Development of a failure strain surface in average stress triaxiality and average lode angle domains of a low temperature high strength steel

초록

The paper deals with formulation of failure strain according to average stress triaxiality and normalized lode angle of a low temperature high-tensile steel, EH36, used for arctic marine structures. Stress triaxiailty and lode angle are known the factors mainly governing fracture initiation of most ductile metals. A number of tests are conducted for round and flat tensile specimens with different notches from relatively smooth to very sharp levels, and specially designed specimens to induce pure shear failure and shear-tension failure. Nonlinear finite element simulation of each specimen is performed to obtain stress and strain fields at fracture initiation. Three dimensional failure strain surface is proposed in the average stress triaxiality and normalized lode angle domains. In order to verify validity of the surface, tensile tests are conducted for asymmetric notch specimens which are indirectly representing fracture-anticipating parts of real marine structures. It is concluded that the proposed fracture surface well predicts fracture initiation of the real structures.