Measurement of material nonlinearity using surface acoustic wave parametric interaction and laser ultrasonics

Abstract

A dual frequency mixing technique has been developed for measuring velocity changes caused by material nonlinearity. The technique is based on the parametric interaction between two surface acoustic waves (SAWs): The low frequency pump SAW generated by a transducer and the high frequency probe SAW generated and detected using laser ultrasonics. The pump SAW stresses the material under the probe SAW. The stress (typically <5 MPa) is controlled by varying the timing between the pump and probe waves. The nonlinear interaction is measured as a phase modulation of the probe SAW and equated to a velocity change. The velocity-stress relationship is used as a measure of material nonlinearity. Experiments were conducted to observe the pump-probe interaction by changing the pump frequency and compare the nonlinear response of aluminum and fused silica. Experiments showed these two materials had opposite nonlinear responses, consistent with previously published data. The technique could be applied to life-time predictions of engineered components by measuring changes in nonlinear response caused by fatigue.

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].…”

Imaging of transient surface acoustic waves by full-field photorefractive interferometry

“…They have attracted much attention, by virtue of their non-contact, non-destructive nature and high flexibility of implementation. [1][2][3][4][5][6] Moreover, possible bandwidth limitations of electronic detection can be circumvented by making use of an optical delay line. 7,8 Optical detection of SAW induced displacements at a single location can be done with high sensitivity, e.g., by interferometric detection, 9,10 laser beam deflection, 11,12 modulated optical reflection, 13 or heterodyne diffraction detection.…”

“…14 Single SAW signals contain valuable information on the SAW velocity and attenuation, which are related to the elasticity and microstructure of the materials. 6,9,12,15,16 By analyzing signal contributions due to SAW mode conversion at defect related elastic discontinuities along the path between the excitation a) Authors to whom correspondence should be addressed. Electronic addresses: xdxu@nju.edu.cn and christ.glorieux@fys.kuleuven.be and detection locations, the presence and the size of the defects can also be assessed.…”

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

“…It measures the velocity change of a high frequency probe wave due to the induced stress from a second large amplitude low frequency pump wave. 19,25 By controlling the delay between the generation of the two waves, their interaction point, hence the applied stress, can be selected. The duration of the probe wave packet (T packet ) is short compared to the period of the pump wave (T pump ): T packet < 1=4T pump .…”