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

Abstract

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. The applicability of the conventional C* equation based on the load line displacement is re-examined by using the finite element method. It is found that under the extensive creep condition the C* value of hard weld/soft parent metal specimen can be significantly higher than that of a 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 behaviour of welded specimens. Candidate modification factors have been proposed. (C) 1999 Elsevier Science Ltd. All rights reserved.