Residual Fatigue Life Estimation of Structural Components Under Mode-I and Mixed Mode Crack Problems

The work presents a residual fatigue life prediction methodology of cracked structural components under interspersed mode-I and mixed-modes (I and II). In this paper the numerical computation methods and procedures for predicting the fatigue crack growth trajectories and residual fatigue lives of notched structural components are analyzed. Special attention in this work is focused on notched structural components such as aircraft wing skin type structural components under mixed modes and cracked aircraft lugs under mode-I. Stress intensity factor (SIF) solutions are required for assessment fracture strength and residual fatigue life for defects in structures or for damage tolerance analysis recommend to be performed at the stage of aerospace structure design. A variety of methods have been used to estimate the SIF values, such as approximate analytical methods, finite element (FE), finite element alternating, weight function, photo elasticity and fatigue tests. In this work the analytic/numerical methods and procedures were used to determine SIF and predicting the fatigue crack growth life of damaged structural components with notched cracks. For this purpose, finite element method (FEM) is used to derive analytic expressions for SIF of cracked structural components. To obtain the stress intensity factors of cracked structural components special singular finite elements are used. The strain energy density method (SED) and MTS criterions are used for determination of the crack growth trajectories in thin-walled structures. Computation results are compared with experiments