Application of Pre-Strained Steels in Empirical Correlation Between Small Punch Test and Uniaxial Tensile Test

Abstract

In order to research the method of strength empirical correlation between conventional small punch test (SPT) and uniaxial tensile test, a series of austenitic stainless steel including pre-strained SUS304 have been tested in this study. The conventional SPT is conducted on a small disc-shaped specimen whose edge is firmly gripped by a die, and the specimen is deformed by a punch. The method of empirical correlation between SPT and uniaxial tensile test is a direct way to obtain the mechanical properties of materials. Through establishing the strength empirical correlation, it can achieve to calculate the strength of material by SPT which is nondestructive to equipments. However, the per-strained steels have never been tested in this method. This study is to fill that gap and to obtain the empirical correlation between SPT and uniaxial tensile test with pre-strained steel. In this study, a series of austenitic stainless steel including SUS304 after different levels of pre-strain were tested successively by uniaxial tensile test and SPT. It is found that the tensile strength obtained from uniaxial tensile test increases with the increasing levels of pre-strain. However, the maximum load obtained from prestrained SPT specimen does not increase with the increasing levels of pre-strain. It is contradictory to the linear relation between maximum load and tensile strength. According to the analysis of conventional discshaped SPT specimen, the directions of maximum load obtained from SPT and tensile strength from tensile test are not uniform. It results in the non-linearity between the maximum load and the tensile strength with pre-strained steel, and it indicates the pre-strained steel cannot be applied to the conventional disc-shaped SPT specimen. Furthermore, the prestrained steel is a typical kind of anisotropic material. Therefore, extending to anisotropic material, the conventional disc-shaped SPT specimen is not suitable for the method of strength empirical correlation.