An online detection method for compression and rebound performance of elastic gasket

Abstract

The application discloses an elastic gasket compression resilience performance online detection method, and belongs to the technical field of elastic gasket performance detection. The method obtains real-time pressure values and displacement values in continuous multiple times of loading compression and unloading resilience processes, and constructs a pressure-displacement hysteresis loop sequence; extracts starting displacement of each time of loading and unloading resilience termination displacement, and calculates a displacement valley value sequence; identifies compression permanent deformation accumulation according to adjacent displacement valley value difference change trends; adopts the accumulation to perform coordinate translation correction on the unloading resilience branch, and obtains a corrected resilience branch sequence; extracts starting section and termination section tangent lines from the corrected resilience branch sequence, calculates an included angle change amount, and obtains a resilience response hysteresis angle; and calculates compression resilience performance online detection results by using the hysteresis angle and the accumulation. The method can synchronously analyze compression permanent deformation accumulation and resilience response hysteresis.

Description

Technical Field

[0001] This invention relates to the field of elastic gasket performance testing technology, specifically to an online testing method for the compression and rebound performance of elastic gaskets. Background Technology

[0002] The permanent compression deformation and hysteresis rebound response of elastic gaskets during continuous loading, compression, and unloading directly affect the reliability of the sealing connection. Current methods for testing the compression and rebound performance of elastic gaskets typically involve single or limited loading and unloading cycles using a material testing machine, recording the pressure-displacement curve, and evaluating offline using indicators such as hysteresis loop area, permanent compression deformation rate, and rebound rate. Some online testing methods synchronously acquire pressure and displacement signals for a single cycle, then manually select feature points to calculate the rebound amount. Under continuous loading, compression, unloading, and rebound conditions, the unloading rebound branch shifts within the pressure-displacement hysteresis loop as permanent deformation accumulates. The absolute positions of the rebound initiation and termination displacements change sequentially, and the displacement reference in the original pressure-displacement data becomes unstable. Existing offline or single-cycle analysis methods struggle to process continuous cyclic data online and cannot identify the changing trends of displacement valleys between adjacent cycles in real time, resulting in the inaccurate acquisition of the accumulated permanent compression deformation from the continuous hysteresis loop sequence. The characterization of rebound response hysteresis still largely relies on the original hysteresis loop area or a single slope, failing to separate the displacement caused by permanent deformation from the rebound branch. This couples the rebound response hysteresis with the permanent deformation, making it difficult to obtain independent rebound response hysteresis information. When gaskets are used in sealing parts that withstand continuous compression rebound, the above offline or single-test results are insufficient to reflect the changes in compression rebound performance after multiple cycles under actual working conditions. Summary of the Invention

[0003] To address the problems of existing offline single-analysis methods for testing the compression and rebound performance of elastic gaskets, which are difficult to adapt to continuous cyclic working conditions and cannot simultaneously separate the accumulation of permanent compression deformation and the lag in rebound response, this invention discloses an online method for testing the compression and rebound performance of elastic gaskets. This method processes real-time pressure and displacement values ​​during multiple consecutive loading, compression, unloading, and rebound processes online, identifies the accumulated amount of permanent compression deformation, corrects the unloading rebound branch, and extracts the rebound response lag angle, thereby achieving online testing of the compression and rebound performance of elastic gaskets.

[0004] To achieve the above objectives, the present invention provides the following technical solution: The present invention provides an online detection method for the compression and rebound performance of an elastic gasket. This method simultaneously acquires real-time pressure and displacement values ​​during multiple consecutive loading, compression, and unloading rebound processes, and constructs a pressure-displacement hysteresis loop sequence from the real-time data. Based on the pressure-displacement hysteresis loop sequence, the compression initiation displacement at each loading start point and the rebound termination displacement at each unloading end point are extracted to calculate a displacement valley value sequence. The cumulative compression permanent deformation of the elastic gasket under test within the current compression and rebound cycle is identified based on the trend of the difference between adjacent displacement valley values ​​in the displacement valley value sequence. The cumulative compression permanent deformation is used to perform coordinate translation correction on the unloading rebound branch in the pressure-displacement hysteresis loop sequence to obtain a corrected rebound branch sequence. The tangents of the rebound initiation segment and the rebound termination segment are extracted from the corrected rebound branch sequence, and the change in the angle between the two tangents is calculated to obtain the rebound response hysteresis angle. The online detection result of the compression and rebound performance of the elastic gasket under test is calculated using the rebound response hysteresis angle and the cumulative compression permanent deformation. This method acquires pressure-displacement data online and corrects and extracts features from the hysteresis loop, which can comprehensively reflect the deformation accumulation and rebound response hysteresis characteristics of the elastic gasket, thereby improving the real-time performance and accuracy of online detection.

[0005] Preferably, the process of constructing the pressure-displacement hysteresis loop sequence includes: synchronously acquiring multiple first pressure sampling points and multiple first displacement sampling points during the loading and compression phase, and multiple second pressure sampling points and multiple second displacement sampling points during the unloading and rebound phase, according to a preset sampling frequency; combining the multiple first pressure sampling points and multiple first displacement sampling points acquired during the same loading and compression phase according to a one-to-one correspondence in sampling time sequence to obtain a loading branch sequence; combining the multiple second pressure sampling points and multiple second displacement sampling points acquired during the same unloading and rebound phase according to a one-to-one correspondence in sampling time sequence to obtain a rebound branch sequence; and splicing the loading branch sequence and rebound branch sequence of the same compression and rebound cycle in a head-to-tail manner to obtain the pressure-displacement hysteresis loop sequence. Synchronous acquisition and head-to-tail splicing enable the hysteresis loop sequence to completely reflect the loading and rebound path of each compression and rebound cycle.

[0006] Preferably, the process of calculating the displacement valley value sequence includes: traversing the starting point of the loading branch sequence in the pressure-displacement hysteresis loop sequence, and reading the displacement coordinate value corresponding to the starting point as the compression initiation displacement of the current compression-rebound cycle; traversing the ending point of the rebound branch sequence in the pressure-displacement hysteresis loop sequence, and reading the displacement coordinate value corresponding to the ending point as the rebound termination displacement of the current compression-rebound cycle; calculating the difference between the compression initiation displacement and the rebound termination displacement of the same compression-rebound cycle to obtain the displacement valley value of that cycle; arranging the displacement valley values ​​of all cycles according to the chronological order of the compression-rebound cycles to obtain the displacement valley value sequence. This valley value sequence can reflect the positional change of the rebound endpoint of each cycle, providing a stable basis for cumulative deformation identification.

[0007] Preferably, the process of identifying the cumulative amount of compression set includes: subtracting the previous displacement valley value from the next displacement valley value in the displacement valley value sequence to obtain a valley value difference sequence; extracting the valley value differences with positive values ​​from the valley value difference sequence to form a positive difference subsequence; accumulating the values ​​of all valley value differences in the positive difference subsequence to obtain the total cumulative positive difference, and using the total cumulative positive difference as the cumulative amount of compression set within the current compression rebound cycle. Accumulating only the positive differences avoids negative interference from rebound fluctuations and improves the accuracy of identifying the cumulative amount of compression set.

[0008] As a technical solution of the present invention, the process of coordinate translation correction for the unloading rebound branch includes: extracting all rebound sampling points on the unloading rebound branch of the current compression rebound cycle from the pressure-displacement hysteresis loop sequence, each rebound sampling point containing rebound pressure coordinate values ​​and rebound displacement coordinate values; subtracting the accumulated amount of permanent compression deformation from the rebound displacement coordinate value of each rebound sampling point to obtain the corrected displacement coordinate value; keeping the rebound pressure coordinate value of each rebound sampling point unchanged, recombining the corrected displacement coordinate value and the rebound pressure coordinate value to obtain the corrected rebound sampling point; arranging all the corrected rebound sampling points in chronological order to obtain the corrected rebound branch sequence. Coordinate translation correction can eliminate the overall offset of the rebound curve caused by the accumulation of permanent deformation, enabling rebound feature extraction to be performed under a unified benchmark.

[0009] As a technical solution of the present invention, the process of obtaining the rebound response hysteresis angle includes: extracting the first N corrected rebound sampling points of the rebound initiation segment from the corrected rebound branch sequence, performing linear fitting on the first N corrected rebound sampling points to obtain the tangent slope of the rebound initiation segment; extracting the last M corrected rebound sampling points of the rebound termination segment from the corrected rebound branch sequence, performing linear fitting on the last M corrected rebound sampling points to obtain the tangent slope of the rebound termination segment; calculating the included angle between the two tangents based on the tangent slope of the rebound initiation segment and the tangent slope of the rebound termination segment; and subtracting a preset standard included angle value from the included angle value to obtain the rebound response hysteresis angle. This rebound response hysteresis angle can sensitively characterize the response difference of the elastic gasket between the initial and final stages of rebound. Preferably, the preset standard included angle value is the included angle value between the two tangents calculated during the first compression rebound cycle of the elastic gasket under test.

[0010] In one implementation, the process of calculating the online detection result using the rebound response hysteresis angle and the cumulative amount of compression set includes: comparing the rebound response hysteresis angle with a preset hysteresis angle threshold; when the rebound response hysteresis angle is greater than the preset hysteresis angle threshold, it is determined that the compression rebound response hysteresis is out of tolerance; comparing the cumulative amount of compression set with a preset cumulative amount of deformation threshold; when the cumulative amount of compression set is greater than the preset cumulative amount of deformation threshold, it is determined that the compression set is out of tolerance; when either the compression rebound response hysteresis is out of tolerance or the compression set is out of tolerance, a detection result indicating that the compression rebound performance is unqualified is output.

[0011] In another implementation, the process of calculating the online detection result using the rebound response hysteresis angle and the cumulative amount of compression set includes: reading the historical rebound response hysteresis angle and the historical cumulative amount of compression set obtained from the previous compression rebound cycle; subtracting the historical rebound response hysteresis angle from the rebound response hysteresis angle of the current compression rebound cycle to obtain the hysteresis angle change rate; subtracting the historical cumulative amount of compression set from the cumulative amount of compression set of the current compression rebound cycle to obtain the deformation accumulation change rate; and outputting the detection result of the compression rebound performance degradation trend when both the hysteresis angle change rate and the deformation accumulation change rate are greater than their respective preset change rate thresholds.

[0012] Preferably, the preset hysteresis angle threshold and the preset cumulative deformation threshold are dynamically adjusted according to the material type and thickness specifications of the elastic gasket to be tested, so as to adapt to the testing requirements of different elastic gaskets.

[0013] The technical effects and advantages provided by the present invention in the above technical solution are as follows: The compression initiation displacement at the start of each loading cycle and the rebound termination displacement at the end of each unloading cycle are extracted from a series of consecutive pressure-displacement hysteresis loops. The difference between the compression initiation displacement and the rebound termination displacement of the same compression-rebound cycle is calculated to obtain a displacement valley sequence. The cumulative amount of compression permanent deformation within the current compression-rebound cycle is identified based on the changing trend of the difference between adjacent displacement valleys. The identified cumulative amount of compression permanent deformation is used for coordinate translation correction of the unloading-rebound branch. For each corrected rebound sampling point, the rebound pressure coordinate value remains unchanged, and the cumulative amount of compression permanent deformation is subtracted from the rebound displacement coordinate value to form the corrected rebound branch sequence. After deducting the overall offset of the unloading-rebound branch caused by the accumulation of compression permanent deformation, the corrected rebound branch corresponds to the loading branch under the same displacement reference, avoiding interference from the permanent deformation offset in the original pressure-displacement hysteresis loop on the rebound feature extraction. This method dynamically identifies the changes in displacement valleys in consecutive cycles and uses the identified cumulative amount as a correction amount in the rebound branch reconstruction, making the rebound displacement data more realistically reflect the changes in the elastic recovery part, rather than mixing the plastic deformation offset into the rebound response analysis. In the corrected rebound branch sequence, the first N corrected rebound sampling points of the rebound initiation segment and the last M corrected rebound sampling points of the rebound termination segment are extracted. Linear fitting is then performed to obtain the tangent slopes of the rebound initiation and termination segments. The change in the angle between the two tangents is calculated based on these two slopes to obtain the rebound response hysteresis angle. Since the corrected rebound branch involved in the angle calculation has eliminated the displacement offset caused by compression set, the change in the tangent angle mainly reflects the difference in path direction between the rebound initiation and termination segments, thus characterizing the degree of hysteresis in the rebound response at the beginning and end stages. Combining the rebound response hysteresis angle with the cumulative amount of compression set for performance testing in the current compression-rebound cycle can simultaneously identify the accumulation of plastic deformation and dynamic response hysteresis of the gasket during multiple consecutive loading, compression, and unloading rebound processes. This reduces misjudgments caused by the coupling of these two factors, resulting in online testing results of compression-rebound performance that better reflect actual continuous working conditions. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0015] Figure 1 This is a flowchart of an online testing method for the compression resilience of elastic gaskets; Figure 2 This is a flowchart for constructing the pressure-displacement hysteresis loop sequence of an elastic gasket; Figure 3 This is a flowchart for calculating the hysteresis angle of the elastic gasket's rebound response; Figure 4 This is a schematic diagram of a series of pressure-displacement hysteresis loops in multiple consecutive compression and rebound cycles. Figure 5 These are the displacement valley sequence and the curves showing the variation of cumulative compressive permanent deformation with the compression-rebound cycle; Figure 6 This is a schematic diagram of the compression-rebound branch correction of the elastic gasket; Figure 7 This is a schematic diagram of the first compression and rebound cycle correction, including the rebound branch and the tangent of the start and end segments. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] See Figure 1 This invention provides an online detection method for the compression and rebound performance of an elastic gasket, comprising: acquiring real-time pressure and displacement values ​​of the elastic gasket under test during multiple consecutive loading, compression, unloading, and rebound processes, and constructing a pressure-displacement hysteresis loop sequence; based on the pressure-displacement hysteresis loop sequence, extracting the compression initiation displacement at the start point of each loading and the rebound termination displacement at the end point of each unloading, and calculating a displacement valley value sequence; identifying the cumulative amount of compression permanent deformation of the elastic gasket under test in the current compression and rebound cycle based on the trend of the difference between adjacent displacement valley values ​​in the displacement valley value sequence; using the cumulative amount of compression permanent deformation to perform coordinate translation correction on the unloading rebound branch in the pressure-displacement hysteresis loop sequence, and obtaining a corrected rebound branch sequence; extracting the tangent of the rebound initiation segment and the tangent of the rebound termination segment from the corrected rebound branch sequence, calculating the change in the angle between the two tangents, and obtaining the rebound response hysteresis angle; and using the rebound response hysteresis angle and the cumulative amount of compression permanent deformation to calculate the online detection result of the compression and rebound performance of the elastic gasket under test.

[0018] In specific implementation, please refer to Figure 2 The real-time pressure and displacement values ​​of the elastic gasket under test are obtained during the continuous loading, compression, unloading, and rebound processes, and a pressure-displacement hysteresis loop sequence is constructed.

[0019] In practice, multiple first pressure sampling points and multiple first displacement sampling points are synchronously acquired during the loading and compression phase, and multiple second pressure sampling points and multiple second displacement sampling points are acquired during the unloading and rebound phase, according to a preset sampling frequency. The preset sampling frequency is determined based on the highest frequency components of the displacement signal and the pressure signal during the compression and rebound process of the elastic gasket, and the preset sampling frequency is not less than twice the larger of the highest frequency components of the displacement signal and the pressure signal. The pressure sensor and the displacement sensor are triggered by the same sampling clock and acquire pressure and displacement values ​​respectively at the same sampling moment. During the loading and compression phase, one first pressure sampling point and one first displacement sampling point are acquired at each sampling moment; during the unloading and rebound phase, one second pressure sampling point and one second displacement sampling point are acquired at each sampling moment.

[0020] In practice, multiple first pressure sampling points and multiple first displacement sampling points collected during the same loading and compression phase are combined one-to-one according to their sampling time sequence to obtain a loading branch sequence. The one-to-one combination method is as follows: for the same loading and compression phase, first pressure sampling points and first displacement sampling points with the same sampling sequence number form a loading sampling point. The x-axis of the loading sampling point represents the displacement value of the first displacement sampling point, and the y-axis represents the pressure value of the first pressure sampling point. All loading sampling points are arranged according to their sampling time sequence to form the loading branch sequence.

[0021] In practice, multiple second pressure sampling points and multiple second displacement sampling points collected during the same unloading and rebound phase are combined one-to-one according to the sampling time sequence to obtain a rebound branch sequence. The one-to-one combination method is as follows: for the same unloading and rebound phase, second pressure sampling points and second displacement sampling points with the same sampling sequence number form a rebound sampling point. The x-axis of the rebound sampling point represents the displacement value of the second displacement sampling point, and the y-axis represents the pressure value of the second pressure sampling point. All rebound sampling points are arranged according to the sampling time sequence to form the rebound branch sequence.

[0022] In practice, the loading branch sequence and the rebound branch sequence of the same compression-rebound cycle are concatenated end-to-end to obtain a pressure-displacement hysteresis loop sequence. The end-to-end connection is achieved by connecting the last loading sampling point of the loading branch sequence to the first rebound sampling point of the rebound branch sequence. After concatenation, the pressure-displacement hysteresis loop sequence consists of all loading sampling points from the loading branch sequence and all rebound sampling points from the rebound branch sequence, arranged in the order from the loading stage to the rebound stage. Multiple consecutive compression-rebound cycles are processed by obtaining the loading branch sequence and the rebound branch sequence of the same compression-rebound cycle and concatenating them together to obtain multiple corresponding pressure-displacement hysteresis loop sequences.

[0023] It can be understood that in the pressure-displacement hysteresis loop sequence, the loading branch sequence and the rebound branch sequence form a closed loop trajectory, corresponding to one compression-rebound cycle.

[0024] In some embodiments, the preset sampling frequency is set between 100Hz and 10kHz. As the compression and rebound speed of the elastic gasket increases, the preset sampling frequency increases accordingly, ensuring that the displacement changes during the loading compression and unloading rebound phases are fully recorded by the sampling points. Optionally, the preset sampling frequency is set to 2000Hz, suitable for situations where the elastic gasket completes one loading compression and unloading rebound cycle within 0.1s to 1s.

[0025] See Figure 4 In the graph, the horizontal axis represents the displacement value of the elastic gasket, and the vertical axis represents the pressure value. The curves consist of solid and dashed lines; the solid lines represent the loading branch sequence, and the dashed lines represent the unloading and rebound branch sequence. The legend shows that the 1st to 6th compression-rebound cycles are distinguished by different colors, and the curves are arranged sequentially according to the compression-rebound cycle order.

[0026] As shown in the figure, with the increase of the compression-rebound cycle, the loading branch curve shifts to the lower right, indicating that the initial displacement of compression at the loading start point gradually increases, and the displacement range corresponding to the pressure value also expands. The unloading-rebound branch curve also shows a rightward shift, and the start point of the rebound branch is connected to the end point of the loading branch, forming a closed pressure-displacement hysteresis loop. Each hysteresis loop corresponds to a complete compression-rebound cycle.

[0027] From the first to the sixth compression-rebound cycle, the hysteresis loop area decreases overall, indicating a change in the compression-rebound performance of the elastic gasket. The initial displacement of the unloading-rebound branch shifts significantly to the right, reflecting the cumulative amount of permanent compression deformation generated by the elastic gasket during continuous loading and unloading, which is consistent with the displacement coordinate translation correction description of the unloading-rebound branch in the pressure-displacement hysteresis loop sequence in this embodiment.

[0028] Furthermore, the unloading rebound branch exhibits different slopes at the rebound initiation and rebound termination points, consistent with the linear fitting of the sampling points at the rebound initiation and rebound termination points in this embodiment to calculate the tangent slope. The changing angle between the loading and unloading rebound branches as the cycle increases indicates a change in the rebound response hysteresis angle, reflecting the degree of hysteresis in the elastic gasket's rebound response.

[0029] In specific implementation, when extracting the displacement valley sequence based on the pressure-displacement hysteresis loop sequence, the starting point of each loading branch sequence in the pressure-displacement hysteresis loop sequence is traversed. The starting point of the loading branch sequence is the loading sampling point with the smallest sampling sequence number in the loading branch sequence. The displacement coordinate value corresponding to the starting point of the loading branch sequence is read as the compression starting displacement of this compression-rebound cycle. The displacement coordinate value is the x-coordinate of the starting point of the loading branch sequence.

[0030] In practice, the termination point of each rebound branch sequence in the pressure-displacement hysteresis loop sequence is traversed. The termination point of the rebound branch sequence is the rebound sampling point with the largest sampling sequence number in the rebound branch sequence. The displacement coordinate value corresponding to the termination point of the rebound branch sequence is read as the rebound termination displacement of this compression-rebound cycle. The displacement coordinate value is the x-coordinate of the termination point of the rebound branch sequence.

[0031] Subtract the compression start displacement from the rebound termination displacement of the same compression rebound cycle to obtain the displacement trough value of the same compression rebound cycle. The displacement trough value represents the amount of displacement that the elastic gasket cannot recover after unloading and rebounding in the same compression rebound cycle. For the first... One compression-rebound cycle, displacement valley value It is obtained using the following formula: in, Indicates the first Displacement valley value per compression-rebound cycle Indicates the first The springback termination displacement of one compression-springback cycle Indicates the first The compression initiation displacement of one compression-rebound cycle, This is the sequence number of the compression and rebound cycle. Take a positive integer.

[0032] Arrange the displacement valley values ​​of all compression and rebound cycles in chronological order to obtain a displacement valley value sequence. Each element in the displacement valley value sequence corresponds to one compression and rebound cycle.

[0033] In practice, when identifying the cumulative amount of permanent compression deformation of the elastic gasket under test within the current compression-rebound cycle, the previous displacement valley value is subtracted from the next displacement valley value in the displacement valley value sequence to obtain a valley value difference sequence. Each difference in the valley value difference sequence corresponds to the change in displacement valley value between two adjacent compression-rebound cycles.

[0034] Positive valley difference values ​​are extracted from the valley difference sequence to form a positive difference subsequence. The positive difference subsequence only contains valley differences greater than zero. Negative valley differences and zero valley differences are not included in the positive difference subsequence.

[0035] The total cumulative positive difference is obtained by summing the values ​​of all valley differences in the positive difference subsequence. The total cumulative positive difference is the algebraic sum of all valley differences in the positive difference subsequence. Since all valley differences in the positive difference subsequence are positive, the total cumulative positive difference is the sum of the values ​​of all valley differences in the positive difference subsequence.

[0036] The total cumulative positive difference is taken as the cumulative amount of compression permanent deformation within the current compression rebound cycle. The current compression rebound cycle is the compression rebound cycle corresponding to the last displacement valley value in the displacement valley value sequence.

[0037] It can be understood that when adjacent displacement valley values ​​in the displacement valley value sequence increase, the difference between the next displacement valley value and the previous displacement valley value is positive, indicating that a new cumulative amount of compressive permanent deformation is generated between adjacent cycles. By summing all the positive differences, the total cumulative amount of compressive permanent deformation in each compression and rebound cycle can be obtained.

[0038] In some embodiments, when the positive difference subsequence is empty, the total accumulated positive difference is zero, and the accumulated amount of compression permanent deformation in the current compression rebound cycle is zero.

[0039] In specific implementation, the displacement valley value sequence and the valley value difference sequence are stored in the form of an array or a list, and the array number corresponds to the compression rebound cycle number.

[0040] In some embodiments, the number of elements in the displacement valley sequence is the same as the number of compression-rebound cycles in the pressure-displacement hysteresis loop sequence.

[0041] See Figure 5 In the figure, the horizontal axis represents the sequence number of the continuous compression and rebound cycle, ranging from 0 to about 500. The left side of the vertical axis corresponds to the blue solid curve, which represents the displacement valley sequence, and the right side of the vertical axis corresponds to the red dashed curve, which represents the cumulative amount of compression permanent deformation. The two curves closely overlap and show a step-up trend.

[0042] As shown in the figure, the displacement trough sequence and the cumulative amount of compressive permanent deformation gradually increase with the increase of the compression-rebound cycle number, indicating that the irreversible deformation of the elastic gasket gradually accumulates during continuous compression-rebound. In the initial stage (from 0 to about 100 cycles), both curves rise rapidly, indicating that the elastic gasket has undergone significant permanent deformation accumulation; in the middle stage (from about 100 to about 360 cycles), the growth rate slows down, and the displacement trough and permanent deformation accumulation tend to stabilize, showing that the deformation of the elastic gasket tends to stabilize; in the later stage (from about 360 to about 500 cycles), a slow stepwise increase occurs again, indicating that the elastic gasket continues to accumulate a small amount of compressive permanent deformation. The displacement trough sequence and the cumulative amount of compressive permanent deformation curve in the figure highly overlap, which is consistent with the method of calculating the cumulative amount of compressive permanent deformation by positive accumulation of the displacement trough differences in this embodiment.

[0043] In specific implementation, please refer to Figure 3 The cumulative compression permanent deformation is used to perform coordinate translation correction on the unloading rebound branch in the pressure-displacement hysteresis loop sequence. All rebound sampling points on the unloading rebound branch of the current compression rebound cycle are extracted from the pressure-displacement hysteresis loop sequence. Each rebound sampling point contains rebound pressure coordinates and rebound displacement coordinates. The rebound pressure coordinate is the ordinate of the rebound sampling point, and the rebound displacement coordinate is the abscissa of the rebound sampling point.

[0044] Subtract the accumulated compression set from the rebound displacement coordinate value of each rebound sampling point to obtain the corrected displacement coordinate value. The corrected displacement coordinate value is the displacement coordinate value of the rebound sampling point in the displacement direction after eliminating the influence of compression set. Keeping the rebound pressure coordinate value of each rebound sampling point unchanged, recombine the corrected displacement coordinate value and the rebound pressure coordinate value to obtain the corrected rebound sampling point. The x-coordinate of the corrected rebound sampling point is the corrected displacement coordinate value, and the y-coordinate of the corrected rebound sampling point is the rebound pressure coordinate value.

[0045] Arrange all corrected springback sampling points according to the sampling time sequence to obtain the corrected springback branch sequence. Each corrected springback sampling point in the corrected springback branch sequence corresponds one-to-one with the original springback sampling point, with only the magnitude of the cumulative compressive permanent deformation shifted in the displacement direction.

[0046] In specific implementation, the first N corrected rebound sampling points of the rebound initiation segment are extracted from the corrected rebound branch sequence. The corrected rebound branch sequence is a set of corrected rebound sampling points arranged in chronological order. Starting from the first corrected rebound sampling point in the corrected rebound branch sequence, N corrected rebound sampling points are continuously extracted as the first N corrected rebound sampling points of the rebound initiation segment. The value of N is 5% of the total number of corrected rebound sampling points in the corrected rebound branch sequence. The value of N is based on the fact that the first 5% of the sampling points in the initial stage of elastic gasket unloading rebound are located in the rebound initiation linear segment, and the rebound pressure coordinate value and the corrected displacement coordinate value satisfy an approximately linear relationship within this linear segment.

[0047] The last M corrected rebound sampling points of the rebound termination segment are extracted from the corrected rebound branch sequence. Starting from the last corrected rebound sampling point of the corrected rebound branch sequence, M corrected rebound sampling points are continuously extracted forward as the last M corrected rebound sampling points of the rebound termination segment. The value of M is 5% of the total number of corrected rebound sampling points in the corrected rebound branch sequence. The value of M is based on the fact that the last 5% of sampling points in the elastic gasket unloading rebound termination stage are located in the rebound termination linear segment, and the rebound pressure coordinate value and the corrected displacement coordinate value satisfy an approximately linear relationship within this linear segment.

[0048] Optionally, when the value obtained by multiplying the total number of corrected rebound sampling points in the corrected rebound branch sequence by 5% is not an integer, both N and M shall take the integer part of the value.

[0049] In practice, linear fitting is performed on the first N corrected rebound sampling points to obtain the slope of the tangent line in the rebound initiation segment. The linear fitting uses the least squares method, with the corrected displacement coordinates as the independent variable and the rebound pressure coordinates as the dependent variable, to obtain a linear straight line. The slope of the fitted line is the slope of the tangent line in the rebound initiation segment. Linear fitting is then performed on the next M corrected rebound sampling points to obtain the slope of the tangent line in the rebound termination segment. The linear fitting also uses the least squares method, with the corrected displacement coordinates as the independent variable and the rebound pressure coordinates as the dependent variable, to obtain a linear straight line. The slope of the fitted line is the slope of the tangent line in the rebound termination segment. The specific value of the tangent line slope in the rebound initiation segment is calculated from the corrected displacement coordinates and rebound pressure coordinates of the first N corrected rebound sampling points using least squares fitting. The specific value of the tangent line slope in the rebound termination segment is calculated from the corrected displacement coordinates and rebound pressure coordinates of the next M corrected rebound sampling points using least squares fitting.

[0050] Calculate the angle between the two tangents based on the slopes of the tangents at the beginning and end of the rebound segment. It is obtained using the following formula: in, It represents the angle between two tangents, in radians, which can be converted to degrees. The slope of the tangent at the beginning of the rebound is obtained by linear fitting of the first N corrected rebound sampling points; The slope of the tangent at the end of the rebound segment is obtained by linear fitting of the last M corrected rebound sampling points; and All are dimensionless slope values.

[0051] Subtract a preset standard angle value from the angle value to obtain the rebound response hysteresis angle. The preset standard angle value is the angle between two tangents calculated during the first compression and rebound cycle of the elastic gasket under test. The angle between the two tangents during the first compression and rebound cycle is calculated in the same way as the current compression and rebound cycle.

[0052] It is understandable that the corrected rebound branch sequence eliminates the rebound displacement offset caused by the cumulative amount of compression permanent deformation. The angle between the tangent of the rebound initiation segment and the tangent of the rebound termination segment reflects the symmetry of the elastic gasket's response during the rebound process. The difference between the angle value and the preset standard angle value reflects the degree of rebound response hysteresis.

[0053] See Figure 6 The figure illustrates the unloading and rebound branch correction process and its linear fitting tangent result for the current compression and rebound cycle of the elastic gasket in this embodiment. The horizontal axis represents the corrected displacement coordinate value, and the vertical axis represents the rebound pressure coordinate value; both coordinates are dimensionless scale values. The gray dashed line in the figure represents the original unloading and rebound branch sequence, showing the actual trajectory of pressure changing with displacement during the rebound process; the green solid line represents the corrected rebound branch sequence after the original rebound branch has been corrected by shifting the displacement coordinate based on the accumulated permanent compression deformation. The corrected curve is shifted to the left overall, eliminating the displacement offset caused by permanent deformation.

[0054] The orange dashed line in the figure represents the tangent line of the initial segment obtained by linear fitting of the first 5% of the sampling points from the corrected rebound branch sequence. The slope of this tangent line reflects the linear characteristics of the pressure-displacement relationship in the early stage of the unloading rebound process. The purple dotted line represents the tangent line of the linear fitting termination segment of the last 5% of the sampling points in the rebound termination segment, reflecting the pressure-displacement relationship at the end of the unloading rebound process. The number of sampling points for both tangent lines is 5% of the total number of corrected rebound sampling points, ensuring that the fitting results accurately reflect the linear characteristics of the corresponding stages.

[0055] As shown in the figure, the corrected rebound branch sequence and the original rebound branch sequence exhibit similar trends in the pressure-displacement space, but the overall displacement value of the corrected curve is reduced, indicating that the positional shift of the rebound curve is effectively corrected by subtracting the accumulated amount of compressive permanent deformation. The tangent of the initial segment is located in the lower left region, and the tangent of the final segment is located in the upper right region. A certain angle is formed between the two tangents, which reflects the response hysteresis characteristics during the rebound process.

[0056] In specific implementation, when calculating the online test results of the compression rebound performance of the elastic gasket under test using the rebound response hysteresis angle and the cumulative amount of compression permanent deformation, there are two methods: a method for determining non-compliance and a method for determining deterioration trend.

[0057] In practical implementation, when using the non-compliance determination method, the rebound response hysteresis angle is compared with a preset hysteresis angle threshold. The comparison process is as follows: read the rebound response hysteresis angle value of the current compression rebound cycle, read the preset hysteresis angle threshold value, and calculate the difference between the rebound response hysteresis angle and the preset hysteresis angle threshold. When the rebound response hysteresis angle is greater than the preset hysteresis angle threshold, the compression rebound response hysteresis is determined to be out of tolerance. When the rebound response hysteresis angle is less than or equal to the preset hysteresis angle threshold, the compression rebound response hysteresis is determined to be within tolerance.

[0058] The accumulated compression set is compared with a preset accumulated deformation threshold. The comparison process is as follows: read the accumulated compression set value of the current compression-rebound cycle, read the preset accumulated deformation threshold value, and calculate the difference between the accumulated compression set and the preset accumulated deformation threshold. When the accumulated compression set is greater than the preset accumulated deformation threshold, the compression set is determined to be out of tolerance. When the accumulated compression set is less than or equal to the preset accumulated deformation threshold, the compression set is determined to be within tolerance.

[0059] When either the compression rebound response hysteresis or the compression permanent deformation exceeds the tolerance, the output result indicates that the compression rebound performance is unqualified. An excessive compression rebound response hysteresis indicates that the rebound response hysteresis angle is greater than a preset hysteresis angle threshold; an excessive compression permanent deformation indicates that the cumulative compression permanent deformation exceeds a preset cumulative deformation threshold. When both the compression rebound response hysteresis and compression permanent deformation are within tolerance, the output result indicates that the compression rebound performance is qualified.

[0060] In practical implementation, when using the degradation trend determination method, the historical rebound response hysteresis angle and the historical cumulative compression set are read from the calculation of the previous compression-rebound cycle. The historical rebound response hysteresis angle is the rebound response hysteresis angle calculated using the same steps in the most recent completed compression-rebound cycle. The historical cumulative compression set is the cumulative compression set calculated using the same steps in the most recent completed compression-rebound cycle. When there is no previous compression-rebound cycle, the degradation trend determination method is not executed.

[0061] Subtracting the historical rebound response hysteresis angle from the rebound response hysteresis angle of the current compression and rebound cycle yields the change in hysteresis angle. A positive change in hysteresis angle indicates that the rebound response hysteresis angle of the current compression and rebound cycle is larger than that of the historical cycle. Subtracting the historical cumulative compression set from the cumulative compression set of the current compression and rebound cycle yields the change in cumulative deformation. A positive change in cumulative deformation indicates that the cumulative compression set of the current compression and rebound cycle is larger than that of the historical cycle.

[0062] The system reads the hysteresis angle change rate threshold and the cumulative deformation change rate threshold. The hysteresis angle change rate threshold is a preset threshold used to determine whether the change in the hysteresis angle of the rebound response exceeds the threshold. The cumulative deformation change rate threshold is a preset threshold used to determine whether the change in the cumulative amount of compressive permanent deformation exceeds the threshold. When both the hysteresis angle change and the cumulative deformation change are greater than the cumulative deformation change rate threshold, the system outputs the detection result of the deterioration trend of the compression rebound performance.

[0063] It can be understood that the change in hysteresis angle and the change in cumulative deformation are both increments of the current compression-rebound cycle relative to the previous compression-rebound cycle, used to characterize the trend change in the compression-rebound performance of the elastic gasket as the number of compression-rebound cycles increases.

[0064] In some embodiments, the detection results of unqualified compression rebound performance and the detection results of compression rebound performance degradation trend are displayed by the display unit of the detection system, and an alarm signal is output by the alarm unit of the detection system. The detection results of unqualified compression rebound performance and the detection results of compression rebound performance degradation trend are simultaneously written into the data storage unit of the detection system for online traceability of the compression rebound performance of the elastic gasket.

[0065] In practice, the preset standard included angle value is the included angle between the two tangents of the elastic gasket under test calculated during the first compression and rebound cycle.

[0066] In practice, the pressure-displacement hysteresis loop sequence of the first compression-rebound cycle is obtained, and all rebound sampling points on the unloading rebound branch are extracted from the pressure-displacement hysteresis loop sequence of the first compression-rebound cycle. The cumulative amount of permanent compression deformation of the elastic gasket under test is zero in the first compression-rebound cycle. All rebound sampling points on the unloading rebound branch of the first compression-rebound cycle are directly used as corrected rebound sampling points, and arranged according to the sampling time sequence to obtain the first corrected rebound branch sequence.

[0067] From the initial rebound branch sequence, the first N corrected rebound sampling points of the rebound initiation segment are extracted. N is 5% of the total number of corrected rebound sampling points in the initial corrected rebound branch sequence. The value of N is based on the fact that the first 5% of sampling points in the initial rebound stage of the elastic gasket unloading are located in the rebound initiation linear segment, where the rebound pressure coordinate value and the corrected displacement coordinate value satisfy an approximately linear relationship. From the initial rebound branch sequence, the last M corrected rebound sampling points of the rebound termination segment are extracted. M is 5% of the total number of corrected rebound sampling points in the initial corrected rebound branch sequence. The value of M is based on the fact that the last 5% of sampling points in the rebound termination stage of the elastic gasket unloading are located in the rebound termination linear segment, where the rebound pressure coordinate value and the corrected displacement coordinate value satisfy an approximately linear relationship.

[0068] Linear fitting is performed on the first N corrected rebound sampling points to obtain the slope of the tangent line in the initial rebound segment. The linear fitting uses the least squares method, with the corrected displacement coordinates as the independent variable and the rebound pressure coordinates as the dependent variable, to obtain a linear line. The slope of the fitted line is the slope of the tangent line in the initial rebound segment. Linear fitting is then performed on the next M corrected rebound sampling points to obtain the slope of the tangent line in the final rebound segment. The linear fitting uses the least squares method, with the corrected displacement coordinates as the independent variable and the rebound pressure coordinates as the dependent variable, to obtain a linear line. The slope of the fitted line is the slope of the tangent line in the final rebound segment.

[0069] Based on the slope of the tangent at the beginning of the first rebound and the slope of the tangent at the end of the first rebound, the angle between the two tangents is calculated, and the calculated angle between the two tangents is used as the preset standard angle value.

[0070] In practice, the preset hysteresis angle threshold and the preset cumulative deformation threshold are dynamically adjusted according to the material type and thickness specifications of the elastic gasket to be tested.

[0071] In practice, the testing system pre-stores a material type-thickness specification-threshold mapping table. Each row in this table corresponds to a material type and thickness specification combination, and includes a preset hysteresis angle threshold and a preset cumulative deformation threshold for that combination. Material types include metal spiral wound gaskets, graphite composite gaskets, rubber gaskets, and polytetrafluoroethylene (PTFE) gaskets. The thickness specification is the thickness value of the elastic gasket to be tested. The material type-thickness specification-threshold mapping table is obtained through compression-rebound calibration tests on standard elastic gaskets of the same material type and thickness specification. During the calibration test, the acceptable boundary values ​​for the rebound response hysteresis angle and cumulative compression permanent deformation of the standard elastic gasket at a specified number of compression-rebound cycles are recorded. These acceptable boundary values ​​are used as the preset hysteresis angle threshold and the preset cumulative deformation threshold.

[0072] During testing, the material type and thickness specification of the elastic gasket to be tested are read. The preset hysteresis angle threshold and preset deformation accumulation threshold that match the material type and thickness specification of the elastic gasket to be tested are found in the material type-thickness specification-threshold mapping table. The found preset hysteresis angle threshold and preset deformation accumulation threshold are used to determine the online test results of compression rebound performance.

[0073] It is understandable that when the material type or thickness of the elastic gasket to be tested is different, the corresponding preset hysteresis angle threshold and preset deformation accumulation threshold will change, thereby realizing dynamic adjustment of the threshold.

[0074] See Figure 7 In the figure, the horizontal axis represents the corrected displacement coordinate value, and the vertical axis represents the rebound pressure coordinate value. The green solid curve is the first corrected rebound branch, reflecting the pressure-displacement relationship of the elastic gasket during the unloading and rebound stage of the first compression and rebound cycle. The curve shows an approximately linear upward trend, indicating that the pressure increases with the increase of displacement during the rebound process, reflecting the elastic recovery characteristics of the elastic gasket.

[0075] The orange dashed line is the tangent line of the initial rebound segment. This tangent line is obtained by linear fitting of the first 5% of the sampling points in the initial corrected rebound branch sequence using the least squares method. It represents the linear relationship between rebound pressure and displacement in the initial rebound stage, reflecting the elastic response characteristics of the elastic gasket in the initial rebound stage of unloading.

[0076] The purple dotted line is the tangent line of the first rebound termination segment. This tangent line is obtained by linear fitting of the last 5% of the sampling points in the first corrected rebound branch sequence using the least squares method. It reflects the linear relationship between pressure and displacement in the rebound termination stage and describes the elastic recovery state of the elastic gasket during the unloading and rebound termination stage.

[0077] The angle between the tangent at the beginning of the first rebound and the tangent at the end of the first rebound is the preset standard angle value. The obvious tangent angle in the diagram indicates that the elastic gasket exhibits a certain degree of asymmetry in its rebound response during the first compression and rebound cycle.

[0078] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for online detection of the compression resilience of an elastic gasket, characterized in that, The method includes: The real-time pressure and displacement values ​​of the elastic gasket under test are obtained during multiple consecutive loading, compression, unloading and rebound processes, and a pressure-displacement hysteresis loop sequence is constructed. Based on the pressure-displacement hysteresis loop sequence, the compression initiation displacement at the start point of each loading and the rebound termination displacement at the end point of each unloading are extracted, and the displacement valley value sequence is calculated. Based on the trend of the difference between adjacent displacement valley values ​​in the displacement valley value sequence, the cumulative amount of permanent compression deformation of the elastic gasket under test in the current compression rebound cycle can be identified. The cumulative amount of permanent compression deformation is used to perform coordinate translation correction on the unloading and springback branch in the pressure-displacement hysteresis loop sequence to obtain the corrected springback branch sequence. Extract the tangents of the rebound initiation segment and the rebound termination segment from the modified rebound branch sequence, calculate the change in the angle between the two tangents, and obtain the rebound response hysteresis angle. The online test results of the compression rebound performance of the elastic gasket under test are calculated using the rebound response hysteresis angle and the cumulative amount of compression permanent deformation.

2. The method for online detection of the compression resilience of an elastic gasket according to claim 1, characterized in that, The real-time pressure and displacement values ​​of the elastic gasket under test are obtained during multiple consecutive loading, compression, unloading, and rebound processes, and a pressure-displacement hysteresis loop sequence is constructed, including: Multiple first pressure sampling points and multiple first displacement sampling points during the loading and compression phase, as well as multiple second pressure sampling points and multiple second displacement sampling points during the unloading and rebound phase, are synchronously collected according to a preset sampling frequency. Multiple first pressure sampling points and multiple first displacement sampling points collected in the same loading and compression phase are combined one-to-one according to the sampling time sequence to obtain the loading branch sequence. Multiple second pressure sampling points and multiple second displacement sampling points collected during the same unloading and rebound phase are combined one-to-one according to the sampling time sequence to obtain the rebound branch sequence. By splicing the loading branch sequence and the rebound branch sequence of the same compression and rebound cycle together in a way that connects the beginning and the end, a pressure-displacement hysteresis loop sequence is obtained.

3. The method for online detection of the compression resilience of an elastic gasket according to claim 1, characterized in that, Based on the pressure-displacement hysteresis loop sequence, the compression initiation displacement at the start point of each loading and the rebound termination displacement at the end point of each unloading are extracted, and the displacement valley sequence is calculated, including: Traverse the starting point of the loading branch sequence in the pressure-displacement hysteresis loop sequence, and read the displacement coordinate value corresponding to the starting point as the compression starting displacement of the compression-rebound cycle. Traverse the termination points of the rebound branch sequence in the pressure-displacement hysteresis loop sequence, and read the displacement coordinate value corresponding to the termination point as the rebound termination displacement of the current compression-rebound cycle. The difference between the compression start displacement and the rebound end displacement of the same compression and rebound cycle is calculated to obtain the displacement valley value of that cycle. Arrange the displacement valley values ​​of all cycles in chronological order of compression and rebound to obtain a displacement valley value sequence.

4. The method for online detection of the compression resilience of an elastic gasket according to claim 1, characterized in that, Based on the trend of the difference between adjacent displacement valleys in the displacement valley sequence, the cumulative amount of compression permanent deformation of the elastic gasket under test in the current compression rebound cycle is identified, including: Subtract the previous displacement valley value from the next displacement valley value in the displacement valley value sequence to obtain the valley value difference sequence. Extract the valley difference values ​​that are positive from the valley difference sequence to form a positive difference subsequence; The total cumulative positive difference is obtained by summing the values ​​of all valley differences in the positive difference subsequence. The total cumulative positive difference is taken as the cumulative amount of compression permanent deformation in the current compression rebound cycle.

5. The method for online detection of the compression resilience of an elastic gasket according to claim 1, characterized in that, The cumulative amount of compression permanent deformation is used to perform coordinate translation correction on the unloading springback branch in the pressure-displacement hysteresis loop sequence to obtain a corrected springback branch sequence, including: Extract all rebound sampling points on the unloading rebound branch of the current compression rebound cycle from the pressure-displacement hysteresis loop sequence. Each rebound sampling point contains rebound pressure coordinate values ​​and rebound displacement coordinate values. Subtract the accumulated amount of permanent compression deformation from the rebound displacement coordinate value of each rebound sampling point to obtain the corrected displacement coordinate value; Keeping the rebound pressure coordinate value of each rebound sampling point unchanged, the corrected displacement coordinate value and the rebound pressure coordinate value are recombined to obtain the corrected rebound sampling point. Arrange all corrected rebound sampling points in time sequence to obtain the corrected rebound branch sequence.

6. The method for online detection of the compression resilience of an elastic gasket according to claim 1, characterized in that, Extract the tangents of the rebound initiation segment and the rebound termination segment from the modified rebound branch sequence, calculate the change in the angle between the two tangents, and obtain the rebound response hysteresis angle, including: The first N corrected rebound sampling points of the rebound initiation segment are extracted from the corrected rebound branch sequence, and linear fitting is performed on the first N corrected rebound sampling points to obtain the tangent slope of the rebound initiation segment. The last M corrected rebound sampling points of the rebound termination segment are extracted from the corrected rebound branch sequence, and linear fitting is performed on the last M corrected rebound sampling points to obtain the tangent slope of the rebound termination segment. Calculate the included angle between the two tangents based on the slope of the tangent at the beginning of the rebound and the slope of the tangent at the end of the rebound. Subtract the preset standard angle value from the included angle value to obtain the rebound response hysteresis angle.

7. The method for online detection of the compression resilience of an elastic gasket according to claim 1, characterized in that, Using the rebound response hysteresis angle and the cumulative amount of compression permanent deformation, the online test results of the compression rebound performance of the elastic gasket under test are calculated, including: The rebound response hysteresis angle is compared with a preset hysteresis angle threshold. When the rebound response hysteresis angle is greater than the preset hysteresis angle threshold, it is determined that the compression rebound response hysteresis exceeds the tolerance. The cumulative amount of compressive permanent deformation is compared with a preset cumulative deformation threshold. When the cumulative amount of compressive permanent deformation is greater than the preset cumulative deformation threshold, it is determined that the compressive permanent deformation is out of tolerance. When either the compression rebound response hysteresis error or the compression permanent deformation error is exceeded, the output test result indicates that the compression rebound performance is unqualified.

8. The method for online detection of the compression resilience of an elastic gasket according to claim 1, characterized in that, Using the rebound response hysteresis angle and the cumulative amount of compression permanent deformation, the online test results of the compression rebound performance of the elastic gasket under test are calculated, including: Read the historical rebound response hysteresis angle and historical cumulative compression permanent deformation obtained from the previous compression rebound cycle; Subtract the historical rebound response hysteresis angle from the rebound response hysteresis angle of the current compression rebound cycle to obtain the hysteresis angle change rate; Subtract the historical cumulative compression set from the cumulative compression set during the current compression and rebound cycle to obtain the rate of change of cumulative deformation. When both the hysteresis angle change rate and the cumulative deformation change rate are greater than their respective preset change rate thresholds, the detection result of the compression rebound performance degradation trend is output.

9. The method for online detection of the compression resilience of an elastic gasket according to claim 6, characterized in that, The preset standard included angle value is the included angle between two tangents calculated during the first compression and rebound cycle of the elastic gasket under test.

10. The method for online detection of the compression resilience of an elastic gasket according to claim 7, characterized in that, The preset hysteresis angle threshold and the preset cumulative deformation threshold are dynamically adjusted according to the material type and thickness specification of the elastic gasket to be tested.

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