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超声波探伤仪及数字化超声波探伤仪 总被引:6,自引:3,他引:6
1 常规超声波探伤仪的基本结构超声波探伤仪的基本结构框图如图1所示.探伤仪有同步电路、发射电路、接收电路、时基电路、显示器、电源和超声波换能器等几个部分组成.同步电路:产生使整个仪器协调工作的同步脉冲信号,以同步触发发射电路、时基电路及闸门电路等部分,以便在显示屏上稳定地显示所需观察的超声回波脉冲.发射电路:产生高压(负)脉冲,激励超声波换能器产生高频振荡,从而形成脉冲超声波,经耦合层进人被检构件和材料.接收电路:从超声探头接收到的微小超声信号,经压电晶片转换为微弱的电脉冲信号,经接收电路放大后显示在示波器上.常规超声波探伤仪接收电路由衰减器、高频放大器、检波和视频放大器等几个部分组成.调节衰减器实际上是调节放大器的增益,以便使所观察的回波以合适的高度显示在示波屏上.时基电路:实际是方波形成电路和锯齿波形成 相似文献
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研制了一台相位成象声显微镜,可对样品反射信号的相位信息进行成象.其电路由插入PC机内的超高速A/D卡和快脉冲产生和接收卡组成.A/D卡采样率>109次/s,使用了周边元件扩展接口(PCI)总线和现场可编程门阵列(FPGA)技术;脉冲产生和接收卡能可靠接收、放大未经检波的回波,因而可精确获取未经检波的回波信号.然后利用软件完成相位检测及图象显示,还可通过数字检波获得样品幅度象.仪器工作频率为2~50MHz;可实时显示检测样品的A扫描及相位或幅度象.该仪器在微米级薄膜厚度、形状的测量和三维成象以及焊接质量的检测等方面具有独特功能.该机体积小、功能强、成本低,具有广阔的开发应用前景. 相似文献
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在流量、压力和温度控制中,系统会受到一定的干扰,同时具有低频信号反馈的特点,采用 A/D 转换难以达到抗干扰的要求。为此采用一种新的脉宽调制( PWM) 电路实现转换,将被测模拟信号经过放大、整流以及滤波处理后,与三角波调制信号进行比较,得到 PWM 信号,该信号的占空比与被测量信号的大小成正比。微处理器只要采用定时器测量占空比,就可以计算出输入的模拟信号,其 A/D 转换精度为处理器时钟周期和三角波周期的比值,三角波周期越低,精度越高。这种模数转换电路简单,抗干扰能力强,特别适合低频信号反馈的模数转换。实验结果表明,可以较低成本达到较高转换位数的精度效果。 相似文献
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介绍了超声信号数字频谱分析的原理和实施方法。即通过信号采样、A/D转换、FFT变换等可获得换能器及超声回波的频谱特性参数。介绍了德国KK公司和南昌航院自制探头的波形和频谱图,认为根据频谱测量结果,适当改变有关参数就有可能研制高性能换量器。 相似文献
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目前超声探伤中使用最广泛的是A型显示脉冲探伤仪,它通过探头向工件周期性地发射不连续且频率不变的超声波,根据超声波在工件中的传播时间及回波幅度判断其有无缺陷和缺陷位置及大小。超声波传播时间的记录是通过扫描电路实现的。 相似文献
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提出了一种基于AD9273的高集成度超声相控阵检测系统设计方案。在传统超声相控阵检测系统的基础上,利用新型高集成度芯片AD9273和HV748完成32通道高压发射电路和接收采集电路设计;采用FPGA子系统结合ARM平台的方式构成系统数字信号处理的核心;采用数字正交包络检波技术完成接收波束成形。系统满足探伤的实时、高速的要求。系统在小型化和数字化方面有显著提高,可为便携式超声相控阵检测系统设计奠定基础。 相似文献
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Measuring amplitude and phase of continuous ultrasonic waves with a lock-in amplifier is shown to give similarly sensitive indicators of concrete damage as pulsed coda wave analysis, but maintains its sensitivity at considerably much lower signal levels. Continuous and pulsed measurements were performed on a concrete slab subjected to cyclically increased damage level. In the unloaded phase each measurement type was performed at varying transmit signal levels. The result indicates the possibility of using a larger distance between transducers in high frequency health monitoring systems of concrete structures, where attenuation of propagating waves is strong. 相似文献
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A contribution to the applicability of complex wavelet analysis of ultrasonic signals 总被引:4,自引:0,他引:4
Ultrasonic signal is always composed of a series of transient feedback impulsive waves, which are created during the propagation of ultrasonic energy when it meets the discontinuities within the material, such as inclusions, voids, micro-cracks, the surface of the object being inspected and so on. Complex wavelet based envelope detection method was designed to extract the impulsive features contained in the signal. The complex wavelet based correlation analysis was further proposed for distinguishing the ‘real impulsive waveform’ that indicates the object being searched from a number of unrecognized disturbing waveforms also presented in the signal. The effectiveness of both methods was proved by practical experiments on a common tube sample. The experiments proved that, by using the proposed methods, the impulsive waveform that really indicates the end surface of the tube could be distinguished successfully. With the aid of the analysed results and the calibration equation, the relative distance between the position where the transducer was placed and the end surface of the tube could be identified correctly. It is believed that the proposed methods will be widely applied to the analysis of ultrasonic signals. 相似文献
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Designing amplifiers with very low output noise for high impedance piezoelectric transducers 总被引:2,自引:1,他引:1
Y. Yaez M.J. Garcia-Hernandez J. Salazar A. Turo J.A. Chavez 《NDT & E International》2005,38(6):491-496
An analytical output noise voltage model of an ultra low noise amplifier for high impedance ultrasonic transducers is presented. Operational amplifier with low input bias current is needed to avoid using compensation resistance that considerably increases the noise at the input of the operational amplifier. The proposed analytical model, including the ultrasonic transducer, provides a useful tool to design, compare and select component values. 相似文献
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超声换能器频率特性和探伤仪接收放大器性能及测试方法 总被引:1,自引:1,他引:0
讨论当前国内超声换能器频率特性及探伤仪接收放大器的性能对探伤的影响,并提出了测试方法以提高缺陷定量的准确性及系统的一致性。 相似文献
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