Non-Contact Ultrasound Based Guided Lamb Waves for Composite Structure Inspection: Some Interesting Observations

Karthikeyan, P.; Ramdas, C.; Bhardwaj, Mahesh C.; Balasubramaniam, Krishnan

doi:10.1063/1.3114357

Cited by 6 publications

(4 citation statements)

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“…The experimental setup, shown schematically in figure 5, consists of a signal generator, power amplifier, 100 MHz A/D card, signal conditioner and a desk top computer [17]. The probes used were non-contact ultrasonic transducers (NCU) of central frequency 200 kHz, provided by the Ultran Group, USA.…”

Section: Methodsmentioning

confidence: 99%

Interaction of the primary anti-symmetric Lamb mode (A_o) with symmetric delaminations: numerical and experimental studies

Ramadas

Balasubramaniam

Joshi³

et al. 2009

Smart Mater. Struct.

118

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The interaction of an ultrasonic guided Lamb wave mode with delamination type defects in a quasi-isotropic laminated composite plate has been studied, using both simulations and experiments. In a laminated composite plate with a symmetric delamination, when the primary anti-symmetric mode, Ao, is incident at the entrance and exit of a delamination, it generates a new mode, So, that is confined only to sub-laminates and undergoes multiple reflections in the delaminated region. It was observed that only the incident and mode-converted Ao modes propagate in the main laminate. The two modes reverberate between the two ends of the delaminations while undergoing multiple mode conversions, leading to a trail of signals that is captured by the finite element model. The numerical observations were validated using experiments conducted using air coupled ultrasonic transducers.

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Section: Methodsmentioning

confidence: 99%

Interaction of the primary anti-symmetric Lamb mode (A_o) with symmetric delaminations: numerical and experimental studies

Ramadas

Balasubramaniam

Joshi³

et al. 2009

Smart Mater. Struct.

118

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“…The schematic of the experimental set up shown in figure 6 consists of a signal generator, power amplifier, 100 MHz A/D card, signal conditioner and a desktop computer [27]. The probes used were non-contact ultrasonic air coupled transducers (NCU) [28] with a central frequency of 200 kHz, provided by Ultran Group, USA.…”

Section: Experimental Set Upmentioning

confidence: 99%

Interaction of guided Lamb waves with an asymmetrically located delamination in a laminated composite plate

Ramadas¹,

Balasubramaniam²,

Joshi³

et al. 2010

Smart Mater. Struct.

102

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Propagation of the primary anti-symmetric Lamb mode (A o ) in an asymmetrically delaminated cross-ply laminate has been studied through both numerical simulations and experiments employing the air coupled ultrasonic technique. When the A o mode interacts with the entrance and the exit of an asymmetrically located delamination, in addition to A o , a mode converted to the primary symmetric Lamb mode (S o ) also propagates in each of the two sub-laminates as well as the main laminate. These Lamb modes propagate independently in each of the sub-laminates. In addition, turning modes (i.e. the mode propagating in one sub-laminate interacts with delamination edge and starts propagating in the other sub-laminate) and a mode converted turning mode (a new mode is generated during the interaction of turning mode with delamination edge) were also observed in the numerical simulation. The presence of the 'mode converted turning modes' was also validated through the experiments in this study.

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“…It was shown (Karthikeyan et al, 2009;Ramadas et al, 2009) that when A o mode is incident on the entrance of delamination (E) in Figure 1(a), it splits into two A o modes, and propagates independently in each sub-laminate as A o A o wave groups. This wave group, A o A o , reaches the exit of delamination (X), interacts with it and transmits in the main laminate as The locations of transmitter and receiver are shown in Figure 1(b).…”

Section: Expression For Delamination Lengthmentioning

confidence: 99%

“…Guo and Cawley (1994), and Valdes and Soutis (2002), determined the location of delamination using the arrival time of Lamb wave reflected at the delamination edge. Karthikeyan et al (2009) and Ramadas et al (2009) studied the interaction of primary anti-symmetric Lamb mode with symmetric delaminations, both numerically and experimentally, using non-contact ultrasonic transducers. It was found that when A o mode interacts with a symmetric delamination, it generates a new mode, S o , which is confined only to the sub-laminates, that is, the delaminated region, and can be detected in the main laminate through the mode converted A o mode when the S o mode interacts with the exit portion of the delamination.…”

Section: Introductionmentioning

confidence: 99%

Delamination Size Detection using Time of Flight of Anti-symmetric (A_o) and Mode Converted A_o mode of Guided Lamb Waves

Ramadas

Padiyar

Balasubramaniam

et al. 2010

Journal of Intelligent Material Systems and Structures

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In this article an attempt has been made to quantitatively assess the extent of delamination in composite laminates, using time-of-flight of fundamental Lamb wave modes, without recourse to baseline data from a healthy structure. An expression has been derived to determine the delamination size, from group velocities of primary Lamb modes in the sub-laminates and time-of-flight of transmitted Ao signal and mode converted Ao signal, which is generated when Ao mode propagates through a delamination. The effectiveness of the expression, when group velocities of primary Lamb modes in the main laminate were used, has been verified through numerical simulations carried out on a quasi-isotropic glass/epoxy laminate with various delamination interfaces. The effectiveness of the expression has also been verified experimentally, on two GFRP cross-ply laminates of [0/90/0] lay-up with 40 mm and 50 mm delamination sizes, using air coupled ultrasonic transducers. The predicted delamination sizes were found to be in good agreement with the actual delamination sizes. Using the proposed technique absolute identification of delamination is possible. A supplementary equation for determining the minimum length of delamination has also been derived and presented in the article.

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Non-Contact Ultrasound Based Guided Lamb Waves for Composite Structure Inspection: Some Interesting Observations

Cited by 6 publications

References 0 publications

Interaction of the primary anti-symmetric Lamb mode (A_o) with symmetric delaminations: numerical and experimental studies

Interaction of the primary anti-symmetric Lamb mode (A_o) with symmetric delaminations: numerical and experimental studies

Interaction of guided Lamb waves with an asymmetrically located delamination in a laminated composite plate

Delamination Size Detection using Time of Flight of Anti-symmetric (A_o) and Mode Converted A_o mode of Guided Lamb Waves

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Non-Contact Ultrasound Based Guided Lamb Waves for Composite Structure Inspection: Some Interesting Observations

Cited by 6 publications

References 0 publications

Interaction of the primary anti-symmetric Lamb mode (Ao) with symmetric delaminations: numerical and experimental studies

Interaction of the primary anti-symmetric Lamb mode (Ao) with symmetric delaminations: numerical and experimental studies

Interaction of guided Lamb waves with an asymmetrically located delamination in a laminated composite plate

Delamination Size Detection using Time of Flight of Anti-symmetric (Ao) and Mode Converted Ao mode of Guided Lamb Waves

Contact Info

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Resources

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Interaction of the primary anti-symmetric Lamb mode (A_o) with symmetric delaminations: numerical and experimental studies

Interaction of the primary anti-symmetric Lamb mode (A_o) with symmetric delaminations: numerical and experimental studies

Delamination Size Detection using Time of Flight of Anti-symmetric (A_o) and Mode Converted A_o mode of Guided Lamb Waves