Research On Computer Simulation Of Internal High Pressure Forming Of Tubes And Its Optimization Of Process Parameters

In the fields of automobile industry and so on, weight reduction of structures is the goal that people have pursued for a long time in order to reduce the energy consumption. It is a trend in the development of advanced manufacturing technology, too. Internal high pressure forming is an advanced technology characterized by lightweight and integrity, which can be used to manufacture hollow structural components and "Van-Form" parts. At present, people pay more attention to internal high pressure forming. The process of tube hydroforming is related to many factors, among which the matching relation between internal pressure and axial feeding is particularly important. It is an important subject for us to find out the rules that how they influence the forming, and then to optimize the matching relation between internal pressure and axial feeding.In this paper, a stainless steel tube bugled a rhombus by internal high pressure forming was used as investigated target. According to different features of deformation, the tube has been divided into three different deformation areas and the stress-strain distribution has been analyzed at different hydroforming stages and different areas. The explicit finite element software DYNAFORM was used to simulate and analyze the process of internal high pressure forming. Then, the rules of internal pressure and axial feeding influencing on the forming were determined. After tube hydroforming, the thickness of tube became thin gradually from both ends to the middle and different thickness bands appeared. The maximum thickness appeared in both ends of the tube. The minimum thickness appeared in the bulging highest position. Themaximum thickness was mainly determined by axial feeding. The minimum thickness was mainly determined by the maximal internal pressure. And the supplementing material function of axial feeding mainly happened at stage of low pressure forming. At the same time, the influences of strain hardening exponent (n-value) and thickness on the forming were discussed, too. The bigger n-value is and the relatively thicker the thickness is, the better the forming property is.Aiming at the optimization of parameters, a new method was proposed, in which uniform design was integrated with neural network and genetic algorithm. This method makes full use of the reliability of uniform design and the nonlinear mapping, network reasoning and predicting of the neural networks, but also the global optimal characteristics of genetic algorithm, and the optimum results were obtained. Finally, it proves experimentally that the computer numerical simulation is reliable and the optimal algorithm is stable.The research results in this thesis provide effective guidance and solid foundation for the application of internal high pressure forming process to automobile tubular parts. They also offer a novel and high-efficient way for parameters optimization. In this way, the trial and error method can be abandoned. Efficiency and competition can be enhanced by shortening the experiment cycle of internal high pressure forming process.