Ebook: Electromagnetic Nondestructive Evaluation (XVII)

This volume contains selected papers from the 18th International Workshop on Electromagnetic Non-destructive Evaluation (ENDE), which was held in Bratislava, Slovak Republic on June 25–28, 2013. ENDE workshop is an important event for the researchers with interest in non-destructive evaluation. The first workshop was organized in 1995 in London, UK and then followed 16 workshops held in various countries in different parts of the world. The last one – the 18th ENDE 2013 workshop was for the first time organized in Slovakia.

The aim of the workshop was to provide an international forum for discussion on the state of art and perspectives in the field of electromagnetic non-destructive methods from the view of science, technology and their applications in engineering. From the demand for new effective methods of maintenance of industrial equipments and their live-time testing up to the industrial processing control or medical engineering support evokes a hard scientific and technological effort of many research, development and university institutions all over the world. So the main aim of the workshop was to bring together scientists from universities and research institutions and specialists from institutions of industrial application of electromagnetic non-destructive evaluation in order to offer the opportunity to exchange their best knowledge and experiences.

The workshop was organized by the Faculty of Electrical Engineering, University of Zilina, Slovak Republic and the Alumni Club of the Faculty of Electrical Engineering, University of Zilina in cooperation with the Japan Society of Maintenology and the Japan Society of Applied Electromagnetics and Mechanics.

Sixty four participants from 17 countries (Japan, Slovakia, Poland, France, USA, Germany, Romania, Brazil, Korea, Portugal, Greece, India, Hungary, China, Italy, Czech Republic and UK – listed according to the number of participants) were officially registered. There were presented 61 contributions: 1 key-note lecture, 6 invited lectures, 29 oral and 25 poster presentations.

Keynote Lecture:

P. Kucik, Applications of innovative eddy current probes for non-destructive testing in practice.

Invited Lectures:

1. P. Lopato, T. Chady, Advances in terahertz NDE,

2. J.M.A. Rebello, Advances in electromagnetic NDE for material characterization,

3. R. Grimberg, Advances in high frequency electromagnetic ENDE,

4. H. Kikuchi, Advances in magnetic NDE,

5. B.P.C. Rao, T. Jayakumar, Recent advances in eddy current NDE and future directions,

6. N. Yusa, Numerical modelling of real cracks for electromagnetic nondestructive inverse analysis.

Short versions of all the contributions have been reviewed and published in the Book of Abstracts and forty revised and peer reviewed full papers have been accepted and included into the present volume Electromagnetic Nondestructive Evaluation (XVII) published by IOS Press in the series Studies in Applied Electromagnetics and Mechanics 39.

We would like to express our thanks to all workshop participants for their presentations and manuscripts submissions and to the reviewers for their effort to produce a high quality of volume works. We thank also to the session chairs for their helpful work during the workshop.

Thanks are due to the members of the ENDE Standing Committee, by name to the chair of STC Professor Fumio Kojima, for their helpful attitude during the workshop organization.

Last but not least we would like to thank to all members of the workshop organizing committee for their hard work and excellent assistance during the preparation of the ENDE 2013.

We hope that the readership of this book will find the included papers interesting and inspiring.

Klara Capova, Ladislav Janousek, Lalita Udpa and B. Purna Chandra Rao

Editors

The monitoring of large structures typically require a variety of sensors based on different physical principles combined with set an appropriate set of diagnosis and prognosis methods. The monitoring is in tightly coupled aspect of nondestructive examination. This paper presents a new type of passive wireless sensors for monitoring of strain-stress. The sensor employs a special type of metamaterial named split ring resonator. In order to increase the sensitivity and the tuning of the desired interrogation frequency, the sensor use a self-assembled layer-by-layer single wall carbon nanotubes/graphene as well as an RFID tag. The key essential element for the wireless sensors, can be realized using a split ring resonator.

Magnetic method is one of a prospective candidate for nondestructive evaluation before crack initiation, because magnetic properties are very sensitive to microstructures of the materials, and therefore are sensitive to the mechanical properties. This paper introduces the relations between the magnetic properties and the mechanical properties, the microstructures of materials firstly, and explains several magnetic parameters for nondestructive evaluations: hysteresis, permeability, Barkhausen noise, etc. Then, the several results of parameter changes on cold rolled low carbon steel are introduced. As other cases, results when scanning a probe over deformed samples are described (these include the reviews of our past works). Finally, since microstructures have anisotropy as well as the magnetic properties for the deformed sample, the results in such cases are introduced. The potential of nondestructive evaluation using magnetism for mechanical properties and degradation of steels will be introduced.

The paper deals with biomaterial electromagnetic non-destructive testing with an emphasis on real defects identification. Various modifications of eddy current testing (ECT) detection sensors will be compared and discussed from the desired detected signal characteristics points of view. Advanced magnetic sensors such as giant magneto-resistance (GMR) sensors and fluxgate sensors and probe coils are presented in the paper. These advanced sensors are characterized by their sensitivity, frequency range and sensors dimensions. The measurements for detection of stress corrosion cracks (SCC) in implants materials using magnetic sensors will be presented and their responses will be compared.

In this paper the inspection of stress subjected composite materials was carried out using three nondestructive methods: radiography, infrared thermography and terahertz. In order to combine the information about the defects arising in examined materials the low-level data fusion algorithms were applied. The results are presented and discussed.

Pulsed eddy current (PEC) technique is attractive for detection of surface defects and wall-thinning in covered electrically conductive materials. This paper discusses development of PEC technique and two different types of self-nulling probes (differential Hall sensors and Double-D differential coils) for detection of surface notches in a thick stainless steel plate. PEC testing of covered objects is attempted. In this regard, the influence of lift-off on the PEC signal due to insulation shims and thin aluminum layer is studied using the peak amplitude and the performance of the two probes is compared. The results showed that the PEC instrument, probes and scanner developed can be used for detection as well as imaging of defects in stainless steel plates covered with insulation.

The research on composite magnetic sensors must deal with magnetic, thermal and mechanical properties of ferrite filler in the selected dielectric matrix. This research was focused on properties of the mixture of Sr ferrite filler in the polymer (rubber) matrix. Basic questions of these properties of ferrite-rubber blends were solved. They have been studied for using them for measuring the elastic deformation of the body's surface. The example of the model of passive magnetic sensor is also presented and compared with an active magnetic one.

Electromagnetic non-destructive testing (NDT) systems have been used in steel strip production lines for a long time. Indirect electromagnetic determination of approximate yield and ultimate strength values can be considered state of the art. However, the excellent mechanical properties of advanced high strength steel (AHSS) are particularly sensitive to process variations. Characteristics and homogeneity of texture, grain size and secondary phase content are crucial during forming and welding of steel strips. Ultrasonic methods can be applied in order to indirectly characterize these properties. Deviations which have not been detected in the rolling mill are known to cause flaws or expensive and time-consuming downtimes of the press. The crash performance of the automotive structure is affected by these properties as well. Current in-line NDT systems determine only a subset of the required parameters and do not assess their homogeneity across the strip width. This raises the demand for NDT solutions which assess a larger set of material characteristics in multiple locations at high strip speeds. This paper describes a probe design which allows ultrasonic time-of-flight measurements as well as Micromagnetic Multi-Parameter Microstructure and Stress Analysis (3MA) using a common, minimal set of components. The implementation of a simplified yet advantageous incremental permeability and eddy current impedance analysis based on this probe type is discussed, and first results are presented.

Rotating Field Eddy Current (RoFEC) Probe for inspection of tubes and cylinders offers high operation speed and sensitivity to defects of all orientations. This paper investigates the sensitivity of the RoFEC probe built with encircling excitation coils. The feasibility of the proposed approach is studied using finite element models and results are presented for non-magnetic and ferromagnetic tube inspection.

In this paperthe numerical modeling of composite materials in view of Nondestructive Testing is considered. The composite material is assumed to be modeled at the macroscopic scale by a possibly complex dielectric permittivity tensor. The material is probed by means of an electromagnetic field having wavelength much larger than the relevant geometrical dimensions. As well known, the numerical modeling is critical especially in this “low-frequency” regime where a strong ill-conditioning of the relevant stiffness matrix typically occur (the so-called low-frequency breakdown problem). The proposednumerical model is robust w.r.t. this underlying ill-conditioning.

The article deals with connection of arterial system model based on electromechanical analogy and real photoplethysmographic measurements. The model of arterial system is used for prediction of elastic moduli of arteries. Analysis of photoplethysmographic curve by using its second derivative was used for estimation of elastic moduli of measured subjects.

The European project SIMPOSIUM (standing for Simulation Platform for Non Destructive Evaluation of Structures and Materials) aims at developing simulation tools adapted to the needs of industrial partners, regarding non-destructive testing and material characterization techniques. This communication presents the results obtained with two different simulation methods in the case of an eddy current inspection of pieces with complex shapes.

In this paper, the dependence of plastic deformation on nondestructive evaluation signals of nonlinear ECT (NECT) method is investigated through experiments. The test-pieces of SUS304 austenitic stainless steel are fabricated and tensile residual strains of different scales are applied to them by using a material testing machine. NECT signals of different exciting frequencies are measured, and the experimental results reveal that there are clear relationships between the plastic strains and the feature parameters of the NECT signals especially the loop area and the coercive force, which are sensitive to plastic strain at all tested excitation frequency. It can be concluded that NECT is feasible to quantitatively evaluate the plastic deformation in structures of the 304 austenitic stainless steel.

The present paper focus on the multifrequency and a novel window multifrequency ECT algorithm applied specifically to the magnetic SG tubes of a Fast Breeder Reactor (FBR). The algorithms parameters are determined and validated using 3D numerical Finite Element Simulations of the RF-ECT signal based on codes previously developed in-house by authors. The algorithm robustness is checked and validated using first numerical simulations and then experimental measurements conducted with a small mock-up test tank with SG tubes and full circumferential grooves or partial defects located on the external SG tube surface near tube support plate.

Typical Pulsed Eddy Current Testing (PECT) signals, resulting from the inspection of canonical structures affected by flaw(s), consist in magnetic field variations above the conductor or in coil impedance change, both as functions of time. Calculation of specimen response to Time-Dependent (TD) excitation signals can be obtained through an inverse Fourier transform (FT) of Time-Harmonic (TH) simulated signals, weighted by the FT of the excitation signal. In this paper, an efficient strategy for simulation of PECT signals is introduced. Two adaptive algorithms, guaranteeing the accuracy of the calculations without any intervention of the user, are used to interpolate the spectral response from a database of simulated signals in harmonic regime. Then PECT simulations can be carried out quickly for many TD excitation signals. The performance of this approach is compared with standard manual choices of frequencies proposed in the literature.

Two numerical techniques, the finite integration technique (FIT) and the surface integral equation (SIE) method are combined with the semi-analytical calculation of the field in planar conducting pieces in order to calculate the interaction of such specimens with ferrite-cored eddy-current probes. Coupling different techniques allows us to chose the best suited for each part of the configuration and to better exploit the existing symmetries.

The X-Probe® and the +Point® eddy current probes are used by many utilities for the inspection of steam generator tubes. IRSN and CEA have developed simplified models for those probes using two codes: CIVA and FLUX. A good agreement is obtained between data and simulation results considering the uncertainties in the probe parameters and the simplified approach. The complex shape of the ferrite core of the +Point probe is a challenging issue for modeling and is not considered in this preliminary work. CEA is developing a new model within CIVA for eddy current probes with a complex ferrite core.

This paper presents experimental measurements and 3D finite element simulations of the In-Service Inspection (ISI) of ferromagnetic steam generator (SG) tubes covered by a sodium layer. The ISI of SG tubes is using remote field eddy current technique (RF-ECT) and detect defects located near or between tube support plates and SG tube. Large scale electromagnetic eddy current computations are performed using parallel simulations with up to 1024 CPUs on Fujitsu BX900 based on in-house developed/parallelized code 3D-RFECT. Validations of FEM simulations with experimental measurements for helical tubes are conducted for a large model of SG tubes support plate and three SG tubes attached to it.

Divertor, one of the most challenging in-vessel components facing to plasma in a Tokamak device, is composed of tungsten or carbon fiber composites (CFC) mono-block of multilayer tube structure to withstand huge heat and particle flux. The multilayer tube bonded with hot isostatic pressing (HIP) welding technology is one of the key components for removing heat in divertor. The debonding defect in HIP welding surface may occurs due to fabrication and heat fatigue reason and may significantly reduce the heat transfer ability of the tubes. The debonding defect needs to be inspected in a nondestructive way to prevent local over heat and structural failure. In this paper, two kinds of EMAT probes are proposed to detect debonding defect in the multilayer tubes and their validity is valuated numerically by using a simulation code based on the formulation of reduce vector potential (Ar) method and the time domain difference scheme for wave propagation simulation.

Electric wires are laid down nationwide while they are subject to severe environmental conditions, including natural phenomena, such as heavy wind and rain, and soot and smoke in the industrial area. If water penetrates into an installed wire which is exposed to such an environmental condition, it may accelerate corrosion of wire. If a great amount of stress is applied to a wire, it may result in cracking in the concerned wire section, leading to wire break. In order to ensure reliable power transmission and prevent wire break which causes an accident, it is essential to correctly understand the status of wire corrosion. We propose a new ECT method to inspect high voltage electric wires of common use in Japan and evaluate its practical applicability.

As operating time of nuclear power plants increase, corrosion products in secondary water are built up as scaled deposits on the outside of steam generator tubes, increasing potentials for the corrosion of tube materials with fluid flow restrictions and heat transfer efficiency problems. Several experiences in nuclear power plants have shown that the heat fouling by corrosion product formations in secondary side cause water level oscillation, degrading the thermal performance of steam generators. It is necessary to assess the extent and location of scaled deposits on steam generator tubes for the effective management and maintenance of steam generator. In prior work, tube mock-ups with various thicknesses of scaled deposits have been set up to provide information about the overall deposit condition of steam generator tubes, deriving methodologies to automatically measure deposit thicknesses [1]. In this paper, another tube mock-up with different deposit simulation method is used to improve the similarity in deposit densities of field data and eddy current signal behaviors from the new tube mock-up are correlated to the deposit thicknesses. Using the correlation as a reference, the automatic scaled deposit measurement system has been developed with 3 dimensional mappings of deposit distributions and the overall estimation of the scaled deposit amount. The developed system has been applied to actual plant data of 2 outages and showed similarities with heat transfer distributions of steam generators. Historical comparisons of 2 outage data revealed actual increase of deposit formations and provided useful information as an analysis tool for steam generator deposit formation monitoring and maintenance.

Advances in high frequency electronics, photonics and materials science as well as variety of possible applications enabled rapid development of terahertz technology in last decade. Research on reliable sources and detectors of electromagnetic waves in the terahertz range allows their application in various fields of science and technology ranging from medicine and biotechnology to pharmaceutical, chemical and material sciences. In this paper selected applications in nondestructive testing are shown, especially glass and basalt fiber-reinforced composites inspection as well as terahertz tomography.