红外无损检测在面向等离子体部件检测的应用

建立了主动式内热源激励的红外无损检测平台,并进行了不同缺陷大小的EAST W/Cu 面向等离子体部件(PFC)的无损检测实验(NDT),得到试件表面的红外热图。通过最大温差值融合法消除由试件表面发射率不均匀引起的温度误差,通过快速离散傅里叶变换法提高了图像的信噪比,实现了对W/Cu 面向等离子体部件缺陷的分辨。通过数值模拟的手段对可能影响该检测技术的关键因素进行了定量分析。     

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。     

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。     

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。     

强流激光离子源中的等离子体参数诊断

强流激光离子源是最有希望为重离子聚变直线感应加速器提供离子的离子源之一。离子源内等离子体决定了离子源性能和引出品质,为了了解强流激光离子源内等离子体参数,采用发射光谱和ICCD成像的方法对该离子源中的等离子体进行了诊断。该离子源由一台四倍频的266 nm Nd:YAG激光器和Cu靶组成,激光束经过透镜聚焦后照射在Cu靶上产生等离子体,激光打靶能量密度约为108 W/cm2,持续时间15 ns。ICCD相机拍摄了激光照射后等离子体的膨胀过程,初始时刻等离子体垂直表面喷射,膨胀速度约为1 cm/s。光谱仪测量了离子发射光谱,谱线主要由Cu原子的Cu Ⅰ谱线和Cu+离子的Cu Ⅱ谱线组成。采用Boltzmann图法得到膨胀等离子体电子激发温度约为1 eV,采用Stark展宽法得到电子密度约为1016 cm-3。     

基于分布式超声无损检测方法的零件内部缺陷检测

超声检测广泛应用于工业检测,比如超声相控阵检测法和超声A扫应用于零件内部缺陷检测。然而,这些方法可以检测出缺陷位置却很难精确地检测缺陷尺寸,缺陷定量成了急需解决并且很有意义的问题。本文提出了一种分布式超声无损检测方法,将超声探头均匀布置在检测表面,每一个超声探头可以同时发射和接收超声信号,通过对接收到的信号进行处理来重构缺陷轮廓。基于分布式超声无损检测方法,重构零件的人造缺陷并建立相应的声学仿真模型。通过多项式拟合法和聚类法分别处理实验和仿真所获得的数据并重构缺陷轮廓。实验结果和仿真结果显示重构的椭圆形缺陷和正方形缺陷具有一定的精度。结果表明分布式超声无损检测方法有潜在的应用价值和理论意义。     

含缺陷疲劳试件的锁相红外热成像无损检测

锁相红外热像技术由于其实时、快速、无损以及非接触等优点,被逐渐应用于疲劳研究中。基于锁相红外热像理论,用法国Cedip公司开发的锁相红外热像系统对含缺陷的疲劳试件进行了无损检测,并快速测得了其疲劳极限。结果表明,相位图比幅值图能提供更多的缺陷内部信息,恰当选择检测频率是无损检测的关键,缺陷面积越大检测精度越高。随缺陷深度的增加,疲劳试件的疲劳极限降低。     

二维不规则形状发热型缺陷的红外识别算法

对带有自身发热型缺陷的试件建立二维传热模型,利用有限元法进行求解,研究试件表面的温度分布规律,并根据共轭梯度法提出根据试件外表面红外测温,定量识别发热型内部缺陷边界轮廓的方法.数值实验证明了算法的有效性.对所研究缺陷类型,导热系数较小的试件识别精度较高;温度测量误差、测温点数目及缺陷轮廓初值假设对识别结果的影响可以忽略;检测表面最大温差越大,识别精度越高.     

面向等离子体部件沉积特性的数值模拟研究

采用粒子模拟研究方法，利用PEGASUS 程序对等离子体环境下面向等离子体部件的沉积特性进行了模拟研究。结果显示部件表面连接缝隙尺寸、表面粗糙度、粒子入射的角度以及流量对沉积影响显著。在能量较小、溅射可忽略时，能量对沉积的影响很小。粗糙度越小，沉积量越小；同一种粗糙度，不同轮廓也会使沉积发生较大变化，轮廓一致的更有利于减小沉积。该模拟对研究等离子体与材料相互作用，分析瓦片缝隙尺寸、瓦片加工工艺和等离子体参数对面向等离子体部件沉积行为的影响具有重要意义。     

(Cu,Al)掺杂ZnO薄膜表面处缺陷的拉曼光谱研究

采用电感耦合等离子体增强物理气相沉积法制备了(Cu,Al)掺杂ZnO薄膜,超导量子干涉磁强计测试结果表明,薄膜具有室温的铁磁性。采用激光共聚焦拉曼(Raman)光谱研究了(Cu,Al)掺杂ZnO薄膜的表面特性,以两种处理方式对薄膜进行了Raman光谱测试:共聚焦模式从薄膜表面开始至不同深度处进行测试;对薄膜样品进行预处理加工,采用面扫描模式在薄膜平面对(Cu,Al)掺杂ZnO薄膜的斜面进行测试。分析了Raman光谱A₁(LO)峰的中心位置和强度变化,结果表明,界面处晶格应力和缺陷明显增强。这些晶格畸变和点缺陷的存在会对体系的铁磁性有促进作用。     

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.     

超声红外热像技术及其在无损评价中的应用

本介绍在光热红外检测的基础上发展的超声红外热像技术。该技术利用超声脉冲作为激发源，当超声脉冲在试样上传播的过程中遇到裂纹等缺陷时，缺陷引起超声附加衰减而局部升温。利用红外照相机获取试样表面的温度分布，可显示裂纹等缺陷。超声红外热像技术发挥了超声和红外技术的优点，可实时地检测裂纹等缺陷，在无损评价和检测中有广泛应用。     

Research on thermal wave processing of lock-in thermography based on analyzing image sequences for NDT

Lock-in thermography, an active IR thermography technique for NDT, is based on propagation and reflection of thermal waves which are launched from the surface into the inspected component by absorption of modulated radiation. In this paper, thermal wave image sequences were sampled by a Cedip JADE MWIR 550 FPA infrared camera. Thermal wave signal processing algorithms are investigated to obtain information on subsurface defects. The Fourier transform, four-point correlation, and digital lock-in correlation algorithms are applied to extract the amplitude and phase of thermal wave’s harmonic component. A novel method called the time constant method (TCM) is proposed to analyze subsurface defects by using lock-in thermography. The experimental results confirm the thermal wave signal processing algorithms’ efficiency on subsurface defect detection.     

Comparative analysis on thermal non-destructive testing imagery applying Candid Covariance-Free Incremental Principal Component Thermography (CCIPCT)

Thermal and infrared imagery creates considerable developments in Non-Destructive Testing (NDT) area. Here, a thermography method for NDT specimens inspection is addressed by applying a technique for computation of eigen-decomposition which refers as Candid Covariance-Free Incremental Principal Component Thermography (CCIPCT). The proposed approach uses a shorter computational alternative to estimate covariance matrix and Singular Value Decomposition (SVD) to obtain the result of Principal Component Thermography (PCT) and ultimately segments the defects in the specimens applying color based K-medoids clustering approach. The problem of computational expenses for high-dimensional thermal image acquisition is also investigated. Three types of specimens (CFRP, Plexiglas and Aluminium) have been used for comparative benchmarking. The results conclusively indicate the promising performance and demonstrate a confirmation for the outlined properties.     

Inspection on SiC coated carbon–carbon composite with subsurface defects using pulsed thermography

An investigation on SiC coated carbon–carbon (C/C) composite plates has been undertaken by pulsed thermography. The heat transfer model has been built and the finite element method (FEM) is applied to solve the thermal model. The simulation results show that defects with DA/DP smaller than one can hardly be detected by an infrared camera with the sensitivity of 0.02 °C. Certificated experiments were performed on the built pulsed thermography system. The thermal wave signals have been processed by subtracting background image method (SBIM), pulsed phase thermography (PPT), and temperature–time logarithm fitting method (TtLFM). The limit DA/DP of defects in SiC coated C/C composite plates with the thickness of 6 mm that can be detected by pulsed thermography with the presented signal analysis algorithms has been obtained.     

Lock-in thermography for nondestructive evaluation of materials

Photothermal radiometry allows for remote measurement of local harmonic heat transport where the phase angle (between remote optical energy deposition and resulting temperature modulation) is sensitive to subsurface features or defects. Phase sensitive modulation thermography (or ‘lock-in thermography’) combines the advantages of photothermal radiometry with the fast technique of infrared imaging thereby revealing hidden defects in a short time. In this paper the principle and various applications are described and analyzed. While this lock-in thermography is based on remote optical heating of the whole area of interest, one can heat defects selectively with modulated ultrasound which is converted into heat by the mechanical loss angle effect which is enhanced in defect regions. This ‘ultrasonic lock-in thermography’ provides images showing defects in a way that is similar to dark field imaging in optical microscopy.     

Square pulse thermography in frequency domain as adaptation of pulsed phase thermography for qualitative and quantitative applications in cultural heritage and civil engineering

A methodical approach for qualitative and quantitative non-destructive testing of near-surface structures in civil engineering (CE) with active thermography is presented. It adopts the non-destructive testing (NDT) method of pulsed phase thermography (PPT) for the special requirements of CE and cultural heritage. The concept might be understood as a square pulse thermography (SPT) in frequency domain or an amplitude-expanded PPT with square pulse heating.After a discussion of the material spanning concept and qualitative results in cultural heritage a new approach for quantitative non-destructive testing (NDT) of near-surface structures in CE with active thermography is introduced and tested by investigations on concrete specimen with artificial defects. It is based on the thermal diffusivity of the material and the characteristic frequency of the first extrema of phase and amplitude contrast and aims at complementing the established approaches for defect depth calculation for measurements with long heating and observation times. It should be easily extendable to other fields of application.     

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。