Influence of the material anisotropy in the estimation of the yield strength with the Small Punch Test

Abstract

The Small Punch Test (SPT) was developed in the 80’s as an alternative miniature test for the characterization of mechanical properties in the nuclear industry. One of the key aspects that materials must fulfill to be used with this miniature test is that of homogeneity and isotropy. The origin of the isotropy requirement comes from the fact that the estimation of mechanical properties using the SPT requires empirical correlations with standard tests, which generally show uniaxial stress fields. By contrast, the SPT shows a multiaxial stress field. There are few publications related with the influence of material anisotropy in the yield strength estimation using the SPT, and most of them are empirical studies. This research was intended to address, with a systematic finite element analysis, the influence that different anisotropy combinations could show in the yield strength estimation using the SPT. Thirty-six anisotropic hypothetical materials were evaluated with SPT simulations using the Hill’48 yield criterion. The yield strength of each material was estimated with the SPT using four correlation methods: Mao’s, CEN’s, the t/10 offset, and the optimized t/10. This study concluded that the SPT was not an appropriate test to evaluate or quantify the material anisotropy, but it was a valuable experimental test to estimate a mean yield strength of the six yielding stress components of the anisotropic material.