Numeric Simulation Analysis For Pre-bending Process Of Automotive Subframe Hydroforming

Reduce the weigh of whole auto-body is one part of importance research in modern automotive, and the main way which is application of new material and advanced manufacture process besides of designing more compact components by modern designing methods. The Tube of hydroforming has become the hotspot of automatic manufacture technology, which has a construction designing flexibility, form freely, reduce the number of parts, shorten the process and then make product lighter and better quality. The subframe is the component of sedan car bearing body, and its' construction and performance is very importance to packaging the engine and transmission well and improve carrying capacity with the condition of assembly part. The sub-frame's geometrical U-sharp with curve center-line, proportion section and strong carrying capacity depend on the character of bearing and the space of install. On the base of the Tube of hydroforming technology, the hydroforming process of subframe usually consist of the process of tube pre-bending pre-expansion and/or preforming and final hydroforming. The industry of hydroforming for subframe is empty in China, however the components and parts are made in China become very urgent need, then to study the hydroforming for sub-frame of sedan car is advanced, feasibility and also is a urgent needed technology.The object of this paper is to analyze forming character, forming process parameters, factor of forming disfigurement during the first and critical working procedure-- pre-bending of Sub-frame Hydroforming. Through software of DYNAFORM, analyze tube pre-bending forming procedure ,then set up the theory for design a reasonable pre-bending process parameters by FEM simulation method, build the theory foundation for hydroforming of sub-frame made in China.The main content of this paper:Analysis the importance and development trend for lighter the automatic with the hydroforming technology of tube, describe the advanced and feasibility of simulation analysis for per-bending process of sub-frame Hydroforming by rigid-plastic FEM method.Analysis the bending process of tube by plastic mechanics theory, then make the base for numeric simulation of pre-bending of sub-frame.On DYNAFORM software set up the FEM simulation model of pre-bending of sub-frame basing, then mesh surface, define material model, select element type, define contact type and friction coefficient, define operation time , at last define tool motion loading, so the conditions of simulation are established. Having the pre-bending forming simulation for tube material aim at the control bending condition of CNC bending machine, analysis the forming disfigurement and its' forming mechanism.Using FEA simulation approach analyze the pre-bending process of sub-frame Hydroforming, avoid material wasteful in traditional "trial-and-error" approach, reduce expenses and shorten time consuming .It hope that provide theoretical information and use for reference experiences for applying the hydroforming technology of automotive subframe on the industry of automotive components in China .