| Shortening the constructing cycle and improving accuracy are the requirements of finite element analysis model for complicated bus frame,as for the problems of low efficiency of construction of welding joints in finite element analysis and the simulation of air-spring suspension boundary conditions,rapid construction of welding joints,using equivalent loads to simulate air-spring suspension boundary conditions are studied;put forward the method of rapid construction of welding joints based on point cloud registration.On the basis,sizes of the bus frame are optimized in order to achieve the purpose of lightweight.The first chapter summarizes the domestic and foreign research status of structure performance analysis and lightweight design of the complicated bus frame,including the fast construction of welding joints in bus frame,the setting of boundary conditions based on air-spring suspension bearing characteristics and lightweight design of complicated bus frame;the shortcomings are discussed and the research content and structure of the thesis introduced.The second chapter proposes the method of constructing welding joints quickly based on joints sets,and establishes the corresponding joint set of the same welded joints of large quantity for each sub assembly.A method to quickly construct welding relationships based on point cloud registration and corresponding nodes substitution is proposed,achieving the realization of the fast construction of the welding relationship and solving the low efficiency in construction and differences between joints.The third chapter studies the setting of air-spring suspension boundary conditions based on equivalent load method.We need to set boundary conditions after constructing the welding relationship,construct the multi-body dynamic models of air-spring suspension system,and calculate the forces on the surfaces of bus frame connecting with air-spring suspension under multiple working conditions.Add the forces on the finite element analysis model as equivalent loads,reducing the stress concentration of the connection position of air-spring suspension and the bus frame,ensuring the accuracy of bus frame stress distribution.The fourth chapter analyzes the stress distribution of bus frame under multiple working conditions and compares the maximum stress under various conditions,determines the dangerous working condition combined with opening deformation.We calculate the first to sixth free modals of the bus frame,analyze the frequencies and mode shapes,and the vibrations are analyzed combined with the excitation of engine and roads in the driving process.The fifth chapter studies the lightweight design of the bus frame.Based on the structural performance analysis in the previous chapters,select the profiles with large safety margin as optimal objects,set corresponding constraints of the section sizes based on symmetry in order to reduce calculation amount,construct agent model and use genetic algorithm to solve it.Finally,the optimization scheme is compared with the former in order to verify its feasibility.The sixth chapter summarizes the achievements of this thesis and discusses the future studies. |
