【作者】 王伟；

【导师】 骆英；

【作者基本信息】 江苏大学 ， 测试计量技术及仪器， 2010， 硕士

【摘要】 超声相控阵无损检测技术通过对超声阵列换能器中各阵元进行相位控制,获得灵活可控的合成波束,从而实现高速、全方位和多角度地对机械结构及零部件进行损伤检测。它具有能够进行动态聚焦、可进行成像检测、可以检测复杂形状物体、能提高检测灵敏度、分辨力和信噪比的多项优点,近年来已成为国际无损检测界的研究热点。国内工业领域超声相控阵检测技术尚处在起步阶段,本课题以超声相控阵探伤理论为基础,进行了针对超声相控阵探伤系统中超声相控发射相关技术研究。本文在概述了超声相控阵的发展历史和发展现状后,说明了相控阵超声检测的研究意义以及超声相控阵探伤理论的相关知识,并详细阐述了超声相控阵系统中动态聚焦、相控延时等技术的原理和实现方法。超声波在介质中传播的时候,由于材料阻尼效应的存在,超声波的能量随着传播距离的增加将逐渐衰减,这将严重影响工件的损伤检出率。对此本文提出了利用缺陷的回波信息调整后续驱动器激励信号强度,从而达到缺陷处等强度效果的可控强度激发技术。设计了基于正交异性压电复合材料(OrthotropicPiezoelectric Composite Materials,OPCM)超声相控阵换能器的超声相控阵可控强度驱动系统,包括数字化超声发射波束形成、低噪声的程控放大和信号的高频功放,并对系统进行了初步的实验验证。对各阵元的发射相位延时进行精确控制是形成超声相控阵发射波束的关键环节,在相控发射中,需要精确控制相位延时,从而实现动态聚焦、偏转、声束形成等各种相控效果。理论分析显示,只有尽力提高相位延时的精度、分辨率和稳定性才能显著地抑制旁瓣。本文研究了基于现场可编程门阵列(Field Programmable Gate Array,FPGA)的超声相控延时算法和相位延时技术。分析了超声相控阵系统中线性阵列换能器相控偏转、相控聚焦延时算法,并利用DSP技术完成了相控算法的设计并通过仿真实验进行了验证。相控延时部分包括相控发射粗延时和相控发射细延时:相控发射粗延时通常基于系统时钟频率,在66MHz的系统时钟频率下,延时分辨率可达15ns;相控发射细延时利用直接数字合成技术(DDS)的数字化波形发射方式,采用数字波形相位差的方法来实现相位的细调,本系统中相位分辨率为0.35°,对应250kHz发射信号下3.75ns的相位延时。更多还原

【Abstract】 Ultrasonic phased array technique can help to achieve high-speed, all-round and multi-angle Nondestructive Testing by the flexible and controllable synthesized ultrasound beam, which is achieved by exciting each element of an ultrasonic array transducer with independent phase delay. Phased array ultrasonic testing can accomplish dynamic focusing, obtain visual image, inspect component of complex geometry. Also it can improve detection sensitivity, resolution and SNR, so it has recently been highly recognized in NDT research domain. This thesis studies several key technologies about ultrasonic phased array testing system based on the theory of ultrasonic phased array.In this thesis, firstly the history and current situation of ultrasonic testing is outlined. After that the merit of phased array ultrasonic testing are discussed, then the principles and realizations of several key technologies of phased array testing system such as phase delay and dynamic focus are explicated in details.The material damping effect prevents the transmission of the ultrasound. As the transmission distance increased, the ultrasound energy is gradually weakened. And it will seriously cut down the detection rate of the damage. The technology which can control the transducer’s driving strength according to the message of Echo is proposed in this paper. And the driving system based on OPCM transducer array is designed, including digital beam forming, low noise programmable amplification and the high frequency power amplifier.High precision ultrasonic transmission phased delay is the key technology in phased array ultrasonic beams. The basic link to achieve ultrasound phased array is phase delay. To achieve dynamic focus, deflection, beam forming, and other phased results need precise control of phase delay. Theoretical analysis showed that only to improve the precision, resolution and stability of phase delay. It can significantly inhibit side lobe. In the following chapter, the algorithm of the phase delay and the phase delay technique are discussed. Firstly, the time delay algorithm of linear array ultrasonic transducers was analyzed, which was described and validated with DSP Builder. The phased ultrasonic transmission circuit designed uses the waveform excitation method. With the waveform excitation, the system clock is combined with DDS (direct digital synthesis) to obtain a high-precision transmissions phase delay. The coarse transmission phase delay based on the system clock is 15ns. The fine phase delay based on the DDS can achieve 0.35°phase resolution, which equals 3.75 ns time resolution at a 250 kHz transmission frequency.更多还原