Finite Element Simulations and Empirical Correlation for Charpy-V and Subsize Charpy Tests on an Unirradiated Low-Alloy RPV Ferritic Steel

Abstract

Charpy-V test results are widely used for the surveillance program of RPV (Reactor Pressure Vessel) embrittlement by neutron irradiation. Service life extension of nuclear power plants and more stringent safety requirements are increasing the request for small test specimens such as subsize Charpy. Furthermore, the empirical correlation formulas between conventional Charpy-V and fracture toughness are often questionable. Therefore, prior to use of reduced size specimens, different hypotheses have to be validated and this can only be achieved by combining tests and finite element simulations. The material of interest is a nuclear RPV low alloy ferritic steel 16MND5 (eq. A508 C13). Instrumented impact tests were performed on Charpy-V and subsize Charpy over a wide range of temperatures. The hyperbolic tangent curve from W. Oldfield [1] was fitted to the results. Then, correlation formulas are evaluated and commented. In a first step, the aim of the finite element simulations is to get a clear description of the global mechanical behavior of the specimens. A complete description of dynamic impact tests is not required for fracture mechanics purposes. A quasi-static simulation taking into account strain rate effect on the material response is sufficient. However, a 3D analysis is required even for cleavage failure mode. The second step is related to the transferability of fracture criteria. This task has been initiated at low temperatures using the Beremin cleavage model [2] and in the ductile regime using the Rousselier porous model [3]. The finite element results are compared to the experimental one. These results show good transferability potential.

Ductile to brittle transition of an A508 steel characterized by Charpy impact test

“…The present study uses a modified version of the model [22]. Another solution was proposed by Sainte-Catherine et al [58].…”

“…Such comparisons were carried out by other authors for steels similar to the material investigated in the present study [10][11][12][13]. Simulations of sub-size Charpy specimens were also proposed in [14] The material used in the present study is fully described in a companion paper [1]. This steel (A508 Cl.3) is used to manufacture the pressure vessel of French nuclear pressurized water reactors.…”

Finite element simulation of dynamic brittle fracture in pipeline steel: A XFEM-based cohesive zone approach

“…There are limited studies that focus on brittle fracture of CVN impact tests at low temperatures. For instance Catherine et al 13 have developed the Beremin (1983) cleavage model to simulate CVN and sub-size CVN impact tests at low temperature (À90 C). From their study they found that the results showed a good transferability potential.…”

Numerical simulation of dynamic brittle fracture of pipeline steel subjected to DWTT using XFEM-based cohesive segment technique

“…There are limited studies that focus on brittle fracture of the DWTT or Charpy V-Notch (CVN) impact tests at low temperatures. For instance Sainte Catherine et al [5] have developed the Beremin (1983) cleavage model to simulate CVN and Sub-Size CVN impact tests at low temperature (-90°C). From their study they found that the results showed a good transferability potential.…”