Multidimensional Judgment Method Applied to Brake Shoe Shear Resistance Testing Equipment
By using a multi-dimensional assessment method that combines maximum shear strength, shear toughness, and stability index, the problem of inaccurate single-strength assessment in existing technologies is solved, enabling refined evaluation and risk warning of brake shoe bonding quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG SAFE TECH CO LTD
- Filing Date
- 2025-12-04
- Publication Date
- 2026-06-30
Smart Images
Figure CN121678407B_ABST
Abstract
Description
Technical Field
[0001] This invention specifically relates to a multidimensional determination method for brake shoe shear resistance testing equipment. Background Technology
[0002] Current brake shoe shear resistance tests generally use maximum shear strength as the criterion. Although test standards specify loading rate and ambient temperature, they do not consider energy dissipation and load stability during the shear process. Even when local slippage or microcracks appear at the bond interface, the maximum shear strength can still remain high. Existing technologies have attempted to add a high-temperature holding test, but this still relies on single-point strength and cannot quantify toughness and process stability, leaving the judgment blind spot unresolved. Therefore, a multi-dimensional comprehensive judgment method is urgently needed to achieve a refined evaluation of brake shoe bond quality. Summary of the Invention
[0003] This invention provides a multi-dimensional judgment method for brake shoe shear resistance testing equipment to solve the technical problem of inaccuracy of traditional early warning methods mentioned above. The specific technical solution is as follows:
[0004] A multidimensional determination method for brake shoe shear resistance testing equipment includes the following steps:
[0005] S1: Under constant temperature and humidity test conditions, a shear load parallel to the bonding surface is applied to the brake shoe assembly. The continuous curve F(s) of shear force F versus displacement s is collected simultaneously, and the displacement s at the failure point is recorded. fail ;
[0006] S2: Calculate the maximum shear strength D1:
[0007] D1 = F max / A
[0008] Where A is the bonding area, F max Maximum shear force;
[0009] S3: Calculate the shear toughness index D2:
[0010]
[0011] S4: Calculate the shear stability index D3:
[0012]
[0013] s lin =a*s fail F fit (s) is the least squares linear fitting line of F(s) in this interval;
[0014] S5: Calculate the comprehensive shear resistance index S:
[0015]
[0016] w1 represents the normalized value for each dimension; w2 and w3 are the corresponding weights, and w1 + w2 + w3 = 1.
[0017] S6: Result determination is based on the comprehensive shear resistance index S. When S≥S min It is considered qualified if it is in time, otherwise it is unqualified.
[0018] Furthermore, in step S2, F max Take the first peak value of the F(s) curve. If multiple peak values appear, take the global maximum value to ensure that D1 reflects the most dangerous shear strength.
[0019] Furthermore, the integration in step S3 adopts the trapezoidal method or Simpson's method, with a step size of no more than 0.01 mm, to ensure that the D2 error is less than 1%.
[0020] Furthermore, s lin It can be done in 0.7s fail ~0.9s fail The dynamic adjustment is made between them to eliminate the interference of macroscopic slippage on D3.
[0021] Furthermore, in step S5, the normalization uses the 95th percentile of historical batch samples as the upper limit and the 5th percentile as the lower limit to achieve comparability of S between different batches.
[0022] Furthermore, the weights w1, w2, and w3 are automatically assigned values using the analytic hierarchy process or the entropy weight method, and users are allowed to manually fine-tune them according to the vehicle's safety level.
[0023] Furthermore, the weights w1, w2, and w3 are set according to the actual quality requirements:
[0024] High-security scenario: w1=0.5, w2=0.3, w3=0.2;
[0025] High durability scenario: w1=0.4, w2=0.4, w3=0.2.
[0026] Furthermore, the threshold S in step S6 min Determined by the receiver operating characteristic curve (ROC).
[0027] Furthermore, when S fails to meet the target, the system outputs... , , The ranking of shortcomings guides the prioritization of adjusting the curing temperature or roughness of the adhesive.
[0028] Furthermore, the curve F(s) can be tested at three temperatures: room temperature, 150°C, and 250°C, and the comprehensive shear resistance index S can be calculated accordingly. RT S HT S EHT The minimum value is then taken as the final comprehensive shear resistance index S to cover the risk of thermal degradation.
[0029] The multidimensional judgment method for brake shoe shear resistance testing equipment provided by this invention combines toughness and process stability, and constructs a three-dimensional judgment model based on the traditional strength dimension, so as to realize the scientific quantification and risk warning of shear resistance test results. Attached Figure Description
[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0031] Figure 1 This is a schematic diagram of a multidimensional judgment method applied to a brake shoe shear resistance testing device according to this application. Detailed Implementation
[0032] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.
[0033] like Figure 1 The figure shows a multidimensional determination method for brake shoe shear resistance testing equipment according to this application, including the following steps:
[0034] S1: Under constant temperature and humidity test conditions, a shear load parallel to the bonding surface is applied to the brake shoe assembly. The continuous curve F(s) of shear force F versus displacement s is collected simultaneously, and the displacement s at the failure point is recorded. fail .
[0035] Specifically, the brake shoe specimen was placed in a constant temperature and humidity chamber, maintaining a temperature of (23±2)℃ and a relative humidity of (50±5)% to eliminate the coupling interference of temperature and humidity fluctuations on the mechanical properties of the adhesive layer. A constant beam displacement rate of 1 mm / min was used to apply shear force parallel to the bonding surface; the force sensor had a range of 0-50 kN and an accuracy of 0.5 grade; the displacement sensor had a resolution of 0.001 mm and a sampling frequency of not less than 1 kHz. The F(s) curve was continuously recorded until the load dropped to 80% of its peak value or the displacement exceeded 5 mm. The displacement at this point was defined as s. fail .
[0036] S2: Calculate the maximum shear strength D1
[0037] D1 = F max / A
[0038] Where A is the measured bonding area, F max This represents the maximum shear force.
[0039] In step S2, F max The first peak value of the F(s) curve is taken; if multiple peak values appear, the global maximum value is taken to ensure that D1 reflects the most critical shear strength. It is understandable that during shear testing, interface defects or local debonding can cause "false peaks" or "stepped peaks" in the load curve. If the first local peak value is directly taken as F... max This can easily lead to an underestimation of the true load-bearing limit, resulting in errors in the safety margin calculation. This limitation first scans all sampling points of F(s), identifies all extreme points, compares their amplitudes, and finally locks the global maximum value, ensuring that D1 always corresponds to the highest load before complete interface failure. Since the brake shoe experiences a one-time, impact-type shear force at the moment of actual braking, the global maximum value is a direct measure of the most dangerous working condition, preserving the original safety boundary to the greatest extent. Furthermore, this strategy is robust to process fluctuations such as uneven adhesive layer thickness and micropore aggregation, providing a unified strength benchmark for subsequent dimensions D2 and D3 without increasing experimental costs, thereby improving the comparability and traceability of the comprehensive index S.
[0040] S3: Calculate the shear toughness index D2
[0041] ;
[0042] The shear toughness index D2 defines the energy absorbed per unit area during shearing, reflecting the interface's ability to resist crack propagation before failure. Even if D1 meets the standard, a low D2 indicates high interface brittleness, making it prone to sudden spalling and posing a safety hazard.
[0043] The integration in step S3 uses the trapezoidal or Simpson method with a step size no greater than 0.01 mm to ensure that the D2 error is less than 1%. The essence of the toughness dimension D2 is the energy absorbed per unit area before fracture, and its value directly depends on the integration accuracy. If the step size is too large, subtle fluctuations in the curve will be missed, leading to an underestimation of energy and misjudging good toughness as poor toughness. This limitation compresses the displacement step size to within 0.01 mm, which can obtain no less than 1000 data points in a total displacement of 10 mm, fully satisfying the Nyquist sampling theorem and controlling the truncation error of the trapezoidal or Simpson method to below 0.3%; combined with the sensor accuracy, the total error does not exceed 1%. High-fidelity D2 can not only distinguish between two typical bonding states: high-strength hard and brittle and low-strength high-toughness, but also provide quantitative feedback during heat treatment process optimization: when the curing temperature rises and the adhesive layer becomes brittle, D2 will decrease first, while D1 may remain high, thus providing early warning of the risk of thermal degradation and avoiding latent failures that cannot be detected by the strength dimension alone.
[0044] S4: Calculate the shear stability index D3
[0045] ;
[0046] s lin =a*s fail , a∈[0.7,0.9], F fit (s) represents the least-squares linear fit of F(s) within this interval. In this application, a = 0.8. The closer D3 is to 1, the more uniform the stress at the bonding interface, with no local slippage or gradual debonding. A low D3 value indicates micro-slippage or uneven bonding at the interface, suggesting poor long-term reliability.
[0047] The shear stability index D3 represents the linearity deviation during the shear force rise phase and is used to quantify the smoothness of the shear process.
[0048] As another alternative implementation, s lin It can be done in 0.7s fail ~0.9s fail The values are dynamically adjusted to eliminate the interference of macroscopic slip on D3. It is understandable that the stability index D3 depends on the deviation between the ideal linear elastic segment and the measured curve. If the upper limit is fixed at 0.8s... fail When interfacial slip or microcrack polymerization occurs prematurely in the adhesive layer, nonlinear components are forcibly included in the linear fitting window, causing D3 to be artificially inflated and losing its ability to identify implicit slip. This limitation introduces a dynamic window: the algorithm first calculates 0.7, 0.75, 0.8, 0.85, and 0.9s. failThe goodness-of-fit R² of each of the five segments was used, and the window with the largest R² and a residual mutation rate of <5% was selected as the final linear segment. This automatically eliminates segments where macroscopic slip has occurred, retaining only the true elastic deformation range, making D3 sensitive only to microscopic adhesion unevenness and not contaminated by macroscopic slip. Using a dynamic window improves D3's resolution to curing pressure deviations and significantly enhances the model's robustness under different process fluctuations.
[0049] S5: Calculate the comprehensive shear resistance index S
[0050] ;
[0051] These are the normalized values for each dimension. w1, w2, and w3 are the corresponding weights, and w1 + w2 + w3 = 1.
[0052] Preferably, in step S5, the normalization uses the 95th percentile of historical batch samples as the upper limit and the 5th percentile as the lower limit to achieve comparability of S between different batches. It is understandable that if a fixed theoretical limit is used for normalization, when raw material batch changes or environmental humidity variations cause overall performance drift, S will exhibit a systematic shift, making longitudinal quality tracking difficult. This limitation uses the 95th percentile of at least 30 historical samples over a rolling 12-month period as the upper limit and the 5th percentile as the lower limit to construct a dynamic mapping interval, ensuring that the current sample is always compared with the most recent actual process limit. This strategy eliminates seasonal fluctuations while retaining the early warning function for abnormal samples: when a sudden defect causes D1 to fall below the historical 5th percentile, the normalized value will be directly reset to zero, triggering an immediate alarm; simultaneously, the upper limit automatically shifts upward as the process improves, avoiding the ceiling effect that compresses the improvement space, thereby ensuring that S remains monotonically comparable during long-term quality improvement.
[0053] As a preferred implementation, weights w1, w2, and w3 are automatically assigned values using the analytic hierarchy process (AHP) or entropy weighting, and users are allowed to manually fine-tune them according to the vehicle's safety level. It is understandable that different vehicle models have varying requirements for "strength-toughness-stability." Racing cars prioritize high-temperature strength, city buses value toughness and fatigue resistance, while off-road vehicles require stability to withstand impacts. This approach first uses entropy weighting to objectively weight samples from the past three months, capturing the information inherent in the data; then, it introduces the AHP to transform the OEM's qualitative judgment of "failure consequences severity" into a pairwise comparison matrix, obtaining subjective weights; finally, it takes a linear weighted average of the two weights and allows for a ±20% manual fine-tuning range. This hybrid strategy avoids the arbitrariness of purely subjective judgment while retaining sufficient engineering freedom, enabling S to accurately map design goals for different safety levels and achieving flexible manufacturing with standardized production lines and tiered standards.
[0054] As an optional implementation, the weights w1, w2, and w3 are set according to the actual quality requirements. Different application scenarios have different requirements for different dimensions. In high-security scenarios: w1=0.5, w2=0.3, w3=0.2; in high-durability scenarios: w1=0.4, w2=0.4, w3=0.2.
[0055] S6: Result determination based on the comprehensive shear resistance index S
[0056] When S≥S min If it is qualified, it is considered qualified; otherwise, it is unqualified. Optional, S min It is 0.75.
[0057] It is understandable that, preferably, the maximum shear strength D1 needs to be greater than a certain threshold. Based on this, the S-value is then determined.
[0058] The threshold S in step S6 min The receiver operating characteristic curve (ROC) is used to determine the false positive rate to be ≤2%.
[0059] Understandably, traditional fixed percentage thresholds cannot balance the contradiction between over-detection and under-detection. This study limited the collection of 500 historical samples, using bench fatigue verification results as the ground truth, plotted an ROC curve, and selected the S-value corresponding to the point of maximum Youden index as the S-value. min This method can reduce the sum of Type I false positives (criteria judged as unqualified) and Type II false positives (criteria judged as qualified) to less than 2%. This statistical method frees threshold setting from empiricism and directly links it to vehicle-level safety indicators. When significant changes occur in the material system or process route, samples can be re-collected and the ROC updated to ensure that the judgment boundary always matches the actual failure risk.
[0060] When S fails to meet the target, the system outputs... , , The ranking of weaknesses guides the priority adjustment of adhesive curing temperature or surface roughness. Specifically, the multidimensional model, while indicating pass / fail status, can calculate the marginal contribution rate of each dimension to S, pinpointing the weakest link. The lowest setting indicates insufficient toughness; therefore, the curing temperature should be lowered or a toughening agent should be added. The lowest value indicates interface slippage, requiring increased roughness of the metal shoe or an additional primer coating. If... If the minimum is reached, then increasing the strength of the adhesive itself should be considered. This quantitative ranking avoids the time and material waste caused by trial and error, allowing process engineers to complete targeted optimization within a single batch, shortening the DOE cycle, and the improvement effect can be directly reflected in the increase of S, forming a closed-loop control of "test-diagnosis-improvement-verification".
[0061] The F(s) curve can be tested at room temperature, 150℃, and 250℃ respectively, and the comprehensive shear resistance index S can be calculated accordingly. RT S HT S EHT The minimum value is then taken as the final comprehensive shear resistance index S to cover the risk of thermal degradation. Specifically, during continuous braking in mountainous areas or high-speed emergency braking, the interface temperature of the brake shoe can instantly rise above 250°C, leading to a decrease in the rubber layer modulus and a deterioration in toughness. This specification adds two hot-state conditions, 150°C and 250°C, to the standard room temperature test, and calculates the S value S for each condition. RT S HT S EHT Finally, we take S = min(S RT S HT S EHT This serves as the basis for determining product quality. This strategy ensures that the worst-case temperature condition, rather than the ideal room temperature condition, determines product quality, effectively preventing batches with insufficient high-temperature toughness or severe thermo-oxidative aging.
[0062] In the embodiments of this application, all calculation steps are embedded in the testing machine's host computer software, and the judgment results are interfaced with the MES system to achieve online monitoring and quality traceability of the brake shoe's shear resistance performance. Specifically, by encapsulating the multidimensional algorithm as a DLL plugin, the shear testing machine can automatically output the S-value and dimensional decomposition report within 0.5 seconds after the test ends, and upload it to the factory's MES system via the OPC-UA protocol. This is then linked to key process parameters such as the production batch number, adhesive batch number, and curing oven temperature curve to form a complete electronic quality record. Once a failed part appears in the market, the S-value and dimensional decomposition report at that time can be retrieved by using the batch number. , , By analyzing process parameters, the system can quickly pinpoint the root cause. Simultaneously, it can be configured with trend warnings for S (surface value), automatically freezing production when the S value drops by more than 5% for three consecutive batches, achieving zero-delay quality interception. This digital closed loop not only meets OEMs' requirements for a traceable and predictable intelligent supply chain but also lays a data foundation for subsequent big data mining and machine learning prediction, significantly improving the intelligence level of the brake shoe manufacturing process.
[0063] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.
Claims
1. A multidimensional determination method for brake shoe shear resistance testing equipment, characterized in that, Includes the following steps: S1: Under constant temperature and humidity test conditions, a shear load parallel to the bonding surface is applied to the brake shoe assembly. The continuous curve F(s) of shear force F versus displacement s is collected simultaneously, and the displacement s at the failure point is recorded. fail ; S2: Calculate the maximum shear strength D1: D1=F max / A Where A is the bonding area, F max Maximum shear force; S3: Calculate the shear toughness index D2: S4: Calculate the shear stability index D3: s lin =a*s fail F fit (s) is the least squares linear fitting line of F(s) in this interval; S5: Calculate the comprehensive shear resistance index S: w1 represents the normalized value for each dimension; w2 and w3 are the corresponding weights, and w1 + w2 + w3 = 1. S6: Determine the result based on the comprehensive anti-shear performance index S. If S ≥ S min , it is judged as qualified; otherwise, it is unqualified. s lin It can be done in 0.7s fail ~0.9s fail The dynamic adjustment between them is used to eliminate the interference of macroscopic slippage on D3; In step S5, normalization uses the 95th percentile of historical batch samples as the upper limit and the 5th percentile as the lower limit to achieve comparability of S between different batches. Weights w1, w2, and w3 are set according to actual quality requirements: High-security scenario: w1=0.5, w2=0.3, w3=0.2; High durability scenario: w1=0.4, w2=0.4, w3=0.2; The curve F(s) can be tested at room temperature, 150℃, and 250℃ respectively, and the comprehensive shear resistance index S can be calculated accordingly. RT S HT S EHT The minimum value is then taken as the final comprehensive shear resistance index S to cover the risk of thermal degradation.
2. The multidimensional determination method for brake shoe shear resistance testing equipment according to claim 1, characterized in that, In step S2, F max Take the first peak value of the F(s) curve. If multiple peak values appear, take the global maximum value to ensure that D1 reflects the most dangerous shear strength.
3. The multidimensional determination method for brake shoe shear resistance testing equipment according to claim 1, characterized in that, The integration in step S3 uses the trapezoidal method or Simpson's method, with a step size of no more than 0.01 mm, to ensure that the D2 error is less than 1%.
4. The multidimensional determination method for brake shoe shear resistance testing equipment according to claim 1, characterized in that, The weights w1, w2, and w3 are automatically assigned using the analytic hierarchy process or the entropy weight method, and users are allowed to manually fine-tune them according to the vehicle's safety level.
5. The multidimensional determination method for brake shoe shear resistance testing equipment according to claim 1, characterized in that, The threshold S in step S6 min Determined by the receiver operating characteristic curve (ROC).
6. The multidimensional determination method for brake shoe shear resistance testing equipment according to claim 1, characterized in that... , When S fails to meet the target, the system outputs... , , The ranking of shortcomings guides the prioritization of adjusting the curing temperature or roughness of the adhesive.