ELASTIC PROPERTIES DETERMINATION FROM INDENTATION TESTS

The knowledge of mechanical properties, and elastic modulus in particu lar, is necessary for a good understanding of the behaviour of materia ls subjected to static or dynamic loading. Accurate determination of e lastic modulus is possible in the case of massive and homogeneous mate rials. For coatings the problem is more complicated but this determina tion is rendered possible using load and displacement sensing indentat ion tests or ultrasonic wave tests, for example. The purpose of this s tudy is to determine elastic modulus of materials and specially that o f coatings by analysing the morphology of indents obtained by the Vick ers hardness test. During the withdrawal of the indenter, distortions of the faces of the indent are directly linked to the elastic properti es of the material. Comparison between the true volume of the deformed indent and the ideal volume of the Vickers pyramid allows one, starti ng with Bulychev's relation, to achieve good estimations of the elasti c modulus of massive materials as well as that of coatings. The model is first tested on massive material of known elastic properties (middl e carbon steel, ferritic stainless steel and aluminium alloy), then it is applied to a chromium carbide coating obtained by hypersonic therm al spraying. Calculated elastic moduli are in accordance with literatu re data, except for the aluminium alloy, for which plastic how around the indent is different from the other materials.