Chen Jian, Bai Xiaolong, Yang Keji, Ju Bing-Feng
The State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University, Hangzhou 310027, People's Republic of China; Centre for Optical and Electromagnetic Research, Zhejiang Provincial Key Laboratory for Sensing Technologies, State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310058, China.
The State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University, Hangzhou 310027, People's Republic of China.
Ultrasonics. 2015 Feb;56:505-11. doi: 10.1016/j.ultras.2014.09.019. Epub 2014 Oct 20.
To meet the need of efficient, comprehensive and automatic characterization of the properties of thin layers, a nondestructive method using ultrasonic testing to simultaneously measure thickness, density, sound velocity and attenuation through V(z,t) data, recorded by time-resolved acoustic microscopy is proposed. The theoretical reflection spectrum of the thin layer at normal incidence is established as a function of three dimensionless parameters. The measured reflection spectrum R(θ,ω) is obtained from V(z,t) data and the measured thickness is derived from the signals when the lens is focused on the front and back surface of the thin layer, which are picked up from the V(z,t) data. The density, sound velocity and attenuation are then determined by the measured thickness and inverse algorithm utilizing least squares method to fit the theoretical and measured reflection spectrum at normal incidence. It has the capability of simultaneously measuring thickness, density, sound velocity and attenuation of thin layer in a single V(z,t) acquisition. An example is given for a thin plate immersed in water and the results are satisfactory. The method greatly simplifies the measurement apparatus and procedures, which improves the efficiency and automation for simultaneous measurement of basic mechanical and geometrical properties of thin layers.
为满足对薄层特性进行高效、全面和自动表征的需求，提出了一种使用超声检测的无损方法，通过时间分辨声学显微镜记录的V(z,t)数据同时测量厚度、密度、声速和衰减。建立了薄层垂直入射时的理论反射谱作为三个无量纲参数的函数。从V(z,t)数据中获取测量的反射谱R(θ,ω)，并在透镜聚焦于薄层前后表面时从V(z,t)数据中提取信号来推导测量的厚度。然后利用测量的厚度和逆算法，采用最小二乘法拟合垂直入射时的理论和测量反射谱，确定密度、声速和衰减。它能够在单次采集V(z,t)数据时同时测量薄层的厚度、密度、声速和衰减。给出了一个浸在水中的薄板的示例，结果令人满意。该方法极大地简化了测量设备和程序，提高了同时测量薄层基本力学和几何特性的效率和自动化程度。
