Ding Wenxiang, Bavencoffe Maxime, Lethiecq Marc
IEEE Trans Ultrason Ferroelectr Freq Control. 2021 May;68(5):1819-1827. doi: 10.1109/TUFFC.2020.3047944. Epub 2021 Apr 26.
The transducer is an essential part of all ultrasonic systems used for applications such as medical diagnostics, therapy, nondestructive evaluation, and cleaning because its health condition is vital to their proper operation. Defects within the active element, backing or other constitutive elements, and loss of adhesion between layers can significantly weaken the performance of a transducer. The objective of this work is to determine procedures to monitor the behavior of a single-element probe during its lifetime and detect degradations before they significantly affect the performance of the system. To achieve this, electromechanical admittance (EMA)-based method is envisaged numerically and experimentally. A simplified single-element transducer consisting of a piezoceramic disk, a bonding layer, and a backing is studied and the influence of bonding delamination on EMA is investigated. This study considers three different types of delaminations, which are named, respectively, "center" (circular delamination from the center of the disk toward the peripheric zone), "peripheric" (annular delamination from the peripheric zone toward the center), and "wedge" (wedge-shaped delamination with a given angle). For each case, a numerical model based on the finite-element (FE) method is developed: a 2-D FE analysis is implemented for the first two types of delaminations, taking advantage of their axisymmetric structure, and "wedge" delamination is modeled in 3-D. Then, transducers with different shapes of 3-D printed backings are mounted and experiments are conducted using an impedance analyzer. Finally, experimental results are found to be in good agreement with numerical solutions and it shows that changes in EMA can particularly reveal the occurrence and extent of delamination in an ultrasound probe.
换能器是所有用于医学诊断、治疗、无损检测和清洗等应用的超声系统的重要组成部分，因为其健康状况对系统的正常运行至关重要。有源元件、背衬或其他组成元件内部的缺陷以及层间附着力的丧失会显著削弱换能器的性能。这项工作的目的是确定在单元素探头的使用寿命期间监测其行为的程序，并在其显著影响系统性能之前检测到性能退化。为了实现这一目标，设想了基于机电导纳（EMA）的数值和实验方法。研究了一种由压电陶瓷圆盘、粘结层和背衬组成的简化单元素换能器，并研究了粘结分层对EMA的影响。本研究考虑了三种不同类型的分层，分别命名为“中心”（从圆盘中心向周边区域的圆形分层）、“周边”（从周边区域向中心的环形分层）和“楔形”（具有给定角度的楔形分层）。对于每种情况，开发了基于有限元（FE）方法的数值模型：利用前两种分层的轴对称结构进行二维FE分析，对“楔形”分层进行三维建模。然后，安装具有不同形状的3D打印背衬的换能器，并使用阻抗分析仪进行实验。最后，实验结果与数值解吻合良好，结果表明EMA的变化能够特别揭示超声探头分层的发生情况和程度。
