Study Of Sheet Metal Formability In Incremental Forming

Incremental sheet forming is a new flexible sheet forming process. It does not need a dedicated die and can form sheet parts with a higher forming limit and of complicated shape by use of a CNC device. This process is suited to the forming of sheet parts of small volume, diversification and complicated shape in space-flight, automobile and civil production.In this paper, put forward a simulation technique that different from the technique of much steps simulate sheet forming and establish three-dimensional elastic-plastic FE model for the continuous forming process.Carry through numerical simulation to the process of incremental sheet forming that is based on the FE software DYNAFORM, and bring forward a project to investigate forming limit of sheet in incremental forming process. At last, make sure the project is feasible through analysis.The paper's important content and production are:(1) Set up three-dimensional elastic-plastic FE model for incremental sheet forming. Realize continuous simulation process for incremental sheet forming through imposing time-displacement curve to control its motion on the punch;(2) Analysis the key technique of continuous simulation for incremental sheet forming. Realize the three-dimensional motion of the punch and the motion of the clamping that following punch's motion. In order to avoid sheet element penetration, the SLSFAC take 0.01 as its initial value and enlarge it form one to threemultiples. The time-step of explicit finite element method(FEM) achieves 10^-810^-9 s and the time interval of elements adaptive refinements achieves 10^-4 10^-5 s.(3) The size and the incremental value of punch are optimized. Diameter of the half ball punch is 6mm and incremental value is lmm.(4) Feasibility that investigation of forming limit of incremental sheet forming process has been validated, through FEM numerical simulation. Bring up twoprojects of forming path for research different straining conditions of sheet. To consider that when curvature of path decreased the ratio el to e2 will be increased,which is obtained through analysis of elements major strains and minor strains in different forming paths. The straining conditions of sheet show a tendency to uni-axial stretching along the straight edges. And, straining conditions is between uni-axial stretching and bi-axial stretching for imposing three-dimensional spiral path to the punch. At the same time, straining conditions show a tendency to bi-axial stretching which is following to the decrease of radial radius of path.Above all, study of incremental sheet forming process and of sheet forming limit with numerical simulation method, which is feasible.