Constant true strain rate apparatus for use with Instron testing machines

Abstract

A simple device is described for use with the Instron variable speed unit to produce a constant true strain rate in compression or tension. The device includes a facility for making small strain rate changes during a test cycle. The new strain rate is selected from two arbitrary levels ranging from 0.5 to 2.0 times the initial strain rate. The changes are accomplished in 70 ms and are achieved without discontinuities in strain rate. The effect of machine stiffness on the specimen strain rate obtained with this apparatus is also discussed.