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Simulation of Laser-Ultrasonic Wave Propagation to Measure Mechanical Properties of Metal Sheets

Vajedi, Mahyar | 2008

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39239 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Vossoughi, Gholamreza
  7. Abstract:
  8. Laser ultrasonic is a novel method for measuring sheet parameters. In this technique an intense pulse is irradiated to the target which instantaneously vaporizes the surface layer into the high temperature and high pressure plasma. Expansion of plasma produces shock wave that propagates through the surface. Mechanical properties of target can be calculated by measuring and analyzing produced shock wave. In this project wave propagation is simulated using finite element and numerical-computation methods. The numerical-computation simulation was performed using lamb wave equations. ANSYS software was employed for finite element simulation. The results corroborate each other. Next, simulation of different materials was performed, and the effect of sheet parameters on wave propagation was investigated. According to the results elastic properties of material can be computed by measuring modes’ arrival times. Therefore, three criteria were defined to extract elastic data from measured wave. The ratio of symmetric to anti-symmetric mod amplitudes can be considered as a forth measuring criterion for computing plastic properties of materials. Finally, a neural network is designed to calculate sheet parameters.
  9. Keywords:
  10. Neural Network ; Wave Propagation ; Ultrasonic Waves ; Laser-Ultrasonic Method ; Lamb Wave ; Noncontact Measurment

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