Measurement of acoustoelastic effect of Rayleigh surface waves using laser ultrasonics
- Sandia National Labs., Livermore, CA (United States). Materials and Engineering Sciences Center
- Cornell Univ., Ithaca, NY (United States). Electrical Engineering Dept.
The acoustoelastic effect refers to the fact that elastic wave velocities vary with stress. Measurements of the change in stress induced velocity yield information which leads to the determination of stresses. Some work has been done to explore the possibility of using ultrasonic waves, including bulk longitudinal and shear waves as well as surface waves, for the nondestructive evaluation of stresses. This paper focuses on Rayleigh surface waves, which have the advantage of detecting both surface stresses and stress gradients. Piezoelectric or electromagnetic acoustic transducers have been used for the application of Rayleigh waves in the acoustoelastic measurement of stress. The size of these transducers and their fixtures limit the distance between transducers. Sharp edge wedges are usually bound to the pick-up piezoelectric transducers, known as the Rayleigh or surface wave device (SWD), to provide a better spatial resolution when the stress field is not uniform. The smallest distance reported is 11 mm. On the other hand, acoustic microscopes (AM) can measure localized stress for a very small area, from 30 {micro}m to 2 mm. Both SWD and AM method may lack the agility required for general applications. Laser ultrasonics (LU) is a method for optical generation and detection of ultrasound. The generation and detection areas can be focused to very small spot sizes, less than 1 mm, which allow velocity measurements to be made over a path length of a few millimeters. The LU technique is non-contact and can be applied remotely; it has many potential applications. The authors used the LU technique to measure the acoustoelastic behavior of an aluminum alloy, A16061-T6.
- Research Organization:
- Sandia National Labs., Livermore, CA (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 642758
- Report Number(s):
- SAND--98-8417C; ON: DE98050607
- Country of Publication:
- United States
- Language:
- English
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