Study of hardening and cyclic plastic behaviour around the crack tip of C(T) specimen made by as-received and annealed copper

The purpose of this research is determining experimentally the characteristics of tension and cyclic plastic behaviours of as-received and annealed coppers and studying distribution of stress/strain field near the crack tip. Samples made by pure copper were annealed at 420 degrees C for 40 minutes in electric furnace. To determine the properties of the cyclic plastic behaviour, proper tests with symmetric strain-controlled conditions were performed on standard samples. Chaboche nonlinear hardening model was used to determine the cyclic plastic behaviour of both materials. According to results, annealing process creates isotropic hardening in the copper and also changes its initial kinematic hardening behaviour. Effects of the annealing and hardening on the variations of the stresses and strains around the crack tip were investigated. Also, ratcheting and mean stress relaxations versus number of cycles, inside the plastic region, were studied.