Quantitative monitoring method for damage accumulation of ceramic matrix composites under step loading

Abstract

This application provides a quantitative monitoring method for damage accumulation in ceramic matrix composites under stepped cyclic loading, relating to the field of material damage monitoring technology. This method involves re-measuring the acoustic wave propagation velocity within the test sample using acoustic emission sensors placed on the sample at each load level. The method then calculates the acoustic wave propagation velocity degradation rate corresponding to that load level based on the initial acoustic wave propagation velocity, and determines the damage accumulation variable of the test sample after applying that load level based on the acoustic wave propagation velocity degradation rate. This allows for the determination of the damage accumulation variable evolution curve of the test sample with load, achieving a quantitative characterization of the continuous evolution process of damage accumulation during stepped cyclic loading tests.

Description

Technical Field

[0001] This application relates to the field of material damage monitoring technology, and in particular to a quantitative monitoring method for the accumulation of step cyclic loading damage in ceramic matrix composites. Background Technology

[0002] Ceramic matrix composites (CMCs) have become core candidate materials for hot-end components of high-end equipment due to their high temperature resistance, high specific strength, high specific modulus, and excellent creep resistance. During service, they are subjected to long-term cyclic loading, leading to progressive damage accumulation such as matrix cracking, interface debonding, and fiber breakage, ultimately causing component failure. Therefore, accurate monitoring of their damage evolution is crucial for ensuring service safety.

[0003] Step cyclic loading tests are a core experimental method for studying the cumulative evolution of damage in CMC materials. Currently, damage monitoring for this test mainly relies on acoustic emission technology, supplemented by strain measurement and full-field strain observation. The core limitation of existing monitoring methods is that damage monitoring remains at the qualitative level. It can only preliminarily judge the degree of damage activity based on the basic characteristics of acoustic emission signals, and cannot achieve quantitative characterization of damage. The monitoring accuracy is insufficient, which is the core technical bottleneck in the current field of CMC damage monitoring. Summary of the Invention

[0004] The purpose of this application is to provide a quantitative monitoring method for the accumulation of damage in ceramic matrix composites under stepped cyclic loading, so as to achieve quantitative analysis of the damage evolution of ceramic matrix composites during stepped cyclic loading tests. The specific technical solution is as follows: This application provides a quantitative monitoring method for the accumulation of stepped cyclic loading damage in ceramic matrix composites, comprising: sequentially performing load loading operations on a test sample according to a preset number of different load levels to conduct a stepped cyclic loading test on the test sample; during the load loading operation according to each load level, performing calibration of the sound propagation velocity based on an acoustic emission sensor assembly arranged on the test sample to determine the sound wave propagation velocity inside the test sample corresponding to each load level; for each load level applied to the test sample, determining the sound wave propagation velocity inside the test sample corresponding to that load level. The initial acoustic wave propagation velocity is determined in advance, and the acoustic wave propagation velocity degradation rate corresponding to the load level is determined. The initial acoustic wave propagation velocity is the acoustic wave propagation velocity inside the test sample measured by the acoustic emission sensor assembly under the initial undamaged reference state of the test sample. For each load level applied to the test sample, the cumulative damage variable of the test sample after applying the load level is determined based on the acoustic wave propagation velocity degradation rate corresponding to the load level. Based on the cumulative damage variable of the test sample corresponding to each load level after applying the load level, the evolution curve of the cumulative damage variable of the test sample with load is determined.

[0005] Optionally, during the load loading operation according to a load level, the calibration of the sound propagation velocity is performed as follows: within the calibration window period of the current load loading operation, one or more lead-breaking excitations are performed sequentially at a preset lead-breaking excitation point; the calibration window period covers the load holding phase, the first time period before load holding, and the second time period after unloading during the load loading operation; based on the time difference and distance difference between the stress wave generated when one lead-breaking excitation arrives at different acoustic emission sensors on the test sample, the instantaneous sound wave propagation velocity corresponding to one lead-breaking excitation is determined; based on the instantaneous sound wave propagation velocity corresponding to one or more lead-breaking excitations, the sound wave propagation velocity inside the test sample corresponding to this load level is determined.

[0006] Optionally, for each level of load applied to the test sample, the cumulative damage variable of the test sample after applying that level of load is determined based on the acoustic velocity degradation rate corresponding to that level of load. This includes: for each level of load applied to the test sample, substituting the acoustic velocity degradation rate corresponding to that level of load into the basic damage characterization formula to obtain the cumulative damage variable of the test sample after applying that level of load; the basic damage characterization formula is expressed as follows:

[0007] in, This indicates that the first test sample is loaded. The cumulative damage variable of the test sample after each level of loading. Indicates the first The degradation rate of sound wave propagation velocity corresponding to each load level.

[0008] Optionally, after determining the evolution curve of the damage accumulation variable of the test sample with load, the above method further includes: analyzing the rate of change of the damage accumulation variable with load based on the evolution curve to determine the critical load threshold that leads to accelerated evolution of damage within the test sample.

[0009] Optionally, the above method further includes: acquiring acoustic emission events collected by the acoustic emission sensor assembly during the step cyclic loading test; extracting the time-domain and frequency-domain feature parameters of each acoustic emission event, and constructing multi-dimensional features of each acoustic emission event based on the time-domain and frequency-domain feature parameters; clustering each acoustic emission event according to a preset unsupervised clustering algorithm based on the constructed multi-dimensional features to obtain multiple acoustic emission event clusters; and determining the damage mode corresponding to each acoustic emission event cluster based on the damage mechanism of each damage mode of the ceramic matrix composite material, using the time-domain and frequency-domain feature parameters of the acoustic emission events within the acoustic emission event cluster as a basis.

[0010] Optionally, the above method further includes: acquiring multi-source monitoring data collected for the test sample during the step cyclic loading test; the multi-source monitoring data includes any one or more of the following: load data applied to the test sample, mechanical response curves at preset monitoring positions on the test sample, and full-field strain images of the test sample; the aforementioned determination of the damage mode corresponding to the acoustic emission event cluster based on the time-domain and frequency-domain characteristic parameters of the acoustic emission events within the acoustic emission event cluster, according to the damage mechanism of each damage mode of the ceramic matrix composite material, including: determining the damage mode corresponding to the acoustic emission event cluster based on the time-domain and frequency-domain characteristic parameters of the acoustic emission events within the acoustic emission event cluster, combined with the multi-source monitoring data corresponding to the acoustic emission events within the acoustic emission event cluster, according to the damage mechanism of each damage mode.

[0011] Optionally, after determining the damage mode corresponding to each acoustic emission event cluster, the above method further includes: establishing a correspondence between multidimensional features and damage modes based on the damage mode corresponding to each acoustic emission event cluster and the multidimensional features of each acoustic emission event within each acoustic emission event cluster; the correspondence is used to determine the corresponding damage mode for the acoustic emission events obtained from testing the remaining test samples.

[0012] Optionally, after determining the damage mode corresponding to each acoustic emission event cluster, the above method further includes: determining the proportion of acoustic emission events of each damage mode in each load loading stage based on the damage mode corresponding to each acoustic emission event cluster and the load loading stage corresponding to each acoustic emission event during the step cyclic loading test; wherein, each load loading stage includes the process of performing load loading operation according to one or more consecutive levels of load.

[0013] Optionally, the above method further includes: determining the rate of change of the cumulative damage variable of the test sample with load based on the evolution curve, and dividing the process of performing the step cyclic loading test into multiple damage evolution stages based on the rate of change; or, determining the damage mode that appears in the test sample during the process of performing load loading operation according to each load level based on the damage mode corresponding to each acoustic emission event cluster and the load level corresponding to each acoustic emission event during the step cyclic loading test; and dividing the process of performing the step cyclic loading test into multiple damage evolution stages based on the damage mode that appears in the test sample during the process of performing load loading operation according to each load level.

[0014] Optionally, the above method further includes: at the initial loading moment when the load loading operation is performed on the test sample based on the first level of load, the mechanical loading system, acoustic emission monitoring system, strain measurement system, and full-field strain measurement system are synchronously triggered by a pre-configured synchronous trigger controller, so that the mechanical loading system, acoustic emission monitoring system, strain measurement system, and full-field strain measurement system collect data on the test sample according to a unified time axis; wherein, the mechanical loading system is used to collect load data loaded on the test sample, the acoustic emission monitoring system includes an acoustic emission sensor component for collecting acoustic emission data within the test sample, the strain measurement system is used to collect strain data at preset monitoring positions on the test sample, and the full-field strain measurement system is used to collect full-field strain images of the test sample.

[0015] Beneficial effects of the embodiments in this application: This application recognizes that the accumulation and evolution of damage within CMC materials can disrupt the continuity of the acoustic propagation medium. Therefore, based on this principle, a quantitative analysis of damage accumulation is proposed using the attenuation of acoustic wave propagation velocity within CMC materials. A quantitative monitoring method for damage accumulation during stepped cyclic loading of ceramic matrix composites is designed accordingly. During stepped cyclic loading tests on the test sample using this method, the acoustic wave propagation velocity within the test sample is re-measured using acoustic emission sensors placed on the sample at each load level. The acoustic wave propagation velocity degradation rate corresponding to that load level is calculated based on the initial acoustic wave propagation velocity. Then, the damage accumulation variable of the test sample after applying that load level is determined based on the acoustic wave propagation velocity degradation rate. This allows for the determination of the damage accumulation variable evolution curve of the test sample with load, achieving a quantitative characterization of the continuous evolution of damage accumulation during stepped cyclic loading tests.

[0016] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0018] Figure 1 A schematic diagram of the test monitoring system provided in the embodiments of this application; Figure 2 A flowchart illustrating the quantitative monitoring method for step cyclic loading damage accumulation in ceramic matrix composites provided in this application embodiment; Figure 3 The curve showing the change of load over time on the test sample during the stepped cyclic loading test provided in this application embodiment; Figure 4 A schematic diagram of the evolution curve of the cumulative damage variable of the test sample as a function of load, provided in an embodiment of this application; Figure 5 A schematic diagram illustrating the proportion of acoustic emission events of different damage modes in different load loading stages, as provided in the embodiments of this application; Figure 6 This is a schematic diagram of a test monitoring process provided in an embodiment of this application. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0020] The typical workflow for step-cycle loading damage detection of CMC materials is as follows: An acoustic emission monitoring system and a mechanical loading system are set up; the acoustic emission system is calibrated once before the test; a graded step-cycle loading scheme is designed and implemented, with acoustic emission base signals and mechanical load data collected simultaneously during loading; the collected acoustic emission signals are subjected to simple filtering to extract the basic time-domain characteristics; combined with stress-strain curves, the active damage stage of the material is qualitatively determined, and damage modes are preliminarily classified; finally, based on the qualitative analysis results, a rough assessment of the material damage is given. The core shortcomings of this workflow are the lack of quantitative methods, asynchronous operation, inaccuracy, and standards. A standardized monitoring system has not been formed, significantly reducing the effectiveness of monitoring and failing to meet the needs of damage mechanism research and engineering applications.

[0021] Meanwhile, in engineering and research practice, the above-mentioned typical process also reveals the following key shortcomings: (1) Damage accumulation cannot be quantified: Existing methods can only qualitatively determine the degree of damage activity, and cannot establish a quantifiable correspondence between damage accumulation and loading process. They cannot accurately assess the degree of internal damage of the material after each step of cyclic loading, and cannot meet the precise needs of damage mechanism research and engineering applications.

[0022] (2) The timing of multiple systems is not synchronized: There is no unified time axis synchronization control between acoustic emission system, mechanical loading system, strain measurement system, etc., which makes it impossible to accurately correspond acoustic emission damage events with mechanical response and strain distribution, making it difficult to achieve spatiotemporal location and mechanism analysis of damage, resulting in low monitoring accuracy.

[0023] (3) The system calibration is not standardized: only a single acoustic emission system calibration is carried out before the test, without considering the impact of material damage accumulation on the sound wave propagation speed. As a result, the damage location accuracy continues to decrease with the loading process, and cannot provide reliable data support for damage quantification.

[0024] (4) Low accuracy of damage pattern recognition: The damage pattern is simply divided by a single time-domain feature parameter without combining multi-dimensional features and algorithms to achieve accurate classification. It is impossible to distinguish the typical damage evolution law of different loading stages and it is difficult to reveal the damage mechanism.

[0025] (5) The test process is not standardized: there are no unified standards for the step cyclic loading scheme, monitoring parameter settings, and data processing methods. The test results have poor repeatability, making it difficult to adapt to the needs of engineering testing and application, and thus unable to promote the technology.

[0026] In view of the above, this application provides a method for quantitative monitoring of step cyclic loading damage accumulation in ceramic matrix composites, to solve at least one of the technical problems listed above. The specific details are as follows: The quantitative monitoring method provided in this application can be specifically applied to a test monitoring system built for CMC materials. For ease of understanding, Figure 1 One possible example of a test monitoring system is provided, which includes: a mechanical loading system, an acoustic emission monitoring system, a local strain measurement system, and a full-field strain measurement system.

[0027] The mechanical loading system includes a load information input device and a mechanical loading testing machine. The mechanical loading testing machine is equipped with a CMC material sample to be tested. It receives load information from the load information input device and applies load to the sample based on the received load information to perform a stepped cyclic loading test. The load information input device inputs load information to the mechanical loading testing machine and performs real-time load acquisition and processing during the stepped cyclic loading test, recording the load variation over time (load data) and generating mechanical load-displacement data.

[0028] The acoustic emission monitoring system includes an acoustic emission sensor assembly, a preamplifier, and an AE (Acoustic Emission) signal processing device. The acoustic emission sensor assembly comprises multiple acoustic emission sensors arranged on the test sample. This assembly is used to acquire acoustic signals during the execution of the step cyclic loading test, obtaining full waveform data of acoustic emission from the test sample. The acquired full waveform data is then processed by the preamplifier and processed by the AE signal processing device. The AE signal processing device processes the full waveform data of acoustic emission from the test sample to identify acoustic emission events occurring within the test sample.

[0029] The local strain measurement system includes strain sensors positioned at preset monitoring locations on the test specimen. These sensors acquire strain data at these locations during the step cyclic loading test. By aligning the strain data with the load data recorded by the mechanical loading system on the time axis, a relationship between the strain data and the load applied to the test specimen can be established, thus generating a mechanical response curve of the test specimen at the preset monitoring location. The full-field strain measurement system acquires full-field strain images of the test specimen during the step cyclic loading test.

[0030] In practical applications, based on the aforementioned test monitoring system, multi-source data acquisition and processing can be performed on the data collected by the mechanical loading system, acoustic emission monitoring system, local strain measurement system, and full-field strain measurement system to achieve damage visualization and damage identification of the internal damage of the test sample.

[0031] The following describes in detail the quantitative monitoring method for step cyclic loading damage accumulation in ceramic matrix composites provided in the embodiments of this application. (See also...) Figure 2 The method specifically includes the following steps: Step S201: Perform load loading operations on the test sample in sequence according to multiple preset load levels to conduct a step cyclic loading test on the test sample.

[0032] In this embodiment, multiple load levels are pre-set for the test sample, with the magnitude of each load level increasing sequentially. For example, a maximum load can be set based on the estimated tensile strength of the CMC material used in the test sample, and then multiple load levels can be set proportionally based on this maximum load. For instance, 5% of the maximum load can be set as the first load level, 10% as the second load level, 15% as the third load level, and so on.

[0033] Figure 3 This diagram illustrates the variation of the load applied to the test sample over time during a stepped cyclic loading test conducted according to preset load levels. In the stepped cyclic loading test, the load on the test sample is first increased to the first load level, held for a certain time, and then unloaded to zero. Then, the load is increased to the second load level, held for a certain time, and then unloaded to zero. Next, the load is increased to the third load level, held for a certain time, and then unloaded to zero. This process is repeated, increasing the load level and holding the load until the test sample exhibits obvious failure characteristics.

[0034] Step S202: During the load loading operation at each load level, the sound propagation speed is calibrated based on the acoustic emission sensor assembly arranged on the test sample to determine the sound wave propagation speed inside the test sample corresponding to each load level.

[0035] Specifically, during the execution of the step cyclic loading test, as damage accumulates inside the test sample, the propagation speed of sound waves inside the sample changes. Considering this characteristic, this application innovatively proposes that during each load loading operation, the sound wave propagation speed be calibrated at the same preset location on the test sample to determine the sound wave propagation speed within the sample under the current damage state, and to quantitatively analyze the damage accumulation within the test sample based on the measured sound wave propagation speed.

[0036] In one example, during the load loading operation on the test sample according to the i-th load level, the sound wave propagation velocity inside the test sample corresponding to the i-th load level can be determined based on the following steps A1-A3: Step A1: During the calibration window period of the load loading operation according to the i-th level of load, N pencil lead break (PLB) stimuli are performed sequentially at the preset lead break stimuli point.

[0037] In conjunction with the preceding text regarding Figure 3 The explanation is easy to understand. The process of performing a load loading operation according to the i-th load level includes: a loading phase from zero load to the i-th load level, a load holding phase, and an unloading phase from the i-th load level to zero load. In the embodiments of this application, the calibration window period set during the load loading process according to the i-th load level can specifically cover the load holding phase, a certain period before load holding (first period), and a certain period after unloading begins (second period).

[0038] Figure 3 The document provides an example of calibration windows, specifically illustrating calibration window 1 during a load loading operation performed under a first-level load, calibration window 2 during a load loading operation performed under a second-level load, and calibration window 3 during a load loading operation performed under a third-level load.

[0039] The number of lead-breaking excitations N implemented within a calibration window period can be set to a natural number greater than or equal to 1 according to actual needs. This application embodiment does not limit its specific value.

[0040] Step A2: Based on the implementation of the kth time ( The time difference and distance difference between the stress wave generated during lead breakage excitation and the arrival of different acoustic emission sensors on the test sample are used to determine the instantaneous sound wave propagation speed corresponding to the kth lead breakage excitation.

[0041] For ease of explanation, the two different acoustic emission sensors placed on the test sample are denoted as sensor A and sensor B, respectively. After the k-th lead-breaking excitation is performed within the calibration window period in step A1, the instantaneous sound wave propagation velocity corresponding to the k-th lead-breaking excitation can be calculated based on the following formula. :

[0042] in, The difference between the absolute distances of sound wave propagation from the preset lead-breaking excitation point to sensor A and sensor B is given. The time difference between the arrival time of the stress wave generated by the kth lead breakage excitation at sensor A and sensor B, respectively.

[0043] Step A3: Based on the instantaneous acoustic wave propagation velocity corresponding to each of the N lead-breaking excitations in Step A1, determine the acoustic wave propagation velocity inside the test sample corresponding to the i-th load level. .

[0044] In this embodiment, the instantaneous sound wave propagation velocity corresponding to each of the N lead-breaking excitations is not determined. The implementation method can be specifically defined and chosen according to actual needs. For example, it can be determined by averaging the instantaneous sound wave propagation velocities corresponding to each of the N lead-breaking excitations. .

[0045] In one example, considering the randomness of the evolution of the local microstructure of the material and the influence of environmental noise, the set of instantaneous sound wave propagation velocities obtained in steps A1-A2 is used. The data inevitably contains outlier fluctuations. Therefore, to obtain stable acoustic characteristics that accurately characterize the overall damage state corresponding to the i-th load level, the Interquartile Range (IQR) method can be introduced in step A3 for data cleaning to determine... In this case, step A3 can be implemented based on steps A31-A33 as follows: Step A31: Calculate the set of instantaneous sound wave propagation velocities First quartile and the third and fourth quartiles Find the interquartile range .

[0046] Step A32: Set the valid data range as follows Remove the set of instantaneous sound wave propagation speeds Abnormal instantaneous sound wave propagation speeds outside this valid data range will affect the remaining... indivual( The instantaneous sound wave propagation speed is taken as the effective instantaneous sound wave propagation speed.

[0047] Step A33: Calculation The arithmetic mean of the effective instantaneous sound wave propagation velocities is used as the sound wave propagation velocity inside the test sample corresponding to the i-th load level. , Specifically, it can be represented as follows:

[0048] Step S203: For each level of load applied to the test sample, based on the sound wave propagation velocity inside the test sample corresponding to that level of load and the pre-determined initial sound wave propagation velocity, determine the sound wave propagation velocity degradation rate corresponding to that level of load.

[0049] The initial acoustic wave propagation velocity is defined as the acoustic wave propagation velocity inside the test sample, measured by the acoustic emission sensor assembly, under the initial non-destructive baseline state. In other words, it is the acoustic wave propagation velocity inside the test sample, measured by the acoustic emission sensor assembly, before any load is applied.

[0050] For example, before performing the step cyclic loading test on the test sample according to step S201 described above, the initial acoustic wave propagation velocity inside the test sample under the initial undamaged reference state can be determined as follows: one or more lead-breaking excitations are performed sequentially at a preset lead-breaking excitation point; for each lead-breaking excitation in the one or more lead-breaking excitations, the instantaneous acoustic wave propagation velocity corresponding to the lead-breaking excitation is determined based on the difference in the absolute acoustic wave propagation distance from the preset lead-breaking excitation point to sensor A and sensor B on the test sample, and the time difference between the stress wave generated by the lead-breaking excitation and sensor A and sensor B respectively; based on the instantaneous acoustic wave propagation velocity corresponding to each lead-breaking excitation in the one or more lead-breaking excitations, the initial acoustic propagation velocity inside the test sample is determined.

[0051] Specifically, as the step cyclic loading test proceeds, microscopic damage such as matrix cracking and fiber breakage within the test sample accumulates, disrupting the continuity of the acoustic wave propagation medium and macroscopically manifesting as a decrease in acoustic wave propagation velocity. Considering this, this embodiment uses the initial acoustic wave propagation velocity as a benchmark and calculates the acoustic wave propagation velocity degradation rate of the test sample during the loading process to assess the damage accumulation.

[0052] Let the acoustic wave propagation velocity inside the test sample corresponding to the i-th load level be denoted as . The initial speed of sound wave propagation is denoted as . The degradation rate of sound wave propagation velocity corresponding to the load of the i-th level is... It can be calculated using the following formula:

[0053] In this embodiment of the application, the range of the sound wave propagation speed degradation rate is: , This is used to quantify the degree of degradation in acoustic conductivity of a test sample after the i-th level of load is applied, compared to its conductivity in the initial undamaged baseline state.

[0054] Step S204: For each level of load applied to the test sample, based on the acoustic propagation velocity degradation rate corresponding to that level of load, determine the cumulative damage variable of the test sample after applying that level of load.

[0055] Specifically, the basic formula for damage characterization based on the sound wave propagation velocity degradation rate can be derived in advance, and in step S204, the sound wave propagation velocity degradation rate corresponding to the i-th level of load can be used as the basis for the determination. Substituting into the basic formula for damage characterization, we can calculate the loss variable of the test sample after applying the i-th level of load. .

[0056] In one example, the basic formula for damage characterization can be derived based on the following process: Based on the Lemaitre equivalent effect hypothesis, the loss variable of the test sample after applying the i-th level of load is... It can be represented as follows:

[0057] in, To determine the elastic modulus of the test sample after applying the i-th level of load, This is the elastic modulus of the test sample under the initial undamaged reference state.

[0058] According to the one-dimensional elastic stress wave theory of solid media, the longitudinal wave propagation velocity within the material... Elastic modulus The relationship between material density and Therefore, the above... This can be further expressed as follows:

[0059] in, To determine the density of the test sample after applying the i-th level of load, This represents the density of the test sample under the initial undamaged baseline state.

[0060] During the stepped cyclic loading test of CMC material under tensile load, the change in its macroscopic density is negligible (i.e., Therefore, the attenuation ratio of the elastic modulus can be determined. The equivalent mapping is the attenuation ratio of the square of the sound wave propagation speed. Thus, the above can be Further details are as follows:

[0061] Then the relation Substituting into the above equation and simplifying, we can obtain the basic formula for damage characterization based on the degradation rate of sound wave propagation velocity:

[0062] In this embodiment of the application, the range of values ​​for the damage accumulation variable is: , This is used to quantitatively represent the cumulative damage within the test specimen after applying the i-th level of load. As the step cyclic loading test proceeds, the cumulative damage variable of the test specimen gradually progresses from 0 (intact) to 1 (complete loss of load-bearing capacity).

[0063] Step S205: Based on the cumulative damage variable of the test sample after each level of load is applied, determine the evolution curve of the cumulative damage variable of the test sample with load.

[0064] Figure 4 An example of the evolution curve of damage accumulation variable with load is provided. Specifically, the evolution curve is plotted with load on the horizontal axis and damage accumulation variable on the vertical axis. The horizontal axis of each data point represents the magnitude of a load level, and the vertical axis represents the damage accumulation variable of the test sample after applying that load level. It can be seen that by determining the evolution curve of damage accumulation variable with load, the cumulative evolution process of damage inside the test sample as the load increases can be presented more clearly.

[0065] In one possible implementation of this application, after obtaining the evolution curve of the damage accumulation variable with load, the critical load threshold that leads to accelerated evolution of damage within the test sample can be further determined based on the evolution curve.

[0066] Figure 4An example of a critical load threshold is shown. The physical meaning of the critical load threshold is: after applying this load value to the test sample, the damage within the test sample begins to evolve at an accelerated pace; and the critical load threshold is reflected in the curve shape as the load value at the point where the slope of the curve changes from gentle to steep.

[0067] In practical applications, various methods can be adopted to determine the critical load threshold from the evolution curve according to actual needs. This application does not explicitly limit the specific implementation method. For example, the load value at the point where the slope of the evolution curve increases significantly can be visually determined as the critical load threshold, or the second derivative of the damage accumulation variable with load can be calculated, and the load value at the point where the second derivative is zero can be used as the critical load threshold.

[0068] In practical applications, the evolution curve of the cumulative damage variable with load and the critical load threshold determined for the test sample of CMC material can serve as a benchmark for setting allowable damage thresholds for CMC materials, and can provide accurate and reliable data support for the relevant design and health monitoring of CMC components.

[0069] As can be seen from the above, this application, recognizing that the accumulation and evolution of damage within CMC materials can disrupt the continuity of the acoustic propagation medium, proposes a quantitative analysis of damage accumulation based on the attenuation of acoustic wave propagation velocity within the CMC material. Based on this, a quantitative monitoring method for damage accumulation in ceramic matrix composites under step cyclic loading is designed. During the step cyclic loading test on the test sample using this quantitative monitoring method, the acoustic wave propagation velocity within the test sample is re-measured using acoustic emission sensors placed on the sample at each load level. The acoustic wave propagation velocity degradation rate corresponding to that load level is calculated based on the initial acoustic wave propagation velocity. Then, the damage accumulation variable of the test sample after applying that load level is determined based on the acoustic wave propagation velocity degradation rate. This allows for the determination of the damage accumulation variable evolution curve of the test sample with load, achieving a quantitative characterization of the continuous evolution process of damage accumulation during the step cyclic loading test.

[0070] Furthermore, in research on CMC materials, damage within the CMC material is typically classified into various damage modes based on the damage generation mechanism, such as matrix cracking, interface debonding, fiber pull-out, and fiber breakage. Considering this, in one embodiment of this application, based on the quantitative analysis of the accumulated damage within the test sample according to steps S201-S05 above, the damage modes within the test sample can be further identified. For example, the identification of damage modes within the test sample can be achieved based on the following steps B1-B4: Step B1: Acquire the acoustic emission events collected by the acoustic emission sensor assembly during the step cyclic loading test.

[0071] Generally speaking, acoustic emission sensor components can acquire full acoustic emission waveform data throughout the entire step cyclic loading test cycle. In addition to acoustic emission signals released by actual damage events within the test sample, these data may also include other invalid noise.

[0072] In practical applications, filtering and denoising techniques can be used to preprocess the full acoustic emission waveform data to extract effective acoustic emission events that characterize the actual damage evolution process within the test sample. For example, a noise threshold can be set, and signals below this threshold in the full acoustic emission waveform data can be filtered out to separate independent acoustic emission events from the full acoustic emission waveform data.

[0073] Step B2: Extract the time-domain and frequency-domain feature parameters of each acoustic emission event, and construct multidimensional features of each acoustic emission event based on the time-domain and frequency-domain feature parameters.

[0074] This application does not limit the specific content of the time-domain and frequency-domain feature parameters extracted from acoustic emission events, and they can be selected according to actual needs. For example, time-domain feature parameters may include the amplitude and energy of the acoustic emission event, while frequency-domain feature parameters may include the peak frequency and bandwidth of the acoustic emission event.

[0075] In one example, for an acoustic emission event, the time-domain feature parameters and frequency-domain feature parameters of each dimension of the acoustic emission event can be standardized to eliminate the influence of different dimensions; and the standardized time-domain feature parameters and frequency-domain feature parameters are then concatenated to form the multidimensional features of the acoustic emission event.

[0076] Step B3: Based on the constructed multidimensional features, cluster each acoustic emission event using a preset unsupervised clustering algorithm to obtain multiple acoustic emission event clusters.

[0077] Specifically, the unsupervised clustering algorithm takes the multidimensional features of acoustic emission events as input data. By analyzing the features of the data itself, similar data can be classified into one category, thereby dividing the acoustic emission events obtained in step B1 into multiple acoustic emission event clusters.

[0078] This application does not specifically limit the type of unsupervised clustering algorithm used, and the algorithm can be selected according to actual needs. For example, K-Means (an unsupervised clustering algorithm) or DBSCAN (an unsupervised clustering algorithm) can be used to cluster various acoustic emission events.

[0079] Step B4: For each clustered acoustic emission event cluster, based on the multidimensional characteristics of the acoustic emission events within the cluster, and according to the damage mechanism of each damage mode of the ceramic matrix composite material, determine the damage mode corresponding to the acoustic emission event cluster.

[0080] Specifically, the various damage modes of CMC materials each possess different damage mechanisms, and these different damage mechanisms are manifested differently in the time-domain and frequency-domain characteristics of acoustic emission signals. For example, low-frequency, low-energy acoustic emission signals typically correspond to interface debonding damage modes; mid-to-high frequency, medium-energy acoustic emission signals typically correspond to matrix cracking damage modes; mid-to-low frequency, medium-energy acoustic emission signals typically correspond to fiber pull-out damage modes; and high-frequency, high-energy damage modes typically correspond to fiber breakage damage modes.

[0081] Therefore, in this embodiment, for a cluster of acoustic emission events, the damage mechanisms of various damage modes of CMC materials can be analyzed in the time and frequency domains based on their different manifestations, combined with practical experience, to determine the damage mode corresponding to the cluster. Once the damage mode corresponding to a cluster is determined, it can be assumed that the damage events represented by each acoustic emission event within the cluster belong to that damage mode.

[0082] In one example, during the identification of damage modes within the test specimen, in addition to using the time-frequency domain characteristics of acoustic emission events as the identification basis, multi-source monitoring data collected on the test specimen during the step cyclic loading test can also be used as the identification basis. Multi-source monitoring data can include any one or more of the following: load data applied to the test specimen, mechanical response curves at preset locations on the test specimen, and full-field strain images of the test specimen during the step cyclic loading test.

[0083] Specifically, the damage mechanisms of different damage modes may also manifest differently in the mechanical response curves and full-field strain images of the material, and some damage modes may be related to the loading conditions on the test sample (for example, matrix cracking damage mode is more likely to occur during the load holding process, while interface slip damage mode is more likely to occur during unloading). Therefore, given the multi-source monitoring data collected for the test sample, in step B4, the acoustic emission events and multi-source monitoring data can be aligned on the time axis to find the multi-source monitoring data corresponding to each acoustic emission event (the multi-source monitoring data corresponding to an acoustic emission event is the multi-source monitoring data collected for the test sample within the time of the occurrence of that acoustic emission event); then, for a clustered acoustic emission event cluster, the damage mode corresponding to the acoustic emission event cluster can be determined by analyzing the time-domain and frequency-domain characteristic parameters of each acoustic emission event within the cluster, as well as the multi-source monitoring data corresponding to each acoustic emission event within the cluster, based on the different manifestations of the damage mechanisms of various damage modes of CMC materials in the time-frequency domain, combined with practical experience.

[0084] In one example, after determining the damage mode corresponding to each cluster of acoustic emission events, a correspondence between the multidimensional features of acoustic reflection events and the damage mode can be established based on the damage mode corresponding to each acoustic emission event cluster and the multidimensional features of each acoustic emission event within each cluster. Therefore, when conducting step cyclic loading tests on different test samples, for acoustic emission events collected during the test, the damage mode corresponding to the multidimensional features of that acoustic emission event can be directly considered as the damage mode of that acoustic emission event.

[0085] For example, if the acoustic emission events are clustered using the K-Means algorithm in step B3, and the damage mode corresponding to a cluster of acoustic emission events is determined in step B4, the cluster center of that acoustic emission event cluster can be labeled as the damage mode, thus establishing the correspondence between multidimensional features and damage modes. Therefore, when conducting step cyclic loading tests on different test samples, for acoustic emission events collected during the test, the cluster center closest to the multidimensional features of that acoustic emission event can be found, and the damage mode corresponding to that cluster center can be considered the damage mode of that acoustic emission event.

[0086] In one embodiment of this application, after determining the damage modes corresponding to each cluster of acoustic emission events, the proportion of acoustic emission events of each damage mode in each load loading stage during the step cyclic loading test can be further determined based on the damage modes corresponding to each acoustic emission event cluster and the load loading stage corresponding to each acoustic emission event during the step cyclic loading test.

[0087] As mentioned earlier, multiple load levels are pre-set for the test sample. In this embodiment, several consecutive load levels can be grouped together, and the process of performing a load loading operation based on this group of loads can be considered as a load loading stage. For example, when the highest load level is set as α, a load loading stage can be performed based on a value of 5%. α-25% The process of applying load α is considered the first load application stage, based on a value of 30%. α-50% The process of applying load α is considered the second load application stage, based on a value of 55%. α-75% The process of performing load loading operation on load α is considered the third load loading stage, based on a value of 80%. α-100% The process of α performing load loading operation is regarded as the fourth load loading stage.

[0088] In this embodiment, acoustic emission events occurring in each load loading stage can be determined based on the time axis of the load data loaded on the test sample and the time axis of each acoustic emission event obtained in step B1 above. For each load loading stage, the damage mode of each acoustic emission event occurring in that load loading stage is determined based on the acoustic emission event cluster to which each acoustic emission event belongs and the damage mode corresponding to each acoustic emission event cluster. Then, the proportion of acoustic emission events of each damage mode in that load loading stage is determined (the proportion of acoustic emission events of a damage mode in a load loading stage is: the proportion of the number of acoustic emission events of that damage mode in that load loading stage to the total number of acoustic emission events in that load loading stage), and the damage mode with the largest proportion is determined as the dominant loss mode of that load loading stage.

[0089] Figure 5 An example is provided. In this example, the step cyclic loading test process is divided into four loading stages: loading stage 1 to loading stage 4. The proportion of acoustic emission events for each damage mode (damage mode 1 to damage mode 5) in each loading stage is determined. By analyzing the proportion of acoustic emission events for each damage mode in each loading stage, the dominant damage mechanism in different loading stages can be clearly revealed, improving the accuracy of damage identification and providing effective support for damage mechanism research.

[0090] To facilitate understanding of the methods described in the above embodiments of this application, the following is an exemplary description of a possible test monitoring process for monitoring and analyzing test data from a step cyclic loading test using the quantitative monitoring methods provided in the above embodiments of this application. See also... Figure 6 The specific steps of the test monitoring process are as follows: Step S601: Experiment preparation.

[0091] Specifically, a visual inspection can be performed on the CMC material test samples to remove those with obvious external defects, thus preventing these defects from interfering with the monitoring results. Each test sample can also be assigned a unique number, and a dedicated monitoring archive can be established for it, ensuring the traceability of monitoring data for each sample.

[0092] Furthermore, before conducting step cyclic loading tests on the test sample, an internal defect scan can be performed to obtain initial defect information. Based on this initial defect information, an initial damage baseline can be established for damage accumulation analysis during the test, providing a precise reference for subsequent damage accumulation monitoring and calculation of damage accumulation variables. This ensures the accuracy and validity of the monitoring data, distinguishing it from existing monitoring preparation methods that lack baselines and standards.

[0093] Step S602: Set up the test monitoring system.

[0094] For details, please refer to the previous text. Figure 1 Explanation of the Chinese system.

[0095] In addition, such as Figure 1 As illustrated in the diagram, in one possible implementation of this application, a customized synchronous trigger controller can be innovatively introduced into the test monitoring system, and the synchronous trigger controller can be connected to the trigger ports of the mechanical loading system, the acoustic emission monitoring system, the strain measurement system, and the full-field strain measurement system, respectively.

[0096] After debugging, when performing step cycle tests on the test sample, the mechanical loading system, acoustic emission monitoring system, strain measurement system, and full-field strain measurement system can be synchronously triggered by the synchronous trigger controller at the initial loading moment when the load loading operation is performed on the test sample based on the first level of load. This ensures that the mechanical loading system, acoustic emission monitoring system, strain measurement system, and full-field strain measurement system collect data on the test sample according to a unified time axis.

[0097] By employing synchronous triggers to synchronize the various monitoring systems, it is ensured that the load data recorded by the mechanical loading system, the full waveform data of acoustic emission acquired by the acoustic emission monitoring system, the strain data acquired by the strain measurement system, and the full-field strain image acquired by the full-field strain measurement system all carry a unified timestamp and are time-series aligned, thereby achieving precise spatiotemporal correspondence among multi-source data. This significantly improves the accuracy of damage localization and identification and provides a core guarantee for the accuracy of monitoring results.

[0098] After the test monitoring system is set up, the initial calibration of the acoustic emission system should be completed, and the system sensitivity and damage localization accuracy should be verified to provide a reliable guarantee for subsequent accurate monitoring.

[0099] Step S603: Test loading.

[0100] This involves conducting a step cyclic loading test on the sample to be tested. See the explanation of step S201 above for details.

[0101] Step S604: Multi-source synchronous data processing.

[0102] Specifically, the full waveform data of acoustic emission acquired by the acoustic emission monitoring system can be preprocessed to remove invalid signals, and time-domain and frequency-domain feature parameters can be extracted from valid acoustic emission events to construct multi-dimensional features. See the explanation above for details. By constructing multi-dimensional features based on the time-domain and frequency-domain feature parameters of valid acoustic emission events, and using these multi-dimensional features as the basis for damage pattern classification, the accuracy of damage pattern recognition can be improved, unlike existing methods that only extract single time-domain features.

[0103] Step S605: Quantitative characterization of damage accumulation.

[0104] That is, based on the sound wave propagation velocity measured when each load level is applied, the sound wave propagation velocity degradation rate is calculated; based on the sound wave propagation velocity degradation rate, the cumulative damage variable of the test sample after each load level is determined, and then the evolution curve of the cumulative damage variable with load is plotted. For details, please refer to the explanation of steps S202-S205 above.

[0105] Step S606: Damage pattern recognition.

[0106] In other words, an unsupervised clustering algorithm is used to cluster the acoustic emission events during the step cyclic loading process, and the clustered acoustic emission event clusters are identified as specific damage patterns. See the explanation above for details.

[0107] After identifying the damage modes of each acoustic emission event cluster, the number and cumulative energy percentage of acoustic emission events of each damage mode in each load loading stage can be statistically analyzed to clearly reveal the dominant damage modes in different loading stages, improve the accuracy of damage identification, and provide effective support for damage mechanism research.

[0108] Step S607: Comprehensive assessment of damage status.

[0109] In one possible implementation, a multi-source data fusion evaluation approach can be adopted, combining the mechanical response curve and full-field strain image of the test sample to verify the rationality of the determined damage accumulation variable evolution curve with load, and to locate the concentrated area of ​​material damage.

[0110] Specifically, damage accumulation within the test specimen is usually reflected in its mechanical response curve and full-field strain image. For example, if the evolution curve shows a significant increase in the damage accumulation variable of the test specimen after applying the m-th load level, then the strain value within the test specimen should also show a significant increase after applying the m-th load level in the mechanical response curve and full-field strain image, indicating that the determined evolution curve is reasonable. However, if the evolution curve shows a significant increase in the damage accumulation variable of the test specimen after applying the m-th load level, but the mechanical response curve and full-field strain image show that the strain value within the test specimen remains stable after applying the m-th load level, then the determined evolution curve is unreasonable, and it may be necessary to re-perform the stepped cyclic loading test for a new specimen and redetermine the evolution curve.

[0111] The area of ​​concentrated damage to the test sample can be determined based on the acoustic emission events or full-field strain images collected by different acoustic emission sensors. For details, please refer to the relevant technology.

[0112] In one possible implementation, the damage mode identified for the clustered acoustic emission event clusters can be verified by combining the macroscopic observation results of the fracture surface of the test sample after the step cyclic loading test.

[0113] Specifically, different damage modes may manifest differently at the fracture surface of the test sample. Therefore, if the damage mode identified for a cluster of acoustic emission events shows a specific damage mode in a certain area of ​​the test sample, and the corresponding area at the fracture surface does indeed exhibit this specific damage mode, then the damage mode identified for that cluster of acoustic emission events is reliable (for example, if the damage mode identified for a cluster of acoustic emission events shows a fiber pull-out damage mode in a certain area of ​​the test sample, and the corresponding area at the fracture surface does indeed show fiber pull-out, then the damage mode identified for that cluster of acoustic emission events is reliable). If the corresponding area does not exhibit this specific damage mode, then the identified damage mode is unreliable, and the damage mode corresponding to the acoustic emission event cluster can be re-identified.

[0114] In one possible implementation, the step cyclic loading test process for the test sample can be divided into multiple damage evolution stages based on the evolution curve of the cumulative damage variable of the test sample with load and the mechanical response characteristics.

[0115] In one example, the rate of change of the cumulative damage variable of the test sample with load can be determined based on the evolution curve, and the process of conducting the step cyclic loading test can be divided into multiple damage evolution stages based on the rate of change.

[0116] For example, the rate of change of the cumulative damage variable of the test sample with load can be determined first based on the evolution curve, and the critical load threshold that leads to accelerated damage evolution within the test sample can be determined. Then, using the determined critical load threshold as the dividing point, the process of performing step cyclic loading tests can be divided into multiple damage evolution stages. For example, if a step cyclic loading test is performed on the test sample based on 10 load levels, and the 5th load level is identified as the critical load threshold, then the 5th load level can be used as the dividing point. The process of performing load loading operations on samples based on load levels 1-4 can be considered as the first damage evolution stage, and the process of performing load loading operations on samples based on load levels 5-10 can be considered as the second damage evolution stage.

[0117] In another example, the damage mode that appears in the test sample during the load loading operation at each load level can be determined based on the damage mode corresponding to each acoustic emission event cluster and the load level corresponding to each acoustic emission event during the step cyclic loading test. Based on the damage mode that appears in the test sample during the load loading operation at each load level, the step cyclic loading test process can be divided into multiple damage evolution stages.

[0118] Specifically, based on the time axis of the load data and the time axis of each acoustic emission event obtained in step B1 above, the acoustic emission events generated within the test sample when each level of load is applied to the test sample can be determined. Therefore, for a given level of load, the damage mode appearing within the test sample when that level of load is applied can be determined based on the acoustic emission time cluster to which each acoustic emission event generated within the test sample belongs, and the damage mode corresponding to the acoustic emission time cluster. Based on this, the damage evolution stages can be divided.

[0119] For example, the load value leading to a new damage mode in the test sample can be determined based on the damage modes that appear within the test sample during the load loading operation at each load level. Using the determined load value as a dividing point, the process of performing the stepped cyclic loading test can be divided into multiple damage evolution stages. For instance, if it is determined that only acoustic emission events of damage modes A and B appear in the test sample when loads at levels 1-4 are applied, but acoustic emission events of damage mode C further appear after load level 5 is applied, then the process of performing load loading operations based on loads at levels 1-4 can be considered the first damage evolution stage, and the process of performing load loading operations based on loads at levels 5-10 can be considered the second damage evolution stage.

[0120] Based on the above steps S601-S607, a closed-loop system of monitoring-analysis-evaluation can be formed, thereby enabling limited verification of the rationality and effectiveness of the quantitative monitoring methods provided in the foregoing embodiments of this application.

[0121] Compared with existing methods for monitoring step cyclic loading damage in ceramic matrix composites, the quantitative monitoring method for the accumulation of step cyclic loading damage in ceramic matrix composites provided in the foregoing embodiments of this application has the following advantages: (1) Process standardization: The entire monitoring process is standardized and the operation standards of each link are clarified. The method can be reused in the cyclic loading damage monitoring test of various ceramic matrix composite materials, which effectively solves the problem of poor repeatability of existing test results, adapts to the needs of engineering testing, has promotion value, and further ensures the stability and effectiveness of monitoring results.

[0122] (2) Quantitative analysis of damage accumulation: A quantitative calculation model for the degradation rate of sound wave propagation velocity and damage accumulation variables is established, which breaks through the limitation of existing technologies that can only qualitatively analyze damage. It can accurately quantify the internal damage degree of the material after each loading level, clearly present the continuous evolution process of damage accumulation, and clarify the critical load threshold for accelerated damage expansion. It solves the core pain points of existing technologies that cannot quantitatively monitor and have ambiguous monitoring results. The monitoring data can be directly used for damage mechanism research and engineering evaluation, and its effectiveness is better than existing methods.

[0123] (3) High-precision synchronization of multiple systems: The innovative use of a customized synchronous trigger controller realizes the unified time axis synchronization of each monitoring system, solves the key problem of time sequence misalignment of multiple systems in the existing technology, ensures the accurate spatiotemporal correspondence between acoustic emission damage events and mechanical response and strain field changes, greatly improves the accuracy of damage location and identification, and provides core guarantee for the accuracy of monitoring results, which is different from the existing method of independent acquisition of multiple systems.

[0124] (4) Accurate damage pattern recognition and outstanding monitoring effectiveness: The innovative construction of a multi-dimensional feature space in the time and frequency domain of acoustic emission, combined with unsupervised clustering algorithm, enables accurate classification of various typical damage patterns such as matrix cracking, interface debonding, and fiber fracture. It can clearly reveal the dominant damage mechanism in different loading stages, solving the problems of low damage recognition accuracy and inability to distinguish damage types in existing technologies. The monitoring results can directly support the research on damage mechanism of CMC materials.

[0125] (5) High engineering application value: This monitoring method can accurately obtain the damage evolution law and critical damage threshold of CMC materials under cyclic loading. The monitoring process is standardized and the results are accurate and repeatable. It can not only be used for laboratory material mechanical property monitoring, but also extended to damage monitoring tests of various CMC components. It provides technical support for the service safety assessment and health monitoring technology development of high-end equipment CMC components, and further adapts to the needs of engineering applications.

[0126] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0127] The various embodiments in this specification are described in a related manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0128] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application are included within the scope of protection of this application.

Claims

1. A method for quantitatively monitoring the accumulation of step cyclic loading damage in ceramic matrix composites, characterized in that, include: Loading operations are performed on the test sample in sequence according to multiple preset load levels to conduct a step cyclic loading test on the test sample; During the load loading operation at each load level, the acoustic emission sensor assembly arranged on the test sample is used to perform calibration of the sound propagation speed to determine the sound wave propagation speed inside the test sample corresponding to each load level. For each level of load applied to the test sample, the acoustic wave propagation velocity degradation rate corresponding to that level of load is determined based on the acoustic wave propagation velocity inside the test sample corresponding to that level of load and the pre-determined initial acoustic wave propagation velocity; wherein, the initial acoustic wave propagation velocity is the acoustic wave propagation velocity inside the test sample measured by the acoustic emission sensor assembly under the initial non-damage reference state of the test sample. For each level of load applied to the test sample, based on the acoustic propagation velocity degradation rate corresponding to that level of load, the cumulative damage variable of the test sample after applying that level of load is determined. Based on the cumulative damage variable of the test sample after each level of load is applied, the evolution curve of the cumulative damage variable of the test sample with load is determined.

2. The method according to claim 1, characterized in that, During the load loading operation at a certain load level, the calibration of the speed of sound propagation is performed as follows: During the calibration window period of the current load loading operation, one or more lead breakage stimuli are performed sequentially at the preset lead breakage stimuli point; the calibration window period covers the load holding phase, the first time period before load holding, and the second time period after unloading during the load loading operation; Based on the time difference and distance difference between the stress wave generated when a lead-breaking excitation is performed and the arrival time at different acoustic emission sensors on the test sample, the instantaneous sound wave propagation speed corresponding to the lead-breaking excitation is determined. Based on the instantaneous sound wave propagation velocity corresponding to each of the one or more lead break excitations, the sound wave propagation velocity inside the test sample corresponding to the load level is determined.

3. The method according to claim 1, characterized in that, For each level of load applied to the test sample, based on the acoustic propagation velocity degradation rate corresponding to that level of load, the cumulative damage variable of the test sample after applying that level of load is determined, including: For each level of load applied to the test sample, the cumulative damage variable of the test sample after applying that level of load is obtained by substituting the acoustic propagation velocity degradation rate corresponding to that level of load into the basic damage characterization formula; the basic damage characterization formula is expressed as follows: in, This indicates that the first load is applied to the test sample. The cumulative damage variable of the test sample after each level of load. Indicates the first The degradation rate of sound wave propagation velocity corresponding to each load level.

4. The method according to claim 1, characterized in that, After determining the evolution curve of the cumulative damage variable of the test sample as a function of load, the method further includes: Based on the evolution curve, the rate of change of the damage accumulation variable with load is analyzed to determine the critical load threshold that leads to accelerated evolution of damage within the test sample.

5. The method according to claim 1, characterized in that, The method further includes: Acquire the acoustic emission events collected by the acoustic emission sensor assembly during the step cyclic loading test; Extract the time-domain and frequency-domain feature parameters of each acoustic emission event, and construct a multidimensional feature of each acoustic emission event based on the time-domain and frequency-domain feature parameters; Based on the constructed multidimensional features, the acoustic emission events are clustered using a preset unsupervised clustering algorithm to obtain multiple acoustic emission event clusters; For each clustered acoustic emission event cluster, based on the time-domain and frequency-domain characteristic parameters of the acoustic emission events within the cluster, and according to the damage mechanism of each damage mode of the ceramic matrix composite material, the damage mode corresponding to the acoustic emission event cluster is determined.

6. The method according to claim 5, characterized in that, The method further includes: Acquire multi-source monitoring data collected for the test sample during the step cyclic loading test; the multi-source monitoring data includes any one or more of the following: load data applied to the test sample, mechanical response curves at preset monitoring positions on the test sample, and full-field strain images of the test sample. For each clustered acoustic emission event cluster, the damage mode corresponding to the acoustic emission event cluster is determined based on the time-domain and frequency-domain characteristic parameters of the acoustic emission events within the cluster, according to the damage mechanism of each damage mode of the ceramic matrix composite material. This includes: Based on the time-domain and frequency-domain characteristic parameters of acoustic emission events within the acoustic emission event cluster, and combined with the multi-source monitoring data corresponding to the acoustic emission events within the acoustic emission event cluster, the damage mode corresponding to the acoustic emission event cluster is determined according to the damage mechanism of each damage mode.

7. The method according to claim 6, characterized in that, After determining the damage mode corresponding to each of the acoustic emission event clusters, the method further includes: Based on the damage modes corresponding to each acoustic emission event cluster and the multidimensional features of each acoustic emission event within each acoustic emission event cluster, a correspondence between the multidimensional features and the damage modes is established; the correspondence is used to determine the corresponding damage modes of the acoustic emission events obtained from testing the remaining test samples.

8. The method according to claim 5, characterized in that, After determining the damage mode corresponding to each of the acoustic emission event clusters, the method further includes: Based on the damage mode corresponding to each acoustic emission event cluster and the load loading stage corresponding to each acoustic emission event during the stepped cyclic loading test, the proportion of acoustic emission events of each damage mode in each load loading stage is determined; wherein, each load loading stage includes the process of performing load loading operations according to one or more consecutive levels of load.

9. The method according to claim 5, characterized in that, The method further includes: The rate of change of the cumulative damage variable of the test sample with load is determined based on the evolution curve, and the process of conducting the step cyclic loading test is divided into multiple damage evolution stages based on the rate of change. or, Based on the damage modes corresponding to each acoustic emission event cluster and the load level corresponding to each acoustic emission event during the step cyclic loading test, the damage modes appearing in the test sample during the load loading operation performed on the test sample according to each load level are determined; based on the damage modes appearing in the test sample during the load loading operation performed on the test sample according to each load level, the process of performing the step cyclic loading test is divided into multiple damage evolution stages.

10. The method according to claim 1, characterized in that, The method further includes: At the initial loading moment when the load loading operation is performed on the test sample based on the first level of load, the mechanical loading system, acoustic emission monitoring system, strain measurement system and full-field strain measurement system are synchronously triggered by a pre-configured synchronous trigger controller, so that the mechanical loading system, the acoustic emission monitoring system, the strain measurement system and the full-field strain measurement system collect data on the test sample according to a unified time axis; The mechanical loading system is used to collect load data applied to the test sample; the acoustic emission monitoring system includes the acoustic emission sensor assembly for collecting acoustic emission data within the test sample; the strain measurement system is used to collect strain data at preset monitoring locations on the test sample; and the full-field strain measurement system is used to collect full-field strain images of the test sample.

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