Analysis of Fracture Mechanics Specimens Made of Inconel 600 Based on Assessment Methods of Different Complexity

Fracture mechanics analysis plays an important role in the frame of the safety assessment of nuclear components. Usually the goal of such an analysis is to decide if a given flaw size in the piping (or any component of the primary circuit) is acceptable or not. The word “acceptable” means that structural integrity of the component is guaranteed with sufficient safety margins up to the end of service life or up to the next in-service inspection (considering the worst case loads and lower bound material properties). To fulfil this high-responsible task in practice some useful Engineering Assessment methods (EAM) have been established i.e. Local flow stress concept (Germany), assessment based on J-Integral (France RSE-M), Limit load calculation according to (ASME XI, USA) or Two criteria approach (R6, UK). These EAM are verified by a large number of testscarried out in the past. On a higher level, more advanced assessment methods have been developed during the last years, based on micromechanical models of void nucleation and growth. These advanced micromechanical models are used within the Finite Element Analysis (FEA) and allow to study the whole crack growth process from initiation to final failure in more detail. In the ductile regime, which is the typical case for application of aforementioned methods, the crack growth can be divided into three phases: crack initiation, stable crack growth and unstable crack growth. In this paper methods of different complexity will be applied to analyse fracture mechanics specimens made of Inconel 600. Special focus will be placed on the crack growth modelling based on the Gurson’s porous metal plasticity theory. All performed calculations will be compared with experiments.