Thermo-mechanical tests combining thermal, mechanical and physical measurements

Abstract : Numerical models of many forming processes of metals rely on description of rheological characterization of the metallic alloys, which can turn very difficult at high temperature. In this work, a direct resistance heating machine (Taboo) has been developed to perform cyclic loadings at very low strain rates (10-3 and 10-4 s-1) between 900°C and the solidus temperature. We fir st describe the experimental setup; then we present several measurement techniques. A specificity of resistance heating machines is to deal with non negligible temperature gradients around the center of the sample which induce heterogeneous strains. To measure displacements, a specific set-up has been constructed using speckle correlation. It has several advantages like full field and non destructive displacement measurement. Thanks to this method we obtain full field measurements. Electric current and resistivity measurements are also performed all along the heating/cooling and deformation stages. They can be correlated to phase transformation. Finally, we describe a numerical model for simulating and analysing the tests with a combined electrical, thermal and mechanical model. The main goal is to help designing optimal sample geometry using to identify mechanical parameters by inverse analysis.