Abstract

The most popular transducers used in ultrasonic testing are piezoelectric transducers. The three major components of a piezoelectric transducer are the crystal, backing material, and matching layer. Traditionally, the optimal combination of these components is either found by trial and error or by using simple analytical models. These procedures make it difficult or even impossible to find the cause of poor performance or deficiencies in manufactured transducers. Finite element modeling is an alternative method that can be used for designing optimal piezoelectric transducers while avoiding limitations set forth by one-dimensional analytical models. In this paper, the effects of various parameters on the performance of a piezoelectric transducer are investigated by finite element simulations and experimental measurements. The aim is implementation of a design tool for optimizing the performance of a custom-made ultrasonic transducer. The complete transducer structure, including the piezoelectric disk, backing material, and matching layer are modeled in both transmit and receive modes. In most of the previous finite element models, either distributed force or distributed displacement is applied to the nodes to simulate the effect of the piezoelectric crystal. However, in this paper, actual piezoelectric elements are used to generate ultrasonic waves. Consequently, the input to this model is an electrical pulse, and the output is an electrical voltage. This is exactly like what we have in real world. Therefore, the performance of this model is exactly the same as a real piezoelectric transducer. The results show that undesired echoes can be eliminated by increasing the attenuation of the backing material. Moreover, for matching layer impedances less than 5 MRayl, with an increase in impedance value, both the transducer bandwidth and the echo amplitude increase. For matching layer impedances higher than 5 MRayl, the frequency spectrum is double-humped, and detection of flaws is less accurate. Experimental measurements conducted on an in-house built transducer are found to be in good agreement with simulation results.

中文翻译：

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通过有限元建模研究压电超声换能器的性能

摘要

超声波检测中最常用的换能器是压电换能器。压电换能器的三个主要组件是晶体、背衬材料和匹配层。传统上，这些组件的最佳组合是通过反复试验或使用简单的分析模型找到的。这些程序使得很难甚至不可能找到制造传感器性能不佳或缺陷的原因。有限元建模是一种替代方法，可用于设计最佳压电换能器，同时避免由一维分析模型提出的限制。在本文中，通过有限元模拟和实验测量研究了各种参数对压电换能器性能的影响。目的是实现用于优化定制超声波换能器性能的设计工具。完整的换能器结构，包括压电盘、背衬材料和匹配层，都在发射和接收模式下建模。在以前的大多数有限元模型中，对节点施加分布力或分布位移来模拟压电晶体的效果。然而，在本文中，使用实际的压电元件来产生超声波。因此，该模型的输入是电脉冲，输出是电压。这与我们在现实世界中所拥有的完全一样。因此，该模型的性能与真正的压电换能器完全相同。结果表明，可以通过增加背衬材料的衰减来消除不需要的回声。此外，对于小于 5 MRayl 的匹配层阻抗，随着阻抗值的增加，换能器带宽和回波幅度都增加。对于高于 5 MRayl 的匹配层阻抗，频谱是双峰的，缺陷检测不太准确。发现在内部构建的换能器上进行的实验测量与模拟结果非常一致。并且缺陷的检测不太准确。发现在内部构建的换能器上进行的实验测量与模拟结果非常一致。并且缺陷的检测不太准确。发现在内部构建的换能器上进行的实验测量与模拟结果非常一致。