PWR Effect on Crack Initiation Under Equi-biaxial LoadingFirst tests with a particular fatigue device

As many countries are now working to extend the life of their existing power plants, a thorough inventory of the various effects that could potentially represent a hazard to a safe long term operation is necessary. These structures, often of large dimensions, are subjected during their life to complex loading combining varying mechanical loads, multiaxial, with non-zero mean values associated with temperature fluctuations and also PWR environment. Before applying the concepts and methods observed on uniaxial analytical specimens, it is necessary to consolidate the implementation of tests on almost structures.In the framework of upgrading the fatigue design rules (RCC-M, RCC-MRx), the uniaxial reference fatigue curve was altered by taking into account effects like Multiaxiality, Mean stress or strain, Surface roughness (polished or ground), Scale effect, Loading History. In addition to this effect, Environmentally Assisted Fatigue is also receiving nowadays an increased level of attention.To formally integrate these effects, and to obtain fatigue data under structural loading, biaxial test means with and without PWR environment were developed at LISN. Two kinds of fatigue device have been developed. Within the same specimen geometry, structural loads can be applied in varying only the PWR environment. The first device (FABIME2) is devoted to study the effect of biaxiality and mean strain/stress on the fatigue life. A second and new device based on FABIME2 is for the study of the impact of the environmental effect. With these new experimental results, we will highlight a PWR effect on the fatigue life of stainless austenitic steels.