基于超声红外技术对金属管内壁缺陷的检测

为提高管道的运送效率，及时检测排除管道内壁的缺陷非常重要。提出利用超声红外无损检测方法对管道内部进行检测。超声主动热激励试件，高频红外热像仪记录试件表面温度变化，结合了超声摩擦生热和红外热成像的优点。对壁厚约为3.3mm检测难度较大的金属管内壁缺陷进行了检测。通过对采集数据和热图的处理分析，准确快速地确定缺陷所在的位置。实物对比分析表明：超声热激励红外无损检测技术可以对金属管道内壁缺陷进行准确检测定位。     

复合材料脱粘缺陷的红外热像无损检测

以固体火箭发动机中的玻璃纤维复合材料壳体/绝热层试件的脱粘缺陷为研究对象,利用脉冲闪光灯热激励方式对试件进行加热,用红外热像仪实时监测试件的表面温度场,由表面温度差异来判定试件内部缺陷,然后通过对热像图进行图像增强处理和分割以定量识别缺陷。将实验结果与超声C扫描检测结果进行的对比分析表明:红外热像无损检测方法能够快速直观地发现深度5 mm以内、直径10 mm以上的脱粘缺陷,而超声C扫描检测更适合于对特定缺陷进行准确定量检测。     

铝合金板疲劳微裂纹超声红外成像检测的数值及实验研究*

超声红外成像检测技术是一种发展迅速的新型无损检测技术,可用于检测材料表面或近表面的缺陷,由于对缺陷具有选择性加热的特点,近年备受检测行业的关注。在铝合金板中制作疲劳微裂纹,在板中激励声波,裂纹表面因振动摩擦生热,用红外摄像仪记录板表面温度分布。拍摄的红外图像序列经傅立叶变换后得到的幅值和相位图能清晰显示裂纹的特征,测量到的裂纹长度误差达到4.3%。用有限元模拟超声在板中裂纹处的生热过程,研究板中超声在裂纹处的励热机制。超声的激励时间、裂纹表面间的摩擦系数和裂纹开口宽度直接影响裂纹处的励热效果,温度最高通常位于裂纹尖端附近。实验和模拟结果均表明超声红外成像检测技术能对板中疲劳微裂纹实现快速检测,提供有效、可信的检测结果。     

蜂窝缺陷的红外无损检测及有限元模拟

蜂窝结构在使用过程中,常见的缺陷有脱粘和积水。红外无损检测技术通过对试件主动加热,利用热像仪采集试件表面的红外辐射变化,从而检测出物体的缺陷信息。实验结果表明,蜂窝积水位置的温度要低于参考区域的温度。基于这一现象,利用Ansys有限元软件模拟了蜂窝结构的脉冲红外热成像检测过程,并与实际脉冲红外热成像用于表面下识别检测实验结果进行对比,验证了模拟结果的正确性。对蜂窝结构的积水、脱粘和积油缺陷模拟并进行对比识别,为实际实验提供理论基础。     

振动激励条件下复合材料损伤生热的研究

为实现对复合材料表面及浅表面损伤的快速检测,采用振动热成像技术,对复合材料在疲劳、冲击等不同作用下产生的损伤进行了检测研究。分析了瞬时性和周期性两种内生热源形式下平板构件的表面温度场分布。基于有限元法计算了表面裂纹、浅表面分层及内部脱粘等不同类型损伤在振动激励条件下的生热情况。在设计制作复合材料疲劳裂纹试件和冲击损伤试件的基础上,利用超声波发生器和红外热像仪开展了试验研究。结果表明:振动热成像技术能够快速准确地检测到复合材料表面及浅表面的紧贴型损伤;通过红外序列图中热斑形状可判断损伤的类型。     

红外热波技术在装甲装备故障诊断和缺陷检测中的应用

 针对装甲装备典型故障诊断操作复杂及缺陷检测效率低下等问题,将国外装备维修中广泛应用的红外热波技术引入到装甲装备维修过程中。简要介绍了红外热波技术的基本原理及特点,系统分析了信噪比和热激励2个因素对检测效果的影响,并成功实现了装备发动机动力不足的故障诊断和装甲板裂纹的缺陷检测。试验结果表明：该技术能够在不解体的情况下实现发动机动力不足故障的准确定位,同时能够在3.5 s之内实现装甲车底板裂纹等缺陷的快速检测。     

基于激光超声的微裂纹检测技术的研究

在固体中利用激光产生超声波 ,可作为超声测量和材料无损检测的一种新方法。介绍了激光超声表面波的产生机理、微裂纹的检测方法及其应用。采用Nd∶YAG脉冲激光器、扩束与聚焦透镜组、PZT探头、数据分析仪等器件设计并构建了一套基于接触式检测方法的激光超声微裂纹检测实验系统。通过对大量实验数据进行处理 ,得出了相应的各种关系曲线 ,说明了线光源产生的超声表面波非常适用于材料表面微裂纹的检测     

基于小波变换的红外热波无损检测融合算法

在红外热波无损检测中获取的热像序列存在着背景噪声大、缺陷边缘模糊、对比度低等特点。为了提高由红外热像序列重构的数字图像的缺陷显示能力,以小波变换为热像处理工具,采用基于像素级和特征级的图像融合算法对热像序列进行了处理,并采用基于统计学的图像评估标准对处理效果作了定量评价。通过对铝合金试件的检测实验说明该方法可用于材料内部缺陷的红外热波无损检测。研究结果表明,此种图像融合算法可对不同深度缺陷所对应的两幅最佳热像进行有效地融合,在一幅融合图像中直观地反映出全部缺陷,并能有效地减少加热不均和背景噪声对缺陷识别的不利影响。     

红外热波无损检测技术用于聚丙烯管道缺陷的检测

由于聚丙烯管道所处的工作环境恶劣,长期使用后极易形成内壁腐蚀、结垢和裂纹等缺陷,导致管道的性能降低,引发事故,因此对聚丙烯管理进行严格的天损检测是十分必要的。将红外热波无损检测技术用于预埋有三种缺陷(腐蚀、结垢和裂纹)的聚丙烯管道的无损检测;对红外热像仪采集的数据进行处理,得到典型时刻的热图和温度对数-时间曲线。通过分析典型时刻热图的灰度随时间变化的情况和曲线的斜率变化,对三种缺陷类型进行定性分析,并对缺陷进行定位。利用图像处理软件测量出了腐蚀面积。实验结果表明,红外热波无损检测技术可以快速、直观和有效的检测聚丙烯管道的三种常见缺陷。     

太赫兹激励的红外热波检测技术

本文的目的在于探索一种新的适用于红外热波检测技术的热激励方式——太赫兹(THz)热激励. 文中介绍了THz波周期性热激励的热传导理论模型; 尝试利用返波振荡器(返波管backward wave oscillator, BWO)太赫兹源对一块碳纤维基底吸波涂层板进行周期性THz热激励, 红外热像仪连续观测和记录试件表面温场变化, Canny边缘算法处理热图像显示缺陷; 检测结果与闪光灯脉冲激励的结果进行比较, 讨论了太赫兹波激励红外热波检测技术可能的优势. 实现了THz技术与红外热波无损检测技术的结合.     

Infrared Image Series Automatic Registration and a History & Tendency Analysis

Infrared camera has been widely used in electrical power systems for predictive and preventive thermal fault diagnosis. Without historical IR images being considered, most thermograph analysis used at present are concerned with static image. The dynamic history and tendency analysis which compares the newly taken image with historical images is particularly attractive. Conclusions can be drawn from temperature variations rather than just from anomalous thermal pattern. However the spatial distortions prevent such dynamic analysis from being practicable. So the need to register infrared images arises. This paper proposes an automatic registration algorithm based on closed temperature contour matching for infrared image series of a target equipment taken at different times. Centroid Distance Function is used in image registration for the first time. The algorithm can remove spatial distortions, bring temperature variations into prominence and endow infrared camera with dynamic analysis ability. Experiment shows that the algorithm is simple, effective and extensible.     

基于幅度调制的非线性超声相控阵成像方法*

超声相控阵是超声检测领域常用的材料缺陷定位和成像技术,可便捷快速地对裂纹、孔洞等缺陷进行成像。但是,传统超声相控阵方法对较小缺陷如闭合裂纹不太敏感。非线性超声信号因对材料性能退化以及微小缺陷敏感而广受关注。本文针对疲劳闭合裂纹检测,提出一种基于幅度调制的非线性超声相控阵成像方法,通过测量物理聚焦和虚拟聚焦两种聚焦模式下超声扩散场中的声能差,并将其作为非线性参量,实现疲劳裂纹闭合部分的定位成像和定量表征。将该法应用于7075铝合金试样疲劳裂纹的实验测量,并研究了扩散场信号延迟时间对非线性超声相控阵成像结果的影响。结果表明：相较于传统超声相控阵全聚焦法,基于幅度调制的非线性超声相控阵成像方法能够更准确地定位和成像疲劳裂纹闭合部分;延迟时间的选择对疲劳裂纹长度的表征精度影响较大,本文研究了该延迟时间的选择方法并实现了检测结果的优化。     

Application of the nitroanisole as an infrared detector used in middle infrared interferometer

We propose the application of nitroanisole as a detector for middle infrared (mid-IR) interferometry or holography. The present experiment utilizes the liquid form of nitroanisole, which has a thermal lens effect, i.e. a temperature dependent refractive index. Since the nitroanisole absorbs IR radiation as heat, it is possible to estimate the IR intensity distribution on the nitroanisole from the diffraction pattern made by visible laser light that is transmitted through the nitroanisole. In this study, the time resolution and the diffraction efficiency of the nitroanisole was measured under various conditions. The experimental results show that the nitroanisole has a time resolution as high as that of a standard video camera, as well as a high diffraction efficiency and the spatial resolution equivalent to that of a conventional IR camera. Furthermore, we confirmed that the phase shift in mid-IR region can be estimated by analyzing the change in the visible diffraction pattern.     

Triboluminescence in sodium chloride

The emission of light due to rubbing or impact of two surfaces (Triboluminescence) has been traditionally studied under visible and ultraviolet spectrum. The current study provides an experimental insight into infrared emission occurring during low velocity impact on common salt crystals. The high speed IR imaging done using a whole field IR camera is first of its kind of measurement that provides experimental verification of IR emission occurring in these events. It was observed that the nature of impact surface and the crystalline structure of the material have a marked role in the IR emission. Of the existing theories that explain the origin of light emission in TL, the model provided by Chapman, that TL is a thermal radiation from high temperature regions, which propagate along with the crack, matches closely with the current experimental observations.     

A dynamical model of subharmonic generation in ultrasonic infrared thermography

Subharmonics are often observed in ultrasonic infrared thermography (UIR) system as samples are excited by ultrasonic transducers, and it is testified that, as the subharmonics appear, the detectability of cracks or defects in the sample is greatly enhanced in the UIR system. A dynamical model to explore the generation mechanism of the subharmonics and simulate the sample motion excited by an ultrasonic transducer in the UIR system is presented in this paper. In the model, the sample is continuously impacted by the transducer as the transducer is pushed to the sample by a constant force, in which the sample is simplified as a damped oscillator and the transducer is simplified as an active oscillator with constant frequency and amplitude. The impact process is also taken into account, in which the acting force is assumed to vary linearly during the impact process. A stable waveform of subharmonics in the sample can be obtained in appropriate conditions.