太赫兹光谱技术在复合材料无损检测中的应用研究

发布时间：2018-06-28 19:37

本文选题：太赫兹时域光谱 + 太赫兹成像　；参考：《中国计量学院》2015年硕士论文

【摘要】：太赫兹(THz)辐射是指频率在0.1~10THz的电磁波(1THz=1012Hz),THz能级低(4.1Me V),且具有高信噪比、高分辨率等特征,被用于无损检测领域。复合材料是承压特种设备常用的非金属材料,其有效克服原材料不足的同时表面硬度及强度被降低,出现了多种金属材料中不常见的缺陷,且很难通过传统检测技术解决。THz光谱技术对复合材料分层、夹杂、机械损伤等都能有清晰表达。近年来,THz技术的研究逐渐增多,从更多方面尝试对太赫兹光谱进行分析,对成像技术进行应用是THz光谱技术未来的发展方向。本文针对目前在承压特种设备中常用的复合材料,结合检验检测标准和工程应用需求,基于太赫兹时域光谱系统、BWO连续太赫兹成像系统和调频连续太赫兹成像系统对聚乙烯管道材料、碳纤维缠绕复合材料、玻璃纤维缠绕复合材料进行研究,完成了18种不同材料及缺陷的测试,主要工作和研究点总结如下:(1)通过透射式THz-TDS获得聚乙烯管道样品中不同缺陷点的折射率和吸收系数。在有效波段内,不同测试点在折射率的变化规律,吸收峰的位置都存在差异;通过时域波形,无折射率计算样品中分层缺陷的厚度。实验结果可用于聚乙烯管道样品的缺陷检测并为太赫兹仪器校准提供参考。(2)应用太赫兹调频连续层析成像对Zmax=21mm厚的聚乙烯管道样品进行层析成像并将成像结果进行梯度增强处理以便人眼识别,结果表明不同纵深(2mm-7mm)的成像对不同缺陷的表达重点不同。其中?=1mm的金属夹杂、管道内壁机械损伤及表面损伤宽度,内部深度Zmax=3.2mm的埋藏缺陷都可清晰检测。最大强度成像和样品侧视图互为佐证,进一步确定样品中各类缺陷的形状、方位、连续情况等。(3)BWO连续成像技术被用于玻璃纤维复合材料,成像结果表明,透射式连续成像可以从背面对5mm厚的玻璃纤维表面300?C及以上的热损伤、冲击损伤、划伤缺陷、?=1mm孔洞缺陷等有完整成像,且排除玻璃纤维缠绕材料中环氧树脂的影响对缺陷的形状、位置、大小进行判断。(4)反射式THz-TDS成像被用于2mm厚的碳纤维复合材料,结果表明,碳纤维复合材料中孔洞缺陷的直径大小,划伤缺陷的深度分布,磨损缺陷的面积区域,热损伤的程度等都可直观体现,且成像数据结合图像可对样品的损伤史做出判断。文章最后对太赫兹光谱技术在复合材料无损检测方面的应用及有待进一步开展的工作进行了探讨。
[Abstract]:Terahertz (THz) radiation refers to the low THz energy level (4.1Me V) of the electromagnetic wave (1THzn 1012Hz) with a frequency of 0.1 ~ 10THz, and it has the characteristics of high signal-to-noise ratio (SNR) and high resolution, so it is used in the field of nondestructive testing. Composite material is a kind of nonmetallic material commonly used in special pressure equipment. It can effectively overcome the shortage of raw materials and decrease the surface hardness and strength, which leads to the unusual defects in many kinds of metal materials. It is difficult to solve the problem of lamination, inclusion, mechanical damage and so on. In recent years, the research of THz technology is increasing gradually, and the THz spectrum analysis is attempted from more aspects. The application of imaging technology is the development direction of THz spectroscopy technology in the future. This paper aims at the composite materials which are commonly used in the special pressure equipment at present, combined with the inspection standard and the engineering application demand, Based on terahertz time-domain spectroscopy (THz) system BWO continuous terahertz imaging system and frequency-modulated continuous terahertz imaging system, polyethylene pipe materials, carbon fiber wound composites and glass fiber wound composites were studied. The main work and research points are summarized as follows: (1) the refractive index and absorption coefficient of different defect points in polyethylene pipeline samples are obtained by transmission THz-TDS. In the effective band, the variation of refractive index and the position of absorption peak are different at different test points, and the thickness of delamination defects in samples is calculated by time-domain waveforms without refractive index. The experimental results can be used to detect the defects of polyethylene pipeline samples and provide a reference for the calibration of terahertz instrument. (2) the THz FM continuous tomography is used to image the polyethylene pipeline samples with the thickness of Zmaxx 21mm and the imaging results are incorporated into the imaging results. Gradient enhancement processing for human eye recognition, The results show that different depth (2mm-7mm) imaging has different emphasis on the expression of different defects. Metal inclusions of 1 mm, mechanical damage and surface damage width of the inner wall of the pipeline, and buried defects with a depth of 3. 2 mm in the inner depth of the pipe can be clearly detected. The maximum intensity imaging and the side view of the sample are mutually supporting each other to further determine the shape, orientation and continuity of various defects in the sample. (3) BWO continuous imaging technology has been used in glass fiber composites, and the imaging results show that, Transmissive continuous imaging can provide complete imaging of thermal damage, impact damage, scratch defect and 1 mm hole defect on the glass fiber surface of 5mm thick at or above 300C, etc. The shape, position and size of defects were determined by eliminating the influence of epoxy resin in glass fiber winding materials. (4) reflective THz-TDS imaging was used in 2mm thick carbon fiber composites. The diameter of the hole defect, the depth distribution of the scratch defect, the area of the wear defect and the degree of thermal damage in the carbon fiber composite can be reflected intuitively, and the damage history of the sample can be judged by the imaging data combined with the image. Finally, the application of terahertz spectroscopy in nondestructive testing of composite materials and the work to be further developed are discussed.
【学位授予单位】：中国计量学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB302.5

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