This paper presents the results of an experimental study of the applicability of the
laser Doppler vibrometer (LDV) as a potential measurement tool for structural
health monitoring in pipelines. In this case, use of the LDV has been integrated
into a novel damage detection method referred to as the empirical mode
decomposition (EMD) energy damage index. This method involves monitoring the
free vibrations of a pipe through sensors, followed by decomposition of the
sensor generated signals using EMD, and subsequently comparing an energy
term of the pipe in its healthy state to that of the same pipe in a damaged
state. In the experiment, a single beam LDV was utilized to acquire the
vibration of a cantilever steel pipe impacted by an impulse hammer. Three
cases were studied: pipes with a single half-circumferential damage, a single
full-circumferential damage, and with multiple circumferential damages.
The integrity of the LDV results was verified by comparison with those
obtained from piezoceramic sensors bonded to the pipe surface. The results
confirmed the effectiveness of the LDV and its integration into the proposed
EMD damage index for identifying and locating single and multiple damages.
Compared to piezoceramic sensors, the LDV, as a remote and accurate optical
measurement system, provided more satisfactory identification of single and
multiple damages and can therefore be successfully utilized in structural health
monitoring.