Review of Noncontact Ultrasonic Measurement System for Structural Health Monitoring _ Crimson Publishers

 Review of Noncontact Ultrasonic Measurement System for Structural Health Monitoring by Makiko Kobayashi* in Advancements in Civil Engineering & Technology_ Open Journal of Civil Engineering

 

Abstract

Non-destructive testing (NDT) of infrastructure such as bridges and tunnels has become more important since it has aging problem and traffic was heavier than expected. Thin film ultrasonic sensors would be attractive because it is easy to integrate on huge structure. However, NDT of huge structure is still challenging because of sensor accessibility. Semi-noncontact ultrasonic sensors were proposed in this manuscript. 20cm diameter copper coil transmit/receive electrical signal from a pulser/receiver instrument and a thin film ultrasonic sensor and reflected echo from 12.7mm thick steel plate successfully. By this method, measurement using drone could be possible and it increases application possibility for huge infrastructure monitoring.

Recently, air-coupled ultrasonic transducers made by Capacitive Micromachined UltrasonicTransducer (CMUT) has been developed and the transmitting powder and the resolution has been improved [5]. However, air-coupled ultrasonic transducers are often used to detect obstacles in the air, and it is still challenging to inspect inside of the structures due to acoustic impedance difference. Incident angle is also critical. Electromagnetic acoustic transducers (EMATs) are applied high temperature metallic structures [6]. Intrinsically, this technique can be applied for only conductive material so that it is not suitable for many civil infrastructure components. In laser ultrasound, laser induced ultrasound, i.e., inspection structure itself is ultrasound transmitter and reflected ultrasound is picked up by optical method [7]. This technique is suitable to detect huge and complex geometry and there is no incident angle problem. already applied mainly in aerospace industry. However, since ultrasound generation efficiency is low so that optical detection system is costly. To carry out ultrasonic measurement without wires (kind of non-contact) in relatively low cost for civil infrastructures, combination of thin film ultrasonic sensors and wireless power transmission was tested.

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