I. Introduction CAE is widely used in the development of mechanical products such as automobiles. For example, the Finite Element Method (FEM) is used to calculate the stress and deformation of mechanical parts for strength and stiffness analysis; multibody dynamics methods are used for dynamic simulation analysis of the handling stability and ride comfort of the entire vehicle; the Finite Element Method is used for vehicle collision analysis; and the Finite Element Method and Boundary Element Method (BEM) are used to analyze vehicle noise, etc. It can be said that the role of CAE in the automotive product development process is irreplaceable. The role of CAE in automotive product development is mainly reflected in three aspects: 1. CAE greatly shortens the product development cycle. Solid modeling and parametric methods are used in the modeling and analysis process, making model and parameter modifications very convenient, and significantly reducing the time required to determine reasonable structural parameters. 2. It reduces development costs. Compared with road testing and indoor bench testing, the cost of using CAE to analyze various performance characteristics of the entire vehicle and its components is significantly reduced. 3. It facilitates the development of vehicles and components with superior performance through optimization and other means. For example, optimizing the structural parameters of the chassis and body can reduce the overall vehicle weight; optimizing the parameters of the running gear and steering system can improve the handling stability and ride comfort of the vehicle. Of course, from a practical application perspective, the effective use of automotive CAE depends on two important prerequisites. One is a thorough mastery of CAE technology, and the other is the provision of basic experimental data and relevant databases. Basic experimental data refers to data such as tire characteristics, road characteristics, and the mechanical properties of various materials. Relevant databases refer to databases accumulated by enterprises during product design and development that provide structural forms and key parameters (including price, outsourcing information, etc.). Furthermore, to better implement CAE and maximize its effectiveness, it must be integrated with CAD/CAPP/CAM, optimization techniques, and other technologies. This article mainly introduces the application and specific implementation of CAE in automotive product development and discusses the relationship between CAE and CAD, CAPP, CAM, and optimization techniques. II. Application of CAE in Automotive Product Development CAE has a very wide range of applications in automotive product development. Here, we introduce several key applications. 1. The finite element method is widely used in the analysis of structural strength and stiffness of mechanical structures due to its high calculation accuracy, especially in the linear range of material stress and strain. In addition, when considering the coupling of mechanical stress and thermal stress, large software such as ANSYS and NASTRAN provide very convenient analysis methods. (1) Strength and stiffness analysis of frame and body The frame and body are the most complex components in automobiles in terms of structure and stress, especially for fully load-bearing bus bodies. The purpose of finite element analysis of frame and body is to improve its load-bearing capacity and deformation resistance, reduce its own weight and save materials. In addition, for the whole automobile, when the weight of the frame and body is reduced, the weight of the whole vehicle is also reduced, thereby improving the power and economy of the whole vehicle. (2) Bending stress and contact stress analysis of gears Gears are transmission parts commonly used in automobile engines and transmission systems. By analyzing the bending stress at the tooth root and the contact stress on the tooth surface, the gear structural parameters are optimized to improve the load-bearing capacity and service life of the gears. (3) Stress analysis of engine parts Taking the cylinder head of the engine as an example, during its operation, it is not only subjected to the high-pressure gas in the cylinder, but also generates complex thermal stress. Cylinder head cracking incidents occur frequently. If only the method of local reinforcement at the crack is used to improve it, it cannot fundamentally solve the problem. The finite element method provides a fundamental way to solve this problem. 2. Application in automotive passive safety Safety, environmental protection and energy conservation are the three major hot issues facing automobiles. How to improve the collision resistance of the vehicle body is one of the problems that need to be solved in automotive passive safety. Using the finite element method to simulate the collision process of automobiles involves nonlinear problems such as large deformation, which is different from general finite element analysis. Since simulation calculation can save expensive real vehicle collision test costs, and simulation analysis is the only analysis method in the design stage, domestic and foreign automobile companies generally adopt this method. The LSDYNA module in ANSYS software is often used for simulation analysis of the collision process of automobiles. 3. Automotive dynamics simulation analysis employs multibody (rigid and flexible body) dynamics analysis methods to predict the dynamic performance of the entire vehicle during the research phase. These performance parameters can then be optimized to improve product performance, shorten development time, and reduce development costs. Taking vehicle handling stability as an example, since influencing factors involve multiple aspects such as tires, suspension, and steering, simple calculations are insufficient to obtain reasonable conclusions, and even qualitative conclusions are often unreliable. Therefore, various mechanical dynamics simulation software programs have been developed. It is worth mentioning the ADAMS software from MDI Corporation in the United States, which is widely used for dynamic simulation of vehicle handling stability and ride comfort. The TIRE module in ADAMS provides several tire models for selection during analysis to accurately establish tire dynamic models. The CAR module in ADAMS is specifically designed for automotive dynamics simulation and is very easy to use. Several domestic automotive companies have already used this software for dynamics simulation analysis of trucks, cars, truck trains, and buses, achieving good results. III. Specific Implementation and Software Introduction of CAE CAE, as an analysis tool, can be implemented independently or used in conjunction with other CAX tools. For example, finite element analysis software generally provides corresponding pre- and post-processing modules, which can be used independently or integrated with CAD software. Below is a brief introduction to the implementation process and software for finite element analysis and mechanical dynamics simulation. 1. Finite Element Analysis Process and Software for Automotive Parts Dozens of commercial finite element analysis software can be listed. Here, we only introduce IDEAS, ANSYS, and NASTRAN, which are most widely used in the structural analysis of automotive parts. SDRC's IDEAS software is an integrated software that includes CAD, CAE, CAPP/CAM, PDM, etc. Solid modeling, mesh generation, application of loads and constraints, solving, and post-processing can all be completed by different modules of this software. ANSYS software from ANSYS Corporation is a dedicated finite element analysis software; pre- and post-processing and solving can also be completed by this software. MSC's NASTRAN finite element software has a dedicated pre- and post-processing software, PATRAN. Its analysis process is similar to IDEAS and ANSYS. Figure 1 shows a cross-axis model modeled and meshed using Pro/E. The above illustrates that the finite element software from each company can independently complete finite element analysis tasks. Of course, the above-mentioned software also provides interfaces with various CAD software. Generally speaking, the modeling function of finite element software is not as powerful as that of dedicated CAD software. Only by combining them can their respective functions be better utilized. When analyzing the bending strength of the cross shaft of the automobile transmission device, the author took the following approach: first, the geometric model of the cross shaft was established by Pro/E and the mesh was completed, and the model was output in ANSYS file format .ans. Then, ANSYS read the model and completed the subsequent analysis. Figure 1 shows the cross shaft model modeled and meshed by Pro/E. Of course, ANSYS can also directly read the .prt file of Pro/E. The meshing and subsequent tasks of finite element analysis are all completed by ANSYS. Almost all CAD software can output geometric model files in IGES format, but this format only contains information about lines and surfaces, but not about volumes. Moreover, some information is lost or even incorrect geometric information is generated in the IGES format file. The following is a method to solve this problem: (1) Use UGS's CAD/CAM software UG to read the IGES format file to be converted. (2) Modify the model in UG and use the Sewing command to stitch all the faces of the part together to generate a solid model. (3) Save the solid model as a UG format .prt file. (4) Use the NASTRAN preprocessing software PATRAN to read the .prt file generated by UG to obtain the solid model required for finite element analysis. (5) PATRAN and NASTRAN complete the other tasks of finite element analysis. 2. Application of mechanical dynamics simulation software in automobiles Similar to finite element analysis software, mechanical dynamics simulation analysis software can be used alone or integrated with other CAX software. The software most commonly used in automobile dynamics simulation is ADAMS and DADDS. Taking ADAMS as an example, the steps of mechanical dynamics simulation analysis are introduced. When using ADAMS software alone for analysis, the multibody model to be analyzed can be built using its AVIEW module, and then solved using its SOLVER module. However, in order to make the simulation analysis more successful, multiple software programs are often used in collaboration. Here are some benefits of integrating mechanical dynamics simulation software with CAD and FEM: (1) Modeling with CAD software is more convenient and accurate, the generated graphics are more realistic, and the dynamic simulation effect is better. (2) Accurate mass parameters, such as the mass, center of mass, and moment of inertia of the part, can be more easily obtained from the accurate CAD model. (3) The function of mechanical dynamics simulation software in building soft body models is very limited, while the MNF (modal neutral file) generated by the finite element analysis software can be input into the accurate soft body model generated by the mechanical dynamics simulation software. (4) Although mechanical dynamics software can determine the mutual dynamic relationship and force between parts, it cannot analyze the stress of parts and can only be done with the help of finite element analysis software. IV. Integration of CAE with other CAX Figure 2 Flowchart of CAE and CAD integration From the above analysis, we know that in order to better complete CAE tasks, integrating CAE software with other CAX will achieve better results. As an example, Figure 2 is a flowchart of implementing this integration. In this example, the CAD software first generates the geometric model, outputs the model in .IGES format or other formats, and then the finite element software and mechanical dynamics software read the geometric model in respectively. Finite element method (FEM) software performs stress, strain, and modal analysis based on the geometric model generated by CAD software and the nodal forces calculated by mechanical dynamics software, and outputs the analysis results. The models required by mechanical dynamics software are of two types: rigid body models obtained from CAD software; and flexible body models obtained from the FEM software (.MNF format files). Additionally, if the models of certain parts are generated by the mechanical dynamics software itself, mass parameters can be obtained from the CAD software as needed. Besides outputting the final results, mechanical dynamics simulation analysis can also output the motion relationships and nodal forces of parts for use in FEM analysis. Another example is an automotive transmission CAD/CAM system. This system consists of CAD geometric modeling, parametric optimization design, finite element analysis, and CAPP/CAM. The CAD software used is Pro/E, which completes the geometric modeling and generates model feature files. The parametric optimization design module reads the model feature files and optimizes the structural and performance parameters of the transmission. During optimization, the finite element software ANSYS is called to calculate the strength and stiffness of the parts. The optimized model is returned to Pro/E, which then completes the CAPP/CAM task.