Simulation test method for automobile transmission system
By employing a simulation method that couples multibody dynamics, thermal networks, and fluid dynamics, the high cost and low accuracy of traditional testing methods are solved, enabling high-precision life prediction of automotive transmission systems, especially accurate analysis under extreme conditions.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHONGQING UNIV OF TECH
- Filing Date
- 2025-12-31
- Publication Date
- 2026-04-17
AI Technical Summary
Traditional automotive transmission system testing methods are costly, time-consuming, and difficult to reproduce extreme conditions. Furthermore, existing simulation methods fail to accurately predict the internal dynamic details and lifespan of the system.
A three-dimensional geometric model is constructed using a strongly coupled iterative solution framework of multibody dynamics, thermal network, and fluid dynamics. The multibody dynamics equations, thermal network model, and fluid dynamics model of the flexible body are considered, and combined with a nonlinear continuous damage mechanics model, to simulate the dynamic performance and fatigue life of the transmission system.
Accurate simulation of the mutual conversion of mechanical energy and thermal energy in the transmission system improves the accuracy of simulation results, especially the accuracy of vibration and thermal failure prediction under high-speed and heavy-load conditions, and enhances the confidence of life prediction.
Smart Images
Figure CN121881902A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of automotive simulation testing, and more specifically to a simulation testing method for an automotive transmission system. Background Technology
[0002] Traditional automotive transmission system testing relies on physical prototypes and bench tests, which suffers from drawbacks such as high cost, long cycle time, difficulty in reproducing extreme operating conditions, and inability to explore internal dynamic details. Existing simulation methods (such as pure dynamic simulation) typically treat components as rigid bodies or perform only simple fatigue analysis, ignoring the complex multi-physics coupling effects within the system (such as thermal deformation caused by gear meshing heat generation, the impact of changes in lubricating oil viscosity-temperature characteristics on efficiency, and the transmission of vibration and noise), resulting in insufficient prediction accuracy and difficulty in accurately predicting the actual lifespan and dynamic behavior of the transmission system. Summary of the Invention
[0003] To address the aforementioned shortcomings in the existing technology, this invention provides a simulation test method for automotive transmission systems, enabling coordinated testing of the dynamic performance, thermal characteristics, and fatigue life of automotive transmission systems.
[0004] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: A simulation test method for an automotive transmission system is provided, comprising the following steps: S1: Based on the dimensional parameters of the automotive transmission system, draw a three-dimensional geometric model of the automotive transmission system and import it into multibody dynamics simulation software, assigning material properties, constraint pairs and force elements to different components; S2: Construct mutually coupled multibody dynamics equations, thermal network model equations, and fluid dynamics models considering flexible bodies; S3: Set the initial and boundary conditions for the simulation of the automotive transmission system, under temperature... T Solve the multibody dynamics equations, fluid dynamics model equations, and thermal network model equations considering flexible bodies under different operating conditions, and output the stress time history of the automotive transmission system at the convergence of the temperature field and dynamic state under different operating conditions. ; S4: Construct a nonlinear continuous damage mechanics model based on the stress time history. Damage variables are calculated under different driving cycles to assess the fatigue life of the automotive transmission system.
[0005] Furthermore, the multibody dynamics equations for a flexible body are as follows: ; in, The mass matrix of the automotive transmission system. It is the generalized coordinate system of the automobile transmission system. With temperatureT The function, the mass matrix Consider the slight changes in mass distribution caused by thermal deformation of the automotive transmission system; These are the velocity vector and acceleration vector of the automotive transmission system, respectively. The damping matrix of the automotive transmission system. Time-varying meshing stiffness and time-varying damping The function, t For time, Here is the stiffness matrix, stiffness matrix It is a generalized coordinate. With temperature T The function, stiffness matrix For the thermal stiffness of the automotive transmission system, Let be the vector of external excitation forces acting on the vehicle's transmission system. The contact force vector. lubricating viscosity With lubricating oil pressure The function of lubrication viscosity With temperature T Related.
[0006] Furthermore, the equations for the heat network model are: ; in, For the thermal fusion matrix of automotive transmission systems, These represent the node temperature vector and node temperature change rate vector between components in an automotive transmission system. For the heat conduction matrix, Let the heat generation rate vector be the heat generation rate vector. With contact force vector and mechanical efficiency Related, mechanical efficiency For temperature T The function, The heat vector carried away by the cooling system of the automotive transmission system.
[0007] Furthermore, the fluid dynamics model is as follows: ; in, x The coordinates represent the direction of lubricant flow in the automotive transmission system, which is consistent with the direction of movement of the contact surfaces of various components. y The coordinates are perpendicular to the direction of lubricating oil flow. To be at temperature T The thickness of lubricating oil on the contact surfaces of each component under certain conditions. To be at temperature TLubricating oil dynamic viscosity under certain conditions p To be at temperature T The hydrodynamic pressure generated by the lubricating oil under certain conditions U This refers to the tangential velocity generated on the contact surfaces of each component.
[0008] Further, step S3 includes: S31: Set the initial and boundary conditions for the automotive powertrain simulation. Initial conditions include temperature. T Lubricating oil temperature, speed and torque, and boundary conditions including the cooling conditions of the lubricating oil cooling system and the test environment temperature; S32: At temperature T Updating the mass matrix of the automotive powertrain under certain conditions Stiffness matrix and lubrication viscosity Solving the multibody dynamics equations considering the flexible body yields updated generalized coordinates. Velocity vector and contact force vector ; S33: The generalized coordinates to be updated Velocity vector and contact force vector Substitute the equations into the fluid dynamics model and the heat network model to calculate the new temperature. ; S34: Calculate the new temperature Temperature relative to initial conditions T The difference, and set a temperature error threshold. ; like If the initial temperature field and dynamic state of the vehicle transmission system converge, then the temperature field and dynamic state of the vehicle transmission system are determined to be converged; otherwise, return to step S3 and adjust the initial temperature conditions. T Replace with temperature Perform steps S3-S6 until the temperature field and dynamic state of the vehicle transmission system converge; S35: Outputs the stress time history of the automotive transmission system at the convergence of temperature field and dynamic state under different operating conditions. .
[0009] Further, step S4 includes: S41: Construct a nonlinear continuous damage mechanics model based on stress time history. Calculate the damage variables under different driving cycles; The nonlinear continuous damage mechanics model is as follows: ; in, D As a damage variable, NThe number of driving cycles, Based on stress time history The dynamic stress amplitude, This represents the fatigue damage limit of various components in an automotive transmission system. Based on stress time history The dynamic average stress, These are the maximum and minimum values of dynamic stress, respectively. It is a degenerate function. The initial damage impedance, The coupling sensitivity coefficient, m These are material constants; S42: Set the critical value for the damage variable And record when the damage variable D Reaching the critical value Total number of driving cycles Based on the total number of loops It reflects the fatigue life of the automotive transmission system.
[0010] The beneficial effects of this invention are as follows: This invention proposes a strongly coupled iterative solution framework of "multibody dynamics-thermodynamics-fluid dynamics," accurately simulating the mutual conversion and influence of mechanical and thermal energy in automotive transmission systems. It establishes a nonlinear cumulative fatigue damage model considering load history and the evolution of material micro-defects, used for high-confidence remaining life prediction. By comprehensively considering the thermo-mechanical-fluid coupling effect and microscopic dynamic excitation, the correlation between simulation results and physical experiments is significantly improved, especially for the highly accurate prediction of abnormal vibrations and thermal failures in automotive transmission systems under high-speed, heavy-load conditions. Attached Figure Description
[0011] Figure 1 This is a flowchart of a simulation test method for automotive transmission systems. Detailed Implementation
[0012] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.
[0013] like Figure 1 As shown, a simulation test method for an automotive transmission system includes the following steps: S1: Based on the dimensional parameters of the automotive transmission system, draw a three-dimensional geometric model of the automotive transmission system, import it into the multibody dynamics simulation software, and assign material properties, constraint pairs and force elements to different components. The contact parts between components are defined as flexible connections to which fine force elements can be applied. The automotive transmission system in this embodiment includes core components such as a gearbox, clutch, drive shaft, and differential. The constraint pairs include rotary pairs, universal joint pairs, etc., and the contact parts between components include key contact parts such as gear pairs and bearings.
[0014] S2: Construct mutually coupled multibody dynamics equations, thermal network model equations, and fluid dynamics models considering flexible bodies; The multibody dynamics equations considering a flexible body are as follows: ; in, The mass matrix of the automotive transmission system. It is the generalized coordinate system of the automobile transmission system. With temperature T The function, the mass matrix Consider the slight changes in mass distribution caused by thermal deformation of the automotive transmission system; These are the velocity vector and acceleration vector of the automotive transmission system, respectively. The damping matrix of the automotive transmission system. Time-varying meshing stiffness and time-varying damping The function, t For time, Here is the stiffness matrix, stiffness matrix It is a generalized coordinate. With temperature T The function, stiffness matrix For the thermal stiffness of the automotive transmission system, Let be the vector of external excitation forces acting on the vehicle's transmission system. The contact force vector. lubricating viscosity With lubricating oil pressure The function of lubrication viscosity With temperature T Related; The equations for the heat network model are: ; in, For the thermal fusion matrix of automotive transmission systems, These represent the node temperature vector and node temperature change rate vector between components in an automotive transmission system. For the heat conduction matrix, Let the heat generation rate vector be the heat generation rate vector. With contact force vector and mechanical efficiency Related, mechanical efficiency For temperature T The function, The heat vector carried away by the cooling system of the automotive transmission system; The fluid dynamics model is as follows: ; in, x The coordinates represent the direction of lubricant flow in the automotive transmission system, which is consistent with the direction of movement of the contact surfaces of various components. y The coordinates are perpendicular to the direction of lubricating oil flow. To be at temperature T The thickness of lubricating oil on the contact surfaces of each component under certain conditions. To be at temperature T Lubricating oil dynamic viscosity under certain conditions p To be at temperature T The hydrodynamic pressure generated by the lubricating oil under certain conditions U The tangential velocity generated at the contact surfaces of each component; The flow direction coordinates of the lubricating oil define the geometric domain of the lubrication region and the time evolution of the dynamic process; by solving the fluid dynamics model, the entire ( x , y On the planar domain, over time t Varying lubricating oil pressure. The contact surfaces of various components are supported by lubricating oil pressure, preventing direct metal-to-metal contact (i.e., achieving hydrodynamic lubrication). The integral of the pressure distribution determines the load-bearing capacity of the lubricating oil film between contacts. The distribution of lubricating oil pressure can be used to calculate load-bearing capacity and balance with external mechanical loads. The distribution of lubricating oil pressure directly affects the friction loss and power consumption of the friction pair. The high-pressure areas of the lubricating oil pressure distribution are key locations for assessing contact fatigue (such as pitting).
[0015] Lubricating oil dynamic viscosity Viscosity is a measure of the internal friction of lubricating oil, indicating its ability to resist flow. Viscosity directly affects the formation and load-bearing capacity of the lubricating oil film; dynamic viscosity of lubricating oil. By temperature T Strongly coupled with the thermal network model equations, frictional heat generation can raise the temperature of the lubricating oil, causing a sharp decrease in the dynamic viscosity of the lubricating oil, which in turn weakens the load-bearing capacity of the lubricating oil and may lead to lubrication failure.
[0016] S3: Set the initial and boundary conditions for the simulation of the automotive transmission system, under temperature... TSolve the multibody dynamics equations, fluid dynamics model equations, and thermal network model equations considering flexible bodies under different operating conditions, and output the stress time history of the automotive transmission system at the convergence of the temperature field and dynamic state under different operating conditions. .
[0017] Step S3 specifically includes: S31: Set the initial and boundary conditions for the automotive powertrain simulation. Initial conditions include temperature. T Lubricating oil temperature, speed and torque, and boundary conditions including the cooling conditions of the lubricating oil cooling system and the test environment temperature; S32: At temperature T Updating the mass matrix of the automotive powertrain under certain conditions Stiffness matrix and lubrication viscosity Solving the multibody dynamics equations considering the flexible body yields updated generalized coordinates. Velocity vector and contact force vector ; S33: The generalized coordinates to be updated Velocity vector and contact force vector Substitute the equations into the fluid dynamics model and the heat network model to calculate the new temperature. ; S34: Calculate the new temperature Temperature relative to initial conditions T The difference, and set a temperature error threshold. ; like If the initial temperature field and dynamic state of the vehicle transmission system converge, then the temperature field and dynamic state of the vehicle transmission system are determined to be converged; otherwise, return to step S3 and adjust the initial temperature conditions. T Replace with temperature Perform steps S3-S6 until the temperature field and dynamic state of the vehicle transmission system converge; S35: Outputs the stress time history of the automotive transmission system at the convergence of temperature field and dynamic state under different operating conditions (such as WLTC cycle and hill climbing conditions). .
[0018] S4: Construct a nonlinear continuous damage mechanics model based on the stress time history. Damage variables are calculated under different driving cycles to assess the fatigue life of the automotive transmission system.
[0019] Step S4 specifically includes: S41: Construct a nonlinear continuous damage mechanics model based on stress time history. Calculate the damage variables under different driving cycles; The nonlinear continuous damage mechanics model is as follows: ; in, D As a damage variable, N The number of driving cycles, Based on stress time history The dynamic stress amplitude, This represents the fatigue damage limit of various components in an automotive transmission system. Based on stress time history The dynamic average stress, These are the maximum and minimum values of dynamic stress, respectively. It is a degenerate function. The initial damage impedance, The coupling sensitivity coefficient, m These are material constants, typically m >1 (For metallic materials, it is usually between 3 and 10). The nonlinear continuous damage mechanics model constructed in this invention is applied to the fatigue life prediction of automotive transmission systems. It describes the differential form of the evolution of damage to the materials of each component of the automotive transmission system under cyclic loading with the number of cycles, and is used to calculate the damage accumulation of each component of the automotive transmission system under different driving cycles.
[0020] When damage variables D When the value is less than 0, the materials of each component are in an intact initial state; At that time, there is a state of damage accumulation in which microcracks initiate and propagate within the material; when At this time, macroscopic failures occur in the materials of each component (such as visible cracks or loss of function). Damage variables D It is an internal variable that macroscopically represents the reduction in the effective load-bearing area of each component material, and microscopically represents the evolution of the density and size of defects such as dislocation density, microvoids, and microcracks.
[0021] Dynamic stress amplitude The stress fluctuation component, which varies with time, is the main driving force behind fatigue damage; dynamic mean stress. Represents the reference level of stress cycles, reflecting static or quasi-static load components; degradation function The coupled degradation effect of mean stress and damage state on the material's damage resistance was quantified, and the initial damage impedance was determined. For materials in a non-destructive state ( D The inherent fatigue resistance coefficient at a value of 0 is usually... Coupling sensitivity coefficient It characterizes the intensity of the interaction between damage and mean stress.
[0022] S42: Set the critical value for the damage variable (Typically set to 0.7-0.9), and record the damage variable. D Reaching the critical value Total number of driving cycles Based on the total number of loops Reflects the fatigue life of an automotive transmission system. Total number of cycles. The larger the value, the greater the fatigue life of the automotive transmission system; conversely, the smaller the value, the smaller the fatigue life.
[0023] This invention proposes a strongly coupled iterative solution framework of "multibody dynamics-thermodynamics-fluid dynamics" to accurately simulate the mutual conversion and influence of mechanical and thermal energy in automotive transmission systems. A nonlinear cumulative fatigue damage model considering load history and the evolution of material micro-defects is established for high-confidence remaining life prediction. By comprehensively considering the thermo-mechanical-fluid coupling effect and microscopic dynamic excitation, the correlation between simulation results and physical experiments is significantly improved, especially for the highly accurate prediction of abnormal vibrations and thermal failures in automotive transmission systems under high-speed, heavy-load conditions.
Claims
1. A simulation test method for an automotive transmission system, characterized in that, Includes the following steps: S1: Based on the dimensional parameters of the automotive transmission system, draw a three-dimensional geometric model of the automotive transmission system and import it into multibody dynamics simulation software, assigning material properties, constraint pairs and force elements to different components; S2: Construct mutually coupled multibody dynamics equations, thermal network model equations, and fluid dynamics models considering flexible bodies; S3: Set the initial and boundary conditions for the simulation of the automotive transmission system, under temperature... T Solve the multibody dynamics equations, fluid dynamics model equations, and thermal network model equations considering flexible bodies under different operating conditions, and output the stress time history of the automotive transmission system at the convergence of the temperature field and dynamic state under different operating conditions. ; S4: Construct a nonlinear continuous damage mechanics model based on the stress time history. Damage variables are calculated under different driving cycles to assess the fatigue life of the automotive transmission system.
2. The simulation test method for an automotive transmission system according to claim 1, characterized in that, The multibody dynamics equations considering flexible bodies are as follows: ； in, The mass matrix of the automotive transmission system. It is the generalized coordinate system of the automobile transmission system. With temperature T The function, the mass matrix Consider the slight changes in mass distribution caused by thermal deformation of the automotive transmission system; These are the velocity vector and acceleration vector of the automotive transmission system, respectively. The damping matrix of the automotive transmission system. Time-varying meshing stiffness and time-varying damping The function, t For time, Here is the stiffness matrix, stiffness matrix It is a generalized coordinate. With temperature T The function, stiffness matrix For the thermal stiffness of the automotive transmission system, Let be the vector of external excitation forces acting on the vehicle's transmission system. The contact force vector. lubricating viscosity With lubricating oil pressure The function of lubrication viscosity With temperature T Related.
3. The simulation test method for an automotive transmission system according to claim 2, characterized in that, The equations for the heat network model are: ； in, For the thermal fusion matrix of automotive transmission systems, These represent the node temperature vector and node temperature change rate vector between components in an automotive transmission system. For the heat conduction matrix, Let the heat generation rate vector be the heat generation rate vector. With contact force vector and mechanical efficiency Related, mechanical efficiency For temperature T The function, The heat vector carried away by the cooling system of the automotive transmission system.
4. The simulation test method for an automotive transmission system according to claim 3, characterized in that, The fluid dynamics model is as follows: ； in, x The coordinates represent the direction of lubricant flow in the automotive transmission system, which is consistent with the direction of movement of the contact surfaces of various components. y The coordinates are perpendicular to the direction of lubricating oil flow. For temperature T The thickness of lubricating oil on the contact surfaces of each component under certain conditions. To be at temperature T Lubricating oil dynamic viscosity under certain conditions p To be at temperature T The hydrodynamic pressure generated by the lubricating oil under certain conditions U This refers to the tangential velocity generated on the contact surfaces of each component.
5. The simulation test method for an automotive transmission system according to claim 4, characterized in that, Step S3 includes: S31: Set the initial and boundary conditions for the automotive powertrain simulation. Initial conditions include temperature. T Lubricating oil temperature, speed and torque, and boundary conditions including the cooling conditions of the lubricating oil cooling system and the test environment temperature; S32: At temperature T Updating the mass matrix of the automotive powertrain under certain conditions Stiffness matrix and lubrication viscosity Solving the multibody dynamics equations considering the flexible body yields updated generalized coordinates. Velocity vector and contact force vector ; S33: The generalized coordinates to be updated Velocity vector and contact force vector Substitute the equations into the fluid dynamics model and the heat network model to calculate the new temperature. ; S34: Calculate the new temperature Temperature relative to initial conditions T The difference, and set a temperature error threshold. ; like If the initial temperature field and dynamic state of the vehicle transmission system converge, then the temperature field and dynamic state of the vehicle transmission system are determined to be converged; otherwise, return to step S3 and adjust the initial temperature conditions. T Replace with temperature Perform steps S3-S6 until the temperature field and dynamic state of the vehicle transmission system converge; S35: Outputs the stress time history of the automotive transmission system at the convergence of temperature field and dynamic state under different operating conditions. .
6. The simulation test method for an automotive transmission system according to claim 5, characterized in that, Step S4 includes: S41: Construct a nonlinear continuous damage mechanics model based on stress time history. Calculate the damage variables under different driving cycles; The nonlinear continuous damage mechanics model is as follows: ； in, D As a damage variable, N The number of driving cycles, Based on stress time history The dynamic stress amplitude, This represents the fatigue damage limit of various components in an automotive transmission system. Based on stress time history The dynamic average stress, These are the maximum and minimum values of dynamic stress, respectively. It is a degenerate function. The initial damage impedance, The coupling sensitivity coefficient, m These are material constants; S42: Set the critical value for the damage variable And record when the damage variable D Reaching the critical value Total number of driving cycles Based on the total number of loops It reflects the fatigue life of the automotive transmission system.