Specificity of crack initiation under equibiaxial fatigue: Development of a new experimental device

Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in-service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures. In some nuclear power plant components, the fatigue loading may be equibiaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data are available on austenitic stainless steels. It is essential to improve the fatigue assessment methodologies to take into account the potential equibiaxial fatigue damage. Hence this requires obtaining experimental data on the considered material with a equibiaxial strain tensor. This paper describes an experimental program on austenitic stainless steel carried out on the new experimental fatigue device FABIME2 developed in the LISN in collaboration with EDF and AREVA. This new device permits accurate quantification of the effects of equibiaxial strain state and structural parameters (such as mean stress) on the fatigue life. It also allows studying the complex possible combinations of potential detrimental effects as surface roughness, mean stress and equibiaxial loading. A Finite Element Modeling is performed in order to obtain a precise description of the strain state in the specimen. The results of the on-going test campaign will be presented.