Papers by Author: Mohamed Benguediab

Abstract: In this paper, effect of stress ratio was investigated on macro and micro of fatigue crack growth rates (FCGRs) of Al-alloy 2024 T351. Microscopic fatigue crack growth rate present a change of slope with respect to the macroscopic fatigue crack growth rate. In addition, an increasing in stress ratio increases the fatigue life. Fractographic examination showed the presence of striations in Paris domain and secondary cracks at grain boundaries.

Abstract: The crack propagation behavior in a 2024 T351 Aluminum Alloy under constant amplitude loading has been studied. This study is analyzed in term of crack opening load measurements using a compliance technique. The results obtained under constant amplitude fatigue tests show that different crack propagation stages can be identified. Significant effects due to load ratio changes have been quantified.

Abstract: In this investigation, variable amplitude loading effect was studied on aged hardening Al-alloys in series 2000 and 7000. Generalised Willenborg model was used in order to show loading interaction effects (overload effects). Variable amplitude loading under different form of spectrum has affected highly the fatigue life and fatigue crack growth rates. Fatigue lives were increased and fatigue crack growth rates (FCGRs) were decreased in increasing of overload ratio in single overload case. In application of overload band, the fatigue lives and FCGRs were affected by band overload and R-ratio of them when level in FCGRs was increased.

Abstract: The purpose of this paper is to estimate the number of cycles for fatigue crack initiation in notched plate under constant amplitude loading through tensile residual stress field of Aluminum alloy plate. Residual stress field was generated by plastic deformation using finite element method. Simulation of fatigue behavior was made on AFGROW code. It was shown that the fatigue crack initiation and propagation were affected by level of residual stress filed. In this investigation, the presence of tensile residual stresses reduces considerably the total fatigue life. Loading parameter namely stress ratio was studied. The decreasing in this parameter reduces the fatigue crack growth rate (FCGRs).

Abstract: Fatigue problems become an important topic in the maintenance of aircraft structures. Efficient repair technique, called composite patch repair, was used to reinforce the damaged structures and extend the service life. In this paper, using empirical approach, the effect of composite patch repair on fatigue crack growth was investigated on 7050 aluminum alloy. In additional, loading parameters associated with patch repair (Graphite/Epoxy) was studied in order to show their influence on fatigue life and fatigue crack growth rate, namely stress ratio. Results provide an increasing in fatigue life and fatigue crack growth rate in increased stress ratio. A delayed in fatigue life and diminution of FCGRs is the results of composite patch repair. Effect of patch repair was shown highly at high stress intensity factor when maximum applied loading is kept constant.