Abstract
The main objective of this PhD thesis is to establish an energy balance at the grain scale in order to assess the thermomechanical consistency of material models used to predict the development of crystal plasticity of metals.The first part of this work consists in setting a protocol allowing the material elaboration with the desired microstructure which is to be compatible with the use of classical macroscopic observation devices. The obtained coarse-grained aluminum samples (with centimeter grains) are used in cyclic tensile tests. During these tests, the kinematic and thermal fields are recorded with Digital Image Correlation and Infra-Red Thermography techniques.Two specific imaging techniques were developed. They allow introducing ad hoc hypotheses (i.e. consistent with microstructure) on the kinematic and the thermal fields. In this work, these hypotheses consist in intra-granular continuity conditions on the displacement, temperature and heat flux fields. These methods give independent measures on each grain while improving the robustness of the measurement methods. These methods were numerically validated using computer-generated images heterogeneously loaded.Cyclic tests were finally performed on the processed aluminum multi-crystals. The developed methods allowed the observation of the development of intra-granular plasticity and the development of inter-granular cracking.