Effect of specimen size on creep crack growth rate using ultra-large CT specimens for 1Cr-Mo-V steel

In order to establish an evaluation method of creep crack growth in the structural components of high temperature engineering plant, it is necessary to clarify the effect of specimen size on creep crack growth behaviour. However, experimental investigation using large specimens concerning specimen size effect on creep crack growth has been little conducted. We conducted creep crack growth tests using CT specimens of various sizes, including ultra-large CT specimens of 254 mm in width and 63.5 mm in thickness which had never been investigated. Creep crack growth rate was characterized in terms of C ∗ parameter. Correlation of creep crack growth rate with C ∗ parameter was independent of specimen width, but dependent on specimen thickness. As the specimen thickness increased, the creep crack growth rate increased. It was considered that the effect of specimen thickness on creep crack growth rate was due to constraints of deformation during creep crack propagation.