Abstract
In recent years, with the continuing progress of aging social infrastructures such as bridges and tunnels, there has been high demand for the assessment of deterioration of their performance and conditions. Since current inspection methods for those structures have mainly relied on human resources, it is important to reduce their increasing maintenance cost. One of the key methods for achieving effective maintenance without expensive human costs is to use sensors to discriminate between healthy and unhealthy conditions. In this paper, a MEMS (micro electro mechanical systems) wideband frequency sensor, which is referred to as a super acoustic (SA) sensor, is evaluated through the pencil lead break (PLB) test. Due to its wideband frequency characteristics, the SA sensor is expected to be a promising alternative to the existing vibration sensors, including acoustic emission (AE) sensors. Several PLB signals were generated on an aluminum plate (5 mm thick), and propagating Lamb waves were detected by both AE and SA sensors. SA sensors were able to identify the location of PLB sources on the plate by measuring time differences between each sensor. By comparing the wave spectrums of both the AE and SA sensors analyzed by wavelet transform, the applicability of SA sensor for AE measurement is verified.
Highlights
There are many types of sensors for measuring vibration
The sensor was evaluated by measuring face to face frequency characteristics [3,5], which exhibited continuous sensitivity from several tens of kHz to several MHz, and received acoustic emission (AE) signals, including pencil lead break (PLB) tests [15,16]
PLB test results measured by super acoustic (SA) and AE sensors are evaluated by wavelet transform to investigate the applicability of SA sensors for AE measurement
Summary
There are many types of sensors for measuring vibration. The acoustic emission (AE) sensor is one sensor among them, aimed at measuring quite small amplitudes of vibration, referred to as acoustic emission. Compared to the piezoelectric sensors, MEMS sensors have beneficial characteristics such as low cost as a result of mass production, and smaller size. There are different type of transduction principles, such as optics, MEMS vibration sensors-including AE sensors-consist of three types of major transduction methods; piezoresistive, capacitive and piezoelectric. Capacitive- and resonant-type MEMS AE sensors have been actively researched in the academic field [6,7,8,9,10]. The sensor was evaluated by measuring face to face frequency characteristics [3,5], which exhibited continuous sensitivity from several tens of kHz to several MHz, and received AE signals, including PLB (pencil lead break) tests [15,16]. PLB test results measured by SA and AE sensors are evaluated by wavelet transform to investigate the applicability of SA sensors for AE measurement
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