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Development of a regression model for the fatigue life assessment of open-hole specimens with double through the thickness cracks

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2019
Heidari Shabestari, Seyed Sohrab
This thesis mainly deals with the investigation of the fatigue crack growth characteristics of open rivet holes in aluminum 2024-T3 material. In this respect, most commonly observed type of cracks emanating from rivet holes, namely, double through the thickness edge cracks with centered configurations has been considered. Stress intensity factors and the fatigue lifes are calculated analytically and also with the Extended Finite Element Method (XFEM).Analytical calculations have been carried out using the conformal mapping technique whereas the extended finite element simulation for crack growth and determination of stress intensity factors are performed using a developed code for the desired cracks of interest in Ansys Parametric Design Language APDL. The objective of the analytical part of the study is to verify the calculated stress intensity factors using XFEM method. Nevertheless, XFEM results are also compared with results of AFGROW which is a Damage Tolerance Analysis (DTA) framework that allows users to analyze crack initiation, fatigue crack growth and fracture to predict the life of metallic structures. The effect of geometry in terms of initial crack length (c) and also radius (r) of the open rivet hole and the applied stress on the stress intensity factor and the fatigue life under constant amplitude loading has been studied. Finally, the statistical analysis is carried out using the Response Surface of experiments and Analysis of Variance (ANOVA) to investigate the effects of the parameters to fatigue life and a regression model to predict the fatigue life of open-hole specimens with double through the thickness cracks is developed.