J4 ›› 2011, Vol. 28 ›› Issue (3): 362-368.

• Laser Applications • Previous Articles     Next Articles

Numerical analysis of inspection of micro-surface crack by laser generated surface acoustic waves

GUAN Jian-fei   

  1. College of Optoelectronic Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210046, China
  • Received:2010-04-09 Revised:2010-05-17 Published:2011-05-28 Online:2011-05-20

Abstract:

Plane strain finite element method has been employed in this paper to simulate the generation of the surface acoustic wave by the line focused pulsed laser irradiation on the aluminates plate. The temporal displacemental signals on the plate surface have been calculated and compared with the waveforms obtained in the numerical model with a surface micro cracks introduced in the near field of the laser source. The numerical results demonstrate that the monopolar displacement signals of surface skimming longitudinal wave (sP) and Rayleigh wave (R) become the obvious bipolar signals, as there exists a surface micro defect in the immediate vicinity of the laser line source; in addition, the peak-to-peak value of the bipolar Rayleigh wave signal is enhanced about two times compared with the initial monopolar one. This dramatic transition can be the basis for the scanning laser line source inspection technique for shallow cracks.

Key words: laser techniques, surface acosutic wave, finite element method, surface crack, peak to peak value

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