Depth of penetration effects in eddy current testing

The simple depth of penetration equation used for most eddy current calculations does not take into account the effect of the size of the coil or the effect of flaw morphology. The work described in this paper describes use of the CIVA eddy current model to investigate this effect and some experimental investigations. Knowledge of this effect is important in examination of thin sections with eddy currents. Two examples of this are the small sections required to be inspected in laser metal deposition, and welds in thin sections joining dissimilar metals such as copper and aluminium for electrical connections

Modelling of pulsed eddy current testing of wall thinning of carbon steel pipes through insulation and cladding

Conventional eddy current techniques have been used to a great extent for detection of surface breaking defects in conductive materials. Pulsed Eddy Current (PEC) techniques excite the probe’s driving coil with a repetitive broadband pulse, usually a square wave, instead of sinusoidal wave. The resulting transient current through the coil induces transient eddy currents in the test piece, these pulses consist of a broad frequency spectrum, and the reflected signal contains important depth information. Surface pancake type pulsed eddy current probes have been used for wall thinning and corrosion detection but these methods can be slow. In order to increase the scanned area, an encircling coil has been proposed, with a view to inspect a complete circumference with a single pulse. The work presented in this paper employs COMSOL Multiphysics finite element (FE) modelling software, to further investigate the behaviour of an encircling probe design as a part of the development work. This work involves modelling of an encircling coil around a steel pipe with insulation and cladding of different materials. Pulsed eddy current testing of wall‐thinning through cladding and insulation was studied for various wall thinning situations. The simulation results show the capability of this system in pipe wall thinning detection

A pulsed eddy current system for flaw detection using an encircling coil on a steel pipe

Conventional eddy current techniques have been used to a great extent for detection of surface breaking defects in conductive materials. However, detection of sub-surface defects is limited due to skin effect phenomena and material properties. Pulsed Eddy Current (PEC) techniques excite the probe’s driving coil with a repetitive broadband pulse, usually a square wave. The resulting transient current through the coil induces transient eddy currents in the test piece, these pulses consist of a broad frequency spectrum, and the reflected signal contains important depth information. The work in this paper employs COMSOL Multiphysics, the finite element (FE) modelling software, to investigate the behaviour of a new encircling probe design. This work involves modelling of an encircling coil around a steel pipe with high lift-off to simulate insulation. The 3D modelling of the coil wrapped around a steel pipe was employed and surface breaking discontinuities were modelled. The simulation of these scenarios provided essential information about the behaviour of this probe design

Reliability Improvement of Magnetic Corrosion Monitor for Long-Term Applications

Electromagnetic techniques are widely employed for corrosion detection, and their performance for inspection of corrosion is well established. However, limited work is carried out on the development and reliability of smart corrosion monitoring devices for tracking internal or buried thickness loss due to corrosion remotely. A novel smart magnetic corrosion transducer is developed for long-term monitoring of thickness loss due to corrosion at critical locations. The reliability of the transducer is enhanced by using a dissimilar active redundancy approach. The improved corrosion monitor has been tested in the ambient environment for seven months to evaluate the stability against environmental factors and degradation. The monitor is found to show great sensitivity to detect defects due to corrosion. Detection of anomalous patterns in the time series data received from the monitors is accomplished by using Pearson’s correlation coefficient. The critical component of the monitor is identified at the end of the test. Research findings reveal that, compared to the existing corrosion monitoring techniques in the industry, the detection and isolation of faulty sensor features introduced in this study can contribute to reliable monitoring of thickness loss due to corrosion in ferromagnetic structures over an extended period of tim

Unsettling integration

As part of the three-year project “EPIC”, funded by the Asylum, Migration and Integration fund, this research explores the diversity of responses to migration accross eleven European urban spaces and the different strategies put in place by migrants to navigate and learn the city. To achieve its objective, the project has been designed to establish an international environment for building knowledge and exchanging good practices across multiple partners and sectors. The first chapter examines current migration and integration literature in order to dissect and move beyond the notion of integration. Incorporating policy discourse and academic analyses of integration frameworks and practice, the chapter provides a discursive context for and background to the need for concept revision and to how processes and practices of adaption are perceived of and understood. The second chapter discusses the findings of the surveys and interviews conducted across the eleven cities based on an alternative framework of care, repair and maintenance, drawing out the dominant dimensions and themes within subjective definitions and experiences of ‘integration’. The analysis underlines the importance of recognising the diversity in trajectories of integration, and that policy design should focus on removing obstacles to integration rather than imposing linear integration trajectories. The paper attempts to adopt a reflexive gaze throughout the research to acknowledge the position of power, privilege and in most cases whiteness of the researchers involved. It also recognise the limitations of this type of research and the fact that it is not meant to provide solutions. It wishes, however, to foster further reflections and address the challenges faced by local NGOs and governments

Parameter analysis of pulsed eddy current sensor using principal component analysis

Pulsed eddy current (PEC) technique provides a means to inspect structures without surface contact. It is particularly useful when the structure’s surface is rough or inaccessible, such as insulated pipes in pipeline. Probe parameters of a PEC system, especially the sensing and excitation coil diameters, can significantly affect the PEC system’s performance. Thus, detailed analysis of these parameters is paramount in developing a PEC system. Currently, this is accomplished by establishing the trend of features with respect to the analyzed variables, e.g. sample thicknesses. However, prior to extracting these features, a number of configuration parameters have to be determined. For this reason, analyzing PEC performance over a range of coil diameter values is rather time-consuming as both the sensing and excitation coil diameters significantly affect the received signals. Principal component analysis (PCA) is proposed as an alternative to the feature extraction. The work here analyzes the trends contributed by the PCA scores for different values of sensing and excitation coil parameters. Results from both numerical simulations and experiments suggest that the sensitivity of the PEC probe is highly correlated with the excitation coil diameter, while the excitation-sensing coil distance is not significant in determining the sensitivity of the PEC probe. These findings are consistent with those reported in the literature, suggesting the potential of adopting PCA for an automated PEC performance analysis process

Convolution of Barker and Golay Codes for Low Voltage Ultrasonic Testing

© 2019 The authors. Ultrasonic Testing (UT) is one of the most important technologies in Non-Detective Testing (NDT) methods. Recently, Barker code and Golay code pairs as coded excitation signals have been applied in ultrasound imaging system with improved quality. However, the signal-to-noise ratio (SNR) of existing UT system based on Barker code or Golay code can be influenced under high high attenuation materials or noisy conditions. In this paper, we apply the convolution of Barker and Golay codes as coded excitation signals for low voltage UT devices that combines the advantages of Barker code and Golay code together. There is no need to change the hardware of UT system in this method. The proposed method has been analyzed theoretically and then in extensive simulations. The experimental results demonstrated that the main lobe level of the code produced by convolution of Barker code and Golay code pairs is much higher than the simple pulse and the main lobe of the combined code is higher than the traditional Barker code, sidelobe is the same as the baker code that constitutes this combined code. So the peak sidelobe level (PSL) of the combined code is lower than the traditional Barker code. Equipped with this, UT devices can be applied in low voltage situations

RAAI Project: Life-prediction and prognostics for railway axles under corrosion-fatigue damage

Corrbosion damage induced by atmospheric agents has been shown to be able to trigger fatigue failures of railway axles. In this tphaepenIreDwMetEofiCorl,sDrtleyelpideasirstocmnuesnast nocefowMnseaoculhitadonamitceadtlerEdensgucilnatensenirneinrmga,boIldnesetltilotiunetogffiStchuipeengrtirloyrwaTtnéhcanolyifcsode,aoUmpnatigvcearlusimnddaeedaresucdoreerLmroisesbniotasn,-oAffavt.tihRgeouvceiosacrnroodPdiaetsids,da1ex,tle1ec0ts4iu9or-nf0a.0c1eLainsbdoa, paper we firstly discuss consolidated results in modelling the growth of damage under corrosion-fatigue and its detection. Portugal craTchkisgrioswththebsiamckuglartoiuondtofolrtduensecdribthinrogutghhefduelvl-eslcoaplmemenetaosfuraemneewntpsrofganxolseticotrorolsiwonit-hfiantitghueeRdAamAaIgEeU.-fundedproject.Indetails, This is the background for describing the development of a new prognostic tool within the RAAI EU-funded project. In details, cCeFEMA, Department of Mechanical Engineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisboa, the new tool relies on a new automated scanner able to efficiently analyse optical measurements of the corroded axle surface and a the new tool relies on a new automated scanner able to efficientlPyoartnuaglaylse optical measurements of the corroded axle surface and an axle corrosion-fatigue mode

Analysis and determination of UT POD curves for railway axles

The increasing demand for the reliability assessment of railways components, especially for high speed trains applications, leads to a new definition of safety factor that can be determined by a “defect tolerant” approach and by the evaluation of “safe life” inspection intervals as a function of materials characteristics, propagation models and NDT inspections. The present paper deals with the determination of inspection intervals of railways axles, considering the special application of a typical alloyed steel grade for high speed trains, hollow axles and a specially developed UT device for in-service inspection. Initially, the POD curve of such device has been derived by means of dedicated experimental UT measurements. This curve has then been used together with the crack propagation behaviour of 30NiCrMoV12 steel in order to define inspection intervals of high speed railway axles