基于物理聚焦的超声换能器及其探测系统实现方法

发布时间：2019-01-02 18:49

【摘要】：随着电子技术与自动化技术的不断发展,超声检测技术具有图像化、自动化、数字化、智能化以及极强的渗透力等特点,这已经成为现代检测技术的一个重要研究领域,超声换能器(也称探头)作为超声检测系统的重要组成部分,其探测性能直接影响到检测的精度与档次。由香农公式可知,超声传输的最大信息容量与超声换能器的信道传输带宽和信道信噪比相关。因此,超声换能器若具有较宽的频带与良好的信噪比,则其能获取最大的信息容量,但是现有的超声换能器存在着发射激励时间短、信号频带窄、反射回波信号小等不足,导致传输信息容量较小,探测性能并不高。因此,本文通过研究常见超声换能器的声场空间分布特性与在特定探测容器内对物理聚焦的非线性声场特性,提出一种基于物理聚焦的超声换能器实现方法,可令探测器的发射端局部压强变大,探头能量集中,检测精度得到提高。本文的主要工作有以下几个方面:1、深入研究常见超声换能器工作原理,并对单晶圆形声源、单晶矩形声源以及相控阵声源的声场空间分布与声束指向性特征进行理论分析,然后对其声压空间分布以及声束指向性进行模拟仿真,总结三者的声压空间分布特征、声束聚焦以及声束偏转的性能。2、对探测器模型内的非线性声场空间分布特征进行理论研究,推导出以锥形和指数形为探测器模型的声压幅值特性,并在此基础上提出一种基于物理聚焦的超声换能器实现方法,可克服直探头无法聚焦的缺陷,在保持探头发射功率以及保证最小总辐射量的基础上提高局部声压,可使检测范围缩减,超声探头能量汇聚,检测精度得到提高。同时结合通信系统组成原理,对超声检测系统的组成与工作原理进行详细研究。3、使用PZFLex软件对物理聚焦的超声换能器声场进行有限元数值声场模拟分析,并对换能器设置不同参数,分析探测器不同锥度与不同位置时对波束聚焦的效果。4、深入研究三种估计物理聚焦探测系统信道响应的频响特性算法,在此基础上对物理聚焦超声换能器在实际环境中进行频响特性测试,证明其在实际应用中的可操作性。
[Abstract]:With the development of electronic technology and automation technology, ultrasonic testing technology has the characteristics of image, automation, digitization, intelligence and strong permeability, which has become an important research field of modern detection technology. Ultrasonic transducer (also called probe) as an important part of ultrasonic detection system, its detection performance directly affects the accuracy and grade of detection. According to Shannon's formula, the maximum information capacity of ultrasonic transmission is related to the channel transmission bandwidth and channel signal-to-noise ratio of ultrasonic transducer. Therefore, if the ultrasonic transducer has a wide frequency band and good signal-to-noise ratio, it can obtain the maximum information capacity. However, the existing ultrasonic transducer has some shortcomings, such as short excitation time, narrow signal frequency band, small echo signal, etc. As a result, the transmission information capacity is small and the detection performance is not high. Therefore, by studying the spatial distribution of acoustic field and the nonlinear acoustic field characteristics of physical focusing in a specific detection vessel, this paper presents a method of ultrasonic transducer realization based on physical focusing. It can increase the local pressure of the detector, concentrate the probe energy, and improve the detection accuracy. The main work of this paper is as follows: 1. The working principle of common ultrasonic transducer is deeply studied, and the spatial distribution of sound field and the directivity of sound beam of single crystal circular sound source, single crystal rectangular sound source and phased array sound source are analyzed theoretically. Then, the spatial distribution of sound pressure and the directivity of sound beam are simulated and simulated, and the characteristics of spatial distribution of sound pressure, the focusing of sound beam and the deflection of sound beam are summarized. The spatial distribution characteristics of nonlinear acoustic field in the detector model are theoretically studied, and the acoustic pressure amplitude characteristics of the detector model with conical and exponential shapes are deduced, and a realization method of ultrasonic transducer based on physical focusing is proposed. It can overcome the defect that the straight probe can not be focused. The local sound pressure can be increased on the basis of keeping the transmission power of the probe and ensuring the minimum total radiation. The detection range can be reduced, the energy of the ultrasonic probe can be converged, and the detection accuracy can be improved. At the same time, combined with the principle of communication system composition, the composition and working principle of ultrasonic detection system are studied in detail. 3. The finite element numerical sound field simulation analysis of the ultrasonic transducer with physical focus is carried out by using PZFLex software. At the same time, different parameters are set for the transducer to analyze the effect of beam focusing when the detector has different taper and position. 4. Three frequency response algorithms for estimating the channel response of the physical focusing detection system are studied in depth. On this basis, the frequency response characteristics of the physical focused ultrasonic transducer are tested in the actual environment, which proves its operability in practical application.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB552

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