关键词: 三维型材, 拉弯, 轨迹, 变形控制, 数值模拟

Abstract:

A trajectory design method using deformation controlled finite element (FE) simulation is presented for the three-dimensional (3D) profile stretch bending process. First, a curve is extracted from the CAD model of the stretch bending die to represent the lengthwise feature of the die and it is discretized into many line segments. Thus the process of the blank wrapping the die becomes a process of the blank wrapping these line segments. Then the deformation of the blank as it wraps around each segment is given; thus blank end displacements are calculated according to this deformation mode and its tangent contact condition since in stretch bending the blank is tangent to the die surface where it leaves the die. The calculated end displacements are input into the FE model as boundary conditions to compute the stress, strain and springback of the workpiece. Deformation mode is adjusted according to forming limit diagram （FLD）and maximum springback error, so the optimized one can be found, which in turn optimizes the stretch bending trajectory. Finally, the detailed design process of a trajectory for 3D stretch bending of a rectangular hollow profile is given as an example.

Key words: 3D profile, stretch bending, trajectories, deformation controlled, numerical simulation