Systematic errors in flow stress measurement for the hot plane strain compression test

Abstract

The hot plane strain compression test has been used for the determination of stress - strain curves at hot working temperatures. These curves are used for the establishment of the high temperature mechanical constitutive equations which are an essential part of numerical modelling tools. The test is particularly useful when the working process to be simulated is essentially plane strain (for instance, hot rolling). This work describes and quantifies the systematic errors that arise during stress determinations with the test. The paper uses analytical and numerical techniques (finite element methods) to explore the errors. Specimen geometry, friction, temperature, strain rate and strain are all important and test behaviour is different for cases where die breadth is less than specimen height compared with the reverse situation. Quantitative response surfaces for errors in stress have been determined. The paper describes how these surfaces might be used for optimising test conditions and also for the correction of experimental stress values to true effective stresses.