Pulsed laser generation of ultrasound in a metal plate between the melting and ablation thresholds

Journal Article · Tue Mar 31 00:00:00 EDT 2015 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.4914749· OSTI ID:22391204

Every, A. G., E-mail: [e-mail] ^[1]; Utegulov, Z. N., E-mail: [e-mail] ^[2]; Veres, I. A., E-mail: [e-mail] ^[3]

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1. School of Physics, University of the Witwatersrand, PO Wits 2050 (South Africa)
2. Department of Physics, School of Science and Technology, Nazarbayev University, Astana 010000 (Kazakhstan)
3. RECENDT Research Center for Non Destructive Testing GmbH, A-4040 Linz (Austria)

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.

• OSTI ID: 22391204
• Journal Information: AIP Conference Proceedings, Vol. 1650, Issue 1; Conference: 41. Annual Review of Progress in Quantitative Nondestructive Evaluation, Boise, ID (United States), 20-25 Jul 2014; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
36 MATERIALS SCIENCE
AXIAL SYMMETRY
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
ELECTROMAGNETIC PULSES
EXCITATION
FINITE ELEMENT METHOD
GREEN FUNCTION
IRRADIATION
LASER-RADIATION HEATING
MELTING
MELTING POINTS
PLATES
SURFACE FORCES
SURFACES
TEMPERATURE DEPENDENCE
THERMAL CONDUCTION
THERMAL DIFFUSION
TUNGSTEN