Numerical Simulation On Wrinkle And End-effect In The Flexible Forming Of Sheet Metal

The 3-D surface flexible bending technology is a novel method for sheet metal flexible forming. Its basic principle is that sheet metal can be formed by continue local way through the curve of changeable curvature which is composed of several short rollers with highly adjustable, revolving and sway ability themselves and then through short roller's press displacement and friction between rollers and sheet metal. Sheet metal can be formed by the curve which is composed of adjustable rollers according to the target work piece's shape through this technology, in a way, it is the combination of traditional bending and multi-point forming, and have the characteristics of shortcut, high quality, low cost, flexible ability and intellectualized ability, these characteristics are just needed in a lot of industry such as aviation, shipbuilding, chemical industry and boiler industry.With computer applications and the maturity of nonlinear finite element, the numerical simulation technology of sheet metal forming is developed quickly. Now the technology is widely applied in the die design for forecasting forming defects. in the flexible forming of 3D-surface, the dynamic explicit finite element arithmetic is very suited to simulate the sheet metal forming because the contact between the elements and the sheet is discontinuous and the loading condition is very complicated. So a dynamic explicit finite element software ANSYA-LSDYNA is introduced to simulate in the flexible forming of 3D-surface, studied the wrinkle and end-effect in the forming process, and the solution was given.The main contents and results as follow:1) Established FEA model flexible forming of 3D-surface: Using LS-DYNA explicit dynamical analysis method, choosing BWC algorithmic cell—SHELL163, analyzing non-linear inelastic material model, confirming boundary conditions, short roller's virtual rotate speed and local coordinate according to the principle of 3-D surface flexible bending process, giving the sphere part's and saddle part's FEA models. simulated the wrinkle under different thickness, displacement and character of sheet metal., drew the following results: the sheet metal is more thick, the phenomenon of wrinkle is less obvious, the thickness of sheet metal could inhibit the phenomenon of wrinkle effectively; the displacement of up roller is bigger, the deformation of sheet metal is more obvious, the phenomenon of wrinkle of vertical of sheet metal are less obvious; the forming of 1010steel is better than AL5182, AL5182 is easier to come into the phenomenon of wrinkle.2) Given the influence of end-effect in the start and end of sheet metal: in the beginning of deforming, sheet metal's deformation decrease gradually in the width direction, radius of curvature increase gradually. When radius of curvature tends to infinity, the deformation of sheet metal start to deform in another direction .in the end of forming, sheet metal's deformation increase gradually.3) Described the phenomenon of end-effect in the flexible forming of 3D-surface, simulated the phenomenon of end-effect under different thickness, displacement and character of sheet metal., drew the following results: the sheet metal is more thick, the probability of the appear of the phenomenon of end-effect is less, the thickness could inhibit the phenomenon of end-effect effectively; the displacement of up roller is bigger, the effect of end-effect is less, the displacement of up roller could effect the phenomenon of end-effect; the forming of 1010steel is better than AL5182, AL5182 is easier to be effected by end-effect.4) Discussed the influence of forming size of FEA model and sheet metal to wrinkle and end-effect, drew the following results: the horizontal size of sheet metal is smaller, the forming effect of sheet metal is better; the horizontal size of FEA model is smaller, the forming is acuter, the influence of wrinkle and end-effect is bigger; the space between the down rollers is longer, the forming of sheet metal is less, the influence of wrinkle and end-effect is less obvious.5) Compared the forming effect of saddle surface and sphere surface, drew the following results: the forming effect of saddle surface is better than sphere surface, the sphere surface is easier to be influenced by wrinkle and end-effect.6) Simulated the process of the restrict of wrinkle and end-effect of saddle surface and sphere surface, drew the following results: rolling number is bigger, the forming effect of sheet metal is better for saddle surface and sphere surface, meanwhile, the time of given is more, the forming effect of sheet metal is better for saddle surface and sphere surface.