Event Title

Lamb Wave Contact Scanning Tomography

Location

Snowbird, UT, USA

Start Date

1-1-1999 12:00 AM

Description

Lamb waves are guided ultrasonic waves capable of propagating relatively long distances in thin plates and thin laminated structures, such as airframe skins, storage tanks and pressure vessels. Their propagation properties in these media depend on the vibrational frequency as well as on the thickness and or material properties of the structure. Structural flaws such as disbonds, corrosion and fatigue cracks represent changes in effective thickness and material properties, and therefore measurement of variations in Lamb wave propagation can be employed to assess the integrity of these structures. Lamb wave measurements can be made for a number of relative transducer positions (projections) and an image of the flawed region can be reconstructed tomographically. This paper presents a new technique in which two contact piezoelectric transducers are independently scanned along parallel lines in a fashion analogous to that commonly used in seismic crosshole tomography. These results are compared to those for parallel projection Lamb wave tomography data collected with an automated contact scanning apparatus. The advantages and drawbacks of these two methods in the development of automated tomographic Lamb wave scanners for quantitative mapping of thickness variation in plate-like materials are discussed.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

18A

Chapter

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

Section

Tomography and Holography

Pages

951-958

DOI

10.1007/978-1-4615-4791-4_122

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Lamb Wave Contact Scanning Tomography

Snowbird, UT, USA

Lamb waves are guided ultrasonic waves capable of propagating relatively long distances in thin plates and thin laminated structures, such as airframe skins, storage tanks and pressure vessels. Their propagation properties in these media depend on the vibrational frequency as well as on the thickness and or material properties of the structure. Structural flaws such as disbonds, corrosion and fatigue cracks represent changes in effective thickness and material properties, and therefore measurement of variations in Lamb wave propagation can be employed to assess the integrity of these structures. Lamb wave measurements can be made for a number of relative transducer positions (projections) and an image of the flawed region can be reconstructed tomographically. This paper presents a new technique in which two contact piezoelectric transducers are independently scanned along parallel lines in a fashion analogous to that commonly used in seismic crosshole tomography. These results are compared to those for parallel projection Lamb wave tomography data collected with an automated contact scanning apparatus. The advantages and drawbacks of these two methods in the development of automated tomographic Lamb wave scanners for quantitative mapping of thickness variation in plate-like materials are discussed.