NUMERICAL SIMULATION OF A CORNER CRACK GROWTH IN METALS UNDER MULTIAXIAL FATIGUE LOADING

摘要

Fatigue is reported as the major cause of engineering failure. Traditionally, experimental methods are employed to characterise the fatigue behaviour of a material. Nevertheless, due to its high cost and time-consuming, numerical analysis is introduced as an alternative approach to analyse fatigue crack growth accurately.In this study, a boundary element method is employed in order to simulate the crack growth in prismatic metallic bar under multiaxial fatigue loading. For this purpose, commercial boundary element method software BEASY is utilized. The generalized NASGRO equation and J-integral method is used to evaluate stress intensity factor. Cyclic torsion and bending loads are applied accordingly. Fatigue parameters studied in this work included crack aspect ratio and load ratio. Hence, analysis and prediction of crack size increment, stress intensity factors and fatigue life can be executed. It is demonstrated that corner crack on the prismatic bar tends to grow in the direction of the crack depth rather than the crack length under cyclic bending and torsion loadings despite of the initial crack size. As for the stress intensity factor distribution, the stress intensity factors are found to be higher at the position with the larger crack size, due to the stress concentration at the sharp tip of the end of the crack.