Optical Fibre Sensing of High Order Lamb Waves for Structural Health Monitoring

Rosalie, Cedric; Norman, Patrick; Smithard, Joel; Davis, Claire; Rajic, Nik

doi:10.1115/smasis2012-8023

Cited by 7 publications

(5 citation statements)

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“…When interrogated using intensity-based methods [7] they are capable of detecting high frequency wave-fields with the bandwidth limited only by the photo-current to voltage conversion electronics (typically > 100 MHz). Recent work by the authors has demonstrated the ability of FBGs to measure strain-fields at frequencies in excess of 2 MHz [1].…”

Section: Introductionmentioning

confidence: 99%

Interaction of High Frequency Lamb Waves with Surface-Mount Sensor Adhesives

Norman¹,

Davis²,

Rosalie³

et al. 2013

KEM

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The application of Lamb waves to damage and/or defect detection in structures is typicallyconfined to lower frequencies in regimes where only the lower order modes propagate in order to simplifyinterpretation of the scattered wave-fields. Operation at higher frequencies offers the potentialto extend the sensitivity and diagnostic capability of this technique, however there are technical challengesassociated with the measurement and interpretation of this data. Recent work by the authorshas demonstrated the ability of fibre Bragg gratings (FBGs) to measure wave-fields at frequencies inexcess of 2 MHz [1]. However, when this work was extended to other thinner plate specimens it wasfound that at these higher frequencies, the cyanoacrylate adhesive (M-Bond 200) used to attach theFBG sensors to the plate was significantly affecting the propagation of the waves. Laser vibrometrywas used to characterise the wave-field in the region surrounding the adhesive and it was found that theself-adhesive retro-reflective tape applied to aid with this measurement was also affecting the wavefieldin the higher frequency regime. This paper reports on an experimental study into the influence ofboth of these materials on the propagating wave-field. Three different lengths of retro-reflective tapewere placed in the path of Lamb waves propagating in an aluminium plate and laser vibrometry wasused to measure the wave-field upstream and downstream of the tape for a range of different excitationfrequencies. The same experiment was conducted using small footprint cyanoacrylate film samplesof different thickness. The results show that both of these surface-mount materials attenuate, diffractand scatter the incoming waves as well as introducing a phase lag. The degree of influence of thesurface layer appears to be a function of its material properties, the frequency of the incoming waveand the thickness and footprint of the surface layer relative to the base material thickness. Althoughfurther work is required to characterise the relative influence of each of these variables, investigationsto date show that for the measurement of Lamb Waves on thin structures, careful considerationshould be given to the thickness and footprint of the adhesive layer and sensor, particularly in the highfrequency regime, so as to minimise their effect on the measurement.

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Section: Introductionmentioning

confidence: 99%

Interaction of High Frequency Lamb Waves with Surface-Mount Sensor Adhesives

Norman¹,

Davis²,

Rosalie³

et al. 2013

KEM

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“…Previous work was constrained to a relatively low frequency regime (≤ 200kHz) because of a limitation related to the ratio of the sensor length to the acoustic wavelength [12]. Recent experimental work has demonstrated a significant increase in the plate-wave frequency bandwidth of an in-situ FBG, which has been shown to resolve the elastic wave dynamics in a metallic plate at frequencies of up to 2 MHz [13].…”

Section: Dsto Technical Program Overviewmentioning

confidence: 99%

Development and Validation Roadmap for <i>In Situ</i> Structural Health Monitoring of ADF Aircraft

Galea¹,

Rajic²

2013

KEM

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In recent times there has been concerted pressure on military organisations worldwide to push for significant reductions in through-life support costs while maintaining and improving aircraft availability and safety. These goals, which on the surface may appear contradictory, can be achieved through the introduction of Structural Health Monitoring (SHM) systems. The paper describes the Australian Defence Science and Technology Organisation (DSTO) roadmap for SHM system development, validation, certification and implementation, in the context of technologies and systems that meet Australian Defence Force (ADF) future requirements. The current approach focuses on wide-area damage detection SHM systems using acousto-ultrasonic techniques.

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“…Optical fiber sensors are not only more durable than piezo-ceramic sensors but are also immune to electromagnetic interference, have a small footprint which allows them to be easily embedded in fiber composites, and in the case of FBGs are readily multiplexed allowing for distributed sensing. Recent studies have shown that FBG sensors can achieve high bandwidths and are thus capable of detecting higher order Lamb waves [ 6 ] and when written in a high-density array are capable of resolving multi-modal wave packets into constituent modes [ 7 , 8 , 9 ].…”

Section: Introductionmentioning

confidence: 99%

An Advanced Multi-Sensor Acousto-Ultrasonic Structural Health Monitoring System: Development and Aerospace Demonstration

et al. 2017

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A key longstanding objective of the Structural Health Monitoring (SHM) research community is to enable the embedment of SHM systems in high value assets like aircraft to provide on-demand damage detection and evaluation. As against traditional non-destructive inspection hardware, embedded SHM systems must be compact, lightweight, low-power and sufficiently robust to survive exposure to severe in-flight operating conditions. Typical Commercial-Off-The-Shelf (COTS) systems can be bulky, costly and are often inflexible in their configuration and/or scalability, which militates against in-service deployment. Advances in electronics have resulted in ever smaller, cheaper and more reliable components that facilitate the development of compact and robust embedded SHM systems, including for Acousto-Ultrasonics (AU), a guided plate-wave inspection modality that has attracted strong interest due mainly to its capacity to furnish wide-area diagnostic coverage with a relatively low sensor density. This article provides a detailed description of the development, testing and demonstration of a new AU interrogation system called the Acousto Ultrasonic Structural health monitoring Array Module+ (AUSAM+). This system provides independent actuation and sensing on four Piezoelectric Wafer Active Sensor (PWAS) elements with further sensing on four Positive Intrinsic Negative (PIN) photodiodes for intensity-based interrogation of Fiber Bragg Gratings (FBG). The paper details the development of a novel piezoelectric excitation amplifier, which, in conjunction with flexible acquisition-system architecture, seamlessly provides electromechanical impedance spectroscopy for PWAS diagnostics over the full instrument bandwidth of 50 KHz–5 MHz. The AUSAM+ functionality is accessed via a simple hardware object providing a myriad of custom software interfaces that can be adapted to suit the specific requirements of each individual application.

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Optical Fibre Sensing of High Order Lamb Waves for Structural Health Monitoring

Cited by 7 publications

References 0 publications

Interaction of High Frequency Lamb Waves with Surface-Mount Sensor Adhesives

Interaction of High Frequency Lamb Waves with Surface-Mount Sensor Adhesives

Development and Validation Roadmap for <i>In Situ</i> Structural Health Monitoring of ADF Aircraft

An Advanced Multi-Sensor Acousto-Ultrasonic Structural Health Monitoring System: Development and Aerospace Demonstration

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