Fully plastic J-integral and C* equations for small punch test specimen with a surface crack

Small punch (SP) creep test specimen with an elliptical surface crack was suggested for use with creep crack growth testing. Estimation equations for fracture parameters are needed. K-equation was derived previously for the crack in the SP specimen. In this study, estimation equations for J and C* were derived. 3D elastic-plastic finite element analyses were carried out to determine J value along the front of the surface cracks of the same geometries as were employed for the K-estimation. The dimensionless function, h(1) was determined for various crack locations according to the EPRI scheme. The plastic limit load solution was also determined. The C*-equation of the cracked SP specimen was derived based on the J(p) solution using the analogy between the secondary creep constitutive law and the Ramberg-Osgood plasticity law. The C*-equation may be able to be used to characterize the creep crack growth behavior under the extensive creep condition of the cracked SP specimen.