National Research Council of Canada. NRC Institute for Aerospace Research
Life prediction; HOLSIP; Short crack; FEM; Fractography; 7050
This paper presents the results of a fatigue analysis of a CF-18 aft wing fold shear-tie lug, which involved multiple crack nucleation sites and short crack growth under complex geometry and loading conditions. A three-dimensional (3D) finite element model was developed to simulate the loading applied in the shear-tie lug test and determine the local stress/strain distribution. Short crack data and the subsequent material model, were specifically developed for the lug material (7050-T7452 forging), in which work the Holistic Structural Integrity Process (HOLSIP) approach was used to correlate the short crack model with material microstructural features, such as constituent particles and porosities. After the shear-tie lug fatigue test, quantitative fractography (QF) was carried out to measure the crack growth size. Based on the failure mechanisms, a simplified single crack model was proposed to analyze this multiple crack growth problem, and the life estimation compared well with the test results.