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

Abstract

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 a/c 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 a/t 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.