A novel technique for the measurement of the acoustic properties of a thin linear-viscoelastic layer using a planar ultrasonic transducer
A novel technique for the measurement of the acoustic properties of a thin linear-viscoelastic layer using a planar ultrasonic transducer
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DOI：
10.1088/0957-0233/24/12/125602
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发表时间：
2013-12
影响因子：
2.4
通讯作者：
Xiaolong Bai;Zeqing Sun;Jian Chen;Bingfeng Ju
中科院分区：
文献类型：
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作者：
Xiaolong Bai;Zeqing Sun;Jian Chen;Bingfeng Ju
薄的线性粘弹性层如薄膜和涂层具有许多应用。同时测量薄层的多种声学特性对于保证薄层的质量具有重要意义。本文提出了一种新的方法，用于同时测定薄线性粘弹性层的三个声学特性，即声阻抗Z2、渡越时间Δt2和衰减系数α2。一个平面超声换能器，在正常的入射，是用来询问薄层，所有的反射是由同一个换能器接收。首先，通过从所有接收到的回波中减去来自薄层的前表面的回波来获得Z2的最佳估计。在确定声阻抗之后，如果减去来自薄层后表面的回波而没有任何余数，则可以找到Δt2和α2的最佳估计。该技术避免了传统测量技术中经常遇到的主要基于将实验反射光谱拟合到理论模型的收敛问题。新技术的有效性首先通过数值模拟得到证实，然后通过实验应用到四个薄的线性粘弹性层。实验结果表明，Z2和Δt2可以准确地得到，而α2的确定误差较大，这是由于超声回波对该特性不敏感。在实验中测量的三个声学性质Z2、Δt2和α2的相对不确定度分别为1.2%、1.5%和5%左右，主要是由这种测量技术的原理引起的。
Thin linear-viscoelastic layers such as films and coatings have many applications. Simultaneous measurement of the multiple acoustic properties of a thin layer is of great importance in ensuring its quality. In this paper, a novel technique is proposed for the simultaneous determination of the three acoustic properties of a thin linear-viscoelastic layer, namely the acoustic impedance Z2, the time-of-flight Δt2 and the attenuation coefficient α2. A planar ultrasonic transducer, at normal incidence, is used to interrogate the thin layer, and all the reflections are received by the same transducer. Firstly, an optimal estimate of Z2 is obtained by subtracting the echo from the front surface of the thin layer from all the received echoes. After this determination of the acoustic impedance, optimal estimates for Δt2 and α2 can be found if the echo from the back surface of the thin layer is subtracted without any remainder. This technique avoids the convergence problem that is frequently encountered in the traditional measurement techniques based mainly on fitting the experimental reflection spectrum to a theoretical model. The effectiveness of the new technique is firstly confirmed by numerical simulation and then by experimental application to four thin linear-viscoelastic layers. Experimental results show that Z2 and Δt2 can be obtained accurately while the error in determining of α2 is relatively large due to the insensitivity of the ultrasonic echoes to that property. The relative uncertainties in determining the three acoustic properties Z2, Δt2 and α2 in our experiments are around 1.2%, 1.5%, 5%, respectively, mainly arising from the principle of this measurement technique.