Mechanisms of time-dependent crack growth at elevated temperature. Final project report, July 1, 1986--August 31, 1989

Abstract

MASTER _, DIS"r'Rt_ON OF: Tilts I_OC, UM'ENT IS UNLIMITED techniques for detecting crack tip cavitation damage including electron metallography, synchrotron x-ray tomography, digital microradiography and small angle neutron scattering (SANS) were also evaluated. The study led to the following important conclusions. • In the presence of large scale cavitation damage and crack branching, time rate of creep crack growth (da/dt) i does not correlate with Ct or with C*. On the other hand, when the cavitation damage is constrained, da/dt is uniquely characterized by C t. • Area fraction of grain boundary cavit_ted, Ac, appears to be the single damage parameter for characterizing the extent of cavitation damage ahead of crack tips. The distribution of Ac ahead of the crack tip is a complex function of loading wave form and cycle time.