便携式交变电磁场检测仪器的研制及试验

发布时间：2018-06-18 14:20

本文选题：交变电磁场检测 + 加法器　；参考：《南昌航空大学》2016年硕士论文

【摘要】：交变电磁场检测技术简称为ACFM技术,是一种逐渐兴起的数字化电磁无损检测技术。该技术通过在金属表面感应出交变电场,检测缺陷对交变电场的扰动所形成的感应磁场来精确测定待检金属试件表面及近表面缺陷的长度、深度等信息。近年来该技术以其精度高、操作简单等优点得以在无损检测领域内快速发展。本文根据法拉第电磁感应定理以及麦克斯韦方程组对ACFM技术进行了理论分析与数学建模。依据理论分析及数学模型组建了专用于ACFM技术的实验平台,通过该实验平台探索了不同材料的最佳激励频率,研究了待检试件表面各点各方向上感应磁场的磁感应强度、相位同缺陷的大小、深度的关系。检测不同的金属材质需要不同频率的激励,目前的检测仪器不具备更改激励频率和激励电压的功能。本文设计的正弦信号激励电路由直接数字式频率合成器、低通滤波器、程控放大、功率放大等部分组成,克服了以往ACFM检测仪激励源频率、电压不可调的缺点。经过试验验证,该电路产生的激励频率、电压稳定可调,输出电流大,信噪比高。满足了交变电磁场检测系统对激励源的要求。为提高抵抗待检金属剩磁的能力,满足处理不同频率信号、以及绘制蝶形图的要求,该电路使用双线圈拾取感应磁场信号,克服了磁阻传感器量程小、易受剩磁干扰的缺点。该仪器使用开关电容滤波器对线圈采集到的感应磁场信号进行带通滤波,具有处理不同频率信号的能力。使用加法器对垂直于待检试件表面的感应磁场信号进行相位调整,使缺陷两端该方向上的感应磁场相位相同,解决了因相位不同带来的蝶形图绘制不正确的问题。该电路可检测不同材质的金属,具有检测精度高,工作稳定可靠,抗干扰能力强的特点。
[Abstract]:Alternating electromagnetic field detection technology is called ACFM technology. It is an emerging digital electromagnetic nondestructive testing technology. By sensing an alternating electric field on a metal surface, the technique detects the induction magnetic field caused by the disturbance of the alternating electric field to determine the length, depth and other information of the surface and near surface defects of the metal specimen to be examined. In recent years, this technology has developed rapidly in the field of nondestructive testing with its advantages of high precision and simple operation. In this paper, the theoretical analysis and mathematical modeling of ACFM technology are carried out based on the Faraday electromagnetic induction theorem and the Maxwell equation group. The experimental platform for ACFM technology is built on the basis of theoretical analysis and mathematical model group. The experimental platform has explored the optimum excitation frequency of different materials, and studied the relationship between the magnetic induction intensity of the induction magnetic field in each direction of the surface of the test specimen, the relation between the phase and the size of the defect and the depth. The detection of different metal material needs different frequency excitation, and the current detecting instrument does not have the work to change the excitation frequency and the excitation voltage. The sinusoidal signal excitation circuit designed in this paper is composed of direct digital synthesizer, low pass filter, program control amplification, power amplification and so on. It overcomes the shortcomings of the previous ACFM detector, which has the excitation frequency, the voltage stability, the voltage stability, the output current and the signal to noise ratio. To meet the requirements of the excitation source for the alternating electromagnetic field detection system, in order to improve the ability to resist the remanent magnetic remanence, to meet the processing of different frequency signals and to draw a butterfly chart, the circuit uses a double loop to pick up the induction magnetic field signal, which overcomes the shortcomings of the small range of the magnetoresistance sensor and easy to be disturbed by the remanence. The instrument uses the switch. The capacitive filter has a band pass filter for the induction magnetic field signals collected by the coil, and has the ability to deal with different frequency signals. Using an adder to adjust the magnetic field signal perpendicular to the surface of the test piece to make the same phase of the induction magnetic field on the two ends of the defect, and solve the butterfly figure drawing caused by the phase difference. The circuit can detect metal with different materials, and has the characteristics of high detection accuracy, stable and reliable work, and strong anti-interference ability.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TH878.3

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