Fracture toughness prediction of hydrogen-embrittled materials using small punch test data in Hydrogen

Abstract

In this paper, we propose a numerical methodology to predict the effect of hydrogen concentration on fracture toughness by using small punch (SP) test data in hydrogen. The proposed method performs finite element (FE) damage analysis, with the multi-axial fracture strain damage model based on. First, a damage model is derived from the tensile and fracture toughness test data obtained in air. Then, by simulating the SP test in hydrogen, the hydrogen-embrittlement constant is determined. Finally, fracture toughness of hydrogen-embrittled material is predicted using the determined damage model and hydrogen-embrittlement constant. To validate the proposed methodology, published test data of API X70 steel in hydrogen and air (or nitrogen) atmosphere are used. In terms of hydrogen concentration, the predicted fracture toughness agrees well with the fracture toughness test data obtained in hydrogen environment.