The Young's modulus (E) of steels varies with their chemical composition, the manufacturing conditions of the products, the orientation ot the test samples within a given sheet. The knowledge of its exact value is important for the optimum choice of the steel grade best suited for the production of structural parts. Several methods are available for the determination of the modulus of elasticity. At LEDEPP, a tension test method is used, but it is considered that a method based on the measurement of the resonance frequency should be advantageous. As it is a non-destructive method, various research directions can be explored, like the variation of E with orientation, temperature or prestrain. Both methods are described and their results compared.

The superelastic behaviour of shape memory alloys is now successfully modelled. On the other hand, the anisothermal creep is badly described, both by phenomenological models and by micro-macro formulations. In this paper we introduce a new approach, based on the concept of group of variants to more precisely describe the microstructure obtained during stress assisted two way memory. A new variants selection criterion is proposed.

A technique, which allows characterizing the local strain field over a domain representative of the microstructure of a heterogeneous material, is described. It is based on scanning electron microscopy, microelectrolithography, image analysis and in situ mechanical tests. On one hand, in relation with a microstructure analysis, it allows characterizing the different mechanisms responsible for the plasticity or the damage of materials. On the other hand, a quantitative analysis allows comparing and validating from a local to a global scale, the different models used for the prediction of materials constitutive laws. Finally, the knowledge of the experimental displacement improves seriously the results of finite element computations, by a better determination of the boundary conditions.

A quantitative method is described for the measurememnt of displacements and strains by high-resolution electron microscopy. The image is considered to be composed of periodic sets characterized by Fourier analysis. The local amplitude and geometric phase of lattice fringes can be determined in this way. The analysis of the phase distribution leads to the determination of the local lattice configuration. The method is illustrated by different examples and its application conditions are discussed.

Artefacts of World War I were studied to better understand iron corrosion phenomena in clay soils. The identification of their two corrosion layers by Raman spectroscopy highlighted iron oxides and oxy-hydroxides. Electrochemical experiments confirmed the porosity of the external layer, and the protective role of the internal products. The influence of the burial environment on the corrosion rate was also proved.