A brake interface wear and fatigue crack prediction method based on complete thermal engine coupling

Abstract

The application discloses a brake interface wear and fatigue crack prediction method based on complete thermal-mechanical coupling, comprising the following steps: S1, establishing a finite element model, and discretizing total analysis time into multiple time periods; S2, starting finite element analysis, and calculating interface node contact pressure and node slip rate; S3, performing transient thermal-mechanical coupling analysis; S4, calculating node wear depth and wear direction, and updating grid information by using ALE technology; S5, judging whether the interface contact state is stable convergence; S6, ending analysis, unloading brake load, and obtaining brake disc residual stress; and S7, presetting a crack at the maximum residual stress, simulating crack propagation behavior, calculating stress intensity factor and brake disc fatigue life. The application can simulate tribological behaviors such as contact stress, temperature and wear, and realizes brake disc fatigue life prediction by taking residual stress after the thermal-mechanical coupling process as load input.

Description

Technical Field

[0001] This invention relates to the field of friction braking, and more particularly to a method for predicting brake interface wear and fatigue cracks based on complete thermomechanical coupling. Background Technology

[0002] During friction braking, brake pads experience severe wear, and the rapid accumulation of frictional heat at the braking interface causes the brake disc to heat up dramatically, generating thermal stress and initiating thermal cracks on the disc surface. These potential failure modes seriously threaten the safe operation of the braking system. Before designing and applying a product, it is usually necessary to verify and evaluate its performance to determine if the braking performance is up to standard and predict its service life. While testing brake friction pairs experimentally is the most direct and effective method, it requires expensive testing equipment and time-consuming fatigue testing, resulting in a long verification cycle and high costs. In contrast, finite element simulation (FEM) only requires numerical simulation of the braking process, and optimization iterations only require modifying the model and submitting the calculations. Therefore, FEM can significantly save costs and improve design efficiency.

[0003] Chinese Patent Application No. CN201911411319.2 discloses a method for predicting frictional vibration noise considering interface uncertainty and time-varying characteristics. This method proposes a prediction method for frictional vibration noise that considers the evolution of interface wear, and can simultaneously predict the evolution of interface wear and frictional vibration noise during the friction process. However, since this method does not consider the interface frictional heat factor, it cannot predict the temperature evolution during the friction process, nor the influence of temperature on wear and frictional vibration noise. Chinese Patent Application No. CN201410457959.8 discloses a simulation method for the sequential coupling of dry sliding frictional heat-stress-wear. This method calculates the interface heat flux density using the power equivalence method, then obtains the temperature field of the friction system using heat conduction analysis, and then performs stress analysis to obtain the contact stress and relative slip ratio at the interface nodes to calculate the node wear. While this method can obtain relatively accurate information on interface temperature and wear, its sequential coupling approach, relying on the equal power method to derive heat flux density and using an external heating source for heat conduction analysis, means that temperature generation is independent of the system's stress field. Therefore, this method can only study the effect of temperature on wear, failing to reflect the impact of changes in the stress field on the temperature field after interface wear. Furthermore, this method does not consider the influence of thermomechanical coupling on the system's fatigue life. Summary of the Invention

[0004] To address the problem that existing technologies cannot accurately predict fatigue life using contact stress, temperature, and wear, this invention proposes a method for predicting brake interface wear and fatigue cracks based on complete thermomechanical coupling, thus solving the aforementioned problem.

[0005] This application discloses a method for predicting brake interface wear and fatigue cracks based on complete thermomechanical coupling, including the following steps:

[0006] S1. Establish a finite element model, set the interactions and boundary conditions between each component, and perform mesh generation. Discretize the total analysis time into multiple time periods.

[0007] S2. Start the finite element analysis. First, apply the braking force load, then apply the brake disc rotation speed, and calculate the interface node contact pressure and node slip ratio under the initial incremental step.

[0008] S3. Calculate the frictional heat based on the contact pressure and slip ratio obtained in S2, and perform transient thermo-mechanical coupling analysis.

[0009] S4. Based on the contact pressure and slip ratio obtained in S2, call the UMESHMOTION subroutine to calculate the nodal wear depth and wear direction based on the Archard wear formula, and update the mesh information using ALE technology.

[0010] S5. Determine whether the interface contact state is stable and converged. If it is unstable, return to S1, reduce the initial time step increment, and recalculate steps S2-S4 until the interface contact state is stable and converged. If it is stable, increase the time step increment and enter the next analysis cycle.

[0011] S6. Repeat S2-S5. When the analysis time reaches the simulation time of the braking process, end the thermo-mechanical-wear coupling analysis, unload the braking load, and allow the brake disc to cool naturally to room temperature to obtain the residual stress of the brake disc.

[0012] S7. Pre-place a crack at the location of maximum residual stress, use the residual stress as a load, and simulate the crack propagation behavior using the extended finite element method to calculate the stress intensity factor and the fatigue life of the brake disc.

[0013] Preferably, step S1 includes the following steps:

[0014] Let the total analysis time be... Total analysis time Discretized There are several time periods, of which the simulation time for the braking process is denoted as . The initial time is denoted as The initial increment step is denoted as The maximum increment step is denoted as The time increment step is denoted as If the current time increment step If the circuit does not converge, reduce the time increment step. until convergence; if the current time increment is 1 step If convergence is not achieved, increase the time increment step. ,until Later The time increment step is [number], and the total analysis time is [time]. ,in For the first j The time increment of each increment step.

[0015] Preferably, the formula for calculating frictional heat is as follows:

[0016]

[0017] in, For energy conversion efficiency, The coefficient of friction, The contact pressure of the interface nodes under the initial incremental step. For nodes The distance to the center of the brake disc. For nodes coordinates Let be the coordinates of the center of the brake disc. For nodes Angular coordinates in polar coordinate system This refers to the rotational speed of the brake disc.

[0018] Preferably, the Arcard wear formula is as follows, assuming that the wear depth is related to the contact pressure. The power is directly proportional to:

[0019]

[0020] in, The wear coefficient is defined as the wear direction, which is the normal direction of the wear interface. This is a stress index.

[0021] Preferably, step S6 includes the following steps:

[0022] When the analysis time is greater than The thermal-mechanical-wear coupling analysis is completed at the end of the time, and the wear depth of each node at the interface is output. The braking force and brake disc speed are reduced to 0 within 1 second, so that the braking system dissipates braking heat under natural convection conditions and cools to room temperature, thus obtaining the residual stress of the brake disc.

[0023] Thermal convection satisfies the following conditions:

[0024]

[0025] in, For thermal convection density, The thermal convection coefficient, The surface temperature of the braking system. The ambient air temperature;

[0026] The formula for calculating the heat convection coefficient is as follows:

[0027]

[0028] in, The thermal conductivity of air, For characteristic length, is the Reynolds coefficient.

[0029] Preferably, the formula for calculating the stress intensity factor is as follows:

[0030]

[0031]

[0032] The direction and angle of crack propagation are:

[0033]

[0034] in, for Type eigenvalues, for Type eigenvalues, The number of complex eigenvalues ​​captured. The number of real eigenvalues ​​captured. The direction and angle of crack propagation. It is the generalized stress intensity coefficient. This is an intermediate matrix containing displacements. This is an intermediate matrix containing the stress angle distribution function, with subscripts... R Represents the actual part, subscript I It represents the virtual part.

[0035] Preferably, the fatigue life of the brake disc is calculated using the following formula:

[0036] Calculate the stress intensity factor amplitude:

[0037]

[0038] in, It is the largest element in the stress intensity factor matrix. It is the smallest element in the stress intensity factor matrix;

[0039] Predicting brake disc fatigue life based on the Paris formula:

[0040]

[0041] in, This represents the crack propagation rate. and These are material-related constants.

[0042] The beneficial effects of this invention are:

[0043] (1) This invention can accurately simulate the tribological behavior of the braking system, such as contact stress, temperature, and wear, and use the residual stress after the thermo-mechanical coupling process as the load input to analyze the crack propagation behavior of the brake disc and realize its fatigue life prediction. A complete damage and failure prediction model for the service of brake friction pairs is formed.

[0044] (2) Compared with the traditional sequential coupling method, the temperature field distribution simulated by this invention is more realistic and can reflect the interaction relationship between contact stress, temperature and wear, and can reveal the mechanism of their mutual influence. Attached Figure Description

[0045] Figure 1 This is a flowchart of the braking interface wear and fatigue crack prediction method based on complete thermomechanical coupling according to an embodiment of the present invention.

[0046] Figure 2 This is a schematic diagram of the finite element model of an embodiment of the present invention;

[0047] Figure 3 This is a schematic diagram of the residual stress distribution of the brake disc according to an embodiment of the present invention;

[0048] Figure 4 This is a schematic diagram of the pre-set crack location according to an embodiment of the present invention;

[0049] Figure 5 This is a schematic diagram of the crack propagation in the brake disc according to an embodiment of the present invention.

[0050] Figure 6 This is a schematic diagram comparing the experimental results and numerical simulation results of the interface temperature distribution evolution in an embodiment of the present invention.

[0051] Figure 7 The diagram shows a comparison between experimental results (a) and numerical simulation (b) of the wear distribution of the friction block in an embodiment of the present invention; a comparison between experimental and numerical simulation of radial normalized wear depth of the friction block (c); and a comparison between experimental and numerical simulation of tangential normalized wear depth of the friction block (d). Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided with reference to the accompanying drawings and embodiments.

[0053] This application discloses a method for predicting brake interface wear and fatigue cracks based on complete thermomechanical coupling, the process of which is as follows: Figure 1 As shown, it includes the following steps:

[0054] S1. Establish a simplified finite element model based on the experimental setup, and assign material properties to each component. Set the interactions and boundary conditions between the components, and perform mesh generation, discretizing the total analysis time into multiple time intervals.

[0055] The finite element model established in this embodiment is as follows: Figure 2 As shown, the finite element model mainly includes a pair of friction blocks and a brake disc. A reference point is established at the center of the brake disc, and this reference point is coupled and constrained to the inner surface of the center of the brake disc shaft hole. A constraint is applied around the reference point. x The rotational speed of the shaft drives the brake disc to rotate (in this embodiment, the rotational speed is 8 r / s); in order to fix the friction block and effectively apply the braking load, it is constrained along... y shaft and z Translational degree of freedom along the axis, freeing up the translational degree of freedom along the axis. x Translational degrees of freedom of the shaft. In simulating the braking friction process, a braking pressure of 0.75 MPa is first applied to the friction block, and then a rotational speed of 8 r / s is applied to the brake disc to simulate the braking process.

[0056] Set the contact properties between the friction block and the brake disc, where the friction block surface is set as the "follower surface," the brake disc surface is set as the "master surface," the normal property of the contact interface is set as "hard contact," the tangential friction force property is set as "penalty function," and the coefficient of friction is set to... Set it to 0.4. In the contact properties, enable the frictional heat generation option, indicating that the work done by friction during the friction process will be converted into frictional heat. Set the energy conversion coefficient to 0.9, meaning that 90% of the energy from the frictional work is converted into heat. Set the surface heat distribution coefficient to 0.08, meaning that 8% of the heat will be absorbed by the surface of the friction block, and 92% of the heat will be absorbed by the surface of the brake disc. Simultaneously, assuming an ambient temperature of 25℃, assign a predefined temperature field of 25℃ to the entire braking system.

[0057] To effectively simulate material removal due to wear, the friction block's mesh is designated as an ALE mesh domain, allowing for real-time redrawing of the mesh within this region during the simulation. Simultaneously, nodes on the contact surfaces of the brake disc and friction block are designated as ALE node constraints, enabling the node coordinates within this domain to be updated based on wear information. Ultimately, mesh redrawing is performed to simulate the wear material removal during braking.

[0058] Let the total analysis time be... Total analysis time Discretized There are several time periods, of which the simulation time for the braking process is denoted as . The initial time is denoted as The initial increment step is denoted as The maximum increment step is denoted as Setting a maximum time increment step is significant for automatically controlling the convergence of the simulation process. The time increment step is denoted as... If the current time increment step If the circuit does not converge, reduce the time increment step. until convergence; if the current time increment is 1 step If convergence is not achieved, increase the time increment step. ,until Later The time increment step is [number], and the total analysis time is [time]. ,in For the first j The time increment of each increment step.

[0059] S2. Start the finite element analysis. First, apply the braking force load, then apply the brake disc rotation speed, and calculate the interface node contact pressure and node slip ratio under the initial incremental step.

[0060] S3. Calculate the frictional heat based on the contact pressure and slip ratio obtained in S2, and perform transient thermo-mechanical coupling analysis.

[0061] According to the law of energy conversion, the magnitude of the frictional heat transferred at each node is:

[0062]

[0063] in, In this embodiment, the energy conversion efficiency is set to 0.9, which means that 90% of the work done by friction is converted into heat in the system. The coefficient of friction, The contact pressure of the interface nodes under the initial incremental step. For nodes The distance to the center of the brake disc. For nodes coordinates Let be the coordinates of the center of the brake disc. For nodes Angular coordinates in polar coordinate system This refers to the rotational speed of the brake disc.

[0064] S4. Based on the contact pressure and slip ratio obtained in S2, call the UMESHMOTION subroutine. Use the UMESHMOTION subroutine to retrieve the contact stress and temperature of the friction block contact nodes, and calculate the node wear depth and wear direction based on the Archard wear formula:

[0065] The Archard wear formula is as follows, assuming that the wear depth is related to the contact pressure. The power is directly proportional to:

[0066]

[0067] in, The wear coefficient, whose magnitude is temperature-dependent, can be expressed as a temperature-dependent polynomial: , For polynomial coefficients, For node temperature, the wear direction is specified as the normal direction of the wear interface. The pressure index is used. Since the hardness of the brake disc material is much greater than that of the friction block, its wear is negligible compared to that of the friction block. Therefore, this process only considers the wear of the friction block.

[0068] After the wear calculation is completed, the mesh of the friction block is redrawn and updated using ALE technology to simulate the material removal process caused by wear. The mesh is redrawn once for each incremental step.

[0069] S5. Determine whether the interface contact state is stable and converged. If it is unstable, return to S1, reduce the initial time step increment, and recalculate steps S2-S4 until the interface contact state is stable and converged. If it is stable, increase the time step increment and enter the next analysis cycle.

[0070] S6. Repeat S2-S5, when the analysis time is greater than... The thermo-mechanical-wear coupling analysis ends at the preset braking process simulation time. Then, the braking load is unloaded, allowing the brake disc to cool naturally to room temperature, and the residual stress of the brake disc is obtained. The distribution of the residual stress of the brake disc is as follows: Figure 3 As shown, the residual stress distribution of the brake disc is similar to the temperature distribution, mainly located on the ring belt traversed by the friction block.

[0071] When the analysis time is greater than The thermo-mechanical-wear coupling analysis is completed at the end of the time interval, and the wear depth of each node at the interface is output. Then, the braking force and brake disc speed are reduced to 0 within 1 second, so that the braking system is cooled to room temperature under natural convection conditions, and the residual stress of the brake disc is obtained.

[0072] Thermal convection satisfies the following conditions:

[0073]

[0074] in, For thermal convection density, The thermal convection coefficient is used in this implementation. The value is approximately 80 W / (m℃). The surface temperature of the braking system. The ambient air temperature is 25°C in this embodiment.

[0075] The formula for calculating the heat convection coefficient is as follows:

[0076]

[0077] in, The thermal conductivity of air, For characteristic length, is the Reynolds coefficient.

[0078] S7. Pre-place a crack at the location of maximum residual stress, use the residual stress as a load, and simulate the crack propagation behavior using the extended finite element method (XFEM) to calculate the stress intensity factor and the fatigue life of the brake disc.

[0079] After obtaining the residual stress of the brake disc, locate the position of its maximum residual stress. Then, create a new brake disc crack propagation analysis model and pre-place a crack at the location of the maximum residual stress. The crack is generally semi-elliptical, with a crack depth to crack length ratio of 1:4. Figure 4 As shown, the crack center is located at the location of maximum residual stress. A static analysis step is established, an XFEM crack is created, and the residual stress obtained from the fully coupled thermo-mechanical-wear analysis is applied as a predefined field to the newly created brake disc crack propagation model.

[0080] To simulate the propagation behavior of brake disc cracks under residual stress, a stress threshold for crack propagation needs to be set in the brake disc material parameters. In this embodiment, this threshold is set to 140 MPa, meaning that the crack will propagate when the maximum principal stress at the crack tip exceeds 140 MPa, and crack propagation follows the principle of maximum energy release. A schematic diagram of brake disc crack propagation is shown below. Figure 5 As shown, by Figure 5 As can be seen, the cracks propagate along the radial direction of the brake disc because the residual stress in the brake disc is mainly manifested as circumferential tensile stress.

[0081] Accurately solving for crack tip fracture parameters is crucial for predicting crack propagation behavior. To avoid relying on fine crack tip meshes with or without conventional quarter-node singularities, this embodiment employs a novel method for calculating stress intensity factors (SIFs). The derivation process is as follows:

[0082] The asymptotic displacement and stress near the crack tip are expressed as follows:

[0083]

[0084]

[0085] in, The number of complex eigenvalues ​​captured. The number of real eigenvalues ​​captured. The direction and angle of crack propagation. It is the generalized stress intensity coefficient. and This is an intermediate matrix containing displacement and stress angle distribution functions, with subscripts... Representative of the actual department, It represents the virtual part.

[0086] in and The solution method employs a special one-dimensional finite element eigenvalue analysis method. Using this method, the numerical characteristic solutions of the singular displacement field and stress field can be obtained from the following numerical characteristic equations:

[0087]

[0088] in, For variational symbols, For feature vectors, For eigenvalues, For the quality matrix, Here is the damping matrix. Here is the stiffness matrix.

[0089] Based on the Hellinger-Reissner variational principle, a functional is defined in the crack tip element region:

[0090]

[0091] in, Let be a matrix composed of unit outward normal vectors. Let be the boundary displacement vector. The unit volume is located near the crack tip. and These are the displacement components in a Cartesian coordinate system. , and These are the stress components in a rectangular coordinate system. Represents the boundary surface near the crack tip. Represents a volume element, Represents a micro-element of area.

[0092] To avoid in the domain The difficulty of singular terms in inner integration can be addressed by using the divergence theorem to transform the volume integral in equation (8) into the following surface integral:

[0093]

[0094] in, For the outer surface of the unit near the crack tip, Here is the stress matrix.

[0095] Element boundary displacement Displacement can be determined by the displacement of two adjacent nodes. and Interpolation representation, i.e.:

[0096]

[0097] in, To automatically satisfy the continuity of nodal displacements between adjacent elements, the interpolation function matrix obtained from the one-dimensional Lagrange interpolation method is used. The equation is... , , Attached get:

[0098]

[0099] in, , and They are respectively:

[0100]

[0101]

[0102] in, , These represent the element intermediate matrices containing displacement and stress angle distribution functions, respectively. This is the element stress matrix.

[0103] According to the functional conditions ,available:

[0104]

[0105] in, For nodal displacement.

[0106] The formula Attached available:

[0107]

[0108] Crack tip stiffness matrix It can be represented as:

[0109]

[0110] By performing finite element analysis on a cracked geometry, nodal displacements can be directly extracted from the solution of the global finite element equations. Then through formula - Numerical solutions for the singular stress field around the crack tip are obtained. Finally, the stress intensity factor at the crack tip is calculated using the numerical solutions for the singular stress field.

[0111]

[0112]

[0113] in, for Type eigenvalues, for Eigenvalues ​​of type.

[0114] The direction and angle of crack propagation are:

[0115]

[0116] Calculate the stress intensity factor amplitude:

[0117]

[0118] in, It is the largest element in the stress intensity factor matrix. It is the smallest element in the stress intensity factor matrix.

[0119] Predicting brake disc fatigue life based on the Paris formula:

[0120]

[0121] in, This represents the crack propagation rate. and These are material-related constants.

[0122] In a specific embodiment, experimental and simulation results for interface temperature distribution and interface wear distribution are compared. For example... Figure 6 The figure shows a comparison between experimental and simulation results of the interface temperature distribution evolution. It demonstrates that the numerical simulation accurately simulates the temperature field distribution evolution of the brake disc, and the simulated temperature distribution and magnitude are in good agreement with the experimental results. Figure 7The results show a comparison of the interface wear distribution. The results indicate that the wear distribution of the friction block obtained from the simulation is basically consistent with the experimental observation, which fully proves the reliability of the simulation method.

[0123] In summary, this application discloses a method for predicting brake interface wear and fatigue cracks based on complete thermomechanical coupling. This method can accurately simulate the contact stress, temperature, and tribological behavior of the braking system, and uses the residual stress after the thermomechanical coupling process as the load input to analyze the thermal crack propagation behavior of the brake disc, thereby predicting its fatigue life. Compared to traditional sequential coupling methods, the method proposed in this application simulates a temperature field distribution that is more realistic and can reflect the interaction between contact stress, temperature, and wear, revealing the mechanism of their mutual influence.

[0124] 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 present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for predicting brake interface wear and fatigue cracks based on complete thermomechanical coupling, characterized in that, Includes the following steps: S1. Establish a finite element model, set the interactions and boundary conditions between each component, and perform mesh generation. Discretize the total analysis time into multiple time periods. S2. Start the finite element analysis. First, apply the braking force load, then apply the brake disc rotation speed, and calculate the interface node contact pressure and node slip ratio under the initial incremental step. S3. Calculate the frictional heat based on the contact pressure and slip ratio obtained in S2, and perform transient thermo-mechanical coupling analysis. S4. Based on the contact pressure and slip ratio obtained in S2, call the UMESHMOTION subroutine to calculate the nodal wear depth and wear direction based on the Archard wear formula, and update the mesh information using ALE technology. S5. Determine whether the interface contact state is stable and converged. If it is unstable, return to S1, reduce the initial time step increment, and recalculate steps S2-S4 until the interface contact state is stable and converged. If it is stable, increase the time step increment and enter the next analysis cycle. S6. Repeat S2-S5. When the analysis time reaches the simulation time of the braking process, end the thermo-mechanical-wear coupling analysis, unload the braking load, and allow the brake disc to cool naturally to room temperature to obtain the residual stress of the brake disc. S7. Pre-place a crack at the location of maximum residual stress, use the residual stress as a load, and simulate the crack propagation behavior of the brake disc using the extended finite element method to calculate the stress intensity factor and the fatigue life of the brake disc.

2. The method for predicting brake interface wear and fatigue cracks based on complete thermomechanical coupling according to claim 1, characterized in that, S1 includes the following steps: Let the total analysis time be... Total analysis time Discretized There are several time periods, of which the simulation time for the braking process is denoted as . The initial time is denoted as The initial increment step is denoted as The maximum increment step is denoted as The time increment step is denoted as If the current time increment step If the circuit does not converge, reduce the time increment step. until convergence; if the current time increment is 1 step If convergence is not achieved, increase the time increment step. ,until Later The time increment step is [number], and the total analysis time is [time]. ,in For the first j The time increment of each increment step.

3. The method for predicting brake interface wear and fatigue cracks based on complete thermomechanical coupling according to claim 2, characterized in that, The formula for calculating frictional heat is as follows: in, For energy conversion efficiency, The coefficient of friction, The contact pressure of the interface nodes under the initial incremental step. For nodes The distance to the center of the brake disc. For nodes coordinates Let be the coordinates of the center of the brake disc. For nodes Angular coordinates in polar coordinate system This refers to the rotational speed of the brake disc.

4. The method for predicting brake interface wear and fatigue cracks based on complete thermomechanical coupling according to claim 3, characterized in that, The Archard wear formula is as follows, assuming that the wear depth is related to the contact pressure. The power is directly proportional to: in, The wear coefficient is defined as the wear direction, which is the normal direction of the wear interface. This is a stress index.

5. The method for predicting brake interface wear and fatigue cracks based on complete thermomechanical coupling according to claim 4, characterized in that, S6 includes the following steps: When the analysis time is greater than The thermal-mechanical-wear coupling analysis is completed at the end of the time, and the wear depth of each node at the interface is output. The braking force and brake disc speed are reduced to 0 within 1 second, so that the braking system dissipates braking heat under natural convection conditions and cools to room temperature, thus obtaining the residual stress of the brake disc. Heat convection satisfies the following conditions: in, For thermal convection density, The thermal convection coefficient, The surface temperature of the braking system. The ambient air temperature; The formula for calculating the heat convection coefficient is as follows: in, The thermal conductivity of air, For characteristic length, is the Reynolds coefficient.

6. The method for predicting brake interface wear and fatigue cracks based on complete thermomechanical coupling according to claim 5, characterized in that, The formula for calculating the stress intensity factor is as follows: in, for Type eigenvalues, for Type eigenvalues, The number of complex eigenvalues ​​captured. The number of real eigenvalues ​​captured. The direction and angle of crack propagation. It is the generalized stress intensity coefficient. This is an intermediate matrix containing the stress angle distribution function, with subscripts... R Represents the actual part, subscript I It represents the virtual part.

7. The method for predicting brake interface wear and fatigue cracks based on complete thermomechanical coupling according to claim 6, characterized in that, The fatigue life of the brake disc is calculated using the following formula: Calculate the stress intensity factor amplitude: in, It is the largest element in the stress intensity factor matrix. It is the smallest element in the stress intensity factor matrix; Predicting brake disc fatigue life based on the Paris formula: in, This represents the crack propagation rate. and These are material-related constants.

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