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Full-Text Articles in Physics

Equation Of State Of Boron Nitride Combining Computation, Modeling, And Experiment, Shuai Zhang, Amy Lazicki, Burkhard Militzer, Lin H. Yang, Kyle Caspersen, Jim A. Gaffney, Markus W. Däne, John E. Pask, Walter R. Johnson, Abhiraj Sharma, Phanish Suryanarayana, Duane D. Johnson, Andrey V. Smirnov, Philip A. Sterne, David Erskine, Richard A. London, Federica Coppari, Damian Swift, Joseph Nilsen, Art J. Nelson, Heather D. Whitley Apr 2019

Equation Of State Of Boron Nitride Combining Computation, Modeling, And Experiment, Shuai Zhang, Amy Lazicki, Burkhard Militzer, Lin H. Yang, Kyle Caspersen, Jim A. Gaffney, Markus W. Däne, John E. Pask, Walter R. Johnson, Abhiraj Sharma, Phanish Suryanarayana, Duane D. Johnson, Andrey V. Smirnov, Philip A. Sterne, David Erskine, Richard A. London, Federica Coppari, Damian Swift, Joseph Nilsen, Art J. Nelson, Heather D. Whitley

Ames Laboratory Accepted Manuscripts

The equation of state (EOS) of materials at warm dense conditions poses significant challenges to both theory and experiment. We report a combined computational, modeling, and experimental investigation leveraging new theoretical and experimental capabilities to investigate warm-dense boron nitride (BN). The simulation methodologies include path integral Monte Carlo (PIMC), several density functional theory (DFT) molecular dynamics methods [plane-wave pseudopotential, Fermi operator expansion (FOE), and spectral quadrature (SQ)], activity expansion (actex), and all-electron Green's function Korringa-Kohn-Rostoker (mecca), and compute the pressure and internal energy of BN over a broad range of densities and temperatures. Our experiments were conducted at the ...


Photon Radiation In Hot Nuclear Matter By Means Of Chiral Anomalies, Kirill Tuchin Jan 2019

Photon Radiation In Hot Nuclear Matter By Means Of Chiral Anomalies, Kirill Tuchin

Physics and Astronomy Publications

A new mechanism of photon emission in the quark-gluon plasma is proposed. Photon dispersion relation in the presence of the CP-odd topological regions generated by the chiral anomaly acquires an imaginary mass. It allows photon radiation through the decay q→qγ and annihilation qq¯→γ processes closely related to the chiral Cherenkov radiation. Unlike previous proposals this mechanism does not require an external magnetic field. The differential photon emission rate per unit volume is computed and shown to be comparable to the rate of photon emission in conventional processes.


Beam-Energy And Centrality Dependence Of Direct-Photon Emission From Ultra-Relativistic Heavy-Ion Collisions, A. Adare, Nicole J. Apadula, Sergey Belikov, Paul Constantin, Lei Ding, Alan Dion, Nathan C. Grau, John C. Hill, Nels J. Hotvedt, Todd Kempel, John G. Lajoie, Alexandre Lebedev, S. H. Lee, Craig Ogilvie, Milap R. Patel, H. Pei, Jan Rak, Timothy T. Rinn, Marzia Rosati, Jonathan C. Runchey, Alexey Yu. Semenov, Abhisek Sen, M. Shimomura, C. L. Silva, S. Skutnik, Carla Vale, Feng Wei, Et Al., Phenix Collaboration Jan 2019

Beam-Energy And Centrality Dependence Of Direct-Photon Emission From Ultra-Relativistic Heavy-Ion Collisions, A. Adare, Nicole J. Apadula, Sergey Belikov, Paul Constantin, Lei Ding, Alan Dion, Nathan C. Grau, John C. Hill, Nels J. Hotvedt, Todd Kempel, John G. Lajoie, Alexandre Lebedev, S. H. Lee, Craig Ogilvie, Milap R. Patel, H. Pei, Jan Rak, Timothy T. Rinn, Marzia Rosati, Jonathan C. Runchey, Alexey Yu. Semenov, Abhisek Sen, M. Shimomura, C. L. Silva, S. Skutnik, Carla Vale, Feng Wei, Et Al., Phenix Collaboration

Physics and Astronomy Publications

The PHENIX collaboration presents first measurements of low-momentum (0.41\,GeV/c) direct-photon yield dNdirγ/dη is a smooth function of dNch/dη and can be well described as proportional to (dNch/dη)α with α≈1.25. This scaling behavior holds for a wide range of beam energies at the Relativistic Heavy Ion Collider and the Large Hadron Collider, for centrality selected samples, as well as for different, A+A collision systems. At a given beam energy the scaling also holds for high pT (>5\,GeV/c) but when results from different collision energies are compared, an additional sNN ...


Transition Radiation As A Probe Of The Chiral Anomaly, Xu-Guang Huang, Kirill Tuchin Nov 2018

Transition Radiation As A Probe Of The Chiral Anomaly, Xu-Guang Huang, Kirill Tuchin

Physics and Astronomy Publications

A fast charged particle crossing the boundary between chiral matter and vacuum radiates transition radiation. Its most remarkable features—the resonant behavior at a certain emission angle and the circular polarization of the spectrum—depend on the parameters of the chiral anomaly in a particular material or matter. Chiral transition radiation can be used to investigate the chiral anomaly in such diverse media as the quark-gluon plasma, Weyl semimetals, and axionic dark matter.


Finite-Size Effects In Metasurface Lasers Based On Resonant Dark States, Sotiris Droulias, Thomas Koschny, Costas M. Soukoulis Aug 2018

Finite-Size Effects In Metasurface Lasers Based On Resonant Dark States, Sotiris Droulias, Thomas Koschny, Costas M. Soukoulis

Ames Laboratory Accepted Manuscripts

The quest for subwavelength coherent light sources has recently led to the exploration of dark-mode based surface lasers, which allow for independent adjustment of the lasing state and its coherent radiation output. To understand how this unique design performs in real experiments, we need to consider systems of finite size and quantify finite-size effects not present in the infinite dark-mode surface laser model. Here we find that, depending on the size of the system, distinct and even counterintuitive behavior of the lasing state is possible, determined by a balanced competition between multiple loss channels, including dissipation, intentional out-coupling of coherent ...


A Review Of Equation-Of-State Models For Inertial Confinement Fusion Materials, J. A. Gaffney, Duane D. Johnson, Andrey Smirnov, Et Al. Aug 2018

A Review Of Equation-Of-State Models For Inertial Confinement Fusion Materials, J. A. Gaffney, Duane D. Johnson, Andrey Smirnov, Et Al.

Ames Laboratory Accepted Manuscripts

Material equation-of-state (EOS) models, generally providing the pressure and internal energy for a given density and temperature, are required to close the equations of hydrodynamics. As a result they are an essential piece of physics used to simulate inertial confinement fusion (ICF) implosions. Historically, EOS models based on different physical/chemical pictures of matter have been developed for ICF relevant materials such as the deuterium (D2) or deuterium-tritium (DT) fuel, as well as candidate ablator materials such as polystyrene (CH), glow-discharge polymer (GDP), beryllium (Be), carbon (C), and boron carbide (B4C). The accuracy of these EOS models can directly affect ...


Nanoplasmonic Phenomena At Electronic Boundaries In Graphene, Zhe Fei, Guang-Xin Ni, Bor-Yuan Jiang, Michael M. Fogler, D. N. Basov Jun 2017

Nanoplasmonic Phenomena At Electronic Boundaries In Graphene, Zhe Fei, Guang-Xin Ni, Bor-Yuan Jiang, Michael M. Fogler, D. N. Basov

Ames Laboratory Accepted Manuscripts

We review recent discoveries of the intriguing plasmonic phenomena at a variety of electronic boundaries (EBs) in graphene including a line of charges in graphene induced by a carbon nanotube gate, grain boundaries in chemical vapor deposited graphene films, an interface between graphene and moiré patterned graphene, an interface between graphene and bilayer graphene, and others. All these and other EBs cause plasmonic impedance mismatch at the two sides of the boundaries. Manifestations of this effect include plasmonic fringes that stem from plasmon reflections and interference. Quantitative analysis and modeling of these plasmonic fringes uncovered intriguing properties and underlying physics ...


Plasmonics Based Micro/Nano Manufacturing, Quincy Jay Garner Jan 2013

Plasmonics Based Micro/Nano Manufacturing, Quincy Jay Garner

Graduate Theses and Dissertations

Since the advent of the Information Age, there has been an ever growing demand to continually shrink and reduce the cost of semiconductor products. To meet this demand, a great amount of research has been done to improve our current micro/nano manufacturing processes and develop the next generation of semiconductor fabrication techniques. High throughput, low cost, smaller features, high repeatability, and the simplification of the manufacturing processes are all targets that researchers continually strive for. To this day, there are no perfect systems capable of simultaneously achieving all of these targets. For this reason, much research time is spent ...


Plasma Surface Interactions In Nanoscale Processing: Preservation Of Low-K Integrity And High-K Gate-Stack Etching With Si Selectivity, Juline Shoeb Jan 2012

Plasma Surface Interactions In Nanoscale Processing: Preservation Of Low-K Integrity And High-K Gate-Stack Etching With Si Selectivity, Juline Shoeb

Graduate Theses and Dissertations

Plasma-surface interactions are very important in the fabrication of the nm-sized features of integrated circuits. Plasma processes are employed to produce high-resolution patterns in many of the thin layers of silicon integrated circuits and to remove masking layers while maintaining high selectivity. Integrated plasma processes consisting of sequential steps such as etch, clean and surface modification, are used in semiconductor industries. The surface in contact with the process plasma is exposed to the fluxes of neutrals, ions, molecules, electrons and photons.

Modeling of surface reaction mechanisms requires the determination of the characterizations of fluxes (e.g. composition, magnitude, energy and ...


Micropiv Measurement Of Turbulent And Transitional Flow Characteristics In Microchannels , Hao Li Jan 2005

Micropiv Measurement Of Turbulent And Transitional Flow Characteristics In Microchannels , Hao Li

Retrospective Theses and Dissertations

Microscopic particle image velocimetry (microPIV) experiments were performed on smooth and roughened microchannels. These measurements represent the first instantaneous velocity field measurements in a turbulent microscale flow;The effect of hydraulic diameter on flow through smooth square polydimethylsiloxane (PDMS) microchannels was investigated by varying the hydraulic diameter from 200 mum to 640 mum for Reynolds numbers ranging from 200 through 3971. The data was analyzed to yield mean velocity profiles u, velocity fluctuations (u') and (v'), and Reynolds stresses - ( u'v') and these were compared to experimental data of macroscale channel flow. The microscale and macroscale results agreed quite well ...


Correlations To Predict Turbulent Streamwise Influence Regions And Onset Of Transition In Supersonic Flows , Manohari D. Ramesh Jan 2003

Correlations To Predict Turbulent Streamwise Influence Regions And Onset Of Transition In Supersonic Flows , Manohari D. Ramesh

Retrospective Theses and Dissertations

Correlation functions have been developed to predict both the extent of the streamwise influence regions in supersonic turbulent flows, and the onset of transition in supersonic flow past a flat plate. These correlations are empirical relations involving a priori known flow parameters. In the turbulent flow regime, correlations that can compute the extent of the upstream and downstream regions of influence in two-dimensional compression ramp and expansion corner flowfields have been developed. The correlations were obtained by analyzing numerically computed flowfields. Regression analysis using the least squares approach was applied to the computed flowfield data to determine the correlation functions ...


A Three-Dimensional Hydrodynamic Model Of Acoustic Wave Propagation Through The Non-Magnetic Solar Atmosphere , Gary Wayne Turner Jan 2003

A Three-Dimensional Hydrodynamic Model Of Acoustic Wave Propagation Through The Non-Magnetic Solar Atmosphere , Gary Wayne Turner

Retrospective Theses and Dissertations

A new three-dimensional hydrodynamics code has been developed to model the propagation of acoustically generated waves in stellar atmospheres, in particular the solar atmosphere. These waves are generated using an artificial pulsing boundary, representing the top of the convection zone. The resulting shock waves and subsequent oscillations and atmospheric heating are studied from sub-photospheric to coronal levels. The initial results from this code are presented.;The new code has been developed from a pre-existing one-dimensional Lagrangian hydrodynamic code, developed at Iowa State University over the last 25 years to successfully model the effects of acoustically generated waves propagating through the ...


A New Forward-Backward Sweeping Parabolized Navier-Stokes Algorithm With Application To Magnetohydrodynamic Flows , Hiromasa Kato Jan 2003

A New Forward-Backward Sweeping Parabolized Navier-Stokes Algorithm With Application To Magnetohydrodynamic Flows , Hiromasa Kato

Retrospective Theses and Dissertations

A new forward-backward sweeping parabolized Navier-Stokes algorithm has been developed to efficiently compute supersonic/hypersonic flowfields with embedded separated regions. The algorithm splits the streamwise flux vector using the Steger-Warming method and employs multiple forward/backward sweeps of the flowfield in order to duplicate the results that would be obtained with the complete Navier-Stokes equations. The forward/backward sweeping of the flowfield significantly reduces the number of iterations required over previous iterative parabolized Navier-Stokes algorithms. Once a separated flow region is computed, the algorithm returns to the usual forward-space-marching mode until the next separated flow region is encountered. The new ...


Hybrid Finite-Volume/Transported Pdf Method For The Simulation Of Turbulent Reactive Flows , Venkatramanan Raman Jan 2003

Hybrid Finite-Volume/Transported Pdf Method For The Simulation Of Turbulent Reactive Flows , Venkatramanan Raman

Retrospective Theses and Dissertations

A novel computational scheme is formulated for simulating turbulent reactive flows in complex geometries with detailed chemical kinetics. A Probability Density Function (PDF) based method that handles the scalar transport equation is coupled with an existing Finite Volume (FV) Reynolds-Averaged Navier-Stokes (RANS) flow solver. The PDF formulation leads to closed chemical source terms and facilitates the use of detailed chemical mechanisms without approximations. The particle-based PDF scheme is modified to handle complex geometries and grid structures. Grid-independent particle evolution schemes that scale linearly with the problem size are implemented in the Monte-Carlo PDF solver. A novel algorithm, in situ adaptive ...


Transport Processes In Directional Solidification And Their Effects On Microstructure Development , Prantik Mazumder Jan 1999

Transport Processes In Directional Solidification And Their Effects On Microstructure Development , Prantik Mazumder

Retrospective Theses and Dissertations

The processing of materials with unique electronic, mechanical, optical and thermal properties plays a crucial role in modern technology. The quality of these materials depend strongly on the microstructures and the solute/dopant fields in the solid product, that are strongly influenced by the intricate coupling of heat and mass transfer and melt flow in the growth systems. An integrated research program is developed that include precisely characterized experiments and detailed physical and numerical modeling of the complex transport and dynamical processes. Direct numerical simulation of the solidification process is carried out that takes into account the unsteady thermo-solutal convection ...


Turbulent Scalar Transport Using Two-Point Statistical Closure Theory , Robert Charles Sanderson Jan 1995

Turbulent Scalar Transport Using Two-Point Statistical Closure Theory , Robert Charles Sanderson

Retrospective Theses and Dissertations

The turbulent transport of a passive scalar (Corrsin's problem with diffusion) and of an active scalar in stably stratified fluids is studied using linear analysis (rapid distortion theory or RDT), Kraichnan's direct interaction approximation (DIA) and direct numerical simulation (DNS). The results are compared with each other and with laboratory experiments. The numerical results compare favorably with the experiments of Sirivat and Warhaft, Budwig, Tavoularis and Corrsin and Stillinger and Itsweire of van Atta's group. The RDT study reveals that much of the qualitative behavior observed in experiments, such as the tendency for the system to evolve ...


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.