Measurement of wear on asperity level using image-processing techniques

A wear measurement technique based on the comparison of local surface heights has been developed. The method makes it possible to measure wear on asperity level. By comparing two roughness measurements before and after a wear experiment, the developed algorithms are used in a semi-online wear measurement system (an integration of a pin-on-disk and an interference microscope). The system consists of a controllable table with three degrees of freedom (in-plane motions x–y and a rotation θ), a white-light interference microscope (height and spatial resolutions of 1 nm and 1 μm, respectively) and a device for the generation of the wear track as well as for the friction measurements. The table is stopped before and after a certain number of rotations so that roughness measurements can be made with the white-light interference microscope on a certain spot. By using the developed image-processing algorithms, differences between the obtained successive surface images can give semi-online information about the amount of wear on asperity level. Wear results are correlated to the friction force data at that specific moment. With this approach a better understanding of wear phenomena is possible.