Numerical Simulation and Flaws of Sheet Metal Single-point Incremental Forming

The definition of motion trajectory of forming tool is a puzzle when setting up a finite element method(FEM) model of single-point incremental sheet forming.On the basis of DYNAFORM software,a basic FEM model was firstly constituted,and then the displacement coordinates of the forming tool which were received from numerical control(NC) code directly were added to the keyword file of the FEM model,thus an arbitrary complicated movement trace of the forming tool could be defined.Two problems maintained in the processing tool path generating from NC code,the concentration of the tool setting points and the single machining direction,which might bring about fracture and instability flaw respectively.As the plastic deformation in the tool setting point was large,the accumulative effect of the deformation of the tool setting zone might result in the severe wall thickness reduction.The distribution method in which the distance of the two adjacent setting points must be larger than the maximum radius of the plastic zone was employed to settle this problem.Meanwhile,the forming instability flaws such as collapse and ridge,which came from material accumulation during the process with single machining direction,were overcome by utilizing the forward and backward forming method.