Structural Crashworthiness Optimization And Software Development Considering Displacement And Contact Force Responses

Crash safety is an important issue of vehicle performance.The crashworthiness of vehicle is of great significance for occupant safety.Displacement and contact force response are two important issues of crashworthiness design.However,the crash problem contains geometric,material and contact nonlinear characteristics and it is a dynamic time domain problem.Therefore,the calculation of structural sensitivity information is too difficult to apply the traditional gradient based structural optimization method.In recent years,the equivalent static load method has been proved to be an effective method for solving crash optimization problems.This method transforms the dynamic nonlinear crash condition into multiple linear static load cases.Then the structural optimization under static load cases can be solved by using mature optimization technology.However,this method can only consider the displacement response and cannot consider the contact force response.Therefore,its dual method,the equivalent static displacement method,is proposed in this paper to solve the contact force optimization problem.Using the equivalent static load method and equivalent static displacement method,this paper integrates the commercial software LS-DYNA and Opti Struct to develop an industrial software CrashOpt,which is used to solve the structural crash optimization problem considering the displacement and contact force responses.The main contents of this paper are as follows.First,the literatures on crashworthiness optimization are reviewed.And the advantages and disadvantages of existing methods in solving crashworthiness optimization problems are discussed.Among them,the equivalent static load method can effectively solve the crashworthiness optimization problem considering the displacement response.However,there is no effective method to solve the contact force optimization problem.Then,the concept of equivalent static load method is summarized.In order to improve the efficiency and convergence of the algorithm,this paper also introduces the key time points of energy absorption,the scaling factor method and moving limit strategy.In Chapter 3,the equivalent static displacement method,which can solve the contact force optimization problem,is proposed.The definition,calculation process,equivalence proof of contact force and sensitivity analysis of constraint reaction force are described in detail.The process for contact force optimization based on equivalent static displacement is given.And the similarities and differences between this method and equivalent static load method are compared.In Chapter 4,the CrashOpt software is developed using the VB.net language.The software function,architecture,file storage,software internal execution process are described in detail.Finally,five examples are given to verify the accuracy and efficiency of CrashOpt software for solving the crashworthiness optimization problem.Meanwhile,the effectiveness of the proposed method is also verified.