TY - GEN
T1 - Pulsed laser generation of ultrasound in a metal plate between the melting and ablation thresholds
AU - Every, A. G.
AU - Utegulov, Z. N.
AU - Veres, I. A.
N1 - Publisher Copyright:
© 2015 AIP Publishing LLC.
PY - 2015
Y1 - 2015
N2 - The generation of ultrasound in a metal plate exposed to nanosecond pulsed laser heating, sufficient to cause melting but not ablation, is treated. Consideration is given to the spatial and temporal profiles of the laser pulse, penetration of the laser beam into the sample, the evolution of the melt pool, and thermal conduction in the melt and surrounding solid. The excitation of the ultrasound takes place over a few nanoseconds, and occurs predominantly within the thermal diffusion length of a micron or so beneath the surface. Because of this, the output of the thermal simulations can be represented as axially symmetric transient radial and normal surface force distributions. The epicentral displacement response at the opposite surface to these forces is obtained by two methods, the one based on the elastodynamic Green's functions for plate geometry determined by the Cagniard generalized ray method, and the other using a finite element numerical method. The two approaches are in very close agreement. Numerical simulations are reported of the epicentral displacement response of a 3.12mm thick tungsten plate irradiated with a 4 ns pulsed laser beam with Gaussian spatial profile, at intensities below and above the melt threshold. Comparison is made between results obtained using available temperature dependent thermophysical data, and room temperature materials constants except near the melting point.
AB - The generation of ultrasound in a metal plate exposed to nanosecond pulsed laser heating, sufficient to cause melting but not ablation, is treated. Consideration is given to the spatial and temporal profiles of the laser pulse, penetration of the laser beam into the sample, the evolution of the melt pool, and thermal conduction in the melt and surrounding solid. The excitation of the ultrasound takes place over a few nanoseconds, and occurs predominantly within the thermal diffusion length of a micron or so beneath the surface. Because of this, the output of the thermal simulations can be represented as axially symmetric transient radial and normal surface force distributions. The epicentral displacement response at the opposite surface to these forces is obtained by two methods, the one based on the elastodynamic Green's functions for plate geometry determined by the Cagniard generalized ray method, and the other using a finite element numerical method. The two approaches are in very close agreement. Numerical simulations are reported of the epicentral displacement response of a 3.12mm thick tungsten plate irradiated with a 4 ns pulsed laser beam with Gaussian spatial profile, at intensities below and above the melt threshold. Comparison is made between results obtained using available temperature dependent thermophysical data, and room temperature materials constants except near the melting point.
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U2 - 10.1063/1.4914749
DO - 10.1063/1.4914749
M3 - Conference contribution
AN - SCOPUS:85023767162
T3 - AIP Conference Proceedings
SP - 1350
EP - 1359
BT - 41st Annual Review of Progress in Quantitative Nondestructive Evaluation, Volume 34
A2 - Chimenti, Dale E.
A2 - Bond, Leonard J.
PB - American Institute of Physics Inc.
T2 - 41st Annual Review of Progress in Quantitative Nondestructive Evaluation, QNDE 2014
Y2 - 20 July 2014 through 25 July 2014
ER -