Modeling of dislocation interaction in FCC metals and its application to nonproportional cyclic loading
Hasebe Tadashi; Shibahara Ken; Imaida Yutaka
Abstract:This paper proposes an evolution equation of hardening for FCC crystals from the microscopic point of view. The dislocation interaction with forest is considered to be responsible for additional hardening, which is experimentally observed in nonproportional loading for FCC polycrystalline metals with low stacking fault energy. The proposed model is incorporated into the constitutive equation based on the rate dependent crystalline plasticity theory, and is applied to both monotonic and cyclic nonproportional loadings. In the former case, compressive tests following pre-torsion are conducted on three FCC metals with different stacking fault energy and the material dependency on hardening behavior is compared with the analytical results. The simulated results in the latter case, on the other hand, are compared with the formerly reported experimental results. The variations of additional hardening with strain path as well as material are demonstrated to be successfully described by the proposed model. The transition of the hardening behavior found in the stair step path is also simulated. Small additional hardening reported under a large number of stair steps can be described by the present analysis, which results from small nonproportionality in plastic strain history. Key Words:crystalline plasticity, nonproportional loading, FCC metal, additional hardening, dislocation interaction