LAMB WAVE EXCITATION BY HERTZIAN CONTACTS WITH APPLICATIONS IN NDE

Citation
Fl. Degertekin et Bt. Khuriyakub, LAMB WAVE EXCITATION BY HERTZIAN CONTACTS WITH APPLICATIONS IN NDE, IEEE transactions on ultrasonics, ferroelectrics, and frequency control, 44(4), 1997, pp. 769-779
Citations number
24
Categorie Soggetti
Engineering, Eletrical & Electronic",Acoustics
ISSN journal
08853010
Volume
44
Issue
4
Year of publication
1997
Pages
769 - 779
Database
ISI
SICI code
0885-3010(1997)44:4<769:LWEBHC>2.0.ZU;2-A
Abstract
Excitation of Lamb waves in solid prates by point-like Hertzian contac ts for material characterization and nondestructive testing is investi gated. A 2 dimensional model using normal mode theory is used to predi ct the relative excitation efficiency of the lowest order Lamb waves i n anisotropic solid plates. Hertzian contact transducers with PZT-5H p iezoelectric material and quartz; buffer rods are realized to operate in the 200 to 500 kHz range for experimental verification. Single mode operation with the lowest order antisymmetric Lamb wave (A(o)) mode i s achieved in various plates at in agreement with theoretical predicti ons. The technique is applied for material characterization on single crystal silicon samples and defect detection in composite plates. The phase velocity anisotropy of the A(o) mode is measured with signal-to- noise levels exceeding 65 dB. In (111) cut silicon plates the absolute phase velocity is measured with +/-0.05% accuracy. The phase velocity anisotropy and effects of delamination in layered composite plates ar e calculated using the surface impedance approach. The experiments on graphite/epoxy composite plates agree with these calculations and show the potential of the method for defect detection with high resolution .