Effect of thermal ageing of CF8M on multi-axial ductility and application to fracture toughness prediction

This paper proposes a method to predict the thermal ageing effect on fracture toughness of CF8M cast stainless steel. The proposed method is based on multi-axial fracture strain combined with finite element damage analysis to simulate ductile tearing. Multi-axial fracture strain loci of un-aged and aged CF8M are determined by analyzing notched bar tensile test. It is shown that the thermal ageing effect on multi-axial fracture strain loci can be characterized by one constant. It is further shown that J-resistance curves of un-aged and aged CF8M can be predicted well from finite element damage analysis using multi-axial fracture strain loci. Implication of present results to practical application of crack assessment of aged cast stainless steels is discussed.