Plastic Deformation of Rough Metallic Surfaces

A Tiwari,B N J Persson,A Almqvist

doi:10.1007/s11249-020-01368-9

A Tiwari, B N J Persson + Show 1 more

Open Access

https://doi.org/10.1007/s11249-020-01368-9

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Abstract

The contact between rough metallic bodies almost always involves plastic flow in the area of real contact. We performed indentation experiments on sandblasted aluminum surfaces to explore the plastic deformation of asperities and modeled the contact mechanics using the boundary element method, combined with a simple numerical procedure to take into account the plastic flow. The theory can quantitatively describe the modification of the roughness by the plastic flow. Since the long-wavelength roughness determines the fluid leakage of metallic seals in most cases, we predict that the leakage can be estimated based on the elastoplastic contact mechanics model employed here.

Highlights

The contact between metallic bodies occur in many applications [1, 2], and often the contact pressure is so high as to generate plastic deformation, at least at the asperity level [2,3,4,5,6,7,8,9,10,11,12]
The following points need to be taken into consideration: (a) The indentation hardness depends on the length scale
If we look at the indentation at low magnification we do not see any surface roughness and we would calculate the indentation hardness P = FN∕A0, where A0 = r02 is the projected contact area

Summary

Introduction

The contact between metallic bodies occur in many applications [1, 2], and often the contact pressure is so high as to generate plastic deformation, at least at the asperity level [2,3,4,5,6,7,8,9,10,11,12]. Because of surface roughness and the high elastic modulus of most metals, the contact pressure between asperities at short length scale can be very high even when the nominal contact pressure is low. Metallic seals are used in many applications involving very high fluid pressure differences, and in ultra high vacuum systems. Surface roughness and plastic flow highly affects leakage in metallic seals, since they are key factors in determining the surface separation in the non-contact area. For elastic solids like rubber, contact mechanics theories have been developed for how to predict the fluid leakage rate, and it has been shown that they are in good agreement

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