Novel specimen for the effective measurement of the fracture strain along with stress triaxiality and Lode parameter

A double notched central hole, i.e., DNC specimen, which contains a center hole with a left side notch and a right side notch accompanying the slope α, is proposed to simultaneously achieve dual values of stress triaxiality and Lode parameter from one specimen in the present study. Analytical and numerical approaches are carried out under decent assumptions to characterize the plane strain behavior of DNC specimen along with the slope α. Quasi-static tensile tests with conventional specimens and DNC specimens revealed plastic strains at fracture for each specimen case in accordance with stress triaxiality and Lode parameter by digital image correlation. It is found that one DNC specimen successfully provides dual values of stress triaxiality and Lode parameter at the same time; therefore, it saves up to 50 % of experimental time and labor of conventional specimens.