Determination of the acoustoelastic coefficient for surface acoustic waves using dynamic acoustoelastography: An alternative to static strain

Abstract

The third-order elastic constants of a material are believed to be sensitive to residual stress, fatigue, and creep damage. The acoustoelastic coefficient is directly related to these third-order elastic constants. Several techniques have been developed to monitor the acoustoelastic coefficient using ultrasound. In this article, two techniques to impose stress on a sample are compared, one using the classical method of applying a static strain using a bending jig and the other applying a dynamic stress due to the presence of an acoustic wave. Results on aluminum samples are compared. Both techniques are found to produce similar values for the acoustoelastic coefficient. The dynamic strain technique however has the advantages that it can be applied to large, real world components, in situ, while ensuring the measurement takes place in the nondestructive, elastic regime.

Review of Second Harmonic Generation Measurement Techniques for Material State Determination in Metals

“…Recent developments in laser instrumentation such as the CHeap Optical Transducer (CHOT) [111,112] where patterns are essentially deposited on the surface of a sample for laser generation or transmission, could eventually make laser interrogation portable and feasible in an in situ application. Laser-based generation and detection has also been utilized in vibro-acoustic measurements [112][113][114]. Signals from a laser detector are usually weak such that careful signal conditioning is essential to reliably extract the second harmonic signal.…”

Ultrasonic waves for materials evaluation in fatigue, thermal and corrosion damage: A review

“…Laser detection method is used in vibration-acoustic measurements [114,115]. Ultrasonic laser technique can analyse moving surfaces even in hazardous environments [116,107].…”

Dynamic Acousto-Elastic Testing

“…A slowly varying sinusoidal loading was proposed instead of a quasi-static stress that is varied in discrete steps [15]. Methods based on the interaction of two bulk elastic waves [16] or surface waves [17,18] were introduced, including a technique termed Dynamic Acousto-Elastic Testing (DAET) [19,20]. DAET is the dynamic analog of a conventional experiment of acousto-elasticity, though with significant differences.…”