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Full-Text Articles in Physics

Comparison Of Suppression Across Frequencies, Linda M. Thibodeau, Marc A. Fagelson Nov 1993

Comparison Of Suppression Across Frequencies, Linda M. Thibodeau, Marc A. Fagelson

Marc A. Fagelson

Although much research has focused on the temporal, spectral, and intensity relationships between a masker and a suppressor, there has been little attention directed towards relative amounts of suppression in different frequency regions. The purpose of this experiment was to compare the magnitude of suppression at 500 and 2000 Hz in two forward‐masking experiments with seven normal‐hearing persons. In the first experiment, the threshold for a 10‐ms probe was determined as the bandwidth of a 400‐ms masker increased from 0.05 to 1.6 times the probe frequency. Suppression was determined by observing a decrease in ...


Scattering Of A Sagittal Surface Acoustic Wave From A Large Amplitude Ridge Or A Deep Groove, A. Baghai-Wadji, A. A. Maradudin Jan 1993

Scattering Of A Sagittal Surface Acoustic Wave From A Large Amplitude Ridge Or A Deep Groove, A. Baghai-Wadji, A. A. Maradudin

Review of Progress in Quantitative Nondestructive Evaluation

In [1] we presented a Green’s function theory for obtaining the frequencies of acoustic surface shape resonances of sagittal polarization associated with an isolated ridge or groove of rather general shape on a planar, stress-free surface of an isotropic elastic medium (for details we refer to [2]). It was shown that employing Green’s second theorem, and using tensor Green’s functions associated with the boundary value problem, the initial coupled partial differential equations can be converted into a coupled system of integral equations. Further, it was shown that by discretizing the boundary and using the method of moments ...


Interaction Of Gaussian Acoustic Beams With Plane And Cylindrical Fluid-Loaded Elastic Structures, Jinguang Zhang, Dale E. Chimenti, Smaine Zeroug, Leopold B. Felsen Jan 1993

Interaction Of Gaussian Acoustic Beams With Plane And Cylindrical Fluid-Loaded Elastic Structures, Jinguang Zhang, Dale E. Chimenti, Smaine Zeroug, Leopold B. Felsen

Review of Progress in Quantitative Nondestructive Evaluation

Nonspecular reflection effects for ultrasonic beams incident from a fluid onto solid surfaces have been studied continuously since the early investigations by Schoch [1]. He calculated the reflected held for both the fluid-loaded halfspace and the plate using a series expansion for the phase of the reflection coefficient. A more accurate expression for Gaussian beam reflection has been derived by Bertoni and Tamir [2], who approximated the reflection coefficient by leading terms in a Laurent series, performing the resulting integrals analytically. Many researchers have contributed to this literature from the experimental [3–5], theoretical [6,7], and numerical sides [8 ...


Laser Generation Of Rayleigh And Lamb Waves For Ultrasonic Nondestructive Testing, R. Costley Jr., Yves H. Berthelot Jan 1993

Laser Generation Of Rayleigh And Lamb Waves For Ultrasonic Nondestructive Testing, R. Costley Jr., Yves H. Berthelot

Review of Progress in Quantitative Nondestructive Evaluation

Laser ultrasonics has been the focus of several research efforts over the last two decades. The main advantage of the technique is its noncontact nature which alleviates the problem of sensor coupling inherent in conventional techniques. However, laser ultrasonics has some limitations When operated in the thermoelastic regime, where no damage is inflicted on the surface of the specimen, the signal-to-noise ratio (SNR) is very small, particularly when compared with conventional piezoelectric generation.[1] Several authors have proposed increasing the SNR by producing a source with spatial periodicity designed to enhance a particular wavelength. Royer and Dieulasaint [2] have used ...


Laser Ultrasonic And Photoacoustic Characterization Of Subsurface Structures, Meng-Chou Wu, F. Raymond Parker, William P. Winfree Jan 1993

Laser Ultrasonic And Photoacoustic Characterization Of Subsurface Structures, Meng-Chou Wu, F. Raymond Parker, William P. Winfree

Review of Progress in Quantitative Nondestructive Evaluation

There is a strong interest in applying laser ultrasonic and photoacoustic techniques to the NDE of some high performance structures, for example, the actively cooled panels of the National Aero-Space Plane. Both laser ultrasonic and photoacoustic techniques have been developed for years. Much significant work has been done on either the generation of waves, the mechanisms [1–3] or various techniques for the detection of these waves [4–6]. A few applications being pursued or conducted since the early stage of the development for these techniques [5–7]. However, there is little work concentrating on the interaction of these waves ...


Ultrasonic Propagation Through A Surface With A Step Discontinuity: Validation Of A Hybrid, Gauss-Hermite Ray Tracing Beam Model, M. Greenwood, J.-L. Mai, A. Minachi, I. Yalda-Mooshabad, R. Bruce Thompson Jan 1993

Ultrasonic Propagation Through A Surface With A Step Discontinuity: Validation Of A Hybrid, Gauss-Hermite Ray Tracing Beam Model, M. Greenwood, J.-L. Mai, A. Minachi, I. Yalda-Mooshabad, R. Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

This research continues our cooperative effort to study the effects of large-scale surface roughness on ultrasonic transmission through interfaces and updates our previously-reported results [1], The Center for Nondestructive Evaluation has developed a model for the propagation of ultrasound through a surface and into an isotropic metal and this model is undergoing experimental validation at Battelle PNL. Once validated, this model will be used as an engineering tool to study the effects of surface conditions upon an ultrasonic inspection of nuclear reactor components. The goal is to quantify and develop requirements to limit the adverse effects of surface conditions during ...


Numerical Calculation Of Diffraction Coefficients In Anisotropic Media, J. Temple, L. White Jan 1993

Numerical Calculation Of Diffraction Coefficients In Anisotropic Media, J. Temple, L. White

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic inspection is used to detect and size crack-like defects in pressure vessels and pipework used in the nuclear industry. Reliable inspection can only be achieved if the inspection technique is understood, is optimised and subsequently applied correctly. Austenitic steels are used because of their corrosion resistance and toughness. Welds and centrifugally cast materials tend to crystallise with grains larger than the ultrasonic wavelength required to achieve the desired resolution in the inspection and thus appear anisotropic. Since the grains in a weld grow along the, varying, directions of maximum heat flux during cooling, the welds are inhomogeneous as well ...


Progress Towards The Application Of Laser-Ultrasonics In Industry, Jean-Pierre Monchalin Jan 1993

Progress Towards The Application Of Laser-Ultrasonics In Industry, Jean-Pierre Monchalin

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic techniques are widely used in industry for thickness gauging, flaw detection and materials characterization. The ultrasonic waves are usually generated and detected by piezoelectric transducers and coupled to the inspected part either by direct contact or through a water bath or a water jet. Although widespread and generally cost effective, these conventional ultrasonic techniques suffer from essentially two severe limitations, which impact upon their use for on-line process control and the inspection of advanced materials.


Rapid Inspection Of Composites Using Laser-Based Ultrasound, Andrew Mckie, Robert C. Addison Jr. Jan 1993

Rapid Inspection Of Composites Using Laser-Based Ultrasound, Andrew Mckie, Robert C. Addison Jr.

Review of Progress in Quantitative Nondestructive Evaluation

Current techniques for automated ultrasonic inspection of airframe structures can only be used to examine limited areas which have large radii of curvature. Manual inspection techniques are required in areas having small radii. Laser-based ultrasound (LBU) offers the potential to rapidly inspect large-area composite structures having contoured geometries, without restriction to large radii of curvature [1–4]. The key components that comprise an LBU rapid inspection system are the generation and detection lasers, a 2D scanner and a suitably fast data acquisition system. These must be integrated to provide an areal scan rate of at least 100 ft2/hr based ...


Source Efficiency And Sensor Detectability Factors In Laser Ultrasonics, James Wagner Jan 1993

Source Efficiency And Sensor Detectability Factors In Laser Ultrasonics, James Wagner

Review of Progress in Quantitative Nondestructive Evaluation

Perhaps the greatest fundamental deterrent to the application of current laser ultrasonic technology has been the fact that the detection sensitivity or detectability of laser receiver systems, compared with their piezoelectric counterparts, is rather poor. That is to say that in general, and especially on a dollar-for-dollar basis, piezoelectric transducers are able to detect much smaller surface displacements than can easily be detected by laser methods. As will be discussed shortly, there are several strategies which may be used to overcome these detectability shortcomings. Indeed, several of these strategies have been investigated at the laboratory level and some implemented in ...


Improved Laser Interferometry For Ultrasonic Nde, Peter Nagy, Gabor Blaho, Laszlo Adler Jan 1993

Improved Laser Interferometry For Ultrasonic Nde, Peter Nagy, Gabor Blaho, Laszlo Adler

Review of Progress in Quantitative Nondestructive Evaluation

In spite of its obvious advantages over conventional contact and immersion techniques, laser interferometry has not yet become a practical tool in ultrasonic nondestructive evaluation since its sensitivity is insufficient in most practical applications. Part of the problem is that the maximum signal-to-noise ratio often cited in scientific publications and manufacturers’ specifications cannot be maintained on ordinary diffusely reflecting surfaces. Although these surfaces reflect a fair amount (5–50%) of the incident laser light, this energy is randomly distributed among a large number of bright speckles. Unless the detector happens to see one of these bright speckles, the interferometer’s ...


Laser Ultrasound For The Study Of Thin Sheets, C. Edwards, A. Al-Kassim, S. B. Palmer Jan 1993

Laser Ultrasound For The Study Of Thin Sheets, C. Edwards, A. Al-Kassim, S. B. Palmer

Review of Progress in Quantitative Nondestructive Evaluation

Laser ultrasound is now an accepted and mature technology. However it is still seeking its first fully commercial industrial application although there are several potential uses in prototype form. The major advantage of laser ultrasound is that it is a non contact technique and can therefore be used on hot or moving components. The pulsed laser source generates simultaneously longitudinal and shear bulk waves and Rayleigh surface waves. When the material is in the form of a thin sheet the latter propagate as Lamb or plate waves providing the ultrasonic wavelength is greater than the sheet thickness.


Laser Ultrasonics For Coating Thickness Evaluation At 1200°C, H. Ringermacher, F. A. Reed, J. R. Strife Jan 1993

Laser Ultrasonics For Coating Thickness Evaluation At 1200°C, H. Ringermacher, F. A. Reed, J. R. Strife

Review of Progress in Quantitative Nondestructive Evaluation

Laser ultrasonics has come of age in such diverse industrial applications as in-process evaluation during steel processing[1] and composite air frame inspection[2,3]. This approach generally offers certain unique advantages for process evaluation and diagnostics. It is a noncontact, largely contour independent, technique ideally suited for hostile environments.


Thermoelastic Sound Source: Waveforms In A Sensing Application, Markku Oksanen, R. Lehtiniemi, J. Wu Jan 1993

Thermoelastic Sound Source: Waveforms In A Sensing Application, Markku Oksanen, R. Lehtiniemi, J. Wu

Review of Progress in Quantitative Nondestructive Evaluation

Photoacoustically generated sound pulses are widely used in various NDT, NDE and sensing applications when a non-touching method is preferred. The generation mechanisms are relatively well known, including types of waves generated, directional patterns, sound pressures and damage thresholds for the laser intensity [1]. The so-called thermoelastic regime is attractive to many applications despite of its low efficiency (usually about sub 0.1%). It is because that the process is nondestructive to samples and the theory is well established [2,3,4]. The current study addresses the prediction of the temporal ultrasound pulse shape of an optimum sound generation scheme ...


Reception Of Laser Generated Ultrasound From A Cfrp Plate By An Air Matched Piezoelectric Composite Transducer, L. Scudder, D. A. Hutchins, G. Hayward Jan 1993

Reception Of Laser Generated Ultrasound From A Cfrp Plate By An Air Matched Piezoelectric Composite Transducer, L. Scudder, D. A. Hutchins, G. Hayward

Review of Progress in Quantitative Nondestructive Evaluation

Laser generated ultrasound is being investigated [1,2] for testing structures made of both conventional metals and carbon fibre reinforced polymer (CFRP). Laser interferometers are widely used in such work to detect the normal surface motion caused by ultrasonic pulses. Interferometers offer non-contact, remote and high-fidelity detection, together with a potential to cover large areas rapidly by optical scanning. However their cost is high and only in testing large and/or expensive structures may the cost be justified. A lower cost alternative, but with some compromise on the virtues of an interferometer, would be to use an air transducer as ...


An Actively-Stabilized Fiber-Optic Interferometer For Laser-Ultrasonic Flaw Detection, S. Pierce, R. E. Corbett, R. J. Dewhurst Jan 1993

An Actively-Stabilized Fiber-Optic Interferometer For Laser-Ultrasonic Flaw Detection, S. Pierce, R. E. Corbett, R. J. Dewhurst

Review of Progress in Quantitative Nondestructive Evaluation

Laser ultrasound for NDE applications is reported in several places within this Review. Interest in the subject remains high, even though the cost of associated instrumentation remains high. Benefits associated with optical probing of a sample include potentially high spatial resolution, truly non-contacting transduction permitting non-contact C-scan inspection systems, and the possibility of probing structures having awkward surface shapes. Non-contact imaging systems were first reported at an earlier review [1]. Images of defects in carbon-fiber composite samples have been demonstrated in both reflection mode and more recently in transmission mode [2]. In all cases, such experiments have been conducted using ...


Visualization Of Laser Generated Ultrasound In A Solid, A Liquid And In Air, D. Billson, D. A. Hutchins Jan 1993

Visualization Of Laser Generated Ultrasound In A Solid, A Liquid And In Air, D. Billson, D. A. Hutchins

Review of Progress in Quantitative Nondestructive Evaluation

A laser pulse incident on a bulk medium produces a very complex ultrasonic field, which is often further complicated by phenomena such as mode conversion, surface waves and plate waves. The propagating ultrasonic wavefronts have been modelled using computer intensive techniques, but it was thought that a method of directly observing the ultrasound could give a much clearer understanding of how the field propagates through various media.


Crack Detection In Fuselage Panels By A Narrow-Band Laser-Based Ultrasonic System, Jin Huang, Sridhar Krishnaswamy, Jan D. Achenbach Jan 1993

Crack Detection In Fuselage Panels By A Narrow-Band Laser-Based Ultrasonic System, Jin Huang, Sridhar Krishnaswamy, Jan D. Achenbach

Review of Progress in Quantitative Nondestructive Evaluation

Surface acoustic waves can be used for the characterization of mechanical properties of materials, as well as to investigate the near-surface region of a solid for cracks and other flaws by probing for the presence of scattering sources. In the non-destructive characterization of solids, laser generation of ultrasound as well as interferometric detection of the surface waves are particularly attractive in view of the non-contacting nature of such systems. In recent studies, accurate detection of surface wave speed and attenuation have been shown to be possible by the use of dual-probe laser interferometers[1,2]. A number of authors have ...


Laser Ultrasonic Inspection Of Honeycomb Aircraft Structures, F. P. Chang, T. E. Drake, M. A. Osterkamp, Jean-Pierre Monchalin, R. Heon, P. Bouchard, C. Padioleau, D. A. Froom, W. Frazier, J. Barton Jan 1993

Laser Ultrasonic Inspection Of Honeycomb Aircraft Structures, F. P. Chang, T. E. Drake, M. A. Osterkamp, Jean-Pierre Monchalin, R. Heon, P. Bouchard, C. Padioleau, D. A. Froom, W. Frazier, J. Barton

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic methods have been used extensively for the inspection of advanced composite materials and adhesively bonded structures. Conventional ultrasonic inspections usually require couplants to propagate ultrasonic waves to and from the part surface. Delaminations, porosities, and foreign inclusions in composite laminates can be successfully detected by pulsed-echo and through-transmission modes of ultrasonic inspection. Debonds in adhesively bonded structures are most effectively detected by the through-transmission mode of ultrasonic inspection.


Ultrasonic Beam Propagation Through A Bimetallic Weld — A Comparison For Predictions Of The Gauss-Hermite Beam Model And Finite Element Method, A. Minachi, J. Mould, R. Bruce Thompson Jan 1993

Ultrasonic Beam Propagation Through A Bimetallic Weld — A Comparison For Predictions Of The Gauss-Hermite Beam Model And Finite Element Method, A. Minachi, J. Mould, R. Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

To ensure safe operation, nuclear power plants must be inspected periodically. One of the most commonly used nondestructive inspection methods uses ultrasound to detect internal flaws. However, the complex structure of some joints between different components greatly complicates the ultrasonic inspection. These joints, which consist of welds with varying and sometimes anisotropic elastic properties, can distort the ultrasonic beam and produce unreliable results. To understand the propagation of elastic waves through such materials, beam models are used.


Full Characterization Of Near-Surface Flaws With Multimode Straight-Beam Transducers, G. Gruber, S. R. Burger Jan 1993

Full Characterization Of Near-Surface Flaws With Multimode Straight-Beam Transducers, G. Gruber, S. R. Burger

Review of Progress in Quantitative Nondestructive Evaluation

Reliable and accurate characterization as to type (cracks vs. others), location (highly stressed zone or not), and size of potential flaws in cladded pressure vessels by ultrasonic methods ensures the integrity of these structures. Vessel integrity is primarily affected by the presence of fatigue cracks in the highly stressed near- surface regions (Zones 1 and 2). While there have been some new high- and low- beam multimode transducer developments for characterizing Zone 2 (underclad) and Zone 3 (deeply buried) flaws, respectively [1,2], emphasis has recently been placed upon fully characterizing manufacturing flaws in the cladding (Zone 1) because they ...


Thermal Coating Characterization Using Thermoelasticity, Christopher S. Welch, Michael J. Zickel Jan 1993

Thermal Coating Characterization Using Thermoelasticity, Christopher S. Welch, Michael J. Zickel

Review of Progress in Quantitative Nondestructive Evaluation

Synchronous demodulation techniques have been used for some time to measure thermal radiation produced by the small temperature changes associated with elastic stress in materials, the thermoelastic effect[l]. As reviewed in [2], these measurements have been employed primarily for inferring stress distributions in materials from the associated temperature distributions. Images of stress distribution have been made most often by assembling a large number of individual synchronous component measurements using specialized equipment [3]. Other investigators [4,5] have used subtraction of stroboscopic samples to build up similar images. Recently, techniques using full-field synchronous demodulation [6,7] have been reported using ...


Fast Photothermal Inspection Of Plasma-Sprayed Coatings Of Primary Circulation Seal Rings Of A Nuclear Reactor. Part Two: After The Trial Run, R. Lehtiniemi, J. Hartikainen, J. Rantala, J. Varis, M. Luukkala Jan 1993

Fast Photothermal Inspection Of Plasma-Sprayed Coatings Of Primary Circulation Seal Rings Of A Nuclear Reactor. Part Two: After The Trial Run, R. Lehtiniemi, J. Hartikainen, J. Rantala, J. Varis, M. Luukkala

Review of Progress in Quantitative Nondestructive Evaluation

In the 1991 QNDE conference [1] we described a photothermal inspection of the plasma-sprayed coatings of two seal rings used in the main pump of the primary circulation in the PWR-type nuclear reactor. The measurements concentrated on detecting the most critical flaw type, adhesion defects at the interface between the coating and the substrate. The samples were tested immediately after they were coated and lapped, and already then two thermal anomalies could be found.


An Experimental Method For Structural Intensity And Source Location , Yong Zhang Jan 1993

An Experimental Method For Structural Intensity And Source Location , Yong Zhang

Retrospective Theses and Dissertations

This study investigates the structural intensity and the force distribution function as tools to study vibrating plates. A laser Doppler vibrometer is used in measuring the plate normal velocity for the calculation of the structural intensity and the force distribution function. Several examples show the possibility of locating sources and studying the influence of ribs and damping material attached to the plate surface;There have been many studies on structural intensity. This thesis shows that the differences between two commonly used formulations are the assumptions that are used in deriving the formulas;The force distribution function is introduced in this ...


Effects Of Randomly Rough Surfaces On Ultrasonic Inspection , Mehmet Bilgen Jan 1993

Effects Of Randomly Rough Surfaces On Ultrasonic Inspection , Mehmet Bilgen

Retrospective Theses and Dissertations

Surface finish of an industrial part affects its ultrasonic inspection and consequently the surfaces are often machined smooth before the evaluation. Ultrasonic inspection through smooth surfaces has been well studied and understood. A theoretical basis has been established for the characterization of interior cracks, voids and inclusions, and vast amount of literature exists. However, much less is known about quantitative ultrasonic inspection of such flaws in parts with rough surfaces, e.g. machine marks or "as-cast" surfaces. A question arises "When can an industrial part with randomly rough surfaces be inspected robustly using ultrasound?" This dissertation is aimed at answering ...


Support Minimized Inversion Of Acoustic And Elastic Wave Scattering , Ali Safaeinili Jan 1993

Support Minimized Inversion Of Acoustic And Elastic Wave Scattering , Ali Safaeinili

Retrospective Theses and Dissertations

Inversion of limited data is common in many areas of NDE such as X-ray Computed Tomography (CT), Ultrasonic and eddy current flaw characterization and imaging;In many applications, it is common to have a bias toward a solution with minimum (L[superscript]2)[superscript]2 norm without any physical justification. When it is a priori known that objects are compact as, say, with cracks and voids, by choosing "Minimum Support" functional instead of the minimum (L[superscript]2)[superscript]2 norm, an image can be obtained that is equally in agreement with the available data, while it is more consistent ...


Vibrational And Acoustic Response Of Ribbed Plates , Ten-Bin Juang Jan 1993

Vibrational And Acoustic Response Of Ribbed Plates , Ten-Bin Juang

Retrospective Theses and Dissertations

A self-consistent mathematical formulation, using the Fourier transform method and a direct Gaussian numerical integration scheme, is developed and verified for analysis of both vibrational and acoustic responses of infinite submerged ribbed plates. Further steps developed from standard theories make structural intensity, acoustic intensity, and acoustic power calculations possible in the nearfield and farfield, and are demonstrated in this work;The direct numerical integration scheme adopted to obtain responses has proved to be straightforward and reliable. Although the double integration expression in some responses makes the technique infeasible, a practical way to overcome that difficulty is demonstrated using a standard ...


Carbon In Fly Ash Analysis Using Photoacoustic Spectroscopy , Jeffrey Raymond Dykstra Jan 1993

Carbon In Fly Ash Analysis Using Photoacoustic Spectroscopy , Jeffrey Raymond Dykstra

Retrospective Theses and Dissertations

Photoacoustic absorption spectroscopy (PAS) was investigated as a method for on-line monitoring of carbon in fly ash from coal-fired boilers. PAS is based on the periodic heating of a gas when amplitude-modulated radiation is absorbed by the gas or by particles suspended in the gas. This periodic heating produces an acoustical wave that can be detected by a microphone. Because the PAS signal is based solely on the absorption of radiation (by carbon) and not scattering of radiation (by mineral matter), it has the potential for distinguishing unburned carbon from mineral matter suspended in the flue gas. Two radiation sources ...


Scattering Investigation Based On Acoustical Holography , Ming-Te Cheng Jan 1993

Scattering Investigation Based On Acoustical Holography , Ming-Te Cheng

Retrospective Theses and Dissertations

The objective of this research is to investigate sound scattering by an object using a two-surface measurement technique that separates the incident field and the scattered field. The separation technique is developed in cartesian and cylindrical coordinates. The decomposition method in the cartesian coordinate system is based on the principle that any wave form can be decomposed into plane-wave components by using a two dimensional spatial Fourier transform. For the cylindrical coordinate system, a two plane separation technique is based on decomposing the sound field into cylindrical waves. Numerical simulations are performed and the effect of various parameters are investigated ...


Acoustically Driven Integrated Microstrip Antennas And Electromagnetic Radiation From Piezoelectric Devices , Charles Forrest Campbell Jan 1993

Acoustically Driven Integrated Microstrip Antennas And Electromagnetic Radiation From Piezoelectric Devices , Charles Forrest Campbell

Retrospective Theses and Dissertations

For a receiver system to be considered integrated, the antenna and electronics need to be fabricated on a single semiconductor wafer. To avoid EMI problems, the circuitry must somehow be shielded from the environment where the antenna resides. The required shielding may be accomplished by separating the antenna on one side of the wafer from the electronics on the other side with a conducting ground plane. Energy may be acoustically coupled from the antenna to the circuitry through the ground plane via thin film piezoelectric transducers on either side of the wafer. The radiating side of the wafer would then ...