Computation and Experimental Investigations of Notched Components Fatigue Life Estimation

Abstract

This work considers the analytical methods and procedures for obtaining the stress intensity factors and for predicting the fatigue crack growth life for cracks in notched structural components. Many failures in aircraft structures are due to fatigue cracks initiating and developing from fastener holes at which there is large stress concentration. Stress intensity factor (SIF) solutions are required for fracture strength and residual fatigue life assessment for defects in structures, or for damage tolerance analysis [1] recommended to be performed at the stage of aerospace structure design. Many efforts have been made during the past two decade to evaluate the stress intensity factor for corner cracks and for through-the-thickness cracks emanating from fastener holes. A variety of methods have been used to estimate the SIF values, such as approximate analytical analysis, finite element (FE), finite element alternating, weight function, photoelasticity and fatigue tests. In this paper the analytic methods and procedures for obtaining the SIF and predicting the fatigue crack growth life for cracks at attachment lugs. Single through crack and single corner cracks in the attachment lug analysis are considered. For this purpose analytic expressions [2] are evaluated for SIF of cracked lug structures. For validation of the analytic stress intensity factors FEM with 3D cracked finite elements is used. Typical finite element model of cracked lug is presented in Fig. 1.