Modelling of the cone-type rotary piercing process and analysis of the seamless tube longitudinal shear strain using industrial data

Abstract

In this article an analysis of the cone-type rotary piercing process of seamless tubes by means of a finite element model is presented. The originality of the proposed study is the utilisation of the shear strain of the material for the experimental validation of the model. The cone-type rotary piercing process is a complex procedure in which the material is subjected to severe plastic deformation and to surface twisting that leads to shear deformations. In addition, extreme friction conditions and high temperatures occur during the process which increase the difficulty of the process itself and its simulation. Consequently, the experimental validation of numerical models of the process cannot be accomplished exclusively based on power and velocity terms, as it is usually done. Instead, in this paper it is demonstrated how still another experimental parameter is required for the correct simulation of the process, which is the shear strain of the material, measured through the values of longitudinal surface twisting. This way, a new methodology for the analysis of the cone-type piercing process is proposed in the paper, which establishes a relationship between the material contact with the elements of the piercing mill and the resulting power consumption, process performance, forces exerted and longitudinal surface twisting of the material. Thanks to this methodology, it is shown that the relation between the material contact with the mandrel and the rolls in their initial surface region is responsible for the process performance, while the contact with the rolls in the region where the tube exits the piercing mill defines the surface twisting of the material and thus its shear deformation.