PSI - Issue 57

Giovanni M. Teixeira et al. / Procedia Structural Integrity 57 (2024) 670–691 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 7. The calibration of Voce’s isotropic hardening model for 316 Stainless Steel

2. Mechanism-based deterministic lifetime model 2.1. A Fracture Mechanics Based Method The D TMF method is based on the fracture mechanics idea of correlating crack growth per loading cycle and cyclic crack tip opening displacement (CTOD) [10]: = Δ (18) where  is a parameter to be calibrated and is usually between 1/3 to 1. The crack tip opening displacement is related to the J-Integral by: = ′ 0 (19) 0 being the yield stress and ′ a parameter dependent on the Ramberg-Osgood exponent ′ as per the following equation [11]: ′ = 0.78627 − 4.41692 ′ +6.11945 ′2 −4.2227 ′3 (20) From Heitmann [12], under the hypothesis of a semicircular surface crack ( with crack length a ) in a flat specimen under plane strain and mode 1 loading conditions, the J-Integral is evaluated as: = (1.45 Δ 2 +2.4 Δ ⋅ Δ √1+3 ′ ) (21) The first term addresses the elastic contribution and the second term (originated from [13]) accounts for the plastic contribution to the J-Integral. The combination of equation 19 and 21 results: Δ = ′ 0 (1.45 Δ 2 +2.4 Δ ⋅ Δ √1+3 ′ ) (22)