Uniaxial tensile strain measurement for ceramic testing at elevated temperatures: Requirements, problems, and solutions

Abstract

Accuracy, sensitivity and resolution requirements for strain measurement on a tensile ceramic specimen at high temperature were studied. Results indicate that current techniques and existing equipment for strain measurement can be modified and upgraded for use in high temperature testing of ceramic materials. A versatile mechanical strain extensometer capable of performing both biaxial and uniaxial strain measurements at 1200)degree)c is presented. Results of tensile and fatigue tests using the devices are also given. Additionally, two laser-based, noncontact, optical strain extensometers currently under development are described. The first method utilized the diffraction phenomenon of a light beam passing through a narrow slit. Accuracy, long-term stability, and low cost are the virtues of this method which makes it attractive for creep testing. The second method measures the in-plane surface displacement in terms of the change in phase resulting from the interference of two orthogonally polarized collinear beams which differ in frequency by a constant value. The last method is ideally suited for dynamic strain measurement. 7 refs., 11 figs.