నైరూప్య

Sheet metal forming analyses with spring-back deformation on U-Bends in Isotropic plates

Prabhakar.A, Dr. Mohamed Haneef, Shabbir Ahmed R.M

Forming is the most important manufacturing process. Forming is the process of converting the geometry to the required shape. Forging, extrusion, rolling and bending are some of the important forming process. The forming process includes larger deformation of the structure either with temperature or without temperature application. But in the every mechanical process certain defects exists due to the inherent resistance property of the material for forming it to the required shape. One type of defect is spring and is very important phenomenon which makes the object nonsuitable in case of rigid requirements. Spring back is mainly due to Bauchigner effect which allows the material to follow different paths during loading and unloading cycles. All forming process will take places in the plastic region. So to analyse or to estimate spring back, nonlinear material properties which will accommodate stress strain relations in the nonlinear regions are required In the present work, spring back phenomenon with steel material is analysed using Finite element software Ansys. Two parameters are considered for finding the spring back effect. Initially the sheet metal thickness effect on spring back is analysed. The geometry is built and meshed with 4 noded quad elements which allow plastic properties. Eulerian contact definitions are created between the punch, die and sheet metal with large deformation effects. The displacement loading is applied through the punch. Targe169 and contac172 elements are used for forming process. The results for vonmises stress, residual stress, plastic strain, spring back deformations are captured and tabulated. Similarly the analysis is continued with depth of forming process and its effect on spring back. The results shows with the thickness spring back values are coming down but with the depth of deformation spring back values are increasing. So finite element simulation helps in finding the inaccuracy levels if the member material properties are given which helps in setting the tolerances for the geometry either for assembly or surface finishing operations. All the values like vonmises stress, residual stress, contact pressure, plastic strain and spring back are increasing with depth of the forming process.