Amélioration de la robustesse de la technique de caractérisation mécanique des matériaux métalliques par indentation sphérique instrumentée

This thesis focuses on the development of a method for mechanically characterizing metallic materials based on an indentation curve linking the force and penetration of a quasi-spherical indenter. An initial experimental study established the most suitable test protocol for industrial materials. Simulations with a rigid spherical indenter were then used to build a limited but quick-to-generate digital database. An original method for transforming the curves was developed to convert from a rigid indenter to a deformable, non-spherical indenter. Validated numerically, this method makes it possible to quickly build an indentation database for a deformable monobloc indenter with a radius close to 0.5 mm, which is then used for characterization. The proposed characterization method combines inverse analysis using a simplex algorithm and exploitation of this numerical basis. To enhance robustness against experimental noise, representative deformations are extracted: calculated at different levels of indentation from the Hessian matrix of residuals, the associated stresses are deduced from Hollomon's law, generating several representative points. In addition, various strategies for matching experimental and numerical curves make it possible to increase the number of points on the work hardening law.Finally, numerical and experimental validation shows a good correlation between the mechanical parameters obtained from indentation and those from tensile tests, with particularly high accuracy for tensile strength.