Seminar : Guillaume Kermouche

Surface manufacturing processes - such as machining, shot peening, burnishing, polishing … - are known for their consequences on surface integrity. They are mostly triggered by repeated and intense contact loadings leading to large plastic deformation, high strain strain rate and high temperature rise in the near-surface. A significant in-depth gradient of mechanical properties is usually observed over 10 to 100 µm depending on the process.

This gradient is a consequence of near-surface materials transformation and can play on materials performance (fatigue, stress-corrosion, wear). The accurate characterization of the mechanical properties of these new materials at the right scale is therefore of primary importance. It can be made through the use of suitable methodologies based on nanomechanical testing –i.e. micropillar compression, nanoindentation. The nanomechanical testing field is actually reaching a maturity level that allows its deployment to materials transformation induced by surface manufacturing processes.

The first part of this presentation will be dedicated to a brief review of the last developments in the nanomechanical testing field, with a special focus on high temperature, high strain rate and fatigue testing. The second part will deal with the application of nanomechanical testing to investigate consequences induced by manufacturing processes. More specifically, various cases ranging from severe shot peening to sliding friction contacts are investigated. The last part of this presentation will focus on a new high-temperature nanoindentation procedure, the High Temperature Scanning Indentation (HTSI) method, developed on purpose to investigate the thermal stability of these surface-processed materials.