Representative Stress Correlation of Global Scratch Quantities at Scratch Testing: Experimental Verification

Evaluation and correlation of global quantities, i.e., normal and tangential hardness, at scratch testing in the context of a representative stress description was investigated. In particular, verification based on experimental results is at issue. It has been shown previously that within the framework of classical von Mises elasto-plasticity and quasi-static conditions, correlation can be achieved by using a combination of stresses at different levels of plastic strains to define representative quantities at scratching, accounting for the difference in mechanical behavior at elasto-plastic and rigid plastic scratching. However, verification from experimental results is required, which has been attempted in this study. Predictions based on previous theoretical results were compared with experimental findings for polymeric materials, as well as for different metals. Good agreement was found between the two sets of results, particularly so for the case of polymers modelled by von Mises elasto-plasticity. Accordingly, these results are of direct practical, accurate, and novel relevance for semi-crystalline polymers where viscoelastic effects are negligible.