Materials Characterization Using Holographic Mapping of Transient Lamb Waves
Abstract
The testing of engineering materials is traditionally done using contact ultrasonic techniques or potentially destructive mechanical tests. For many materials, elastic properties are a function of both position and direction, owing to material anisotropy and inhomogeneities arising from process variation and defects. In order to determine these elastic properties as a function of position or direction using conventional techniques, it is necessary to scan the testing apparatus over the surface of the material. In contrast, holographic methods offer a means of full field determination of the elastic properties. Toward this end, the spatial propagation of antisymmetric Lamb waves in nearly homogeneous isotropic plates has been investigated. Using high speed pulsed holographic techniques coupled with excitation of ultrasonic waves, surface displacements arising from Lamb wave propagation in thin plates result in interference patterns super-sign imposed on the holographic reconstruction of the speciment image. The determination of Lamb wave group velocities utilizing a technique which uses only features of the spatial waveform has been demonstrated to yield results in good agreement with elastic plate theory. In addition, preliminary results show that the same holographic techniques may prove a useful tool in the characterization and evaluation of laminated composite plates. Keywords: Flexural waves; Holography; Holographic interferometry; Acoustic wave visualization.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1989
- Accession Number
- ADA211414
Entities
People
- James W. Wagner
- Michael J. Ehrlich
Organizations
- Johns Hopkins University