Strength and Formability Designs of Tube-hydroformed Automotive front Sub-frame

Abstract To call for carbon cut, the automobile industry has been widely used tube-hydroforming technology instead of traditional stamping technology to achieve the reduction of structural weight, the enhancement of vehicle structural strength and low fuel consumption. This study targets on automobile front suspension system in modifying the front sub-frame design from stamping-welding parts to a one-piece tube-hydroformed part. First of all, this study refers to the result of cross-section analysis to put up with the modification directions to meet the part strength and manufacturability requirements. According to the modified finished surface, the part strength was evaluated by the comparing the stress and strain distributions of the tube-hydroformed part with those of stamping-welding parts. The impact properties of the tube-hydroformed part was also examined and the results indicated that the tube-hydroformed part exhibits a satisfactory impact mechanism and better capability in energy absorption compared to the stamping-welding parts. The die design for tube-hydroforming the front sub-frame was then investigated in the present study. Both the bending process and the perform design were optimized to avoid the presence of fracture. The proposed tube-hydroformed part design and the manufacturability of this part were validated by the production part. The consistency between the finite element simulation results and the production part in dimension accuracy confirms the effectiveness of the tube-hydroformed part design established in the present study.