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Full-Text Articles in Physics

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 ...


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.


Beam Profile Reflectometry: A New Technique For Thin Film Measurements, J. Fanton, J. Opsal, D. L. Willenborg, S. M. Kelso, Allan Rosencwaig Jan 1993

Beam Profile Reflectometry: A New Technique For Thin Film Measurements, J. Fanton, J. Opsal, D. L. Willenborg, S. M. Kelso, Allan Rosencwaig

Review of Progress in Quantitative Nondestructive Evaluation

In the manufacture of semiconductor devices, it is of critical importance to know the thickness and material properties of various dielectric and semiconducting thin films. Although there are many techniques for measuring these films, the most commonly used are reflection spectrophotometry [1,2] and ellipsometry [3]. In the former method, the normal- incidence reflectivity is measured as a function of wavelength. The shape of the reflectivity spectrum is then analyzed using the Fresnel equations to determine the thickness of the film. In some cases, the refractive index can also be determined provided that the dispersion of the optical constants are ...


Nonspecular Reflection Of Rotationally Symmetric Gaussian Beams From Shaped Fluid-Solid Interfaces, Smaine Zeroug, Leopold B. Felsen Jan 1993

Nonspecular Reflection Of Rotationally Symmetric Gaussian Beams From Shaped Fluid-Solid Interfaces, Smaine Zeroug, Leopold B. Felsen

Review of Progress in Quantitative Nondestructive Evaluation

Nonspecular reflection, which occurs when an incident beam is phase matched to a leaky wave, is an important tool for fluid-solid interface diagnostics. A recently developed complex ray analysis for modeling nonspecular reflection of two-dimensional Gaussian sheet beams [1,2] is here extended to account for rotationally symmetric three-dimensional (3D) Gaussian beams (GBs) with arbitrary collimation. As in our 2D analysis, we utilize the complex-source-point (CSP) technique by which a conventional point-source-excited field can be converted into a 3D quasi-Gaussian beam field by displacing a real point source to a complex location [3]. When the CSP field excited in the ...


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 ...


Absolute-Convective Instabilities And Their Associated Wave Packets In A Compressible Reacting Mixing Layer, F. Q. Hu, T. L. Jackson, D. G. Lasseigne, C. E. Grosch Jan 1993

Absolute-Convective Instabilities And Their Associated Wave Packets In A Compressible Reacting Mixing Layer, F. Q. Hu, T. L. Jackson, D. G. Lasseigne, C. E. Grosch

Mathematics & Statistics Faculty Publications

In this paper the transition from convective to absolute instability in a reacting compressible mixing layer with finite rate chemistry is examined. The reaction is assumed to be one step, irreversible, and of Arrhenius type. It is shown that absolute instability can exist for moderate heat release without backflow. The effects of the temperature ratio, heat release parameter, Zeldovich number, equivalence ratio, direction of propagation of the disturbances, and the Mach number on the transition value of the velocity ratio are given. The present results are compared to those obtained from the flame sheet model for the temperature using the ...


Erratum: "Temperature And Suction Effects On The Instability Of An Infinite Swept Attachment Line" [Physics Of Fluids A 4, 2008 (1992)], D. G. Lasseigne, T. L. Jackson, F. Q. Hu Jan 1993

Erratum: "Temperature And Suction Effects On The Instability Of An Infinite Swept Attachment Line" [Physics Of Fluids A 4, 2008 (1992)], D. G. Lasseigne, T. L. Jackson, F. Q. Hu

Mathematics & Statistics Faculty Publications

Erratum to:

Lasseigne, D. G., Jackson, T. L., & Hu, F. Q. (1992). Temperature and suction effects on the instability of an infinite swept attachment line. Physics of Fluids A: Fluid Dynamics, 4(9), 2008-2012. doi:10.1063/1.858370


Glow-Discharge Enhanced Permeation Of Oxygen Through Silver, D. Wu, R. A. Outlaw, Robert L. Ash Jan 1993

Glow-Discharge Enhanced Permeation Of Oxygen Through Silver, D. Wu, R. A. Outlaw, Robert L. Ash

Mechanical & Aerospace Engineering Faculty Publications

The permeation of oxygen through Ag0.05Zr over the temperature range of 300-650°C under glow-discharge conditions has been studied and compared to the permeation of thermally dissociated molecular oxygen. A low-energy dc glow-discharge in O2 has been employed which produced approximately 10% atoms. The permeation rate during the glow discharge was found to be much higher (a factor of ∼10) than without the glow discharge. The small fraction of oxygen atoms generated appears to dominate the permeation because of much higher solution probabilities. Below 500°C, the activation energy for the permeation with glow discharge was found to ...


A Numerical Study Of Wave Propagation In A Confined Mixing Layer By Eigenfunction Expansions, Fang Q. Hu Jan 1993

A Numerical Study Of Wave Propagation In A Confined Mixing Layer By Eigenfunction Expansions, Fang Q. Hu

Mathematics & Statistics Faculty Publications

It is well known that the growth rate of instability waves of a two-dimensional free shear layer is reduced greatly at supersonic convective Mach numbers. In previous works, it has been shown that new wave modes exist when the shear layers are bounded by a channel due to the coupling effect between the acoustic wave modes and the motion of the mixing layer. The present work studies the simultaneous propagation of multiple stability waves using numerical simulation. It is shown here that the coexistence of two wave modes in the flow field can lead to an oscillatory growth of disturbance ...


Induced Mach Wave-Flame Interactions In Laminar Supersonic Fuel Jets, F. Q. Hu, T. L. Jackson, D. G. Lasseigne, C. E. Grosch Jan 1993

Induced Mach Wave-Flame Interactions In Laminar Supersonic Fuel Jets, F. Q. Hu, T. L. Jackson, D. G. Lasseigne, C. E. Grosch

Mathematics & Statistics Faculty Publications

A model problem is proposed to investigate the steady response of a reacting, compressible laminar jet to Mach waves generated by wavy walls in a channel of finite width. The model consists of a two-dimensional jet of fuel emerging into a stream of oxidizer which are allowed to mix and react in the presence of the Mach waves. The governing equations are taken to be the steady parabolized Navier-Stokes equations which are solved numerically. The kinetics is assumed to be a one-step, irreversible reaction of the Arrhenius type. Two important questions on the Mach wave-flame interactions are discussed: (i) how ...


A Study Of The Guiding Center Approximation, Qun Yao Jan 1993

A Study Of The Guiding Center Approximation, Qun Yao

Dissertations, Theses, and Masters Projects

A Hamiltonian treatment for the motion of a charged particle in a toroidal magnetic field is given. Assuming the plasma equilibrium, Boozer coordinates are used. The Hamiltonian of the exact trajectory is given in the guiding center coordinates. The higher order corrections to the standard drift Hamiltonian are derived. It is shown that the exact Hamiltonian depends on both the field strength and the shape of the magnetic surfaces (the metric of Boozer coordinates) while the standard drift Hamiltonian depends only on the field strength. The first order correction to the standard drift Hamiltonian, in gyroradius to system size, depends ...