The influence of material mismatch of weld on the evaluation of time-dependent fracture mechanics parameters

The influence of material mismatch on the stress field of uniaxial specimens and the time-dependent fracture mechanics parameters is studied in the present work. It is found that under the extensive creep condition C* value of hard weld /soft parent metal specimen can be significantly higher than that of single weld metal specimen, and the material mismatch has little influence on C(t) in small scale creep in the studied cases. It is proposed that the C* formula based on the load-line displacement recommended by ASTM E1457 needs to be modified to interpret the CCG behavior of welded specimens. Candidate modification factors have been proposed. A creep crack growth rate test on SENT specimens has been carried out. The CCG data interpretation in terms of the modified formula illustrates the errors by use of the conventional method.