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.

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A B S T R A C T This paper reports steady-state stress distributions within the weld metal in a welded branch component, via detailed three-dimensional elastic-creep finite element analyses. The creep exponent and constants for the base and weld metal are systematically varied to simulate under-matching, even-matching and over-matching conditions in creep. Various loading conditions are also considered to see the effect of the loading mode. It is found that the mismatch effect in creep on steady-state stresses within the weld metal can be uniquely quantified by the mismatch factor, defined as a function of creep exponent and constant. Ratios of section-averaged (effective and maximum principal) stresses for the mismatched case to those for the even-matched case are linearly dependent on the mismatch factor. A = creep constant, see Eq. (2) E = Young's modulus MF = mismatch factor, see Eq. (1) or Eq. (3) n = creep exponent P = generalized load P L = limit load t = time t red = redistribution time, see Eq. (4) ε = (creep) strain σ = stress σ 0.2 = strength corresponding to 0.2% inelastic strain; 0.2% proof strength σ 1 = maximum principal stress σ e = von Mises effective stress σ h = hydrostatic stress σ ref = reference stress ξ = coordinate along the centre line in the weld metal, see Fig. 2Subscripts b = referring to the base material w = referring to the weld metal m = referring to the mismatch condition avg = referring to section-averaged stress values (averaged over the ligament within weldment)

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