Nondestructive evaluation of ceramic materials using terahertz impulse ranging

Terahertz (THz) impulse ranging is used to examine ceramic ball bearings for fractures. THz radiation is demonstrated to transmit through both unfired and fired ceramic targets. The electromagnetic scattering signature of commercial aluminum oxide bearings is measured and compared to identical bearings damaged by thermal stress. Two separate methods are used to determine the presence of fractures: late time impulse response and time domain angular modulation. Late time impulse response detects changes in temporally shifted scattering mechanisms, while time domain angular modulation allows rapid detection of fractures. This evaluation technique is non-contact, nondestructive, requires no liquid medium, and is insensitive to ambient temperatures.