The Elastic-Plastic Theory of Containers and Liners for Extrusion Presses

Abstract

Reasons are given for basing the design of containers and liners for extrusion presses on elastic-plastic behaviour. After a review of the available theories on the behaviour of thick tubes and rings beyond the yield point, a solution based on the stress-difference theory of elastic breakdown is adopted. The application of this solution to containers both with and without liners is elaborated, and expressions are derived for the internal pressures sufficient to cause initial yield and full plasticity. Consideration is given to the possible occurrence of alternating yield on the inner surface of either the liner or the container. It is also found that, in certain circumstances, a tapered liner will progressively penetrate the container against the taper at pressures less than those required to produce complete plasticity. The results of the analysis are presented in the form of charts which cover the whole range of practical conditions.