Fractal Characterization of Brass Corrosion in Cavitation Field in Seawater

Abstract

Cavitation is a physical process that produces complex effects on the machines and components working in conditions where it acts. One effect is the materials-mass loss by corrosion–erosion when components are introduced into fluids under cavitation. The analysis of the damages produced by cavitation is generally performed by using different destructive and non-destructive experimental techniques. Most studies on materials’ behavior in cavitation refer to the erosion–corrosion mechanism, and very few investigate the fissure propagation by fractal methods. None have investigated the fractal characteristics of the sample surface after erosion–corrosion or the multifractal characteristics of materials’ mass variation in time in a cavitation field. Therefore, this research proposes a computational approach to determine the pattern of materials’ damages produced by ultrasound cavitation. The studied material is a brass, introduced in seawater. Fractal and multifractal techniques are applied to the series of the absolute mass loss per surface and the sample’s micrography after corrosion. Such an approach has not been utilized for such a material in similar experimental conditions. This study emphasizes that the box dimension of the series of the absolute mass loss per surface is close to one, and its behaviour is close to a non-/monofractal. It is demonstrated that the material’s surface corrosion is not uniform, and its multifractal character is highlighted by the f(α)− spectrum and the multifractal dimensions, which have the following values: the capacity dimension = 1.5969, the information dimension = 1.49836, and the correlation dimension = 1.4670.

Fractal Characterization of the Mass Loss of Bronze by Erosion–Corrosion in Seawater

“…Comparisons of the previous results with those drawn from the analysis of a brass sample [ 41 ] subjected to the same conditions indicate that: The fractal dimensions of all series do not significantly differ. The lowest capacity dimension corresponds to the brass series − = 1.22.…”

“…Still, these studies have been performed using a smaller number of tools, among which are R/S rescaled analysis and MFDFA [ 50 ]. Extended analyses on the mass loss of copper alloys have not been performed using both fractal and multifractal methods, even if the mass loss in time of copper alloys has not been studied in terms of its relationship with image analysis [ 41 ]. The current study and [ 41 ] represent a departure point for the fractal analysis of these materials’ behavior in a cavitation field in seawater by fractal and multifractal approaches.…”

“…Spatial data were used in [ 39 ] to investigate the roughness of metal samples. Fractal and multifractal analysis were performed to investigate the results of corrosion or corrosion–erosion of steel and copper alloys [ 37 , 40 , 41 , 42 , 43 , 44 ].…”

“…Despite investigations of the mass loss of copper-based alloys having been performed [ 18 , 41 , 42 , 43 ] and the existence of multifractality applications in engineering, combined investigation (exploring the corroded surfaces of materials in an ultrasonic cavitation field) has been less reported [ 41 ]. Therefore, in this article, we continue the investigation from [ 8 , 41 , 42 , 43 ], aiming to determine the pattern of the mass loss of copper-based alloys from the viewpoint of fractal/multifractal theory. The goal is to check the hypothesis that the fractal/multifractal measures significantly differ for the two materials and compare the results with those obtained for a brass [ 41 ].…”

“…Therefore, in this article, we continue the investigation from [ 8 , 41 , 42 , 43 ], aiming to determine the pattern of the mass loss of copper-based alloys from the viewpoint of fractal/multifractal theory. The goal is to check the hypothesis that the fractal/multifractal measures significantly differ for the two materials and compare the results with those obtained for a brass [ 41 ]. Accepting the above hypothesis will open up a new way to use this technique to distinguish between two classes of materials.…”