Topology Optimization Of Crashworthiness And Software Development Based On Equivalent Static Load Method

In recent years,with the increasing voice of energy saving and environmental protection,the major automobile manufacturers have increased the R&D investment of electric vehicles and attempts to achieve a strategic transformation from traditional fuel vehicles to electric vehicles in this critical period.However,currently,body structures of electric vehicles on the market are slightly modified on the basis of the body of the fuel vehicles instead of combining with the actual bearing way of the vehicle body.Obviously,there exists big difference between the motor and the engine,not only the weight but also the layout in the vehicle,which determines the necessity of the redesign of the body structure.As one of the three most important stages in the body design process,conceptual design was able to achieve the light-weight design maximally.Meanwhile,it can bring much greater economic benefits than detailed design and basic design.Therefore,in the conceptual design stage of the vehicle body,it can greatly reduce the weight of the vehicle body under the premise of ensuring the vehicle performance if the difference between electric vehicles and traditional vehicles was been considered.Currently,more attention is only paid to the static bending stiffness,torsion stiffness and natural frequency of the vehicle body in the optimization process under multiple loading conditions.As an indispensable vehicle safety performance,crashworthiness remains to be further studied.Obviously,the crashworthiness of the vehicle body is a time-dependent dynamic nonlinear problem.Therefore,it will bring a huge amount of computation if we perform the sensitivity analysis directly according to existing optimization algorithms.Though the agent model optimization method is simple and universal,the accuracy cannot be guaranteed because the method depends on the number of samples largely.Hybrid Cellular Automata(HCA)optimization methods are only suitable for small structures due to their poor accuracy and robustness.For large structures,problems such as low computational efficiency and non-periodic oscillation behavior of the objective function occur.The Equivalent Static Load Method(ESLM)shows high accuracy and fast convergence speed in solving dynamic nonlinear optimization problems and the entire optimization process consists of dynamic nonlinear analysis and static optimization.The equivalent static load(ESLs)at each node can be calculated by multiplying the displacement response outputted by the analysis process with the stiffness matrix of the model.And then,perform the static optimization process by applying the ESLs in the model.Finally,update the optimization model according to the optimization result.The whole dynamic optimization process iterates between the analysis process and optimization process until the convergence parameter was satisfied.In order to solve the problem of dynamic topology optimization,a software CrashTopologyOptimization(CrashTopt)which can solve the dynamic topology optimization problem was developed in this paper by using VB.NET language based on the equivalent static load method.The process of software development consists of two aspects: on one hand,design the process of software development,the overall architecture of software and the operation interface of software;on the other hand,implement the functions of the software by programming including the import of the file,the transformation of file storage format,the modification of model,the extraction of stiffness matrix,the writing of optimization parameters,the calculation of equivalent static load,the update of the model during iteration and the judgment of convergence.Finally,the entire software development process is completed.A certain SUV Body-in-White(BIW)was regarded as the research object,this paper comprehensively considered the strain energy under the conditions of frontal collision,side collision,rear-end collision,top pressure and then established the topological optimization model of the BIW.The constraint of the optimization model was set to volume fraction and the objective function was to minimize the weighted strain energy(maximize the weighted stiffness)under the above conditions.Next,the self-developed CrashTopt software was used to perform the topology optimization of crashworthiness of the BIW.Good optimization results indicate that CrashTopt software can perform an optimization design for a vehicle body under a variety of working conditions which can be effectively applied in engineering problems.