Design of an automotive frame cross member for the hydro-forming process using computer aided engineering

Abstract

Hydroforming is a forming technology in which a steel tube is set in a die and formed to fit a specified shape by applying hydraulic pressure from inside the tube while also applying force in the tube axial direction (axial feed). In the present study, the whole process chain of frame component (cross member) simulation and development by hydroforming technology to apply to a high strength steel having a tensile strength of 440 MPa grade is studied. At the part design stage, a feasibility study and process design aided by CAE (Computer Aided Design) to confirm the hydroformability in detail is required. The overall possibility of the hydroformability of the frame part could be examined by cross sectional analyses. Moreover, it is essential to ensure the formability of the tube material in every forming step such as pre-bending and hydroforming. At the die design stage, all the components of the prototyping tool are designed and the interference with the press is investigated from the geometry. For the improvement of tube thinning, the hydroforming was carried out adding an axial feeding of 45 mm at both ends of the part for supplying materials to the end zone where thinning occurs and retards burst. From this treatment, the thinning of the tube wall was experimentally measured and it was improved by 17.9%. It is in good agreement with the calculation and the position of the maximum thinning corresponds to the result of the simulation.