A method and system for detecting the durability of an adhesive material interface

Abstract

The application discloses a kind of adhesive material interface durability detection method and system, it is related to adhesive material interface durability detection technical field, comprising: applying preset diagnostic microcirculation load, obtain initial diagnostic response data and determine initial interface response benchmark;Perform segmented cycle durability loading, record each segment cumulative cycle number;After each segment ends, unload recovery, determine recovery termination state according to the interface response of recovery stage;Diagnose again after reaching recovery termination state, determine irreversible interface degradation according to the difference between recovery after diagnostic response and initial interface response benchmark;According to irreversible interface degradation and cumulative cycle number, determine change relationship and interface durability turning point stage;Generate interface durability detection result.The application reduces the interference of viscoelastic recovery and unloading rebound on degradation evaluation, realizes continuous characterization and turning identification of durability degradation history, improves the comparability and stage identification ability of detection result.

Description

Technical Field

[0001] This invention relates to the field of adhesive material interface durability testing technology, specifically to a method and system for testing adhesive material interface durability. Background Technology

[0002] With the expanding applications of structural adhesives, polymer adhesives, and composite adhesive structures in automotive, rail transportation, aerospace, electronic packaging, and building connections, the long-term service reliability of adhesive interfaces has become a crucial aspect of adhesive material performance evaluation. Current interface durability testing typically employs static tensile testing, shear strength testing, cyclic fatigue loading, temperature and humidity aging, or load-environment coupled accelerated testing. Changes in interface performance are evaluated by comparing ultimate strength, stiffness, fracture energy, residual deformation, or fatigue life before and after aging. Some testing methods also involve periodic retesting at different cycle counts to obtain the decay law of mechanical properties with the number of cycles, thus characterizing the durability degradation process of the adhesive interface. In recent years, with the development of high-precision mechanical testing and displacement detection technologies, utilizing load-displacement response, hysteresis dissipation, and local deformation characteristics to perform process-oriented characterization of adhesive interfaces has become an important development direction in durability testing.

[0003] However, existing methods for testing the durability of adhesive interfaces primarily focus on the decrease in ultimate strength, final fatigue life, or changes in mechanical properties at fixed cycle points. They lack effective separation of viscoelastic recovery, unloading springback, and irreversible interface degradation that occur simultaneously after cyclic loading. When retesting after a fixed waiting time, the interface recovery timescales at different durability stages may differ significantly, easily leading to the inclusion of insufficiently recovered transient responses in the degradation evaluation results, resulting in a lack of consistent comparison benchmarks between different cycle points. Furthermore, relying solely on instantaneous stiffness, displacement, or hysteresis changes during loading makes it difficult to determine whether detected response deviations can recover after unloading. On the other hand, existing methods typically evaluate durability performance based on a single mechanical index or the number of final failure cycles, lacking a unified characterization of multidimensional interface responses such as stiffness changes, energy dissipation, and residual displacement, making it difficult to stably describe the process of interface evolution from gradual degradation in the early stages to accelerated degradation in the later stages. Meanwhile, conventional fatigue life determination often uses fracture, strength reduction to a set ratio, or reaching a preset number of cycles as the termination criteria. It lacks a clear identification mechanism for when the rate of interface degradation changes continuously, making it difficult to determine the physically significant durability transition stage before final macroscopic failure. This is not conducive to accurately characterizing the staged degradation characteristics of adhesive interfaces and the durability differences between different material systems. Summary of the Invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the technical problem solved by this invention is that existing methods for testing the interface durability of adhesive materials have the following drawbacks: difficulty in effectively distinguishing between recoverable responses after cyclic loading and irreversible interface degradation; the use of fixed recovery times leads to a lack of consistency in the test status at different durability stages; reliance on single performance indicators or final failure results makes it difficult to characterize the phased changes in the rate of interface degradation; and the problem of how to establish an irreversible interface degradation process based on segmented durability loading, recovery status determination, and repeated diagnostic responses, and identify the interface durability transition stage from stable degradation to continuously accelerating degradation of the adhesive interface.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, embodiments of the present invention provide a method for testing the interface durability of adhesive materials, comprising the following steps: S1: Apply a preset diagnostic micro-cyclic load to the bonding interface of the adhesive material to be tested, obtain initial diagnostic response data, and determine the initial interface response benchmark based on the initial diagnostic response data; S2: Perform segmented cyclic durability loading consisting of multiple durability loading segments on the bonding interface. Record the corresponding cumulative number of cycles at the end of each durability loading segment. After completing steps S3 and S4 corresponding to the current durability loading segment, proceed to the next durability loading segment. S3: After each durability loading segment ends, perform unloading recovery on the bonding interface, obtain the interface response data of the recovery stage, and determine the recovery termination state based on the change of the interface response data of the recovery stage with the recovery time. S4: After reaching the recovery termination state, apply the preset diagnostic micro-circulation load again, obtain the post-recovery diagnostic response data, and determine the irreversible interface degradation amount corresponding to each durability loading segment based on the difference between the post-recovery diagnostic response data and the initial interface response benchmark. S5: Based on the irreversible interface degradation amount and cumulative number of cycles corresponding to each durability loading segment, determine the relationship between the irreversible interface degradation amount and the cumulative number of cycles, and determine the interface durability transition stage based on the relationship. S6: Generate the interface durability test results of the adhesive material to be tested based on the amount of irreversible interface degradation, the change relationship, and the interface durability transition stage corresponding to each durability loading segment.

[0007] As a preferred embodiment of the adhesive material interface durability testing method of the present invention, step S1 specifically includes: Before segmented cyclic durability loading, the preset diagnostic micro-cyclic load is applied to the adhesive interface according to the preset diagnostic load amplitude, preset diagnostic loading frequency, preset diagnostic load waveform and preset diagnostic cycle number. The peak load of the preset diagnostic micro-cyclic load is lower than the predetermined interface damage initiation load. Obtain load data and displacement data under the preset diagnostic micro-circulation load, determine diagnostic stiffness, hysteresis dissipation characteristics and residual displacement characteristics based on the load data and displacement data, and use the diagnostic stiffness, hysteresis dissipation characteristics and residual displacement characteristics as the initial diagnostic response data; The initial diagnostic stiffness characteristic value, the initial hysteresis dissipation characteristic value, and the initial residual displacement characteristic value are determined based on the diagnostic stiffness, the hysteresis dissipation characteristic value, and the initial residual displacement characteristic value, respectively, and the initial interface response benchmark is formed by the initial diagnostic stiffness characteristic value, the initial hysteresis dissipation characteristic value, and the initial residual displacement characteristic value.

[0008] As a preferred embodiment of the adhesive material interface durability testing method of the present invention, step S2 specifically includes: The bonding interface is subjected to cyclic durability loading according to a preset durability load amplitude, a preset durability loading frequency, and a preset durability load waveform, wherein the preset durability load amplitude is greater than the preset diagnostic load amplitude. The cyclic durability loading process is divided into multiple durability loading segments that are executed sequentially. The current durability loading segment ends when the segment termination condition corresponding to each durability loading segment is met. Record the total number of cycles completed from the start of the cyclic durability loading to the end of each durability loading segment, and determine the total number of cycles as the cumulative number of cycles for the corresponding durability loading segment.

[0009] As a preferred embodiment of the adhesive material interface durability testing method of the present invention, step S3 specifically includes: After each durability loading segment is completed, the cyclic durability load applied to the bonding interface is unloaded to a preset recovery load and maintained. The load level corresponding to the preset recovery load is lower than the load peak value of the preset diagnostic micro-cyclic load. According to the preset recovery detection interval, the recovery stage interface response data corresponding to multiple recovery detection times are obtained. The recovery stage interface response data includes recovery displacement data. The recovery response change amount corresponding to each recovery detection interval is determined according to the change between the recovery displacement data corresponding to adjacent recovery detection times. When the change in the recovery response corresponding to a consecutive preset number of recovery detection intervals is not greater than a preset recovery stability threshold, it is determined that the bonding interface has reached the recovery termination state.

[0010] As a preferred embodiment of the adhesive material interface durability testing method of the present invention, step S4 specifically includes: After the bonding interface reaches the recovery termination state, the preset diagnostic micro-circulation load is applied to the bonding interface again according to the preset diagnostic load amplitude, the preset diagnostic loading frequency, the preset diagnostic load waveform, and the preset diagnostic cycle number, and the recovery load data and recovery displacement data are obtained during the operation of the preset diagnostic micro-circulation load. Based on the recovered load data and the recovered displacement data, the recovered diagnostic stiffness, recovered hysteresis dissipation characteristics, and recovered residual displacement characteristics are determined according to the feature extraction method consistent with step S1, and the recovered diagnostic response data is composed of the recovered diagnostic stiffness, the recovered hysteresis dissipation characteristics, and the recovered residual displacement characteristics.

[0011] As a preferred embodiment of the adhesive material interface durability testing method of the present invention, step S4 further includes: The stiffness degradation characterization value is determined based on the difference between the recovered diagnostic stiffness and the initial diagnostic stiffness characteristic value; the dissipation degradation characterization value is determined based on the difference between the recovered hysteretic dissipation characteristic and the initial hysteretic dissipation characteristic value; and the residual displacement degradation characterization value is determined based on the difference between the recovered residual displacement characteristic and the initial residual displacement characteristic value. According to the preset feature scale corresponding to each degradation characterization value, the stiffness degradation characterization value, the dissipation degradation characterization value, and the residual displacement degradation characterization value are subjected to scale unification processing, and according to the preset degradation direction corresponding to each response feature, the direction is unified processing to obtain stiffness degradation characterization value, dissipation degradation characterization value, and residual displacement degradation characterization value. The stiffness degradation characteristic value, the dissipation degradation characteristic value, and the residual displacement degradation characteristic value are weighted and fused according to a preset fusion weight to obtain the irreversible interface degradation amount of the corresponding durability loading segment.

[0012] As a preferred embodiment of the adhesive material interface durability testing method of the present invention, step S5 specifically includes: Obtain the irreversible interface degradation amount and the cumulative number of cycles corresponding to each durability loading segment, and construct a degradation data sequence according to the order of the cumulative number of cycles; The irreversible interface degradation rate between adjacent durability loading segments is determined based on the difference between the irreversible interface degradation amount between adjacent durability loading segments and the difference between the cumulative number of cycles in the degradation data sequence. The relationship between the amount of irreversible interface degradation and the cumulative number of cycles is determined based on the degradation data sequence, and the degree of change of the relationship between adjacent cumulative number of cycles is characterized by the irreversible interface degradation development rate between each adjacent durability loading segment.

[0013] As a preferred embodiment of the adhesive material interface durability testing method of the present invention, step S5 further includes: A stable degradation interval is determined based on the change in the irreversible interface degradation rate between multiple consecutive adjacent durability loading segments. When the change in the first preset number of consecutive segments is not greater than a preset stable change threshold, the corresponding consecutive durability loading interval is determined as the stable degradation interval. A baseline degradation rate is determined based on the irreversible interface degradation rate within the stable degradation interval. According to the order of cumulative cycle count, the irreversible interface degradation rate between each adjacent durability loading segment after the stable degradation interval is compared with the baseline degradation rate, and the corresponding degradation deviation is determined based on the difference between the two. When the degradation deviation of a second consecutive preset number of such deviations is not less than a preset turning point deviation threshold, and the corresponding irreversible interface degradation rate shows a continuous increasing trend, the next durability loading segment corresponding to the first irreversible interface degradation rate among the second consecutive preset number of such irreversible interface degradation rates is determined as the interface durability turning point stage.

[0014] As a preferred embodiment of the adhesive material interface durability testing method of the present invention, step S6 specifically includes: The irreversible degradation process of the adhesive interface is determined based on the amount of irreversible interface degradation corresponding to each durability loading segment and the relationship between the amount of irreversible interface degradation and the cumulative number of cycles. The durability transition cycle number is determined based on the cumulative number of cycles of the durability loading segment corresponding to the interface durability transition stage. The irreversible degradation process corresponding to the durability transition cycle number is determined as the pre-transition degradation process, and the irreversible degradation process corresponding to the durability transition cycle number is determined as the post-transition degradation process. The interface durability test results of the adhesive material to be tested are generated based on the degradation process before the transition, the degradation process after the transition, and the number of durability transition cycles.

[0015] Secondly, embodiments of the present invention provide a system for testing the interface durability of adhesive materials, comprising: Initial interface response benchmark determination module: Apply a preset diagnostic micro-cyclic load to the bonding interface of the adhesive material to be tested, acquire initial diagnostic response data, and determine the initial interface response benchmark based on the initial diagnostic response data; Segmented Cyclic Durability Loading Module: Performs segmented cyclic durability loading on the bonding interface, consisting of multiple durability loading segments. Records the corresponding cumulative number of cycles at the end of each durability loading segment, and enters the next durability loading segment after completing steps S3 and S4 corresponding to the current durability loading segment. Recovery Termination State Determination Module: After each durability loading segment ends, unloading recovery is performed on the bonding interface, the interface response data of the recovery stage is obtained, and the recovery termination state is determined based on the change of the interface response data of the recovery stage with the recovery time. Irreversible interface degradation determination module: After reaching the recovery termination state, the preset diagnostic micro-cycle load is applied again to obtain the post-recovery diagnostic response data, and the irreversible interface degradation corresponding to each durability loading segment is determined based on the difference between the post-recovery diagnostic response data and the initial interface response benchmark. Interface durability transition stage determination module: Based on the irreversible interface degradation amount and cumulative cycle count corresponding to each durability loading segment, determine the relationship between the irreversible interface degradation amount and the cumulative cycle count, and determine the interface durability transition stage based on the relationship. Interface durability test result generation module: Based on the irreversible interface degradation amount, the change relationship, and the interface durability transition stage corresponding to each durability loading segment, the interface durability test result of the adhesive material to be tested is generated.

[0016] The beneficial effects of this invention are as follows: By introducing unloading recovery and same-condition diagnosis between each durability loading segment, this invention allows for interface response comparison at different cumulative cycle nodes after reaching a unified recovery termination state, thereby reducing the interference of viscoelastic recovery and unloading rebound on irreversible degradation evaluation. The difference between the post-recovery diagnostic response and the initial interface response benchmark forms the irreversible interface degradation amount corresponding to each durability node. Combined with the cumulative cycle count to analyze the degradation development rate, this invention can continuously characterize the durability degradation process of the adhesive interface and further identify the interface durability transition stage from relatively stable degradation to continuously accelerating degradation, thereby improving the comparability, stage identification ability, and technical interpretability of adhesive material interface durability test results. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is an overall flowchart of a method for testing the interface durability of adhesive materials according to the first embodiment of the present invention; Figure 2 This is a module connection diagram of an adhesive material interface durability testing system provided in the third embodiment of the present invention. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0019] Example 1, referring to Figure 1 This invention provides a method for testing the interface durability of adhesive materials, as one embodiment of the present invention.

[0020] S1: Apply a preset diagnostic micro-cyclic load to the bonding interface of the adhesive material to be tested, obtain initial diagnostic response data, and determine the initial interface response benchmark based on the initial diagnostic response data.

[0021] Before segmented cyclic durability loading, the preset diagnostic micro-cyclic load is applied to the adhesive interface according to the preset diagnostic load amplitude, preset diagnostic loading frequency, preset diagnostic load waveform and preset diagnostic cycle number. The peak load of the preset diagnostic micro-cyclic load is lower than the predetermined interface damage initiation load. Obtain load data and displacement data under the preset diagnostic micro-circulation load, determine diagnostic stiffness, hysteresis dissipation characteristics and residual displacement characteristics based on the load data and displacement data, and use the diagnostic stiffness, hysteresis dissipation characteristics and residual displacement characteristics as the initial diagnostic response data; The initial diagnostic stiffness characteristic value, the initial hysteresis dissipation characteristic value, and the initial residual displacement characteristic value are determined based on the diagnostic stiffness, the hysteresis dissipation characteristic value, and the initial residual displacement characteristic value, respectively, and the initial interface response benchmark is formed by the initial diagnostic stiffness characteristic value, the initial hysteresis dissipation characteristic value, and the initial residual displacement characteristic value.

[0022] In this embodiment, step S1 is used to obtain the initial mechanical response state of the adhesive material under test before it has undergone cyclic durability testing, using a low-disturbance load that will not cause identifiable additional degradation to the bonding interface, and to establish a self-reference benchmark for comparison under the same conditions after each subsequent durability loading segment has been unloaded and recovered. This step is not used to directly determine whether the adhesive interface has already experienced durability failure, but rather to ensure that the diagnostic response obtained after recovery in step S4 has the same load conditions, displacement measurement method, sampling conditions, and feature extraction rules as the initial diagnostic response established in step S1.

[0023] In this embodiment, a two-component epoxy resin adhesive was used as the adhesive material to be tested, and an aluminum alloy plate was used as the substrate to prepare a single-lap shear test specimen. The bonding length was set to 25 mm, the bonding width to 12.5 mm, and the adhesive layer thickness to 0.20 mm. After the specified curing process was completed, initial diagnosis and subsequent durability testing were performed under environmental conditions of 23 ℃ ± 2 ℃ and 50% ± 5% relative humidity. The above materials, dimensions, and environmental conditions are used to form a set of directly implementable testing conditions and are not intended as fixed conditions that must be adopted for other adhesive material systems.

[0024] The specimen is mounted in a mechanical testing device with cyclic load control, and the loading direction is aligned with the cyclic durability loading direction in subsequent step S2. Load data is continuously acquired by a force sensor; displacement data preferably uses the relative displacement between the measurement reference positions on both sides of the bonded area along the loading direction. Specifically, non-contact displacement measurement marks can be set on both sides of the overlap area, and the positional changes of the two marks can be recorded synchronously using a displacement measurement device. The relative displacement of the two marks along the loading direction is used as the displacement data of the bonded area. Using the relative displacement of the bonded area instead of directly using the crossbeam displacement of the testing machine can reduce the influence of fixture deformation, substrate elastic deformation, and loading system flexibility on subsequent stiffness diagnosis. If the testing device can only output crossbeam displacement, the system flexibility calibration is completed using an empty fixture and a substrate of the same size before formal testing, and the contribution of the corresponding non-bonded area elastic displacement is deducted from the crossbeam displacement.

[0025] Predetermination of the interface damage initiation load.

[0026] The preset diagnostic micro-cyclic load is used to excite the adhesive interface to generate a load-displacement response that can be stably measured, rather than to actively generate new interface degradation. Therefore, before the formal test, the interface damage initiation load is first determined using a reference sample from the same batch that has the same adhesive, substrate, bonding size, adhesive layer thickness and curing conditions as the sample to be tested.

[0027] First, low-load repeated diagnostics were performed. Using a peak load of 0.3 kN, a reference load of 0.1 kN, and a loading frequency of 0.5 Hz, five consecutive low-load loading-unloading cycles were performed on the reference sample. After each loading cycle, the reference load was returned to 0.1 kN and held for 30 s, and the corresponding residual displacement was recorded. The average and standard deviation of the residual displacement from the five repeated low-load tests were calculated, and the sum of the average and three times the standard deviation was used as the threshold for significant deviation of the residual displacement.

[0028] The significant deviation of the residual displacement from the threshold is not an artificially set empirical constant. It is based on normal residual displacement fluctuations generated by repeated low-load measurements under the same sample system, loading equipment, and recovery observation conditions. The method of using the average value plus three standard deviations is to ensure that the threshold is higher than most normal repeated measurement fluctuations and random sensor disturbances, rather than directly interpreting small single residual displacement changes as interface damage. Here, three standard deviations are used to construct the engineering statistical boundary for normal repeated variations, and are not interpreted as strictly probabilistic confidence intervals that must satisfy a specific probability distribution.

[0029] Subsequently, a loading-unloading pre-test with progressively increasing peak values ​​was conducted on the reference specimen. The peak load started at 0.5 kN, increasing by 0.1 kN after each load level. After each load level, the load was unloaded to 0.1 kN and held for 30 s, and the corresponding residual displacement was recorded. When the residual displacement of a certain load level first exceeded the aforementioned residual displacement significantly deviating from the threshold, and the residual displacement obtained in the next load level under the same recovery conditions still exceeded the threshold, the peak value of the load level where the first sustained deviation occurred was determined as the interface damage initiation load. .

[0030] The reason for adopting the "first exceeding the threshold and then confirmed by the next load level" approach is that an abnormal residual displacement in a single load level may originate from clamping micro-slippage, instantaneous sampling disturbance, or local contact adjustment; only when the deviation still exists in the next load level is it used as a reference load for the interface to begin forming an identifiable and unrecoverable response. It is the damage initiation reference load determined under the current loading number, recovery time, and testing conditions, and is not equivalent to the ultimate failure load of the bonded specimen.

[0031] Determination of pre-defined diagnostic microcirculatory load.

[0032] After obtaining the initial load for interface damage, candidate diagnostic loads are validated based on reference specimens from the same batch. The diagnostic load parameters must simultaneously satisfy response identifiability and low perturbation.

[0033] Response identifiability is used to confirm that, under candidate diagnostic load conditions, the force sensor and displacement measurement system can stably acquire the complete loading branch, unloading branch, and reference load return states, and can repeatedly extract the diagnostic stiffness, hysteretic dissipation characteristics, and residual displacement characteristics described later. If the candidate load is too low, causing any of the three characteristics to remain close to the reliable resolution level of the current measurement system for an extended period, the candidate diagnostic peak load is increased.

[0034] Low perturbation is used to confirm that after repeated application of candidate diagnostic microcyclic loads according to a cumulative number of diagnoses not less than the formal testing plan, the three diagnostic features do not exhibit unidirectional changes relative to the initial diagnosis that continuously exceed the normal fluctuation range of repeated diagnoses without durability loading; if such continuous changes occur, the peak load of the candidate diagnosis is reduced and re-verified.

[0035] In this embodiment, the diagnostic peak load is determined according to the above method. 0.40 times, the diagnostic reference load is 0.05 times. When At that time, the diagnostic peak load was 0.8 kN, the diagnostic reference load was 0.1 kN, and the diagnostic load amplitude was half the difference between the peak load and the reference load, i.e., 0.35 kN. The above 0.40 and 0.05 are not empirical constants applicable to all adhesive materials, but specific parameters determined in this embodiment after satisfying the two conditions of identifiable response and low disturbance.

[0036] The preset diagnostic load waveform is a sine wave, the diagnostic loading frequency is 0.5 Hz, the number of diagnostic cycles is 6, and the load and displacement synchronous sampling frequency is 100 Hz. Therefore, each sinusoidal diagnostic cycle can obtain approximately 200 sets of synchronous load-displacement data. To obtain a stable residual displacement reference value, the load is briefly held at the same diagnostic reference load before and after each diagnostic cycle, and the corresponding reference load displacement sampling window is obtained respectively. The brief holding process is only used to obtain reference displacement data and does not change the 0.5 Hz loading frequency of the sinusoidal loading segment.

[0037] After obtaining the diagnostic data, the data is divided into 6 diagnostic microcycles according to the time of cycle start, peak value and return to the diagnostic reference load, and the diagnostic stiffness, hysteresis dissipation characteristics and residual displacement characteristics are determined in parallel from the data of the same diagnostic microcycle.

[0038] First diagnostic feature: Diagnostic stiffness.

[0039] Diagnostic stiffness is used to characterize the ability of the bonded area to resist relative deformation within a preset diagnostic load range. The initial stage of the cycle may include fixture clearance elimination and initial contact adjustment, while slight local nonlinearity may occur near the diagnostic peak region. Therefore, in this embodiment, synchronous sampling points corresponding to the load variation range of 20% to 80% are selected in each diagnostic cycle loading branch for stiffness determination.

[0040] The 20%–80% range is not arbitrarily set. Before formal testing, multiple candidate load ranges containing the cycle initiation region, the region near the peak, and the region after removing the above regions are compared using reference samples from the same batch. The range that can retain enough sampling points, while making the slope obtained from repeated diagnosis less discrete, and is not significantly affected by the initial gap elimination and local nonlinearity near the peak is selected as the formal range. In this embodiment, 20%–80% is used accordingly.

[0041] Compared to directly using the ordinary least squares slope, this embodiment uses the median value of the slope of paired sampling points to determine the diagnostic stiffness, making it less likely that a small number of local displacement jumps or abnormal sampling points will significantly change the final stiffness result. Equation 1: ; in, For the first The diagnostic stiffness corresponding to each diagnostic microcirculation is expressed in N / mm. Numbering is used to diagnose microcirculation; For the first The first diagnostic microcirculation The load corresponding to each valid sampling point; For the same diagnostic microcirculation, the first The load corresponding to each valid sampling point; For the first The relative displacement of the bonding area corresponding to each valid sampling point; For the first The relative displacement of the bonding area corresponding to each valid sampling point; and A valid sample point index that satisfies ; For the first The set of effective synchronous sampling points in the diagnostic micro-circulation loading branch that fall within the aforementioned 20% to 80% load variation range; This indicates that the median value of the slope is taken over all valid two points.

[0042] Since the load and displacement within the same loading branch increase in the same direction overall, under normal testing conditions... The larger the value, the higher the equivalent bearing stiffness of the bonded area within the current diagnostic load range. If the result of a certain diagnostic cycle... If the value is non-positive, it indicates that there may be obvious loading abnormalities, displacement measurement abnormalities, or sample slippage in the cycle. The cycle should not be considered a valid diagnostic cycle, and the corresponding original load-displacement data should be checked instead.

[0043] Second diagnostic feature: Hysteresis dissipation.

[0044] Hysteresis dissipation characteristics are used to characterize the energy dissipation caused by the non-overlapping of loading and unloading branches in the same diagnostic microcycle. Considering that the actual equipment obtains discrete load-displacement sampling data, this embodiment does not introduce an additional continuous energy model, but directly determines it based on the discrete load-displacement closed path of the complete diagnostic cycle, Equation 2: , ; in, For the first Hysteresis dissipation characteristics corresponding to each diagnostic microcirculation, in N·mm; This is an index of synchronous sampling points arranged chronologically within the diagnostic microcirculation. For the first The number of effective synchronous sampling points contained in a diagnostic microcirculation; For the first The load at each sampling point; The load for the next sampling point; For the first Relative displacement of the bonding area at each sampling point; This represents the relative displacement of the bonding area at the next sampling point; For diagnostic reference load; The first synchronous sampling point reconnected to complete the discrete path closure.

[0045] Equation 2 uses the diagnostic reference load as the load reference level, ensuring that even if a small amount of residual displacement exists at the end of the cycle, no additional translational work corresponding to the reference load will be introduced along the closed path of the diagnostic reference load. Therefore, the results primarily characterize the path difference between the diagnostic cyclic loading and unloading branches. Under normal circumstances... A value close to zero indicates that the loading and unloading paths are relatively close, while an increase in the value indicates that the energy dissipation response within the current diagnostic loop is enhanced.

[0046] Third diagnostic feature: residual displacement characteristics.

[0047] Residual displacement characteristics are used to characterize the relative displacement offset that remains after a diagnostic microcycle is completed and returns to the same diagnostic reference load as at the start of the cycle. To avoid the influence of random fluctuations in the sensor on individual sampling points, fixed-length displacement sampling windows are obtained at the beginning and end of each diagnostic microcycle during the short-term holding phase of the diagnostic reference load, and the median value of the relative displacement within the two windows is used to determine the displacement, as shown in Equation 3: ; in, For the first The residual displacement characteristics corresponding to each diagnostic microcirculation are shown in mm. For the first The set of displacement sampling points that were in a stable state under the diagnostic reference load before the start of the diagnostic microcycle; For the first The set of displacement sampling points after the end of each diagnostic microcycle and return to the same diagnostic reference load; This represents the relative displacement of the bonding area at the corresponding sampling point; The index of the displacement sampling point; This indicates that the median value is taken from all relative displacement data within the corresponding sampling window.

[0048] The start and end sampling windows have the same duration and are fixed before the formal testing begins. In this embodiment, a 0.20 s sampling window is used under 100 Hz displacement sampling conditions, with each window containing approximately 20 relative displacement data points. The rationale for using 0.20 s is that this time window provides sufficient repeated sampling points to reduce single-point noise, while being short enough relative to the 2 s dynamic loading time of a 0.5 Hz diagnostic loading cycle to not significantly prolong a single diagnostic process. If the sampling frequency or displacement measurement device is changed, a sampling window that balances data stability and diagnostic time resolution should be re-evaluated, rather than directly using 0.20 s.

[0049] Under normal circumstances . A value close to zero indicates that the adhesion area has basically returned to its displacement state at the beginning of the circulation after the diagnosis of microcirculation has ended. An increase indicates an increase in the displacement offset retained after returning to the same diagnostic reference load. It should be noted that the single diagnostic microcycle... This does not directly indicate that irreversible durability damage has occurred at the bonding interface. Step S1 only considers it as one of the initial response features. The true irreversible interface degradation needs to be determined by step S4 after unloading and recovery is completed in subsequent step S3. The post-recovery diagnostic results are compared with the initial baseline of step S1 in the same type.

[0050] Establishing the initial interface response baseline.

[0051] In this embodiment, the preset number of diagnostic cycles is 6. The first diagnostic micro-cycle is used to pre-stabilize the sample clamping state, the contact state of the loading mechanism, and the initial stress state, and does not participate in the initial diagnostic feature statistics; the second to sixth diagnostic micro-cycles are considered as 5 effective diagnostic cycles.

[0052] For the five valid diagnostic cycles, the corresponding diagnostic stiffness, hysteresis dissipation characteristics, and residual displacement characteristics are obtained according to Equations 1, 2, and 3, respectively, and the arithmetic mean of the five valid diagnostic results is taken. Since the arithmetic mean is a data statistical processing method that can be directly performed in this field, this embodiment does not set a separate formula for the average value.

[0053] The average diagnostic stiffness over five effective cycles was used as the initial diagnostic stiffness characteristic value. The average value of the hysteresis dissipation characteristics of the five effective cycles is determined as the initial hysteresis dissipation characteristic value. The average residual displacement characteristic value of 5 effective cycles is determined as the initial residual displacement characteristic value. .

[0054] Depend on , and Together, they constitute the initial interface response benchmark of the bonding interface of the adhesive materials to be tested.

[0055] The term "composition" here refers to the storage of three types of characteristic values ​​with different physical meanings and dimensions as corresponding reference data, which are not processed in step S1. , and Direct summation or fusion can be performed. Diagnostic stiffness reflects the bearing slope of the bonded area within the low-disturbance diagnostic load range; hysteretic dissipation characteristics reflect the energy dissipation state during diagnostic cyclic loading and unloading; and residual displacement characteristics reflect the displacement offset that remains after returning to the same diagnostic reference load. Establishing an initial reference in parallel with these three types of characteristics avoids overlooking interface state changes that are mainly manifested as dissipation changes or residual displacement accumulation when using only a single stiffness index.

[0056] It should also be noted that the step S1 determines , and This will serve as a fixed initial reference for the subsequent step S4. After each durability loading segment ends and is confirmed by step S3 to have reached the recovery termination state, step S4 re-obtains the post-recovery diagnostic stiffness, post-recovery hysteresis dissipation characteristics, and post-recovery residual displacement characteristics using the exact same diagnostic load parameters, cycle division method, sampling conditions, and feature extraction methods as in this step, according to Equations 1 to 3. Thus, a strict longitudinal comparison relationship is established between steps S1 and S4 under the same conditions, providing a unified data foundation for subsequently determining the irreversible interface degradation amount corresponding to each durability loading segment.

[0057] S2: Perform segmented cyclic durability loading consisting of multiple durability loading segments on the bonding interface. Record the corresponding cumulative number of cycles at the end of each durability loading segment, and proceed to the next durability loading segment after completing steps S3 and S4 corresponding to the current durability loading segment.

[0058] The bonding interface is subjected to cyclic durability loading according to a preset durability load amplitude, a preset durability loading frequency, and a preset durability load waveform, wherein the preset durability load amplitude is greater than the preset diagnostic load amplitude. The cyclic durability loading process is divided into multiple durability loading segments that are executed sequentially. The current durability loading segment ends when the segment termination condition corresponding to each durability loading segment is met. Record the total number of cycles completed from the start of the cyclic durability loading to the end of each durability loading segment, and determine the total number of cycles as the cumulative number of cycles for the corresponding durability loading segment.

[0059] In this embodiment, step S2 is used to continuously apply a cyclic load capable of forming a cumulative durability effect to the same bonded sample after establishing the initial interface response benchmark in step S1. Multiple interface state observation nodes with a clearly defined cumulative number of cycles are established during the continuous durability process through segmented pauses. After each durability loading segment ends, the durability load is paused, and the unloading recovery in step S3 and the post-recovery diagnosis in step S4 are executed sequentially. Only after steps S3 and S4 corresponding to the current durability loading segment are completed are the cyclic durability load reapplied and the next durability loading segment begins. This forms a repetitive testing process of "durability loading—unloading recovery—diagnosis retesting—continued durability loading".

[0060] The cyclic durability load in step S2 and the preset diagnostic micro-cyclic load in step S1 serve different technical purposes. The diagnostic micro-cyclic load in step S1 is used to obtain the interface state under low-disturbance conditions. Its main requirement is that the response is identifiable and that it does not actively form identifiable additional degradation due to repeated diagnosis. The cyclic durability load in step S2 is used to continuously apply repetitive mechanical action to the adhesive interface, so that local stress concentration, micro-slip, viscoelastic dissipation changes, and progressive interface damage can accumulate with the number of cycles. Therefore, the preset durability load amplitude used in step S2 is greater than the preset diagnostic load amplitude used in step S1 to ensure that the two types of loads perform different functions of condition diagnosis and durability testing, respectively.

[0061] In this embodiment, cyclic durability loading is performed in the same loading direction as in step S1. Throughout the entire cycle from step S2 to step S4, the sample clamping position, loading direction, and measurement reference of the adhesive area remain unchanged. This ensures that the initial interface response reference established in step S1 and the recovered diagnostic response obtained in subsequent step S4 originate from the same adhesive interface. The cyclic durability load includes at least a peak durability load, a durability reference load, a preset durability load amplitude, a preset durability loading frequency, and a preset durability load waveform. The preset durability load amplitude is determined by half the difference between the peak durability load and the durability reference load, and uses the same load amplitude definition as in step S1.

[0062] Durability load parameters are pre-verified using reference samples from the same batch before the formal testing of the test specimens begins, and are not temporarily adjusted based on the obtained degradation results during the formal testing process. Candidate durability loads should simultaneously meet two conditions: accumulative durability effects and controllable loading process. Accumulative durability effects mean that after multiple consecutive durability loading segments, the post-recovery diagnostic response obtained according to steps S3 and S4 exhibits a sustained change exceeding the normal fluctuation level of repeated diagnostics without durability loading. If the candidate durability load is too low, making it difficult to distinguish the post-recovery response changes of multiple adjacent durability nodes from repeated diagnostic fluctuations over a long period, the candidate durability load level should be increased. Controllable loading process means that the candidate durability load should not cause significant interface separation, continuous instability, or inability to stably maintain the preset peak load in the early stages of durability loading for the reference samples from the same batch. If any of these situations occur, the candidate durability load level should be reduced. Using this dual verification ensures that the durability load can both drive gradual interface degradation and retain sufficient inter-stage observation intervals for subsequent step S5 to identify changes in the degradation rate.

[0063] As a specific setting in this embodiment, the interface damage initiation load predetermined in step S1 is 2.0 kN, the diagnostic peak load is 0.8 kN, the diagnostic reference load is 0.1 kN, and the preset diagnostic load amplitude is 0.35 kN. Under the above conditions, the peak load of the cyclic durability load is set to 1.2 kN, the reference load is set to 0.1 kN, and the corresponding preset durability load amplitude is 0.55 kN, which is greater than the preset diagnostic load amplitude in step S1. The durability peak load of 1.2 kN is also lower than the interface damage initiation load of 2.0 kN predetermined in this embodiment. The purpose is not to require that the durability loading absolutely does not produce irreversible changes, but to avoid rapid macroscopic damage caused by a single or a small number of cycles, so that the durability degradation of the adhesive interface is mainly manifested as a gradual accumulation of state changes under a large number of cycles, thereby preserving the evolution range that can be used for segmented observation and durability transition identification. The above values ​​are specific parameters obtained by this embodiment through verification with the same batch of reference samples, and are not fixed values ​​that must be adopted for other adhesive material systems.

[0064] In this embodiment, the preset durability load waveform is set to a sine wave, and the preset durability loading frequency is set to 1 Hz. A complete durability loading cycle starts with the load from the durability reference load, continuously increases to the durability peak load, and then continuously decreases and returns to the same durability reference load as the cycle boundary. The force sensor continuously records the actual durability load and synchronously acquires it with the displacement measurement data using a unified time reference to verify whether the load peak, reference load, loading frequency, and waveform are executed according to the preset conditions. The load-displacement data of the durability loading stage obtained in step S2 is mainly used to confirm the durability load execution status and identify equipment interruption, sample slippage, or abnormal instability. It does not directly replace the post-recovery diagnostic response obtained in step S4 under the same conditions as in step S1 after the recovery from the termination state.

[0065] After the durability load parameters are determined, the continuous cyclic durability loading process is divided into multiple sequentially executed durability loading segments, and a segment termination condition is set for each durability loading segment. This embodiment uses a fixed number of cycles within a segment as the segment termination condition; that is, each durability loading segment ends after completing 1000 complete durability cycles. The entire detection process is set to 20 durability loading segments, corresponding to a planned total of 20,000 durability cycles. After the first durability loading segment completes 1000 durability cycles, loading is paused, and steps S3 and S4 are executed. After the recovery and diagnosis of this node are completed, the second durability loading segment begins, and subsequent durability loading segments are executed sequentially in the same manner.

[0066] The 1000-cycle interval is not an arbitrarily determined empirical threshold, but rather determined by comparing multiple candidate segment scales through reference durability tests of the same batch before formal testing. The segment scale needs to simultaneously meet two requirements: distinguishable degradation increment and resolving transition points. Distinguishing degradation increment means that the interface response differences obtained by adjacent durability nodes through steps S3 and S4 should be stably distinguishable from normal fluctuations generated by repeated diagnostics without durability loading in repeated reference tests. If the number of cycles for candidate segments is too small, causing changes in adjacent nodes to fall within the normal repeated fluctuation range for a long period, the number of cycles per segment should be increased. Resolving transition points means that a single durability loading segment should not cover an excessively large cycle interval to avoid the continuous degradation rate increase process already observed in the reference durability test being concentrated in the same loading segment, causing subsequent step S5 to only determine a wider transition cycle range. If the number of cycles for candidate segments is too large and the above situation occurs, the number of cycles per segment should be reduced. In this embodiment, 1000 cycles are used as the formal interval cycle number after comparing candidate segment scales, forming 20 state observation nodes within the 20,000-cycle planned durability interval.

[0067] The 20 durability loading segments mentioned above also fall within the specific testing range of this embodiment. This is based on the fact that the pre-conducted reference durability test can cover the main evolutionary range from early gradual degradation, stable degradation to continuous accelerated degradation, and finally to significant instability. It also provides a sufficient number of consecutive nodes for step S5 to establish an early stable degradation benchmark and determine the subsequent continuous acceleration trend. For other adhesive materials, substrates, bonded structures, or durability load levels, the planned number of loading segments should be re-determined based on the coverage of the reference durability curve, rather than directly and mechanically using the 20 loading segments.

[0068] Each durability loading segment employs independent intra-segment cycle counting and cumulative cycle counting. Only when the load completes the entire process from the durability reference load, to the durability peak load, and back to the durability reference load is it counted as a durability cycle. If the load is interrupted within an incomplete cycle due to equipment pause, protection shutdown, or other abnormal reasons, that incomplete process is not counted in the durability cycle count. After the current durability loading segment reaches the preset intra-segment cycle count, the actual number of cycles completed for that segment and the total number of cycles actually completed from the first durability loading segment to the end of the current durability loading segment are recorded. The latter is determined as the cumulative cycle count corresponding to the current durability loading segment.

[0069] Under the fixed 1000-cycle segmentation condition in this embodiment, the cumulative cycle count at the end of the first to twentieth durability loading segments is 1000, 2000, 3000, up to 20000, respectively. The cumulative cycle count here only includes the durability loading cycles actually completed in step S2, excluding the unloading recovery process in step S3 and the diagnostic micro-cycles reapplied in step S4. For example, after the first durability loading segment completes 1000 cycles, even if multiple diagnostic micro-cycles are executed in subsequent step S4, the cumulative cycle count of this durability state node remains at 1000; only after re-entering step S2 and completing a new durability cycle does the cumulative cycle count continue to increase.

[0070] In cases where the actual number of cycles completed in a durability loading segment differs from the preset number of cycles due to equipment downtime, abnormal handling, or premature termination of the sample, the cumulative number of cycles is not manually corrected at equal intervals; instead, the actual number of durability cycles completed is recorded. This ensures that the cumulative number of cycles used in subsequent step S5 always corresponds to the actual durability load experienced by the bonded interface, and allows for the determination of the irreversible interface degradation rate based on the difference in the actual number of cycles even when the intervals between adjacent durability nodes are not entirely identical.

[0071] After each durability loading segment ends and the cumulative number of cycles is recorded, the next durability loading segment is not immediately initiated. First, the cyclic durability load is stopped, and in step S3, the bonded interface is unloaded to a preset recovery load. The interface response during the recovery phase is continuously acquired until the recovery termination state is determined. Subsequently, step S4 performs post-recovery diagnosis using the same diagnostic load parameters, sampling conditions, and feature extraction methods as step S1, obtaining the irreversible interface degradation amount corresponding to the current durability loading segment. Only after steps S3 and S4 of the current durability loading segment are completed is the cyclic durability load reapplied, and the next durability loading segment begins. Therefore, each cumulative number of cycles corresponds only to the post-recovery interface state obtained after the end of the same loading segment, preventing subsequent durability cycles from interfering with the current node's state evaluation.

[0072] By employing the segmentation method described above, continuous durability loading can be transformed into multiple discrete and locatable interface state observation nodes. If only a single detection is performed after continuous loading to the final macroscopic failure, only the overall difference between the initial and final states can be obtained; the staged evolution of interface degradation with the cumulative number of cycles cannot be obtained, nor can the degradation development rate between adjacent durability nodes be provided for step S5. By actively pausing durability loading at preset cycle nodes and inserting the unified recovery step S3 and the same-condition diagnosis step S4 at each node, a one-to-one correspondence data sequence of "cumulative cycle count - irreversible interface degradation amount" can be formed, where the cumulative cycle count is determined by step S2, and the irreversible interface degradation amount is determined by step S4.

[0073] It should also be noted that the preset durability load amplitude, preset durability load frequency, and preset durability load waveform remain unchanged within each durability loading segment of the same test specimen. Once the formal testing begins, the subsequent durability loading parameters will not be temporarily changed due to the obtained interface degradation results. The reason for using fixed durability conditions is that if the load amplitude, frequency, or waveform changes simultaneously in different loading segments, the subsequent diagnostic response changes may originate from both changes in material state and changes in external durability conditions, which is not conducive to analyzing the degradation development pattern based on the cumulative number of cycles. The current test will only be stopped when equipment safety protection occurs, the specimen cannot maintain the specified load, or other pre-defined abnormal termination conditions occur, and the cause of the abnormality and the actual cumulative number of cycles will be recorded.

[0074] Therefore, the main output of step S2 is the sequence of durability loading segments arranged in the order of durability loading, the actual number of loops completed within each durability loading segment, and the cumulative number of loops at the end of each durability loading segment. Step S2 itself does not directly determine the degree of irreversible interface degradation, nor does it directly determine the interface durability transition stage. Instead, it provides clear durability action nodes to steps S3 and S4, and provides cumulative loop count coordinates to step S5. After multiple durability loading segments are completed sequentially, each cumulative loop count node establishes a one-to-one correspondence with the corresponding irreversible interface degradation amount obtained in step S4, providing a data foundation for subsequently determining the relationship between the irreversible interface degradation amount and the cumulative loop count, and for identifying the interface durability transition stage.

[0075] S3: After each durability loading segment ends, perform unloading recovery on the bonding interface, obtain the interface response data of the recovery stage, and determine the recovery termination state based on the change of the interface response data of the recovery stage with the recovery time.

[0076] After each durability loading segment is completed, the cyclic durability load applied to the bonding interface is unloaded to a preset recovery load and maintained. The load level corresponding to the preset recovery load is lower than the load peak value of the preset diagnostic micro-cyclic load. According to the preset recovery detection interval, the recovery stage interface response data corresponding to multiple recovery detection times are obtained. The recovery stage interface response data includes recovery displacement data. The recovery response change amount corresponding to each recovery detection interval is determined according to the change between the recovery displacement data corresponding to adjacent recovery detection times. When the change in the recovery response corresponding to a consecutive preset number of recovery detection intervals is not greater than a preset recovery stability threshold, it is determined that the bonding interface has reached the recovery termination state.

[0077] In this embodiment, step S3 is used to transition the bonded interface that has undergone cyclic durability testing from the durability loading state to the recovery termination state, which is ready for retesting under the same conditions in step S4, after each durability loading segment. Step S3 does not directly evaluate whether the current bonded interface has formed irreversible durability degradation. Instead, it determines when the recoverable response, which still changes over time after the durability load stops, enters a stable fluctuation range through controlled unloading and continuous recovery displacement monitoring. This provides a unified and repeatable diagnostic entry condition for step S4. By setting this recovery process between the durability testing in step S2 and the post-recovery diagnosis in step S4, the interference of time-dependent responses such as viscoelastic delayed recovery, unloading rebound, local contact readjustment, and interface stress redistribution of adhesive materials on the subsequent evaluation of irreversible interface degradation can be reduced.

[0078] Specifically, in the first Each durability loading segment reaches the segment termination condition specified in step S2 and the corresponding cumulative number of cycles is recorded. Then, stop applying the cyclic durability load and smoothly unload the load acting on the adhesive interface to the preset recovery load. The preset recovery load is a low load level that remains unchanged during the recovery phase, rather than the cyclic durability load amplitude. The purpose of maintaining a certain recovery load is to maintain stable force contact between the specimen, fixture, and loading mechanism while ceasing to apply durability cycles, thus avoiding complete unloading that could cause specimen repositioning, re-establishment of fixture clearance, or abrupt changes in the displacement measurement reference.

[0079] In this embodiment, a preset recovery load is preferably used. The diagnostic reference load in step S1 is the same load level. According to the specific implementation parameters described in step S1, the diagnostic reference load is 0.1 kN, and the diagnostic peak load is 0.8 kN. Therefore, in this embodiment, the preset recovery load is set to 0.1 kN. This setting allows the system to directly proceed to step S4 from the same diagnostic reference load state as step S1 after step S3 reaches the recovery termination state, without requiring a significant load reference conversion after recovery termination, thereby reducing instantaneous displacement changes caused by additional load adjustments. It should be noted that 0.1 kN is the specific recovery load in this embodiment and does not constitute a fixed limitation on other adhesive material systems; for other materials or sample structures, the preset recovery load should be lower than the peak load of the corresponding preset diagnostic micro-cycle load and be able to maintain stable stress contact without forming new durability cycles.

[0080] After the load is unloaded to the preset recovery load, the loading device switches to a constant load holding state and uses the force sensor output for closed-loop control. In this embodiment, the allowable holding error of the recovery load is controlled within ±2% of the preset recovery load. This ±2% is not used as a recovery stability threshold to determine whether the bonding interface has reached the recovery termination state, but only as a device control condition for the validity of the recovery detection interval. This allowable error is determined before formal testing based on the constant load control accuracy of the loading device and repeated holding tests under the same load level. The setting principle is: the allowable range should cover the normal closed-loop control fluctuations of the device under stable constant load operation, and should not be so wide that the load change itself can cause identifiable additional displacement changes. In this embodiment, the loading device can stably maintain the recovery boundary conditions under a ±2% control range under a 0.1 kN constant load state; therefore, this range is adopted. If the actual load temporarily exceeds the allowable range, the corresponding time period is not considered a valid detection interval for recovery stability determination. A new valid recovery detection interval is formed after the load re-enters the allowable range and stabilizes.

[0081] During the recovery phase, no periodic mechanical excitation is applied; only the relative displacement of the bonded area is continuously monitored under a preset recovery load. The recovery displacement is obtained from the same measurement reference positions set in step S1 on both sides of the bonded area, ensuring that steps S1, S3, and S4 use the same displacement measurement object. Once the load reaches the preset recovery load and enters the allowable constant load range, this moment is determined as the recovery timing start point for the current durability loading segment. Step S2 records the cumulative number of cycles. It remains unchanged throughout the recovery process, and the time spent in the recovery phase is not counted in the durability cycle count.

[0082] The preset recovery detection interval and the displacement statistical time window corresponding to a single recovery detection moment are both predetermined using the recovery curves of reference samples from the same batch before the formal testing of the sample to be tested begins. Specifically, multiple complete reference recovery curves are acquired under the same recovery load, the same displacement sampling frequency, and the same environmental conditions. The recovery displacement sequence and recovery termination result are calculated back for multiple candidate recovery detection intervals and candidate displacement statistical time windows. The candidate parameters need to meet two conditions: first, the recovery termination time should be similar and consistent in position in the repeated reference recovery curves; second, the threshold crossing should not frequently occur due to noise at a single sampling point or short-term local displacement fluctuations, resulting in a failure to meet the recovery stability condition after being met. After meeting the above conditions, a shorter recovery detection interval is preferred to maintain the time resolution capability for changes in the recovery process, and the displacement statistical time window is made significantly shorter than the recovery detection interval to avoid excessive overlap of data windows at adjacent detection moments.

[0083] In this embodiment, following the aforementioned reference recovery verification, the preset recovery detection interval is set to 10 s, and the arithmetic mean of the relative displacements of the bonded area continuously collected within 1 s before each recovery detection moment is used as the recovery displacement at that detection moment. The reason for using a 1 s data window is that, under the 100 Hz displacement sampling condition in this embodiment, approximately 100 consecutive displacement sampling values ​​can be obtained, which can reduce the impact of single-point measurement noise on the recovery displacement; at the same time, 1 s is significantly shorter than the 10 s recovery detection interval, preventing a large overlap of the statistical windows of adjacent recovery detection moments. If the displacement sampling frequency, measurement equipment, or material recovery time scale is changed, the recovery detection interval and displacement statistical time window should be re-determined according to the aforementioned candidate parameter verification, instead of directly using 10 s and 1 s.

[0084] The first The recovery detection moments during the recovery process of each durability loading segment are numbered sequentially according to time, and the corresponding recovery displacements are recorded as follows: A recovery detection interval is formed between two adjacent recovery detection times. This step focuses on whether there is still a identifiable change in the recovery displacement between adjacent detection times, without considering the positive or negative direction of the change. Therefore, the change in the recovery response is evaluated using the absolute magnitude of the difference between adjacent recovery displacements. This adjacent difference is no longer formulated separately but is directly used as the basic comparison quantity in the recovery termination formula described later, in order to reduce the number of unnecessary formulas.

[0085] Preset recovery stability threshold Instead of being a fixed empirical value assigned by humans, it is determined through recovery tests under the same conditions on the same batch of reference samples before the formal segmented durability testing begins. First, a complete reference recovery curve is obtained under a preset recovery load, and multiple candidate reference calibration starting points are selected sequentially, starting from the earliest recovery stage. For each candidate starting point, a continuous recovery displacement sequence is formed using the same 10-second recovery detection interval and 1-second displacement statistical time window as in formal step S3, and the change in adjacent recovery displacements within the candidate calibration window is statistically analyzed. When, after gradually moving the candidate calibration starting point backward, the stability threshold obtained from subsequent candidate windows no longer changes the final recovery termination judgment conclusion of the repeated reference recovery curve, the earliest candidate starting point that meets this condition is taken as the starting point of the formal reference calibration time window. This process ensures that the calibration window is determined by the actual recovery curve of the current adhesive system, rather than assuming that all materials will necessarily stabilize after a certain fixed waiting time.

[0086] In this embodiment, after verification as described above, 600 seconds after the restored load enters the allowable constant load range is defined as the starting point of the reference calibration time window. From this moment, at least 21 restoration detection times are continuously acquired, thus forming at least 20 adjacent restoration detection intervals. The arithmetic mean and standard deviation of the adjacent restoration displacement changes in these reference detection intervals are calculated, and the sum of the mean and three times the standard deviation is determined as the preset restoration stability threshold. The basis for using "mean plus three standard deviations" is that the recovery stability threshold needs to be higher than most normal fluctuations formed by measurement noise, small fluctuations of constant load, and slow residual changes after the interface has entered the stable recovery stage under the same conditions, and recovery should not be triggered by a single small change. Here, three standard deviations are used to establish the upper bound of normal stable fluctuations in the engineering statistical sense, and are not interpreted as a strict confidence interval that must obey a specific probability distribution.

[0087] In this embodiment, the average value of the change in adjacent recovered displacements within the stable calibration window, as referenced in the recovery calibration data, is 0.0010 mm, and the standard deviation is 0.0008 mm. Therefore, a preset recovery stability threshold is determined. The value is 0.0034 mm. This 0.0034 mm only corresponds to the specific calibration results under the conditions of adhesive material, sample structure, recovery load, measuring equipment, sampling conditions, and recovery detection interval in this embodiment. If any of the above conditions are changed and the distribution of the reference recovery displacement changes significantly, the reference recovery calibration will be re-performed instead of directly using 0.0034 mm.

[0088] In addition to the recovery stabilization threshold, the number of recovery detection intervals continuously used for recovery termination determination. Similarly, the recovery curve is determined through repeated reference curves before formal testing. Specifically, after the recovery testing interval and the preset recovery stability threshold are fixed, the complete reference recovery curve is calculated sequentially starting from a smaller number of consecutive candidate samples. If a certain number of consecutive candidate samples initially meets the recovery stability requirement, but then the change in the recovery response exceeds the preset recovery stability threshold again in a subsequent testing interval with the same number of samples, it is considered that this number of candidate samples is susceptible to short-term stability or local fluctuations, leading to premature termination. The number of consecutive candidate samples is then increased for reassessment. The smallest number of consecutive candidate samples that can exclude premature termination from the repeated reference recovery curves without unnecessarily extending the recovery waiting time is selected as the formal recovery curve. This embodiment was verified and determined according to the above method. .

[0089] After the above parameters are determined, the first The recovery termination time of each durability loading segment According to the most recent consecutive The determination is made based on whether all effective recovery detection intervals satisfy the condition that the change in recovery response is no greater than the preset recovery stability threshold. Specifically, it is shown in Equation 4: ; in, For the first The recovery termination time after the end of each durability loading segment; Numbering of the durability loading section; For the first The recovery time corresponding to each recovery detection moment; To restore the detection time index; The number of consecutive recovery and stability determinations; This refers to the index variable within the most recent consecutive recovery detection interval; For the first During the recovery process of the first durability loading segment The recovery displacement corresponding to each recovery detection moment; It is the recovery displacement corresponding to the previous recovery detection time; The preset recovery stability threshold is used; Indicates taking the nearest consecutive The maximum value of adjacent recovery displacement changes in each recovery detection interval; This indicates that the testing time that first meets the continuous stability requirement is selected according to the order of recovery time.

[0090] when Furthermore, when the recovery detection interval is 10 s, Equation 4 requires that the adjacent recovery displacement changes corresponding to the five most recently formed valid recovery detection intervals are all no greater than 0.0034 mm, meaning that the recovery changes over the most recent approximately 50 s are always within the reference stable fluctuation range. If the adjacent displacement change of any valid recovery detection interval exceeds the preset recovery stability threshold, the current continuous judgment sequence is interrupted, and judgment begins from the subsequently formed consecutive qualified recovery detection intervals. By taking the maximum value of the change within the continuous interval, a unified criterion can be used to constrain all the most recently recovered intervals simultaneously, rather than making a recovery termination judgment based solely on the small local changes at the last detection moment.

[0091] When Equation 4 is effective for the first time When the time is reached, the bonding interface state corresponding to that moment is determined as the recovery termination state of the current durability loading segment, and the time from the recovery timing start point to the end of the recovery period is recorded. The actual recovery time. The "recovery termination state" referred to here is an operational state defined by this detection method under the conditions of specified recovery load, displacement measurement method, recovery detection interval, recovery stability threshold and number of continuous judgments. It means that the currently observable recovery displacement change has continuously entered the reference stable fluctuation range, and does not mean that it proves from an infinite time scale or the material microstructure level that all viscoelastic relaxation processes have absolutely ended.

[0092] This embodiment also sets a maximum recovery detection time as an abnormal protection condition, but the maximum recovery detection time is not involved in the normal recovery termination judgment of Equation 4. The maximum recovery detection time is determined before formal testing based on the time required for the complete recovery curve of the same batch of reference samples to reach a stable state, the ability of the loading equipment to continuously and stably maintain the recovery load, and the testing efficiency, and should be significantly longer than the time range required for the normal reference recovery curve to reach a stable state. In this embodiment, after reference recovery test and constant load holding capability verification, the maximum recovery detection time is set to 1800 s. If the recovery process reaches 1800 s and still does not meet Equation 4, the current durability loading segment is recorded as "recovery termination condition not met", the process is paused and proceeds to step S4, and the constant load control, displacement measurement, sample clamping status, and whether the bonding interface has experienced continuous slippage or abnormal damage are checked; the current state should not be forcibly judged as the recovery termination state simply because 1800 s has been reached.

[0093] Step S3 uses dynamic recovery termination judgment instead of a uniform fixed waiting time. This is because, as the cumulative durability cycle count increases, the viscoelastic state of the adhesive layer, the degree of local interface slippage, and the stress redistribution process may all change. The recoverable response amplitude and recovery timescale after different durability loading segments do not need to be consistent. If all durability nodes use the same fixed waiting time, early nodes may have already entered a stable fluctuation range but are still unnecessarily delayed, while later nodes may enter step S4 prematurely before significant recovery changes are observed. By using the same recovery load, recovery stability threshold, and continuous interval criterion, while allowing the actual recovery time to be automatically determined based on the real-time recovery displacement changes of the current node, step S4 for nodes with different cumulative cycle counts can all start from a unified state of "the recovery response has entered a stable fluctuation range."

[0094] It should also be noted that the interface response data obtained in step S3 during the recovery phase and the post-recovery diagnostic response data in step S4 have clearly defined data usage boundaries. The continuous recovery displacement and load retention records in step S3 are only used to determine whether the recovery termination state has been reached and to confirm whether the recovery boundary conditions are effective, and are not directly used to calculate the irreversible interface degradation. Step S4, after determining the recovery termination state using Equation 4, reapplies the same preset diagnostic micro-cyclic load as in step S1, and re-determines the post-recovery diagnostic stiffness, post-recovery hysteresis dissipation characteristics, and post-recovery residual displacement characteristics according to Equations 1 to 3 of step S1. This separates the "recovery process monitoring" from the "post-recovery state diagnosis," avoiding the direct use of the recovery displacement, which is still in the process of time change, as an indicator of irreversible degradation.

[0095] For the In the durability loading segment, step S3 finally calculates the cumulative number of loops recorded in step S2. Establish a correspondence with the recovery termination state determined according to Equation 4. During the entire S3 process, the durability cycle count is not increased further; therefore, regardless of the actual recovery time of the current node, the cumulative cycle count remains constant. All remain unchanged. After reaching the recovery termination state, step S4 performs post-recovery diagnosis at the fixed cumulative loop node and further forms a relationship with... The corresponding amount of irreversible interface degradation.

[0096] Therefore, the main outputs of step S3 include the recovery termination status of the current durability loading segment and the recovery termination time. And the effective recovery displacement sequence and recovery load record used to verify the state. Step S3 transforms the traditional fixed waiting time retesting into a dynamic state determination where the recovery response of the bonding interface under test determines the diagnostic entry time by means of "fixed recovery boundary conditions - continuous acquisition of recovery response - reference data calibration of stability threshold - continuous interval confirmation of recovery termination", thereby providing a consistent recovery state premise for step S4 to perform the same condition comparison under different cumulative cycle nodes.

[0097] S4: After reaching the recovery termination state, apply the preset diagnostic micro-circulation load again, obtain the post-recovery diagnostic response data, and determine the irreversible interface degradation amount corresponding to each durability loading segment based on the difference between the post-recovery diagnostic response data and the initial interface response benchmark.

[0098] After the bonding interface reaches the recovery termination state, the preset diagnostic micro-circulation load is applied to the bonding interface again according to the preset diagnostic load amplitude, the preset diagnostic loading frequency, the preset diagnostic load waveform, and the preset diagnostic cycle number, and the recovery load data and recovery displacement data are obtained during the operation of the preset diagnostic micro-circulation load. Based on the recovered load data and the recovered displacement data, the recovered diagnostic stiffness, recovered hysteresis dissipation characteristics, and recovered residual displacement characteristics are determined according to the feature extraction method consistent with step S1, and the recovered diagnostic response data is composed of the recovered diagnostic stiffness, the recovered hysteresis dissipation characteristics, and the recovered residual displacement characteristics.

[0099] The stiffness degradation characterization value is determined based on the difference between the recovered diagnostic stiffness and the initial diagnostic stiffness characteristic value; the dissipation degradation characterization value is determined based on the difference between the recovered hysteretic dissipation characteristic and the initial hysteretic dissipation characteristic value; and the residual displacement degradation characterization value is determined based on the difference between the recovered residual displacement characteristic and the initial residual displacement characteristic value. According to the preset feature scale corresponding to each degradation characterization value, the stiffness degradation characterization value, the dissipation degradation characterization value, and the residual displacement degradation characterization value are subjected to scale unification processing, and according to the preset degradation direction corresponding to each response feature, the direction is unified processing to obtain stiffness degradation characterization value, dissipation degradation characterization value, and residual displacement degradation characterization value. The stiffness degradation characteristic value, the dissipation degradation characteristic value, and the residual displacement degradation characteristic value are weighted and fused according to a preset fusion weight to obtain the irreversible interface degradation amount of the corresponding durability loading segment.

[0100] In this embodiment, step S4 is used to reacquire the mechanical response of the adhesive interface under the same diagnostic conditions as in step S1 after confirming in step S3 that the adhesive interface has reached the recovery termination state. Using the initial interface response benchmark established in step S1 as a fixed self-reference, the response deviation that remains after endurance cycling and completion of the specified recovery is converted into an irreversible interface degradation amount that can be used for longitudinal comparison at different cumulative cycle nodes. Step S4 includes two consecutive processing parts: "acquiring the diagnostic response after recovery" and "determining the amount of irreversible interface degradation." The first part ensures that the comparison data is consistent with the initial benchmark in terms of load conditions, measurement methods, and feature extraction rules. The second part addresses the problem that the three types of responses—diagnostic stiffness, hysteresis dissipation, and residual displacement—have different dimensions, different degradation directions, and different sensitive stages, making direct comparison impossible.

[0101] It should be noted that the term "irreversible interface degradation" in this step is an operational definition of the recovery load, recovery stability threshold, number of consecutive judgments, and observation timescale specified in step S3 of this detection method. In other words, it refers to the deviation of the diagnostic response from the initial interface response baseline in step S1 after the bonded interface has reached the recovery termination state. This statement does not imply that the corresponding state has been proven absolutely unrecoverable from an infinite timescale or material microscopic mechanism perspective. Rather, it is used to distinguish between recoverable responses that have entered a stable fluctuation range and interface state changes that are still retained at the current detection timescale.

[0102] Part 1: Acquisition of diagnostic response data after recovery.

[0103] For the Each durability loading segment records the current cumulative loop count in step S2. Next, perform unloading and recovery according to step S3. When Equation 4 first determines that the current bonding interface has reached the recovery termination state, keep the sample clamping state, loading direction, bonding area displacement measurement reference position, and environmental conditions unchanged, and directly enter the post-recovery diagnosis process corresponding to the current durability loading segment. During the recovery process in step S3 and the diagnosis process in step S4, the durability cycle count in step S2 will not be increased. Therefore, the current post-recovery diagnosis result will always be the same as the cumulative cycle count. correspond.

[0104] In this embodiment, the preset recovery load is preferably set as the diagnostic reference load in step S1 in step S3. Therefore, after reaching the recovery termination state, the preset diagnostic microcycle can be directly entered from this load level without needing to readjust from another recovery load to the diagnostic reference load. According to the aforementioned implementation conditions, the post-recovery diagnosis still uses a diagnostic peak load of 0.8 kN, a diagnostic reference load of 0.1 kN, a diagnostic loading frequency of 0.5 Hz, and a sinusoidal load waveform. Six diagnostic microcycles are executed each time, and the load data and the relative displacement data of the bonding area continue to be synchronously collected at 100 Hz. The purpose of keeping the above parameters consistent with step S1 is to ensure that the difference between the post-recovery diagnostic response and the initial interface response reference mainly reflects the state change of the bonding interface after endurance cycling and specified recovery, rather than being caused by changes in the diagnostic load or data sampling conditions.

[0105] The load data for post-recovery diagnosis continues to be acquired by the force sensor used in step S1, and the displacement data continues to be the relative displacement along the loading direction between the same measurement reference positions on both sides of the bonded area. If step S1 uses the beam displacement corrected for system flexibility, then step S4 continues to use the same flexibility correction procedure and the same calibration parameters, without changing the displacement definition during the durability loading process. This yields the... The recovery load data and recovery displacement data corresponding to each durability loading segment.

[0106] After obtaining the recovered load data and recovered displacement data, the data is processed according to the same loop partitioning rules and feature extraction methods as in step S1. In this embodiment, instead of redesigning another set of diagnostic feature algorithms in step S4, Equations 1 to 3 of step S1 are called again: Equation 1 is used to determine the robust diagnostic stiffness within the 20% to 80% load variation range of the loading branch in each effective diagnostic microcycle; Equation 2 is used to determine the hysteretic dissipation characteristics based on the discrete load-displacement closed path of the complete diagnostic microcycle; and Equation 3 is used to determine the residual displacement characteristics based on the displacement statistical window under the same diagnostic reference load at the beginning and end of the cycle.

[0107] Similar to step S1, the first post-recovery diagnostic micro-cycle is used to smoothly transition the adhesive interface from the constant load recovery state to the periodic diagnostic state, and does not participate in the post-recovery eigenvalue statistics; the second to sixth diagnostic micro-cycles are considered as five effective diagnostic cycles. The diagnostic stiffness, hysteretic dissipation characteristics, and residual displacement characteristics obtained from the five effective cycles are arithmetically averaged, and the corresponding results are recorded as the post-recovery diagnostic stiffness. Hysteresis dissipation characteristics after recovery and residual displacement characteristics after recovery .in, The unit is N / mm. The unit is N·mm. The unit is mm. These three together constitute the first... The diagnostic response data after recovery for each durability loading segment is used, but the three types of data with different dimensions are not directly summed at this stage.

[0108] Using the exact same feature extraction rules as in step S1 is crucial. If the initial benchmark uses one stiffness calculation method, while the post-recovery diagnosis uses a different regression interval or outlier handling method, the difference between the initial and recovered values ​​will simultaneously include changes in material state and algorithm. This embodiment, by fixing the diagnostic load, measurement location, sampling frequency, effective cycle selection method, and calculation rules from Equations 1 to 3, ensures that the post-recovery diagnostic response corresponding to each durability node is consistent with the value established in step S1. , and Perform a comparison with similar types.

[0109] Part Two: Pre-determination of characteristic scale and degradation direction.

[0110] Before fusing the differences in the three types of recovered responses, it is necessary to predetermine the preset characteristic scales corresponding to each response dimension. The reason for setting preset characteristic scales is that diagnostic stiffness, hysteretic dissipation characteristics, and residual displacement have different physical dimensions of N / mm, N·mm, and mm, respectively, and even under the same degree of interface state change, the natural numerical ranges of the three characteristics are significantly different. If the three original differences are directly added together, the feature with the larger numerical magnitude will only dominate the comprehensive result due to its unit and magnitude, and cannot reflect the true deviation of each of the three response dimensions from its normal repetitive fluctuations.

[0111] In this embodiment, before the start step S1 of the formal test specimen, a non-durability-loaded reference specimen prepared in the same batch as the test specimen is used to determine the preset stiffness characteristic scale. Hysteresis dissipation preset characteristic scale and residual displacement preset characteristic scale The reference specimen does not undergo the durability cyclic loading step S2. Instead, it completes 10 independent diagnostics continuously under the same environmental and clamping conditions. Each diagnostic uses the same diagnostic load parameters, sampling method, effective cycle selection rules, and feature extraction methods of Equations 1 to 3 as in step S1. Recovery is completed between two adjacent independent diagnostics according to the recovery load and recovery termination criteria specified in step S3.

[0112] For the three response dimensions of stiffness, hysteresis dissipation, and residual displacement, the absolute changes of the 2nd to 10th independent diagnostic results relative to the 1st diagnostic result were statistically analyzed. The mean and standard deviation of the corresponding absolute changes were calculated, and the sum of the mean and three times the standard deviation was used as the candidate value of the corresponding preset feature scale. The reason for using this statistical boundary is that the preset feature scale should cover most of the normal repetitive changes generated by sensor noise, clamping repeatability, small fluctuations in loading control, and the feature extraction process under no-durability loading conditions. This ensures that the values ​​after subsequent scale unification have an interpretable meaning of "the deviation multiple relative to the level of normal repetitive changes," rather than directly using the absolute size of the initial feature itself as the denominator.

[0113] Meanwhile, to avoid the abnormal amplification of degenerate features after scale unification due to candidate scales being too small or close to zero, it is also necessary to determine the minimum feature change that can be stably distinguished for each response dimension under the current measurement system and feature extraction process. For diagnosing stiffness and hysteresis dissipation features, the minimum non-zero feature change that can be stably and repeatedly identified is determined based on the nominal resolution of the force sensor and displacement measurement device, the 100 Hz sampling condition, and the actual repeated output of Equations 1 and 2. For residual displacement, the corresponding lower limit is determined based on the minimum displacement difference that can be stably and repeatedly distinguished by the displacement measurement device and Equation 3 under the same diagnostic reference load. If the candidate scale obtained by "mean plus 3 times the standard deviation" for a certain response dimension is less than the minimum reliable distinguishable change for that dimension, then the minimum reliable distinguishable change is used as the formal preset feature scale. This avoids the excessive amplification of subsequent small noise due to occasional small fluctuations obtained from the reference test.

[0114] The preset degradation direction is also determined through reference durability tests in the same batch before the formal testing of the test specimens begins, and remains fixed during the same batch of formal testing. Specifically, the reference specimens are subjected to the same steps as the formal testing: S2 segmented durability loading, S3 recovery termination judgment, and S4 post-recovery diagnosis process to obtain three types of response characteristics for multiple consecutive cumulative cycle nodes. For each response dimension, its change sign and continuity relative to the initial baseline are compared. Only when a certain change direction repeatedly appears in multiple consecutive durability nodes of most valid reference specimens, and the change in this direction can continuously exceed the normal fluctuation range of repeated diagnosis without durability loading, is it determined as the preset degradation direction corresponding to the current material system.

[0115] This embodiment focuses on the reference durability test of a two-component epoxy adhesive bonded to an aluminum alloy single-lap interface. The direction of stiffness degradation is defined as a decrease in diagnostic stiffness, the direction of dissipation degradation as an increase in hysteresis dissipation, and the direction of residual displacement degradation as an increase in residual displacement. These directions have clear mechanical meanings: a decrease in diagnostic stiffness indicates a weakened ability of the bonded area to resist deformation within the same low-disturbance load range; an increase in hysteresis dissipation indicates enhanced energy loss between the loading and unloading paths; and an increase in residual displacement indicates a larger displacement offset retained after returning to the same diagnostic reference load. For other adhesive material systems, if the stable response direction obtained from the reference durability test differs, the corresponding degradation direction should be redefined before formal testing, rather than directly using the direction set in this embodiment.

[0116] Part 3: Determination of the amount of irreversible interface degradation.

[0117] In obtaining the first Post-recovery diagnostic stiffness of each durability-loaded segment Hysteresis dissipation characteristics after recovery and residual displacement characteristics after recovery Subsequently, the initial diagnostic stiffness characteristic values ​​established in step S1 are compared with those in step S1. Initial hysteresis dissipation characteristic value and initial residual displacement eigenvalues A comparison with similar models is performed. For the three degradation directions already determined in this embodiment—"decrease in stiffness, increase in dissipation, and increase in residual displacement"—the dimensions are first unified using the corresponding preset characteristic scales. Then, the changes opposite to the preset degradation directions are set to zero to avoid the negative degradation caused by the reverse changes generated by normal measurement fluctuations, which would then offset the degradation that has already occurred in other response dimensions.

[0118] Subsequently, a weighted secondary fusion method was used to form the first... The amount of irreversible interface degradation corresponding to each durability loading segment is specifically shown in Equation 5: ; in, For the first Stiffness degradation characteristic value corresponding to each durability loading segment For the first The dissipation degradation characteristic value corresponding to each durability loading segment For the first The residual displacement degradation characteristic value corresponding to each durability loading segment The initial diagnostic stiffness characteristic value determined in step S1, For the first Post-recovery diagnostic stiffness corresponding to each durability loading segment The initial hysteresis dissipation characteristic value determined in step S1, For the first Hysteresis dissipation characteristics after recovery for each durability loading segment The initial residual displacement characteristic value determined in step S1, For the first The residual displacement characteristics after recovery corresponding to each durability loading segment. Predetermine characteristic scales for stiffness. Pre-defined characteristic scales for hysteresis dissipation Predetermine the characteristic scale for the residual displacement. The preset fusion weights are the stiffness degradation features. The preset fusion weights are the features corresponding to dissipative degradation. The preset fusion weights are the residual displacement degradation features. For the first The amount of irreversible interface degradation corresponding to each durable loading segment. For the durability loading section number, This means taking the larger of the two values ​​within the parentheses.

[0119] In Equation 5, all three preset fusion weights are non-negative, and their sum is 1. Compared to simple linear weighted summation, weighted quadratic fusion first squares the magnitude of each degradation feature before combining them according to the preset weights. Therefore, when a response dimension deviates significantly from its normal repeating scale, that dimension will not be weakened by simple averaging due to the temporarily smaller values ​​of the other two response dimensions. Simultaneously, the three degradation features have already been dimensionless and their degradation directions unified before fusion, so the squaring operation does not introduce dimensional mixing issues. Finally, the square root is used to ensure that the comprehensive index maintains a numerical scale similar to that of each dimensionless degradation feature, facilitating longitudinal comparisons between different cumulative cycle nodes.

[0120] In Formula 5 The range of values ​​for is from 0 to positive infinity. When When, it indicates that the current post-recovery diagnostic state has not formed a positive degradation deviation exceeding the initial baseline in any of the three degradation directions predetermined in this embodiment; when When the value increases, it indicates that at least one response dimension has deviated more significantly from the corresponding preset feature scale, and the overall interface degradation state is more pronounced. This is a dimensionless testing indicator and should not be interpreted as the percentage of interface damage, the percentage of remaining strength, or the probability of failure, for example... This does not mean that the interface is 80% damaged.

[0121] The preset fusion weights are determined through independent durability pre-tests of reference samples from the same batch before the formal testing of the test samples begins. Furthermore, weight verification must be performed specifically for the weighted secondary fusion method used in Equation 5, and weight results are not directly transferred from other fusion methods. Specifically, multiple reference samples from the same batch are selected, and the same durability load, segmentation method, recovery criterion in step S3, and diagnostic method in step S4 are used as in the formal testing to obtain multiple preset cumulative cycle count nodes. , and Before the reference experiment begins, consecutive early, middle, and late evaluation intervals are pre-divided according to the cumulative number of cycles. Once the stage boundaries are determined, they are not adjusted in reverse based on the candidate weight calculation results.

[0122] During the weighted candidate verification, each combination satisfying that the three candidate weights are non-negative and their sum is 1 is substituted into Equation 5 to recalculate the corresponding values ​​of each reference sample at each cumulative cycle node. First, a stage-based identifiability screening is performed: the overall degradation amount obtained from candidate weights should be able to retain the continuous state changes from the early to the middle and late stages, and the overall difference between stages should not continuously fall within the overall fluctuation range formed by repeated diagnosis without durability loading in multiple consecutive observation nodes of the corresponding stage; candidate weights that do not meet this condition are excluded. Subsequently, for the candidate weights that pass the screening, the differences between different reference samples at the same cumulative cycle number node are compared. The degree of dispersion was determined, and weight combinations with smaller dispersion across samples were selected as formal fusion weights while maintaining the identifiability of stage changes.

[0123] The reason for using the above method to determine the weights is that the three response dimensions have different sensitivities at different stages of durability evolution. Diagnostic stiffness may be more pronounced when the interface bearing capacity decreases in the later stages, while hysteretic dissipation and residual displacement may have already undergone continuous changes in earlier stages. If a particular response dimension is designated as more important based solely on the operator's subjective judgment, the overall degradation amount may be biased towards a single characteristic. By simultaneously constraining stage identifiability and cross-sample repeatability, the preset fusion weights can be matched with the current adhesive material system, testing equipment, and the actual output characteristics of Equation 5. Once the weights are determined for the current testing batch, they remain fixed during the execution of steps S1 to S6 of the formal test sample and are not temporarily changed based on the degradation results that have subsequently appeared in the formal test sample.

[0124] It should also be noted that if the adhesive material, substrate, adhesive layer thickness, bonding structure, loading equipment, or displacement measuring device is changed, or the diagnostic load, sampling frequency, feature extraction parameters in step S1, or the recovery criterion in step S3 is altered, resulting in a significant change in the level of fluctuation in the non-durability repeat diagnostic test or the direction of the reference durability response, the affected components should be re-determined before formal testing. , , The recalibration requires setting a predefined degradation direction and three predefined fusion weights. This recalibration must ensure that the input of Equation 5 always corresponds to the current actual measurement conditions, rather than mechanically applying the scales and weights obtained from a certain batch to different detection systems.

[0125] Complete the first After calculating the value of Equation 5 corresponding to each durability loading segment, the result will be... The cumulative number of loops recorded in step S2 Establish a one-to-one correspondence based on the same durability loading segment number to form the "cumulative cycle count - irreversible interface degradation" data node for the current durability node. Step S4 does not rely on a single Instead of directly determining whether the absolute size has entered the interface durability transition phase, the durability loading segment is obtained sequentially from multiple durability loading segments. and its corresponding Step S5 is then used to analyze the rate of irreversible interface degradation between adjacent nodes and its continuous trend.

[0126] The irreversible interface degradation is determined by using diagnostic stiffness, hysteretic dissipation characteristics, and residual displacement characteristics together because the interface state information corresponding to the three response dimensions is different. Diagnostic stiffness mainly reflects the change in the bearing slope of the bonded area within the specified diagnostic load range; hysteretic dissipation characteristics mainly reflect the change in energy dissipation between the loading and unloading paths; and residual displacement characteristics mainly reflect the displacement offset that remains after returning to the same diagnostic reference load. By first removing the main recoverable response that is still changing in step S3, and then performing scale unification, direction unification, and weighted secondary fusion on the three recovered diagnostic dimensions in step S4, the impact of random fluctuations or stage insensitivity of a single response dimension on the comprehensive durability degradation evaluation can be reduced.

[0127] Thus, the first Each durability loading segment forms a complete data loop between steps S2 and S4: Step S2 applies the specified cyclic durability load and records the cumulative number of cycles. Step S3 restores the adhesive interface to the recovery termination state determined by Equation 4 without increasing the number of durability cycles; Step S4 re-invokes Equations 1 to 3 under the same conditions as Step S1 to obtain... , and Then, by substituting the fixed feature scale, degradation direction, and fusion weights from before the formal detection into Equation 5, we obtain... This yields a solution that can be directly used in step S5. and Corresponding data.

[0128] S5: Based on the irreversible interface degradation amount and cumulative cycle count corresponding to each durability loading segment, determine the relationship between the irreversible interface degradation amount and the cumulative cycle count, and determine the interface durability transition stage based on the relationship.

[0129] Obtain the irreversible interface degradation amount and the cumulative number of cycles corresponding to each durability loading segment, and construct a degradation data sequence according to the order of the cumulative number of cycles; The irreversible interface degradation rate between adjacent durability loading segments is determined based on the difference between the irreversible interface degradation amount between adjacent durability loading segments and the difference between the cumulative number of cycles in the degradation data sequence. The relationship between the amount of irreversible interface degradation and the cumulative number of cycles is determined based on the degradation data sequence, and the degree of change of the relationship between adjacent cumulative number of cycles is characterized by the irreversible interface degradation development rate between each adjacent durability loading segment.

[0130] A stable degradation interval is determined based on the change in the irreversible interface degradation rate between multiple consecutive adjacent durability loading segments. When the change in the first preset number of consecutive segments is not greater than a preset stable change threshold, the corresponding consecutive durability loading interval is determined as the stable degradation interval. A baseline degradation rate is determined based on the irreversible interface degradation rate within the stable degradation interval. According to the order of cumulative cycle count, the irreversible interface degradation rate between each adjacent durability loading segment after the stable degradation interval is compared with the baseline degradation rate, and the corresponding degradation deviation is determined based on the difference between the two. When the degradation deviation of a second consecutive preset number of such deviations is not less than a preset turning point deviation threshold, and the corresponding irreversible interface degradation rate shows a continuous increasing trend, the next durability loading segment corresponding to the first irreversible interface degradation rate among the second consecutive preset number of such irreversible interface degradation rates is determined as the interface durability turning point stage.

[0131] In this embodiment, step S5 receives the cumulative number of cycles recorded in step S2 and the amount of irreversible interface degradation obtained in step S4, forms a degradation data sequence according to the order of durability loading, and identifies the durability stage of the bonding interface transitioning from stable degradation to continuously accelerating degradation by the development rate, stable degradation interval, and continuous deviation relationship. The turning point determination uses the current sample's early stable degradation level as its own benchmark, and does not use the absolute magnitude of a single irreversible interface degradation amount as the turning point criterion.

[0132] Part 1: Degraded data sequences and the rate of irreversible interface degradation.

[0133] After completing steps S2 to S4 corresponding to multiple durability loading segments, for the first... Each durability loading segment yields the cumulative number of loops. and irreversible interface degradation If a total of The effective durability nodes are then formed in ascending order of cumulative cycle count. Degraded data sequences.

[0134] Step S5 uses the actual cumulative number of cycles recorded in step S2. If the actual number of cycles completed in a particular durability loading segment differs from the preset value due to equipment pauses or abnormal handling, the cumulative number of cycles is not corrected at equal intervals. Step S5 also retains the actual number of cycles obtained in step S4. It is not required that all adjacent nodes increase strictly monotonically; when individual nodes show a slight decline due to measurement repeatability or local state fluctuations, no forced monotonicization is performed.

[0135] No. The durability node to the first The average irreversible interface degradation rate between durable nodes is determined by the following formula and is attributed to the node located on the back side. One durability loading segment, Equation 6: ; in, For the first The durability node to the first The average rate of irreversible interface degradation between durable nodes For the first The amount of irreversible interface degradation corresponding to each durable loading segment. This represents the amount of irreversible interface degradation corresponding to the previous durability loading segment. For the first The actual cumulative number of cycles at the end of each durability loading segment. This represents the actual cumulative number of cycles at the end of the previous durability loading phase. The total number of effective durability nodes, This is the index for the durable loading segment.

[0136] because It is a dimensionless quantity. The dimension of is sub-dimension When a certain adjacent node When there is a slight pullback, the corresponding It can be a negative value, which is reserved for subsequent continuous change judgment and is not used as a criterion for interface recovery or durability transition alone.

[0137] Part Two: Determination of the preset stable change threshold and the preset turning deviation threshold.

[0138] The preset stable change threshold and the preset turning point deviation threshold are determined by reference durability tests of the same batch before the formal test of the sample to be tested begins. The same steps as the formal test are used: step S2 segmentation method, step S3 recovery criterion, step S4 calculation method for irreversible interface degradation amount and formula 6 calculation method for development rate.

[0139] Before formal threshold statistics are performed, a complete cumulative cycle count-irreversible interface degradation sequence and evolution rate sequence are obtained using independent exploratory reference samples, and a continuous calibration window is fixed accordingly. The starting position of the calibration window avoids the initial transition zone corresponding to the first evolution rate, and the ending position is located before macroscopic failure, when the durability load cannot be stably maintained, or when the evolution rate shows a continuous increasing trend. Once the window numbering is determined before formal threshold statistics, all subsequent reference samples use the same numbering range and are not adjusted based on the subsequent curve morphology of each reference sample.

[0140] This embodiment uses five reference samples from the same batch for formal threshold statistics. For the preset stable change threshold, the absolute value of the difference between adjacent development rates within a fixed pre-calibration window is calculated. The corresponding data for each reference sample are summarized, and their mean and standard deviation are calculated. The sum of the mean and three times the standard deviation is determined as the preset stable change threshold. This threshold is used to characterize the upper bound of normal variation between adjacent development rates in the early stable degradation state.

[0141] For the preset turning point deviation threshold, within the same fixed pre-calibration window, first calculate the average development rate of each reference specimen as the reference baseline development rate for that specimen. Then calculate the positive deviation when each development rate is higher than the corresponding reference baseline. For development rates not higher than the reference baseline, the positive deviation is recorded as zero. Summarize the normal positive deviations of each reference specimen, calculate their average and standard deviation, and determine the sum of the average and three times the standard deviation as the preset turning point deviation threshold. This threshold is used to characterize the normal upward deviation of the development rate from its baseline in the early stable degradation state.

[0142] Preset stable change threshold Deviation from preset turning threshold The comparison objects are different. The former is used to determine whether adjacent growth rates remain stable, while the latter is used to determine whether subsequent growth rates have significantly exceeded the fixed benchmark. Both remain fixed after the formal testing begins.

[0143] First preset quantity Second preset quantity Similarly, candidate validation was performed using a reference evolution rate sequence before formal testing. For Stable interval identification begins with a small number of consecutive candidate values, selecting the smallest candidate value that can repeatedly identify previously stable and degenerate intervals in valid reference samples without generating additional stable intervals due to short-term, accidental small fluctuations; for Candidate turning point sequences are identified based on a preset turning point deviation threshold and a continuously increasing development rate. The smallest candidate value is selected that can exclude false turning points caused by a short-term rate surge followed by an immediate decline and can provide stable confirmation of the continuous acceleration phase. This embodiment determines the value according to the above method. , .

[0144] Part Three: Stable Degradation Range and Baseline Degradation Rate.

[0145] After obtaining the development rate sequence of the formal test specimen, the stable degradation intervals are searched in ascending order of cumulative cycle count. Stable degradation refers to the situation where irreversible interface degradation continues to develop with durability cycles, but the development rate changes of consecutive adjacent intervals remain within the range limited by a preset stable change threshold.

[0146] The starting index and baseline degradation rate of the stable degradation interval are determined according to the following formula, Equation 7: , ; in, The initial index for the development rate that first satisfies the continuous stability condition. This serves as the starting index for the candidate stable interval. For the first preset quantity, To ensure stable index determination within the window, and The rate of degradation at adjacent irreversible interfaces. To preset a stable change threshold, As a benchmark rate of degradation, This represents the total number of nodes with effective durability.

[0147] Equation 7 requires continuity The changes in each adjacent development rate are no greater than The window that first satisfies the condition in the cumulative cyclic sequence is used as the stable degradation interval; this window contains A continuous rate of development, with its arithmetic mean as a fixed baseline rate of degradation development. . Once determined, it will not be updated according to the subsequent development rate.

[0148] If there are no nodes in the current effective durability that satisfy equation 7 If no baseline degradation rate is established within the current detection range, the interface durability transition determination based on this baseline will not continue.

[0149] Part Four: Deviation in Degradation and the Inflection Point in Interface Durability Sure Then, a turning point search is performed only on the development rate after the stable degradation interval. The deviation of a development rate from a fixed baseline from its degradation and the initial index of the development rate that first meets the sustained transition condition are determined according to the following formula: Formula 8: , ; in, For the first The deviation of the rate of irreversible interface degradation from the baseline rate of degradation in the positive direction. For the first The rate of irreversible interface degradation. As a benchmark rate of degradation, The initial index for the development rate that first satisfies the continuous transition condition. This serves as the starting index for candidate transitions. To establish the starting index for the stable degradation interval, For the first preset quantity, For the second preset quantity, The index within the continuous transition determination window. To preset the turning deviation threshold, This represents the total number of nodes with effective durability.

[0150] In Equation 8, only positive deviations when the development rate exceeds the baseline degradation development rate are retained; the candidate inflection point is located after the stable degradation interval and is required to be continuous. Each deviation from the degenerative development is not less than At the same time, corresponding Each development rate increases strictly in stages. The index that first satisfies the above conditions is denoted as... .

[0151] According to the attribution rules of Formula 6, Indicates the first The durability node to the first The development rate between durable nodes, and attributed to the th The first durability loading segment, therefore the first The durability loading segment was determined to be the interface durability transition phase. Although the transition conditions require further investigation... The development rates are confirmed by all of them, but the starting position of the turning point still corresponds to the development rate that is first in the continuously confirmed sequence.

[0152] If no equation 8 is satisfied by the end of the detection period. If no interface durability transition phase that meets the preset continuous criteria is identified within the current cumulative cyclic detection range, it is determined that no such phase has been identified within the current cumulative cyclic detection range.

[0153] Part 5: Parameter Fixation and Step Output.

[0154] When changing the adhesive material, substrate, adhesive layer thickness, or bonding structure, or altering the durability load level, durability loading frequency, number of segmented cycles, diagnostic sampling conditions, recovery criteria, characteristic scale, or fusion weight, resulting in a significant change in the amount of irreversible degradation of the reference interface or the distribution of the reference evolution rate, the preliminary calibration window determination, preset stable change threshold calibration, preset inflection deviation threshold calibration, and verification of the first and second preset quantities should be re-executed before the formal testing of the sample begins. Once the relevant parameters are determined for the current testing batch, they should remain fixed during the formal testing process.

[0155] Step S5 outputs the relationship between irreversible interface degradation and cumulative cycle count, the irreversible interface degradation rate sequence, the stable degradation interval, the baseline degradation rate, and the interface durability transition stage. Step S5 does not equate the interface durability transition stage with the final failure time, nor does it perform remaining lifetime prediction in this step; Step S6 generates the interface durability test results based on the cumulative cycle count of the durability loading segment corresponding to the interface durability transition stage and the irreversible degradation process before and after the transition.

[0156] S6: Generate the interface durability test results of the adhesive material to be tested based on the amount of irreversible interface degradation, the change relationship, and the interface durability transition stage corresponding to each durability loading segment.

[0157] The irreversible degradation process of the adhesive interface is determined based on the amount of irreversible interface degradation corresponding to each durability loading segment and the relationship between the amount of irreversible interface degradation and the cumulative number of cycles. The durability transition cycle number is determined based on the cumulative number of cycles of the durability loading segment corresponding to the interface durability transition stage. The irreversible degradation process corresponding to the durability transition cycle number is determined as the pre-transition degradation process, and the irreversible degradation process corresponding to the durability transition cycle number is determined as the post-transition degradation process. The interface durability test results of the adhesive material to be tested are generated based on the degradation process before the transition, the degradation process after the transition, and the number of durability transition cycles.

[0158] In this embodiment, step S6 is used to divide the interface degradation process of the adhesive material to be tested under the current durability test conditions into stages based on the irreversible interface degradation amount corresponding to each durability loading segment obtained in step S4, and the relationship between the irreversible interface degradation amount and the cumulative number of cycles and the interface durability transition stage obtained in step S5, and generate the interface durability test result.

[0159] Step S6 does not recalculate the irreversible interface degradation amount, nor does it re-execute the determination of the stable degradation interval and the interface durability transition stage. Step S4 has already determined the irreversible interface degradation amount corresponding to each cumulative cycle number node, and Step S5 has already determined the relationship between the irreversible interface degradation amount and the cumulative cycle number, as well as the interface durability transition stage. Therefore, this step directly uses the above results to determine the irreversible degradation process, the durability transition cycle number, and the degradation process before and after the transition.

[0160] Part 1: Determining the irreversible degradation process.

[0161] After processing through steps S2 to S5, for the first... One effective durability loading segment has been formed, and the cumulative number of cycles has been reached. Corresponding irreversible interface degradation amount A one-to-one correspondence.

[0162] Arrange the durability loading segments in ascending order of cumulative cycle count. and By combining the relationship between the amount of irreversible interface degradation determined in step S5 and the cumulative number of cycles, the irreversible degradation process of the bonding interface to be tested is determined.

[0163] The irreversible degradation process includes at least the cumulative number of cycles and the amount of irreversible interface degradation corresponding to each effective durability loading segment, and reflects the evolution of the irreversible interface degradation state from the first durability observation node to the current detection endpoint in the order of durability loading.

[0164] In this embodiment, when a fixed segmentation method of 1000 cycles per durability loading segment is adopted, each durability node is arranged in the order of the cumulative number of cycles from 1000, 2000, 3000 until the actual detection endpoint. If the actual number of cycles completed for a certain durability loading segment is different from the preset number of cycles for each segment, the position of the corresponding node is determined according to the actual cumulative number of cycles recorded in step S2, and no equal-interval correction is made to the cumulative number of cycles.

[0165] The irreversible interface degradation rate obtained in step S5 It can be associated with and stored in relation to the corresponding durability interval to characterize the degree of change between two adjacent irreversible degradation nodes; the basic state data of the irreversible degradation process consists of the cumulative number of cycles. and corresponding irreversible interface degradation amount constitute.

[0166] The irreversible degradation process can be represented by a data sequence arranged according to the cumulative number of cycles, or by a degradation process curve with the cumulative number of cycles as the horizontal axis and the amount of irreversible interface degradation as the vertical response value. If a curve is used, the connection between adjacent actual detection nodes is only used to show the trend of change, and is not considered as a new measured durability node, nor does it change the interface durability transition stage determined in step S5.

[0167] Part Two: Determining the Number of Durability Turnaround Cycles.

[0168] When step S5 identifies a valid interface durability transition stage according to formula 8, the cumulative number of cycles recorded by step S2 at the end of the durability loading segment corresponding to the interface durability transition stage is obtained, and the cumulative number of cycles is determined as the durability transition cycle number of the adhesive material to be tested under the current test conditions.

[0169] Specifically, if step S5 determines the first If the first durability loading segment is the interface durability transition phase, then the first... Cumulative number of cycles at the end of each durability loading segment This is determined as the number of durability transition cycles. This represents the cumulative number of cycles corresponding to the interface durability transition stage. Its value is directly read from the actual cumulative number of cycles recorded in step S2, without additional interpolation or extrapolation.

[0170] The durability transition cycle number corresponds to the starting position of the continuous accelerated degradation identified in step S5. Although step S5 needs to use the continuous acceleration trend confirmed by the development rates of multiple irreversible interface degradations after this starting node, the durability transition cycle number still corresponds to the next durability loading segment to which the development rate at the beginning of the continuous transition sequence belongs, instead of using the last durability loading segment corresponding to the completion of all continuous confirmations.

[0171] The durability transition cycle count is used to characterize the cumulative cycle position at which the rate of irreversible interface degradation begins to show a continuously accelerated, node-verified rate of increase relative to the previous stable degradation baseline, under the current specified durability load, recovery conditions, and diagnostic conditions. The durability transition cycle count is not equivalent to the final fracture cycle count of the adhesive interface, nor does it directly represent the failure life of the adhesive material.

[0172] Part Three: Determining the Degradation Process Before and After the Turning Point.

[0173] After determining the number of durability transition cycles, this number of durability transition cycles is used as the stage boundary of the irreversible degradation process.

[0174] Each durability node with a cumulative cycle count less than the durability transition cycle count and its corresponding irreversible interface degradation amount are classified into the pre-transition degradation process; each durability node with a cumulative cycle count equal to or greater than the durability transition cycle count and its corresponding irreversible interface degradation amount are classified into the post-transition degradation process.

[0175] Therefore, the data node corresponding to the number of durability transition cycles belongs to the post-transition degradation process and is not included in the pre-transition degradation process, so that the same durability node has a unique stage affiliation.

[0176] The pre-transition degradation process indicates that the adhesive interface has already developed and continues to accumulate irreversible degradation, but has not yet reached the stage of continuously accelerating the transition condition specified in step S5. The pre-transition degradation process does not mean that there is no irreversible change in the adhesive interface, nor does it require that the amount of irreversible interface degradation in this stage remain unchanged.

[0177] The post-turn degradation process represents the irreversible degradation evolution from the continuously accelerating starting node identified in step S5 to the current detection endpoint. The turning point is jointly confirmed by multiple consecutive development rates. Therefore, the post-turn degradation process is used to represent the overall evolution after entering the continuously accelerating degradation stage, and it is not required that the development rate of each individual adjacent interval after the turning point permanently maintain a strictly monotonically increasing trend.

[0178] Part 4: Generation of Interface Durability Test Results.

[0179] Based on the degradation process before the transition, the degradation process after the transition, and the number of durability transition cycles, the interface durability test results of the adhesive material to be tested are generated.

[0180] When step S5 identifies the interface durability transition stage, the interface durability test result includes at least the pre-transition degradation process, the post-transition degradation process, and the number of durability transition cycles. The pre-transition degradation process characterizes the evolution of irreversible interface degradation with the cumulative number of cycles before the durability transition cycle count; the post-transition degradation process characterizes the subsequent evolution of irreversible interface degradation from the durability transition cycle count to the detection endpoint; and the number of durability transition cycles identifies the starting cycle position of the continuously accelerating degradation confirmed by the continuous development rate criterion in step S5.

[0181] As a specific output method, an interface durability test result table can be established, recording the durability loading segment number, cumulative number of cycles, amount of irreversible interface degradation, and degradation stage identifier. For durability nodes before the durability transition cycle count, the degradation stage identifier is set to "before transition"; for durability nodes starting from the durability transition cycle count, the degradation stage identifier is set to "after transition", and the durability transition cycle count is recorded separately.

[0182] Irreversible degradation history curves can also be generated based on the same data. The positions corresponding to the number of durability transition cycles can be marked on the curves, and the degradation history before and after the transition can be distinguished. Data tables and degradation history curves are different expressions of interface durability test results and do not change the test data and stage judgment results obtained in steps S1 to S5.

[0183] Part 5: Result processing when no durability transition is detected within the current detection range.

[0184] If step S5 does not identify an interface durability transition stage that satisfies the continuous criterion of Equation 8 within the current cumulative loop detection range, then step S6 will not manually specify the number of durability transition loops, nor will it take the last durability loading segment or the durability loading segment corresponding to the maximum irreversible interface degradation as the interface durability transition stage.

[0185] In this case, an irreversible degradation history is formed based on the total number of cumulative cycles and the amount of irreversible interface degradation obtained so far, and the result of the interface durability test is recorded as "No interface durability transition stage that meets the preset continuity criterion was identified within the current cumulative cycle test range". At this time, the degradation history before the transition and the degradation history after the transition are not distinguished, but the complete irreversible degradation history obtained so far is taken as the interface degradation test result within the scope of this test.

[0186] The above results indicate that, up to the current detection endpoint, there is no evidence of continuous interface acceleration that satisfies the continuous transition criterion in step S5, and it is not used to presume that a durability transition will not occur even after further increasing the durability cycles.

[0187] Part 6: Technical Boundaries of Test Results

[0188] The interface durability test results generated in step S6 are used to describe the irreversible interface degradation process and its stages of change of the adhesive material under test under the specified durability load, recovery criterion and diagnostic conditions.

[0189] Among them, irreversible interface degradation The dimensionless comprehensive degradation index determined in step S4 does not represent the percentage of interface damage; the durability turning point cycle number represents the cumulative cycle position corresponding to the continuous acceleration of the irreversible interface degradation development rate verified by consecutive nodes, and does not represent the final fracture cycle number.

[0190] This embodiment does not directly calculate the remaining service life based on the number of durability transition cycles, does not directly determine the failure probability based on the amount of irreversible interface degradation, and does not directly identify the interface durability transition stage as the macroscopic failure stage of the adhesive interface.

[0191] So far, step S1 establishes the initial interface response benchmark, step S2 applies segmented cyclic durability treatment and records the cumulative number of cycles, step S3 determines the recovery termination state based on the recovery displacement change, step S4 performs the same condition diagnosis under the recovery termination state and determines the amount of irreversible interface degradation, step S5 determines the interface durability transition stage based on the development rate of the amount of irreversible interface degradation with the cumulative number of cycles, and step S6 forms the pre-transition degradation process, post-transition degradation process and durability transition cycle number based on the irreversible degradation process and the interface durability transition stage, and generates the interface durability test results.

[0192] Example 2 is the second embodiment of the present invention, which differs from the previous embodiment in that: If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art or the current technical solution, can be embodied in the form of a software product. This current computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0193] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-including system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0194] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0195] Example 3, referring to Figure 2 In one embodiment of the present invention, an adhesive material interface durability testing system is provided, which includes an initial interface response benchmark determination module, a segmented cyclic durability loading module, a recovery termination state determination module, an irreversible interface degradation amount determination module, an interface durability transition stage determination module, and an interface durability test result generation module. Initial interface response benchmark determination module: Apply a preset diagnostic micro-cyclic load to the bonding interface of the adhesive material to be tested, acquire initial diagnostic response data, and determine the initial interface response benchmark based on the initial diagnostic response data; Segmented Cyclic Durability Loading Module: Performs segmented cyclic durability loading on the bonding interface, consisting of multiple durability loading segments. Records the corresponding cumulative number of cycles at the end of each durability loading segment, and enters the next durability loading segment after completing steps S3 and S4 corresponding to the current durability loading segment. Recovery Termination State Determination Module: After each durability loading segment ends, unloading recovery is performed on the bonding interface, the interface response data of the recovery stage is obtained, and the recovery termination state is determined based on the change of the interface response data of the recovery stage with the recovery time. Irreversible interface degradation determination module: After reaching the recovery termination state, the preset diagnostic micro-cycle load is applied again to obtain the post-recovery diagnostic response data, and the irreversible interface degradation corresponding to each durability loading segment is determined based on the difference between the post-recovery diagnostic response data and the initial interface response benchmark. Interface durability transition stage determination module: Based on the irreversible interface degradation amount and cumulative cycle count corresponding to each durability loading segment, determine the relationship between the irreversible interface degradation amount and the cumulative cycle count, and determine the interface durability transition stage based on the relationship. Interface durability test result generation module: Based on the irreversible interface degradation amount, the change relationship, and the interface durability transition stage corresponding to each durability loading segment, the interface durability test result of the adhesive material to be tested is generated.

[0196] Example 4, an embodiment of the present invention, provides a method for testing the interface durability of adhesive materials.

[0197] This embodiment compares and explains the test results obtained by the adhesive material interface durability testing method of the present invention by setting up control samples with different recovery methods and stage judgment methods.

[0198] Using the same batch of two-component epoxy structural adhesive, single-lap joint samples were prepared with 6061 aluminum alloy plates as the substrate. The overlap length was 25 mm, the overlap width was 12.5 mm, and the adhesive layer thickness was controlled at 0.20 mm ± 0.02 mm. All samples were prepared under the same substrate treatment, adhesive application, and curing conditions. After curing, they were placed in an environment of 23 ℃ ± 2 ℃ and 50% ± 5% relative humidity for more than 48 h.

[0199] Nine samples with intact appearance and no obvious abnormalities in the initial diagnostic response were selected for formal control testing. Among them, F-01 to F-03 constitute the method group of the present invention, and adopt the complete testing process described in Example 1; C1-01 to C1-03 constitute the fixed recovery time control group, whose durability loading conditions, diagnostic microcirculation conditions, and subsequent feature processing methods are consistent with group F, but a fixed recovery time is used after each durability loading segment, and the recovery termination state is not determined based on the change of recovery displacement with recovery time; C2-01 to C2-03 constitute the single diagnostic stiffness criterion control group, whose durability loading conditions, dynamic recovery termination method, and post-recovery diagnosis method are consistent with group F, but the stage judgment does not adopt the multi-feature irreversible interface degradation development rate criterion of the present invention, but adopts the single post-recovery diagnostic stiffness reduction criterion.

[0200] Before the formal comparative testing begins, a reference sample from the same batch is used to pre-determine the interface damage initiation load, recovery stability threshold, characteristic scale, degradation direction, fusion weight, and transition judgment parameters according to the method disclosed in Example 1. Once these parameters are determined for the specific testing conditions, they remain fixed during the formal comparative testing process.

[0201] All three groups of samples underwent diagnostic micro-cycles with a diagnostic peak load of 0.8 kN and a diagnostic reference load of 0.1 kN. The diagnostic loading frequency was 0.5 Hz, and six diagnostic micro-cycles were performed each time. Load data and relative displacement data of the bonding area were obtained synchronously in the same way as in Example 1.

[0202] The peak value of the cyclic durability loading was set to 1.2 kN, the durability reference load was set to 0.1 kN, and the durability loading frequency was set to 1 Hz. Every 1000 complete durability cycles constituted a durability loading segment, and after each durability loading segment ended, the interface state data of the current cumulative cycle node was obtained according to the recovery and diagnostic methods of the corresponding test group. The above common detection parameters are consistent with the specific implementation conditions of Embodiment 1 of this invention.

[0203] For group F, after each durability loading segment, the load was reduced to a recovery load of 0.1 kN, and the recovery displacement was continuously acquired at a recovery detection interval of 10 s. The recovery stability threshold determined before formal testing was 0.0034 mm. When the recovery response change corresponding to 5 consecutive effective recovery detection intervals was not greater than 0.0034 mm, the bonding interface was determined to have reached the recovery termination state, and then post-recovery diagnosis was initiated.

[0204] After reaching the recovery termination state, Group F performs a diagnostic microcycle under the same conditions as the initial diagnosis, and determines the post-recovery diagnostic stiffness, post-recovery hysteresis dissipation characteristics, and post-recovery residual displacement characteristics according to Equations 1 to 3 of Example 1. Subsequently, the irreversible interface degradation amount is determined according to Equation 5 using the feature scale, degradation direction, and fusion weight pre-fixed in Example 1, and the interface durability transition stage is determined according to Equations 6 to 8 based on the cumulative number of cycles and the irreversible interface degradation amount.

[0205] For group C1, the durability loading conditions, diagnostic microcirculation conditions, data acquisition methods, and diagnostic feature processing methods are consistent with group F. The difference lies in that after each durability loading segment, a fixed 300-second wait is performed before directly executing the post-recovery diagnosis. The diagnostic entry time is not determined based on whether the current recovered displacement has met the 0.0034 mm recovery stability threshold or the criteria of five consecutive recovery detection intervals. This fixed 300-second recovery method remains unchanged across all C1 group samples and all durability loading segments. The test setup uses a fixed 300-second timeframe as the recovery entry point for group C1.

[0206] Since the C1 group may not have reached the recovery termination state specified in this invention by the end of the 300 s fixed wait, the comprehensive value obtained by the C1 group according to the same characteristic scale, degradation direction, and fusion rule as the F group is used as a comprehensive degradation index for inter-group comparison in this embodiment. When a certain C1 durability node has not yet reached the recovery termination state, this comprehensive degradation index may also be affected by the incomplete recoverable response, therefore it is not directly interpreted as the amount of irreversible interface degradation defined in this invention.

[0207] To compare the impact of a fixed recovery entry point on the identification results of subsequent stages, the comprehensive degradation index of group C1 was arranged according to the cumulative number of cycles, and the corresponding stage change nodes were obtained using the same development rate and continuous determination rules as group F. These stage change nodes are control results under fixed recovery time conditions and are not defined as interface durability transition stages determined using the complete method of this invention.

[0208] For group C2, the same dynamic recovery termination determination as group F is used after each durability loading segment ends, and the post-recovery diagnostic response is obtained according to the same diagnostic conditions after reaching the recovery termination state. Therefore, group C2 and group F are consistent in terms of the post-recovery diagnostic entry state.

[0209] The difference between Group C2 and Group F lies in the stage judgment method. To construct a control detection method with a fixed threshold for a single index, this embodiment sets an 8% decrease in the post-recovery diagnostic stiffness relative to the initial diagnostic stiffness as the single stiffness significant degradation criterion for Group C2. When the post-recovery diagnostic stiffness first reaches this decrease percentage, the corresponding cumulative number of cycles is recorded as the number of cycles for the significant degradation node identified by the single stiffness threshold criterion. The 8% threshold is only used as a fixed discrimination level for the control detection of Group C2 and is not a parameter of the interface durability transition criterion of this invention, nor does it indicate that the bonded interface has reached an 8% degree of damage or failure. The control settings for Group C2 using the 8% stiffness decrease criterion are consistent with the experimental conditions.

[0210] All three groups of samples continued to undergo durability loading until significant interface separation occurred or the preset peak durability load could not be stably reached, and the number of macroscopic failure cycles was recorded. The number of macroscopic failure cycles was only used for subsequent comparison of the stage results obtained by different detection methods and was not used to determine the interface durability transition stage of group F. Specific data can be found in Table 1.

[0211] Table 1: Reference Table for Experimental Data

[0212] The initial diagnostic stiffness, nodal recovery data after 10,000 cycles, comprehensive degradation data, and stage identification data of the specimens in the table above all correspond to the control test data.

[0213] The “Change in Recovery Response” in Table 1 represents the absolute value of the difference between the recovery displacements corresponding to two adjacent recovery detection times. Its physical dimension is displacement, and the unit is mm. 10 s is the time interval between adjacent recovery detection times, which is not a unit of the change in recovery response.

[0214] The "Comprehensive Degradation Index Obtained from 10,000 Nodes under the Same Fusion Rule" in Table 1 is used to uniformly display the comprehensive response of the three groups of samples at the same cumulative cycle node. For groups F and C2, since post-recovery diagnosis was performed after reaching the recovery termination state, this value corresponds to the comprehensive degradation characterization obtained under the same fusion rule; group F uses this value as the amount of irreversible interface degradation according to the complete method of this invention. For group C1, since the recovery termination state may not have been reached after fixing for 300 s, the corresponding value is only used as a comprehensive degradation index for control purposes.

[0215] Table 1 shows the "Number of Cycles of Stage Change Nodes Identified by the Same Development Rate Rule," used to compare Group F and Group C1. For Group F, this node represents the number of interface durability transition cycles determined by this invention; for Group C1, this node only indicates the control stage change position obtained by using the same development rate continuous criterion under fixed recovery entry conditions. Group C2 does not use this criterion, so the corresponding position is marked as "—".

[0216] The "Number of cycles for significantly degraded nodes identified by a single stiffness threshold criterion" in Table 1 applies only to group C2, so the corresponding positions for groups F and C1 are marked as "—".

[0217] As shown in Table 1, the initial diagnostic stiffness of the three groups of samples is distributed between approximately 1190 and 1230 N / mm. There is no case where the initial diagnostic stiffness of any one test group is significantly higher or lower than average. This distribution can be used for comparative analysis of subsequent recovery methods and stage judgment methods. The initial stiffness data of each sample in Table 1 exhibit the above distribution characteristics.

[0218] At the 10,000-cycle endurance node, the recovery times for F-01, F-02, and F-03 to reach the recovery termination state were 448 s, 472 s, and 461 s, respectively; while C1-01, C1-02, and C1-03 all entered the diagnostic phase after a fixed 300 s.

[0219] The changes in recovery response of the three samples in group F before diagnosis were 0.0024 mm, 0.0028 mm, and 0.0026 mm, respectively, all below the 0.0034 mm recovery stabilization threshold. The changes in recovery response of the three samples in group C1 at the end of a fixed 300 s waiting period were 0.0058 mm, 0.0066 mm, and 0.0053 mm, respectively, all above the 0.0034 mm recovery stabilization threshold.

[0220] Therefore, it can be seen that at the 10,000th node, the three samples in group F have reached the recovery termination state according to the same recovery stability criterion, while the three samples in group C1 still have a recovery displacement change that is significantly higher than the recovery stability threshold at the end of the fixed 300 s.

[0221] From the complete durability testing process, none of the three samples in group F entered the retest without reaching the condition for recovery stability, while C1-01, C1-02 and C1-03 had 8, 10 and 7 such nodes, respectively.

[0222] Further comparison of the comprehensive degradation index at 10,000 cycles revealed that the three samples from group F had values ​​of 0.502, 0.536, and 0.487, with an average of approximately 0.508; while the three samples from group C1 had values ​​of 0.691, 0.748, and 0.663, with an average of approximately 0.701. The test data also showed a significant difference in values ​​between group F and group C1 at this node.

[0223] Since Group F and Group C1 have the same durability loading conditions, diagnostic conditions, and feature processing rules, their main difference lies in the entry conditions for post-recovery diagnosis. Therefore, the recoverable response that still exists in Group C1 at the end of the fixed 300 s can be included in the subsequent diagnostic data and further change the comprehensive degradation index obtained according to the same fusion rules.

[0224] Therefore, a fixed recovery time cannot guarantee that different cumulative cycle nodes will enter the diagnosis from the same recovery state. However, by using the recovery displacement change of the current interface to determine the recovery termination state, the post-recovery diagnosis can be based on a unified state criterion.

[0225] Further comparison of group F and group C2 showed that both groups used dynamic recovery termination criteria.

[0226] At the 10,000th node, the actual recovery times of C2-01, C2-02, and C2-03 were 456 s, 478 s, and 469 s, respectively, with corresponding recovery response changes of 0.0027 mm, 0.0029 mm, and 0.0025 mm, all below the 0.0034 mm recovery stability threshold. The comprehensive degradation indices corresponding to the same node were 0.519, 0.548, and 0.501, respectively, which are in a similar range to the results of 0.502, 0.536, and 0.487 for the three samples in group F.

[0227] Therefore, Group F and Group C2 have a good comparative basis in terms of diagnosing the entry status after recovery and the comprehensive interface response of 10,000 nodes. Their main difference lies in the judgment method of the subsequent stage.

[0228] Group F identified the interface durability transition stage based on the change in the amount of multi-feature irreversible interface degradation with the cumulative number of cycles, through the development rate, stable degradation benchmark, and continuous deviation relationship. F-01, F-02, and F-03 determined the number of interface durability transition cycles at 13,000, 14,000, and 13,000 cycles, respectively.

[0229] Group C2 was judged solely based on whether the stiffness decrease after recovery reached a fixed 8%. C2-01, C2-02, and C2-03 reached the single stiffness significant degradation criterion at 16,000, 17,000, and 16,000 cycles, respectively. The test results also showed that the interface durability transition in Group F was concentrated between 13,000 and 14,000 cycles, while the node corresponding to the single stiffness criterion in Group C2 was located between 16,000 and 17,000 cycles.

[0230] Meanwhile, the number of macroscopic failure cycles for both Group F and Group C2 was concentrated around 19,000. Therefore, the earlier determined interface durability transition in Group F was not caused by earlier macroscopic failure in Group F samples, but rather by the fact that the comprehensive degradation information formed by diagnostic stiffness, hysteretic dissipation, and residual displacement could reflect the continuous changes in the interface state before the single stiffness reached a fixed decrease ratio.

[0231] Therefore, by further analyzing and synthesizing the development rate of irreversible interface degradation and its continuous deviation from the previous stable degradation benchmark, the stage in which the adhesive interface changes from relatively stable degradation to continuously accelerating degradation can be identified before macroscopic failure, without waiting for a single diagnostic indicator to reach a fixed decrease rate.

[0232] The results above show that, under the same durability loading conditions, the C1 group with a fixed recovery time of 300 s still has situations where the change in recovery response exceeds the recovery stability threshold at multiple durability nodes, thus requiring retesting. This also affects the overall degradation index and the corresponding stage change position obtained by the same fusion rule, as the recovery response has not yet been completed.

[0233] Group F dynamically determines the recovery termination state based on the actual recovery displacement changes, ensuring that each cumulative cycle node undergoes post-recovery diagnosis after meeting the same recovery stability conditions. This helps reduce the impact of changes in the recovery timescale at different durability stages on the comparability of test results.

[0234] In groups F and C2, which both adopted the dynamic recovery termination method, the recovery response and comprehensive degradation index of the two groups after 10,000 cycles were generally similar. However, after group F adopted the continuous criterion of multi-feature irreversible interface degradation development rate, the interface durability transition stage was identified at 13,000 to 14,000 cycles. Group C2, which adopted the single stiffness fixed threshold criterion, reached the significant degradation node at 16,000 to 17,000 cycles.

[0235] Therefore, this invention, through segmented cyclic durability loading, dynamic recovery termination determination based on recovery response, post-recovery condition diagnosis, multi-dimensional interface response fusion, and continuous change analysis of irreversible interface degradation rate, can form an irreversible interface degradation process with a clear cumulative cycle number coordinate, and determine the interface durability transition stage from stable degradation to continuously accelerating degradation of the adhesive interface before final macroscopic failure.

[0236] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for testing the interface durability of adhesive materials, characterized in that, include: S1: Apply a preset diagnostic micro-cyclic load to the bonding interface of the adhesive material to be tested, obtain initial diagnostic response data, and determine the initial interface response benchmark based on the initial diagnostic response data; S2: Perform segmented cyclic durability loading consisting of multiple durability loading segments on the bonding interface. Record the corresponding cumulative number of cycles at the end of each durability loading segment. After completing steps S3 and S4 corresponding to the current durability loading segment, proceed to the next durability loading segment. S3: After each durability loading segment ends, perform unloading recovery on the bonding interface, obtain the interface response data of the recovery stage, and determine the recovery termination state based on the change of the interface response data of the recovery stage with the recovery time. S4: After reaching the recovery termination state, apply the preset diagnostic micro-circulation load again, obtain the post-recovery diagnostic response data, and determine the irreversible interface degradation amount corresponding to each durability loading segment based on the difference between the post-recovery diagnostic response data and the initial interface response benchmark. S5: Based on the irreversible interface degradation amount and cumulative number of cycles corresponding to each durability loading segment, determine the relationship between the irreversible interface degradation amount and the cumulative number of cycles, and determine the interface durability transition stage based on the relationship. S6: Generate the interface durability test result of the adhesive material to be tested based on the irreversible interface degradation amount, the change relationship and the interface durability transition stage corresponding to each durability loading segment.

2. The method for testing the interface durability of adhesive materials as described in claim 1, characterized in that, Step S1 specifically includes: Before segmented cyclic durability loading, the preset diagnostic micro-cyclic load is applied to the adhesive interface according to the preset diagnostic load amplitude, preset diagnostic loading frequency, preset diagnostic load waveform and preset diagnostic cycle number. The peak load of the preset diagnostic micro-cyclic load is lower than the predetermined interface damage initiation load. Obtain load data and displacement data under the preset diagnostic micro-circulation load, determine diagnostic stiffness, hysteresis dissipation characteristics and residual displacement characteristics based on the load data and displacement data, and use the diagnostic stiffness, hysteresis dissipation characteristics and residual displacement characteristics as the initial diagnostic response data; The initial diagnostic stiffness characteristic value, the initial hysteresis dissipation characteristic value, and the initial residual displacement characteristic value are determined based on the diagnostic stiffness, the hysteresis dissipation characteristic value, and the initial residual displacement characteristic value, respectively, and the initial interface response benchmark is formed by the initial diagnostic stiffness characteristic value, the initial hysteresis dissipation characteristic value, and the initial residual displacement characteristic value.

3. The method for testing the interface durability of adhesive materials as described in claim 2, characterized in that, Step S2 specifically includes: The bonding interface is subjected to cyclic durability loading according to a preset durability load amplitude, a preset durability loading frequency, and a preset durability load waveform, wherein the preset durability load amplitude is greater than the preset diagnostic load amplitude. The cyclic durability loading process is divided into multiple durability loading segments that are executed sequentially. The current durability loading segment ends when the segment termination condition corresponding to each durability loading segment is met. Record the total number of cycles completed from the start of the cyclic durability loading to the end of each durability loading segment, and determine the total number of cycles as the cumulative number of cycles for the corresponding durability loading segment.

4. The method for testing the interface durability of adhesive materials as described in claim 1, characterized in that, Step S3 specifically includes: After each durability loading segment is completed, the cyclic durability load applied to the bonding interface is unloaded to a preset recovery load and maintained. The load level corresponding to the preset recovery load is lower than the load peak value of the preset diagnostic micro-cyclic load. According to the preset recovery detection interval, the recovery stage interface response data corresponding to multiple recovery detection times are obtained. The recovery stage interface response data includes recovery displacement data. The recovery response change amount corresponding to each recovery detection interval is determined according to the change between the recovery displacement data corresponding to adjacent recovery detection times. When the change in the recovery response corresponding to a consecutive preset number of recovery detection intervals is not greater than a preset recovery stability threshold, it is determined that the bonding interface has reached the recovery termination state.

5. The method for testing the interface durability of adhesive materials as described in claim 2, characterized in that, Step S4 specifically includes: After the bonding interface reaches the recovery termination state, the preset diagnostic micro-circulation load is applied to the bonding interface again according to the preset diagnostic load amplitude, the preset diagnostic loading frequency, the preset diagnostic load waveform, and the preset diagnostic cycle number, and the recovery load data and recovery displacement data are obtained during the operation of the preset diagnostic micro-circulation load. Based on the recovered load data and the recovered displacement data, the recovered diagnostic stiffness, recovered hysteresis dissipation characteristics, and recovered residual displacement characteristics are determined according to the feature extraction method consistent with step S1, and the recovered diagnostic response data is composed of the recovered diagnostic stiffness, the recovered hysteresis dissipation characteristics, and the recovered residual displacement characteristics.

6. The method for testing the interface durability of adhesive materials as described in claim 5, characterized in that, Step S4 also includes: The stiffness degradation characterization value is determined based on the difference between the recovered diagnostic stiffness and the initial diagnostic stiffness characteristic value; the dissipation degradation characterization value is determined based on the difference between the recovered hysteretic dissipation characteristic and the initial hysteretic dissipation characteristic value; and the residual displacement degradation characterization value is determined based on the difference between the recovered residual displacement characteristic and the initial residual displacement characteristic value. According to the preset feature scale corresponding to each degradation characterization value, the stiffness degradation characterization value, the dissipation degradation characterization value, and the residual displacement degradation characterization value are subjected to scale unification processing, and according to the preset degradation direction corresponding to each response feature, the direction is unified processing to obtain stiffness degradation characterization value, dissipation degradation characterization value, and residual displacement degradation characterization value. The stiffness degradation characteristic value, the dissipation degradation characteristic value, and the residual displacement degradation characteristic value are weighted and fused according to a preset fusion weight to obtain the irreversible interface degradation amount of the corresponding durability loading segment.

7. The method for testing the interface durability of adhesive materials as described in claim 1, characterized in that, Step S5 specifically includes: Obtain the irreversible interface degradation amount and the cumulative number of cycles corresponding to each durability loading segment, and construct a degradation data sequence according to the order of the cumulative number of cycles; The irreversible interface degradation rate between adjacent durability loading segments is determined based on the difference between the irreversible interface degradation amount between adjacent durability loading segments and the difference between the cumulative number of cycles in the degradation data sequence. The relationship between the amount of irreversible interface degradation and the cumulative number of cycles is determined based on the degradation data sequence, and the degree of change of the relationship between adjacent cumulative number of cycles is characterized by the irreversible interface degradation development rate between each adjacent durability loading segment.

8. The method for testing the interface durability of adhesive materials as described in claim 7, characterized in that, Step S5 also includes: A stable degradation interval is determined based on the change in the irreversible interface degradation rate between multiple consecutive adjacent durability loading segments. When the change in the first preset number of consecutive segments is not greater than a preset stable change threshold, the corresponding consecutive durability loading interval is determined as the stable degradation interval. A baseline degradation rate is determined based on the irreversible interface degradation rate within the stable degradation interval. According to the order of cumulative cycle count, the irreversible interface degradation rate between each adjacent durability loading segment after the stable degradation interval is compared with the baseline degradation rate, and the corresponding degradation deviation is determined based on the difference between the two. When the degradation deviation of a second consecutive preset number of such deviations is not less than a preset turning point deviation threshold, and the corresponding irreversible interface degradation rate shows a continuous increasing trend, the next durability loading segment corresponding to the first irreversible interface degradation rate among the second consecutive preset number of such irreversible interface degradation rates is determined as the interface durability turning point stage.

9. The method for testing the interface durability of adhesive materials as described in claim 8, characterized in that, Step S6 specifically includes: The irreversible degradation process of the adhesive interface is determined based on the amount of irreversible interface degradation corresponding to each durability loading segment and the relationship between the amount of irreversible interface degradation and the cumulative number of cycles. The durability transition cycle number is determined based on the cumulative number of cycles of the durability loading segment corresponding to the interface durability transition stage. The irreversible degradation process corresponding to the durability transition cycle number is determined as the pre-transition degradation process, and the irreversible degradation process corresponding to the durability transition cycle number is determined as the post-transition degradation process. The interface durability test results of the adhesive material to be tested are generated based on the degradation process before the transition, the degradation process after the transition, and the number of durability transition cycles.

10. A system for testing the interface durability of adhesive materials, used to implement the method for testing the interface durability of adhesive materials as described in any one of claims 1 to 9, characterized in that, include: Initial interface response benchmark determination module: Apply a preset diagnostic micro-cyclic load to the bonding interface of the adhesive material to be tested, acquire initial diagnostic response data, and determine the initial interface response benchmark based on the initial diagnostic response data; Segmented Cyclic Durability Loading Module: Performs segmented cyclic durability loading on the bonding interface, consisting of multiple durability loading segments. Records the corresponding cumulative number of cycles at the end of each durability loading segment, and enters the next durability loading segment after completing steps S3 and S4 corresponding to the current durability loading segment. Recovery Termination State Determination Module: After each durability loading segment ends, unloading recovery is performed on the bonding interface, the interface response data of the recovery stage is obtained, and the recovery termination state is determined based on the change of the interface response data of the recovery stage with the recovery time. Irreversible interface degradation determination module: After reaching the recovery termination state, the preset diagnostic micro-cycle load is applied again to obtain the post-recovery diagnostic response data, and the irreversible interface degradation corresponding to each durability loading segment is determined based on the difference between the post-recovery diagnostic response data and the initial interface response benchmark. Interface durability transition stage determination module: Based on the irreversible interface degradation amount and cumulative cycle count corresponding to each durability loading segment, determine the relationship between the irreversible interface degradation amount and the cumulative cycle count, and determine the interface durability transition stage based on the relationship. Interface durability test result generation module: Based on the irreversible interface degradation amount, the change relationship, and the interface durability transition stage corresponding to each durability loading segment, the interface durability test result of the adhesive material to be tested is generated.

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