EH36강의 평균 응력 삼축비 및 정규 로드각을 고려한 3차원 파단 변형률 평면 개발

초록

This paper proposes a formulation of failure strain according to average stress triaxiality and lode angle of a low temperature high-tensile steel EH36 used for arctic marine structures. Stress triaxiality and lode angle are known to be the most important parameters for prediction of failure strain of ductile metals. In order to obtain failure strains at broad ranges of two parameters, a number of tests are conducted for tensile specimens with flat and round cross sections, pure shear specimens, and shear-tension specimens. All specimens are prepared to have various notches. 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 the normalized lode angle. User subroutine of Abaqus/Explicit is developed to check availability of three dimensional failure strain surface. The failure surface is verified by comparison of simulated fracture with test one for asymmetric notch tests (structure tests) which is specially conducted for comparative study. It is concluded that the proposed facture surface well predicts fracture initiation of the real structures.