A clutch friction element temperature field and thermal failure calculation method and system

Abstract

The present invention discloses a clutch friction element temperature field and thermal failure calculation method and system, belonging to the technical field of automobile clutch. The method comprises: S1, constructing a clutch model; S2, calculating the contact pressure between friction elements based on the clutch model and extracting the radial contact pressure; Fourier integral functioning the radial contact pressure to obtain the contact pressure function; S3, conducting an engagement test on the clutch, collecting the speed data during the clutch engagement process; and determining the convective heat transfer coefficient of the friction element based on the speed data; S4, calculating the total heat flux density between the friction elements based on the contact pressure function and the speed data; S5, calculating the radial temperature of the dual steel sheets based on the convective heat transfer coefficient and the total heat flux density; and obtaining the circumferential stress based on the radial temperature; S6, calculating the in-plane bending moment of the friction element based on the circumferential stress, and evaluating the thermal failure trend of the friction element based on the in-plane bending moment.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile clutches, and in particular relates to a method and system for calculating the temperature field and thermal failure of a clutch friction element. Background Art

[0002] The wet shift clutch is widely used in vehicle transmissions 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 transmissions. During the wet clutch sliding process, the axial ends of the friction element are subjected to the uniform surface pressure of the piston and the local constraint of the retaining spring only close to the outer ring, resulting in radial non-uniform distribution of the friction interface pressure and pressure attenuation between multiple friction pairs, which in turn leads to radial non-uniform heat flow input at the friction interface and different temperature rises of each friction element. However, excessive radial temperature difference of the friction element will lead to its failure, affecting the reliability and driving integrity of the transmission.

[0003] The clutch friction element has both circumferential rotation and axial displacement, so it is difficult to arrange conventional sensors for temperature measurement. Based on the existing technology, in the temperature measurement test of the clutch friction element, the passive end of the clutch is mostly fixed. Since the dual steel plate and the clutch passive end gear are connected by splines, the clutch dual steel plate is also relatively static. The temperature of the friction element is measured by drilling holes on the side plane of the dual steel plate and inserting thermocouples. This method cannot obtain the actual temperature of the friction plate surface, and the measurement points are limited. In addition, the side plane processing is difficult. This temperature measurement method is costly and has low accuracy.

[0004] The clutch temperature test can also rely on the construction of a temperature model to infer the surface temperature of the clutch friction plate based on the real-time working conditions. Patent ZL202111278538.5 provides a method for constructing an automatic transmission clutch temperature simulation model. Based on the actual vehicle information, the theoretical temperature of the clutch dual steel plate and the oil outlet can be obtained. Patent CN202310332141.2 provides a clutch temperature prediction method, which predicts the final temperature of the clutch based on the original temperature value of the clutch, the temperature correction coefficient and the predicted temperature rise. Patent ZL202110087699.X proposes a dry clutch temperature prediction method based on dynamic neural network time series prediction. The above methods do not take into account the influence of the actual structural characteristics of the clutch on the contact pressure distribution characteristics of the friction element. The clutch temperature rise laws obtained are all average temperature rises. The relevant information cannot reflect the radial temperature characteristics of the friction plate, nor can it be determined whether the friction plate is at risk of thermal failure. Summary of the invention

[0005] The present invention aims to address the deficiencies of the prior art and proposes a clutch friction element temperature field and thermal failure calculation method and system. The actual structural characteristics of the clutch are taken into consideration to obtain the actual contact pressure distribution characteristics between the friction elements, thereby obtaining the actual temperature field between different friction elements, evaluating whether the friction elements have a risk of thermal failure, determining the position characteristics of the friction elements that are prone to failure, and giving a timely failure warning.

[0006] To achieve the above object, the present invention provides the following solution: a method for calculating the temperature field and thermal failure of a clutch friction element, comprising the following steps:

[0007] S1. Collecting the operating parameters during the clutch engagement process, and constructing a clutch model through finite element software based on the operating parameters and the structural characteristics of the clutch; the operating parameters include: initial speed, piston pressure, number of friction pairs, lubrication flow, load inertia, inner and outer ring radii of the friction element, thickness of the dual steel sheet, width of the retaining spring, and ambient temperature;

[0008] S2. Calculating the contact pressure between the friction elements based on the clutch model; obtaining a surface contact stress distribution cloud map based on the contact pressure, and extracting radial contact pressure based on the surface contact stress distribution cloud map; performing Fourier integral function on the radial contact pressure to obtain a contact pressure function;

[0009] S3, performing an engagement test on the clutch, collecting speed data during the clutch engagement process; and determining a convection heat transfer coefficient of the friction element based on the speed data;

[0010] S4, calculating the total heat flux density between the friction elements based on the contact pressure function and the rotation speed data;

[0011] S5, calculating the radial temperature of the dual steel sheets based on the convection heat transfer coefficient and the total heat flux density; and obtaining the circumferential stress based on the radial temperature;

[0012] S6. Calculate the in-plane bending moment of the friction element based on the circumferential stress, and evaluate the thermal failure trend of the friction element based on the in-plane bending moment.

[0013] Further preferably, the calculation method of the convection heat transfer coefficient includes:

[0014]

[0015] In the formula, h i (t) and h o (t) represents the convective heat transfer coefficient at the inner ring radius and the outer ring radius of the friction element; ω(t) represents the rotational angular velocity of the friction element; r i , r0 represent the inner ring radius and outer ring radius of the friction element respectively;

[0016] Among them, ω(t)=2πn(t), n(t) represents the rotation speed.

[0017] Further preferably, the calculation method of the total heat flux density includes:

[0018] q k (t,r)=μ·p k (r)·ω(t)·r,

[0019] Where μ represents the friction coefficient; p k (r) represents the contact pressure function; ω(t) represents the rotational angular velocity of the friction element; r represents the radial coordinate.

[0020] Further preferably, S5 includes:

[0021] S51, based on the difference in thermal conductivity of the dual steel plate and the friction plate and the total heat flux density, determine the heat flux ratio entering the friction plate, and obtain the heat flux density entering the kth surface into the friction plate and the dual steel plate respectively;

[0022] S52, based on the convection heat transfer coefficient and the heat flux density of the dual steel sheet, calculate the temperature T of the dual steel sheet at different positions at the coordinate (r, θ) at time t s (r,θ,t);

[0023] S53, Extract T c At the moment, the radial temperature changes of all friction elements with a circumferential angle of 0° are obtained by Fourier transformation to obtain the discrete function of the radial temperature of each friction element;

[0024] S54. Based on the discrete function of the radial temperature and thermal stress theory, the circumferential stress is obtained.

[0025] Further preferably, the method for calculating the circumferential stress includes:

[0026]

[0027] In the formula, σ s represents circumferential stress; α represents thermal expansion coefficient; E represents elastic modulus; r represents radial coordinate; r i , r0 represent the inner ring radius and outer ring radius of the friction element respectively; T s (r) represents the discrete function of radial temperature.

[0028] Further preferably, the method for calculating the in-plane bending moment includes:

[0029]

[0030] Where Ms represents the in-plane bending moment; h represents the thickness of the friction element; r i , r0 represent the inner ring radius and outer ring radius of the friction element respectively; r represents the radial coordinate; σ s (r) represents the circumferential stress.

[0031] Further preferably, the method for evaluating the thermal failure tendency of the friction element based on the in-plane bending moment comprises:

[0032]

[0033] Where M s represents the in-plane bending moment.

[0034] The present invention also provides a clutch friction element temperature field and thermal failure calculation system, the calculation system is used to apply the above calculation method, including: a modeling system, a contact pressure system, a lubrication and cooling system, a heat flux system, a circumferential stress system and an evaluation system;

[0035] The modeling system is used to collect operating parameters during the clutch engagement process, and to construct a clutch model through finite element software based on the operating parameters and the structural characteristics of the clutch; the operating parameters include: initial speed, piston pressure, number of friction pairs, lubrication flow, load inertia, inner and outer ring radii of the friction element, thickness of the dual steel sheet, width of the retaining spring, and ambient temperature;

[0036] The contact pressure system is used to calculate the contact pressure between the friction elements based on the clutch model; obtain a surface contact stress distribution cloud map based on the contact pressure, and extract radial contact pressure based on the surface contact stress distribution cloud map; perform Fourier integral function on the radial contact pressure to obtain a contact pressure function;

[0037] The lubrication and cooling system is used to perform an engagement test on the clutch, collect speed data during the clutch engagement process; and determine the convection heat transfer coefficient of the friction element based on the speed data;

[0038] The heat flux system is used to calculate the total heat flux between the friction elements based on the contact pressure function and the speed data;

[0039] The circumferential pressure system is used to calculate the radial temperature of the dual steel sheets based on the convection heat transfer coefficient and the total heat flux density; and to obtain the circumferential stress based on the radial temperature;

[0040] The evaluation system is used to calculate the in-plane bending moment of the friction element based on the circumferential stress, and to evaluate the thermal failure tendency of the friction element based on the in-plane bending moment.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention provides a clutch friction element temperature field and thermal failure calculation method and system. Considering the actual structural characteristics of the clutch, the actual radial contact pressure, convection heat dissipation coefficient, heat flux density, temperature, circumferential stress, in-plane bending moment, etc. of all friction elements in the clutch system can be obtained. The working state of the clutch can be accurately judged, the temperature field change trend can be analyzed, the position characteristics of the friction elements that are prone to failure can be obtained, and the clutch can be evaluated for thermal failure risks. It has a positive effect on reducing clutch ablation and is suitable for large-scale promotion and application. In addition, the present invention can realize the solution of the real-time temperature field of friction elements at different positions, and obtain the radial temperature field of the dual steel sheets at different positions at different times, which solves the disadvantage that the traditional method can only solve the average temperature rise of the clutch. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0044] Figure 1 A schematic diagram of a clutch friction element temperature field and thermal failure calculation method according to an embodiment of the present invention;

[0045] Figure 2 A schematic diagram of the structure of a clutch friction element temperature field and thermal failure calculation system according to an embodiment of the present invention;

[0046] Figure 3 This is a schematic diagram of a surface contact stress distribution cloud diagram when k=5 in an embodiment of the present invention;

[0047] Figure 4 Schematic diagram of radial contact pressure of Fourier integral function of different friction surfaces in an embodiment of the present invention;

[0048] Figure 5 Schematic diagram of the temperature of the dual steel sheets according to an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] Embodiment 1:

[0052] like Figure 1 As shown, this embodiment provides a clutch friction element temperature field and thermal failure calculation method, comprising the following steps:

[0053] S1. Collect the operating parameters of the clutch during engagement, and build a clutch model based on the operating parameters and the structural characteristics of the clutch using ABAQUS finite element software; the piston is subjected to an axial hydraulic pressure of p. c , referred to as piston pressure p c , the dual steel plates and friction plates are arranged alternately, and the retaining spring is completely fixed. The operating parameters include: initial speed n c , friction pair number z, lubrication flow L, load inertia I, inner and outer ring radius r of the friction element i 、r o , thickness of the dual steel sheet h, width of the retaining ring w and ambient temperature T c .

[0054] S2. Calculate the contact pressure between the friction elements based on the clutch model; obtain the surface contact stress distribution cloud map based on the contact pressure, and extract the radial contact pressure based on the surface contact stress distribution cloud map; perform Fourier integral function on the radial contact pressure of different friction surfaces to obtain the contact pressure function p k (r), where k represents the number of friction surfaces of the dual steel plates and r represents the radial coordinate.

[0055] S3. Perform an engagement test on the clutch, collect the speed data n(t) during the clutch engagement process through a speed torque sensor, where t represents the time; and determine the convection heat transfer coefficient at the inner ring and the outer ring of the friction element based on the speed data.

[0056] In this embodiment, the calculation method of the convective heat transfer coefficient includes:

[0057]

[0058] In the formula, h i (t) and h o (t) represents the convective heat transfer coefficient at the inner ring radius and the outer ring radius of the friction element; ω(t) represents the rotational angular velocity of the friction element; r i , r0 represent the inner ring radius and outer ring radius of the friction element respectively; wherein, ω(t)=2πn(t), n(t) represents the rotational speed.

[0059] S4. Calculate the total heat flux density between each friction element based on the contact pressure function and the rotational speed data.

[0060] In this embodiment, the calculation method of the total heat flux includes:

[0061] q k (t,r)=μ·p k (r)·ω(t)·r,

[0062] Where μ represents the friction coefficient; p k (r) represents the contact pressure function; ω(t) represents the rotational angular velocity of the friction element; r represents the radial coordinate.

[0063] S5. Calculate the radial temperature of the dual steel sheets based on the convection heat transfer coefficient and the total heat flux density; and obtain the circumferential stress based on the radial temperature.

[0064] Specifically, S5 includes:

[0065] S51. Based on the thermal conductivity difference of the dual steel plate and the friction plate and the total heat flux density, determine the heat flux ratio entering the friction plate, and obtain the heat flux density q entering the kth surface into the friction plate and the dual steel plate respectively. kf (t,r) and q ks (t,r).

[0066] S52, based on the convection heat transfer coefficient and the heat flux density of the dual steel sheet, calculate the temperature T of the dual steel sheet at different positions at the coordinate (r, θ) at time t s (r,θ,t); subscript s is the position of the dual steel sheet, r and θ are the radial coordinate and circumferential coordinate, respectively.

[0067] S53, Extraction c At the moment, the radial temperature change T of all friction elements with a circumferential angle of 0° s (r,0°,t c ), the three-dimensional temperature coordinate is simplified to one dimension, and the discrete function T of the radial temperature of each friction element is obtained by Fourier transform. s (r).

[0068] S54. Based on the discrete function of radial temperature and thermal stress theory, the circumferential stress is obtained.

[0069] In this embodiment, the calculation method of the circumferential stress includes:

[0070]

[0071] In the formula, σ s represents circumferential stress; α represents thermal expansion coefficient; E represents elastic modulus; r represents radial coordinate; r i, r0 represent the inner ring radius and outer ring radius of the friction element respectively; T s (r) represents the discrete function of radial temperature.

[0072] S6. Calculate the in-plane bending moment of the friction element based on the circumferential stress, and evaluate the thermal failure trend of the friction element based on the in-plane bending moment.

[0073] In this embodiment, the calculation method of the in-plane bending moment includes:

[0074]

[0075] Where M s represents the in-plane bending moment; h represents the thickness of the friction element; r i , r0 represent the inner ring radius and outer ring radius of the friction element respectively; r represents the radial coordinate; σ s (r) represents the circumferential stress.

[0076] Methods for evaluating the thermal failure tendency of friction components based on in-plane bending moments include:

[0077]

[0078] Where M s represents the in-plane bending moment.

[0079] Embodiment 2:

[0080] This embodiment provides an application example for describing the application of the method proposed in the present invention in detail.

[0081] The present invention is applicable to different clutch systems, in which the clutch configuration, the number, ratio and size of friction elements can vary. During the clutch engagement process, the initial speed n c is 150rpm, piston pressure p c The pressure is 0.1 MPa, the number of friction pairs z is 6 (4 dual steel plates, 3 friction plates arranged alternately), the thickness of the dual steel plates h is 2 mm, the lubrication flow L is 2 L / min, and the load inertia I is 0.27 kg·m 2 The radii of the inner and outer rings of the friction element are r i 、r o 86mm, 124mm, the width of the spring is 5mm, and the ambient temperature is T c At 40°C, the bonding time t c is 10s.

[0082] Input the actual structural characteristic parameters of the clutch and build the clutch model through finite element software. Calculate the contact pressure between the friction elements based on the clutch model; obtain the surface contact stress distribution cloud map based on the contact pressure, such as Figure 3As shown. The radial contact pressure is extracted based on the surface contact stress distribution cloud map; the radial contact pressure of different friction surfaces is functionalized by Fourier integral. In this embodiment, when k=5, the contact pressure function is:

[0083] p5(r)=1.156e5+8.69e4·cos(0.09831·r)-1.453e4·sin(0.09831·r)+2.667e4·cos(2×

[0084] 0.09831·r)-4286·sin(2×0.09831·r).

[0085] like Figure 4 As shown. After that, the above-mentioned operating parameters during the clutch engagement process are input, and the speed information of this time period is first obtained, and the convection heat dissipation coefficient at the inner and outer diameters of the friction element is obtained based on the speed information. And the total heat flux density is calculated based on the speed information and the radial contact pressure after Fourier integral function. And according to the difference in thermal conductivity between the dual steel plate and the friction plate, the proportion of heat flow entering the friction plate is determined, and the heat flux density of the friction plate and the dual steel plate at different positions is calculated. Based on the convection heat transfer coefficient and the heat flux density of the dual steel plate, the temperature T of the dual steel plate at different positions at the coordinate (r, θ) at time t is calculated. s (r,θ,t); subscript s is the position of the dual steel sheet, r and θ are radial and circumferential coordinates respectively. c At the moment, the radial temperature change T of all friction elements with a circumferential angle of 0° s (r,0°,t c ), the three-dimensional temperature coordinate is simplified to one dimension, and the discrete function T of the radial temperature of each friction element is obtained by Fourier transform. s (r). Figure 5 As shown in the figure, based on the discrete function of radial temperature and thermal stress theory, the circumferential stress is obtained, and the in-plane bending moment is calculated based on the circumferential stress. Since the maximum radial temperature difference of steel sheet 3 is 55.2℃, the circumferential stress is σ s.min =-84.44MPa,σ s.max =61.94MPa, the calculated bending moment in the plane is: M s =42.22N·m. According to the magnitude of the bending moment in the plane of the friction element, the thermal failure trend of the friction element is evaluated. Steel sheet 3 has a risk of thermal failure, and the other steel sheets are in a safe area.

[0086] Embodiment three:

[0087] like Figure 2As shown, this embodiment provides a clutch friction element temperature field and thermal failure calculation system, including: a modeling system, a contact pressure system, a lubrication and cooling system, a heat flux system, a circumferential stress system and an evaluation system.

[0088] The modeling system is used to collect the operating parameters during the clutch engagement process, and build a clutch model based on the operating parameters and the structural characteristics of the clutch using ABAQUS finite element software. The operating parameters include: initial speed n c , piston pressure p c , friction pair number z, lubrication flow L, load inertia I, inner and outer ring radius r of the friction element i 、r o , thickness of the dual steel sheet h, width of the retaining ring w and ambient temperature T c .

[0089] The contact pressure system is used to calculate the contact pressure between the friction elements based on the clutch model; obtain the surface contact stress distribution cloud map based on the contact pressure, and extract the radial contact pressure based on the surface contact stress distribution cloud map; perform Fourier integral function on the radial contact pressure of different friction surfaces to obtain the contact pressure function p k (r), where k represents the number of friction surfaces of the dual steel plates and r represents the radial coordinate.

[0090] The lubrication and cooling system is used to perform clutch engagement tests. The speed data n(t) during the clutch engagement process is collected through a speed torque sensor, where t represents the time; and the convection heat transfer coefficients at the inner and outer rings of the friction element are determined based on the speed data.

[0091] In this embodiment, the calculation method of the convective heat transfer coefficient includes:

[0092]

[0093] In the formula, h i (t) and h o (t) represents the convective heat transfer coefficient at the inner ring radius and the outer ring radius of the friction element; ω(t) represents the rotational angular velocity of the friction element; r i , r0 represent the inner ring radius and outer ring radius of the friction element respectively; wherein, ω(t)=2πn(t), n(t) represents the rotational speed.

[0094] The Heat Flux system is used to calculate the total heat flux between the friction elements based on the contact pressure function and the speed data.

[0095] In this embodiment, the calculation method of the total heat flux includes:

[0096] q k (t,r)=μ·p k(r)·ω(t)·r,

[0097] Where μ represents the friction coefficient; p k (r) represents the contact pressure function; ω(t) represents the rotational angular velocity of the friction element; r represents the radial coordinate.

[0098] The circumferential pressure system is used to calculate the radial temperature of the dual steel sheet based on the convective heat transfer coefficient and the total heat flux density, and obtain the circumferential stress based on the radial temperature. Specifically, the circumferential pressure system includes: a proportional module, a first calculation module, an extraction module, and a second calculation module.

[0099] The proportion module is used to determine the heat flux ratio entering the friction plate based on the thermal conductivity difference of the dual steel plate and the friction plate and the total heat flux density, and obtain the heat flux density q entering the kth surface into the friction plate and the dual steel plate respectively. kf (t,r) and q ks (t,r).

[0100] The first calculation module is used to calculate the temperature T of the dual steel sheet at different positions at the coordinate (r, θ) at time t based on the convection heat transfer coefficient and the heat flux density of the dual steel sheet. s (r,θ,t); subscript s is the position of the dual steel sheet, r and θ are the radial coordinate and circumferential coordinate, respectively.

[0101] The extraction module is used to extract t c At the moment, the radial temperature change T of all friction elements with a circumferential angle of 0° s (r,0°,t c ), the three-dimensional temperature coordinate is simplified to one dimension, and the discrete function T of the radial temperature of each friction element is obtained by Fourier transform. s (r).

[0102] The second calculation module is used to obtain the circumferential stress based on the discrete function of radial temperature and thermal stress theory.

[0103] In this embodiment, the calculation method of the circumferential stress includes:

[0104]

[0105] In the formula, σ s represents circumferential stress; α represents thermal expansion coefficient; E represents elastic modulus; r represents radial coordinate; r i , r0 represent the inner ring radius and outer ring radius of the friction element respectively; T s (r) represents the discrete function of radial temperature.

[0106] The evaluation system is used to calculate the in-plane bending moment of the friction element based on the circumferential stress, and to evaluate the thermal failure tendency of the friction element based on the in-plane bending moment.

[0107] In this embodiment, the calculation method of the in-plane bending moment includes:

[0108]

[0109] Where M s represents the in-plane bending moment; h represents the thickness of the friction element; r i , r0 represent the inner ring radius and outer ring radius of the friction element respectively; r represents the radial coordinate; σ s (r) represents the circumferential stress.

[0110] Methods for evaluating the thermal failure tendency of friction components based on in-plane bending moments include:

[0111]

[0112] Where M s represents the in-plane bending moment.

[0113] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A clutch friction element temperature field and thermal failure calculation method, characterized in that: The following steps are involved: S1. Collecting the operating parameters during the clutch engagement process, and constructing a clutch model through finite element software based on the operating parameters and the structural characteristics of the clutch; the operating parameters include: initial speed, piston pressure, number of friction pairs, lubrication flow, load inertia, inner and outer ring radii of the friction element, thickness of the dual steel sheet, width of the retaining spring, and ambient temperature; S2. Calculating the contact pressure between the friction elements based on the clutch model; obtaining a surface contact stress distribution cloud map based on the contact pressure, and extracting radial contact pressure based on the surface contact stress distribution cloud map; performing Fourier integral function on the radial contact pressure to obtain a contact pressure function; S3. Performing an engagement test on the clutch to collect speed data during the clutch engagement process; and determining the convection heat transfer coefficient of the friction element based on the speed data; the calculation method of the convection heat transfer coefficient includes: In the formula, h i (t) and h o (t) represents the convective heat transfer coefficient at the inner ring radius and the outer ring radius of the friction element; ω(t) represents the rotational angular velocity of the friction element; r i , r0 represent the inner ring radius and outer ring radius of the friction element respectively; Among them, ω(t) = 2πn(t), n(t) represents the speed; S4. Calculating the total heat flux density between the friction elements based on the contact pressure function and the speed data; the calculation method of the total heat flux density includes: q k (t,r)=μ·p k (r)·ω(t)·r, Where μ represents the friction coefficient; p k (r) represents the contact pressure function; ω(t) represents the rotational angular velocity of the friction element; r represents the radial coordinate; S5, calculating the radial temperature of the dual steel sheets based on the convection heat transfer coefficient and the total heat flux density; and obtaining the circumferential stress based on the radial temperature; S5 includes: S51, based on the difference in thermal conductivity of the dual steel plate and the friction plate and the total heat flux density, determine the heat flux ratio entering the friction plate, and obtain the heat flux density entering the kth surface into the friction plate and the dual steel plate respectively; S52, based on the convection heat transfer coefficient and the heat flux density of the dual steel sheet, calculate the temperature T of the dual steel sheet at different positions at the coordinate (r, θ) at time t s (r,θ,t); S53, Extract T c At the moment, the radial temperature changes of all friction elements with a circumferential angle of 0° are obtained by Fourier transformation to obtain the discrete function of the radial temperature of each friction element; S54, obtaining the circumferential stress based on the discrete function of the radial temperature and thermal stress theory; S6. Calculate the in-plane bending moment of the friction element based on the circumferential stress, and evaluate the thermal failure trend of the friction element based on the in-plane bending moment.

2. A clutch friction element temperature field and thermal failure calculation method according to claim 1, characterized in that: The calculation method of the circumferential stress includes: In the formula, σ s represents circumferential stress; α represents thermal expansion coefficient; E represents elastic modulus; r represents radial coordinate; r i , r0 represent the inner ring radius and outer ring radius of the friction element respectively; T s (r) represents the discrete function of radial temperature.

3. A clutch friction element temperature field and thermal failure calculation method according to claim 1, characterized in that: The calculation method of the in-plane bending moment includes: Where M s represents the in-plane bending moment; h represents the thickness of the friction element; r i , r0 represent the inner ring radius and outer ring radius of the friction element respectively; r represents the radial coordinate; σ s (r) represents the circumferential stress.

4. A clutch friction element temperature field and thermal failure calculation method according to claim 1, characterized in that: The method for evaluating the thermal failure tendency of a friction element based on the in-plane bending moment includes: Where M s represents the in-plane bending moment.

5. A clutch friction element temperature field and thermal failure calculation system, the calculation system using the calculation method according to any one of claims 1 to 4, characterized in that: include: Modeling system, contact pressure system, lubrication and cooling system, heat flux system, circumferential stress system and evaluation system; The modeling system is used to collect operating parameters during the clutch engagement process, and to construct a clutch model through finite element software based on the operating parameters and the structural characteristics of the clutch; the operating parameters include: initial speed, piston pressure, number of friction pairs, lubrication flow, load inertia, inner and outer ring radii of the friction element, thickness of the dual steel sheet, width of the retaining spring, and ambient temperature; The contact pressure system is used to calculate the contact pressure between the friction elements based on the clutch model; obtain a surface contact stress distribution cloud map based on the contact pressure, and extract radial contact pressure based on the surface contact stress distribution cloud map; perform Fourier integral function on the radial contact pressure to obtain a contact pressure function; The lubrication and cooling system is used to perform an engagement test on the clutch, collect speed data during the clutch engagement process; and determine the convection heat transfer coefficient of the friction element based on the speed data; The heat flux system is used to calculate the total heat flux between the friction elements based on the contact pressure function and the speed data; The circumferential stress system is used to calculate the radial temperature of the dual steel sheets based on the convection heat transfer coefficient and the total heat flux density; and to obtain the circumferential stress based on the radial temperature; The evaluation system is used to calculate an in-plane bending moment of the friction element based on the circumferential stress, and to evaluate a thermal failure tendency of the friction element based on the in-plane bending moment.

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