Kazys R J, Mazeika L, Jasiuniene E
Ultrasound Institute, Kaunas University of Technology, Studentu 50, Kaunas, Lithuania.
Ultrasonics. 2004 Apr;42(1-9):267-71. doi: 10.1016/j.ultras.2004.01.043.
In the case of ultrasonic measurements in aggressive media piezoelectric elements of ultrasonic transducers are separated from a medium by thick protective layers, which may posses nonparallel front and back surfaces. This enables to reduce significantly the amplitude of multiple reflections, but the structure of the ultrasonic field radiated through a layer with nonparallel boundaries becomes complicated. The main objective of this paper is to present a method suitable for simulation of ultrasonic fields radiated through a layer with nonparallel boundaries in a transient mode. The proposed simulation method is based on the transformation of a multilayered medium into a virtual one without internal boundaries, equivalent to the actual medium from the point of a view of the relative times of arrival of direct and edge waves. The simulated ultrasonic fields in water are compared with the measurement results and a good correspondence between calculated and measured fields is obtained.
在腐蚀性介质中进行超声测量时，超声换能器的压电元件通过厚厚的保护层与介质隔开，这些保护层的前后表面可能不平行。这能够显著降低多次反射的幅度，但通过具有不平行边界的层辐射的超声场结构会变得复杂。本文的主要目的是提出一种适用于瞬态模式下模拟通过具有不平行边界的层辐射的超声场的方法。所提出的模拟方法基于将多层介质转换为无内部边界的虚拟介质，从直达波和边缘波的相对到达时间来看，该虚拟介质与实际介质等效。将水中模拟的超声场与测量结果进行比较，计算场与测量场之间取得了良好的一致性。
