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

Highlights: • SPT correlation factors calculated are dependent of the materials. • Bottom displacement provides more extended linearity during regime I. • Plastic energy evaluations provide new criteria to select PY. • t/100 method is more representative to define the plastic spreading on SPT. The assessment of the yield strength σ_YS from characteristic load P_Y 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 P_Y were considered: Mao and a modification of Mao methods and t/100 and t/10 offset methods. The attempt of correlation between σ_YS with P_Y/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 P_Y. The advantage to use the bottom displacement measurement during regime I of deformation is discussed on the assessment of Young modulus and P_Y. Finally, the representativeness of P_Y as the beginning of massive yielding of SPT specimen is also analyzed in terms of plastic energy E_PL calculated from SPT plot. Based on the study of E_PL evolution during the first regime of deformation, the t/100 offset method resulted the most suitable to select P_Y as characteristic parameter of the beginning of yielding when compared with the other three methods.