Laser Generation of Ultrasound.
Abstract
The purpose of this report is to demonstrate a technique to generate high level, focused ultrasound by laser excitation of a material. The application is for ultrasonic nondestructive testing of components and possibly structures. The principle is that the laser energy is absorbed by a material and heats it, and the resulting thermal expansion generates a pressure wave in the material. An experimental and analytical study has been conducted into the use of carbon dioxide TEA lasers to generate ultrasonic waves. When the laser is fired at a plastic target, waves with a peak-to-peak pressure of 10 bars are generated. Teflon and Mylar were the most effective. There was no damage to the plastic, even after several hundred shots. This was not the case for glass or aluminum with a much smaller absorption depth and lower conversion efficiency. The sound wave could be directed by using an off-axis zone plate. This generated a 10 MHz tone burst, 45 deg, off-axis with a duration of 4 microsecs. A theoretical analysis of the phenomena is given which accounts for the waveforms and peak pressures measured.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1983
- Accession Number
- ADA138483
Entities
People
- J. A. Doughty
- M. J. Rudd
Organizations
- BBN Technologies