Fatigue life estimation of structures with cracks using the finite element method

11 ABSTRACT Master of Science Thesis FATIGUE LIFE ESTIMATION OF STRUCTURES WITH CRACKS USING THE FINITE ELEMENT METHOD TOLGA BAKLACIO?LU Anadolu University Graduate School of Sciences Civil Aviation Program Supervisor: Assist. Prof. Dr. Dilek TURAN 2005, 143 pages In this thesis, using finite elemet method fatigue life predictions of structures containing cracks were made. Effect of different stress values and crack lengths on fatigue life was investigated. Firstly, a 2024-T3 Aluminium alloy plate which is a fatigue experiment tool was modelled in 2-D for two different conditions of existence of precracks of different lengths using ANSYS 5.5 software. By selecting different crack increments, fatigue analysis of this plate subjected to two different tensile stress values was done and fatigue life predictions were made. Then, a geometry which consists of cracks nucleating around two notches of a 2024-T3 Aluminium alloy lap joint found on an aircraft wing surface was modelled in 2-D using ANSYS software and fatigue analysis of the lap joint subjected to a typical stress value obtained from the wing load distribution of a C-15 aircraft during flight was done and its fatigue life prediction was made. The variation of stress intensity factor and the number of cycles values with increasing crack length were plotted. Keywords: Fatigue, crack propagation, finite element method, ANSYS, fatigue life prediction