An experimental and computational study of Lamb wave scattering by edge delaminations around circular holes

Nithurshan Nadarajah, L. R. Francis Rose, Wing Kong Chiu

Research output: Chapter in Book/Report/Conference proceedingConference PaperResearch

Abstract

This paper presents a study on the scattering of the fundamental flexural Lamb wave mode (A0) by an edge delamination around the circumference of a circular through hole in a plate. Although edge delaminations are recognized as an important form of structural damage in fiber-composite laminates, there is little previous work on Lamb wave scattering by this form of damage This study uses a 3D laser vibrometer to obtain a detailed experimental characterization of the angular dependence of the scattered field from an edge delamination, for an incident probing wave at various angles of incidence. These experimental observations are correlated with computational results obtained by using the commercial Finite Element package ABAQUS, showing excellent correlation. To assist with a detailed quantitative analysis of this complicated scattering process, Aluminium is used instead of a composite laminate, as this removes further complications that arise due to the anisotropic and multilayer nature of the material in composites. A simulated semi-circular delamination is introduced at the boundary of a circular hole of 20mm diameter, in the mid plane location of the plate using cutting tool. The probing signal is a narrowband 5.5-cycle tone burst with a center frequency of 200 kHz, for which the corresponding A0 wavelength is λ = 10 mm. The relatively small damage size studied corresponds to early damage detection which is the main area of interest for SHM applications The Scattered Amplitude Pattern is used to study the relationship between the scattered field and damage orientation relative to the incident wave. Results obtained indicate a strong dependence between the scattering amplitude pattern and angle of incidence. The results show that the scatter field amplitude and directivity information can be used to detect and quantify the damage in any orientation around the through hole, which confirms and extends the correlations obtained in our previous work for delaminations at a straight edge. This forward scattering problem provides a necessary pre-requisite for addressing the more challenging inverse problem of characterizing the damage from observations of the scattered field, particularly for complex geometries involving detection on the blind side of through holes.

Original languageEnglish
Title of host publication8th European Workshop on Structural Health Monitoring, EWSHM 2016
Subtitle of host publicationBilbao, Spain; 5-8 July 2016
Place of PublicationBad Breisig, Germany
PublisherNDT Internet Publishing
Pages1077-1086
Number of pages10
Volume2
ISBN (Print)9781510827936
Publication statusPublished - 2016
Event8th European Workshop on Structural Health Monitoring - Bilbao, Spain
Duration: 5 Jul 20168 Jul 2016
Conference number: 8

Conference

Conference8th European Workshop on Structural Health Monitoring
Abbreviated titleEWSHM 2016
CountrySpain
CityBilbao
Period5/07/168/07/16

Keywords

  • Delamination damage
  • Experimental validation.
  • Lamb waves
  • Wave Scattering

Cite this

Nadarajah, N., Francis Rose, L. R., & Chiu, W. K. (2016). An experimental and computational study of Lamb wave scattering by edge delaminations around circular holes. In 8th European Workshop on Structural Health Monitoring, EWSHM 2016: Bilbao, Spain; 5-8 July 2016 (Vol. 2, pp. 1077-1086). Bad Breisig, Germany: NDT Internet Publishing.
Nadarajah, Nithurshan ; Francis Rose, L. R. ; Chiu, Wing Kong. / An experimental and computational study of Lamb wave scattering by edge delaminations around circular holes. 8th European Workshop on Structural Health Monitoring, EWSHM 2016: Bilbao, Spain; 5-8 July 2016. Vol. 2 Bad Breisig, Germany : NDT Internet Publishing, 2016. pp. 1077-1086
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Nadarajah, N, Francis Rose, LR & Chiu, WK 2016, An experimental and computational study of Lamb wave scattering by edge delaminations around circular holes. in 8th European Workshop on Structural Health Monitoring, EWSHM 2016: Bilbao, Spain; 5-8 July 2016. vol. 2, NDT Internet Publishing, Bad Breisig, Germany, pp. 1077-1086, 8th European Workshop on Structural Health Monitoring, Bilbao, Spain, 5/07/16.

An experimental and computational study of Lamb wave scattering by edge delaminations around circular holes. / Nadarajah, Nithurshan; Francis Rose, L. R.; Chiu, Wing Kong.

8th European Workshop on Structural Health Monitoring, EWSHM 2016: Bilbao, Spain; 5-8 July 2016. Vol. 2 Bad Breisig, Germany : NDT Internet Publishing, 2016. p. 1077-1086.

Research output: Chapter in Book/Report/Conference proceedingConference PaperResearch

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AB - This paper presents a study on the scattering of the fundamental flexural Lamb wave mode (A0) by an edge delamination around the circumference of a circular through hole in a plate. Although edge delaminations are recognized as an important form of structural damage in fiber-composite laminates, there is little previous work on Lamb wave scattering by this form of damage This study uses a 3D laser vibrometer to obtain a detailed experimental characterization of the angular dependence of the scattered field from an edge delamination, for an incident probing wave at various angles of incidence. These experimental observations are correlated with computational results obtained by using the commercial Finite Element package ABAQUS, showing excellent correlation. To assist with a detailed quantitative analysis of this complicated scattering process, Aluminium is used instead of a composite laminate, as this removes further complications that arise due to the anisotropic and multilayer nature of the material in composites. A simulated semi-circular delamination is introduced at the boundary of a circular hole of 20mm diameter, in the mid plane location of the plate using cutting tool. The probing signal is a narrowband 5.5-cycle tone burst with a center frequency of 200 kHz, for which the corresponding A0 wavelength is λ = 10 mm. The relatively small damage size studied corresponds to early damage detection which is the main area of interest for SHM applications The Scattered Amplitude Pattern is used to study the relationship between the scattered field and damage orientation relative to the incident wave. Results obtained indicate a strong dependence between the scattering amplitude pattern and angle of incidence. The results show that the scatter field amplitude and directivity information can be used to detect and quantify the damage in any orientation around the through hole, which confirms and extends the correlations obtained in our previous work for delaminations at a straight edge. This forward scattering problem provides a necessary pre-requisite for addressing the more challenging inverse problem of characterizing the damage from observations of the scattered field, particularly for complex geometries involving detection on the blind side of through holes.

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Nadarajah N, Francis Rose LR, Chiu WK. An experimental and computational study of Lamb wave scattering by edge delaminations around circular holes. In 8th European Workshop on Structural Health Monitoring, EWSHM 2016: Bilbao, Spain; 5-8 July 2016. Vol. 2. Bad Breisig, Germany: NDT Internet Publishing. 2016. p. 1077-1086