SA-06-2(013) Size Distribution of Creep Cracks and Fracture Mechanisms in High-Temperature Materials(Flaw Assessment at Elevated Temperature 1)

概要

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The size distribution of large cracks, which could lead to creep fracture, was examined on the ruptured or crept specimens of heat-resistant materials. The number of the cracks, N, of the size (x') equal to or larger than X(x'≧X) can be fitted to a power law, N(x'≧X) ∝ X^<-b>, with a scaling exponent b at the large crack sizes in the ruptured specimens of the HS-21 alloy. This result was expected by the theoretical prediction based on a stable distribution of cracks. However, the relationship between the value of N(x'≧X) and that of X was better fitted to an exponential law, N(x'≧X) ∝ exp(-cX), with a parameter c for all the cracks in the crept specimens of the SUS304 steel. The values of b and c depended on creep conditions such as creep strain or microstructures of materials. Grain-boundary fracture occurred in the HS-21 alloy, while the SUS304 steel exhibited a mixed mode of grain-boundary fracture and transgranular fracture. The difference in the relationship between the cumulative number of cracks (N(x'≧X)) and the crack length (X) were correlated to that in the fracture mechanisms between these materials.
一般社団法人日本機械学会の論文
2001-06-03