Search

Springback is a common phenomenon in sheet metal forming since the elastic recovery of the internal stresses is induced after removal of the tooling. The numerical analysis of springback is a complicated time-consuming job and its result is greatly effected by a type of the yield function, finite elements used and the constraint condition for eliminating a rigid body motion. In this paper, optimization of the draw-bead force is carried out utilizing the response surface method in order to reduce springback and improve shape accuracy of a deep drawn product. In the optimization process, the tendency of springback is evaluated qualitatively without springback simulation usually done with the implicit solving scheme. Instead of springback simulation, the amount of stress deviation along the thickness direction in the deep drawn product is used as an indicator of springback. The stamping process is analyzed for a front side member formed with advanced high strength steel (AHSS) sheets such as DP60. The analysis procedure fully covers the binder-wrap, stamping, trimming and springback processes with the commercial elasto-plastic finite element code LS-DYNA 3D. The effect of the restraining force of draw-beads is confirmed with the decreased stress deviation. The analysis result shown in the final springback simulation demonstrates that the present analysis provides a guideline for controlling the evolution of springback based on the finite element simulation of complicated auto-body members. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper is concerned with the quantitative effect of the draw-bead and the blank holding force on the sheet metal formed part. The draw-bead analysis is newly carried out to provide the restraints force of the draw-bead for finite element analysis of sheet metal forming. The draw-bead analysis has been carried out in the two steps: first, the draw forming analysis has been carried out; and secondly, the drawing analysis has been performed. The results provide the restraint force of the draw-bead as well as the displacement in the region of the draw-bead, which is utilized as boundary conditions in finite element analysis of sheet metal forming. And then, the sheet metal forming analysis is carried out to investigate the effect of the draw-bead on the quality of forming. Numerical results demonstrate that the forming history becomes totally different depending on the restraining method such that the forming is not successful with the use of only the blank-holding force while it is successful with the use of the draw-bead. It is also noted from the comparison of the analysis result with the experimental one that the present analysis method is effective in sheet metal forming simulation. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]