【作者】 李桂颖；

【导师】 高松巍；

【作者基本信息】 沈阳工业大学 ， 测试计量技术及仪器， 2012， 硕士

【摘要】 电磁超声技术以其非接触、可以产生各种波形、能够在恶劣环境中工作、能对移动物体进行准确检测等优点成为工业生产中重要的检测手段之一。厚度的测量是检测物体的重要指标之一,尤其在金属板材检测方面,知晓板材的精确壁厚对于保障其质量与安全至关重要。本文从理论及实验两方面研究了电磁超声波金属板厚度测量问题,并对电磁超声采集信号进行软件上的处理。理论方面,本文通过研究电磁超声检测的基本原理,选取横波作为测厚的波的类型,确定了产生横波的测厚换能器结构形式。利用ANSYS有限元分析软件对确定形式的金属板测厚换能器进行了仿真分析。对于非铁磁性材料,仿真采用电磁结构耦合分析方法,分别得出了试件所受洛伦兹力及试件上的质点位移。通过分析多个质点位移值得出超声波在被测试件中主要传播角度。针对参数改变对超声波传播的影响问题,分析了在改变频率、线圈间距、线圈提离距等情况下金属板质点位移的变化。对于铁磁性材料,介绍了压磁—压电比拟法。实验方面,利用电磁超声检测平台对铝板进行了实际测量,测量结果证实了理论分析内容。针对电磁超声采集信号具有信号微弱、噪声大、干扰强、信噪比高的缺点,本文采用软件的方法对电磁超声采集信号进行了滤波去噪。比较了不同处理算法的原理及特点,选择了平均算法及小波去噪算法。结果表明,处理后信号质量明显提高。搭建了电磁超声测厚系统实验平台,并对板材进行了测厚实验。实验平台实现了对金属板的厚度测量。实验结果有效验证了理论及仿真分析正确性。更多还原

【Abstract】 Electromagnetic ultrasonic technique has become one of the important means of detection in industrial production. Because it not only can detect objects without contact or moving objects in various environments, but also can produce a variety of waveforms. Thickness measurement is an important indicator of object detection, especially in the metal plate detection, it is essential to ensure quality and safety of plate.This article studies the electromagnetic ultrasonic metal plate thickness measurement from the experimental and theoretical aspects, and processing the signal collected using software. In theory, this paper studies the basic principle of electromagnetic ultrasonic detection, select transverse wave as the wave type and the transducer structure is determined. The simulation is established using finite element software. For non-ferromag- netic material, the force and displacement of specimen suffered can be obtained from the electromagnetic structure coupling analysis. The analysis shows the main transmission angle. Simulation analyzes the effect on particle displacement by changing frequency, spaced coil and coil lift-off. For the ferromagnetic material, paper introduces an analogy method between magnetic analysis and piezoelectric analysis. In experiment, aluminum plate is measured using the electromagnetic ultrasonic testing platform and the results show that the theoretical analysis is content. In this paper, the weak signal collected with noise and interference is filtered. Comparing to the principle and characteristics of different processing algorithms, this paper chose the average algorithm and wavelet algorithm. The results show that, after processing the signal is improved.The experiment system of thickness measurement is set up and it is used to detect plate. The experiment results can verify the theoretical analysis and simulation effectively, and can measure thickness of metal plate.更多还原