Methodology for wear mapping error quantification

Abstract

Purpose The purpose of this paper is to propose a methodology to quantify the error on wear volume evaluation using optical interferometry with image analysis (OI+IA), to establish a lower threshold for wear mapping in practical applications. Design/methodology/approach A three-dimensional surface wear map is quantified by measuring the same area of a surface before and after a wear process using optical interferometry. Then, by subtracting the matching images, the wear map (volume of wear) is obtained. To access the error related to wear mapping, the difference between several consecutive measurements of the same unworn surface was performed and deeply investigated. Findings The paper shows that the difference between two consecutive measurements of the same unworn surface, which ideally should be zero, is not. Thus, the magnitude of this “wear map” is the error. The main causes of such uncertainties are because of sample motion in a subpixel scale; a combination between surface roughness with the selected resolution; and numerical errors on the relocation process that is used to match the surfaces before subtracting them. Practical implications The proposed methodology allows one to define the lower threshold for wear map analysis using OI+IA. To know the limitation of OI+IA for wear mapping prevents misevaluation of the so-called almost-zero-wear. Originality/value This paper covers and identifies main uncertainties and numerical errors related to optical interferometry assisted by image analysis for wear mapping. Several other papers deal with uncertainties of OI; however, this paper proposes a simple methodology to evaluate the lower threshold for wear mapping. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0354