抄録
An ultrasonic experiment has been carried out to evaluate the accumulative creep damage which occurred in polycrystalline pure copper during high-temperature tensile loading. The shear wave velocities exhibited birefringence which arose from the macroscopic anisotropy due to intergranular creeping process controlled by grain-boundary cavitation and subsequent microcracking perpendicular to the stress axis. The velocity anisotropy, which is independent of specimen thickness, decreased very slowly and linearly up to approximately 80% of the time to fracture, and then decreased at increasing rate until the eventual failure. The first period was expended by the nucleation and growth of cavities and the second corresponded to the cavity coalescence and the cracking. Measurements of porosity and metallography supported the ultrasonic observation. The results gave basic information about nondestructive characterization of accumulative creep damage in high-temperature components.
