The structural components of the nuclear industry are submitted to a number of aggressions, Mechanical, chemical and physical (irradiation). As a consequence, the problem of durability and ageing of such structures is a key issue. The understanding of the phenomena involved implies the description and modelling of atomic scale events (irradiation point defects) resulting in fluxes of matter (diffusion under irradiation), in the dynamic evolution of structural defects (dislocation loops, cavities,...), with major consequences on mechanical properties (yield stress, fracture behaviour), with, in addition, phenomena coupled between mechanical behaviour and chemical environment. It is therefore the totality of materials science which is involved in understanding the behaviour of metallic structural materials in the nuclear environment. The aim of the present paper is to illustrate some examples currently under investigation, and some of the new approaches involved in the understanding of mechanical behaviour (a scale transition from the atomic to the macroscopic). The input from large computer simulations as well as the value of simple 'back of the envelope' calculations, plus the need for cautious experimental studies will be illustrated. The theme of the ageing of materials, central to this paper, finds applications in many industrial situations.
- Mechanical properties