Estimation of high-temperature fracture parameters for small punch specimen with a surface crack

摘要

An outline of a newly proposed methodology for evaluating creep crack growth (CCG) parameters using cracked small-punch (SP) specimens is explained. Three-dimensional finite element analyses were performed to calculate the stress intensity factor along the crack front for a surface crack formed at the centre of a SP specimen. Effects of crack ratio, (a/t); crack aspect ratio, (a/c); and thickness of the specimen, (t), on the fracture parameters were studied. It was observed that the minimum variation of K-value along the crack front can be achieved when alc was 0.50 except the location very near the intersection of the crack and free surface. This condition is similar to the case of constant K-values along the crack front of the conventional compact tension specimen. Thus, it can be argued that the SP specimen with a surface crack is a suitable specimen geometry for CCG testing. The proposed CCG test method was found to be practically applicable for the crack geometry of 0.10 to 0.30 of alt with constant aspect ratio of 0.50. An estimation of the K and C_t-parameter under the small scale creep condition was derived. Future work for further development of the suggested CCG testing is discussed.