Modelling of the Charpy test as a basis for toughness evaluation

Abstract

Micro-mechanical material models are applied for the evaluation of fracture toughness properties from results of instrumented Charpy tests. In the first example the ductile fracture resistance of a weld material from the irradiation surveillance of a nuclear pressure vessel is determined. The initiation values were converted into pseudo plane strain fracture toughness values and used to adjust the ASME reference fracture toughness curve. The second example summarises modelling efforts towards the description of the cleavage-to-ductile transition region of a ferritic steel. Here, the Beremin model revealed substantial deficiencies concerning the transferability of the results between different specimen types and temperatures. Modifications of the failure models considering the failure mechanisms observed seem to improve the situation. In order to give some additional insight into stress and strain fields in Charpy and fracture mechanics specimens, preliminary results of a study with irradiated weld material will be presented. This study aims at the assessment of upper shelf toughness curves, however the existing numerical models are also applicable for the determination of the stress and strain fields in Charpy specimens tested in the transition temperature regime.