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Published on: February 14, 2017
Generation of negative group velocity Lamb waves by a moving laser source
Alexey M Lomonosov1, Chenyin Ni2, Zhonghua Shen3
1School of Science, Nanjing University of Science and Technology, Nanjing 210094, China; Prokhorov General Physics Institute of the Russian Academy of Sciences, 119911 Moscow, Russia; Scientific-Technological Center of Unique Instrumentation, Russian Academy of Sciences, 117342 Moscow, Russia.
Abstract:
Analytical existence conditions for negative group velocity (NGV) of an arbitrary mode Lamb waves in elastic plate was obtained. Experimentally, NGV waves were excited by means of a thermoelastic laser source moving across the sample plate with a controllable velocity. Such source is coupled with modes which phase velocity component parallel to the surface coincides with the source speed. Additional mode selection was performed by choosing a quasiperiodic shape of the laser spot, which specifies the range of the wavenumber k. This technique was successfully applied for generation of backward (NGV) waves. By tuning the speed of the source the propagation direction was switched from forward to reversal.
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