A method and system for hydraulic fatigue test of automobile structural parts based on loading curve control

Abstract

The application is suitable for the technical field of fatigue test of new energy automobile structural parts, and provides a hydraulic fatigue test method and system for automobile structural parts based on loading curve control, which comprises the following steps: acquiring a current sealing indentation continuity characteristic value, and generating a loading curve correction factor according to the deviation between the two when the value is lower than a reference value, so as to weaken the sealing pre-press simulation loading curve of the correction preset; superimposing the corrected sealing pre-press simulation loading curve and a road fatigue loading curve to perform hydraulic fatigue test on a current to-be-tested battery pack lower shell. The application avoids the test deviation caused by the same pre-press curve used in different production batches of workpieces, makes the corrected sealing pre-press simulation loading curve more suitable for the actual sealing indentation state of the current workpiece, thereby improving the consistency between the flange sealing test response and the actual vehicle service sealing reference, and enhancing the authenticity and reliability of the hydraulic fatigue test result.

Description

Technical Field

[0001] This invention belongs to the field of fatigue testing technology for structural components of new energy vehicles, and particularly relates to a hydraulic fatigue testing method and system for automotive structural components based on loading curve control. Background Technology

[0002] The lower casing of a new energy vehicle battery pack typically forms a closed cavity with the upper cover, seals, and fasteners via a sealed flange connection area. This sealed flange connection area serves both a connection function and a sealing function, and its fatigue performance and sealing reliability directly affect the long-term service safety of the battery pack.

[0003] In existing technologies, the durability of the sealing flange connection area of ​​the lower housing of a battery pack is typically evaluated using hydraulic fatigue testing. During testing, a preset sealing preload simulation loading curve is generally applied to simulate the sealing preload under assembly clamping conditions, and this curve is then superimposed on a road fatigue loading curve for testing. Since the preset sealing preload simulation loading curve is usually obtained by processing actual vehicle data, assembly preload data, or bench calibration data, it is costly to acquire. Therefore, the same preset sealing preload simulation loading curve is typically used for similar workpieces from different production batches.

[0004] However, even if the structure, materials, and processes of the lower casing of battery packs from different production batches are identical, the sealing indentation state formed in the sealing flange connection area under pre-compression may still differ. This difference is usually within the allowable range of the process and is not easily noticed in routine testing, but it may lead to a difference in the degree of agreement between the flange sealing test response and the sealing benchmark in actual vehicle service. Therefore, although existing hydraulic fatigue testing can complete the testing of workpieces from different production batches through a unified preset sealing pre-compression simulation loading curve, it does not utilize historical test samples to analyze the relationship between the continuity characteristic value of the sealing indentation and the response agreement, nor can it weaken the correction of the preset sealing pre-compression simulation loading curve when the continuity of the sealing indentation of the current workpiece under test is lower than a reasonable benchmark. This results in a possible deviation between the sealing pre-compression state in the test and the actual service state, thus affecting the authenticity and reliability of the hydraulic fatigue test results. Summary of the Invention

[0005] The purpose of this invention is to provide a hydraulic fatigue testing method and system for automotive structural components based on loading curve control, aiming to solve the problems mentioned in the background art.

[0006] This invention is implemented as follows: a hydraulic fatigue testing method for automotive structural components based on loading curve control, the method comprising:

[0007] Before conducting hydraulic fatigue testing on the sealing flange connection area of ​​the lower casing of the battery pack under test, retrieve the historical test database and extract historical test samples from different production batches that use the same preset sealing pre-pressure simulation loading curve.

[0008] Obtain the continuity characteristic value of the sealing indentation and the response consistency of each historical test sample; wherein, the continuity characteristic value of the sealing indentation is determined by the sealing indentation image collected after the start of the historical test, and the response consistency is determined by the deviation between the flange sealing test response and the sealing reference of the actual vehicle in service;

[0009] Establish a relationship curve between the continuity characteristic value of the sealing indentation and the response matching degree, and determine the continuity characteristic value of the sealing indentation corresponding to the stable range of the response matching degree as the benchmark value;

[0010] Obtain the current seal indentation continuity characteristic value, and when it is lower than the reference value, generate a loading curve correction factor according to the difference between the two to weaken and correct the preset seal preload simulation loading curve;

[0011] The modified simulated pre-stressing curve of the sealed battery pack was superimposed with the road fatigue loading curve to perform a hydraulic fatigue test on the lower casing of the battery pack under test.

[0012] As a further limitation of the technical solution of the present invention, the historical test samples meet the following conditions: the historical workpieces corresponding to each historical test sample have the same sealing flange connection area structure, sealing material type, hydraulic loading equipment, road fatigue loading curve and sealing pre-pressure simulation loading curve as the current battery pack under test.

[0013] As a further limitation of the technical solution of this embodiment of the invention, the specific calculation process of the continuity characteristic value of the sealing indentation includes:

[0014] Based on historical test samples, within a preset time period after the start of the simulated pre-pressure loading curve, images of sealing indentations formed along the sealing path in the sealing flange connection area are collected; wherein, the sealing indentation image is an image of the indentation distribution formed by the seal in the sealing flange connection area under pre-pressure, and the indentation distribution image includes at least the indentation area, the non-indentation area, and the indentation boundary.

[0015] The image of the sealing indentation is preprocessed, and the center line of the sealing path is extracted. The sealing path is then divided into several detection segments according to the center line of the sealing path.

[0016] Identify the effective indentation area in each detection segment, and obtain the indentation width, indentation grayscale, and indentation boundary position corresponding to each detection segment;

[0017] The indentation width dispersion is calculated based on the indentation width corresponding to each detection segment, the indentation grayscale dispersion is calculated based on the indentation grayscale corresponding to each detection segment, and the indentation interruption length and indentation center offset are determined based on the indentation boundary position corresponding to each detection segment.

[0018] The continuity characteristic value of the sealing indentation is determined based on the dispersion of the indentation width, the dispersion of the indentation grayscale, the length of the indentation interruption, and the offset of the indentation center; wherein the continuity characteristic value of the sealing indentation is negatively correlated with the dispersion of the indentation width, the dispersion of the indentation grayscale, the length of the indentation interruption, and the offset of the indentation center.

[0019] As a further limitation of the technical solution of this embodiment of the invention, the specific calculation process of the response matching degree includes:

[0020] Obtain flange sealing test response data generated during hydraulic fatigue testing of the sealing flange connection area of ​​the lower housing of the battery pack corresponding to each historical test sample; wherein, the flange sealing test response data includes at least one of the following: sealing cavity pressure attenuation, sealing surface opening and closing amount, flange local residual deformation amount, and leakage rate change amount.

[0021] Obtain the actual vehicle service sealing response benchmark data corresponding to each historical test sample; wherein, the actual vehicle service sealing response benchmark data is the flange sealing response data obtained by the lower housing of the qualified battery pack of the corresponding batch under actual vehicle service conditions;

[0022] Calculate the response deviation between the flange seal test response data and the actual vehicle service seal response benchmark data;

[0023] The response fit is determined based on the response deviation; wherein, the smaller the response deviation, the higher the response fit.

[0024] As a further limitation of the technical solution of this invention, the step of establishing the relationship curve between the continuity characteristic value of the sealing indentation and the response matching degree, and determining the continuity characteristic value of the sealing indentation corresponding to the stable range of the response matching degree as the benchmark value, includes:

[0025] Several historical test samples are sorted from smallest to largest according to the continuity characteristic value of the sealing indentation to obtain a sample sequence, and the response consistency of each historical test sample in the sample sequence is extracted to establish the relationship curve between the continuity characteristic value of the sealing indentation and the response consistency.

[0026] Analyze the relationship curve to determine whether the response fit first increases and then tends to stabilize as the characteristic value of the continuity of the sealing indentation increases;

[0027] If so, then identify the inflection point corresponding to when the response matching degree enters the stable range from the rising state, and determine the seal indentation continuity characteristic value corresponding to the inflection point as the benchmark value;

[0028] The stable interval is defined as the interval formed by the change in the response consistency between adjacent historical test samples being less than a preset change threshold and continuously satisfying a preset number of historical test samples.

[0029] As a further limitation of the technical solution of this embodiment of the invention, the step of obtaining the current sealing indentation continuity characteristic value and generating a loading curve correction factor according to the deviation difference between the two when it is lower than the reference value, so as to weaken the correction of the preset sealing pre-pressure simulation loading curve, includes:

[0030] Obtain the continuity characteristic value of the sealing indentation in the sealing flange connection area of ​​the lower housing of the battery pack under test;

[0031] Determine whether the continuity characteristic value of the sealing indentation on the lower casing of the current battery pack under test is lower than the reference value;

[0032] If the continuity characteristic value of the sealing indentation of the lower housing of the current battery pack under test is not lower than the benchmark value, then the preset sealing pre-compression simulation loading curve remains unchanged.

[0033] If the continuity characteristic value of the sealing indentation of the lower housing of the current battery pack under test is lower than the reference value, then a loading curve correction factor is generated based on the decrease of the continuity characteristic value of the sealing indentation of the lower housing of the current battery pack under test relative to the reference value, and in conjunction with a preset correction strength coefficient.

[0034] The preset sealing pre-compression simulation loading curve is weakened and corrected based on the loading curve correction factor.

[0035] As a further limitation of the technical solution of the present invention, the continuity characteristic value of the sealing indentation of the lower shell of the current battery pack under test is determined by the sealing indentation image collected within a preset time period after the start of the sealing pre-pressure simulation loading curve of the lower shell of the current battery pack under test.

[0036] As a further limitation of the technical solution of the present invention, the sealing pre-pressure simulation loading curve is a time-pressure curve used to simulate the sealing pre-pressure experienced by the sealing flange connection area of ​​the lower housing of the battery pack under the assembly and clamping state.

[0037] The simulated loading curve for sealing pre-pressure includes pre-pressure amplitudes corresponding to multiple time points; the weakening correction is based on the loading curve correction factor, reducing the pre-pressure amplitude corresponding to each time point in the simulated loading curve for sealing pre-pressure by the same correction ratio, so that the corrected simulated loading curve for sealing pre-pressure shifts downward as a whole relative to the uncorrected simulated loading curve for sealing pre-pressure, while maintaining the original loading sequence and curve change trend unchanged.

[0038] As a further limitation of the technical solution of this embodiment of the invention, the preset sealing pre-pressure simulation loading curve is weakened and corrected based on the loading curve correction factor, and a preset correction function is adopted, the correction function including:

[0039] The correction function includes:

[0040] ;

[0041] in, This refers to the simulated loading curve for the corrected seal preload at time [time missing]. The corresponding preload amplitude, This refers to the simulated loading curve of the seal preload before correction at time [time value missing]. The corresponding preload amplitude, This refers to the lower limit of the preload amplitude. This refers to the current characteristic value of the seal indentation continuity. This refers to the baseline value. This refers to the rate of decline. This refers to a preset correction strength coefficient, and satisfies... Greater than 0, This refers to the correction factor;

[0042] The lower limit of the pre-pressure amplitude is obtained by reducing the initial pre-pressure amplitude at the corresponding time according to a preset maximum reduction ratio, so that the pre-pressure amplitude of the corrected sealing pre-pressure simulation loading curve at any time is not lower than the lower limit of the pre-pressure amplitude at that time.

[0043] A hydraulic fatigue testing system for automotive structural components based on loading curve control, the system comprising:

[0044] The sample extraction module is used to retrieve historical test samples from the historical test database before performing hydraulic fatigue testing on the sealing flange connection area of ​​the lower housing of the current battery pack under test, and extract historical test samples that use the same preset sealing pre-pressure simulation loading curve but correspond to different production batches.

[0045] The parameter acquisition module is used to acquire the continuous characteristic value of the sealing indentation and the response consistency of each historical test sample. The continuous characteristic value of the sealing indentation is determined by the sealing indentation image acquired after the start of the historical test, and the response consistency is determined by the deviation between the flange sealing test response and the sealing reference of the actual vehicle in service.

[0046] The benchmark determination module is used to establish the relationship curve between the continuity characteristic value of the sealing indentation and the response matching degree, and to determine the continuity characteristic value of the sealing indentation corresponding to the stable range of the response matching degree as the benchmark value;

[0047] The curve correction module is used to obtain the current seal indentation continuity characteristic value, and when it is lower than the reference value, it generates a loading curve correction factor according to the difference between the two, so as to weaken and correct the preset seal pre-pressure simulation loading curve.

[0048] The fatigue testing module is used to overlay the corrected sealed preload simulation loading curve with the road fatigue loading curve to perform hydraulic fatigue testing on the lower shell of the battery pack under test.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] This invention extracts historical test samples from different production batches under the same simulated sealing preload curve from a historical test database, establishes the relationship between the continuity characteristic value of the sealing indentation and the response consistency, and determines the continuous sealing indentation characteristic value corresponding to the stable range of the response consistency as the benchmark value. Therefore, when performing hydraulic fatigue testing on the sealing flange connection area of ​​the lower casing of the battery pack under test, a loading curve correction factor can be generated based on the deviation of the current continuous sealing indentation characteristic value from the benchmark value, thus performing an overall weakening correction on the preset simulated sealing preload curve. This method avoids the test deviation caused by mechanically using the same preload curve for workpieces from different production batches, making the corrected simulated sealing preload curve more suitable for the actual sealing indentation state of the current workpiece, thereby improving the consistency between the flange sealing test response and the actual vehicle service sealing benchmark, and enhancing the authenticity and reliability of the hydraulic fatigue test results. Attached Figure Description

[0051] Figure 1 A flowchart of the method provided in the embodiments of the present invention;

[0052] Figure 2 This is a flowchart illustrating the process of establishing a relationship curve and determining a reference value in the method provided in this embodiment of the invention;

[0053] Figure 3 This is a flowchart illustrating the correction of the simulated loading curve for sealing preload in the method provided in this embodiment of the invention;

[0054] Figure 4The application architecture diagram of the system provided in the embodiments of the present invention. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0056] Figure 1 A flowchart of the method provided by an embodiment of the present invention is shown.

[0057] Specifically, a hydraulic fatigue testing method for automotive structural components based on loading curve control includes the following steps:

[0058] Step S100: Before performing hydraulic fatigue testing on the sealing flange connection area of ​​the lower housing of the battery pack under test, retrieve the historical test database and extract historical test samples from different production batches that use the same preset sealing pre-pressure simulation loading curve. The sealing pre-pressure simulation loading curve is a time-pressure curve used to simulate the sealing pre-pressure experienced by the sealing flange connection area of ​​the lower housing of the battery pack under assembly and clamping conditions; the sealing pre-pressure simulation loading curve includes the pre-pressure amplitude corresponding to multiple moments.

[0059] The historical test samples meet the following conditions: the historical workpieces corresponding to each historical test sample have the same sealing flange connection area structure, sealing material type, hydraulic loading equipment, road fatigue loading curve and sealing pre-pressure simulation loading curve as the current battery pack under test.

[0060] In this embodiment of the invention, the lower housing of the battery pack under test refers to the lower housing structure in a new energy vehicle power battery pack that carries the battery modules and electrical components and forms a closed cavity with the battery pack cover. The sealing flange connection area refers to the region located around the periphery of the lower housing of the battery pack, used to form a sealed connection with the battery pack cover, seals, and fasteners. It typically includes the flange face, sealing path, sealing groove, area around bolt holes, and local reinforcing structures adjacent to the flange face. Since this area serves both as an assembly connection and a sealing retention function, hydraulic fatigue testing of this area is a common testing method during the durability verification of new energy vehicle battery packs.

[0061] When conducting hydraulic fatigue testing on the sealing flange connection area of ​​the battery pack lower housing, it is typically necessary to first place the sealing flange connection area in a state close to the actual assembled sealing and tightening condition, and then superimpose a road fatigue loading curve to simulate the combined effect of sealing pre-pressure and road fatigue load on the battery pack lower housing during vehicle operation. The preset sealing pre-pressure simulation loading curve can be obtained by filtering, normalizing, and reconstructing the sealing pre-pressure data, bolt pre-tightening force transmission data, seal compression data, or bench calibration data collected under actual vehicle assembly conditions. Essentially, it is a time-pressure curve used to simulate the sealing pre-pressure experienced by the sealing flange connection area under assembled and tightened conditions. The acquisition, calibration, and application of this type of curve are relatively mature in existing hydraulic testing methods, and superimposing it with the road fatigue loading curve to simulate the test state under the combined effect of sealing tightening boundary conditions and road fatigue load is also a reasonable testing approach.

[0062] For the lower casing of the same battery pack model, workpieces from different production batches typically employ the same design standards, the same sealing flange connection area structure, the same type of sealing material, and the same or similar manufacturing processes. Based on this, existing hydraulic fatigue testing usually uses the same preset sealing pre-pressure simulation loading curve for the lower casings of battery packs from different production batches. Since this preset sealing pre-pressure simulation loading curve requires data acquisition from actual vehicles, bench calibration, and data processing, the acquisition cost is high, and it already meets the accuracy requirements of conventional testing. Therefore, it is usually not easily changed or recalibrated between different production batches.

[0063] However, in this embodiment of the invention, it is noted that although the lower housings of battery packs from different production batches maintain consistency in structural design, sealing material type, and manufacturing process, and all meet factory inspection requirements, identifiable differences may still exist in the sealing indentations formed along the sealing path in the sealing flange connection area. These differences may stem from minor variations in the hardness or compression rebound characteristics of the sealing components from different batches, manufacturing tolerances for flange flatness, differences in coating thickness, differences in localized springback after welding or forming, differences in localized contact states around bolt holes, and differences in the surface condition of the sealing groove. These differences are generally within the allowable range of the process and will not lead to the workpiece being deemed unqualified; under unpressurized or routine static observation conditions, the sealing indentations between different batches may also appear quite similar.

[0064] Furthermore, within a preset time period following the application of the simulated pre-pressure loading curve, the continuity, uniformity, boundary position, and local interruptions of indentations along the sealing path in the sealing flange connection area of ​​different batches may be amplified. In other words, while some batches may appear similar during routine dimensional inspections or static seal checks, the indentation state formed in the initial stage of pre-pressure loading is not entirely consistent. Since the indentation state is typically not a primary control parameter in conventional hydraulic fatigue testing, and it requires image acquisition and analysis for stable characterization, existing testing procedures often do not correct the preset simulated pre-pressure loading curve for the indentation state of different batches.

[0065] Those skilled in the art, through long-term testing data, have discovered that for workpieces from different production batches using the same preset sealing preload simulation loading curve, the flange sealing test response obtained in hydraulic fatigue testing, while generally meeting the test requirements, still exhibits varying degrees of difference in response consistency with the actual vehicle service sealing benchmark obtained by the corresponding batch of qualified workpieces under actual vehicle service conditions. This difference in response consistency typically does not exceed the allowable range for production or testing, and therefore is not considered abnormal in routine testing, nor does it directly lead to the workpiece being deemed unqualified.

[0066] However, further analysis of historical test samples reveals a correlation between the aforementioned differences in response agreement and the state of the sealing indentation formed after the start of the simulated pre-compression loading curve. Specifically, the more continuous and uniform the sealing indentation, the more stable the sealing contact state formed in the initial stage of pre-compression loading in the sealing flange connection area. Consequently, the flange sealing test response obtained after superimposing the road fatigue loading curve is more likely to closely approximate the actual vehicle service sealing reference. Conversely, when there are local indentation interruptions, large fluctuations in indentation width, or significant indentation center offsets in the sealing path, even if the workpiece itself still meets production inspection requirements, the same preset simulated pre-compression loading curve may cause a deviation between the sealing clamping state in the hydraulic fatigue test and the actual service state.

[0067] Therefore, this invention does not simply apply the same preset sealing pre-compression simulation loading curve to the lower casing of the battery pack under test for different production batches. Instead, before the hydraulic fatigue test, it retrieves the historical test database and uses the sealing indentation continuity characteristic value and response consistency in the historical test samples to determine the benchmark value for the current test. When the current sealing indentation continuity characteristic value is lower than the benchmark value, the preset sealing pre-compression simulation loading curve is weakened and corrected. In this way, while keeping the road fatigue loading curve unchanged, the sealing pre-compression simulation loading curve can be made more suitable for the sealing indentation state of the lower casing of the battery pack under test, thereby improving the consistency between the hydraulic fatigue test response and the sealing response in actual vehicle service, and avoiding test results that are too high or distorted due to the preset sealing pre-compression simulation loading curve not being suitable for the current batch of workpieces.

[0068] The historical test database can be formed by combining existing hydraulic fatigue test records, production batch records, seal indentation image records, actual vehicle service verification records, and bench calibration records. Its underlying data can include production batch information of historical workpieces, structural information of the sealing flange connection area, sealing material type, seal batch information, hydraulic loading equipment information, preset seal pre-pressure simulation loading curves, road fatigue loading curves, seal indentation images, flange seal test response data, actual vehicle service seal response benchmark data, test environment data, and equipment calibration data. The acquisition of the above data can be achieved through hydraulic loading equipment, image acquisition devices, pressure sensors, displacement sensors, airtightness testing devices, and data acquisition systems, all of which can be obtained using mature testing and recording methods.

[0069] In step S100, historical test samples from different production batches using the same preset sealing pre-pressure simulation loading curve are extracted from the historical test database. This aims to control extraneous variables so that the subsequently established relationship curve between the continuity characteristic value of the sealing indentation and the response consistency primarily reflects the impact of differences in the sealing indentation state between different production batches on the response consistency. If historical test samples show significant differences in the structure of the sealing flange connection area, the type of sealing material, the hydraulic loading equipment, the road fatigue loading curve, or the sealing pre-pressure simulation loading curve, then the difference in response consistency may be due to structural differences, material differences, equipment differences, or differences in loading conditions, making it difficult to accurately reflect the correlation between the continuity characteristic value of the sealing indentation and the response consistency.

[0070] Therefore, this embodiment of the invention sets relatively strict screening conditions for historical test samples. Specifically, the historical workpiece corresponding to each historical test sample must have the same sealing flange connection area structure, sealing material type, hydraulic loading equipment, road fatigue loading curve, and sealing pre-pressure simulation loading curve as the current battery pack under test. Furthermore, in other embodiments, historical test samples may also be required to meet the following requirements: identical or similar sealing component supply batches, bolt specifications, pre-tightening processes, test environment temperature, test environment humidity, image acquisition angle, image resolution, sensor arrangement, and data sampling frequency. Through the above screening, the comparability between historical test samples can be improved.

[0071] In practical applications, historical test samples do not necessarily need to be completely identical in all parameters. For certain parameters that do not substantially affect the continuity characteristics of the seal indentation and the response fit, differences within a preset range are permissible. For example, ambient temperature, humidity, image brightness, sensor mounting location, or some manufacturing tolerances can fluctuate within acceptable limits. Therefore, a preset similarity threshold can be set for historical test samples to evaluate structural similarity, material similarity, loading curve similarity, test equipment similarity, and test environment similarity. When the overall similarity is not lower than the preset similarity threshold, the corresponding historical test sample is considered usable. The preset similarity threshold can be determined based on the number of samples in the historical test database, test repeatability requirements, equipment error range, and the company's internal testing specifications.

[0072] The reason for using a preset similarity threshold is that hydraulic fatigue test data itself has a certain degree of engineering variability. If historical test samples are required to be completely consistent across all underlying data, the number of usable samples may be insufficient, thus affecting the stability of the relationship curve. On the other hand, if the screening conditions are too lenient, interference factors unrelated to the continuity of the sealing indentation may be introduced. Therefore, by screening historical test samples using the same key conditions and a preset similarity threshold, the comparability of samples can be ensured while increasing the number and representativeness of historical test samples, providing a reliable data foundation for subsequently determining benchmark values ​​and correcting the preset sealing preload simulation loading curve.

[0073] Furthermore, the hydraulic fatigue testing method for automotive structural components based on loading curve control also includes the following steps:

[0074] Step S200: Obtain the continuity characteristic value of the sealing indentation and the response consistency of each historical test sample; wherein, the continuity characteristic value of the sealing indentation is determined by the sealing indentation image collected after the start of the historical test, and the response consistency is determined by the deviation between the flange sealing test response and the actual vehicle service sealing reference.

[0075] The specific calculation process for the continuity characteristic value of the sealing indentation includes:

[0076] Based on historical test samples, within a preset time period after the start of the simulated pre-pressure loading curve, images of sealing indentations formed along the sealing path in the sealing flange connection area are acquired. These images are distribution images of indentations formed by the seal under pre-pressure in the sealing flange connection area, including at least indentation areas, non-indentation areas, and indentation boundaries. The sealing indentation images undergo image preprocessing, and the centerline of the sealing path is extracted. The sealing path is then divided into several detection segments according to the centerline. Effective indentation areas in each detection segment are identified, and the corresponding indentation width, grayscale, and boundary position are obtained. The indentation width dispersion is calculated based on the indentation width of each detection segment, the grayscale dispersion is calculated based on the grayscale of each detection segment, and the indentation interruption length and center offset are determined based on the boundary position of each detection segment.

[0077] The continuity characteristic value of the sealing indentation is determined based on the dispersion of indentation width, the dispersion of indentation grayscale, the length of indentation interruption, and the offset of indentation center. The continuity characteristic value is negatively correlated with the dispersion of indentation width, the dispersion of indentation grayscale, the length of indentation interruption, and the offset of indentation center. In other words, the continuity characteristic value of the sealing indentation decreases as the dispersion of indentation width, the dispersion of indentation grayscale, the length of indentation interruption, and the offset of indentation center increase.

[0078] The specific calculation process for response fit includes:

[0079] Obtain flange sealing test response data generated during hydraulic fatigue testing of the sealing flange connection area of ​​the battery pack lower housing corresponding to each historical test sample; wherein, the flange sealing test response data includes at least one of the following: sealing cavity pressure attenuation, sealing surface opening and closing amount, flange local residual deformation amount, and leakage rate change amount; obtain the actual vehicle service sealing response benchmark data corresponding to each historical test sample; wherein, the actual vehicle service sealing response benchmark data is the flange sealing response data obtained by the qualified battery pack lower housing of the corresponding batch under actual vehicle service conditions; calculate the response deviation between the flange sealing test response data and the actual vehicle service sealing response benchmark data; determine the response consistency based on the response deviation; wherein, the smaller the response deviation, the higher the response consistency.

[0080] In this embodiment of the invention, step S200 is used to extract the core data required for establishing the subsequent relationship curve from historical test samples, namely, the seal indentation continuity characteristic value and the response fit. The seal indentation continuity characteristic value is not the conventional structural stiffness, structural strength, or single-point sealing pressure value, but rather a characteristic parameter used to characterize the continuity, uniformity, and positional stability of the indentation formed along the sealing path by the sealing flange connection area of ​​the battery pack lower housing after the sealing pre-pressure simulation loading curve is applied.

[0081] Specifically, in the hydraulic fatigue tests corresponding to historical test samples, after the simulated pre-pressure loading curve is applied, the seal is subjected to pre-pressure, forming an indentation on the flange face, sealing groove, or sealing contact surface in the sealing flange connection area. This indentation reflects the actual contact state between the seal and the sealing flange connection area. For example, when the indentation is continuous, uniform in width, and stable in center position, it indicates that the pressure state of the seal on the sealing path is relatively balanced; when there are local interruptions in the indentation, abrupt changes in the indentation width, or offset of the indentation center, it indicates that there are local insufficient contacts, local bias pressure, or unstable sealing contacts on the sealing path.

[0082] Sealing indentation images can be obtained using industrial cameras, line scan cameras, vision inspection devices, pressure-sensitive film imaging devices, or other image acquisition devices capable of acquiring the indentation distribution along the sealing path. In one embodiment, a pressure-sensitive film or a developable medium can be placed between the seal and the sealing flange connection area, allowing it to form an indentation distribution image characterizing the contact pressure and contact area under pre-pressure. In another embodiment, indentation images on the seal surface or flange contact surface can be acquired by an image acquisition device within a preset time period after pre-pressure loading. The aforementioned image acquisition, pressure-sensitive film development, and industrial vision recognition are all mature and feasible detection methods. The improvement of this invention lies in further using these indentation images to construct continuous feature values ​​for sealing indentations and using them as the data basis for subsequent correction of the simulated pre-pressure loading curve.

[0083] After obtaining the image of the seal indentation, image preprocessing can be performed. Image preprocessing may include at least one of the following: grayscale conversion, filtering and noise reduction, brightness equalization, edge enhancement, image registration, and distortion correction. Image preprocessing can reduce the impact of ambient light, acquisition angle, image noise, and local reflections on the indentation recognition results, thereby improving the stability of subsequent effective indentation area recognition.

[0084] Then, the centerline of the sealing path can be extracted based on the designed sealing path of the sealing flange connection area or the indentation distribution pattern in the image. The centerline of the sealing path can be understood as the central trajectory extending along the theoretical compression path of the seal, which can be extracted based on the geometric position of the sealing groove, the installation position of the seal, or the geometric center of the indentation area in the image. After extracting the centerline of the sealing path, the sealing path is divided into several detection segments according to a preset length, preset angle, or preset sampling interval. By dividing the sealing path into several detection segments, the annular or near-annular sealing path can be transformed into multiple quantifiable and comparable local areas, facilitating a unified analysis of the indentation state at different locations.

[0085] For each detection segment, the effective indentation area can be identified. The effective indentation area refers to the region in the image that reflects the actual pressure contact of the seal, and can be obtained through grayscale thresholding, edge detection, region connectivity analysis, color feature recognition, or machine vision segmentation models. After identifying the effective indentation area, the indentation width, indentation grayscale, and indentation boundary position corresponding to each detection segment can be further obtained. Among them, the indentation width is used to characterize the contact width formed by the seal under pressure in the detection segment; the indentation grayscale can be used to characterize the indentation strength or contact pressure distribution characteristics in the detection segment; and the indentation boundary position is used to characterize the positional relationship of the indentation area relative to the centerline of the sealing path.

[0086] After obtaining the indentation width, indentation grayscale, and indentation boundary position for each detection segment, the dispersion of indentation width, the dispersion of indentation grayscale, the indentation interruption length, and the indentation center offset can be further calculated. The dispersion of indentation width can be determined by the variance, standard deviation, range, or coefficient of variation of the indentation width for each detection segment, and is used to characterize whether the indentation width is uniform along the sealing path. The dispersion of indentation grayscale can be determined by the variance, standard deviation, range, or coefficient of variation of the indentation grayscale for each detection segment, and is used to characterize whether the contact pressure distribution along the sealing path is uniform. The indentation interruption length can be determined based on the length of the non-indentation area between adjacent effective indentation areas, the length of the ineffective indentation area, or the length of the continuous area below the effective indentation threshold, and is used to characterize whether there is a local contact interruption in the sealing path. The indentation center offset can be determined based on the distance between the centerline of the indentation area in each detection segment and the centerline of the sealing path, and is used to characterize whether there is displacement or bias pressure after the seal is compressed.

[0087] The continuity characteristic value of the sealing indentation can be obtained by normalizing and weighting the aforementioned indentation width dispersion, indentation grayscale dispersion, indentation interruption length, and indentation center offset. For example, the indentation width dispersion, indentation grayscale dispersion, indentation interruption length, and indentation center offset can be normalized separately and then fused according to preset weights to obtain a value used to characterize the continuity of the indentation. Since a larger indentation width dispersion, a larger indentation grayscale dispersion, a longer indentation interruption length, and a larger indentation center offset all indicate a more unstable indentation state on the sealing path, the continuity characteristic value of the sealing indentation is negatively correlated with the above parameters. In other words, a larger continuity characteristic value of the sealing indentation indicates a more continuous and uniform sealing indentation, and fewer local interruptions, offsets, and contact imbalances in the sealing path.

[0088] By setting a continuity characteristic value for the sealing indentation, this invention can transform the sealing indentation state, which is originally difficult to quantify directly, into a comparable, sortable, and curve-correcting numerical parameter. This parameter reflects the actual sealing contact state formed by the lower casing of battery packs from different production batches after the start of the simulated sealing pre-compression loading curve, thus providing a data foundation for subsequent analysis of the relationship between the continuity characteristic value of the sealing indentation and the response fit. Compared to judging solely based on structural dimensions, material batches, or single-point pressure data, the continuity characteristic value of the sealing indentation more directly corresponds to the actual sealing contact quality of the sealing flange connection area.

[0089] Response consistency is used to characterize the degree of closeness between the flange seal test response in historical test samples and the actual vehicle service seal reference. Flange seal test response data includes at least one of the following: sealing cavity pressure attenuation, sealing surface opening and closing amount, flange local residual deformation, and leakage rate change, which can be obtained through the data acquisition module of a pressure sensor, displacement sensor, airtightness detection device, or hydraulic testing system.

[0090] The benchmark data for sealing response in actual vehicle service is the flange sealing response data obtained by the lower housing of the qualified battery pack of the corresponding batch under actual vehicle service conditions. For example, the amount of pressure decay in the sealing cavity, the amount of opening and closing of the sealing surface, the amount of local residual deformation of the flange, or the change in leakage rate obtained after a preset mileage, preset road conditions, or preset service period.

[0091] When calculating the response fit, the response deviation between the flange seal test response data and the actual vehicle service seal response benchmark data is calculated. When multiple response data are used, the deviations of each response data are normalized and weighted and fused to obtain the comprehensive response deviation. The smaller the response deviation or comprehensive response deviation, the closer the flange seal test response is to the actual vehicle service seal benchmark, and the higher the corresponding response fit.

[0092] Step S200 allows for the acquisition of the seal indentation continuity characteristic value and response consistency for each historical test sample. The former reflects the seal indentation state formed after the start of the seal pre-compression simulation loading curve, while the latter reflects the degree of closeness between the hydraulic fatigue test results of the historical test sample and the seal response in actual vehicle service. Together, they form the data basis for establishing the relationship curve between the seal indentation continuity characteristic value and the response consistency.

[0093] Furthermore, the hydraulic fatigue testing method for automotive structural components based on loading curve control also includes the following steps:

[0094] Step S300: Establish the relationship curve between the continuity characteristic value of the sealing indentation and the response matching degree, and determine the continuity characteristic value of the sealing indentation corresponding to the stable range of the response matching degree as the benchmark value.

[0095] Specifically, Figure 2 A flowchart is shown to establish the relationship curve and determine the baseline value.

[0096] The process of establishing the relationship curve between the continuity characteristic value of the sealing indentation and the response consistency, and determining the continuity characteristic value of the sealing indentation corresponding to the stable range of the response consistency as the benchmark value, specifically includes the following steps:

[0097] Step S301: Sort several historical test samples according to the continuous characteristic value of sealing indentation from small to large to obtain a sample sequence, and extract the response consistency of each historical test sample in the sample sequence to establish the relationship curve between the continuous characteristic value of sealing indentation and the response consistency.

[0098] Step S302: Analyze the relationship curve and determine whether the response fit first increases and then tends to stabilize as the characteristic value of the continuity of the sealing indentation increases;

[0099] Step S303: If yes, identify the inflection point when the response matching degree enters the stable range from the rising state, and determine the sealing indentation continuity characteristic value corresponding to the inflection point as the benchmark value.

[0100] The stable interval is defined as the interval formed when the change in the response consistency between adjacent historical test samples is less than a preset threshold and continues to meet a preset number of historical test samples. Once this characteristic value reaches a certain level, further increasing the continuity of the sealing indentation has a diminishing impact on the consistency between the flange sealing test response and the actual vehicle service sealing response, thus the response consistency enters the stable interval.

[0101] In this embodiment of the invention, step S300 is used to perform a correlation analysis on the continuity characteristic value of the sealing indentation and the response consistency to determine the influence law of the continuity characteristic value of the sealing indentation on the response consistency in historical test samples of different production batches, and thereby obtain a benchmark value for subsequent correction judgment.

[0102] Specifically, each historical test sample can be represented as a data point consisting of the continuity characteristic value of the sealing indentation and the response consistency. These data points are then sorted from smallest to largest according to the continuity characteristic value of the sealing indentation, and a relationship curve is established with the continuity characteristic value of the sealing indentation as the x-axis and the response consistency as the y-axis. For data points with local fluctuations, moving averages, piecewise linear fitting, or local smoothing can be used to reduce the impact of individual sample test errors on the relationship curve.

[0103] Inflection points can be identified by the change in response consistency between adjacent historical test samples. When the change in response consistency between a consecutive preset number of adjacent historical test samples is less than a preset threshold, the response consistency is considered to have entered a stable range, and the seal indentation continuity characteristic value corresponding to the starting position of this stable range is determined as the baseline value. Alternatively, it can be determined by the local slope of the relationship curve; when the local slope decreases to below a preset slope threshold and remains there, the corresponding position is determined as the inflection point.

[0104] Therefore, the benchmark value is not an empirical value set arbitrarily, but is determined based on the actual relationship between the continuity characteristic value of the sealing indentation and the response consistency in historical test samples. It is used to determine whether the lower casing of the current battery pack under test needs to be weakened by the simulated loading curve of the preset sealing pre-pressure.

[0105] If, after analyzing the relationship curve, no trend is found in which the response fit first increases and then tends to stabilize as the characteristic value of the continuity of the sealing indentation increases, the subsequent weakening correction step based on the benchmark value will not be executed.

[0106] The significance of determining the inflection point lies in its role as a critical level characterizing the continuity of the sealing indentation, which allows the response consistency to stabilize. When the continuity characteristic value of the sealing indentation on the lower casing of the battery pack under test is lower than the benchmark value corresponding to this inflection point, it indicates that the sealing indentation state has not yet reached the indentation continuity level corresponding to the stable response consistency in historical samples. Using the original preset sealing pre-compression simulation loading curve may lead to a deviation between the test response and the actual vehicle service sealing benchmark. Therefore, it is necessary to weaken and correct the preset sealing pre-compression simulation loading curve based on the deviation difference.

[0107] Furthermore, the hydraulic fatigue testing method for automotive structural components based on loading curve control also includes the following steps:

[0108] Step S400: Obtain the current sealing indentation continuity characteristic value, and when it is lower than the reference value, generate a loading curve correction factor according to the difference between the two to weaken and correct the preset sealing pre-pressure simulation loading curve.

[0109] Step S500: The corrected sealing pre-compression simulation loading curve is superimposed with the road fatigue loading curve to perform a hydraulic fatigue test on the lower casing of the battery pack under test.

[0110] Specifically, Figure 3 A flowchart is shown for correcting the simulated loading curve of the seal preload.

[0111] The process of obtaining the current seal indentation continuity characteristic value and generating a loading curve correction factor based on the deviation difference when the value is lower than the benchmark value, in order to weaken and correct the preset seal pre-pressure simulation loading curve, specifically includes the following steps:

[0112] Step S401: Obtain the continuity characteristic value of the sealing indentation in the sealing flange connection area of ​​the lower housing of the current battery pack under test; the continuity characteristic value of the sealing indentation in the lower housing of the current battery pack under test is determined by the sealing indentation image collected within a preset time period after the start of the sealing pre-pressure simulation loading curve of the lower housing of the current battery pack under test.

[0113] Step S402: Determine whether the continuity characteristic value of the sealing indentation on the lower casing of the battery pack under test is lower than the reference value;

[0114] Step S403: If the continuity characteristic value of the sealing indentation of the lower housing of the battery pack under test is not lower than the reference value, then the preset sealing pre-compression simulation loading curve remains unchanged.

[0115] Step S404: If the continuity characteristic value of the sealing indentation of the lower housing of the current battery pack under test is lower than the reference value, then according to the decrease of the continuity characteristic value of the sealing indentation of the lower housing of the current battery pack under test relative to the reference value, and in conjunction with the preset correction strength coefficient, a loading curve correction factor is generated.

[0116] Step S405: The preset sealing pre-pressure simulation loading curve is weakened and corrected based on the loading curve correction factor. The weakening correction is based on the loading curve correction factor, which reduces the pre-pressure amplitude corresponding to each moment in the sealing pre-pressure simulation loading curve by the same correction ratio, so that the corrected sealing pre-pressure simulation loading curve shifts downward as a whole relative to the uncorrected sealing pre-pressure simulation loading curve, while maintaining the original loading sequence and curve change trend unchanged.

[0117] The preset sealing preload simulation loading curve is weakened by a loading curve correction factor. A preset correction function is used, which includes:

[0118] The correction functions include:

[0119] ;

[0120] in, This refers to the simulated loading curve for the corrected seal preload at time [time missing]. The corresponding preload amplitude, This refers to the simulated loading curve of the seal preload before correction at time [time value missing]. The corresponding preload amplitude, This refers to the lower limit of the preload amplitude. This refers to the current characteristic value of the seal indentation continuity. This refers to the baseline value. This refers to the rate of decline. This refers to a preset correction strength coefficient, and satisfies... Greater than 0, This refers to the correction factor;

[0121] The lower limit of the pre-pressure amplitude is obtained by reducing the initial pre-pressure amplitude at the corresponding time according to the preset maximum reduction ratio, so that the pre-pressure amplitude of the corrected sealing pre-pressure simulation loading curve at any time is not lower than the lower limit of the pre-pressure amplitude at that time.

[0122] Because the simulated loading curve of the sealing preload changes over time, the lower limit of the preload amplitude at each moment should not be a fixed constant, but should be determined by the initial preload amplitude at that moment according to the preset maximum decrease ratio.

[0123] In this embodiment of the invention, steps S400 and S500 are used to apply the benchmark values ​​obtained from the aforementioned historical test samples to the hydraulic fatigue test of the lower housing of the current battery pack under test. That is, the invention does not merely discover the relationship between the continuity characteristic value of the sealing indentation and the response consistency in historical data, but further utilizes this relationship to adapt and correct the preset sealing pre-compression simulation loading curve used in the current test, making the pre-compression state of the lower housing of the current battery pack under test in the hydraulic fatigue test closer to its actual service state.

[0124] The preset time period should not be too short or too long. If the preset time period is too short, the seal has not yet formed a stable indentation in the sealing flange connection area, and the acquired sealing indentation image is easily affected by transient contact in the early stage of loading, image noise, or local rebound, making it difficult to accurately characterize the sealing indentation state. If the preset time period is too long, the sealing indentation image may have been affected by subsequent fatigue loading, creep of the sealing material, or local residual deformation, and cannot accurately reflect the sealing assembly clamping state formed in the initial stage of the sealing pre-compression simulation loading curve.

[0125] In step S404, when the continuity characteristic value of the sealing indentation of the lower housing of the current battery pack under test is lower than the reference value, a loading curve correction factor is generated based on the magnitude of its decrease relative to the reference value. This is because the magnitude of the decrease reflects the degree of deviation of the sealing indentation state of the current lower housing of the battery pack under test from the stable range of response consistency in historical samples. A larger magnitude of decrease indicates insufficient continuity, uniformity, or positional stability of the indentation in the current sealing flange connection area, and a more significant mismatch between the original preset sealing pre-pressure simulation loading curve and the current workpiece, thus requiring greater weakening correction. Conversely, a smaller magnitude of decrease indicates that the current workpiece is close to the reference state, requiring only a smaller correction or no significant correction at all. The preset correction intensity coefficient is used to control the sensitivity of the conversion from the magnitude of the decrease to the curve weakening magnitude, avoiding over-correction due to fluctuations in single image recognition or sample discreteness.

[0126] In step S405, the weakening correction involves reducing the pre-pressure amplitude at each moment in the simulated sealing pre-pressure loading curve by the same correction ratio, causing the entire simulated sealing pre-pressure loading curve to shift downward while maintaining the original loading sequence and curve trend. In other words, this invention does not only correct a single local peak, a single moment, or a single segment, but rather synchronously corrects the pre-pressure level of the entire simulated sealing pre-pressure loading curve. This is because the simulated sealing pre-pressure loading curve simulates the overall sealing pre-pressure experienced by the sealing flange connection area under assembly and tightening conditions. Its mismatch is mainly manifested in the overall pre-pressure level not matching the sealing indentation state of the current workpiece under test, rather than an anomaly at a single instant. Therefore, shifting the entire curve downward allows the preset simulated sealing pre-pressure loading curve to be more suitable for the lower casing of the battery pack under test without disrupting the original loading rhythm and trend.

[0127] This approach also differs from existing technologies that correct for single-point peak values, local impact segments, or local load fragments. The correction target of this invention is the overall pressure level of the simulated pre-stressing curve. The correction is based on the deviation of the continuity characteristic value of the sealing indentation of the lower casing of the battery pack under test from the reference value. The correction objective is to improve the consistency between the flange sealing test response and the sealing reference value in actual vehicle service.

[0128] The correction function used in this embodiment of the invention can be understood as follows: at each moment, the weakening ratio corresponding to that moment is first determined based on the decrease in the current sealing indentation continuity characteristic value relative to the reference value and the preset correction strength coefficient; then, the pre-pressure amplitude at that moment before correction is reduced according to the weakening ratio; simultaneously, the lower limit of the pre-pressure amplitude corresponding to that moment is used as a protective constraint to ensure that the corrected pre-pressure amplitude will not be lower than the minimum allowable pre-pressure amplitude at that moment. Since the sealing pre-pressure simulation loading curve itself changes with time, the lower limit of the pre-pressure amplitude at each moment is not a fixed constant, but is obtained by reducing the initial pre-pressure amplitude at that moment according to the preset maximum weakening ratio.

[0129] The above correction method is intuitive and effective. It ensures that the greater the degree to which the current sealing indentation continuity characteristic value is lower than the baseline value, the greater the overall downward shift of the curve. Simultaneously, it avoids over-correction by limiting the pre-pressure amplitude, guaranteeing that the lower casing of the battery pack under test remains in an effective sealing pre-pressure state. Besides the above calculation method, in other implementations, a lookup table, piecewise correction, or nonlinear mapping method can also be used to determine the loading curve correction factor. For example, a correspondence table between the decrease magnitude and the correction ratio can be established in advance; a smaller correction ratio can be used when the decrease magnitude is small, and a larger correction ratio can be used when the decrease magnitude is large; or a nonlinear relationship between the decrease magnitude and the correction ratio can be obtained by fitting historical test samples.

[0130] For example, in one specific embodiment, the historical test database includes historical test samples from six different production batches, with sealing indentation continuity characteristic values ​​of 0.62, 0.70, 0.78, 0.84, 0.88, and 0.91, respectively, and corresponding response fits of 0.84, 0.88, 0.92, 0.95, 0.956, and 0.958. After establishing a relationship curve based on the above data, it can be seen that when the sealing indentation continuity characteristic value reaches 0.84, the increase in response fit significantly decreases and enters a stable range; therefore, 0.84 is determined as the baseline value.

[0131] For the lower casing of the battery pack under test, sealing indentation images are acquired within a preset time period after the start of the simulated sealing pre-compression loading curve. Based on these images, the current sealing indentation continuity characteristic value is calculated to be 0.756. Since 0.756 is lower than the baseline value of 0.84, a weakening correction is required. The current sealing indentation continuity characteristic value decreases by 10% relative to the baseline value. If the preset correction strength coefficient is 0.6, the loading curve correction factor is 6%. If the preset maximum weakening ratio is 12%, the current 6% weakening does not exceed the maximum weakening ratio, and the pre-compression amplitude corresponding to each moment in the simulated sealing pre-compression loading curve can be directly reduced synchronously by 6%.

[0132] For example, the pre-compression simulation loading curve before correction showed pre-pressure amplitudes of 0.2 MPa, 0.8 MPa, 1.2 MPa, 1.2 MPa, and 0.9 MPa at 0, 5, 10, 20, and 25 seconds, respectively. After correction with a 6% reduction ratio, the pre-pressure amplitudes at the above times were 0.188 MPa, 0.752 MPa, 1.128 MPa, 1.128 MPa, and 0.846 MPa, respectively. If the maximum allowable reduction ratio at each time point is 12%, then the corrected pre-pressure amplitudes are all higher than the lower limit of the pre-pressure amplitude at the corresponding time point, therefore the correction result is valid. Subsequently, the corrected pre-compression simulation loading curve was superimposed on the road fatigue loading curve, and a hydraulic fatigue test was performed on the lower casing of the battery pack under test. Thus, the pre-compression level of the lower casing of the battery pack under test was appropriately reduced during the test, but the original loading sequence and curve trend remained unchanged.

[0133] By employing the above method, this invention can adapt and correct the preset sealing pre-compression simulation loading curve to address the differences in sealing indentations formed in the sealing flange connection area of ​​battery pack lower housings from different production batches. This avoids mechanically applying the same sealing pre-compression simulation loading curve to all batches of workpieces. This method addresses the core issue identified in the aforementioned research: although workpieces from different production batches all meet production requirements, differences in their sealing indentation states can affect the consistency between the hydraulic fatigue test response and the actual vehicle service sealing benchmark. By introducing sealing indentation continuity characteristic values, benchmark values, and loading curve correction factors, this invention can improve the consistency between test results and actual service results while ensuring the effectiveness of hydraulic fatigue testing, reducing test deviations caused by mismatches in the preset sealing pre-compression simulation loading curve.

[0134] The beneficial effects of this invention are as follows: Firstly, it can utilize data from different production batches in a historical test database to establish a relationship between the continuity characteristic value of the sealing indentation and the response consistency, thus providing a data basis for correcting the preset sealing pre-compression simulation loading curve. Secondly, when the continuity characteristic value of the sealing indentation on the lower casing of the battery pack under test is lower than the benchmark value, the sealing pre-compression simulation loading curve can be corrected in an overall weakening manner, making the current test more closely match the sealing indentation state of the current workpiece. Furthermore, this invention does not require the re-collection of complete real vehicle load data or the reconstruction of the road fatigue loading curve; it only requires adaptation and correction of the sealing pre-compression simulation loading curve, thus exhibiting good engineering feasibility.

[0135] This invention can be applied to batch sampling inspection, durability verification, fatigue evaluation of sealing flange connection areas, and hydraulic fatigue testing adaptation scenarios for the lower housing of new energy vehicle battery packs. Especially when the structure, sealing material type, and testing equipment of the lower housing of the battery pack are consistent, but there are differences in the sealing indentation state between different production batches, this invention can provide an objective basis for correcting the preset sealing pre-pressure simulation loading curve, and has good prospects for widespread application.

[0136] Furthermore, Figure 4 An application architecture diagram of the system provided in an embodiment of the present invention is shown.

[0137] In another preferred embodiment of the present invention, a hydraulic fatigue testing system for automotive structural components based on loading curve control includes:

[0138] The sample extraction module 100 is used to retrieve historical test samples from the historical test database and extract historical test samples from different production batches that use the same preset sealing pre-pressure simulation loading curve before performing hydraulic fatigue testing on the sealing flange connection area of ​​the lower housing of the current battery pack under test.

[0139] The parameter acquisition module 200 is used to acquire the continuous characteristic value of the sealing indentation and the response consistency of each historical test sample; wherein, the continuous characteristic value of the sealing indentation is determined by the sealing indentation image acquired after the start of the historical test, and the response consistency is determined by the deviation between the flange sealing test response and the sealing reference of the actual vehicle service.

[0140] The benchmark determination module 300 is used to establish the relationship curve between the continuous characteristic value of the sealing indentation and the response matching degree, and to determine the continuous characteristic value of the sealing indentation corresponding to the stable range of the response matching degree as the benchmark value.

[0141] The curve correction module 400 is used to obtain the current seal indentation continuity characteristic value, and when it is lower than the reference value, it generates a loading curve correction factor according to the difference between the two, so as to weaken and correct the preset seal pre-pressure simulation loading curve.

[0142] The fatigue testing module 500 is used to superimpose the corrected sealed preload simulation loading curve with the road fatigue loading curve to perform hydraulic fatigue testing on the lower shell of the battery pack under test.

[0143] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A hydraulic fatigue testing method for automotive structural components based on loading curve control, characterized in that, The method includes: Before conducting hydraulic fatigue testing on the sealing flange connection area of ​​the lower casing of the battery pack under test, retrieve the historical test database and extract historical test samples from different production batches that use the same preset sealing pre-pressure simulation loading curve. Obtain the continuity characteristic value of the sealing indentation and the response consistency of each historical test sample; wherein, the continuity characteristic value of the sealing indentation is determined by the sealing indentation image collected after the start of the historical test, and the response consistency is determined by the deviation between the flange sealing test response and the sealing reference of the actual vehicle in service; Establish a relationship curve between the continuity characteristic value of the sealing indentation and the response matching degree, and determine the continuity characteristic value of the sealing indentation corresponding to the stable range of the response matching degree as the benchmark value; Obtain the current seal indentation continuity characteristic value, and when it is lower than the reference value, generate a loading curve correction factor according to the difference between the two to weaken and correct the preset seal preload simulation loading curve; The modified simulated pre-stressing curve of the sealed battery pack was superimposed with the road fatigue loading curve to perform a hydraulic fatigue test on the lower casing of the battery pack under test.

2. The hydraulic fatigue testing method for automotive structural components based on loading curve control according to claim 1, characterized in that, The historical test samples meet the following conditions: the historical workpieces corresponding to each historical test sample have the same sealing flange connection area structure, sealing material type, hydraulic loading equipment, road fatigue loading curve and sealing pre-pressure simulation loading curve as the current battery pack under test.

3. The hydraulic fatigue testing method for automotive structural components based on loading curve control according to claim 1, characterized in that, The specific calculation process for the continuity characteristic value of the sealing indentation includes: Based on historical test samples, within a preset time period after the start of the simulated pre-pressure loading curve, images of sealing indentations formed along the sealing path in the sealing flange connection area are collected; wherein, the sealing indentation image is an image of the indentation distribution formed by the seal in the sealing flange connection area under pre-pressure, and the indentation distribution image includes at least the indentation area, the non-indentation area, and the indentation boundary. The image of the sealing indentation is preprocessed, and the center line of the sealing path is extracted. The sealing path is then divided into several detection segments according to the center line of the sealing path. Identify the effective indentation area in each detection segment, and obtain the indentation width, indentation grayscale, and indentation boundary position corresponding to each detection segment; The indentation width dispersion is calculated based on the indentation width corresponding to each detection segment, the indentation grayscale dispersion is calculated based on the indentation grayscale corresponding to each detection segment, and the indentation interruption length and indentation center offset are determined based on the indentation boundary position corresponding to each detection segment. The continuity characteristic value of the sealing indentation is determined based on the dispersion of the indentation width, the dispersion of the indentation grayscale, the length of the indentation interruption, and the offset of the indentation center; wherein the continuity characteristic value of the sealing indentation is negatively correlated with the dispersion of the indentation width, the dispersion of the indentation grayscale, the length of the indentation interruption, and the offset of the indentation center.

4. The hydraulic fatigue testing method for automotive structural components based on loading curve control according to claim 1, characterized in that, The specific calculation process for the response matching degree includes: Obtain flange sealing test response data generated during hydraulic fatigue testing of the sealing flange connection area of ​​the lower housing of the battery pack corresponding to each historical test sample; wherein, the flange sealing test response data includes at least one of the following: sealing cavity pressure attenuation, sealing surface opening and closing amount, flange local residual deformation amount, and leakage rate change amount. Obtain the actual vehicle service sealing response benchmark data corresponding to each historical test sample; wherein, the actual vehicle service sealing response benchmark data is the flange sealing response data obtained by the lower housing of the qualified battery pack of the corresponding batch under actual vehicle service conditions; Calculate the response deviation between the flange seal test response data and the actual vehicle service seal response benchmark data; The response fit is determined based on the response deviation; wherein, the smaller the response deviation, the higher the response fit.

5. The hydraulic fatigue testing method for automotive structural components based on loading curve control according to claim 1, characterized in that, The steps for establishing the relationship curve between the continuity characteristic value of the sealing indentation and the response consistency, and determining the continuity characteristic value of the sealing indentation corresponding to the stable range of the response consistency as the benchmark value, include: Several historical test samples are sorted from smallest to largest according to the continuity characteristic value of the sealing indentation to obtain a sample sequence, and the response consistency of each historical test sample in the sample sequence is extracted to establish the relationship curve between the continuity characteristic value of the sealing indentation and the response consistency. Analyze the relationship curve to determine whether the response fit first increases and then tends to stabilize as the characteristic value of the continuity of the sealing indentation increases; If so, then identify the inflection point corresponding to when the response matching degree enters the stable range from the rising state, and determine the seal indentation continuity characteristic value corresponding to the inflection point as the benchmark value; The stable interval is defined as the interval formed by the change in the response consistency between adjacent historical test samples being less than a preset change threshold and continuously satisfying a preset number of historical test samples.

6. The hydraulic fatigue testing method for automotive structural components based on loading curve control according to claim 3, characterized in that, The steps of obtaining the current seal indentation continuity characteristic value and generating a loading curve correction factor based on the deviation difference when it is lower than the reference value, in order to weaken and correct the preset seal preload simulation loading curve, include: Obtain the continuity characteristic value of the sealing indentation in the sealing flange connection area of ​​the lower housing of the battery pack under test; Determine whether the continuity characteristic value of the sealing indentation on the lower casing of the current battery pack under test is lower than the reference value; If the continuity characteristic value of the sealing indentation of the lower housing of the current battery pack under test is not lower than the benchmark value, then the preset sealing pre-compression simulation loading curve remains unchanged. If the continuity characteristic value of the sealing indentation of the lower housing of the current battery pack under test is lower than the reference value, then a loading curve correction factor is generated based on the decrease of the continuity characteristic value of the sealing indentation of the lower housing of the current battery pack under test relative to the reference value, and in conjunction with a preset correction strength coefficient. The preset sealing pre-compression simulation loading curve is weakened and corrected based on the loading curve correction factor.

7. The hydraulic fatigue testing method for automotive structural components based on loading curve control according to claim 6, characterized in that, The continuity characteristic value of the sealing indentation of the lower housing of the current battery pack under test is determined by the sealing indentation image of the lower housing of the current battery pack under test acquired within a preset time period after the start of the sealing pre-pressure simulation loading curve.

8. The hydraulic fatigue testing method for automotive structural components based on loading curve control according to claim 6, characterized in that, The sealing preload simulation loading curve is a time-pressure curve used to simulate the sealing preload pressure experienced by the sealing flange connection area of ​​the lower housing of the battery pack under the assembled and tightened state. The simulated loading curve for sealing pre-pressure includes pre-pressure amplitudes corresponding to multiple time points; the weakening correction is based on the loading curve correction factor, reducing the pre-pressure amplitude corresponding to each time point in the simulated loading curve for sealing pre-pressure by the same correction ratio, so that the corrected simulated loading curve for sealing pre-pressure shifts downward as a whole relative to the uncorrected simulated loading curve for sealing pre-pressure, while maintaining the original loading sequence and curve change trend unchanged.

9. The hydraulic fatigue testing method for automotive structural components based on loading curve control according to claim 8, characterized in that, The preset sealing preload simulation loading curve is weakened and corrected based on the loading curve correction factor using a preset correction function, which includes: The correction function includes: ； in, This refers to the simulated loading curve for the corrected seal preload at time [time missing]. The corresponding preload amplitude, This refers to the simulated loading curve of the seal preload before correction at time [time value missing]. The corresponding preload amplitude, This refers to the lower limit of the preload amplitude. This refers to the current characteristic value of the seal indentation continuity. This refers to the baseline value. This refers to the rate of decline. This refers to a preset correction strength coefficient, and satisfies... Greater than 0, This refers to the correction factor; The lower limit of the pre-pressure amplitude is obtained by reducing the initial pre-pressure amplitude at the corresponding time according to a preset maximum reduction ratio, so that the pre-pressure amplitude of the corrected sealing pre-pressure simulation loading curve at any time is not lower than the lower limit of the pre-pressure amplitude at that time.

10. A hydraulic fatigue testing system for automotive structural components based on loading curve control, characterized in that, The system includes: The sample extraction module is used to retrieve historical test samples from the historical test database before performing hydraulic fatigue testing on the sealing flange connection area of ​​the lower housing of the current battery pack under test, and extract historical test samples that use the same preset sealing pre-pressure simulation loading curve but correspond to different production batches. The parameter acquisition module is used to acquire the continuous characteristic value of the sealing indentation and the response consistency of each historical test sample. The continuous characteristic value of the sealing indentation is determined by the sealing indentation image acquired after the start of the historical test, and the response consistency is determined by the deviation between the flange sealing test response and the sealing reference of the actual vehicle in service. The benchmark determination module is used to establish the relationship curve between the continuity characteristic value of the sealing indentation and the response matching degree, and to determine the continuity characteristic value of the sealing indentation corresponding to the stable range of the response matching degree as the benchmark value; The curve correction module is used to obtain the current seal indentation continuity characteristic value, and when it is lower than the reference value, it generates a loading curve correction factor according to the difference between the two, so as to weaken and correct the preset seal pre-pressure simulation loading curve. The fatigue testing module is used to overlay the corrected sealed preload simulation loading curve with the road fatigue loading curve to perform hydraulic fatigue testing on the lower shell of the battery pack under test.

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