A SIMPLE, HIGH-PRECISION BIAXIAL EXTENSOMETER FOR HIGH-TEMPERATURE CREEP STUDY

A biaxial extensometer for high temperature creep study is described. The axial displacemnt is measured by a linear variable differential transformer, the angular displacement by a rotary variable differential transformer. The possible interference between the axial and angular displacement measurements is minimized by using instrument linear motion ball bushing bearings and case hardened shafts. Examples of applications are given for a constant shear strain rate test and a creep test at 200 degree C under abrupt changes of stress states performed on a thin-walled tube specimen made of 2618 aluminum alloy.