Precision of Measured Stress and Strain in Compression Test for Cylindrical Specimen

Abstract

The precision of the measured stress and strain in a compression test was evaluated numerically and experimentally. Attention was focused on a simple compression test on a cylindrical specimen whose geometry is specified by ASTM E9. Elastic-plastic finite element analyses were carried out to examine the uniformity and uniaxiality of stress and strain. The stress distribution was evaluated in the cross section at the centre of the specimen and the strain distribution was evaluated on the outside surface of the specimen and also in the radial direction in the specimen corresponding to each evaluation point on the outside surface. The parameters changed in the numerical analyses were the yield stress and work-hardening ratio of the material, the aspect ratio of the specimen, and the friction coefficient. Numerical results showed that the parameter most strongly affecting for the precision of the measured stress and strain is the work-hardening ratio of the material, and that the lower its value the poorer the uniformity and uniaxiality. Experimental results using steel with a low work-hardening ratio showed good agreement of the axial strain on the outside surface of the specimen with the numerically predicted results. The recommended aspect ratio of the cylindrical specimen is over 2.5, and a ratio of 3 is sufficient enough to ensure the precision of measured results.