Forming tubular hexahedral screws—Process development by means of a combined finite element-boundary element approach

Abstract The aim of the present paper is twofold: first, to propose a new forming process that is capable of producing hexahedral heads with washers in tubular screws and, second, to present a numerical approach to solve the plastic deformation of the tubular preforms and the elastic deformation of the dies. The methodology draws from independent determination of mechanical properties and fabrication of prototypes with a forming tool designed and fabricated by the authors to the development of a direct boundary integral element formulation for solving the elastic deformation of the dies inside an existing in-house finite element computer program. The performance of the proposed forming process is assessed by experimentation and results and observations are explained in the light of the proposed numerical approach based on the combination of the finite element (FE) with the boundary element (BE) methods. Because project and design of tooling is often only dependent on boundary solutions for the elastic deformation of dies and for the contact between the workpiece and the dies, the proposed FE–BE approach seems as a cost-effective methodology that avoids discretization of dies by finite elements, reduces the overall size and improves the performance of the resulting computer models.