Simulation of dynamic ductile crack growth using strain-rate and triaxiality-dependent cohesive elements

Rate-sensitive and triaxiality-dependent cohesive elements are used to simulate crack growth under quasi-static and dynamic loading conditions. The simulations are performed for a middle-cracked tension M(T) specimen made of an aluminum alloy (6XXX series). To consider the effect of stress triaxiality and strain rate on the cohesive properties, a single plane strain element obeying the constitutive equations of a rate-dependent Gurson type model has been used. The single element is loaded under various stress biaxiality ratios and strain rates and the obtained stress-displacement curves are considered as traction separation law for the cohesive elements. These curves are used for analyzing the aluminum M(T) specimen. The qualitative effects of constraint, strain rate, inertia and stress waves on the energy absorption of the specimen and crack growth are discussed.