Analysis of axisymmetrical compression processes by the finite element method

In the study of compression processes, analytical methods use to be applied under plane strain conditions due to limitations of their own formulation [1]. However, axisymmetrical workpieces are more commonly used in industrial processes, so the use of numerical methods is often neccesary. In this sense, the Finite Element Method (FEM) is a powerful numerical tool that can simulate more realistic conditions of these processes [2]. In the study of compression processes between parallel flat dies (such as forging or indentation) several parameters are usually involved. The friction on the flat die-workpiece interface is is one of the most important parameters to be considered [3]. Additionally, other factors mainly related to the geometrical dimensions of the problem are also relevant. Mainly, attending to the geometry of the problem different cases can be defined. Thus, the indentation and the forging of a cylindrical billet can be similarly studied assuming different dimensions of the dies and the workpiece, in each case. Thus, when the diameter of the workpiece is longer than the diameter of the die, indentation processes are developed. On the contrary, forging processes are distinguished when the diameter of the workpiece is shorter than the diameter of the die. In order to identify different cases to be solved for both types of compression processes a shape factor has been considered. This is defined as the ratio between the diameter and the height of the workpiece that is used to relate two dimensions of the process. Different axisymmetrical compression processes have been analysed by FEM in order to study the influence of the shape factor on the calculation of the required forces and contact pressure distributions [4]. Results are compared between forging and indentation problems. The main conclusion of this study is that, for the same material, a change of the geometry can cause different values of the required energy to carry out the plastic deformation and also, different contact pressure distributions. With a right selection of the geometrical parameters, a more economical process and the extension of the tool life can be achieved [5].