1. Experimental and Theoretical Approaches to Elementary Phenomena

The experimental approach to the fundamental phenomena governing the material's response to abrasive grains at the microscopic scale is based on scratch tests. We first present the principle and main applications of these tests. We then summarize the results obtained for ductile materials before reviewing current theoretical models and interpretations, which also help clarify various important aspects. Finally, we discuss the case of brittle and semi-brittle materials.