Surface roughness

Summary

Surface roughness can be regarded as the quality of a surface of not being smooth and it is hence linked to human (haptic) perception of the surface texture. From a mathematical perspective it is related to the spatial variability structure of surfaces, and inherently it is a multiscale property. It has different interpretations and definitions depending from the disciplines considered. In surface metrology Surface roughness, often shortened to roughness, is a component of surface finish (surface texture). It is quantified by the deviations in the direction of the normal vector of a real surface from its ideal form. If these deviations are large, the surface is rough; if they are small, the surface is smooth. In surface metrology, roughness is typically considered to be the high-frequency, short-wavelength component of a measured surface. However, in practice it is often necessary to know both the amplitude and frequency to ensure that a surface is fit for a purpose. Ro

Official source

https://en.wikipedia.org/wiki/Surface_roughness

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Characterization of the surface roughness of 3d objects from micro CT

David Delévaux

2020

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Laser polishing (LP) is a process that allows a significant reduction of the surface roughness of a metal workpiece via re-melting a shallow layer of material. However, the practical use of LP is limited due to the difficulty of satisfying the high surface polishing quality for industries such as jewelry. Hence, this study presents a thermal model based on the Chernoff formula for fixed and moving LP processes. The model was validated via a sensitivity analysis of the coefficient of absorption of the solid and liquid phase and through comparing the results with the corresponding experimental observations of the melt pools produced. In this investigation, a continuous wave, high power diode laser (980 nm wavelength, o 0.9 mm spot size with a flat top distribution) was coupled to a fixed focusing head. The material was a hardened tool steel (X38CrMVo5-1 steel-1.2343) with an initial surface state obtained by electrical discharge machining (EDM) of CH30 on the Charmilles scale for EDM, which corresponds to a roughness Ra of 3.15 mu m. The results show that the model is able to represent the thermal behavior of the tool steel during LP. The best results are obtained with two constant coefficients, one for the solid based on the measurement at room temperature (a(s) = 35%) and one for the liquid fixed so that the model fits the experiment data (a(l) = 25%).

MDPI2022

Variational phase-ﬁeld study of adhesive wear: elastic and elastic-plastic models

Sylvain Collet

Wear is well known for causing material loss in a sliding interface. Available macroscopic approaches are bound to empirical ﬁtting parameters. We propose a study of the physical processes that lead to wear at the scale of the surface roughness, where adhesive junctions are formed between the asperities on the surface of the materials. Using a brittle formulation of the variational phase-ﬁeld approach to fracture, we demonstrate that the failure mechanism of an adhesive junction can be linked to its geometry. By imposing speciﬁc couplings between the damage and the elastic energy, we further investigate the triggering processes underlying each failure mechanism. We show that a large debris formation is mostly triggered by tensile stresses while shear stresses are dominating the mechanisms leading to small or no particle formation. The interaction of two neighboring junctions is analyzed and shows that macro-particles which embody the two junctions can be formed under certain conditions. A ductile phase-ﬁeld formulation permits us to assess the effect of the material’s ductility on the failure mechanism of adhesive junctions. We observe that the formation of large particle becomes less likely to happen as the ductility of the material increases.

2020