Effect of end milling, grinding and tartaric-sulfuric anodizing on the fatigue behavior of AA7050 alloy

The present study investigates the effect of the high-speed milling (HSM), grinding and anodizing processes on the high cycle fatigue strength of the AA7050 aluminum alloy. These processes are systematically applied to certain aircraft components as specified by aeronautical standards, to attain a good surface finish. In order to understand the effect of each process on the fatigue strength, a vast experimental campaign consisting of fully reversed plane bending fatigue tests has been conducted on specimens with different surface states. A polished batch, three milled batches with different surface roughness, a grinded batch and two milled then anodized batches with different surface roughness have been tested. The results show that the roughness must be highly degraded (Sa > 3 μm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu m$$\end{document}) in order to impact the fatigue strength. It is also shown that anodizing has slight beneficial effect on the fatigue strength in the high cycle fatigue domain studied. The experimental results show a dependence of the fatigue strength on the surface roughness via the parameter Sa\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sqrt{Sa}$$\end{document}, previously proposed by the authors.