A Preliminary Geometrical Characterization of Surface Scratches on Aluminium Alloys Used in the Aerospace Industry

Abstract

Surface marks, such as scratches or cosmetic marks, commonly appear during the manufacturing phase of metallic components, because of the contact between tools and sharp edges with the surface of the parts. Scratches, depending on their width, depth, and root radius, cause a decrease in the fatigue life of metallic alloys. In particular, the presence of scratches with a size comparable to the grain size favors the generation of fatigue cracks in these features. In the aerospace industry, the presence of surface marks is a common cause of rejection. The low hardness of aluminium, a material widely employed in the manufacture of aerospace structures, contributes to the generation of surface marks. In this paper, a preliminary geometrical characterisation of scratches is established. It aims to define a set of parameters to characterise exhaustively the different scratches and to generate different behavior models for each type of scratch. Parameters such as scratch length, path radius, and burr height are considered in addition to the well-known parameters such as scratch depth, root radius, and open angle.