Analysis of Stress Distribution in Tensile Test Specimens Using Modified Versions of a Novel Gripping System

Abstract

This paper deals with the effect of novel gripping systems developed for tensile testing on the stress distribution inside the test piece. The uniformity of the stress distribution plays a decisive role in measuring the upper yield strength and creep behavior of materials. In this study two modified versions of a recently developed gripping system are introduced and tested together with the original version. The tests consist of measuring the bending stress/axial stress ration during elastic loading of the test piece. The bending stress/average stress ratio was measured using a special strain gauge mounted test piece, which was loaded by elastic tension. The results show that the gripping systems provide the self-alignment of the test piece at the beginning of the loading; therefore they can ensure almost true uniaxial conditions for tensile testing. The average bending stress/axial stress ratio is found to be just 1-2 %, so, the gripping systems can provide the accurate measurement of upper yield strength and creep curves of materials.