相控阵超声缺陷检测信号处理研究

发布时间：2018-06-10 06:57

  本文选题：超声相控阵 + Nios　； 参考：《天津大学》2014年硕士论文

【摘要】：超声相控阵技术因其扫查速度快、声束控制灵活、检测灵敏度高、适用范围广等多项优点而被推广使用,并逐渐成为国际无损检测领域研究热点。本文以相控阵超声缺陷检测信号处理相关技术为主线,先从硬件和软件方面实现超声信号的获取,为自主研发超声相控阵设备奠定了基础;紧接着对缺陷信号的处理方法进行了研究和实验验证,最后将分形技术应用于提取近表面缺陷信号特征并实现缺陷识别。相控阵超声缺陷检测中首先要实现的是声波的相控发射与接收,本文建立了带楔块超声相控阵检测的声束偏转和声束聚焦模型,并计算两种模型的延迟法则,通过仿真说明了延迟法则相控技术对声束合成的影响,分析了超声相控阵缺陷检测的成像方法。为实现缺陷信号的获取,提出了基于FPGA嵌入式处理器的超声信号采集方案,通过在FPGA内部构建以Nios Ⅱ软核为处理器的片上可编程系统(SOPC,System On a Programmable Chip),实现对超声信号采集A/D芯片以及信号传输USB芯片的控制,构建了嵌入式超声信号采集平台。针对全矩阵捕获(FMC,Full Matrix Capture)这一获取缺陷全面信息的扫查方式,对Multi2000系统进行软件开发以获取全矩阵数据,提出了运用全聚焦成像算法(TFM,Total Focusing Methods)对全矩阵数据进行后处理。为排除实验外界干扰对算法验证的影响,仿真了全矩阵捕获过程。对获得的仿真和实验数据分别用平面B扫、聚焦B扫和TFM的成像方法处理,结果表明,全聚焦成像的方法有助于提高缺陷成像分辨率。最后本文针对工业相控阵超声缺陷检测过程中近表面缺陷的漏检问题,提出运用分形理论的方法对实验获得的A-Scan缺陷信号进行处理,计算其盒计数维数,通过统计分析证明了分形理论可应用于近表面缺陷A-Scan信号处理,盒维数特征可用于识别近表面缺陷。
[Abstract]:Ultrasonic phased array technology has been widely used because of its advantages of fast scanning speed, flexible control of sound beam, high detection sensitivity, wide range of application and so on, and has gradually become a hot spot in the field of international nondestructive testing (NDT). In this paper, the ultrasonic signal processing technology of phased array ultrasonic defect detection is the main line, first from the hardware and software to achieve ultrasonic signal acquisition, for the development of ultrasonic phased array equipment laid the foundation; Then, the processing method of defect signal is studied and verified by experiments. Finally, fractal technique is applied to extract the feature of near-surface defect signal and to realize defect recognition. The first thing to be realized in the ultrasonic defect detection of phased array is to transmit and receive the sound wave. In this paper, the acoustic beam deflection and the focusing model of ultrasonic phased array with wedge are established, and the delay rules of the two models are calculated. The effect of delay rule phase control technology on acoustic beam synthesis is illustrated by simulation, and the imaging method of ultrasonic phased array defect detection is analyzed. In order to obtain defect signal, an ultrasonic signal acquisition scheme based on FPGA embedded processor is proposed. An embedded ultrasonic signal acquisition platform is constructed by constructing a programmable system on a Programmable ChipP with Nios 鈪，

本文编号：2002364