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Ultrasound has long been used for inspecting parts without damaging them. Like a sonogram at the doctor's office, a gel-like couplant is applied to the surface and sound waves pulsed [...]

Poor-quality longitudinal joints can cause premature failure on asphalt pavements; they are characterized by exhibiting low density and high permeability. These conditions generate surface distresses such as longitudinal cracking. Previous ultrasonic methods for condition assessment, e.g., Fourier and wavelet transmission coefficient, require user input, making the automatic data processing difficult. Furthermore, the coupling between ultrasonic transducers and the asphalt surface is not practical for testing in-service roads. This paper presents a new data analysis technique and the results of an experimental program for the condition assessment of longitudinal asphalt joints using ultrasonic surface waves. A new coupling system between the ultrasonic transducers and the asphalt surface is presented. The new data processing technique reduces user input and increases testing reliability. The new coupling system uses polyurethane foam and calibrated weights to provide a spring action on the transducers. The proposed data analysis technique, called instantaneous transmission coefficient (ITC), is based on the evaluation of instantaneous frequencies and damping ratios. The main advantage of the new procedure is that it can be performed automatically, reducing user input and increasing test repeatability. A laboratory scale asphalt slab is used to show the potential of the new methodology and coupling system. Laboratory validation results show good agreement between the new ITC method and previous methods, and a significant reduction in testing time, while improving test reliability. Key words: nondestructive testing, asphalt pavement, longitudinal joints, surface waves, wavelet transform, Hilbert transform, Lamb modes. Une mauvaise qualite des joints de chaussee longitudinaux peut entrainer une deterioration prematuree des revetements en asphalte. Ces joints sont alors caracterises par une faible densite et une permeabilite elevee. De telles caracteristiques sont responsables d'alterations de surface telles que des fissures longitudinales. Les methodes d'evaluation de l'etat des joints de chaussee a l'aide d'ultrasons precedemment utilisees, telles que la determination des coefficients d'ondelettes et de Fourier, exigent la saisie des donnees par l'utilisateur, ce qui complique le traitement automatique de ces donnees. En outre, le couplage entre des transducteurs ultrasoniques et la surface en asphalte n'est pas commode dans le cas des essais effectues sur des routes en service. Le present article decrit une nouvelle technique d'analyse de donnees et les resultats d'un programme experimental d'evaluation de l'etat des joints longitudinaux en asphalte a l'aide d'ondes de surface ultrasonores. Le present article decrit un nouveau systeme de couplage entre des transducteurs ultrasoniques et la surface en asphalte. La nouvelle technique de traitement de donnees reduit la tache de saisie par l'utilisateur et accroit la fiabilite des essais. Ce nouveau systeme de couplage utilise de la mousse de polyurethane et des poids calibres pour produire un effet de ressort au niveau des transducteurs. La technique d'analyse de donnees proposee, nommee methode du coefficient de transmission instantane (CTI), est basee sur la mesure des frequences et rapports d'amortissement instantanes. Le principal avantage de cette technique est qu'elle peut etre utilisee automatiquement, ce qui reduit la tache de saisie des donnees par l'utilisateur et augmente la repetabilite des essais. Une dalle-test en asphalte est utilisee pour montrer les possibilites qu'offrent cette methode et ce systeme de couplage inedits. Les resultats de la validation en laboratoire de la nouvelle methode du CTO concordent bien avec ceux des methodes utilisees auparavant et mettent en evidence une reduction importante de la duree des evaluations et une amelioration de leur fiabilite. [Traduit par la Redaction] Mots-cles : essais non destructifs, revetement en asphalte, joints longitudinaux, ondes de surface, transformees d'ondelettes, transformee de Hilbert, modes de Lamb., Introduction Ultrasonic nondestructive testing (NDT) uses the propagation of different wave modes for the evaluation of the internal structure of materials. Technological developments in data collection, data acquisition equipment, and [...]

At the end of 2006, defects were identified using ultrasonic testing in three of the pressurizer nozzle dissimilar metal (DM) welds at the Wolf Creek nuclear power plant. Understanding welding residual stress is important in the evaluation of why and how these defects occur, which in turn helps to determine the reliability of nuclear power plants. This paper presents analytical predictions of welding residual stress in the surge nozzle geometry identified at Wolf Creek. The analysis procedure in this paper includes not only the pass-by-pass welding steps, but also other essential fabrication steps of pressurizer surge nozzles. Detailed welding simulation analyses have been conducted to predict the magnitude of these stresses in the weld material. Case studies were carried out to investigate the change in the DM main weld stress fields resulting from different boundary conditions, material strength, weld sequencing, as well as simulation of the remaining piping system stiffness. A direct comparison of these analysis methodologies and results has been made in this paper. Weld residual stress results are compared directly to those calculated by the nuclear industry. [DOI: 10.1115/1.4000701]

The main objective of this paper is to study the evolution of the ice content of porous media submitted to subzero temperatures by dielectric and ultrasonic measurements. Dielectric measurements are made by a capacitive sensor-based apparatus. The amount of ice formed within the tested sample is estimated from the global dielectric constants of the sample and of all the phases that form the tested composite material. On the other hand, ultrasonic measurements are based on the evolution of the ultrasonic wave velocity through the tested sample during a freezing-thawing cycle. These two methods lead to very close results and appear to be cheaper alternatives to low temperature calorimetry. The ice content curves are analyzed with the help of thermoporometry concepts in order to characterize the pore-size distribution. Results appear to be complementary to mercury intrusion porosimetry ones. Moreover, the commonly observed hysteresis of the ice content during a freezing-thawing cycle is investigated with respect to material microstructure. CE Database subject headings: Freeze-thaw; Pore size distribution; Hysteresis; Cement; Clays; Thermodynamics.

The alkali-aggregate reaction (AAR) has been detected in the spillway driftway of the Furnas Hydroelectric Power Plant, Brazil, which was built in 1963. To investigate the properties of this concrete, several cores were drilled in the affected structure and ultrasonic tests in association with mechanical tests were conducted. This paper presents the results of the following properties: splitting tensile strength, compressive strength, modulus of elasticity, and ultrasonic pulse velocity. For the ultrasonic tests, initial in situ determinations were performed on the driftway concrete surface under different exposure conditions before actual coring took place. The concrete cores drilled from the same location were tested by direct ultrasonic method before determining their mechanical properties. The ultrasonic results showed that the pulse velocity is sensitive to different degrees of deterioration due to AAR and correlates with the modulus of elasticity of the concretes investigated. Furthermore, the modulus of elasticity was the main property affected by AAR. CE Database subject headings: Deterioration; Mechanical properties; Ultrasonic methods; Damage; Assessments.

The partial discharge source localization by ultrasonic measurements in power transformers is studied by the Particle Swarm optimization (PSO), and the signal parameter estimated model of ultrasonic localization has been established on the basis of the propagation properties of the ultrasonic wave. The experiment result shows that the PSO algorithm possesses high calculation efficiency and high convergence speed, and can efficiently prevent the result from falling into the local optimum, the localization error of the PSO algorithm is clearly better than that of the Least-Square algorithm obviously. Index Terms--Power transformer, ultrasonic localization, partial discharge, particle swarm optimization.

Boiler piping of fossil-fuel combustion power generation plants are exposed to high-temperature and high-pressure environments, and failure of high-energy piping due to creep damage has been a concern. Therefore, a precise creep damage assessment method is needed. This paper proposes a nondestructive method for creep damage detection of piping in fossil-fuel combustion power generation plants by ultrasonic testing. Ultrasonic signals are transformed to signals in a frequency domain by Fourier transform, and a specific frequency band is chosen. To determine the creep damage, the spectrum intensities are calculated. Calculated intensities have a good correlation to life consumption of the weld joints, and this method is able to predict the remaining life of high-temperature piping, which has been already installed. [DOI: 10.1115/1.2767364] Keywords: nondestructive testing, frequency analysis, creep damage, maintenance, fossil-fuel combustion power generation plants, boiler piping, frequency spectral intensity, life consumption, ultrasonic testing

Ultrasound is a well-known diagnosis tool that can be used for the condition assessment of insulating systems. For this special purpose, various investigations on the detectability of the included inhomogeneities are performed: The resolution of ultrasonic measurements on high voltage insulations has been evaluated by using standardized Landolt rings in silicone rubber and epoxy resin. Although a dependency exists on the ring position, the diagnostic system that is used is able to image the gap with a sub-millimeter size. In other words, the system has recognition ability for two different objects close to such a distance. Regarding detectability, it has been found that in addition to ball-shaped inhomogeneities, the system can also detect thin fibrous objects with a diameter of a few micrometers. Finally, the results are used to detect and characterize electrical trees in silicone rubber. Index Terms: Diagnostics, ultrasound, electrical tree, insulating device.

The prototype of a guided ultrasonic wave array for the structural integrity monitoring of large, plate like structures is designed, built and tested. The array design consists of a ring of 32 transducers, permanently bonded to the structure with a protective membrane, in a compact housing with the necessary multiplexing electronics.

Air-coupled ultrasound is used for the nondestructive evaluation (NDE) of concrete, using broad bandwidth electrostatic transducers and chirp excitation. The benefits of using time-frequency analysis in such situations, for both waveform retrieval and imaging in the presence of low signal levels.

A method and an experimental setup is developed and tested to study the nonlinear behavior of fatigued and intact metal samples under high-frequency stresses. Two analytical models are proposed to explain the observed changes in the nonlinear behavior when fatiguing the samples.

A detailed study of small deviations from the presumed texture symmetry for rolled cubic metal sheets is allowed by an automated system for ultrasonic determination of texture. It is suggested that the asymmetry in the measured ultrasonic lamb wave velocities on either side of the rolling direction is due to a stress effect rather than crystallographic texture.

This paper addresses implementation of ultrasonic (UT) process qualification by performance demonstration as imposed by the ASME Boiler and Pressure Vessel Code Section XI, Appendix VIII. The intended audience for the present paper is an engineer with a good knowledge of NDE, but a limited knowledge of the ASME Codes and Standards. The starting point for application of UT performance demonstration is described in a paper published in this journal just over a decade ago by Cowfer and Hedden. That paper addressed the application of ultrasonic performance demonstration to qualify an examination process for ASME Code Section XI inservice inspection. The present paper provides a brief summary of papers specifically selected to provide the reader with a concise update of progress in UT performance demonstration since the earlier paper. Given that qualification, the reader should not expect new information in this present paper. The papers selected have been mostly selected from those presented at ASME Pressure Vessels and Piping Conferences, from 1995 to 2002, addressing the subsequent development and application of the UT performance demonstration process. The emphasis is on work performed for nuclear utilities under the Performance Demonstration Initiative (PDI), for application to Section XI inservice inspection. However, material also is included describing parallel work in the European Community, and applications of UT performance demonstration in Sections I and VIII of the ASME Boiler and Pressure Vessel Code, for use of UT in place of RT for new construction, are included. [DOI: 10.1115/1.1490932]

Following the Northridge earthquake, the quality and accuracy of the ultrasonic testing (UT) of structural steel connections, and the abilities of technicians to perform such testing, was drawn into question. In establishing new weld quality acceptance criteria and appropriate inspection guidelines, it was important to validate the ability, or lack thereof, of ultrasonic testing technicians to accurately characterize and locate weld flaws in a variety of welded joint types. Round-robin testing of mock-up specimens representative of a variety of common joints used in steel moment frames, fabricated with embedded discontinuities of known size, location, and orientation, were examined by a number of ultrasonic testing technicians. The inconsistencies noted in the test results indicate a need for more specific UT procedures when used for weld acceptance, and a need for validation of the skill level of the UT technicians in their ability to perform the inspections. CE Database keywords: Ultrasonic tests; Connections, welded; Inspection; Nondestructive tests; Steel structures; Seismic hazards.

Results show that the standard compressible turbulence model poorly predict the spreading rates of mixing layers and particularly so in the presence of large density ratios. The findings suggest that the model can be modified into subsonic and supersonic conditions for efficient mixing of the mixing layers with high-density variations.

An investigation of the acoustic velocity and acoustic attenuation of lead-vanadate glasses has been conducted. The study used ultrasonic methodology in temperatures ranging from 80 to 300 degrees Kelvin. The observed temperature dependence in attenuation can be rationalized in terms of relaxation process that is activated thermally while the velocity variation is attributed to the microscopic inhomogeneity of elasticity in glasses that is caused by anharmonicity, relaxation and frozen-in fluctuations.

In this paper, stress and displacement fields inside a multilayered plate are analytically computed. For the theoretical modeling, individual layers of the multilayered plate are assumed to be elastic and homogeneous, but anisotropic. These theoretical computations are then experimentally verified in a qualitative manner. Experimental investigations are carried out on a ceramic composite plate that has 12 plies of fibers going in 0 [degrees] and 90 [degrees] directions, [[0,90].sub.3s]. The incident angles and frequencies of the ultrasonic signal for generating different Lamb wave modes in this plate are obtained experimentally as well as from the theory. Displacement and stress fields inside the plate for some of these Lamb nodes are then computed. Computation of stress and displacement fields inside the plate is useful for studying the internal damage. Internal stress distribution varies significantly from one Lamb mode to another. Hence, different Lamb modes should detect defects in different layers of the plate. The Lamb mode that produces maximum stress in a specific layer should be most sensitive for detecting defects in that layer. This is observed experimentally as well.

Inspection and rating of public infrastructure has become a focus of many recent studies because of well-documented deterioration and failure case studies. A new indirect inspection technique using ultrasonic spread-spectrum methods can significantly improve distress identification and monitoring of deteriorating infrastructure. This paper presents the general concept and application of using a continuous spread-spectrum signal to test structural objects. First of all, the basic theory for this technique will be outlined. Secondly, the basic hardware setup will be described. And finally, the results of two laboratory experiments will be presented. The laboratory results indicate that this new method may be feasible for monitoring and evaluating existing large or complicated structural members. The method does, however, have its limitations, as the signal is very sensitive to transducer orientations, couplant, and ambient conditions as is the case in all contact transducer-based nondestructive evaluation techniques.

A non destructive evaluation technique has been developed to measure and analyze section loss due to corrosion for anchor rods used in guying steel transmission poles. The anchor guy system tested consists of a steel plate embedded in concrete connected to a steel rod buried in earth and attached to the guy wire from the pole. The method used was ultrasonics and specifically, the cylindrically guided wave technique (CGWT). Field correlation of the method was verified by digging up and inspecting several rods. This approach has optimized the ultimate replacement and maintenance expense.

This paper presents an experimental investigation of the use of an optical fiber laser phased array to measure solidified weld pool penetration depth in butt and v-groove joints. The purpose was to determine the optimum distances between the ultrasound source (the array), receiver, and the weld joint, in order to measure weld penetration depth. The relationship between penetration depth and wave amplitude was approximately linear. A narrow range of distances between the ultrasound receiver and weld joint permitted the ultrasonic system to detect penetration depth over the entire thickness of the base metal. Maximum resolution in measuring penetration depth was achieved by keeping the distance between the array and the weld joint as small as possible.

During nondestructive evaluation (NDE) of a material, an NDE instrument typically is used to receive the inspection signals and display them for visual interpretation. Work has been underway to convert these signals to a range of aural (audible) signals with the intent to enhance the accuracy of evaluation through the use of two senses (ears and eyes) instead of one. This paper describes auralization of ultrasonic NDE testing signals to improve characterization and evaluation of materials.

The acoustic velocity measurement technique for measuring the liquid-phase evolution during melt processing of high-temperature superconductoring tapes is described. The approach, which requires the use of an ultrasonic magnetostrictive transducer, is based on monitoring changes in the acoustic velocity of the tapes. As such, it is suitable for characterizing tapes prepared using the powder-in-tube method with respect to heat treatment time, temperature and oxygen partial pressure. To date, it has been applied to silver-sheathed tapes with Al2O3 and NaCl cores.

Nuclear reactors have many components within the reactor vessel. During the life of a reactor it is possible for these components to be displaced or deformed because of the thermal cycles to which they are subject. Also, these components are handled during refuellings and reconfigurations of the core. During these operations, damage is possible. Inspection of these components in si tu therefore becomes important for the upkeep of the reactor. However, high radiation levels make it difficult to monitor using optical methods. This paper describes an ultrasonic method which was successfully employed in profiling a deformed guide tube of a reactor. The method uses the well-known ultrasonic ranging technique. However, the speciality of the method is the use of air transducers at 40 kHz to overcome the inherent divergence problems and the difficulties associated with high temperatures inherent in a sodium cooled reactor.

A new type of focusing transducer for ultrasonic contact testing is introduced. It contains an acoustic contact lens whose geometry was designed for the generation and point-focusing of surface waves. Its design is employed to build a prototype for Rayleigh waves whose stress pattern on the transducer's symmetry axis may be described by a model. The modeling results, which show a good fit with experimental data, indicate that the new design can enhance the surface evaluation of thin laminated films.

An investigation into shear-horizontal (SH) surface waves propagating in a layered configuration of piezoelectric ceramics is carried out with respect to the currently known existence condition for the Love type wave. The study, which arose from the discovery of ferroelectric domain layer waves, provides a new existence condition for SH surface waves. The new criterion stipulates that SH surface waves can also be present when its velocity is below that of the phase velocities of volume shear waves in the substrate and layer, respectively.

Manufacturing installations in sectors such as petrochemical or power generation usually need to be cooled down for periodic inspections. Cooling down the installation, equipment inspection, and heating again contribute to [...]

This issue features the first AM & P Guide to Nondestructive Testing, a special section that we hope will be useful to many of our readers. The purpose of the […]

Cracks are public enemy number one when it comes to structural components. However, if we want to make reliable quantitative evaluations of cracks by fracture mechanics, we've been rather short [...]