Lamb wave propagation in vibrating structures for effective health monitoring

Abstract

Lamb wave based Structural Health Monitoring (SHM) has received much attention during the past decades for its broad coverage and high sensitivity to damage. Lamb waves can be used to locate and quantify damage in static structures successfully. Nonetheless, structures are usually subjected to various external vibrations or oscillations. Not many studies are reported in the literature concerning the damage detecting ability of Lamb wave in oscillating structures which turns out to be a pivotal issue in the practical application of the SHM technique. For this reason in this study, the propagating capability of Lamb waves in a vibrating thin aluminum plate is examined experimentally. Two circular shaped piezoelectric wafer active transducers are surface-bonded on the aluminum plate where one acted as an actuator and another as a sensor. An arbitrary waveform generator is connected to the actuator for the generation of a windowed tone burst on the aluminum plate. An oscilloscope is connected to the sensor for receiving the traveled waves. An external shaker is used to generate out-of-plane external vibration on the plate structure. Time of flight (TOF) is a crucial parameter in most Lamb wave based SHM studies, which measures wave traveling time from the actuator to sensor. In the present study the influence of the external vibrations on the TOF is investigated. Experiments are performed under different boundary conditions of the plate, such as free-free and fixed by gluing. The effects of external vibrations in the frequency range between 10 Hz to 1000 Hz are analyzed. Comparisons are carried out between the resulting Lamb wave signals from the vibrating plate for different boundary conditions. Experimental results show that the external vibrations in relatively low frequency range do not change the TOF during the application of Lamb wave based SHM.

A Novel Baseline-Free Damage Detection Method Based on Path Scanning of Lamb Waves Using Mobile Transducers

“…The isolated signals are regarded as a specific signature to indicate the presence of structural damage. However, reliable baseline data are extremely difficult and impractical to obtain in realistic conditions due to varying environmental and operational conditions, such as fluctuations in temperature [ 14 , 15 ], variation in surface moisture [ 16 , 17 ], vibrations, loading conditions [ 18 , 19 , 20 ], and so forth. As a result, the baseline-dependent method can identify damages that are sometimes mistaken in the presence of these varying conditions.…”

New semi three-dimensional approach for simulation of Lamb wave clamp-on ultrasonic gas flowmeter

“…Considering ultrasonic flow measurement, experimental and simulation-based studies include the following categories: investigating the effects of pipe configurations on ultrasonic flowmeters (Holm et al, 1995;Hilgenstock and Ernst, 1996;Pamela et al, 2000;Zhao et al, 2015), studying flow profile correction factor (Zhao et al, 2015;O'Sullivan and Wright, 2002;Cheon and Poong Hyun, 2005;Weissenbrunner et al, 2016), exploring transducer protrusion and recess effects on ultrasonic flowmeters (Raišutis, 2006;Zheng et al, 2011;Hoffmann et al, 2015) and considering acoustics effects in ultrasonic flowmeters (Bezdek et al, 2007;Tezuka et al, 2008;Zheng et al, 2016;Sun et al, 2018b). Lamb wave propagation in pipe walls was studied by many authors (Park et al, 2009;Yashiro et al, 2007;Hern andez et al, 2018;Faisal Haider et al, 2017;Luyao et al, 2014;Lu et al, 2015). However, almost all of them are related to air-coupled ultrasonic testing applications.…”

Data-driven model identification of guided wave propagation in composite structures

“…Guided waves of Lamb are also very effective for examining the monitored structures generated by piezoelectric elements [11]. By adequately choosing the amplitude, frequency, and the number of cycles, it is possible to propagate guided waves to examine the state the structures and obtain a detection, location, and characterization based on some damage metrics extracted from these signals.…”