Quantification by Signal to Noise Ratio of Active Infrared Thermography Data Processing Techniques

In this paper, the use of a signal to noise ratio (SNR) is proposed for the quantification of the goodness of some selected processing techniques of thermographic images, such as differentiated absolute contrast, skewness and kurtosis based algorithms, pulsed phase transform, principal component analysis and thermographic signal reconstruction. A new hybrid technique is also applied (PhAC—Phase absolute contrast), it combines three different processing techniques: phase absolute contrast, pulsed phase thermography and thermographic signal reconstruction. The quality of the results is established on the basis of the values of the parameter SNR, assessed for the present defects in the analyzed specimen, which enabled to quantify and compare their identification and the quality of the results of the employed technique.

Numerical Simulation of Non-destructive Testing of Stainless Steel Composites Plate by Infrared Thermography

The non-destructive testing(NDT)of debonding in stainless steel composites plate(SSCP)is performed by infrared thermography,finite element analysis(FEA)software ANSYS is taken as the simulative tool,and 2D simulative model has been set up to investigate effect of the thickness of coating and/or substrate on the detectibility of debonging in SSCPs.Two parameters,namely the maximum defect temperature difference and defect appearing index,are defined to evaluate the detectivity of defects,and their computational methods and formulas are given respectively.The preliminary changing tendency of the maximum defect temperature difference and defect appearing index with the thickness of coating and/or substrate is found by numerical simulation.

Pulsed electromagnetic non-destructive evaluation and applications

This paper introduces recent research work in the field of pulsed electromagnetic non-destructive testing/evaluation.These are pulsed eddy current,pulsed magnetic flux leakage and eddy current pulsed thermography.This paper introduces pulsed electromagnetic techniques and their different case studies on defect detection as well as stress characterisation.Experimental tests have been validated and future research plans are discussed.This paper demonstrates pulsed electromagnetic non-destructive testing and evaluation for not only depth information,but also for multiple parameter measurement and multiple integration,which are important for future development.

基于红外热成像技术的隧道隐性渗漏检测研究

因隧道安装防火板,导致渗漏水隐蔽在防火板背后而不易被检测。红外热成像技术是一种非接触无损检测技术,因其对表面热辐射敏感而常用来测量表面温度场。基于红外热成像技术,研究了隧道隐性渗漏车载非接触式快速检测的可行性。结合某长江隧道,将红外热成像设备安置在车顶,对隧道内表面实施移动扫描拍照,并通过红外热力图准确识别既有渗漏点。为了进一步验证检测效果,人为在防火板表面涂湿模拟渗漏,该渗漏过程可以被准确识别。通过试验研究,表明红外热成像技术用于隧道隐性渗漏车载非接触式快速检测是可行性的。

Successes and challenges in non-destructive testing of aircraft composite structures

Composite materials are increasingly used in the aerospace industry.To fully realise the weight saving potential along with superior mechanical properties that composites offer in safety critical applications,reliable Non-Destructive Testing(NDT)methods are required to prevent catastrophic failures.This paper will review the state of the art in the field and point to highlight the success and challenges that different NDT methods are faced to evaluate the integrity of critical aerospace composites.The focus will be on advanced certificated NDT methods for damage detection and characterization in composite laminates for use in the aircraft primary and secondary structures.

Feature Extraction Approach for Defect Inspection in Eddy Current Pulsed Thermography

The eddy current pulsed thermography(ECPT)technique is a research focus in the non-destructive testing(NDT)area for defect inspection.Defect feature extraction for defect information analysis in ECPT is limited by image contrast,heat diffusion,background interference,etc.In this paper,a defect feature extraction approach in ECPT has been proposed to improve the quality of defect features,which is based on image partition,local sparse component evaluation,and feature fusion.This method can extract complete defect features by enhancing the defect area and removing background interference,such as noises and heating coil.Two typical steel specimens are utilized to testify the validity of the proposed approach.Compared with other three common feature extraction algorithms in ECPT,the proposed method can reserve more complete defect features and suppress more background interference.

NDI of Rail Squats and Estimating Defect Size and Location Using Lock-In Thermography

Rail squats are a form of near surface rolling contact fatigue damage found in rail heads. Currently, the most popular method to detect the rail squats is utilizing ultrasonic techniques to determine their presence and measure their depths. This technique needs to be direct contact between the probe and the rail head, with a coupling fluid in at the interface. Other weaknesses of these ultrasonic techniques include false detections as well as missed detections. Infrared thermography is a relatively new non-destructive inspection technique used for a wide range of applications but is not used for rail squat detection. Lock-in thermography is a non-destructive inspection technique that can be used for the detection of near surface defects. It utilizes an infrared camera to detect the thermal waves and then produces a thermal image, which displays the local thermal wave variation in phase or amplitude. In inhomogeneous materials, the amplitude and phase of the thermal wave carries information related to both the local thermal properties and the nature of the structure being inspected. This comparison is then used to determine the phase angle difference (Δf) between the input and the thermal response of the object. The aim of this paper is to determine whether lock-in thermography can be used to firstly locate squats in rails, and secondly measure their depths. It has demonstrated the feasibility for using such a technique in generating thermal responses that could be adequately utilized for the purpose of defect characterization.

沥青路面内部缺陷无损检测技术研究综述

为了快速、准确地检测出沥青路面内部缺陷和病害,以便及时采取养护或其他处理措施,保障道路行车安全。同时,为促进沥青路面内部隐性病害和缺陷无损检测技术的发展,对现有沥青路面内部缺陷的无损检测技术进行了综述。分别综述了探地雷达的基本原理、在沥青路面检测中的应用以及探地雷达图谱的智能识别,超声波检测技术的检测原理、超声波的衰减规律研究和其在路面内部缺陷检测中的应用与研究,红外热成像技术、核子密度仪、无核密度仪和瑞利波法的检测原理和在沥青路面内部缺陷检测中的应用与研究,最后汇总了各检测技术的检测原理、检测缺陷类型和优缺点等,并探讨了各检测技术存在的问题和未来的发展方向,为沥青路面内部缺陷无损检测技术的进一步应用与研究提供了参考和依据。

升力体缝隙模型红外测热试验及分析

针对升力体缝隙模型在中国空气动力研究与发展中心的Φ0.3 m高超声速低密度风洞中开展了红外测热试验,试验马赫数12、总温668 K、总压4.731 MPa、攻角0°和35°,获取了模型的红外热图结果,并开展了相应的数值仿真分析。在此基础上,研究了选取不同帧次的红外热图进行数据处理对热流密度结果的影响,分析了缝隙干扰引起的热流密度增量。结果表明:投放后模型抖动对数据处理存在明显影响,建议在数据处理中采用模型投放稳定后(约1.2 s)的红外热图结果;“T”字型缝干扰区的热流密度增量需要引起重视,攻角35°情况下的峰值热流密度能达到无缝隙时热流密度的8倍以上;红外测热试验数据与CFD数据吻合较好,两者仅在很小的峰值干扰区域存在差异。下一步需要在CFD建模倒角处理、红外方案优化等方面开展工作。

金属增材制造内部缺陷激光热波检测方法研究

金属增材制造是近年来发展迅速的一种高效材料加工技术,为了保障构筑件的质量和可靠性,应避免其内部形成对结构力学性能有显著影响的缺陷。本文研究了激光红外热成像检测技术在金属增材制造亚表面缺陷检测上的应用。首先,基于有限元仿真结果,研究了激光红外热成像检测对不同深度和尺寸的金属亚表面缺陷检测的可靠性,进一步地,考虑了粗糙表面对检测的影响,并对比验证了常用红外热成像序列处理算法的噪声干扰抑制性能;最后,对加工有人工内部缺陷的选择性激光熔融试件进行了实验验证。仿真和实验结果表明,激光红外热成像检测可以可靠地检出宽深比大于1的金属增材制造内部亚表面缺陷,通过常用的热成像序列预处理方法,可以有效地抑制粗糙表面干扰造成的空间噪声,此外,由于激光红外热成像检测技术具备高效、非接触以及可视化的优势,有望成为金属增材制造在线监测的可靠技术。

激光热成像无损检测研究进展(特邀)

红外热成像是无损检测技术的典型代表。按有无外部激励源,红外热成像可大致分为被动式热成像与主动式热成像两类。其中,以激光作为激励源的主动式热成像,因其输出功率稳定、能量分布均匀、可控性强等诸多优势于近些年得到了广泛的应用。文中首先介绍了激光热成像无损检测系统的构成与激光热成像的分类,并进一步探讨了激光热成像无损检测系统的优化与相关图像处理方法,并从应用角度对现有主要研究工作进行了综述、分析、总结与对比。目前,基于激光热成像的无损检测方法在实际应用过程中存在精度不够,效率偏低,检测对象受限等问题。为提升检测效果,研究人员从激励方式、检测条件、图像处理等方面出发提出了多类优化策略。随着新一代信息技术的发展与检测技术精度要求的提高,激光热成像无损检测从裂纹等表面缺陷的检测,拓展至包括分层、脱粘等内部缺陷检测,从缺陷定性分析拓展至缺陷定量计算,从二维缺陷识别拓展至三维缺陷重构。通过详细分析现有研究,认为提升激光源性能、开发小型便携式激光器、结合智能算法的三维缺陷定量检测等是激光热成像无损检测未来的发展方向。

红外成像技术在化工设备安全监测中的应用与探讨

我国化工行业在国民经济中的重要地位日益凸显,安全事故成为制约其发展的严重隐患。化工生产领域的泄漏事故会造成严重后果,因此建立健全的泄漏监测预警系统具有紧迫性。传统方法在化工设备的监测和故障诊断应用过程中存在一定的缺陷,而红外热成像技术凭借其非接触、实时的优势越来越受到关注。本文详细介绍了该技术的原理,并深入讨论了其广泛应用场景,研究发现该技术在化工设备的无损检测及远程监测方面具有显著优势。

槽罐车缺陷及泄漏的在役热成像和声发射检测方法综述

随着石油化工产业的快速发展,槽罐车作为危险化学品的主要运输工具,其安全性对铁路和公路运输安全至关重要。本研究旨在探讨槽罐车缺陷和泄漏的在役热成像和声发射检测方法。通过分析罐体表面温度梯度变化和泄漏时产生的高频震动信号,提出了一种基于长波红外热成像与声发射技术的多模态数据融合在役检测策略。该策略通过数据融合处理,可实现对槽罐车罐体异常状态的自主检测,能够为槽罐车的安全运输提供技术支持。

Applications of Non-destructive Tests for Diagnosis of Heritage Buildings:Case Studies from Singapore and Malaysia

Non-destructive tests have been increasingly used in historic buildings not only for pre-restoration investigation but also as useful tools to evaluate the effectiveness of eventual interventions.These tests can complement and supplement destructive tests like laboratory analysis of extracted samples as long as a sound sampling plan has been put in place to commensurate with the pattern and extent of dilapidation and materials distribution.Common methods employed in projects in Singapore and Malaysia include the infrared thermography,ground penetrating radar,microwave moisture tomography and ultrasonic pulse echo tomography.The paper discusses about a selection of case studies,demonstrating the application of various techniques for the identification of hidden details,defects and deterioration,and moisture detection.

超声红外热像技术及其在无损检测中的应用

在超声技术和红外热像技术的基础上,建立了混合型的超声红外热像系统,并利用超声红外热像技术检测材料(试样)的缺陷(裂纹)和残余应力等不均匀结构。当超声波脉冲发射到样品中时,声能在样品中衰减而转化为热能,样品内部及表面的温度会升高。一般情况下,在缺陷或不均匀的区域声衰减更显著,引起的温度变化更大,而温度的差别可以用红外热像仪来观察和记录。因此可以很灵敏和迅速地对缺陷或结构和应力不均匀的区域进行检测。

脉冲加热红外热成像无损检测的有限元模拟及分析

为了进行定量化的红外无损检测，必须全面考察脉冲加热冷却的全过程，更准确地得到红外无损检测过程中各参数对缺陷检测的影响．通过三维有限元分析方法模拟了脉冲加热红外无损检测过程，分析了影响脉冲加热红外无损检测灵敏度的几个参数，找出了脉冲加热红外无损检测对比度变化的规律，为进一步进行定量化红外无损评价打下了基础．

脉冲热像法在航空复合材料构件无损检测中的应用

对红外热像检测技术的原理、特点和国内外应用状况作了简单的介绍,对闪光灯激励脉冲热像法中影响检测的主要参数进行了分析,并针对多种常见的复合材料构件进行了检测研究。研究结果表明:对于薄蒙皮的泡沫夹层结构件和蜂窝夹层结构件,闪光灯激励脉冲热像法能够给出清晰的检测结果和丰富的构件内部信息,可以检测出脱粘缺陷、损伤和蜂窝积水,能够用于雷达罩的在役检测。闪光灯激励脉冲热像法适于检测厚度较薄的层合板构件。

电线电缆破损的定量热像检测与诊断方法研究

通过控制容积法对带有破损的高压输电线及电缆建立了物理和数学模型。模型考虑了电线和电缆芯的轴向导热,更精确地描述了破损程度和温度响应的关系;得到了无破损以及不同程度破损时电线以及电缆的表面温度分布规律;提出了通过红外热像仪测量表面温度分布在线检测与诊断输电线和电缆破损程度的方法,并针对常用电线电缆进行了具体分析和诊断。理论和实验研究均证明了红外在线检测电线电缆破损的可行性及定量诊断方法的有效性。

民航飞机主动红外热波成像检测技术应用进展

根据主动加热方式不同,论述了脉冲加热、锁相调制加热、超声加热、微波加热等主动红外热成像无损检测技术理论基础和技术特点;综述了主动红外热成像无损检测技术用于飞机机体结构缺陷、蒙皮腐蚀、复合材料缺陷、发动机管路堵塞与叶片裂纹等无损检测方面的研究成果;结合主动红外热成像实验技术特点,指出了其在飞机检测方面存在的问题和发展方向。

超声红外锁相热像技术检测金属板材表面裂纹

超声红外锁相热像检测法是超声波激励与红外锁相热像检测技术相结合的一种红外无损检测方法。采用超声红外锁相热像检测法实现对金属板材构件接触界面类缺陷的检测,分析超声波激励构件缺陷的选择性加热过程。通过有限元仿真模型对热流在金属板材内部的热传导过程进行研究并分析超声激励参数对检测结果的影响;利用所建立的超声红外锁相检测系统对预制金属板材构件接触界面类缺陷中的裂纹缺陷进行检测实验,验证有限元模型的有效性。研究结果表明,加载中心位置远离缺陷时,裂纹缺陷幅值降低,相位不变;超声激励振幅(即初始静压)增加,缺陷处的幅值升高,相位基本保持不变;超声调制频率增加,缺陷处幅值降低,相位升高。通过对比仿真结果与实验结果发现,所建立的仿真模型能够较好地预测检测过程中的热流传递,并且能够用于超声红外锁相热像技术检测金属板材接触界面类缺陷检测结果的预测,为超声红外锁相热像技术激励参数的选择提供了指导。