Clutch thermal load evaluation method and system considering spline friction pair

Abstract

The invention discloses a clutch thermal load evaluation method and system considering a spline friction pair. The evaluation method comprises the steps that the axial contact pressure attenuation coefficient of a friction element is obtained; calculating the average surface pressure of each friction pair of the clutch based on the axial contact pressure attenuation coefficient; based on the average surface pressure, friction torques and temperature fields of all friction pairs of the clutch are obtained; calculating the single spline tooth torque and the in-plane bending moment of each friction pair based on the friction torque and the temperature field of each friction pair; calculating a critical value of heat engine coupling failure based on the size characteristics of the dual steel disc; and evaluating the thermal load of the clutch based on the single spline tooth torque and the in-plane bending moment of each friction pair and the critical value of the heat engine coupling failure. According to the method, the real-time torques and temperatures of the friction elements at different positions can be solved, the friction torques and radial temperature fields of the dual steel discs at different moments and different positions are obtained, and failure evaluation is carried out.

Description

Technical Field

[0001] The invention belongs to the field of automobile clutches, and in particular relates to a clutch thermal load evaluation method and system taking spline friction pairs into consideration. Background Art

[0002] The wet shift clutch is widely used in vehicle transmission devices due to its unique advantages such as strong load-bearing capacity, large torque transmission and simple structure. It is the core component of various step-speed transmission devices. The clutch's matching friction pair is composed of multiple ring-shaped dual steel plates and friction plates arranged alternately. The dual steel plates are connected to the clutch cylinder sleeve keyway through external splines, and the friction plates are connected to the transmission gears through internal splines. During the clutch engagement process, the power input shaft transmits the input torque to the dual steel plates through the cylinder sleeve through the spline connection pair, and the friction plates transmit the friction torque to the transmission gear through the spline connection pair to complete the power output. During the axial movement process of the friction element and the static compression process, the spline teeth are subjected to shear force. The generation of axial friction directly affects the contact pressure transmission between the friction pairs, and has a certain impact on the temperature field calculation and failure analysis of the friction element.

[0003] Prior art 1 proposes a method for dynamic modeling and parameter determination of a wet friction clutch considering a spline pair, and realizes the study of the dynamic characteristics of the spline connection between the inner and outer hubs of the clutch and the friction plate and the dual steel plate. Prior art 2 proposes a wear detection method for the spline teeth of a friction disk in a disc brake, which can effectively detect the wear of the spline teeth of the friction disk. At present, no relevant research has considered the influence of the force characteristics of the spline teeth on the torque transmission and temperature field of the friction pair, resulting in errors in the clutch thermodynamic simulation results, which is not conducive to the precise control of the vehicle transmission system. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a clutch thermal load assessment method and system taking into account the spline friction pair, which can accurately obtain the contact pressure and surface temperature of all friction elements of the clutch, assess the failure trend of the friction elements, and help the driver to use it as a reference.

[0005] To achieve the above object, the present invention provides a clutch thermal load evaluation method considering a spline friction pair, comprising:

[0006] Obtaining the axial contact pressure attenuation coefficient of the friction element;

[0007] Calculating the average surface pressure of each friction pair of the clutch based on the axial contact pressure attenuation coefficient;

[0008] Based on the average surface pressure, obtaining the friction torque and temperature field of each friction pair of the clutch;

[0009] Calculating the single spline tooth torque and in-plane bending moment of each friction pair based on the friction torque and temperature field of each friction pair;

[0010] Based on the dimensional characteristics of the dual steel sheets, the critical value of thermal-mechanical coupling failure is calculated;

[0011] The clutch thermal load is evaluated based on the single spline tooth torque of each friction pair, the in-plane bending moment and the critical value of the thermal-mechanical coupling failure.

[0012] Optionally, the friction element includes: a friction plate and a steel plate.

[0013] Optionally, obtaining the axial contact pressure attenuation coefficient of the friction element includes: obtaining the axial contact pressure attenuation coefficient of the friction plate and the axial contact pressure attenuation coefficient of the steel plate respectively;

[0014] The method for obtaining the axial contact pressure attenuation coefficient of the friction plate is:

[0015]

[0016] Among them, ξ f is the axial contact pressure attenuation coefficient of the friction plate, μ is the friction coefficient of the surface friction pair, μ f is the key friction coefficient of the friction plate spline friction pair, R f is the pitch radius of the friction plate spline friction pair, α f is the pressure angle of the friction plate spline friction pair, R i is the inner ring radius of the friction element, R o is the outer ring radius of the friction element;

[0017] The method for obtaining the axial contact pressure attenuation coefficient of the steel sheet is:

[0018]

[0019] Among them, ξ s is the axial contact pressure attenuation coefficient of the steel sheet, μ is the friction coefficient of the surface friction pair, μ s is the key friction coefficient of the steel spline friction pair, R s is the pitch radius of the steel spline friction pair, α s is the pressure angle of the steel spline friction pair.

[0020] Optionally, the method for calculating the average surface pressure of each friction pair of the clutch is:

[0021]

[0022] Among them, p i+1 is the contact pressure of the i+1th friction pair, ξ is the axial contact pressure attenuation coefficient, p is the clutch piston pressure, pi is the contact pressure of the i-th friction pair, i=1,2,3...M-2 is the friction plate number.

[0023] Optionally, the method for obtaining the friction torque of each friction pair of the clutch is:

[0024]

[0025] Where, M is the total friction torque, M i is the friction torque of the th friction plate.

[0026] Optionally, obtaining the temperature field of each friction pair includes:

[0027] Based on the average surface pressure, calculating the heat flux density of each friction pair;

[0028] Based on the heat flux density, the temperature field of each friction pair is obtained.

[0029] Optionally, the method for calculating the heat flux density of each friction pair is:

[0030] q i (r,t)=μ·p i ω(t) r

[0031] Among them, q i (r, t) is the heat flux density of each friction pair, ω(t) is the rotational angular velocity of the friction element, r represents the radial coordinate, and μ is the friction coefficient.

[0032] Optionally, critical values ​​for calculating thermal-mechanical coupling include:

[0033] The critical bending moment of the steel sheet causing thermal warping and the critical torque of the single spline teeth of the steel sheet are calculated respectively;

[0034] Based on the critical bending moment of the steel sheet causing thermal warping and the critical torque of the single spline teeth of the steel sheet, a critical value of thermal-mechanical coupling failure is obtained.

[0035] The present invention also provides a clutch thermal load evaluation system considering spline friction pairs, characterized in that it comprises: a contact pressure calculation module, a friction torque calculation module, a temperature field calculation module, a failure critical value calculation module, and a failure evaluation module;

[0036] The contact pressure calculation module is used to obtain the average contact pressure of each friction pair;

[0037] The temperature field calculation module is used to obtain the temperature field of each friction pair based on the average contact pressure of the friction pair;

[0038] The failure critical value calculation module is used to calculate the failure critical value of the friction element;

[0039] The failure assessment module is used to assess the friction element according to the failure threshold value.

[0040] Compared with the prior art, the present invention has the following advantages and technical effects:

[0041] The present invention provides a clutch thermal load assessment method and system considering the spline friction pair, considering the friction force of the spline teeth of the clutch friction plate and steel plate, and giving the pressure attenuation coefficient of the piston pressure attenuation along the axial direction, so that the friction torque and temperature characteristics generated by each friction pair can be calculated more accurately; at the same time, according to the torque borne by the single spline teeth of the steel plate and the in-plane bending moment borne by the steel plate, the working state of the clutch can be more accurately judged, and whether the clutch has a risk of thermal engine failure can be assessed, which has a positive effect on reducing clutch failure and is suitable for large-scale promotion and application. In addition, this method and system can realize the solution of the real-time torque and temperature of friction elements at different positions, and obtain the friction torque and radial temperature field of the dual steel plates at different times and positions, which solves the disadvantage that the traditional method can only solve the average temperature rise of the clutch and the friction torque of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0043] Figure 1 is a flow chart of a clutch thermal load evaluation method considering a spline friction pair according to an embodiment of the present invention;

[0044] Figure 2 It is a layout scheme and friction element numbering diagram of an embodiment of the present invention;

[0045] Figure 3 This is a temperature rise characteristic diagram of a steel sheet 2 according to an embodiment of the present invention;

[0046] Figure 4 This is a radial temperature rise diagram of the steel sheet 2 at the end of sliding according to an embodiment of the present invention. DETAILED DESCRIPTION

[0047] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0048] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0049] The present invention proposes a clutch thermal load evaluation method and system considering the spline friction pair, such as Figure 1 As shown, the specific steps include:

[0050] Obtaining the axial contact pressure attenuation coefficient of the friction element;

[0051] Based on the axial contact pressure attenuation coefficient, the average surface pressure of each friction pair of the clutch is calculated;

[0052] Based on the average surface pressure, the friction torque and temperature field of each friction pair of the clutch are obtained;

[0053] Based on the friction torque and temperature field of each friction pair, the single spline tooth torque and in-plane bending moment of each friction pair are calculated;

[0054] Based on the dimensional characteristics of the dual steel sheets, the critical value of thermal-mechanical coupling failure is calculated;

[0055] The clutch thermal load is evaluated based on the single spline tooth torque, in-plane bending moment and critical value of thermal-mechanical coupling failure of each friction pair.

[0056] Furthermore, the friction element includes: a friction plate and a steel plate.

[0057] Specifically, Figure 2 As shown, install the clutch, arrange the outer tooth steel plate and the inner tooth friction plate alternately, and name the friction elements from the piston end to the pressure plate end. The pairs of steel plates numbered 0, 2, 4…, i, …M-1 are paired steel plates, and the pairs of steel plates and friction plates numbered 1, 3, 5…, i+1, …M-2 are friction plates. The paired friction pairs of steel plates and friction plates are marked as: S0, S1, S2…S i …S M-1 The piston pressure of the clutch is p, and the inner and outer ring radii of the friction element are R i , R o ;

[0058] Further, obtaining the axial contact pressure attenuation coefficient of the friction element includes: obtaining the axial contact pressure attenuation coefficient of the friction plate and the axial contact pressure attenuation coefficient of the steel plate respectively;

[0059] The method for obtaining the axial contact pressure attenuation coefficient of the friction plate is:

[0060]

[0061] Among them, ξ f is the axial contact pressure attenuation coefficient of the friction plate, μ is the friction coefficient of the surface friction pair, μ f is the key friction coefficient of the friction plate spline friction pair, R f is the pitch radius of the friction plate spline friction pair, α fis the pressure angle of the friction plate spline friction pair, R i is the inner ring radius of the friction element, R o is the outer ring radius of the friction element;

[0062] The method for obtaining the axial contact pressure attenuation coefficient of the steel sheet is:

[0063]

[0064] Among them, ξ s is the axial contact pressure attenuation coefficient of the steel sheet, μ is the friction coefficient of the surface friction pair, μ s is the key friction coefficient of the steel spline friction pair, R s is the pitch radius of the steel spline friction pair, α s is the pressure angle of the steel spline friction pair.

[0065] Furthermore, the method for calculating the average surface pressure of each friction pair of the clutch is:

[0066]

[0067] Among them, p i+1 is the contact pressure of the i+1th friction pair, ξ is the axial contact pressure attenuation coefficient, p is the clutch piston pressure, p i is the contact pressure of the i-th friction pair.

[0068] Specifically, the contact pressure of friction pairs S0, S1, S2, etc. can be solved as:

[0069] Furthermore, the method for obtaining the total friction torque of the clutch is:

[0070]

[0071] Where, M is the total friction torque of the clutch, M i is the friction torque of the i-th clutch.

[0072] Specifically, considering the contact pressure attenuation, steel plate 0 has only one friction surface that generates friction torque, so the friction torque generated by steel plate 2 in the clutch is the largest, and the calculation formula is:

[0073]

[0074] Then the friction torque transmitted by the single spline teeth of steel sheet 2 is:

[0075]

[0076] Where n is the number of teeth on the dual steel plates.

[0077] Furthermore, obtaining the temperature field of each friction pair includes:

[0078] Based on the average surface pressure, calculate the heat flux density of each friction pair;

[0079] Based on the heat flux density, the temperature field of each friction pair is obtained.

[0080] Specifically, calculate the heat flux density of each friction pair:

[0081] q i (r,t)=μ·p i ·ω(t)·r,

[0082] Where ω(t) is the rotational angular velocity of the friction element, r represents the radial coordinate, and μ is the friction coefficient.

[0083] Subsequently, according to the difference in contact pressure of each friction pair, the heat flux density flowing into different friction pairs can be obtained. For example, the heat flux densities generated by the two friction pairs of steel sheet 2 are q2(r, t) and q3(r, t) respectively.

[0084] According to the two-dimensional heat conduction formula of the disk, the surface temperature of the friction elements at different positions is calculated by considering the difference of heat flux density of each friction pair.

[0085] Since the heat flux density of steel sheet 2 is the largest, it is only necessary to determine whether steel sheet 2 has a risk of thermal failure: extract the radial temperature value of steel sheet 2 at the end of sliding friction, and transform it into a function T2(r) through Fourier transformation. According to thermal stress theory, substitute the radial temperature function into the circumferential stress formula of the disk, as shown below:

[0086]

[0087] Where σ2(r) is the circumferential thermal stress, α is the thermal expansion coefficient, E is the elastic modulus, and r is i 、r o are the inner and outer diameters of the friction element.

[0088] Then, the in-plane bending moment of steel sheet 2 is calculated:

[0089]

[0090] Where h is the thickness of the friction element.

[0091] Furthermore, the critical value of the thermal-mechanical coupling is calculated by:

[0092] The critical bending moment of the steel sheet causing thermal warping and the critical torque of the single spline teeth of the steel sheet are calculated respectively;

[0093] The critical value of thermal-mechanical coupling is obtained based on the critical bending moment of thermal warping of the steel sheet and the critical torque of the single spline tooth of the steel sheet.

[0094] Specifically, thermal failure: The critical bending moment of thermal warping of steel sheets is:

[0095]

[0096] Where n is the warping mode, n = 0, 1, 2...; B1 is the bending stiffness, C1 is the torsional stiffness, r m is the median diameter of the steel sheet; w is the width of the steel sheet; G is the shear elastic modulus of the dual steel sheet.

[0097] ② Mechanical failure: Calculate the critical torque of the single spline tooth of steel sheet 2:

[0098]

[0099] Where a is the distance of the load point vertically above the center of mass, and ξ is the torque coefficient.

[0100] Specifically, the judgment of thermal-mechanical coupling failure: Since the friction torque and temperature field of steel sheet 2 are the largest, it is only necessary to judge whether steel sheet 2 has thermal-mechanical coupling failure. The evaluation method is:

[0101] |M s |<M T ∩M 22 <M 2M In a safe area

[0102] |M s |≥M T ∩M 22 <M 2M Thermal failure has occurred

[0103] |M s |<M T ∩M 22 ≥M 2M Mechanical failure has occurred

[0104] |M s |≥M T ∩M 22 ≥M 2M Thermal-mechanical coupling failure has occurred

[0105] According to the failure mode, the system gives corresponding maintenance prompts. If a mechanical failure occurs, the piston pressure is reduced; if a thermal failure occurs, the lubrication flow is increased; if a thermal-mechanical coupling failure occurs, the system must both reduce the piston oil pressure and increase the lubrication flow.

[0106] The present invention also provides a clutch thermal load evaluation system considering spline friction pairs, comprising: a contact pressure calculation module, a friction torque calculation module, a temperature field calculation module, a failure critical value calculation module, and a failure evaluation module;

[0107] A contact pressure calculation module is used to obtain the average contact pressure of each friction pair;

[0108] A temperature field calculation module is used to obtain the temperature field of each friction pair based on the average contact pressure;

[0109] A failure critical value calculation module, used to calculate the failure critical value of the friction element;

[0110] The failure assessment module is used to assess the friction element according to the failure threshold value.

[0111] In the contact pressure calculation module, after inputting the clutch friction element layout and actual structural characteristic parameters, this module can be used to solve the pressure attenuation coefficient ξ between the steel plate and the friction plate in the process of transmitting axial contact pressure. s , f , and then calculate the average contact pressure of each friction pair.

[0112] In the friction torque calculation module, the total friction torque transmitted by the clutch is obtained according to the average contact pressure of each friction pair; in addition, according to the number of spline teeth of the dual steel plates, the friction torque transmitted by the single spline teeth of the steel plate 2 which is most prone to mechanical failure is obtained.

[0113] In the temperature field calculation module, the heat flux density q of the friction pair is calculated according to the average contact pressure of each friction pair. i (r, t), and then calculate the temperature field of each friction pair of the clutch. Then, extract the radial temperature value of the steel sheet 2 at the end of sliding friction, and calculate the in-plane bending moment of the steel sheet 2.

[0114] Since the heat flux density of steel sheet 2 is the largest, it is only necessary to determine whether steel sheet 2 has a risk of thermal failure: transform it into a function T2(r) through Fourier transform. According to thermal stress theory, the radial temperature function is substituted into the circumferential stress formula of the disk, as shown below:

[0115] In the failure critical value calculation module, the critical in-plane bending moment and the single spline tooth critical torque of the steel sheet 2 that cause thermal failure and mechanical failure are calculated respectively.

[0116] In the failure assessment module, the data of the above modules are called to assess whether the steel sheet 2 has failed. If a mechanical failure occurs, the piston pressure is reduced; if a thermal failure occurs, the lubrication flow is increased; if a thermal-mechanical coupling failure occurs, the system should both reduce the piston oil pressure and increase the lubrication flow.

[0117] Example:

[0118] The present invention provides an embodiment, which only uses the above method and system. The present invention is applicable to different clutch systems, wherein the clutch form, the number, ratio and size of friction elements can be changed. The clutch is set to perform constant speed sliding friction, the speed is 300rpm, the piston pressure p is 0.3MPa, the sliding friction is 10s, the number of friction pairs z is 6, h is 2mm, the number of teeth is 18, and the inner and outer ring radii of the friction element are r i 、r o The diameters are 86mm and 124mm, and the lubricating oil temperature is 40℃.

[0119] In the contact pressure calculation module, after inputting the clutch friction element layout and actual structural characteristic parameters, this module can be used to solve the pressure attenuation coefficient ξ between the steel plate and the friction plate in the process of transmitting axial contact pressure. s , f The values ​​are 0.0331 and 0.0561 respectively, and then the average contact pressure of each friction pair is calculated: p1~p6, as shown in Table 1.

[0120] Table 1

[0121]

[0122] In the friction torque calculation module, the friction torque transmitted by each friction pair is obtained according to the average contact pressure of each friction pair, and the total friction torque transmitted by the clutch is 340.4 N·m; in addition, according to the number of spline teeth of the dual steel plates, the friction torque transmitted by the single spline tooth of the steel plate 2 which is most prone to mechanical failure is 117.8 N·m, and the friction torque transmitted by the single spline tooth is 9.8 N·m.

[0123] In the temperature field calculation module, the heat flux density q of the friction pair is calculated according to the average contact pressure of each friction pair. i (r, t), and then calculate the temperature field of each friction pair of the clutch, such as Figure 3 The time-varying temperature rise characteristics of the steel sheet 2 are shown in FIG. Then, the radial temperature value of the steel sheet 2 at the end of the sliding friction is extracted as follows: Figure 4 As shown, the circumferential stress σ of steel sheet 2 is calculated s (r) and the in-plane bending moment M s Since the maximum radial temperature difference of steel sheet 2 is 29.3℃, the circumferential stresses are σ s.min =-36.6MPa,σ s.max =41.4MPa, the calculated bending moment in the plane is: M s =-18.84N·m.

[0124] In the failure critical value calculation module, the critical in-plane bending moment of the steel sheet 2 for thermal failure and mechanical failure is calculated to be 53.33 N·m, and the critical torque of the single spline tooth is 12.19 N·m.

[0125] In the failure assessment module, the data of the above modules are called to assess whether failure has occurred in the steel sheet 2. The steel sheet 2 is within the safety range and no maintenance measures are required.

[0126] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A clutch thermal load evaluation method considering a spline friction pair, characterized in that: include: Obtaining the axial contact pressure attenuation coefficient of the friction element; Calculating the average surface pressure of each friction pair of the clutch based on the axial contact pressure attenuation coefficient; Based on the average surface pressure, obtaining the friction torque and temperature field of each friction pair of the clutch; Calculating the single spline tooth torque and in-plane bending moment of each friction pair based on the friction torque and temperature field of each friction pair; Based on the dimensional characteristics of the dual steel sheets, the critical value of thermal-mechanical coupling failure is calculated; The clutch thermal load is evaluated based on the single spline tooth torque of each friction pair, the in-plane bending moment and the critical value of the thermal-mechanical coupling failure.

2. The clutch thermal load evaluation method considering the spline friction pair according to claim 1, characterized in that: The friction element comprises a friction plate and a steel plate.

3. The clutch thermal load evaluation method considering the spline friction pair according to claim 2, characterized in that: Obtaining the axial contact pressure attenuation coefficient of the friction element includes: respectively obtaining the axial contact pressure attenuation coefficient of the friction plate and the axial contact pressure attenuation coefficient of the steel plate; The method for obtaining the axial contact pressure attenuation coefficient of the friction plate is: Among them, ξ f is the axial contact pressure attenuation coefficient of the friction plate, μ is the friction coefficient of the surface friction pair, μ f is the key friction coefficient of the friction plate spline friction pair, R f is the pitch radius of the friction plate spline friction pair, α f is the pressure angle of the friction plate spline friction pair, R i is the inner ring radius of the friction element, R o is the outer ring radius of the friction element; The method for obtaining the axial contact pressure attenuation coefficient of the steel sheet is: Among them, ξ s is the axial pressure contact attenuation coefficient of the steel sheet, μ is the friction coefficient of the surface friction pair, μ s is the key friction coefficient of the steel spline friction pair, R s is the pitch radius of the steel spline friction pair, α s is the pressure angle of the steel spline friction pair.

4. The clutch thermal load evaluation method considering the spline friction pair according to claim 1, characterized in that: The method for calculating the average surface pressure of each friction pair of the clutch is: Among them, p i+1 is the contact pressure of the i+1th friction pair, ξ is the axial contact pressure attenuation coefficient, p is the clutch piston pressure, p i is the contact pressure of the i-th friction pair, i=1,2,3...M-2 is the friction plate number.

5. The clutch thermal load evaluation method considering the spline friction pair according to claim 3, characterized in that: The method for obtaining the friction torque of each friction pair of the clutch is: Where, M is the total friction torque, M i is the friction torque of the th friction plate.

6. The clutch thermal load evaluation method considering the spline friction pair according to claim 1, characterized in that: Acquiring the temperature field of each friction pair includes: Based on the average surface pressure, calculating the heat flux density of each friction pair; Based on the heat flux density, the temperature field of each friction pair is obtained.

7. The clutch thermal load evaluation method considering the spline friction pair according to claim 6, characterized in that: The method for calculating the heat flux density of each friction pair is: q i (r,t)=μ·p i ·ω(t)·r Among them, q i (r, t) is the heat flux density of each friction pair, ω(t) is the rotational angular velocity of the friction element, r represents the radial coordinate, and μ is the friction coefficient.

8. The clutch thermal load evaluation method considering the spline friction pair according to claim 1, characterized in that: Critical values ​​for calculating thermal-mechanical coupling include: The critical bending moment of the steel sheet causing thermal warping and the critical torque of the single spline teeth of the steel sheet are calculated respectively; Based on the critical bending moment of the steel sheet causing thermal warping and the critical torque of the single spline teeth of the steel sheet, a critical value of thermal-mechanical coupling failure is obtained.

9. A clutch thermal load evaluation system considering a spline friction pair, characterized in that: include: Contact pressure calculation module, friction torque calculation module, temperature field calculation module, failure critical value calculation module, failure assessment module; The contact pressure calculation module is used to obtain the average contact pressure of each friction pair; The temperature field calculation module is used to obtain the temperature field of each friction pair based on the average contact pressure of each friction pair; The failure critical value calculation module is used to calculate the failure critical value of the friction element; The failure assessment module is used to assess the friction element according to the failure threshold value.

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