13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Effect of Levels of Residual Stress at Notch on Fatigue Crack Growth M. Benachour1,*, M. Dahaoui1, N. Benachour1,2, A. Cheikh1, M. Benguediab3 1 IS2M Laboratory, Department of Mechanical Engineering, Tlemcen University, Tlemcen 13000, Algeria 2 Faculty of Sciences, Physics Department, Tlemcen University, Tlemcen 13000, Algeria 3 LMSR, Department of Mechanical Engineering, Sidi Bel Abbes University, Sidi Bel Abbes 22000, Algeria * Corresponding author: bmf_12002@yahoo.fr Abstract In this paper, fatigue crack growth of finite plate with hole under constant amplitude loading through compressive residual stress at notch of aluminum alloys was investigated. Residual stress fields were generated by plastic deformation using finite element method. Based on fatigue crack growth rates (FCGRs) experimental data without residual stress, fatigue life and FCGR were predicted using AFGROW code. It was shown that the fatigue crack growth was affected by level of residual stress at notch for different level of plastic deformation. In this investigation, the presence of compressive residual stresses increase the total fatigue life and reduces the FCGRs. In addition stress ratio effect on fatigue behavior was studied. Keywords Fatigue crack, Compressive residual stress, Al-alloy, notch, stress ratio 1. Introduction Fatigue crack growth behavior is a significant issue in the establishment of inspection and maintenance procedures in variety industries such as aerospace, automotive, oil industries, rail...etc. This behavior is divided in three stages [1]: fatigue crack initiation, stable crack propagation and unstable crack propagation. Generally, mechanical components and structures contain geometrical discontinuities and notches. Stress concentration will be produced in theses discontinuities as a result of external force and depend of notch radius. The stresses are generally higher than the nominal values, and if precautions (good quality of machining of notch, induction of residual stress …etc.) are not taken into account, notches could be sites of crack initiation. Residual fatigue life of materials and structures depends on several parameters. In stable stage, fatigue life is linked strongly geometrical, loading parameters and residual stress. However, the stresses resulting from applied service loading are not the only stresses of significance for fatigue. Many components also contain residual stresses that were established prior to placing the component into service and which remain in place during the service life. These residual stresses are static load and influence the mean or maximum value of the load in each fatigue cycle. The residual stresses present diverse origin and several shapes [2-11] namely shot-penning, expansion of hole, overloads, underload, pre-strain or pre-deformation, welding, machining process… The stress field is beneficial if the stress is in compressive state [12, 15]. Contrary to this, the fatigue crack is accelerated [16]. Pre-strain is a process when preload induced plastic deformation, induced intentionally or not and create a residual stress field. The level and nature of these residual stresses depend on the amplitude and direction of applied load. In the investigation of Kamel et al. [17] effects of tensile and compressive residual stress in fracture mechanics specimens by the application of a mechanical pre-load were studied using ‘C’ shape specimen. Finite element analysis is performed to simulate the pre-loading and the subsequent fracture loading of the cracked specimen. Recently, effect of residual stress on the fatigue behavior
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