Montero de Espinosa Francisco, Martínez Oscar, Elvira Segura Luis, Gómez-Ullate Luis
Instituto de Acústica, Spanish Council Scientific Research (CSIC), Madrid, Spain.
IEEE Trans Ultrason Ferroelectr Freq Control. 2005 Jun;52(6):980-6. doi: 10.1109/tuffc.2005.1504020.
Harmonic imaging (HI) has emerged as a very promising tool for medical imaging, although there has been little published work using this technique in ultrasonic nondestructive testing (NDT). The core of the technique, which uses nonlinear propagation effects arising in the medium due to the microstructure or the existence of defects, is the ability to design transducers capable of emitting at one frequency and receiving at twice this frequency. The transducers that have been used so far are usually double crystal configurations with coaxial geometry, and commonly using a disc surrounded by a ring. Such a geometry permits the design of broadband transducers if each transducer element is adapted to the medium with its corresponding matching layers. Nevertheless, the different geometry of the emission and reception apertures creates difficulties when resolving the images. In this work, a new transducer design with different emission and reception apertures is resented. It makes use of the traditional construction procedures used to make piezocomposite transducers and the well-known theory of the mode coupling in piezoelectric resonators when the lateral dimensions are comparable with the thickness of the piezoceramic. In this work the design, construction, and characterization of a prototype to be used in NDT of metallic materials is presented. The acoustic field is calculated using water as a propagation medium, and these theoretical predictions then are compared with the experimental measurements. The predicted acoustic performances for the case of propagation in stainless steel are shown.
谐波成像（HI）已成为医学成像中一种非常有前景的工具，尽管在超声无损检测（NDT）中使用该技术的已发表作品很少。该技术的核心是能够设计出能够以一个频率发射并以该频率两倍接收的换能器，它利用了由于微观结构或缺陷的存在而在介质中产生的非线性传播效应。到目前为止所使用的换能器通常是具有同轴几何结构的双晶配置，并且通常使用由环包围的圆盘。如果每个换能器元件都通过其相应的匹配层与介质相适配，那么这种几何结构允许设计宽带换能器。然而，发射和接收孔径的不同几何结构在解析图像时会产生困难。在这项工作中，提出了一种具有不同发射和接收孔径的新型换能器设计。它利用了制造压电复合换能器所使用的传统制造工艺以及当横向尺寸与压电陶瓷的厚度相当时压电谐振器中众所周知的模式耦合理论。在这项工作中，展示了一种用于金属材料无损检测的原型的设计、制造和特性。使用水作为传播介质计算声场，然后将这些理论预测与实验测量结果进行比较。展示了在不锈钢中传播情况下的预测声学性能。
