A normalized damage variable for ductile metals based on toughness performance

The normalized damage function based on elastic modulus is proposed to evaluate damage for ductile metals under a unified criterion. An equivalent half-sine model is employed to illustrate plastic stress–strain relationship. Toughness indicator is introduced to describe the toughness character in metals. An exponential rule is employed to calculate toughness indicator, and the parameter of toughness indicator is formulated by conventional mechanical properties of metals. Repeated loading–unloading tensile tests are conducted on stainless steel and aluminium alloy. The good correlation coefficient and dispersion are presented between the experimental values and predicted values of damage variable (within 12%). The damage function with toughness indicator can be applied to predict the effective elastic modulus.