Effects of thickness specimen on the evaluation of relationship between tensile properties and small punch testing parameters in metallic materials

Abstract

The assessment of the yield strength σYS from characteristic load PY obtained from small punch tests (SPT) was studied systematically in aluminum alloys and structural steels by variation in thickness of specimens. Four methodologies of calculating PY were considered: Mao and a modification of Mao methods and t/100 and t/10 offset methods. The attempt of correlation between σYS with PY/t2 by using a unique linear parameter of correlation α was reviewed. Under this framework, it is suggested that the dependence of this correlation factor α with each material cannot be avoided for the four methodologies used to calculate PY. The advantage to use the bottom displacement measurement during regime I of deformation is discussed on the assessment of Young modulus and PY. Finally, the representativeness of PY as the beginning of massive yielding of SPT specimen is also analyzed in terms of plastic energy EPL calculated from SPT plot. Based on the study of EPL evolution during the first regime of deformation, the t/100 offset method resulted the most suitable to select PY as characteristic parameter of the beginning of yielding when compared with the other three methods.