Division of Electrical Systems and Optics, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
J Acoust Soc Am. 2011 Apr;129(4):1721-8. doi: 10.1121/1.3560945.
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.
已经开发出一种双频混合技术来测量由材料非线性引起的速度变化。该技术基于两个表面声波（SAW）之间的参数相互作用：由换能器产生的低频泵 SAW 和使用激光超声产生和检测的高频探测 SAW。泵 SAW 对探测 SAW 下方的材料施加应力。通过改变泵波和探测波之间的时间间隔来控制应力（通常 <5 MPa）。将非线性相互作用作为探测 SAW 的相位调制进行测量，并等同于速度变化。速度-应力关系用作材料非线性的度量。通过改变泵的频率来观察泵-探测相互作用的实验，并比较铝和熔融石英的非线性响应。实验表明，这两种材料具有相反的非线性响应，与先前发表的数据一致。该技术可以通过测量疲劳引起的非线性响应变化来应用于工程部件的寿命预测。
