On the Identification of Critical Damage Mechanisms Parameters to Predict the Behavior of Charpy Specimens on the Upper Shelf

Abstract

Abstract The use of sub-sized Charpy-V specimens to monitor the mechanical properties of reactor pressure vessel (RPV) steels is receiving increasing attention. It is motivated by the fact that a smaller amount of material can be used to obtain the fracture properties, which can be of great economical interest when dealing with activated materials. Prior to use reduced-size specimens, investigations are still necessary to verify that the properties obtained from sub-sized specimens are comparable to those obtained from standard size specimens. Amongst the approaches that are available, the local approach to failure, which combines a description of the material microstructure (void density, distance between inclusions…) and empirical observations, is a promising way to investigate the transferability of mechanical properties. It has been successfully used to describe the macroscopic behavior of a wide range of cracked or notched specimens and components of various dimensions but restricted so far to quasi-static loading conditions. The results discussed in the paper are focused on the upper shelf behavior of the French RPV material, equivalent to the American ASTM A508 Cl.3 material. Modeling of the material is achieved using the Rousselier coupled damage constitutive equations. This model is implemented in CAST3M, a general-purpose finite element code developed by the French Atomic Energy Agency. Comparisons between the numerical results and the experimental observations are given and the computed local temperature elevations and plastic strain rates discussed to explain the behavior of the specimens.