A predictive fatigue life model for anodized 7050 aluminium alloy |
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| Affiliation: | 1. Université de Toulouse; INSA, UPS, EMAC, ISAE; ICA (Institut Clément Ader), 10 Av. Edouard Belin, 31055 Toulouse Cedex 4, France;2. Université de Toulouse; INSA, UPS, EMAC, ISAE; ICA (Institut Clément Ader), Route de Tiellet, 81000 Albi, France;1. Department of Mechanical Engineering, Faculty of Technology, University of Brasília, Brazil;2. Federal Institute of Brasília, Brasília, Brazil;1. CEEMPRE, Department of Mechanical Engineering, University of Coimbra, Rua Luís Reis Santos, Pinhal de Marrocos, 3030-788 Coimbra, Portugal;2. Department of Mechanical Engineering, Coimbra Polytechnic – ISEC, Rua Pedro Nunes, Quinta da Nora, 3030-199 Coimbra, Portugal;3. State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031, China;4. State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China;1. 2354 Fairchild Dr., Suite 2J2A, USAF Academy, CO 80840, USA;2. 3290 Hamal Circle, Monument, CO 80132, USA |
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| Abstract: | The objective of this study is to predict fatigue life of anodized 7050 aluminum alloy specimens. In the case of anodized 7050-T7451 alloy, fractographic observations of fatigue tested specimens showed that pickling pits were the predominant sites for crack nucleation and subsequent failure. It has been shown that fatigue failure was favored by the presence of multiple cracks. From these experimental results, a fatigue life predictive model has been developed including multi-site crack consideration, coalescence between neighboring cracks, a short crack growth stage and a long crack propagation stage. In this model, all pickling pits are considered as potential initial flaws from which short cracks could nucleate if stress conditions allow. This model is built from experimental topography measurements of pickled surfaces which allowed to detect the pits and to characterize their sizes (depth, length, width). From depth crack propagation point of view, the pickling pits are considered as stress concentrator during the only short crack growth stage. From surface crack propagation point of view, machining roughness is equally considered as stress concentrator and its influence is taken into account during the all propagation stage. The predictive model results have been compared to experimental fatigue data obtained for anodized 7050-T7451 specimens. Predictions and experimental results are in good agreement. |
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