Inspection of Circumferential Cracks Beyond Elbows. In
order to inspect the circumferential cracks beyond elbows, the
penetration rate for different kinds of pipes configurations is
investigated first by using the integrated pipes. Figure 8 shows
the amplitude of the end echo of the three types of pipes
under the condition that excitation frequencies are from 95
kHz to 115 kHz. The amplitudes of the end echo at various
frequencies are extracted from the received time-domain
waveforms.