Determination of an Objective Criterion for the Assessment of the Feasibility of an Instrumented Indentation Test on Rough Surfaces.

Julie Marteau,Abdeljalil Jourani,Maxence Bigerelle

doi:10.3390/ma13071589

Abstract

The influence of roughness on the results of indentation testing was investigated using a semianalytical model. This model used simulated surfaces that were described using three standard roughness parameters: the root-mean-square deviation Sq, the wavelength (or cut-off of Gaussian high-pass filter), and the fractal dimension. It was shown that Sq had the largest effect on the determination of the macrohardness, while the surface wavelength and fractal dimension had negligible effects at the scale of investigation. The error of determination of the macrohardness rose with the increase of the ratio Sq/hmax where hmax was the maximum indentation depth: Sq/hmax ratios lower than 0.02 were required to obtain a systematic error of the macrohardness lower than 5%, whatever the examined material mechanical properties (in elasticity and plasticity).

Highlights

Instrumented indentation testing is a widely used technique for the determination of mechanical properties
The aim of this paper is to provide an objective criterion for assessing the feasibility of an instrumented indentation test on rough surfaces
To assess the effect of roughness on the indentation curves and the resulting macrohardness, a semianalytical model of contact was applied on surfaces obtained with the Weierstrass function

Summary

Introduction

Instrumented indentation testing is a widely used technique for the determination of mechanical properties. Smooth surfaces are required to avoid the introduction of uncertainties in the determination of the contact area [1]. The need for smooth surfaces can be an issue for different reasons: (i) (ii). If the investigation of the material properties of a given component is required, surface preparation may not be wished for to avoid affecting the surface properties or to avoid deteriorating the component. It is impossible to have a surface free of any roughness: whatever the surface preparation, there is always residual roughness that may impact the very small scales. The impact of roughness on the indentation results was investigated by several authors. Walter et al [2] used finite element simulation to examine the influence of roughness on the scattering of indentation curves and on the computation of Young’s modulus using the Oliver–Pharr method [3]

Objectives

Methods

Results