Notch Tensile Strength of Ductile Materials

Notch tensile tests are performed to evaluate the effects of stress triaxiality at the net section and uniaxial tensile properties on the notch strength ratio. Notched cylindrical specimens with a U-shaped circumferential notch are employed. These specimens are made of eight kinds of materials chosen for providing a wide variety of deformation characteristics. The notch strength ratio increases with stress triaxiality factor proportional to the ratio of hydrostatic to equivalent stress, and with the ratio of local to total elongation in an engineering stress-strain curve. The notch strength ratio is determined by the multiplication effect of these two factors. Notch strengthening occurs owing to the strong multiplication effect. The value of the notch strength ratio can be obtained by an empirical equation expressed in terms of these two factors. The notch strength ratio is independent of the absolute quantity of ductilities of a material.