• A Fast New Numerical Tool for Designing Pre-stressed Dies for Backward Extrusion: Part 1: Die Behaviour

      Bonnavand, F.; Bramley, Alan N.; Mynors, Diane J. (Professional Engineering Publishing, 2001)
      Prestressed die inserts are often used in the forging of axisymmetric parts. Their use enhances overall tool economy and can enhance the quality of the finished forging. The design of tooling that incorporates prestressed die inserts is, however, complex. The complexity arises from the interrelated phenomena that occur within the dies during the forging process. As a result, it is not possible to obtain an analytical expression for critical parameters such as die stresses and deflections. This paper shows the limitations of currently used design methods, and identifies, for the backward extrusion process, which physical phenomena should be taken into account when designing prestressed tooling. (Professional Engineering Publishing)
    • A fast new numerical tool for designing prestressed dies for backward extrusion: Part 2: numerical analysis

      Bonnavand, F.; Bramley, Alan N.; Mynors, Diane J. (Professional Engineering Publishing, 2001)
      The economics of forging requires tools to be designed to ensure maximum service life. Ideally, this should be achieved by determining the maximum equivalent stress experienced by tools during service. However, the determination of the maximum equivalent stress in the dies through numerical simulations is very time consuming. For the case of a backward extrusion process, this paper proposes a method for its determination that is based on an analytical function of the process parameters. This function was obtained by generating a database that includes the maximum equivalent stress for a large range of process parameters. This database was then modelled by a function determined through statistical analysis. (Professional Engineering Publishing)