毫瓦级标准压电超声换能器的研制与性能测试

发布时间：2018-06-25 12:53

本文选题：超声换能器 + 铌酸锂　；参考：《郑州大学》2014年硕士论文

【摘要】：在超声诊断和治疗中，由于超声功率过大可能引起人体细胞破坏性形变的空化效应，超声诊断安全性逐渐成为医用超声的重要问题。在我国，计量部门主要采用毫瓦级或者瓦级超声功率计来检测各种医用超声设备的输出功率，而超声功率计则需要通过上一级计量部门进行定期检定或校准，可见，超声量值传递的准确性为超声技术使用的可靠性提供了保障。本文从压电超声换能器的工作原理出发，理论上分析了铌酸锂单晶材料的压电机理，压电振子的振动模式和压电方程，并由压电方程推导出压电换能器在厚度伸缩振动模式下的机电等效电路；在压电材料的选择方面，研究了铌酸锂单晶不同切割方向的振动特性和机电耦合系数，确定压电晶片的最佳切型及振动模式；在压电振子的设计方面，合理设计振子厚度与直径的尺寸比例，并用溅射法在压电振子表面镀上金层电极薄膜；在换能器的制作方面，从换能器整体装配和电极焊接角度出发，设计了超声换能器的外壳，有效地降低了装配难度。本文严格遵循“毫瓦级超声功率计检定规程”的要求，研制了标称频率为5MHz的标准超声换能器。铌酸锂压电超声换能器的性能测试主要包括两部分，分别为声场特性测试和超声输出功率的标定。声场特性测试原理为水听器法，本文设计了确定换能器工作频率的实验，，并测试了其在工作频率下的声场空间分布特性。按照毫瓦级标准超声源的标定要求，在毫瓦级国家基准装置上，采用辐射力天平法测量所研制的超声换能器的输出功率，并对实验结果进行了不确定度评定。实验结果表明，所研制的换能器满足“毫瓦级标准超声源”的要求，达到了预期设计指标，一定程度上克服了标准石英晶体超声换能器的缺点。
[Abstract]:In ultrasonic diagnosis and treatment, the supersonic power may cause the cavitation effect of the destructive deformation of human cells. The safety of ultrasonic diagnosis has gradually become an important problem of medical ultrasound. In our country, the Metrology Department mainly uses milliwatt grade or watt grade ultrasonic power meter to detect the output power of various medical ultrasonic equipment, and the ultrasonic work The rate meter needs to be regularly calibrated or calibrated through the upper level measurement department. It can be seen that the accuracy of the transmission of ultrasonic values provides a guarantee for the reliability of ultrasonic technology.
Based on the working principle of the piezoelectric ultrasonic transducer, the piezoelectric mechanism of the lithium niobate single crystal material, the vibration mode and the piezoelectric equation of the piezoelectric vibrator are analyzed theoretically, and the electromechanical equivalent circuit of the piezoelectric transducer under the thickness expansion vibration mode is derived from the piezoelectric equation. The optimum cutting and vibration modes of the piezoelectric wafers are determined by the vibration characteristics and the electromechanical coupling coefficient of the crystal. In the design of the piezoelectric vibrator, the size ratio of the thickness and diameter of the vibrator is rationally designed, and the gold layer electrode film is plated on the surface of the piezoelectric vibrator by sputtering; the transducer is made from the transducer as a whole. In the angle of assembly and electrode welding, the outer shell of the ultrasonic transducer is designed, which effectively reduces the difficulty of assembly. In this paper, a standard ultrasonic transducer with a nominal frequency of 5MHz is developed in strict compliance with the requirements of the "milliwatt ultrasonic power meter verification regulation".
The performance test of the piezoelectric ultrasonic transducer for lithium niobate mainly consists of two parts, which are the sound field characteristic test and the calibration of the ultrasonic output power respectively. The sound field characteristic test principle is the hydrophone method. This paper designs the experiment to determine the working frequency of the transducer, and tests the spatial distribution characteristics of the sound field at the working frequency. The calibration requirement of the ultrasonic source is to measure the output power of the ultrasonic transducer developed by the radiation force balance method on the milliwatt national benchmark device, and evaluate the uncertainty of the experimental results. The experimental results show that the developed transducer meets the requirements of the "milliwatt standard super sound source" and has reached the expected design index. It overcomes the shortcomings of the standard quartz crystal transducer.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB552

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