Event Title

Shearography: A Tool for Imaging Lamb Waves in Composites and their Interaction with Delaminations

Location

Snowbird, UT, USA

Start Date

1-1-1999 12:00 AM

Description

Composite materials, especially in aeronautics, often present themselves as thin structures of large lateral size. Their control is generally performed by pulse-echo technique using ultrasonic bulk waves. A way of reducing the inspection time could be to use Lamb waves. These guided waves present a relatively low attenuation which thus allows to inspect large areas more rapidly. Furthermore, one can select a propagation mode offering no « dead zone » inside the plate [1]. Lamb waves can be generated by piezo transducers with contact, water coupling or, more recently, with air coupling [1,2]. Research is underway to generate Lamb waves through imbedded optical fibers delivering laser pulses [3]. Then the inspection consists in detecting for each considered emission direction either an echo (reflection mode) or an increased attenuation (transmission mode) [1,2]. These indications reveal the presence of a defect in the insonicated area. Depending on the minimal size of the defects and of the induced diffraction pattern, the angular discretization of the « inspection web » around each emission transducer has to be optimized.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

18A

Chapter

Chapter 3: Simulations, Signal Processing, Tomography, and Holography

Section

Inversion, Reconstruction, Imaging

Pages

905-912

DOI

10.1007/978-1-4615-4791-4_116

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Shearography: A Tool for Imaging Lamb Waves in Composites and their Interaction with Delaminations

Snowbird, UT, USA

Composite materials, especially in aeronautics, often present themselves as thin structures of large lateral size. Their control is generally performed by pulse-echo technique using ultrasonic bulk waves. A way of reducing the inspection time could be to use Lamb waves. These guided waves present a relatively low attenuation which thus allows to inspect large areas more rapidly. Furthermore, one can select a propagation mode offering no « dead zone » inside the plate [1]. Lamb waves can be generated by piezo transducers with contact, water coupling or, more recently, with air coupling [1,2]. Research is underway to generate Lamb waves through imbedded optical fibers delivering laser pulses [3]. Then the inspection consists in detecting for each considered emission direction either an echo (reflection mode) or an increased attenuation (transmission mode) [1,2]. These indications reveal the presence of a defect in the insonicated area. Depending on the minimal size of the defects and of the induced diffraction pattern, the angular discretization of the « inspection web » around each emission transducer has to be optimized.