Integrated Design Technique For Material And Structures Of Vehicle Body Under Crash Safety Considerations

As the energy crisis and environmental pollution have become increasingly sharp,new lightweight materials and structures are attracting more and more attentions in the automotive and other industries,due to their great capability in energy saving and emission reduction.In the automotive design,the material and structure are extremely decisive so that it is particularly important to study the integrated design method of materials and structures.At the same time,the multi material structure of vechile body has been rapid development,because it can not only meet the requirement of light weight,but also,to large extent,in providing a broader design space to meet the requirements of crash safety,etc.Although the development of multi material structure of vehicle body is a popular trend,the research on integrated design of material and structure is less.In this paper,an integrated design method of vehicle body material and structure considering crash safety is proposed.The results suggest that,it can handle,analyze and design the multi material and multi structure of vechile body.First,in view of basic requirements of crashworthiness and light weight,the design indexes?design objectives?and the analytical structures?analytical factors?were chosen and determined.Second,considering the dominant and discrete characteristics of the material,the orthogonal design was carried out to obtain the response of the material against crash safety and lightweight.On the basis of the characteristics of orthogonal experimental design,the multi-index comprehensive balance analysis was used to analyze and match the analytical factors,so as to obtain the general material selection scheme.At the same time,in order to acquire the significance of the analytical factors,Max Ur^?3?factorial design method was developed,combined with the range analysis,for obtaining the significant factors.Third,the material type and structure thickness of the significant factors were set as discrete and continuous design variables,respectively,and multi-objective optimization problem was proposed.Meanwhile,in an attempt to obtain the optimal surrogate model with high precision for the multi-objective optimization mathematical function,an optimal radial basis function?RBF?model was put forward based on the optimization of the smoothing coefficients.Finally,the non-dominated sorting genetic algorithm II?NSGA-II?and the minimum distance selection method were used to obtain the Pareto solution set and the comprehensive optimal solution,respectively,under the multi-objective design requirements.The reliability and effectiveness of the proposed method were verified by the results from analysis and design of two important working scenarios:vehicle roof crushing and vehicle offset frontal impact.After the integrated design of materials and structures of vehicle body under crash safety considerations,under roof crushing,there were significant increment of the total absorbed energy and the maximum resistive force in comparison to their initial values,and the weight was reduced apparently as well;As for the vehicle under offset frontal impact,the maximum accelaration and the weight were decreased remarkably against their initial values,meanwhile the total absorbed energy was increased.Therefore,the results suggested that the proposed method is able to effectively analyze,optimize and design the materials and structures of the vehicle body to improve the crash safety and light weight,and also provides a new design idea for the integrated design of the material s and structures in engineering.