Abstract
To improve fuel economy and crash safety in the automotive industry, three-dimensional hot bending and direct quench (3DQ) technology, which enables the formation of hollow automotive parts with a tensile strength of 1470 MPa or more, has been developed. In this paper, the forming characteristics in 3DQ are investigated by experiments and FEM analysis. The main results are as follows. (1) Measured and calculated bending force and twisting torque are low and within the load capacity of general robots. (2) The constraint at the tube top by the robot in 3DQ can increase the accuracy of products even in inhomogeneous coiling. (3) A narrow deformation area suppresses the change in the product cross section, and it is clarified that the calculated maximum value of σθ/σl is closer to 0.5 in a narrow deformation area, where σθ is circumferential stress, and σl is longitudinal stress. (4) The effects of the maximum heating temperature and the feeding speed on the deformation area are small.
