Apport des techniques sclérométriques à la caractérisation des ...

ABSTRACTAn understanding of abrasion resistance and the associatedsurface deformation mechanisms is of primary importance in thematerials engineering and design of many important industrialcomponents undergoing wear and abrasion. Instrumented scratchtesting has been shown to be a useful tool for characterization of theabrasion resistance of materials.Our fundamental work on the scratch tester development foundtwo main applications, focused on elasto-plastic deformation andfracture mechanisms during a scratch test.i - Although most studies on scratch resistance have been liniitedto the theoretical case of purely plastic materials, experiments onmetals and polymers have shown that the contact mechanics andindentation behavior are strongly influenced by the elastic behavior.In this work, the measurement of the normal and tangentialscratch forces, the penetration depth relative to the initial surface andthe three-dimensional topographic relief of the scratched surface aredone. They have allowed us to acurately calculate the actual contactarea between the indenter and the material, taking into account bothelastic deformation and pile up phenomena. This contact surface wasused to estimate the real mean contact pressure during scratchtesting. This pressure was compared to the static hardness of thestudied materials, as well as to the classical definitions of the scratchhardness. The ratio between the plastic and elastic deformationduring a scratch test with a Berkovich indenter was then related tothe ratio of the elastic modulus over the hardness for the tested bulkmaterials.This study was performed on a wide range of ductile materialsfrom polymers to metals and demonstrates the importance of takingboth elastic and pile-up phenomena into account in order toaccurately understand and characterize the scratch resistance ofmaterials.2 - Ceramic materials are used in a large range of mechanical andelectronic devices. But these materials are still limited in their