The influence of stress-regime dependent creep model and ductility in the prediction of creep crack growth rate in Cr–Mo–V steel

Prediction of creep crack growth behavior in Cr–Mo–V steel specimens with different constraints for a wide range of C∗

“…The transition stress is about 250 MPa. The values of the (A 1 , n 1 ) and (A 2 , n 2 ) are listed in Table 2 [38]. This 2RN behavior of the Cr-Mo-V steel is similar to that of the 316H steel [35,36].…”

“…We have developed the 2RN creep model in Eq. (1) in the previous work [38] for the Cr-Mo-V steel used in this work by using the relation between minimum creep rate and stress, and the different Norton model parameters of (A 1 , n 1 ) in low stress regime and (A 2 , n 2 ) in high stress regime are shown in Fig. 1(b).…”

“…The material used in this work is a Cr-Mo-V steel (Chinese 25Cr2NiMo1V steel) which is the same as the steel used in the previous studies of authors [8,37,38], and the chemical composition of the steel is listed in Table 1. The Young's modulus E and yield stress r y of the steel at 566°C are 160 GPa and 383 MPa, respectively.…”

“…The true stress-strain curve of the steel is shown in Fig. 1(a) [38]. For the Cr-Mo-V steels and welded joints with higher yield stress, the two-regime Norton (2RN) creep model is usually developed by using the relations between minimum creep rate (steady state creep rate) and stress in the literature [39][40][41][42], and the scatter of data is very small.…”

“…The upper shelf (US) and lower shelf (LS) creep ductility and the transition region are dependent on materials and temperatures, and have effects on the CCG behavior of materials for a wide range of C ⁄ [35,38,46]. By using the stress dependent creep ductility and strain rate model, the CCG behavior has been successfully simulated in a wide range of C ⁄ for 316H steel [35,36] and Cr-Mo-V steel [38,46], but the use of the constant creep ductility cannot get good results. Thus, in order to accurately predict constraint effect on creep crack growth behavior, the stress dependent creep ductility should be used.…”