Optimization of pre-form shapes by response surface methodology for hydro-forming of 780 MPa torsion beam

With the increasing use of advanced high strength steel for automotive components, hydro-formed hollow components have the advantage of both high strength and high stiffness. In order to manufacture a 780 MPa torsion beam satisfied with both improved safety and lightweight, hydro-forming process of 780 MPa torsion beam was studied by experimental research and numerical simulation. Pre-form design according to central composite method was carried out to avoid forming flash and bursting during hydro-forming. Response surface model of the effect of pre-form structure on thickness distribution was developed, and significance of structural parameters on the response value was discussed. According to the genetic algorithm, an optimum pre-form shape has been obtained. An experiment was carried out on the basis of the optimum pre-form shape, and the effect of loading paths was deeply discussed on hydro-forming process. It is shown that the axial feeding within acceptable range can significantly improve the thickness distribution and forming accuracy. Finally, a well hydro-formed torsion beam is manufactured.