A NOVEL APPLICATION OF A LASER DOPPLER VIBROMETER IN A HEALTH MONITORING SYSTEM

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.