Design Methods Of TWB High-strength Steel Vehicle Body Parts Based On Side Impact Safety

The traditional designs of TWB parts mainly depend on experience available by incorporating with a trial and error procedure to improve the product design quality. The method is often time-consuming and high-cost, but also often makes it difficult to ensure the practicality and reliability of the TWB parts, especially for the design of TWB parts based on side impact safety. As the development and maturity of finite element method, CAE technology has been widely applied in automotive parts design. Although the finite element analysis methods promote the progress of vehicle body parts, avoid the blindness, reduce the design cost and shorten the development cycle of the body structure to considerable extent, the finite element method itself is only an analytical tool to evaluate and verify the product design. What’s more, design is still inseparable from the "trial and error". In order to maximize the potential of CAE technology, CAE and optimization algorithm are combined to improve the design efficiency and effectiveness of the TWB parts of vehicle body. This paper mainly focus on method for determining the weld line of TWB parts, the determination of the key components in the side impact, Approximate model, topology optimization method and multi-objective optimization study.The main contents are as follows:(1) The paper establishes a detailed vehicle side impact model and verifies its correctness, and then takes out side impact simulation analysis by changing the material properties of the major vehicle components. What’s more, the paper makes detailed comparisons on the invasive speed and invasive measurement of the vehicle body to study the contribution of the various parts on the vehicle side impact performance. The study shows that the material distribution of the doors and the B-pillars has a significant impact on the vehicle side impact performance.(2) The paper carries out tensile test of tailor welded blanks to research the impact of the weld of the material properties of welded blanks.And it gets the conclusion that total node weld model has high accuracy for the stiffness analysis, through the comparative analysis of test results and simulation results. The paper also makes use of the improved version of the bi-directional evolutionary structural optimization method to develop a welds determining system which is suitable for multi-stiffness and multi-material TWB parts design by the advantage of the topology optimization techniques. And then the paper integrates the welds determining system, sensitivity analysis method and size optimization method to propose a new design method of TWB parts. The result shows that the weight of the door system is reduced greatly under the premise of ensuring all kinds of performance requirements for door stiffness and modal by using the new design method.(3) The paper carries out TWB vehicle body parts optimization design based on vehicle side impact approximate model which includes the following contents:it puts forward the reasonable welding plate structure design, and constructs the approximate mathematical model of the response surface and verifies its accuracy at the same time. And then it builds the multi-objective optimization model based on the side impact safety and takes out optimized work of vehicle body parts in two dimensions which are the material thickness and yield strength of the material. At last, the paper uses multi-objective genetic algorithm and multi objective particle swarm algorithm to optimize the design of approximate model. The results show that in the inner door panel and the B-pillar using tailor-welded blank structure which has reasonable distribution of body stiffness can obviously improve the body deformation condition. What’s more, the application of high strength steel in TWB parts is a good solution to the contradiction between the lightweight vehicles and crash safety.