Pulsed Eddy Current Non-destructive Testing and Evaluation:A Review

Pulsed eddy current （PEC） non-destructive test- ing and evaluation （NDT＆E） has been around for some time and it is still attracting extensive attention from researchers around the globe, which can be witnessed through the reports reviewed in this paper. Thanks to its richness of spectral components, various applications of this technique have been proposed and reported in the lit- erature covering both structural integrity inspection and material characterization in various industrial sectors. To support its development and for better understanding of the phenomena around the transient induced eddy currents, attempts for its modelling both analytically and numeri- cally have been made by researchers around the world. This review is an attempt to capture the state-of-the-art development and applications of PEC, especially in the last 15 years and it is not intended to be exhaustive. Future challenges and opportunities for PEC NDT＆E are also presented.

Non-destructive experimental testing and modeling of electrical impedance behavior of untreated and treated ultra-soft clayey soils

The characterization of ultra-soft clayey soil exhibits extreme challenges due to low shear strength of such material.Hence,inspecting the non-destructive electrical impedance behavior of untreated and treated ultra-soft clayey soils gains more attention.Both shear strength and electrical impedance were measured experimentally for both untreated and treated ultra-soft clayey soils.The shear strength of untreated ultra-soft clayey soil reached 0.17 kPa for 10% bentonite content,while the shear strengths increased to 0.27 kPa and 6.7 kPa for 10% bentonite content treated with 2% lime and 10% polymer,respectively.The electrical impedance of the ultra-soft clayey soil has shown a significant decrease from 1.6 kΩ to 0.607 kΩ when the bentonite content increased from 2% to 10% at a frequency of 300 kHz.The10%lime and 10% polymer treatments have decreased the electrical impedances of ultra-soft clayey soil with 10%bentonite from 0.607 kΩ to 0.12 kΩ and 0.176 kΩ,respectively,at a frequency of 300 kHz.A new mathematical model has been accordingly proposed to model the non-destructive electrical impedancefrequency relationship for both untreated and treated ultra-soft clayey soils.The new model has shown a good agreement with experimental data with coefficient of determination（R;）up to 0.99 and root mean square error（RMSE） of 0.007 kΩ.

Optical generation,detection and non-destructive testing applications of terahertz waves

Optoelectronic terahertz generation and detection play a key role in the applications of non-destructive testing,which involves different areas such as physics,biological,material science,imaging,explosions detection,astronomy applications,semiconductor technology and superconductiong electronics. In this article,we present a reviewof the principle and performance of typical terahertz sources,detectors and non-destructive testing applications. On this basis,the newdevelopment and trends of terahertz radiation detectors are also discussed.

Application Research of the Non-Destructive Testing Using Optical Fiber Sensor

In this paper, an optical fiber sensor is designed by using optical Faraday effect. It is composed of fiber collimator, polarizer, magneto-optical crystal and mirror. Based on the magnetic flux leakage (MFL) theory, The optical fiber sensor was placed between two permanent magnets with the N-pole. Therefore, the optical fiber sensing system was built to detect the defective ferromagnetic objects. Theoretical and experimental studies shown that the system can identify a little defects, such as irons’ blind hole (diameter φ =?3mm , depth t = 4mm?), irons’ grooves (length l= 30mm , width?ω = 10mm ), hole (φ?=?3mm ) and crackle etc. The system has the characteristics of small size, high sensitivity, fast signal response and high resolution. In terms of the defective oil and gas pipelines detection, The optical fiber sensing system is used in non-destructive testing, which will be valuable and meaningful.

The Research Progress of Nondestructive Testing Technology in the Detection of Egg Quality

[Objective]The aim was to improve the quality of the egg in favour of producers and business operators according to the market demand to take scientific feeding and management.[Methods]This paper discussed the research progress of using machine vision,optical properties,and acoustic resonance technology in the egg quality nondestructive testing. [Results]Egg quality indicators directly affect their edible quality and quality levels. [Conclusion]Egg quality test has practical value and practical significance.

Nondestructive Testing Electrical Methods for Sensing Damages in Cement Mortar Beams

This paper discusses the experimental results of concurrently measured Electrical and Acoustic Emissions in order to evaluate the mechanical health status of cement mortar beams subjected to three-point bending mechanical tests. In particular, the Electrical Resistance and the Electrical Current emissions are recorded concurrent with Acoustic Emissions and the experimental results are discussed under the concept of crack initiation and propagation processes. For the first time, the electrodes that are used for conducting the measurements are placed in the bulk of the specimen, near the tensile zone, during its preparation. The damage evolution is examined by monitoring the fractional change of the Electrical Resistance and the variation of the Electrical Current in combination with the Acoustic Emission recordings.

Non-Destructive Testing of Rods Using a Potential Component of a Magnetic Field

An essentially new method for non-destructive testing of elastic electrically conductive rods using non-vortex electromagnetic induction is proved theoretically. An experimental technique for defining a location of a cross crack is offered.

NON-DESTRUCTIVE PAVEMENT LAYER THICKNESS MEASUREMENT USING EMPIRICAL MODE DECOMPOSITION WITH GPR

Ground Penetrating Radar(GPR) is an effective Non-Destructive Testing(NDT) technique for highway pavement surveys, which is able to acquire continuous pavement data compared with traditional core drilling method. In this study, we proposed an accurate and efficient method to estimate the thickness of each pavement layer using an air-coupled GPR system. For this work, the main difficulties are estimating each pavement layer's time delay and dielectric constant. We first give the basic signal model for pavement evaluation, and then present an Intrinsic Mode Functions(IMFs) product detector to determine each pavement layer's time delay. This method is based on Empirical Mode Decomposition(EMD), which is an adaptive signal decomposition procedure and proved to be suitable for suppressing noises in GPR signal. The dielectric constant was determined by metal reflection measurement. The laboratory and highway experiments illustrate that the proposed thickness estimation method yields reasonable result, thus meets the requirements of practical highway pavement survey with massive GPR data.

Non-Destructive Imaging of Water Permeation through Cementitious Materials Using MRI

In this study, water permeation through cementitious materials was observed using magnetic resonance imaging (MRI). The influence of cement type on the magnetic resonance signal was studied subsequent to determining the parameters required for imaging. Consequently, adequate imaging of water permeating through hardened cement paste (HCP) made with white Portland cement was achieved, while water permeation through ordinary Portland cement-based HCP yielded poor signal. HCPs maintained at various levels of relative humidity (RH) were observed, and the signal was detected only from those maintained at an RH of higher than 85%. The water permeation depths in HCP were observed by using MRI, and the measured depths were compared to those measured via a spraying water detector on the split surface of the specimens. As a result, good agreement was confirmed between the two methods. Additionally, MRI was applied to concrete specimens;although it was found that water was not detected when a lightweight aggregate was used, water permeation through concrete with limestone aggregate was detectable via MRI. MRI will help in understanding how water permeation causes and accelerates concrete deteriorations such as rebar corrosion and freezing and thawing.

Non-destructive Evaluation of Absolute Stress in Steel Members Using Shear-Wave Spectroscopy

Non-destructive measurement of absolute stress in steel members can provide useful information to optimize the design of steel structures and allow the safety of existing structures to be evaluated.This paper investigates the non-destructive capability of ultrasonic shear-wave spectroscopy in absolute stress evaluation of steel members.The effect of steel-member stress on the shear-wave amplitude spectrum is investigated,and a method of absolute stress measurement is proposed.Specifically,the process for evaluating absolute stress using shear-wave spectroscopy is summarized.Two steel members are employed to investigate the relationship between the stress and the frequency in shear-wave echo amplitude spectrum.The H-beam loaded by the universal testing machine is evaluated by the proposed method and the traditional strain gauge method for verification.The results show that the proposed method is effective and accurate for determining absolute stress in steel members.

Non-destructive study of fruits using grating-based X-ray imaging

Grating-based X-ray imaging can make use of conventional tube sources to provide absorption, refraction and scattering contrast images from a single set of projection images efficiently. In this paper, a fresh cherry tomato and a dried umeboshi are imaged by using X-ray Talbot–Lau interferometer. The seed distribution in the scattering image of the cherry tomato, and the wrinkles of epicarp in the refraction image of the umeboshi, are shown distinctly. The refraction and scattering images provide more information on subtle features than the absorption image. Also, the contrast-to-noise ratio values show distinguishing capacity of the three kinds of imaging techniques. The results confirm that grating-based X-ray imaging is of great potential in non-destructive fruit testing.

Determination of Bonding Failures in Transparent Materials with Non-Destructive Methods—Evaluation of Climatically Stressed Glued and Laminated Glass Compounds

As part of an international research project—funded by the European Union—capillary glasses for facades are being developed exploiting storage energy by means of fluids flowing through the capillaries. To meet highest visual demands, acrylate adhesives and EVA films are tested as possible bonding materials for the glass setup. Especially non-destructive methods (visual analysis, analysis of birefringent properties and computed tomographic data) are applied to evaluate failure patterns as well as the long-term behavior considering climatic influences. The experimental investigations are presented after different loading periods, providing information of failure developments. In addition, detailed information and scientific findings on the application of computed tomographic analyses are presented.

Feasibility Study for Applying Spectral Imaging for Wheat Grain Authenticity Testing in Pasta

Authentication of pasta is currently determined using molecular biology-based techniques focusing on DNA as the target analyte. Whilst proven to be effective, these approaches can be criticised as being destructive, time consuming, and requiring specialist instrument training. Advances in the field of multispectral imaging (MSI) and hyperspectral imaging (HSI) have facilitated the development of compact imaging platforms with the capability to rapidly differentiate a range of materials (inclusive of grains and seeds) based on surface colour, texture and chemical composition. This preliminary investigation evaluated the applicability of spectral imaging for identification and quantitation of durum wheat grain samples in relation to pasta authenticity. MSI and HSI were capable of rapidly distinguishing between durum wheat and adulterant common wheat cultivars and assigning percentage adulteration levels characterised by low biases and good repeatability estimates. The results demonstrated the potential for spectral imaging based seed/grain adulteration testing to augment existing standard molecular approaches for food authenticity testing.

Simulation as a Support for Ultrasonic Testing

Ultrasonic testing is a very important non-destructive method for testing components for safety of nuclear power plants and other security and delicate parts in other industries. Nowadays, thanks to the development of computer technology, it is possible to simulate processes which occur during ultrasonic testing. That is why numerical simulations are becoming an integral part of non-destructive testing. Simulations are used to determine parameters of ultrasonic examination, especially parameters of probes and scan plan and also in the analysis of results. They are used in such cases, when it is necessary to verify applicability of probes and methods. This verification could be provided on the weld and test block which are not manufactured. It could be also provided on defects, which are not manufactured in test block, but their presence is possible in given weld joint. Simulations are very useful for verifying the propagation of ultrasonic signal in given area (e.g. weld area). If movement of probe is limited, possibility of whole volume scan should be verified.

高温声学检测技术的发展、应用与挑战

以我国航空航天、钢铁冶金、特种设备等领域的高温声学无损检测技术研究与应用为主线,分析了高温声学检测技术在促进先进高温材料制备与研发、钢铁冶金行业绿色低碳生产和产业升级、高温压力管道安全运行与维护等方面的巨大需求。介绍了国内外在高温声学检测的技术方法和仪器研制等方面取得的进展,分析了压电超声、电磁超声、激光超声、激光电磁超声等技术在高温无损检测应用方面存在的优缺点和应用场景,总结了高温声学检测技术面临的机遇与挑战。

光谱技术在果品无损检测中的应用研究进展

介绍了常用的果品无损检测方法,包括电子鼻法、X射线计算机断层成像法、机械方法、磁共振(核磁共振)成像光谱学法、拉曼光谱学法、近红外光谱技术等;重点综述了高光谱成像技术在无损检测水果结构特性、生化成分和安全性等方面的研究进展,以期为水果品质的无损检测研究提供参考。

老旧直升机维修中无损检测技术的应用

随着使用年限的增长,老旧直升机结构性故障和偶发性故障逐渐增多,给维护修理带来了诸多困难,维护人员常常不能及时发现和消除故障隐患。针对当前老旧直升机的特点和维修现状,介绍了无损检测技术在航空维修领域中的应用,结合直升机结构特点和使用情况探讨确定老旧直升机无损检测的重点部位和关键部件,围绕不同无损检测技术特点对直升机关键部件检测的具体应用方法进行阐述,并结合老旧直升机维护实践对无损检测技术的使用时机做出探讨和研究,最后对无损检测技术在老旧直升机维修中的应用前景进行了展望。

一种古籍修复用纸伸缩性检测方法的探讨

补纸选配是古籍修复中的重要环节,但其伸缩性尚未引起足够重视。古籍修复补纸均为传统手工抄制,浸水后强度较低。按现行国家标准浸湿法检测补纸伸缩性时易产生撕裂、变形等问题,适用性较差。本研究探讨了一种古籍修复补纸的伸缩性检测方法——喷润法。利用水分检测仪对补纸相对含水量进行测定,从测量时间和可操作性的角度验证了该方法的可行性。通过十余种常用补纸的伸缩性检测结果发现,喷润法与浸湿法所得结果具有较好的一致性。随后探讨了古籍书叶伸缩性检测的适用性,并结合具体案例,建议在修复前分析古籍书叶与补纸的伸缩性匹配度。喷润法有效避免了补纸浸湿后的拉伸变形或破裂,既适用于古籍修复补纸,也适用于古籍书叶的无损检测,可为古籍修复策略的制定提供科学依据和参考。

钢筋混凝土结构移动式精准检测技术开发

无损检测技术是一种在不损害材料及结构服役性能的前提下,对其性质进行评估和测量的检测技术。然而,随着无损检测技术的发展和实践,结构内部的复杂损伤检测缺乏多层次精准性成为该领域的难点和核心问题。该文旨在结合国内外的研究成果,对无损检测技术的发展、分类和挑战进行梳理和分析,并在此基础上,介绍作者研究团队建立的一套由宏观到细观,再到内部的全面精准检测系统研究成果。针对表面宏观识别与细观定量识别,作者团队开发了表观病害视觉检测技术,包括构建的空间基准点自动追踪融合和亚像素级病害分割的全景图像快速拼接及表观病害厘米级定位方法,以及提出的全景图像中0.05 mm~0.2 mm多尺寸微细裂缝同步识别及真伪判别的人工智能算法。针对结构内部损伤识别,作者团队首创了智能变频敲击声波扫描及各类损伤精准识别新原理,发明建立了自适应激励分布移动敲击声波的损伤检测评估理论方法、声波及声纹图像特征人工智能算法及智能装备关键技术。经过实验验证,裂缝检测中宽度为0.05 mm时最大深度可达40 mm,剥离检测中最大深度可达400 mm,最小识别范围为50 mm。