Abstract: Wrinkling is a crucial forming defect in continuous multi-point forming process. Principle of continuous multi-point forming is explained. Finite element analysis model of spherical surface is established. Numerical simulation method is adopted to study the wrinkling. Simulation result of wrinkle of 08Al sheet metal with 0.5 mm thickness during forming process is obtained. The result shows that wrinkles happen on two sides and two ends of sheet metal. Reasons for wrinkles happening and not happening are analyzed by use of principal strain states of shell element middle surface in different regions of sheet metal. Simulation results of wrinkles on ends of 08Al sheet metal with 0.5 mm, 1.0 mm, 1.5 mm and 2.0 mm thickness under different displacements of upper flexible roller are obtained. The results show that when thicknesses of sheet metal are identical, the deeper the displacement of upper flexible roller is, the more serious the wrinkles will be ; when displacements of upper flexible roller are identical, the thicker the sheet metal, the more difficult the happening of wrinkles. The change rule of wrinkles on ends of sheet metal is analyzed and explained reasonably. Experiments are carried out. Experimental results basically agree with simulation results.

Key words: Flexible forming, Numerical simulation, Sheet metal forming, Three-dimensional surface