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 Evaluation of Composite Pressure Vessel by Using FBG Sensors

In recent years, advanced composite structures are used extensively in many industries such as aerospace, aircraft, automobile, pipeline and civil engineering. Reliability and safety are crucial requirements posed by them to the advanced composite structures be- cause of their harsh working conditions. Therefore, as a very important measure, structural health monitoring （SHM） in-service is deft- nitely demanded for ensuring their safe working in-situ. In this paper, fiber Bragg grating （FBG） sensors are surface-mounted on the hoop and in the axial directions of a FRP pressure vessel to monitor the strain status during its pressurization. The experimental results show that the FBG sensors could be used to monitor the strain development and determine the ultimate failure strain of the composite pressure vessel.

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.

New Trends in Non-Destructive Evaluation of Surface Hardened Layers and Coatings

This article should not be considered as a full review of current methods for non-destructive testing of surface layers. Rather, it is a subjective in this area. However, the article provides some review of the challenges posed by the current state of surface layers treatment techniques on the area of Non-Destructive materials evaluation: enhancement of the sensitivity to the type of defects, increasing resolution to submicron values, the requirement to diagnose the surface layers with depth resolution of properties, diagnosis of multilayer multicomponent surface layers and coatings, treated with concentrated energy.

Structural Evaluation for Maputo Airport Pavement

Maputo Airport was initially constructed to serve mixed traffic of light and medium aircrafts. With its opening to heavier aircrafts such as B727, DC10, Airbus 340, etc. , structural improvements have become necessary. For this purpose, structural evaluation were described and performed using falling weight deflectometer. Results show that while subgrade response to loads appears more consistent with depth, surface layer of the pavement is significantly influenced by the layer thickness as well as mechanical properties of pavement materials. Load magnitude also affects pavement performance. But loading conditions show an equivalent or even greater influence on pavement performance.

Detection of Accidental Fish Defrosting Using Non-Destructive Ultrasonic Technique

A non invasive ultrasonic method is used to detect whether or not the frozen fish has suffered a partial or total accidental thawing. The time of flight and the peak to peak amplitude of the ultrasonic signals backscattered by fish are recorded during thawing. The comparison of the evolution curves and images corresponding to first and second thawing shows indicators of accidental thawing. The monitoring of thawing process showed that its assessment can be reduced to the measurement of the water content lost by fish. The attempt to replace the original water lost by fish in first thawing is analyzed. The influence of the transducer frequency on fish thawing evaluation is tested.

Statistical Analyses and Geotechnical Evaluation of Nubia Sandstone, Golden Triangle Area, Egypt

Great efforts had been made to use indirect non-destructive tests in the geotechnical evaluation of rocks, especially sandstones, employing different empirical equations. However, most of these equations have been derived from hard and compacted sandstones data;therefore, the focus of this research is on weak and weakly compacted sandstones, aiming firstly to obtain empirical equations for estimating their characteristics, secondly to demonstrate and visualize the correlations between the studied variables, and finally to cluster the studied samples based on their characteristics. To attain these aims, twenty oriented block samples were collected from Nubia sandstone, central Eastern Desert, Golden Triangle area, Egypt. These samples were prepared and tested according to standard test methods, including uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), Schmidt rebound number (SRN), porosity (n), bulk density (ρ), and ultrasonic P-wave velocity (UPV). The loss on ignition (LOI) was also employed as a physicochemical test for classifying the studied samples and indicating pores filling materials. The results revealed that these sandstones are characterized mainly by high n, low ρ, and low UPV values and these give an indication of weakly compacted and weakly cemented sandstone with shallow burial diagenetic conditions. Based on UCS and elastic modulus values, these sandstones are mainly classified as very low strength and highly yielding rocks. The results of regression analysis show satisfactory correlations between physical and mechanical characteristics, indicating the suitability of obtained empirical equations to deduce these properties. Principal component analysis revealed that the LOI, BTS, SRN, and USC have a positive correlation to each other and weakly correlated with ρ and UPV, which positively correlated to each other and negatively correlated to n. The results of agglomerative hierarchical clustering revealed that the studied samples can group into three main clusters depending on their USC, LOI, and n values.

Enhanced air-coupled impact echo technique by phase analysis of signals from multiple sensors

This paper presents an air-coupled impact echo(IE)technique that relies on the phase spectrum of the collected data to find the frequencies corresponding to the reflections from delaminations.The proposed technique takes advantage of the fact that the IE compression wave is not a propagating wave,but it is the 1st order symmetrical(S1)mode Lamb wave at zero group velocity(S1-ZGV).Therefore,it searches the phase spectra of the data collected by multiple sensors to locate the frequency corresponding to the lowest phase difference.As a result,the technique reduces the effect of propagating waves,including the direct acoustic wave and ambient noise.It is named the Constant Phase IE(CPIE).The performance of the CPIE is experimentally compared with the regular amplitude spectrum-based IE technique and two other multisensor IE techniques.The CPIE shows a performance advantage,especially in a noisy environment.

Piezoelectric Actuator/Sensor Wave Propagation Based Nondestructive Active Monitoring Method of Concrete Structures

In order to monitor the basic mechanical properties and interior damage of concrete structures,the piezoelectric actuator/sensor based wave propagation method was investigated experimentally in the laboratory using a specifically designed test setup.The energy attenuation of stress waves was measured by the relative index between the output voltage of sensors and the excitation voltage at the actuator.Based on the experimental results of concrete cube and cylinder specimens,the effect of excitation frequencies,excitation amplitude,wave propagation paths and the curing age on the output signals of sensors are evaluated.The results show that the relative voltage attenuation coefficient RVAC is an effective indicator for measuring the attenuation of stress waves through the interior of concrete.

Segmentation of Thermographic Sequences in Frequency Modulated Thermal Wave Imaging for NDE of GFRP

Image processing techniques have become highly essential to improve the data usefulness of the raw images obtained for infrared non-destructive evaluation(NDE).The identification of defective regions from a thermogram has been a common problem in the field of NDE.Image segmentation is one of the promising approaches to identify defective regions from thermogram.In the present work,segmentation approach based on clustering is employed.In this image patterns are organized into clusters or groups considering the relationship among these.The method involves finding the centroids of the regions and formation of clusters around each centroid.Thresholding is applied to improve accuracy in formation of clusters.Double thresholding method is adapted to retrieve the shape of defect and to improve the possible diagnosis capabilities of system for NDE applications.The proposed method is investigated with frequency modulated thermal wave imaging(FMTWI)over glass fiber reinforced polymers(GFRP).The GFRP sample consists of square shaped Teflon inserts of different dimensions placed at various depths.A comparative study of the proposed novel segmentation scheme and existing segmentation methods is conducted.

Application of Non-destructive Techniques in Evaluation of Wood Properties

With the increase of wood and wood products demands in the world, non-destructive evaluation techniques of wood are more and more important. This article clarifies the importance and present situation of non-destructive evaluation and introduces some instruments about non-destructive evaluation, and some advice and ideas are put forward.

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 。

超声波声速测量技术及其在材料评价中的应用

介绍两种测量声速的方法,阐述这两种方法的原理和区别,并列举了利用声速评价材料性能的实例。

非线性超声在金属基复合材料结构界面粘接强度评价中的应用

针对常规超声波难以对金属基复合材料结构的界面质量进行评价的问题,设计了非线性超声检测系统,利用超声波在界面上传播时微小缺陷与其相互作用产生的非线性响应信号,通过计算回波信号的超声非线性系数,就可以进行金属基复合材料结构界面弱粘接缺陷的检测,进而评价界面的粘接质量。实验结果表明超声非线性系数与界面的粘接强度之间存在一定的关系,因此,非线性超声检测方法有望用于金属基复合材料结构的无损评价。

复合材料粘接界面缺陷的热象无损检测和定量评价

采用红外热象测量技术和图像处理技术对复合材料粘接面质量进行定量检测和评价.从传热学原理出发 ,阐述了复合材料热象无损检测的可行性 .提出用缺陷区域的面积、形心和最大横向尺寸来评定缺陷的大小和位置 。

基于相空间重构和独立分量分析的超声信号噪声消除

提出了一种新的基于相空间重构和独立分量分析的超声信号去噪方法.应用该方法处理了实际的试块超声检测信号,并与小波去噪的效果进行了比较.实验结果表明,该去噪方法的效果与小波去噪方法接近,其特色是通过超声信号和噪声信号的盲源分离实现噪声消除.该去噪方法与小波去噪方法相比具有使用简单容易、去噪效果好和自适应强等优点.

SQUID及在地球物理中的应用

SQUID(SuperconductingQuantumInterferenceDevice)技术(特别是高温SQUID)的发展,为地球物理探测技术的发展提供了巨大潜力.基于SQUID技术开发的地球物理探测系统不仅具有精度高、分辨率高的优点,而且仪器系统轻便.在野外实验和应用取得了巨大的进展.本文将近年SQUID技术应用于地球物理取得的进展进行了简要的总结,并阐述它了在地球物理勘探领域的广阔应用.

航天器在轨无损检测技术研究

航天器尤其是空间站在轨运行期间,碎片撞击以及应力集中区的疲劳损伤会对其结构产生较为严重的破坏作用,对航天器进行在轨诊断和评估是NASA的常规手段。从分析空间环境对常规无损检测方法的影响入手,结合空间应用的特殊要求,建立了基于MR的脉冲涡流无损检测系统,实现了非扫描无损检测技术,解决了传统电涡流无损检测技术的缺陷检测深度和缺陷检测分辨率无法兼顾的矛盾,给出了描述导电材料损伤的物理量及其量值的获取方法,试验结果表明此方法应用于航天器在轨无损检测是可行的。

SPF规格材静、动态弹性模量研究

采用无损横向振动法和三点静态弯曲法,对加拿大进口的云杉-松-冷杉(Spruce-Pine-Fir,SPF)J等级规格材的动、静态弹性模量进行测试和评价。结果表明,SPF规格材有明显的两个峰值,其一阶频率峰值平均为44.78Hz,二阶频率峰值平均122.61 Hz;两种方法测得的SPF弹性模量服从正态分布,近1/3的规格材弹性模量值在10000~11 000 MPa;动、静态弹性模量平均值分别为10 983 MPa和10 523 MPa,SPF规格材动态弹性模量比静态弹性模量高4.38%,动、静态弹性模量值之间具有非常强的相关性(R^2=0.91)。

基于无损检测技术的路桥管理系统框架

提出如何将无损检测 ( NDE)评价结果应用于网级道路桥梁管理系统 ,得到道路桥梁使用性能的定量评价。由于无损检测设备机动性好 ,因此 NDE技术尤其适用于网级道路桥梁管理系统。在专家系统和智能数据库的基础上 。