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Articles 1  30 of 49
FullText Articles in Mechanical Engineering
Primary Coolant Flow Characteristics As It Exits The Palisades Reactor, Gregory Alan Baustian
Primary Coolant Flow Characteristics As It Exits The Palisades Reactor, Gregory Alan Baustian
Master's Theses
During fuel cycles 9 and 10 at the Palisades Nuclear Power Plant, new phenomena have been observed using the resistance temperature devices installed in the reactor coolant piping. Oscillations in the temperature readings have been observed leading to the assumptions that there is temperature stratification of the coolant in the reactor hotlegs and that the coolant rotates as it leaves the reactor. In addition, oscillations in the bulk coolant flow within the two hot legs have been postulated. This report outlines work performed using computational fluid dynamics modelling which predict the observed and assumed flow characteristics of the Palisades reactor ...
Analysis Of Sandwich Plates Subjected To Blast Loading, Vijay Prasad Bulla
Analysis Of Sandwich Plates Subjected To Blast Loading, Vijay Prasad Bulla
Master's Theses
A dynamic analysis is presented for the bending response of square sandwich plates with isotropic core and facings under blast type pressure. The maximum central deflections of simply supported plates under static and dynamic loadings are compared for various thicknesses and elastic moduli. The deviation of the thick sandwich plate results from the purebending theory results is presented for various core properties. Small deflection dynamic isoresponse plots are shown for different core rigidities. To study the limits of small deformation linearity for various sandwich plates, nonlinear results for deformations under high pressure loads are compared with the linear results. The ...
A Vacuum FourBall Tribometer To Evaluate Liquid Lubricants For Space Applications, Masabumi Masuko, William R. Jones Jr, Ralph Jansen, Ben Ebihara, Stephen V. Pepper, Larry S. Helmick
A Vacuum FourBall Tribometer To Evaluate Liquid Lubricants For Space Applications, Masabumi Masuko, William R. Jones Jr, Ralph Jansen, Ben Ebihara, Stephen V. Pepper, Larry S. Helmick
Science and Mathematics Faculty Publications
The design and operation of a vacuum tribometer, based on the fourball configuration, is described. This tribometer evaluates the tribological characteristics of liquid lubricants for space applications. Operating conditions include: room temperature, loads to approximately 1000N, speeds to approximately 500 rpm, and pressures of approximately 10(exp 6)Pa. Tests can also be run at atmospheric pressure with air or nitrogen. Some typical test results are included.
Studies On Nonequilibrium Phenomena In Supersonic Chemically Reacting Flows, Rajnish Chandrasekhar
Studies On Nonequilibrium Phenomena In Supersonic Chemically Reacting Flows, Rajnish Chandrasekhar
Mechanical & Aerospace Engineering Theses & Dissertations
This study deals with a systematic investigation of nonequilibrium processes in supersonic combustion. The twodimensional, elliptic NavierStokes equations are used to investigate supersonic flows with nonequilibrium chemistry and thermodynamics, coupled with radiation, for hydrogenair systems. The explicit, unsplit MacCormack finitedifference scheme is used to advance the governing equations in time, until convergence is achieved.
For a basic understanding of the flow physics, premixed flows undergoing finite rate chemical reactions are investigated. Results obtained for specific conditions indicate that the radiative interactions vary substantially, depending on reactions involving HO$\sb2$ and NO species, and that this can have a noticeable influence ...
Boundary Layer Influences On The Subsonic NearWake Of A Family Of ThreeDimensional Bluff Bodies, Charles Willliam Alcorn
Boundary Layer Influences On The Subsonic NearWake Of A Family Of ThreeDimensional Bluff Bodies, Charles Willliam Alcorn
Mechanical & Aerospace Engineering Theses & Dissertations
A study is reported on subsonic bluff body nearwake flows. It has been determined that one family of bluff bodies, namely slantedbase ogive cylinders, can experience either a closed recirculating nearwake, or a longitudinal vortex nearwake depending on the base slantangle and the Reynolds number. This suggests a dependence of nearwake parameters on the state of the boundary layer ahead of separation. This report addresses the influence of the boundary layer on the nearwake of slantedbase bluff bodies. Experiments were conducted in two facilities, the 6inch Magnetic Suspension and Balance System (MSBS) at NASA Langley Research Center and the Old ...
Numerical Algorithms For SquaringUp NonSquare Systems Part Ii: General Case, Pradeep Misra
Numerical Algorithms For SquaringUp NonSquare Systems Part Ii: General Case, Pradeep Misra
Pradeep Misra
NavierStokes Simulation Of QuasiAxisymmetric And ThreeDimensional Supersonic Vortex Breakdown, Hamdy A. Kandil
NavierStokes Simulation Of QuasiAxisymmetric And ThreeDimensional Supersonic Vortex Breakdown, Hamdy A. Kandil
Mechanical & Aerospace Engineering Theses & Dissertations
Computational simulation of supersonic vortex breakdown is considered for internal and external flow applications. The interaction of a supersonic swirling flow with a shock wave in bounded and unbounded domains is studied. The problem is formulated using the unsteady, compressible, full NavierStokes equations which are solved using an implicit, fluxdifference splitting, finitevolume scheme. Solutions are obtained for quasiaxisymmetric and threedimensional flows. The quasiaxisymmetric solutions are obtained by forcing the components of the flowfield vector to be equal on two axial planes, which are in close proximity to each other. For the flow in a bounded domain, a supersonic swirling flow ...
Grid Sensitivity For Aerodynamic Optimization And Flow Analysis, Ideen Sadrehaghighi
Grid Sensitivity For Aerodynamic Optimization And Flow Analysis, Ideen Sadrehaghighi
Mechanical & Aerospace Engineering Theses & Dissertations
An algorithm is developed to obtain the grid sensitivity with respect to design parameters for aerodynamic optimization. Two distinct parameterization procedures are developed for investigating the grid sensitivity with respect to design parameters of a wingsection as an example. The first procedure is based on traditional (physical) relations defining NACA fourdigit wingsections. The second is advocating a novel (geometrical) parameterization using spline functions such as NURBS (NonUniform Rational BSplines) for defining the wingsection geometry. An interactive algebraic grid generation technique, known as TwoBoundary Grid Generation (TBGG) is employed to generate Ctype grids around wingsections. The grid sensitivity of the domain ...
Robust Control Of Nonlinear Multibody Flexible Space Structures, Atul G. Kelkar
Robust Control Of Nonlinear Multibody Flexible Space Structures, Atul G. Kelkar
Mechanical & Aerospace Engineering Theses & Dissertations
A generic nonlinear math model of a multibody flexible system is developed. Asymptotic stability of such systems using dissipative compensators is established. It is proved that, under certain conditions, this class of systems exhibit global asymptotic stability under dissipative compensation. The dissipative compensators considered are static as well as dynamic dissipative compensators. The stability proofs are based on passivity approaches, Lyapunov methods, as well as a key property of such systems, i.e., skewsymmetricity of certain matrix. The importance of the stability results obtained is that the stability is robust to parametric uncertainties and modeling errors.
For static dissipative compensators ...
Laser Ultrasonic And Photoacoustic Characterization Of Subsurface Structures, MengChou Wu, F. Raymond Parker, William P. Winfree
Laser Ultrasonic And Photoacoustic Characterization Of Subsurface Structures, MengChou 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 AeroSpace 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 ...
Custom Pvdf Transducers For PulseEcho Testing Of Solid Rocket Motors For Detection Of PropellantToBootLiner Unbonds, Lewis Brown, William M. Sisson, Christopher P. Guerin
Custom Pvdf Transducers For PulseEcho Testing Of Solid Rocket Motors For Detection Of PropellantToBootLiner Unbonds, Lewis Brown, William M. Sisson, Christopher P. Guerin
Review of Progress in Quantitative Nondestructive Evaluation
Solid rocket motor segments (SRMs) typically consist of a rigid cylindrical shell, an elastomeric insulation liner, and a core of solid propellant. A rubber bootliner is often included to relieve stresses between the propellant and insulation liner, produced near the ends of the SRM during the cure of the solid propellant. In the manufacture of the SRM, good bond integrity is required between the boot liner and propellant to prevent detrimental effects on motor performance, thus, a reliable NDE technique is required to detect possible unbond regions. One SRM manufacturer’s approach was a radiographic method consisting of analyzing overlapping ...
Ultrasonic Propagation Through A Surface With A Step Discontinuity: Validation Of A Hybrid, GaussHermite Ray Tracing Beam Model, M. Greenwood, J.L. Mai, A. Minachi, I. YaldaMooshabad, R. Bruce Thompson
Ultrasonic Propagation Through A Surface With A Step Discontinuity: Validation Of A Hybrid, GaussHermite Ray Tracing Beam Model, M. Greenwood, J.L. Mai, A. Minachi, I. YaldaMooshabad, R. Bruce Thompson
Review of Progress in Quantitative Nondestructive Evaluation
This research continues our cooperative effort to study the effects of largescale surface roughness on ultrasonic transmission through interfaces and updates our previouslyreported 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 ...
Ultrasonic Scattering From Spherically Orthotropic Shells, John Mittleman, Ron Roberts, R. Bruce Thompson
Ultrasonic Scattering From Spherically Orthotropic Shells, John Mittleman, Ron Roberts, R. Bruce Thompson
Review of Progress in Quantitative Nondestructive Evaluation
Concerns over the detectability of embrittlement in high strength alloys has led to studying a simple anisotropic shell model [1] for grain boundaries decorated by precipitates, or otherwise enriched by segregated inhomogenieties. In this model the shell is presumed to be “spherically orthotropic,” having five independent elastic constants and symmetry about the origin of a spherical coordinate system. This structure is analogous to transversely isotropic materials in a Cartesian coordinate system. By studying ultrasonic scattering from such shells (embedded in an isotropic host, and surrounding an isotropic core), we hope to learn whether their presence could be detected, and differentiated ...
Ultrasonic Scattering From A Crack Which Emanates From A Rivet Hole, David Budreck
Ultrasonic Scattering From A Crack Which Emanates From A Rivet Hole, David Budreck
Review of Progress in Quantitative Nondestructive Evaluation
In this article we present the exact solution, to first order of the interacting field, of the following canonical problem. We consider the scattering system consisting of an isotropic elastic medium containing an infinite cylindrical void (= hole), from which emanates a halfpennyshaped crack. The crack lies in a plane containing the axis of the cylindrical void, also the crack intersects the void at its own axis of symmetry. In the paragraph below we define what is meant by obtaining the solution ‘to first order’.
Scattering By An Infinite Array Of Randomly Spaced Coplanar Cracks, Yozo Mikata
Scattering By An Infinite Array Of Randomly Spaced Coplanar Cracks, Yozo Mikata
Review of Progress in Quantitative Nondestructive Evaluation
In this paper, the investigation is carried out for the scattering of an antiplane shear (SH) wave by an infinite array of randomly spaced coplanar cracks. This study was motivated by the desire to better understand the detection and characterization of a flaw plane, i.e., a plane of microcracks, in a more realistic situation. The first thing we can do to model a flaw plane is to model it as a periodic array of cracks [1–5]. In reality, however, an array of cracks is never periodic but rather random. Thus in a previous paper [6], we have treated ...
Improved Finite Difference Method For Long Distance Propagation Of Waves, Doron Kishoni, Shlomo Ta'asan
Improved Finite Difference Method For Long Distance Propagation Of Waves, Doron Kishoni, Shlomo Ta'asan
Review of Progress in Quantitative Nondestructive Evaluation
Evaluation of aging aircraft involves inspection of large areas of plates, including lap joints, bonded material and other complex geometries. These inspections need to be done within a reasonable time in order to be economical. Ultrasonic measurements of platemodes propagating for large distances [1] are a promising method for fast detection of these defects in a commercial environment. There is a need to predict the waveforms of such waves in order to analyze the results of the experimental data. Analytic solution cannot always be found for general cases, therefore, numerical prediction of elastic wave propagation for long distances is desired ...
Phase Velocity And Attenuation Of Sh Waves In A FiberReinforced Composite, RueyBin Yang, Ajit K. Mal
Phase Velocity And Attenuation Of Sh Waves In A FiberReinforced Composite, RueyBin Yang, Ajit K. Mal
Review of Progress in Quantitative Nondestructive Evaluation
We consider SH wave propagation in a fiberreinforced composite which consists of a homogeneous, isotropic matrix, containing long, parallel, randomly distributed circular fibers of identical properties. The scattering of waves in the elastically inhomogeneous medium results in a frequency dependent velocity and attenuation of the coherent wave.
Ultrasonic Oblique Incidence In Anisotropic Media, Xiang Zhao, Davis M. Egle
Ultrasonic Oblique Incidence In Anisotropic Media, Xiang Zhao, Davis M. Egle
Review of Progress in Quantitative Nondestructive Evaluation
Determining the elastic moduli of anisotropic materials via nondestructive testing techniques is one of the most difficult subjects of acoustoelasticity theory today. The major difficulty comes from the fact that the elastic waves propagating in anisotropic media have different phase and group velocities in both magnitude and direction, which was considered to greatly complicate the analysis of the problem. Therefore, previous work in this area has been restricted to either measurements conducted only in symmetry planes, as mentioned in [1,2], or the slight anisotropy case in which the ultrasonic measurement was approximately related to the phase velocity, such as ...
Guided Waves In Piezoelectric Plates, HualTe Chien, Adnan H. Nayfeh, CheHua Yang, Dale E. Chimenti
Guided Waves In Piezoelectric Plates, HualTe Chien, Adnan H. Nayfeh, CheHua Yang, Dale E. Chimenti
Review of Progress in Quantitative Nondestructive Evaluation
In recent paper [1] Nayfeh and Chimenti presented the analysis of the propagation of free waves in a general anisotropic plate. Closed form secular equations which isolate the mathematical conditions for symmetric and antisymmetric wave mode propagation in completely separate terms were obtained. By paralleling the procedure of Nayfeh and Chimenti [1], Nayfeh and Chien [2] presented exact solutions for the interaction of elastic waves with fluidloaded piezoelectric plates. The technique used was shown to formally handle the most general anisotropy (i.e. the triclinic) case. The plate was immersed in liquid and incident waves impinged upon it from the ...
Interaction Of Ultrasound With Imperfectly Contacting Interfaces, R. Bruce Thompson
Interaction Of Ultrasound With Imperfectly Contacting Interfaces, R. Bruce Thompson
Review of Progress in Quantitative Nondestructive Evaluation
The need to characterize imperfectly contacting interfaces is encountered in a wide variety of scientific and engineering problems, as illustrated in Fig. 1. Parts (a)–(c) illustrate the stages of diffusion bonding, [1,2] in which the condition of the interface evolves from one of isolated contacts at the initial stages of bonding through one containing distributed micropores, which exist during intermediate stages, to a state in which the material is fully bonded but in which there may be some nearinterface microstructural variations. The ability to determine the degree to which bonding has passed through these conditions is presently needed ...
Quantitative Thickness Measurements Of Ice Layers With Remote Ir Detection, D. Heath, William P. Winfree
Quantitative Thickness Measurements Of Ice Layers With Remote Ir Detection, D. Heath, William P. Winfree
Review of Progress in Quantitative Nondestructive Evaluation
Accretion of ice on aerospace structures is a problem affecting takeoff safety and aerodynamic performance. The problem is of concern for commercial and military aircraft, on the runway and in flight, when adverse weather conditions allow ice formation to occur. Ice accretion also occurs on aerospace structures when cryogenic fuels are used, if defects in insulators allow cold spots to develop. In particular, ice formation on the space shuttle external tank can result in structural damage during launching if ice of appreciable mass detaches and impacts the orbiter surface.
Structure Characterization With Thermal Wave Imaging, Kurt Bryan
Structure Characterization With Thermal Wave Imaging, Kurt Bryan
Review of Progress in Quantitative Nondestructive Evaluation
Thermal imaging is a technique of recent interest for the nondestructive evaluation of materials. This method attempts to characterize the internal structure of a sample (perhaps to locate flawscracks, bubbles, corrosion, etc.) by using its surface temperature response to an external heating. Some recent work on this subject is detailed in [2], [3], [4] and [6].
DualBand Infrared Imaging Applications: Locating Buried Minefields, Mapping Sea Ice And Inspecting Aging Aircraft, Nancy Del Grande, Philip F. Durbin, Dwight E. Perkins
DualBand Infrared Imaging Applications: Locating Buried Minefields, Mapping Sea Ice And Inspecting Aging Aircraft, Nancy Del Grande, Philip F. Durbin, Dwight E. Perkins
Review of Progress in Quantitative Nondestructive Evaluation
We discuss the use of dualband infrared (DBIR) imaging for three quantitative NDE applications: locating buried surrogate mines, mapping sea ice thicknesses and inspecting subsurface flaws in aging aircraft parts. Our system of DBIR imaging offers a unique combination of thermal resolution, detectability, and interpretability. Pioneered at Lawrence Livermore Laboratory, it resolves 0.2 °C differences in surface temperatures needed to identify buried mine sites and distinguish them from surface features. It produces both surface temperature and emissivityratio images of sea ice, needed to accurately map ice thicknesses (e.g., by first removing clutter due to snow and surface roughness ...
Thermal Method For Depth Of Damage Determination In Insulating Materials, P. Howell, K. Elliott Cramer, William P. Winfree
Thermal Method For Depth Of Damage Determination In Insulating Materials, P. Howell, K. Elliott Cramer, William P. Winfree
Review of Progress in Quantitative Nondestructive Evaluation
Impact damage often may produce little visible surface damage, yet extensive subsurface delaminations, greatly reducing the load carrying capacity of the composite part [1]. For large composite structures typical of aerospace applications, thermal NDE techniques have been shown to provide quantitative information regarding the area and depth of hidden damage in composite samples [2] [3]. For a quantitative assessment of damage, where a noncontacting method capable of imaging large areas at a time is required, thermal techniques have some advantages.
Laser Ultrasonics For Coating Thickness Evaluation At 1200°C, H. Ringermacher, F. A. Reed, J. R. Strife
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 inprocess 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.
Crack Detection In Fuselage Panels By A NarrowBand LaserBased Ultrasonic System, Jin Huang, Sridhar Krishnaswamy, Jan D. Achenbach
Crack Detection In Fuselage Panels By A NarrowBand LaserBased 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 nearsurface region of a solid for cracks and other flaws by probing for the presence of scattering sources. In the nondestructive characterization of solids, laser generation of ultrasound as well as interferometric detection of the surface waves are particularly attractive in view of the noncontacting 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 dualprobe 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, JeanPierre Monchalin, R. Heon, P. Bouchard, C. Padioleau, D. A. Froom, W. Frazier, J. Barton
Laser Ultrasonic Inspection Of Honeycomb Aircraft Structures, F. P. Chang, T. E. Drake, M. A. Osterkamp, JeanPierre 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 pulsedecho and throughtransmission modes of ultrasonic inspection. Debonds in adhesively bonded structures are most effectively detected by the throughtransmission mode of ultrasonic inspection.
Novel ThermalAcoustic Point Transducer, Curtis Fiedler, Pramode Bhagat, John C. Murphy
Novel ThermalAcoustic Point Transducer, Curtis Fiedler, Pramode Bhagat, John C. Murphy
Review of Progress in Quantitative Nondestructive Evaluation
The Air Force has a continuing need to develop materials which can withstand high temperatures and stresses. The quality of the grain boundaries, i.e. the ability of the grain boundary to resist slip, is one of the most important factors in determining how well a material will resist creep and high stresses. While there are techniques which can image grain boundaries (ultrasonic microscopy and scanning electron microscopy of etched specimens), there is no known method to assess their quality. Thus there is a need to develop a technique to measure the quality of grain boundaries.
HighFrequency Elastodynamic Boundary Integral Equation Inversion Using Asymptotic Phase Information, R. Roberts
HighFrequency Elastodynamic Boundary Integral Equation Inversion Using Asymptotic Phase Information, R. Roberts
Review of Progress in Quantitative Nondestructive Evaluation
Ultrasonic transmission and scattering in the high frequency regime are important problems in ultrasonic NDE, relating to both scattering from large flaws, and the transmission behavior of an ultrasonic beam in a complex geometry component. Ultrasonic modeling efforts are often confronted with problems for which asymptotic methods such as geometrical diffraction theory (GTD) prove inadequate due to insufficiently high frequency or lack of an appropriate canonical solution, but which are too high in frequency (too large in ka) for conventional numerical methods such as boundary element methods (BEM). The inefficiency of BEM at high frequency arises from the need to ...
Application Of A SelfCalibrating Ultrasonic Technique To The Detection Of Fatigue Cracks By The Use Of Lamb Waves, I. N. Komsky, Jan D. Achenbach
Application Of A SelfCalibrating Ultrasonic Technique To The Detection Of Fatigue Cracks By The Use Of Lamb Waves, I. N. Komsky, Jan D. Achenbach
Review of Progress in Quantitative Nondestructive Evaluation
The reliability of fatiguecrack detection plays an important role in the safety of aircraft structures. Improvements in this reliability can be achieved by making the inspection technique independent of the coupling of the sensor to the specimen. A selfcalibrating technique previously developed by the authors [1] makes it possible to detect and quantitatively characterize defects in aircraft structures with greater reliability.