ABSTRACT
The Charpy impact test is a widely accepted method for the measurement of material’s fracture toughness and facilitates the investigation on the temperature related ductile-brittle transition phenomena. In order to study the structural steel behavior under different conditions such as the effect of pre-strains and the residual stresses etc., the experimental procedure of impact test becomes laborious and expensive. The ability to reproduce experimental results analytically from a limited set of material parameters may reduce the cost and allow assessment of the various behaviors of target steel from few tested samples. In this study, efforts were made to simulate the Charpy impact test to measure the brittleness of steel based on the modified Weibull stress (MWS). To deal with strong non-linearity and reproduction of elasto-plastic deformation phenomena under impact, an explicit-dynamic analysis was performed employing penalty contact method. The fracture occurrence probability at different temperatures was evaluated based on MWS, while internal energy from the analysis was decided at 95% fracture probability. The ductile-brittle transition temperature (DBTT) was estimated from the ductile-brittle transition curve for two Japanese structural steels i.e., SM570Q and SM490YB. To validate the analytical results, laboratory experiments were performed under similar conditions. The internal energy from MWS calculations was compared with the experimental absorbed energy from the Charpy impact tests. It was found that the analytical values and the experimental values are in good agreement in the low-temperature region where brittle fracture dominates. Based on the outcomes of this study, it was concluded that MWS calculations can be applied to evaluate the brittle fracture occurrence during Charpy impact tests.
