Finite element analysis of axisymmetric sheet stretching process

The incremental updated Lagrangian elasto-plastic finite-element method (FEM) was employed in this study to analyse sheet stretching under the axisymmetric condition. The extended r _min technique is utilized such that each incremental step size is determined not only by the yielding of an element Gaussian point, but also the change of the boundary condition along the tool-metal interface. The frictional force in the contact region between the sheet and the tools is computed by the application of Coulomb’s friction law. Low-carbon (BA-DDQ) sheet plates were used throughout the experiments, which were later performed using a hemispherical punch head. Experimental tests were performed to demonstrate formulation of the theory and development of the computer code. The experimental load shows good agreement with the value of the punch load predicted by the finite-element method. When performing numerical calculation, the entire loading process history, the deformed geometry, the nodal velocity, and the distributions of strain and stress are also obtained by considering carefully the moving boundary condition. From the results of the experiment and the FEM, it may be concluded that the method proposed here provides a good model for simulating the axisymmetric sheet stretching process.