Abstract
An ultrasonic experiment has been done to find the effect of ultrasonic waves on the accumulative creep damage which occurs in polycrystalline pure copper during high-temperature tensile loading. The longitudinal wave velocity was sensitive to the intergranular creeping process controlled by grain boundary cavitation and subsequent microcracking. The velocity decreased slowly and linearly up to about 60% of the time to rupture, when the steady creep shifted to the accelerated creep. It then decreased with increasing rate until the eventual failure. Measurements of porosity and photomicrographic observations revealed that the first period is associated with the nucleation and growth of cavities and the second corresponds to cracking perpendicular to the stress. A nondestructive technique for predicting the remaining life time of high-temperature components was also suggested.
