Analysis of laser ultrasonic measurements of surface waves on elastic spheres

Conference · Tue Jan 01 04:00:00 EST 1991

OSTI ID:6149585

Koo, L S; Telschow, K L

In conventional ultrasonic nondestructive evaluation studies, piezoelectric transducers are used to generate sound waves in solids via a couplant that transmits the mechanical motions. In recent years, a different method of generating sound in solids, pulsed laser heating, was introduced by White. This method is noncontacting, requires no coupling medium, and operates directly on the surface of the specimen. Noncontacting ultrasonic detection using laser interferometers of several types has also been developed. Laser techniques can achieve essentially point source and point detection of ultrasonic motion through focusing. Laser ultrasonics can, therefore, be used on objects with complex shapes, e.g. curved surfaces, and are applicable to material shapes more commonly found in industry. Often the goal of ultrasonic measurements is to determine material properties such as Lame's elastic constants. The conventional approach measures longitudinal and shear wave speeds between two parallel flat surfaces. The work reported here demonstrates the versatility of laser ultrasonics by directly measuring the surface motion of a solid sphere generated by ablation from a pulsed laser beam in the ablation regime. The results compare well with elastodynamic theoretical calculations, where the ablation source is approximated well with elastodynamic theoretical calculations, where the ablation source is approximated as a normal impulse on the surface. This work suggests that an algorithm could be formulated to measure elastic properties of targets with curved surfaces. 15 refs., 5 figs.

• Research Organization: EG and G Idaho, Inc., Idaho Falls, ID (United States)
• Sponsoring Organization: DOI; Department of the Interior, Washington, DC (United States)
• DOE Contract Number: AC07-76ID01570
• OSTI ID: 6149585
• Report Number(s): EGG-M-91205; CONF-9107112--5; ON: DE92003332
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420500* -- Engineering-- Materials Testing
ACOUSTIC TESTING
ELECTROMAGNETIC RADIATION
INTERFEROMETERS
LASER RADIATION
MATERIALS TESTING
MEASURING INSTRUMENTS
NONDESTRUCTIVE TESTING
RADIATIONS
RAYLEIGH WAVES
SEISMIC SURFACE WAVES
SEISMIC WAVES
SOLIDS
SOUND WAVES
SPHERES
TESTING
ULTRASONIC TESTING
ULTRASONIC WAVES