Imaging strategies and their effectiveness for wear analysis of polymer-steel pairs


In tribological investigations substantial developments were made in acquiring precise friction and wear data at micron scale (microNewton and microMeter). Such data are generated by automated new sensors, complemented by efficient data processing. Nevertheless, in tribography the interpretation of wear mechanism and characterization from surface scar observation are still rather subjective. This can be attributed to the gap between image data acquisition and its processing methods. In the present research, attempts were made to effectively use imaging techniques and the micrographs image characteristics to analyze worn surfaces. In this regard, polymer composites were tested against steel counter face material in rolling/sliding contact. A low cost imaging technique of reflected light microscopy has been used. Sequential micrographs (ex-situ) for wear analysis were acquired using relocation micrography. Two different illumination strategies were followed to understand their influence on surface image interpretation. Image data such as texture (surface scars) and image properties (histogram and energy score) were estimated to quantify and understand the wear process. The sequential image data were compared with roughness measurements and coefficient of friction values. Comparable micrographs between the sequences were realized through relocation micrography and image registration where the region of interest is located at a micron scale. Amongst the different image characteristics, the energy score from the grey-level co-occurrence matrix (GLCM) provides most representative results concerning changes in surface characteristics and in friction behaviour. The results of energy score clearly suggest that the GLCM can be used to track the change incurred on the worn surface for both polymer and steel surfaces. Moreover, the dynamic nature in the formation of a polymer transfer layer on the steel surface is understood from calculated energy score (GLCM). The presence of a thin film on the polymer surface also suggests a readhesion mechanisms of worn polymer debris or a back transfer the steel surface. On the whole it is evident that potential research is required for surface investigation practices.

10th Arnold Tross Kolloquium, 2014