Research On Stiffness Analysis Method Of Integrated Coach Body Structure

The body frame of coach is a complicated spatial higher statically indeterminate structure composed of thin-walled bar and meets the general layout of the structure. The frame should be able to stand the maximum allowable static load and a variety of dynamic load to meet the needs of the fatigue life. It must also have enough sufficient stiffness to ensure assembly and using requirements and should have reasonable dynamic character in order to achieve the purpose of vibration and noise. From this perspective, the analysis of body structure is very necessary.The body stiffness is an important index to evaluate the performance of coach body and has a significant impact for body strength, fatigue durability and NVH performance. In the early design of coach, using finite element method for stiffness analysis of structure can significantly reduce the sample number of vehicles and the development process; improve efficiency and success rate of the design.Currently in the process of structure stiffness analysis, there are some errors such as inaccurate add-section selected, statistical difficulties for body deformation and the reverse angle of the body. According to coach carries the characteristics of body structure, This paper propose the corresponding solutions, and design procedures for the preparation of the corresponding calculations to solve these problems, improve the calculation process and enable them to introduce products to the design of bus early. In addition, on the base of the existing structural models, this paper breaks the routine and carries the integrated coach body structure to carry out a number of explorations and provide a reference for the bus designer.The main contents of this paper are as follows:In the first chapter,developments of coach body structure design in our country and character of integrated coach body structure, and the importance of research more were expatiated. The paper introduces the finite element method, CAE, C# language and other major research methods.In the second chapter,on the basis of the theory of mechanics of materials, the exact definition of flexural stiffness was elaborated and the two kinds of bending stiffness formula were defined, which are the deflection value of the deformation body and the corner of bound section to determine the flexural stiffness. Secondly, a simply supported beam model and space frame model were established in order to verify the applicability of formula of two types of bending stiffness. According to the results,the first formula can calculate the bending stiffness of two structures and the second formula only calculate the simply supported beam model. According to the calculation formula of the space frame structure, this paper calculates the overall bending stiffness of the integrated coach, low floor city buses and hinged buses in order to verify the validity and feasibility of this formula. In order to facilitate data processing, this paper uses C# program to statistics deflection bending deformation and calculate the bending stiffness and it can reduce the difficulty of computing and improve efficiency. Finally, the paper summaries the different types of conditions in the bending of the bound method and determines a more practical processes of the calculation of bending stiffness and makes it suitable for early design analysis and optimization of structural design.Chapter three elaborates the exact definition of torsional stiffness and defines torsional stiffness formula. According to calculation of torsional stiffness problems and the character of coach body structure, the method that confirming the whole body torsion angle using the rigid section was proposed in order to raise the calculation accuracy of torsional stiffness. At the same time, C# was used to calculate twist angle of vehicle and the torsional stiffness. Finally, the process of calculating the torsional stiffness was summed up.The group put forward the structure of the new airbus spinal-keel bus based on the original model of a company integrated coach. Chapter IV focuses on the overall stiffness analysis of these two models and intercepts the local structure in the central keel structure and establishes the finite element analysis model. The paper calculates and compares between the bending stiffness and torsional stiffness. Compared with the 6127 structure, spinal-keel structure increases the overall stiffness levels. The most obvious one is the flexural stiffness and more than doubled. In addition, according to the characteristics of bus structure, the paper made a structural optimization and triangle is used to draw support load to improve the overall stiffness of the structure. The paper Provide strong evidence that the spinal carling structure is a high-rigidity.Chapter V summarized the full text. The paper proposes the calculation of body structure stiffness and solves some errors such as add-section selected inaccurate, statistical difficulties for body deformation and the reverse angle of the body. The paper realized rapid calculation of the bus stiffness. This paper uses C# program to statistics deflection bending deformation and calculate the bending stiffness and it can reduce the difficulty of computing and ensure the accuracy. By the level of experience and limited knowledge, there is a lot of work to do to improve the stiffness analysis of coach body structure in the future.