Fatigue Crack Growth Analysis of Damaged Structural Components Under Mode-I and Mixed Modes

 

Katarina Maksimović

 

The work presents a life prediction methodology of damaged structural components under the interspersed mode-I and the mixed-mode (I and II). This work considers the numerical computation methods and procedures for predicting the fatigue crack growth life for cracks at notched structural components. A special attention is focused on notched structural components under mixed modes. Stress intensity factor (SIF) solutions are required for assessing fracture strength and residual fatigue life for defects in structures, or for damage tolerance analysis recommended to be performed at the stage of the aerospace structure design. A variety of methods has 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 SIFs and predict the fatigue crack growth life of damaged structural components with notched cracks. For this purpose the finite element method (FEM) is used to derive analytic expressions for SIFs of cracked structural components. To obtain the stress intensity factors of cracked structural components, singular finite elements are used. The strain energy density and MTS criteria are used to determine the crack trajectory or the angle of crack growth in thin-walled structures with cracks emanating from holes. Computation results are compared with experiments.

Key words: fracture mechanics, crack growth, fatigue life, finite elements, mixed modes, crack growth trajectory.