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Two thermography techniques, passive and active, are used to detect damage initiation and progression in a cyclically loaded composite cylinder. The passive thermography tracks damage progression in real time during cyclic loading. Active flash thermography, using a flash tube enclosed within the cylinder, images delaminations. A differential thermography processing technique eliminates normal material variations and improves sensitivity to and sizing of delaminations. The thermography results were compared to non‐immersion ultrasonic results.

Most modern railways use Continuous Welded Rail (CWR). A major problem is the almost total absence of expansion joints that can create severe issues such as buckling in hot weather and breakage in cold weather. A related critical parameter is the rail Neutral Temperature (NT), or the temperature at which the net longitudinal force in the rail is zero. In June 2008 the University of California, San Diego (UCSD), under the sponsorship of a Federal Railroad Administration (FRA) Office of Research and Development (R&D) grant, began work to develop a technique for in‐situ measurement of NT and detection of incipient buckling in CWR. The method under investigation is based on ultrasonic guided waves, and the ultimate goal is to build and test a prototype that can be used in motion. A large‐scale full rail track (70 feet in length) has been constructed at UCSD’s Powell Structural Laboratories, the largest laboratories in the country for structural testing, to validate the NT measurement and buckling detection te...

Work is being conducted to develop phased array inspection of stainless steel welded pipes. Defects can occur anywhere along the weld fusion face. Optimum inspection performance across the entire weld face can be facilitated by collecting data as Full Matrix Capture (FMC) and applying a processing technique that allows focusing to be ideal for every pixel within the Bscan image. Further improvements to the Bscan image can be made by having a split aperture that varies as a function of focal depth. This paper introduces the FMC principle and describes the variable split aperture signal processing. The inspections were also modeled using the CEA CIVA software which was compared to experimental results.

In this paper, we propose a sizing methodology of pipe wall thinning using data acquisition by electromagnetic acoustic transducer (EMAT). First, a mathematical model of nondestructive test is given by eddy current systems and a linear elastic system. Secondly, an artificial corrosion is characterized by ellipsoid function with geometrical parameters. Thirdly, a parameter estimation problem is discussed using principle components analysis (POD). The proposed method deploys a reduced order model in order to save the computational cost of the forward analysis. Finally, an inverse analysis is performed for recovering corrosion shape using the measurement data.

Non‐oriented steels, with low carbon, are widely used in the fabrication of electrical motor nucleus. The performance of these motors is affected by the level of recrystallization. These steels can come from the steel plant in two different conditions: totally processed or semi‐processed. The semi‐processed steels have a partially deformed structure and are submitted to the final annealing process after reaching the end shape. An adequate annealing heat treatment is important to get an appropriate magnetic property. In the present study, samples of an electric steel, with the composition (0.05 wt% C, 1.28wt% Si, 0.29wt% Mn), cold rolled 50% in thickness, were withdrawn during the industrial heat treatment at temperatures of 575, 580, 600, 620 and 730 °C with the objective of evaluating the evolution of recrystalization with temperature. Magnetic properties were measured at room temperature in a vibrating sample magnetometer. Although the changes in magnetic hysteresis loop with temperature are difficult t...

The integration of magneto‐resistive sensors into eddy current probes can significantly expand the capabilities of conventional eddy current nondestructive evaluation techniques. The room temperature solid‐state sensors have typical bandwidths in the megahertz range and resolutions of tens of microgauss. The low frequency sensitivity of magneto‐resistive sensors has been capitalized upon in previous research to fabricate very low frequency eddy current sensors for deep flaw detection in multilayer conductors. In this work a modified probe design is presented to expand the capabilities of the device. The new probe design incorporates a dual induction source enabling operation from low frequency deep flaw detection to high frequency high resolution near surface material characterization. Applications of the probe for the detection of localized near surface conductivity anomalies are presented. Finite element modeling of the probe is shown to be in good agreement with experimental measurements.

A new laser‐based ultrasonic (LBU) receiver was recently introduced. The novel architecture is based on two‐wave mixing in photorefractive materials and allows simultaneous measurement of in‐plane and out‐of‐plane displacements (two‐ component). By taking advantage of recent developments in electronic processing and our knowledge on multi‐channel interferometer, we achieved a compact optical system using only a single collecting aperture and a single laser probe beam. We will characterize the system performances and present experimental results demonstrating the capability for this compact two‐component interferometer.

This paper describes a theoretical investigation into the behaviour of anisotropic welds under phased array inspection procedures using a 128 element linear array. Two advanced inspection techniques are simulated, and their suitability compared. A finite element (FE) model, configured in PZFlex, is used to represent both the variations in crystal orientation found in a typical anisotropic weld, and also the linear array configuration. Firstly, through transmission spectra of the weld are used to determine the optimum operating frequency and configuration of the array in order to detect a 3 mm SDH in the weld. Next, the Full Matrix Capture (FMC) technique is simulated, and an image of the weld constructed using the Total Focussing Method (TFM). This is accomplished by transmitting on each element sequentially, while receiving on the remaining 127 elements. This approach provides spatial averaging over the weld area, reducing the distortion caused by the anisotropic media. Finally, Time Reversal Acoustic (TRA) methods were employed to coherently focus the array at the defect and compensate for the elemental timing variations caused by the complex medium. Results illustrate the potential for inspecting anisotropic welds when using correctly designed arrays and implementing novel inspection procedures.

In this paper results of shallow outer flaw detection in thick titanium alloy specimens is presented. In order to increase efficiency of inspections of minor defects an eddy current measuring system with a lock‐in amplifier was used. The measurements were carried out for flat and cylindrical specimens with artificial flaws.

Multipass welds made in austenitic stainless steel, in the primary circuit of nuclear power plants with pressurized water reactors, are characterized by an anisotropic and heterogeneous structure that disturbs the ultrasonic propagation and challenge the ultrasonic non‐destructive testing. The simulation in this type of structure is now possible thanks to the MINA code which allows the grain orientation modeling taking into account the welding process, and the ATHENA code to exactly simulate the ultrasonic propagation. We propose studying the case where the order of the passes is unknown to estimate the possibility of reconstructing this important parameter by ultrasound measures. The first results are presented.

Early demonstrations of the use of models in the U.S. and U.K. to assist in the determination of NDE reliability and probability of detection (POD), as dictated by the advent of damage tolerant design, will be reviewed. A major motivation in the U.S. was the adoption of POD as the primary metric for effectiveness of an inspection and the empirical observation that field and depot inspections were not adequate so support the desired structural integrity. In parallel, a series of round robin trials in Europe raised issues with the effectiveness of nuclear power plant inspections, and the resulting concerns became an important part of the “Public Inquiry” in the UK regarding the construction of the Sizewell B power plant. In each country, physics‐based models of the inspection process became an important part of the response. This paper describes these early developments in the use of models to assess inspection reliability, contrasts the philosophies and approaches taken, and notes how these provide the ori...

The Laser induced Breakdown Spectroscopy (LIBS) is supplement and extension of standard chemical methods and SEM‐ or Micro‐RFA‐applications for the evaluation of building materials. As a laboratory method LIBS is used to gain color coded images representing composition, distribution of characteristic ions and/or ingress characteristic of damaging substances. To create a depth profile of element concentration a core has to be taken and split along the core axis. LIBS was proven to be able to detect all important elements in concrete, e. g. Chlorine, Sodium or Sulfur, which are responsible for certain degradation mechanisms and also light elements like lithium or hydrogen. Practical examples are given and a mobile system for on‐site measurements is presented.

In this paper we present a concept for an Intelligent System for Radiogram Analysis (ISAR) for welds quality inspection. Both, hardware and software solutions have been introduced in the system. The software operates with variety of scanner standards. It contains preliminary image processing (linear and nonlinear filtering algorithms) and some specialized functions, like Sauvola’s tresholding or IQI detection. The aim of the ISAR system is to support a radiologist in his work.

To increase the power generating capacity of a wind turbine composite turbine blade manufacturers have been increasing the size of blades. Current utility‐scale windmills are equipped with blades ranging from 40 m (130 ft) to 90 m (300 ft) in their sweep diameter. The increased blade size brings greater structural and safety demands. Recent blade recalls and field failures highlights the market need for sensors capable of part quality inspections on manufacturing line and for structural health monitoring (SHM) of the composites in service. An ultrasonic surface wave sensor technology based on interdigitization transduction (IDT) has been developed that can inspect and detect defects in the composite blades. The current work covers the design, fabrication, and characterization of the IDT sensors. The sensor characterization, coverage area, and detection capability for a variety of defects such as impact, cracking and delamination will be discussed.

Optical fiber sensors are ideal for monitoring continuous deterioration conditions of civil infrastructure, especially of long‐span bridges. Typically, a network of sensors is used to measure the strains or low frequency vibrational response of the structure. In this work, we demonstrate dynamic spectral demodulation of fiber Bragg grating (FBG) sensor responses with a stabilized Michelson interferometer for monitoring mechanical strains in a model of long‐span bridge. A series of experiments has been performed, including the measurements of the natural resonant modes of the model bridge, impact response of a bridge member and acoustic emissions in a fractured aluminum bar. The experimental results not only reveal that dynamic spectral demodulation of FBG strain responses at frequencies extending up to about 3.5 MHz is possible, but also suggest that the method may be suitable for monitoring high frequency mechanical strains in civil structures that result from cracking or impact loading, thus providing a tool for local detection of structural damage.

A laser ultrasonics system was used to detect impact damage in samples of composite material used in the Brazilian aeronautics industry. The ultrasonic generation was accomplished with a high power Nd:YAG laser at 1064 nm and the detector was a Mach‐Zehnder interferometer. The Nd:YAG laser was configured so as not to cause damage to the sample and a beam homogenizer was used to distribute the laser energy homogeneously over the optical spot cross section.

High‐precision magnetic field sensors are of increasing interest in non destructive testing (NDT). In particular GMR‐sensors (giant magneto resistance) are qualified because of their high sensitivity, high signal‐to‐noise ratio and high spatial resolution. With a GMR‐gradiometer and a 3D‐GMR‐magnetometer we performed magnetic flux leakage measurements of artificial cracks and cracks of a depth of ≤50 μm still could be dissolved with a sufficient high signal‐to‐noise ratio. A semi‐analytic magnetic dipole model that allows realistic GMR sensor characteristics to be incorporated is used for swiftly predicting magnetic stray fields. The reliable reconstruction based on measurements of artificial rectangular‐shaped defects is demonstrated.

Ap ipe with protective cladding and insulation was simplified to a four-layered structure when the diameter of a pipe is large enough, and analytical solutions for sinusoidal and pulsed wave excitation were derived. Simulation implemented by using the analytical solutions showed that sinusoidal excitation is not appropriate for the monitoring of inner thinning ,w hile pulsed eddy current method can be used to measure wall-thickness regardless of inner or outer thinning by using the decay rate of log(Bz) as a particular parameter to evaluate wall thickness.

A directional low‐frequency Alternating Current Potential Drop (ACPD) sensor was developed for in‐situ monitoring of creep in metals. The sensor relies on a modified ACPD technique that measures simultaneously both values of resistance in the axial and lateral directions using a square electrode configuration. As compared to the more commonly used in‐line electrode configuration, the square arrangement used in this sensor is much more directional and thus allows the detection of creep‐induced anisotropy and texture. The technique monitors the variation in the ratio of the measured axial and lateral resistances, therefore can efficiently separate the mostly isotropic common part of the resistivity variation caused by reversible temperature variations from the mostly anisotropic differential part caused by direct geometrical and indirect material effects of creep. Initially, this ratio is roughly proportional to the axial creep strain, while at later stages, the resistance ratio increases even faster with c...

3D finite difference modeling results showing the sensitivity of laser line thermography to cracks of varying lengths, depths and openings are presented. A novel crack imaging technique based on assembling second spatial derivative thermal images of a scanned laser line is presented. Experimental results show the technique to image cracks with openings of a few micrometres. The technique is found to have an imaging rate twenty times higher than that of scanning laser spot thermography.

This contribution presents results from studies investigating factors that influence the detection of surface breaking cracks using pulsed eddy current thermography. The influences of the current strength and crack orientation in both ferromagnetic and non‐ferromagnetic metals have been investigated. It has been found that crack detection is far more sensitive to crack orientation in non‐ferromagnetic metals than in ferromagnetic metals. The effects of crack size on detectability are presented for a large number of steel, nickel alloy and titanium samples. Results of studies comparing crack images obtained prior and after coating a nickel alloy sample with a thermal barrier coating are presented.

An experimental observation on a large welded plate found that the weld can concentrate and guide the energy of a guided wave traveling along the direction of the weld. An attractive shear weld guided mode was discovered by the authors, which is non‐attenuative and almost non‐dispersive. It is interesting to explore the possibilities of applying this mode as a screening tool to quickly inspect for defects along a long distance of the weld. In this work, the interaction of the shear weld guided mode with different types of defects has been studied, including cracks perpendicular or parallel to the weld and circular holes, in the heat affected zone next to the weld. The results are obtained from both Finite Element simulations and experimental measurements, showing good agreement. The sensitivity of the weld‐guided mode to different defects has been discussed and suitable choices of frequency to detect these defects have been suggested.

An industrial application of ultrasonic array imaging is the inspection of austenitic welds with high inhomogeneity and anisotropy. These result in attenuation and perturbation of the signals that adversely affects imaging performance. Here, the effects of perturbations introduced by an austenitic weld on array imaging performance are investigated experimentally. It is shown that three major factors contribute to the degradation of image quality: timing errors, phase errors, and multi‐path propagation and scattering.

We present development status and plans for NDE of graded material microstructures such as those found in dual microstructure turbine engine disks. These hybrid disks feature coarse grain microstructures in the rim for increased creep resistance and fine grain microstructures in the bore for optimal fracture toughness and fatigue resistance. Preliminary eddy current measurements and ultrasonic measurements, including longitudinal, shear, and Rayleigh wave velocity, frequency dependent attenuation, and backscattered grain noise resulted in clear identification of the coarse grain, transition, and fine grain regions, and are the basis for development of quantitative methods for NDE of microstructure.

The U.S. Nuclear Regulatory Commission established and coordinated the international Program for the Inspection of Nickel alloy Components (PINC). The goal of PINC was to evaluate the capabilities of various nondestructive examination (NDE) techniques to detect and characterize primary water stress corrosion cracking (PWSCC) in dissimilar metal welds. Round‐robin results showed that a combination of conventional and phased‐array ultrasound provide the highest performance for flaw detection and depth sizing in dissimilar metal piping welds. The effective detection of flaws in bottom‐mounted instrumentation penetrations by eddy current and ultrasound shows that it may be possible to reliably inspect these components in the field.

The nondestructive evaluation of nickel titanium (Ni‐Ti) alloys for applications such as heat treatment for biomaterials applications (dental) and welding was investigated. Ni‐Ti alloys and its ternary alloys are valued for mechanical properties in addition to the shape memory effect. Two analytical approaches were perused in this work. Assessment of the microstructure of the alloy that determines the martensitic start temperature (Ms) of Ni‐Ti alloy as a function of heat treatment, and secondly, an attempt to evaluate a Friction Stir Welding, which involves thermo‐mechanical processing of the alloy.

The present work refers to the welding inspection of the brackets of Atucha I Nuclear Power Plant’s Pressure Vessel (RPV) using the wet fluorescent magnetic particles technique (MT). Due to limited access and high radiation levels in the inspection area, it was necessary to automate the testing and use non conventional magnetization techniques. This paper describes the design and implementation of an automated inspection device and the tests carried out on the mock‐up to set up the system. Also, magnetization techniques used are described, explaining in detail the non conventional technique of magnetization by current plates and the use of magnetic field concentrators to increase the field values in the area of interest. Finally, the device mounted on the RPV, used to inspect the bracket’s weld, and the results achieved from the inspection are shown.

This paper explores the excitation probe excitation field invariance when the eddy current method is applied to detect, localize and characterize material defects in conductive nonmagnetic media. The cases relative to rotational symmetry in circular solenoidal probes and translation symmetry in constant field probes are presented. The experimental data shows that this theoretical treatment is useful to preview the behavior of these probes.

We apply N‐port theory to characterize a transmit‐receive (T/R) array of coils, in which two large transmit coils drive an 8×8 array of receiver, or sensor, coils. We introduce two systems of parameters that characterize N‐ports: open‐circuit driving‐point and transfer impedances, and chain‐matrix parameters. We then compare measured data with model data, and find equivalent electrical network representations for ‘parasitic clutter.’ Through the use of the chain‐matrix, we are able to remove the clutter, and leave a model response that can be further applied to model‐based inversion, though that is not dealt with in this paper.

This paper presents a characterization of machined long cracks by performing measurements at two different directions not necessarily orthogonal. The evaluation is using eddy current technique which is one of the most used non destructive evaluation methods for conductive materials using a giant magnetoresistor (GMR) sensor as the measuring device. A digital signal processor (DSP) is used to control the measuring system, to acquire and to process data.

This paper presents a new system for eddy current testing. The system enables tests with very short current impulses. Therefore, the frequency spectrum of the excitation signal is very wide. In this paper, a study of eddy current differential transducer for testing titanium element is also presented.

Structural health monitoring is a key factor in life cycle management of infrastructures. Truly distributed fiber optic sensors are able to provide relevant information on large structures, such as bridges, dikes, nuclear power plants or nuclear waste disposal facilities. The sensing chain includes an optoelectronic unit and a sensing cable made of one or more optical fibers. A new instrument based on Optical Frequency Domain Reflectometry (OFDR), enables to perform temperature and strainmeasurements with a centimeter scale spatial resolution over hundred of meters and with a level of precision equal to 1 μstrain and 0.1°C. Several sensing cables are designed with different materialstargeting to last for decades in a concrete aggressive environment and to ensure an optimal transfer of temperature and strain from the concrete matrix to the optical fiber. Tests were carried out by embedding various sensing cables into plain concrete specimens and representative-scale reinforced concrete structural elements. Measurements were performed with an OFDR instrument; meanwhile, mechanical solicitations were imposed to the concrete element. Preliminary experiments are very promising since measurements performed with distributed sensing system are comparable to values obtained with conventional sensors used in civil engineering and with the Strength of Materials Modelling. Moreover, the distributed sensing system makes it possible to detect and localize cracks appearing in concrete during the mechanical loading.

The quality of ultrasonic array imagery is adversely affected by uncompensated variations in the medium properties. A method for estimating the parameters of a general model of an inhomogeneous anisotropic medium is described. The model is comprised of a number of homogeneous sub‐regions with unknown anisotropy. Bayesian estimation of the unknown model parameters is performed via a Monte‐Carlo Markov chain using the Metropolis‐Hastings algorithm. Results are demonstrated using simulated weld data.

This paper presents results of an eddy current model validation study. Precise measurements were made using an impedance analyzer to investigate changes in impedance due to Electrical Discharge Machining (EDM) notches in aluminum plates. Each plate contained one EDM notch at an angle of 0, 10, 20, or 30 degrees from the normal of the plate surface. Measurements were made with the eddy current probe both scanning parallel and perpendicular to the notch length. The experimental response from the vertical and oblique notches will be reported and compared to results from different numerical simulation codes.

Submerged eddy current testing of zircaloy‐4 fuel cladding has been developed as a method of characterizing the hydrogen evolution within zircaloy‐4 fuel cladding in spent fuel pools. The parameters associated with storage in spent fuel pools must be incorporated and accounted for within the hydrogen content measurements. A focus on the effects of water and temperature must be incorporated and separated out of the hydrogen measurements. The use of submerged eddy current measurements to identify hydrogen content and hydride phases present in zircaloy‐4 fuel cladding will be presented.

Early fatigue crack growth behavior is an important aspect to the total fatigue life for many engineering applications. During a thermomechanical fatigue (TMF) test, crack inspections are commonly done in a disruptive manner using an acetate replication method; and post-test crack evaluations are done using both optical and scanning electronic microscope methods. This paper investigates a proof-of-concept technique for using induction thermography as a new in-situ, non-destructive inspection approach for use during TMF testing. The results obtained by induction thermography are compared to those obtained via the traditional acetate replication method and post-test scanning electron microscope (SEM) evaluation. The induction thermography inspections were carried out at several temperatures and show that the temperature used for the TMF test does not influence the crack detection capability. It is demonstrated that induction thermography can detect cracks smaller than 500 μm and has potential for quantifying the crack length. © 2011 American Institute of Physics., 37th Annual Review of Progress in Quantitative Nondestructive Evaluation, QNDE, 18 July 2010 through 23 July 2010, San Diego, CA, Series: AIP Conference Proceedings; no. 1335

A central issue in life extension for the current fleet of light water nuclear power reactors (LWR) is the early detection and monitoring of significant materials degradation. To meet this need, nondestructive methods that are suitable for continuous monitoring over extended time periods (months to years) are needed. A related issue is the ability to estimate remaining useful life (RUL) of components and systems based on condition assessment or degradation information. Monitoring for early detection of materials degradation requires novel sensors and enhanced data integration techniques. A range of acoustic and electromagnetic measurement methods may be suitable, including acoustic microscopy, eddy current and magnetic Barkhausen emission. Prognostic methods that predict rate of degradation and remaining life based on phenomena that can be described by linear elastic fracture mechanics have been reported by several researchers. However, the challenge of predicting remaining life starting from earlier phases of degradation is largely unsolved. This paper discusses an assessment of selected diagnostic techniques, and the application of Bayesian prognostic algorithms to detection of early degradation and rate of degradation/life prediction. Such measurement and modeling methods are expected to form the basis for a new range of advanced diagnostic and prognostic approaches for assessing and monitoring life extension of ageing light water reactors.

The ultrasonic wave field modeling reported in this paper has been undertaken with a view to optimizing the design of a conical scanning probe microscope tip to be used in measuring the near surface elastic properties of solids at high frequencies and high spatial resolution. The modeling is concerned with the evolution of a pulse which is launched from the upper spherical shaped surface of the tip, and is aimed at achieving the greatest possible concentration of acoustic energy at the lower sharp end of the tip. The calculations assume a transversely isotropic medium. Two complementary approaches have been taken, firstly the discretization of the equations of motion on a 1000×1000 mesh and solution using the commercial FE package ABAQUS, and secondly an analytical approach based on the angular spectrum method and stationary phase approximation. A high degree of consistency is achieved between the two approaches regarding the characteristics of the focal region, dispersion of the pulse attendant on the di...

Until recently, civil engineering material calibration data could only be obtained from material sample cores or via time consuming, stationary calibration measurements in a limited number of locations. Calibration data are used to determine material propagation velocities of electromagnetic waves in test materials for use in layer thickness measurements and subsurface imaging. Limitations these calibration methods impose have been a significant impediment to broader use of nondestructive evaluation methods such as ground‐penetrating radar (GPR). In 2006, a new rapid, continuous calibration approach was designed using simulation software to address these measurement limitations during a Federal Highway Administration (FHWA) research and development effort. This continuous calibration method combines a digitally‐synthesized step‐frequency (SF)‐GPR array and a data collection protocol sequence for the common midpoint (CMP) method. Modeling and laboratory test results for various data collection protocols and materials are presented in this paper. The continuous‐CMP concept was finally implemented for FHWA in a prototype demonstration system called the Advanced Pavement Evaluation (APE) system in 2009. Data from the continuous‐CMP protocol is processed using a semblance/coherency analysis to determine material propagation velocities. Continuously calibrated pavement thicknesses measured with the APE system in 2009 are presented. This method is efficient, accurate, and cost‐effective.

The assessment of corrosion requires the use of tools able to quantify the corrosion but often times also qualify it. Electrochemical Impedance Spectroscopy (EIS) is a laboratory tool that can provide both qualification and quantification of corrosion. EIS was successfully used to compare the thickness of the corrosion products formed during the application of different alternating current (AC) densities as well as to characterize pitting. When EIS is applied at the open circuit potential, the technique is nondestructive and predicts the corrosion behavior of the electrode. It can also be used at cathodic potentials while still being nondestructive, providing information about the electrode reaction kinetics, diffusion and electrical double layer.

Standard ultrasound methods using a phased‐array or a single transducer are commonly used for non‐destructive evaluation (NDE) during manufacturing of carbon fiber reinforced plastics (CFRP) parts and certificated testing schemes were developed for individual parts and geometries. However, most testing methods need direct contact, matching gels and remain therefore time consuming. Laser‐Ultrasonics is advantageous due to the contactless measurement technology and high accessibility even on complex parts. Despite the non‐destructive testing with body waves, we show that the NDE can be expanded using two‐dimensional surface (Lamb) waves for detection of delaminations close to the surface or small deteriorations caused by e.g. impacts. Lamb waves have been excited with a single transducer and with a short‐pulse Laser with additionally producing A0‐and S0‐Lamb waves. The waves were detected with a shearography setup that allows for measuring two‐dimensionally the displacement of a surface. Short integration t...

Interdigital transducers (IDT) generate and receive ultrasonic surface waves without the complexity involved with secondary devices such as angled wedges or combs. The IDT sensors have been successfully applied for the NDE of homogeneous materials like metals in order to detect cracks and de‐bond. However, these transducers have not been yet adapted for complex and anisotropic materials like fiber‐reinforced composites. This work presents the possibility of using IDT sensors for monitoring structural damages in wind turbine blades, typically made of fiberglass composites. IDT sensors with a range of operating frequency between 250 kHz and 1 MHz are initially tested on representative composite test panels for ultrasonic surface wave properties including beam spread, propagation distance and effect of material’s anisotropy. Based on these results, an optimum frequency range for the IDT sensor is found to be 250–500 kHz. Subsequently, IDT sensors with operating frequency 500 kHz are used to detect and quantify artificial defects created in the composite test samples. Discussions are made on the interaction of ultrasonic fields with these defects along with the effects of fiber directionality and composite layer stacking.

This contribution addresses ultrasonic inspection and evaluation of welds in large components. An approach has been developed in order to enhance the reliability of welded ship propellers. The Synthetic Aperture Focusing Technique (SAFT) has been modified with regard to the curved surfaces and the sound attenuation of cast Ni‐Al bronzes. For weld inspection in steels the Time‐of‐Flight Diffraction technique (TOFD) can provide additional information for specific defect orientations. Both techniques have been combined in view of the determination of defect sizes and shapes in longitudinal welds of pipes with diameters of up to 48 inches. Details on the inspection and evaluation concepts as well as experimental results are presented.

The use of non‐destructive evaluation (NDE) for defect detection and failure prediction in structures and specimens is widespread in energy industries, aimed at ageing power plants and pipelines, material degradation, fatigue and radiation damage, etc. At present there are no suitable electromagnetic NDE methods for the measurement and characterization of material degradation, in irradiated samples in particular, which is very important and timely for the nuclear power industry in the UK. This paper reports recent developments in the field of electromagnetic (EM) NDE at Newcastle University, including pulsed eddy current (PEC), pulsed magnetic flux leakage (PMFL), magnetic Barkhausen emission (MBE) and magneto‐acoustic emission (MAE). As different EM methods have different strengths, an integrative EM framework is introduced. Case studies through the second round robin tests organized by the Universal Network for Magnetic Non‐Destructive Evaluation (UNMNDE), representing eighteen leading research groups worldwide in the area of electromagnetic NDE, are reported. Twelve samples with different ageing times and rolling reduction ratios were tested using different magnetic methods among the UNMNDE members. Based on the studies, the complementary characteristics of electromagnetic techniques for NDE are discussed.

Corrosion and erosion shorten the life of components that are used in the petrochemical industry. In order to mitigate the safety and financial risks posed by the degradation mechanisms, plant operators monitor wall thicknesses at regular inspection intervals. In high temperature locations inspections have to be carried out at plant shut downs because conventional ultrasonic sensors cannot withstand the high operating temperatures. The authors have developed a waveguide based high temperature thickness gauge for monitoring of wall thicknesses in high temperature areas. The waveguide allows the use of conventional transduction systems (max temp. 60 °C) at one end and guides ultrasonic waves into the high temperature region where the inspection is to be carried out. Slender stainless steel waveguides allow a temperature drop of ∼500–600 °C per 200 mm length to be sustained simply by natural convection cooling. This paper describes the technical challenges that had to be overcome (dispersion and source/receiver characteristics) in order to implement this “acoustic cable”. A range of experimental results of thickness measurements on components of different thickness, and furnace tests at different temperatures are presented. An accelerated corrosion test that demonstrates the effectiveness of the monitoring for corrosion is also presented.

To achieve performance demonstration, which is a legal requirement for the qualification of NDE processes applied on French nuclear power plants, the use of modeling tools is a valuable support, provided that the employed models have been previously validated. To achieve this, in particular for eddy current modeling, a validation methodology based on the use of specific benchmarks close to the actual industrial issue has to be defined. Nonetheless, considering the high variability in code origin and complexity, the feedback from experience on actual cases has shown that it was critical to define simpler generic and public benchmarks in order to perform a preliminary selection. A specific Working Group has been launched in the frame of COFREND, the French Association for NDE, resulting in the definition of several benchmark problems. This action is now ready for mutualization with similar international approaches.

The inspection of welded austenitic stainless steel components can be challenging. Austenitic welds contain an anisotropic, inhomogeneous grain structure which causes attenuation, scattering and beam bending. The inspection of components where the weld cap has not been removed is even more difficult due to the irregularity of the surface geometry. A twin crystal membrane coupled device has now been produced containing two linear phased arrays positioned adjacent to one another within the same housing. The arrays are angled relative to one another so that the transducer provides a pseudo‐focusing effect at a depth corresponding to the beam crossing point. This type of design is used to improve the signal to noise ratio of the defect response in comparison to simple linear phased array transducer designs and to remove an internal noise signal found in linear phased array devices. Experimental results obtained from the through weld inspection of an austenitic stainless steel component with an undressed weld cap using the twin crystal membrane device are presented. These results demonstrate that small lack of side wall fusion defects can be reliably detected in large complex structures.

This work presents an experimental investigation of real‐time damage detection in overhead transmission lines using a guided wave system in a pitch and catch configuration. The system is composed of a transmitter module (based on a microcontroller) that excites 70 kHz guided wave energy pulses via an ultrasound transducer; the receiver is made of an ultrasound transducer and a processing microcontroller module, which performs real‐time damage detection. The receiver module is connected to a computer through a USB cable for continuous monitoring purposes. Experiments carried out in the laboratory, attaching the transducers to the periphery of a 1.4 m long ACSR cable, successfully detect a small 1.5 mm notch depth artificial damage.

The probabilistic collocation method (PCM) was introduced to efficiently propagate the distributions of input parameters for eddy current NDE inverse problems. A multilevel approach was also considered to simultaneously address input parameter variability and the uniqueness of the inversion result. A case study is presented for the problem of characterizing material loss in a multi‐layer structure with varying liftoff and material properties. The performance and sensitivity of the uncertainty propagation method using PCM was evaluated under varying conditions.

Waviness in glass fiber reinforced composite is of great interest in composite research, since it results in the loss of stiffness. Several NDE techniques have been used previously to detect waviness. This work is concerned with waves normal to the plies in a composite. Air‐coupled ultrasonics was used to detect waviness in thick composites used in the manufacturing of wind turbine blades. Composite samples with different wave aspect ratios were studied. Different wavy samples were characterized, and a three step process was developed to make sure the technique is field implementable. This gives us a better understanding of the effect of waviness in thick composites, and how it affects the life and performance of the composite.