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Full-Text Articles in Engineering Science and Materials

A Transient, One-Dimensional, Discrete-Element Transport Model For Predicting Hydrodynamic Conditions And Three-Layer Non-Equilibrium Pollutant Concentrations As Dissolved In Water And As Adsorbed On Different Classes Of Sediment In Controlled Rivers And Tidal Estuaries, Gary W. Zimmerman Dec 1980

A Transient, One-Dimensional, Discrete-Element Transport Model For Predicting Hydrodynamic Conditions And Three-Layer Non-Equilibrium Pollutant Concentrations As Dissolved In Water And As Adsorbed On Different Classes Of Sediment In Controlled Rivers And Tidal Estuaries, Gary W. Zimmerman

Masters Theses

A transient one-dimensional mathematical model for simulating the transport of pollutant effluents from industrial plants is presented.

The Eulerion fluid-in-discrete-element (FLIDE) formulation employs the integral forms of the conservation principles of water mass, sediment mass, and pollutant mass in variable size discrete elements that span the flow region. The transport of the pollutant effluents are modeled as dissolved and adsorbed suspended sediment in the suspended sediment and slurry sediment layer and as dissolved and stationary resident sediment in the resident sediment layer.

The contributions of vertical variations of the velocity components and pollutant concentrations in the suspended sediment and slurry ...


An Apparatus For Measuring The Thermal Conductivity Of Cast Insulation Materials, Christine A. Wilkins, Robert L. Ash Jul 1980

An Apparatus For Measuring The Thermal Conductivity Of Cast Insulation Materials, Christine A. Wilkins, Robert L. Ash

Mechanical & Aerospace Engineering Faculty Publications

A steady-state apparatus has been developed for measuring the thermal conductivity of cast materials. The design has employed a novel thermal symmetry arrangement which can permit total electrical isolation of the test material from its surroundings. © 1980 American Institute of Physics


Overview Of Ultrasonic Developments, R B. Thompson Jan 1980

Overview Of Ultrasonic Developments, R B. Thompson

Review of Progress in Quantitative Nondestructive Evaluation

An overview of the ultrasonic developments which have occurred in the DARPA/AFML Interdisciplinary Program for Quantitative NDE is presented. The paper is introduced by a discussion of the philosophy of the program and a review of the progress made during the last five years towards the development of quantitative techniques and criteria- for accepting or rejecting parts. This is followed by a sumnary of the relevant papers presented at this meeting and of the role which they play in the evolution of this new technology. The paper concludes with a discussion of the use of these technical building blocks ...


Life Prediction For Al In The Microcrack Regime Using Saw Nde, Otto Buck, W L. Morris, M R. James, R J. Richards Jan 1980

Life Prediction For Al In The Microcrack Regime Using Saw Nde, Otto Buck, W L. Morris, M R. James, R J. Richards

Review of Progress in Quantitative Nondestructive Evaluation

Harmonic generation of surface acoustic waves (SAW) is a useful tool for studying surface microcrack initiation during fatigue of high strength aluminum alloys. We have developed a model which relates the length and density of such microcracks, initiated during fatigue, with SAW harmonic generation signals. It was found that the resulting quantitative relationship between the acoustic data and the remaining fatigue life is accurate to within 5% over the last 50% of the fatigue life, spent in the microcrack initiation phase. Extensive tests are now underway to study the general applicability of these concepts to a wide range of high-strength ...


Ultrasonic Detection Of Surface Flaws In Gas Turbine Ceramics, Thomas Derkacs, I M. Matay Jan 1980

Ultrasonic Detection Of Surface Flaws In Gas Turbine Ceramics, Thomas Derkacs, I M. Matay

Review of Progress in Quantitative Nondestructive Evaluation

This paper presents the results of a program sponsored by NADC for NASC to develop an ultrasonic surface wave technique for detection of small flaws, <100 11m (< 0.004 inch), in gas turbine quality ceramics. A 45 MHz ultrasonic surface wave inspection technique is described, which employs immersion scanning ndd C-scan recording. Inspection results are presented using this technique on specimens of hot pressed Silicon nitride and silicon carbide, from two sources each, and reaction bonded silicon nitride. Results are also presented of four-point-bend tests and scanning electron micrography, which were used to identify defect sizes and types and to correlate flexural strength with inspection results. The flexural strength is shown to correlate, at least qualitatively, with the extent of ultrasonic response from machining damage. The sensitivity to individual defects is shown to be limited primarily by the extent of machining damage and the spot size of the ultrasonic beam.


Applications Of Image Reconstruction In Nde, R V. Denton, S Maitra Jan 1980

Applications Of Image Reconstruction In Nde, R V. Denton, S Maitra

Review of Progress in Quantitative Nondestructive Evaluation

The nondestructive evaluation (NDE) of materials often involves the solution of an inverse problem. It is shown that image reconstruction techniques lead to the direct solution of the 3-D inverse problem when radiographic measurements are made. In particular, it is suggested that the convolve-and-backproject solution to the 3-D divergent ray geometry problem should be useful for NDE. There is also a discussion of the accept-reject criteria appropriate for various classes of defects.


Mapping Of Materials Stress With Ultrasonic Tomography, B P. Hilderbrand, T P. Harrington Jan 1980

Mapping Of Materials Stress With Ultrasonic Tomography, B P. Hilderbrand, T P. Harrington

Review of Progress in Quantitative Nondestructive Evaluation

It is known that internal stress concentrations can give rise to microcracks which then grow when the structure is subjected to external forces. It has also been found that the velocity of sound is altered as it propagates through a region of stress. In this paper we discuss a technique called Computer Assisted Tomography (CAT) and describe an application that provides pictures of stress fields. We report the results of both simulated and experimental models used to evaluate the technique. We conclude that the CAT approach has great potential for locating and mapping residual stress in metals.


Acoustic Emission Monitoring Of In-Flight Crack Growth In Air Craft Structures, P H. Hutton, James R. Skorpik Jan 1980

Acoustic Emission Monitoring Of In-Flight Crack Growth In Air Craft Structures, P H. Hutton, James R. Skorpik

Review of Progress in Quantitative Nondestructive Evaluation

Purpose of the program is to evaluate acoustic emission (AE) for in-flight detection of fatigue crack growth in aircraft structure. A special AE system was developed and installed on a RAAF Macchi jet trainer. It has been effectively measuring AE from a fatigue crack since August, 1978. Work is continuing to investigate correlation of AE data with crack growth.


Probabilistic Models For Defect Initiated Fracture In Ceramics, A G. Evans, M E. Meyer, K W. Fertig, B I. Davis, H R. Baumgartner Jan 1980

Probabilistic Models For Defect Initiated Fracture In Ceramics, A G. Evans, M E. Meyer, K W. Fertig, B I. Davis, H R. Baumgartner

Review of Progress in Quantitative Nondestructive Evaluation

Fracture tests on hot-pressed silicon nitride containing voids and several types of inclusions have been conducted. Fracture models pertinent to each defect type have been proposed and correlated with the data. The specificity of the fracture models is emphasized, and the various trends with defect size that result from the models are described. The resultant fracture probability relations are one of the key inputs to accept/reject decisions for nondestructive failure prediction.


An Application Of Padé Approximants To Elastic Wave Scattering, J E. Gubernatis Jan 1980

An Application Of Padé Approximants To Elastic Wave Scattering, J E. Gubernatis

Review of Progress in Quantitative Nondestructive Evaluation

Several Padé methods were used to try to accelerate the convergence of partial wave sums for scattering amplitudes. A specific test problem of longitudinal-to-longitudinal scattering from a spherical void was studied in detail. Results for this test case and the behavior of partial wave amplitudes for general cases are presented and discussed.


Understanding Materials Reliability - The Mechanisms Of Fracture, Robb M. Thompson Jan 1980

Understanding Materials Reliability - The Mechanisms Of Fracture, Robb M. Thompson

Review of Progress in Quantitative Nondestructive Evaluation

For the benefit of the NDE community, a personal view will be given of the current status of our understanding of materials fracture.· The discussion will include a general description of the physical and chemical processes which occur when a solid under load possesses a crack. A physical picture is presented of the role of plasticity. The basic question of ductile vs brittle response of the solid is addressed and recent ideas and progress reviewed. Time dependence, and its manifestation in materials fatigue are briefly described. The implications for NDE are on two levels: (1) new insight generated by fundamental ...


Turbine Disk Retirement-For-Cause: Measurement Of Inspection Uncertainty For Disk Eddy Current Inspections, C A. Rau Jr, S W. Hopkins, J W. Eischen, D E. Allison Jan 1980

Turbine Disk Retirement-For-Cause: Measurement Of Inspection Uncertainty For Disk Eddy Current Inspections, C A. Rau Jr, S W. Hopkins, J W. Eischen, D E. Allison

Review of Progress in Quantitative Nondestructive Evaluation

Major cost savings are possible through life extension of high-cost jet engine components until damage develops. Retirement-for-cause (RFC) decisions will be based upon both non-destructive inspection (NDI) to detect and size defects, and engineering analysis to assess defect severity under future usage. Failure Analysis Associates is performing a three-year program for ARPA/AFML to define and verify an optimum RFC strategy for jet engine disks. In depth, quantitative characterization of NDI performance is a major part of this project. This presentation summarizes the quantitative evaluation of inspection (NDI) uncertainty for four independent inspections - two state-of-the-art eddy current inspections of disk ...


Pvf2 Transducers For Ndt, E Carome, K Fesler, H J. Shaw, D G. Weinstein, L T. Zitelli Jan 1980

Pvf2 Transducers For Ndt, E Carome, K Fesler, H J. Shaw, D G. Weinstein, L T. Zitelli

Review of Progress in Quantitative Nondestructive Evaluation

We have investigated the spatial dependence of the longitudinal piezoelectric stress constant e of PVF2. Experiments were performed on a series of no.minally identical brass-backed PVF2 longitudinal wave transducers in water using commercial PVF2 film. Computer programs were designed to predict the performance of the transducers as a function of ezz (Z) , the thickness mode piezoelectric stress constant as a function of position Z through the thickness of the film. Our experiments indicate that the coupling coefficient is uniform across the film thickness. These computer programs were also used to model the insertion loss and bandwidth performance of ...


Materials Characterization By Time Delay Spectrometry Ultrasound, P M. Gammel, M H. Leipold Jan 1980

Materials Characterization By Time Delay Spectrometry Ultrasound, P M. Gammel, M H. Leipold

Review of Progress in Quantitative Nondestructive Evaluation

A technique known as Time Delay Spectrometry (TDS), which has been used at JPL for ultrasonic tissue characterization, has promise for similar application in materials characterization as well. This technique differs from the approaches based on pulse-echo techniques which are used by other workers. Time Delay Spectrometry operates in the frequency domain directly. The transducer is excited by a rapidly swept frequency source and a tracking receiver is used to select signals arriving during a narrow time interval. In the reflection mode this time interval represents the range of the reflecting surface. In the transmission mode this time interval is ...


Overview Of Eddy Current Research At Saarbrücken, P Höller, R Becker, K Betzold Jan 1980

Overview Of Eddy Current Research At Saarbrücken, P Höller, R Becker, K Betzold

Review of Progress in Quantitative Nondestructive Evaluation

The development of an eddy current testing system is described which encloses a 4-frequency test device as well as extensive computer programs to optimize layout and adaptation to practical problems. Results obtained on the testing of welds and heat exchanger tubes are presented. The testing aim is to detect defects and to determine their type and size.


On The Resonances Of Surface Breaking Cracks, S Ayter, B A. Auld Jan 1980

On The Resonances Of Surface Breaking Cracks, S Ayter, B A. Auld

Review of Progress in Quantitative Nondestructive Evaluation

The resonance phenomenon observed in Rayleigh wave scattering from surface-breaking cracks has been investigated using Freund's results on reflection of Rayleigh waves from an infinite crack edge. To model the crack as a section of acoustic waveguide, resonances are treated as standing waves in the length and depth directions. The model takes both faces of the crack into consideration, and this makes it possible to explain the observations of all order resonances in the length direction for excitation by a Rayleigh wave beam at normal incidence. Calculations are made for rectangular and half-penny shaped cracks and differences between the ...


Defect Identification And Sizing By The Ultrasonic Satellite-Pulse Technique, G J. Gruber Jan 1980

Defect Identification And Sizing By The Ultrasonic Satellite-Pulse Technique, G J. Gruber

Review of Progress in Quantitative Nondestructive Evaluation

Type and size are the most important defect characteristics that need to be determined for reliable prediction of the remaining service lifetime of a defective structure or part. The analytical and supporting experimental results presented in this paper concern a universal ultrasonic defect-identificationand- subsequent-sizing method. The conceived satellite-pulse technique (SPT) is based on the interpretation, in terms of defect types and dimensions, of the separation in time-of-arrival between the specularly-reflected pulse and its tip-diffracted or tangentially-scattered "satellite" contained in the composite defect signal. Several alternate calibration procedures were also developed, any one of which enables the ultrasonic examiner to make ...


Characterization Of Defects And Heterogeneities In Silicon Nitride And Silicon Carbide By Different Nde Methods, K Goebbels, H Reiter Jan 1980

Characterization Of Defects And Heterogeneities In Silicon Nitride And Silicon Carbide By Different Nde Methods, K Goebbels, H Reiter

Review of Progress in Quantitative Nondestructive Evaluation

The brittleness of ceramic materials like silicon nitride and silicon carbide makes it necessary to fabricate homogeneous structures and to detect small defects in the region of 10 to 100 microns diameter. In the German program on NDE for the gas turbine therefore a study was made to compare different NDE methods and to develop new techniques. Tests were made with ultrasonics, microradiography, vibration analysis, acoustic emission and optical-holographical interferometry on test samples and real components of the gas turbine (rotor, stator, combustor). The results show that especially

  • microradiography with projection technique and X-ray focus of ≈ 10 µm diameter,
  • ultrasonics ...


Weld Inspection With Shear Horizontal Acoustic Waves Gnerated By Emats, C M. Fortunko, W E. Lawrence Jan 1980

Weld Inspection With Shear Horizontal Acoustic Waves Gnerated By Emats, C M. Fortunko, W E. Lawrence

Review of Progress in Quantitative Nondestructive Evaluation

The potential advantages of using electromagnetic acoustic transducers (EMATs) for nondestructive evaluation of metal parts have been known for some time. Recently a generically new EMAT has been perfected which can generate and receive horizontally polarized shear (SH) wave andle beams. SH waves offer considerable advantages over SV waves for inspecting metal parts of complex shape: 1) they reflect specularly from planes containing the direction of particle displacement, 2) they can be generated in any direction lying· in the saggital plane with equal efficiency, and 3) SH wave transducers inherently discriminate against Raleigh, L and SV waves. These advantages make ...


Deterministic And Probabilistic Inversion At Long Wavelengths, John M. Richardson Jan 1980

Deterministic And Probabilistic Inversion At Long Wavelengths, John M. Richardson

Review of Progress in Quantitative Nondestructive Evaluation

In contrast with the scalar wave case, the scattering of elastic waves in the long wavelength limit yields data containing a surprising amount of information concerning the nature of the scatterer. We will consider both deterministic and probabilistic versions of the inversion problem pertaining to the above scattering problem. The deterministic version provides theoretical insight into the "blindspots" of an optimal inversion procedure in the hypothetical limit of zero measurement error. The probabilistic version is appropriate for the interpretation of real data containing errors and possible inconsistencies. In the former category our-discussion will start with a review of earlier results ...


Application Of Tomography To The Nuclear Industry, R A. Morris, R P. Kruger, G W. Wecksung Jan 1980

Application Of Tomography To The Nuclear Industry, R A. Morris, R P. Kruger, G W. Wecksung

Review of Progress in Quantitative Nondestructive Evaluation

While tomographic methods of reconstructing three~dimensional x-ray images are becoming more common in the medical field, their application to industrial problems has only started. Some of the features that differentiate industrial tomography from medical tomography are

  1. x-ray energies may vary from< 10 keV to> 22 MeV
  2. radiation dose to the object is not a constraint
  3. inspection times (within economic constraints) are not as important
  4. the anomalies to be detected offer sharp, high contrast boundaries to the inspection system
  5. high spatial resolution rather than high contrast sensitivity is the primary design goal, and
  6. the number of views may be limited by other (mechanical ...


Interrogation Of Voids In Solids Utilizing Ramp Function Ultrasonic Pulses, Bill D. Cook Jan 1980

Interrogation Of Voids In Solids Utilizing Ramp Function Ultrasonic Pulses, Bill D. Cook

Review of Progress in Quantitative Nondestructive Evaluation

From some low frequency scattering investigations in radar, it is suggested that interrogating the target with "ramp" function has distinct advantages. This "ramp" function is a ramp in amplitude, not frequency. The returning echo is predicted to exhibit directly in the time domain, information of the cross-sectional area of a target as the ramp passes the target. From this information, one can infer size, volume, and orientation of the target. The theory for this interpretation is based on the physical optics approximation. This approximation is commonly used in acoustic and elastic wave scattering when the boundary conditions are approximate. The ...


Test Bed For Quantitative Nde, R C. Addison Jr, R B. Houston, J M. Martin, R Bruce Thompson Jan 1980

Test Bed For Quantitative Nde, R C. Addison Jr, R B. Houston, J M. Martin, R Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

The ARPA/AFML Interdisciplinary Program for Quantitative Flaw Definition has demonstrated a number of new techniques for quantitatively sizing flaws, as are reported elsewhere in these proceedings. This paper describes a test bed program to assemble and demonstrate these techniques in a single integrated measurement system that will extend them from the idealized geometries that have been considered thus far to geometries that are a better approximation to those that are found in real parts. Included are discussions of the conceptual design of the system, the detailed design and construction of specific modules, and preliminary experimental results. The basic system ...


Ultrasonic Caustics And The Inverse Scattering Problem In Nde, P A. Doyle Jan 1980

Ultrasonic Caustics And The Inverse Scattering Problem In Nde, P A. Doyle

Review of Progress in Quantitative Nondestructive Evaluation

This paper explores theoretically the possibility of using caustics, formed in the ultrasonic field diffracted by defects, as an approach to the inverse scattering problem, The case of crack-like defects is considered in detail, using the geometrical theory of diffraction. The involute of the far field caustic reproduces the projection of the crack edge in the incident beam direction, for a plane incident wavefront. This purely geometrical inversion is carried out uniquely for the astroid and its involute, the elliptical edge. For a general edge shape, the complete inversion requires one further length measurement, which may be carried out in ...


Scanning Laser Acoustic Microscope Visualization Of Solid Inclusions In Silicon Nitride, D E. Yuhas, T E. Mcgraw, L W. Kessler Jan 1980

Scanning Laser Acoustic Microscope Visualization Of Solid Inclusions In Silicon Nitride, D E. Yuhas, T E. Mcgraw, L W. Kessler

Review of Progress in Quantitative Nondestructive Evaluation

The Scanning Laser Acoustic Microscope (SLAM) operating at a frequency of 100 MHz is used to characterize solid inclusions in silicon nitride. Ten, seven millimeter thick discs, with 100 and 400 micron implanted inclusions are analyzed. We find that the images of a solid inclusion are characterized by a bright high transmission central zone, a well defined dark boundary and a characteristic diffraction ring pattern. These image features differentiate solid inclusions from pores and voids which may also be encountered in the samples. The images of the implanted flaws were generally found to be larger than anticipated. This can be ...


Testing The Inverse Born Procedure For Spheroidal Voids, J H. Rose, Vasundara V. Varadan, Vijay K. Varadan, Richard K. Elsley, Bernard R. Tittmann Jan 1980

Testing The Inverse Born Procedure For Spheroidal Voids, J H. Rose, Vasundara V. Varadan, Vijay K. Varadan, Richard K. Elsley, Bernard R. Tittmann

Review of Progress in Quantitative Nondestructive Evaluation

Previously we have shown that the inverse Born approximation allows an accurate determination of the radius of spherical flaws in Ti. Here we report the results of extending that analysis to spheroidal voids. Both oblate and prolate spheroids are considered. Using scattering amplitude generated by the T-matrix method, we find that both the major and minor axes of 2-1 spheroids are accurately determined. Inversion results using experimental data will be presented for the 2-1 oblate spheroid: a comparison of the experimental and theoretical results will be given.


The Use Of Acoustoelastic Measurements To Characterize The Stress States In Cracked Solids, J Hunter, R King, Gordon S. Kino, D Barnett, G Herrmann, D Ilić Jan 1980

The Use Of Acoustoelastic Measurements To Characterize The Stress States In Cracked Solids, J Hunter, R King, Gordon S. Kino, D Barnett, G Herrmann, D Ilić

Review of Progress in Quantitative Nondestructive Evaluation

The theory of acoustoelasticity predicts that a plane longitudinal acoustic wave passing through a solid which is already in a deformed state will propagate with a velocity (v) which is different from the (v0) of the same wave propagating through the undeformed medium. It may be shown that Δv/v0 = (v-v0)/v0 = B(σ12) where σ1 and σ2 are the principal stress in the plane normal to the wave propagation direction and B is the acoustoelastic constant. Wave transit time measurements allow the relative velocity change Δv/v0 to be ...


Finite Difference Methods Applied To Ultrasonic Non-Destructive Testing Problems, Leonard J. Bond Jan 1980

Finite Difference Methods Applied To Ultrasonic Non-Destructive Testing Problems, Leonard J. Bond

Review of Progress in Quantitative Nondestructive Evaluation

The scattering and reflection of ultrasonic pulses is the basis for ultrasonic non-destructive testing techniques. However problems are encountered in the interpretation of experimental results in many systems especially those which have target dimensions of the order of a wavelength, where there are no analytical solutions. It is shown that the lack of an adequate analytical theory can be overcome by the use of numerical models based on finite difference approximations of the basic elastic equations of motion. Finite difference methods, which have previously had a successful history in seismology, are introduced to study non-destructive testing problems and provide a ...


Detection Of Bending Stresses In Buried Pipelines, George A. Alers, R Bruce Thompson Jan 1980

Detection Of Bending Stresses In Buried Pipelines, George A. Alers, R Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

When gas or oil pipelines must be laid through sand or permafrost or other unstable soils, the pipe walls can he subjected to large bending loads if the soil shifts. In order to detect this condition and correct it, it would be useful to monitor the state of stress along the pipeline'at regular time intervals using a vehicle that is moved through the line by the fluid or gas in it. The experiments described here demonstrate that such a vehicle, using EMATs to excite and detect ultrasonic waves in the pipe wall, would be feasible because the transduction efficiency ...


Application Of Adaptive Learning Networks For The Characterization Of Two-Dimensional And Three-Dimensional Defects In Solids, M F. Whalen, L J. O'Brien, Anthony N. Mucciardi Jan 1980

Application Of Adaptive Learning Networks For The Characterization Of Two-Dimensional And Three-Dimensional Defects In Solids, M F. Whalen, L J. O'Brien, Anthony N. Mucciardi

Review of Progress in Quantitative Nondestructive Evaluation

The objective of the work was to develop an ultrasonic inversion procedure which (1) discriminates, (2) sizes, and (3) determines the orientation of two-dimensional (crack-like) and· three-dimensional (void-like) defects in materials. Adaptive learning networks (ALN's) were used to estimate directly the defect size and orientation parameters from the spectrum of the echo transient. A 19-element hexagonal synthetic array measured the scattered field within a 60-degree solid angle aperture. The ALN' s were trained on theoretically generated spectral data where the crack forward scattering model was based on the Geometrical Diffraction Theory and the void model was based on the ...