Measurement of flow stress at high temperature in solid torsion tests

Abstract

This document outlines good measurement practice to be adopted for the determination of flow stress at high temperature in torsion tests on solid metallic materials. The recommendations are applicable to hot (isothermal) tests at medium to high rates of strain (10^–3–10² s^–1) at temperatures relevant to metal working practice.

Guidance is provided on appropriate testpiece geometries and methods of verifying the temperature distribution along the length of the testpiece. Flow diagrams are given showing all the steps that are necessary, including the correction factors that need to be applied for deformational heating and for the determination of true stress. Details are given of the calibration procedures that should be followed to provide traceability to the National Measurement System.

Technical input to the document has been provided by the steering group of a European SMT funded project on High Temperature Testing, TESTIFY, that contained representatives of industrial users and producers of a wide range of engineering materials as well as academic modellers.

An experimental programme was conducted during the preparation of this document to underpin the procedures in this guide.

Keywords:

• flow stress
• high temperature
• solid torsion tests