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Full-Text Articles in Mechanical Engineering

Brittle Composites Modeling: Compazisons With Mosi2/Zro2, S.P. Chen, Richard Alan Lesar, A. D. Rollett Nov 1993

Brittle Composites Modeling: Compazisons With Mosi2/Zro2, S.P. Chen, Richard Alan Lesar, A. D. Rollett

Richard Alan Lesar

We have calculated the mechanical properties of brittle composites with spring-network (SN) model. The composites that we studied involve the transformation toughening effects and the accompanying micro-cracking. Our simulation results are consistent with experiments of MoSi2 toughened with ZrO2. By monitoring the stress changes due to the transformation and micro-cracking we are able to separate, for the first time, the contributions from these two competing effects. We also found that the fracture toughness of the composite increases as the modulus, interfacial cohesion of particle increases.


Fiber Enhanced Viscoelastic Damping Polymers And Their Application To Passive Vibration Control, Houchun Xia Jul 1993

Fiber Enhanced Viscoelastic Damping Polymers And Their Application To Passive Vibration Control, Houchun Xia

Mechanical & Aerospace Engineering Theses & Dissertations

A new composite damping material is investigated, which consists of a viscoelastic matrix and high elastic modulus fiber inclusions. This fiber enhanced viscoelastic damping polymer is intended to be applied to light-weight flexible structures as surface treatment for passive vibration control. A desirable packing geometry for the composite material is proposed, which is expected to produce maximum shear strain in the viscoelastic damping matrix. Subsequently, a micromechanical model is established in which the effect of fiber segment length and relative motion between neighboring fibers are taken into account. Based on this model, closed form expressions for the effective storage and ...


Silicon Carbide/Electroless Nickel Composite Plating For Aluminum Substrates, Ben Charbit Apr 1993

Silicon Carbide/Electroless Nickel Composite Plating For Aluminum Substrates, Ben Charbit

Master's Theses

The effectiveness of producing a composite coating by suspending micron-sized particles in an electroless nickel bath while plating a 2024T4 aluminum alloy part was studied. The variation in the count of particles trapped in the nickel coating due to changes in the particle size, concentration of the particles in the bath, and the substrate surface texture was also studied. Particle sizes of 1 micron and 10 microns, concentrations of 15 gr/lt and 30 gr/lt, and polished and blasted textures were used. It was found that this technique is an effective way to produce composite coatings rendering a high ...


Performance Characteristics Of Piezocomposite Bulk Wave Transducers, J. Hossack, B. A. Auld Jan 1993

Performance Characteristics Of Piezocomposite Bulk Wave Transducers, J. Hossack, B. A. Auld

Review of Progress in Quantitative Nondestructive Evaluation

Piezoelectric ceramic/ polymer composite materials, possessing useful characteristics unobtainable in single phase materials, have been widely investigated over the past ten years. [1]. Their superior matching to low impedance media has been recognized by manufacturers of medical ultrasound and sonar equipment. However, so far as we know, they have received little attention in the field of non-destructive examination. It is evident that they offer superior performance for the inspection of low impedance media; including concrete, wood, fiber reinforced resin composites etc. A review of the types of composite available is presented together with results indicating achievable performance.


Real-Time Ultrasonic Investigation Of Fiber-Matrix Debonding In Ceramic-Matrix Composite, Shi-Chang Wooh, Isaac M. Daniel Jan 1993

Real-Time Ultrasonic Investigation Of Fiber-Matrix Debonding In Ceramic-Matrix Composite, Shi-Chang Wooh, Isaac M. Daniel

Review of Progress in Quantitative Nondestructive Evaluation

Limitations of ceramic materials such as brittleness, low tensile strength and low fracture toughness are being overcome with the introduction of ceramic matrix composites. The mechanical behavior of these fiber-reinforced composites strongly depends on the fiber-matrix bonding condition. If the bonding is too weak, there is poor stress transfer. On the other hand, for a case of very strong bond, the material behaves in a brittle fashion. Recently, photomicroscopic observations were made and the macroscopic behavior of the material was related to the failure mechanisms and damage development under loading [1]. However, this method is destructive, limited to damage on ...


Propagation Of Laser Generated Broadband Ultrasonic Pulses In A Thick Carbon Fibre Composite Plate, L. P. Scudder, D. A. Hutchins, N. Guo Jan 1993

Propagation Of Laser Generated Broadband Ultrasonic Pulses In A Thick Carbon Fibre Composite Plate, L. P. Scudder, D. A. Hutchins, N. Guo

Review of Progress in Quantitative Nondestructive Evaluation

The use of laser generated ultrasound for the pulse-echo testing of carbon fibre reinforced polymer (CFRP) aerospace components is being established [1,2]. Our particular interest is in the possibility of using ultrasound propagating from the laser source along the component, as bulk or plate waves, as a means of testing a larger area for a single step in a scan. As part of an investigation into how laser generated pulses propagate in CFRP we have examined their propagation in a 40 ply, 5.5mm thick (300x300mm area) unidirectional plate. The plate was made from carbon fibre reinforced epoxy resin ...


Laser Ultrasonic Inspection Of Graphite Epoxy Laminates, Christian Padioleau, Paul Bouchard, René Héon, Jean-Pierre Monchalin, Francis F. Chang, Tomy E. Drake, Kenneth I. Mcrae Jan 1993

Laser Ultrasonic Inspection Of Graphite Epoxy Laminates, Christian Padioleau, Paul Bouchard, René Héon, Jean-Pierre Monchalin, Francis F. Chang, Tomy E. Drake, Kenneth I. Mcrae

Review of Progress in Quantitative Nondestructive Evaluation

Superior mechanical properties and reduced weight of fiber reinforced polymer matrix composite laminates (e.g., made of graphite epoxy) are leading to their increased use in aeronautic and aerospace structures. These materials are found more and more in load bearing components, which in turn, requires their integrity to be fully evaluated by nondestructive inspection. This applies to newly manufactured parts which can be flawed following improper manufacturing procedures and to parts which have been in service on an aircraft as well, since additional flaws could have occurred and old existing flaws could have grown and become more severe. Flaws which ...


Investigation Of Corrosion In Aluminum/Adhesive Lap-Splices Using Pulse-Echo Ultrasonic Techniques, T. C. Patton, D. K. Hsu Jan 1993

Investigation Of Corrosion In Aluminum/Adhesive Lap-Splices Using Pulse-Echo Ultrasonic Techniques, T. C. Patton, D. K. Hsu

Review of Progress in Quantitative Nondestructive Evaluation

Corrosion can exist in any layer of a simple aluminum/adhesive lap-splice. For lap- splices where only one aluminum surface is accessible, first layer corrosion is corrosion that occurs on or under the accessible skin; and second layer corrosion is that which exists behind the adhesive/scrim layer on the upper or lower surface of the inaccessible skin. Many different nondestructive evaluation (NDE) techniques can detect first layer corrosion, and much progress has been made quantifying corrosion that exists in this layer[l]. Due to the layered nature of a lap-splice, second layer corrosion is much more difficult to detect ...


Ultrasonic Assessment Of Microcrack Damage In Ceramics, Y. C. Chu, M. Hefetz, S. I. Rokhlin Jan 1993

Ultrasonic Assessment Of Microcrack Damage In Ceramics, Y. C. Chu, M. Hefetz, S. I. Rokhlin

Review of Progress in Quantitative Nondestructive Evaluation

The inherent brittleness of ceramics often results in catastrophic failure due to microcrack damage caused by thermal treatment or mechanical loading. Extensive theoretical and experimental studies have been performed to analyze microcrack damage in ceramics caused by thermal shock [1–7]. Hasselman [1,2] proposed a simple model describing the strength behavior of ceramic materials as a function of thermal shock temperature difference ΔT. The important characteristic parameter in this model is the critical temperature difference, ΔT c . For thermal shock temperature differences less than ΔT c (stage I, Fig. 1) ceramics retain their strength. Thermal shocks with temperature differences ...


Effects Of Acoustic Scattering At Rough Surfaces On The Sensitivity Of Ultrasonic Inspection, Peter B. Nagy, Laszlo Adler, James H. Rose Jan 1993

Effects Of Acoustic Scattering At Rough Surfaces On The Sensitivity Of Ultrasonic Inspection, Peter B. Nagy, Laszlo Adler, James H. Rose

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic inspection of ordinary samples with more or less rough surfaces is an everyday problem in industrial NDE. Contact techniques require flat or other regular (e. g., cylindrical) surfaces of negligible roughness with respect to the acoustic wavelength. Immersion techniques are less susceptible to surface topography, but they still require that the surface radius be larger than the beam diameter and the surface roughness be comparable or less than the wavelength in the immersion fluid. This difference is due to the fact that in immersion inspection surface irregularities do not significantly reduce the energy transmission into the specimen but rather ...


Acoustic Microscopy Measurements To Correlate Surface Wave Velocity And Surface Roughness, Y. C. Lee, Jan D. Achenbach, Jin O. Kim Jan 1993

Acoustic Microscopy Measurements To Correlate Surface Wave Velocity And Surface Roughness, Y. C. Lee, Jan D. Achenbach, Jin O. Kim

Review of Progress in Quantitative Nondestructive Evaluation

Acoustic microscopy can be used for very localized measurements of the velocity and attenuation of surface waves, and hence is a possible technique for nondestructive evaluation of near surface damage due to fatigue, machining, friction, wear, etc. Because the frequency of operation of an acoustic microscope is high, usually above 100 MHz, the wavelength of the surface wave is relatively small, and thus the roughness of the specimen may affect the wave velocity. In most cases the specimens must be polished to a metallurgical level to ensure that the true Rayleigh wave velocity, i.e., the one for a smooth ...


Line-Focus Acoustic Mcroscopy Measurements Of Thin-Film Elastic Constants, Jin O. Kim, Jan D. Achenbach Jan 1993

Line-Focus Acoustic Mcroscopy Measurements Of Thin-Film Elastic Constants, Jin O. Kim, Jan D. Achenbach

Review of Progress in Quantitative Nondestructive Evaluation

Thin film materials are widely used as hard, protective coatings for softer surfaces. It is known that fracture strength and hardness are related to the elastic and plastic properties [1]. The elastic constants of the film deposited on a substrate are, however, difficult to measure. By a technique which was recently discussed [2] the elastic constants of amorphous (isotropic) films and single-crystal (anisotropic) films can be obtained by measuring the velocities of surface acoustic waves (SAWs) propagating over a thin-film/ substrate specimen by the use of a line-focus acoustic microscope.


A Reflection Ultrasonic Interference Method For Measurement Of The Acoustic Velocity Of Thin Layers, D. K. Mak, G. Langlois Jan 1993

A Reflection Ultrasonic Interference Method For Measurement Of The Acoustic Velocity Of Thin Layers, D. K. Mak, G. Langlois

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic waves can be used to measure the velocities and other properties of a material layer by determining the difference in the time-of-flight of the successive echoes from the backwall of the layer. The top and bottom surfaces must be sufficiently far apart for the successive echoes to be distinct. This method can be used to measure the velocity of a protective epoxy layer on a pipeline wall to determine the deviation of an ultrasonic wave scattered from a defect. It has been used to determine the strength of adhesive bonds [1].


Ultrasonic Attenuation Of Water-Infiltrated Thermal Barrier Coatings, Joachim Bamberg, Heinz Schmitt Jan 1993

Ultrasonic Attenuation Of Water-Infiltrated Thermal Barrier Coatings, Joachim Bamberg, Heinz Schmitt

Review of Progress in Quantitative Nondestructive Evaluation

For advanced aircraft gas-turbine engines greater efficiencies and higher thrust are demanded. One possibility to achieve this is to increase the gas temperature at the turbine-section. Then thermal barrier coatings are necessary to protect the metallic structures.


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

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

Review of Progress in Quantitative Nondestructive Evaluation

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


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

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

Review of Progress in Quantitative Nondestructive Evaluation

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


Inspection Of Refinery Vessels For Hydrogen Attack Using Ultrasonic Techniques, W. D. Wang Jan 1993

Inspection Of Refinery Vessels For Hydrogen Attack Using Ultrasonic Techniques, W. D. Wang

Review of Progress in Quantitative Nondestructive Evaluation

Hydrogen attack is a damage mechanism occurring in steels exposed to high pressure hydrogen at elevated temperatures. Under such conditions, hydrogen atoms diffuse into steels and react with carbides. The reaction leads to formation of methane and, subsequently, intergranular fissuring and losses of material strength and toughness.


The Detection Of A Brittle Layer At The Bondline In Diffusion Bonded Titanium, Michael Lowe, Peter Cawley Jan 1993

The Detection Of A Brittle Layer At The Bondline In Diffusion Bonded Titanium, Michael Lowe, Peter Cawley

Review of Progress in Quantitative Nondestructive Evaluation

Diffusion bonding, the joining of two surfaces by the interdiffusion of atoms across the interface, is brought about by the application of pressure for a specified time at high temperature. This form of bonding has the attractions for aerospace applications of very high strength and low maintenance costs.


Ultrasonic Shearwave Measurements Of Phase Transitions In Zircalloy At Elevated Temperatures, D. R. Billson, D. A. Hutchins Jan 1993

Ultrasonic Shearwave Measurements Of Phase Transitions In Zircalloy At Elevated Temperatures, D. R. Billson, D. A. Hutchins

Review of Progress in Quantitative Nondestructive Evaluation

CANDU reactors each contain several hundred zirconium-niobium pressure tubes. The zirconium-niobium alloy is prone to hydrogen (and deuterium) absorption, which can lead to the formation of brittle zirconium hydride platelets within the metal. These hydrides have caused a number of pressure tube leaks, and were the cause of a major failure in one early reactor. They have necessitated the retubing (or the scheduled retubing) of the earliest reactors at a cost of several hundred million dollars each.


Eddy Current Evaluation Of Porous Magnesium Alloy Casting, Gabor Blaho, Alain Quirion, Laszlo Adler Jan 1993

Eddy Current Evaluation Of Porous Magnesium Alloy Casting, Gabor Blaho, Alain Quirion, Laszlo Adler

Review of Progress in Quantitative Nondestructive Evaluation

Metal matrix composites (MMCs) have increasingly found a home in high technology industries. Even though much research and money have been invested in their conception, manufacturing and incorporation into load bearing structures, the development of suitable nondestructive evaluation technique to test their integrity has lagged behind. Eddy current testing may provide a suitable method of inspection the internal structure of MMCs through differences in electrical conductivity and/or magnetic permeability between fibers and matrix.


Ultrasonic Sensing Simulation Of Cdte Single Crystal Growth, Yichi Lu, Haydn N. G. Wadley Jan 1993

Ultrasonic Sensing Simulation Of Cdte Single Crystal Growth, Yichi Lu, Haydn N. G. Wadley

Review of Progress in Quantitative Nondestructive Evaluation

Today’s infrared detector arrays consist of Hg1-xCdxTe deposited upon lattice matched Cd1-xZnxTe substrate wafers. Very high quality Cd1-xZnxTe crystals must be grown so that substrate wafer defects do not degrade the detector’s performance. Usually, the Cd1-xZnxTe crystals are grown by a Bridgman technique in which a charge is melted in a cylindrical quartz ampoule and slowly withdrawn from the hot zone (at ~ 1100°C) of a furnace.1 The best quality crystal is obtained from material solidified under plane front conditions.2 This is difficult to achieve, and a need has arisen for insitu sensing of the growth ...


Monte-Carlo Simulation Of Ultrasonic Grain Noise, I. Yalda-Mooshabad, Frank J. Margetan, R. Bruce Thompson Jan 1993

Monte-Carlo Simulation Of Ultrasonic Grain Noise, I. Yalda-Mooshabad, Frank J. Margetan, R. Bruce Thompson

Review of Progress in Quantitative Nondestructive Evaluation

In ultrasonic inspections for small or subtle defects in metals, defect signals may be obscured by grain noise echoes which arise from the scattering of sound by the microstructure of the metal. Models for predicting microstructural noise levels are consequently essential for accurately assessing the reliability of the ultrasonic inspections. Existing noise models, like the independent scatterer model (ISM) [1], are capable of predicting only average noise characteristics, such as the root-mean-square (rms) noise level. Average noise levels, although useful, are not sufficient for assessing detection reliability. One needs to know the manner in which noise signals are distributed about ...


Modeling Ultrasonic Microstructural Noise In Titanium Alloys, Frank J. Margetan, R. Bruce Thompson, I. Yalda-Mooshabad Jan 1993

Modeling Ultrasonic Microstructural Noise In Titanium Alloys, Frank J. Margetan, R. Bruce Thompson, I. Yalda-Mooshabad

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic echoes from small or subtle defects in metals may be masked by competing “noise” echoes which arise from the scattering of sound by grains or other microstructural elements. Algorithms for estimating the detectability of such defects consequently require quantitative models for microstructural noise. In previous work [1,2] we introduced an approximate noise model for normal-incidence immersion inspections using tone-burst pulses, and we used the model to estimate signal/noise ratios for brittle (hard-alpha) inclusions in titanium alloys. In the present work we consider an extension of that noise model to inspections using broadband incident pulses. Like its predecessor ...


Relationships Between Ultrasonic Noise And Macrostructure Of Titanium Alloys, K. Y. Han, R. Bruce Thompson, Frank J. Margetan, James H. Rose Jan 1993

Relationships Between Ultrasonic Noise And Macrostructure Of Titanium Alloys, K. Y. Han, R. Bruce Thompson, Frank J. Margetan, James H. Rose

Review of Progress in Quantitative Nondestructive Evaluation

The complex microstructure of two-phase titanium alloys can produce considerable ultrasonic backscattering noise. The noise introduces problems in detecting small flaws, such as hard-alpha inclusions, by forming a background which can mask the flaw signals. Therefore better understanding of grain noise is required to quantify and increase the detectability of the small flaws. As an aid to understanding the grain noise, an independent scattering model was constructed and studied during last two years by Margetan and Thompson. In that model for the backscattered noise generated by a tone burst, the grain noise is described by following equation (1) N(t ...


Ultrasonic Nde Of Adhesive Metal To Metal Bond Integrity Based On A Combined Numerical And Expert System Approach, Reinhold Ludwig, John M. Sullivan Jr., Dacheng Dai Jan 1993

Ultrasonic Nde Of Adhesive Metal To Metal Bond Integrity Based On A Combined Numerical And Expert System Approach, Reinhold Ludwig, John M. Sullivan Jr., Dacheng Dai

Review of Progress in Quantitative Nondestructive Evaluation

Bonded structures have become increasingly prevalent in the safe and reliable operation of many advanced material components. Concomitant with the wide-spread use of adhesively bonded materials comes the need of nondestructive inspection of the bond line. Since conventional NDE methods offer only partial success in detecting the various possible bondline conditions [1], additional research in the actual energy/bondline interaction is required.


Experimental Study Of Thermal Oxidation Damage In Ceramic Composites Using Ultrasonic Waves, Y.-C. Chu, S. I. Rokhlin, G. Y. Baaklini, Ramakrishna Bhatt Jan 1993

Experimental Study Of Thermal Oxidation Damage In Ceramic Composites Using Ultrasonic Waves, Y.-C. Chu, S. I. Rokhlin, G. Y. Baaklini, Ramakrishna Bhatt

Review of Progress in Quantitative Nondestructive Evaluation

One major concern about ceramic matrix composites (CMC) is their high temperature stability, especially in an oxidizing environment. In general CMC materials are composed of matrix, fiber, and interphase layers (mainly fiber coatings and/or reaction product layers). It is known [1,2] that the properties of CMC materials are dominated by the interphase. However, this interphase often suffers from oxidation reactions caused by diffusion of oxygen through the matrix [1,3]. As a result desirable properties are not retained.


Ultrasonic Characterization Of Fiber-Matrix Interphasial Properties In Ceramic Matrix Composites, Y.-C. Chu, S. I. Rokhlin Jan 1993

Ultrasonic Characterization Of Fiber-Matrix Interphasial Properties In Ceramic Matrix Composites, Y.-C. Chu, S. I. Rokhlin

Review of Progress in Quantitative Nondestructive Evaluation

The major role of the fiber-matrix interphase in ceramic matrix composites (CMC) is to increase the composite fracture resistance; thus the properties of these materials are dominated by the interphase. To achieve this, the interphase is designed to provide friction sliding contact between fiber and matrix, which prevents fracture of fibers due to matrix cracking [1,2]. Due to the relatively low stiffness of the fiber-matrix interphase compared to fiber and matrix, the interphase also has a dominant effect on the transverse and shear stiffnesses of CMC materials [3]. Therefore, to obtain optimal performance in CMC materials quantitative characterization of ...


On The Differentiation Of Diffusion Bond Strength Using The Total Acoustic Energy Reflected From The Bond, G. C. Ojard, Otto Buck, D. K. Rehbein, M. S. Hughes Jan 1993

On The Differentiation Of Diffusion Bond Strength Using The Total Acoustic Energy Reflected From The Bond, G. C. Ojard, Otto Buck, D. K. Rehbein, M. S. Hughes

Review of Progress in Quantitative Nondestructive Evaluation

Diffusion bonding is a well known metallurgical joining technique which allows similar and dissimilar materials to be bonded together in near net shape. Due to this feature, wider use of this technique is now being made, especially in aerospace industries. Therefore, the differentiation of diffusion bonds with little variation in their acoustic response is of critical importance since relatively significant changes in bond strength may be a consequence. The challenge at the present time is to find ultrasonic techniques that are sensitive enough to detect small changes at the original interface. A number of diffusion bonds has been made that ...


Ultrasonic Inspection, Material Noise And Surface Roughness, Mehmet Bilgen, James H. Rose, Peter B. Nagy Jan 1993

Ultrasonic Inspection, Material Noise And Surface Roughness, Mehmet Bilgen, James H. Rose, Peter B. Nagy

Review of Progress in Quantitative Nondestructive Evaluation

The ultrasonic detection of subsurface flaws, such as cracks or voids, may be greatly degraded by the presence of rough surfaces [1,2]. The loss of signal-to-noise arises for three reasons. First, the randomization of the phase of the wave by the roughness may reduce the phase coherent signal from the flaw. Second, additional noise is generated directly by the reflection of the incident beam by the rough surface. Finally, the material noise is modified.


Theory Of Ultrasonic Backscatter From Multiphase Polycrystalline Solids, James H. Rose Jan 1993

Theory Of Ultrasonic Backscatter From Multiphase Polycrystalline Solids, James H. Rose

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasound scatters from the microscopic single crystals that constitute polycrystalline solids. The scattering originates from crystallite-crystallite variations in the density and elastic constants. For single-phase materials, each crystallite has the same density and the same crystalline symmetry. Hence, in single-phase materials scattering arises from the variation in velocity, which in turn is due to the anisotropy of the elastic constants and the more or less random orientation of the crystallites [1,2]. The situation is considerably more complicated in multiphase alloys where the density, the crystal symmetry and the elastic constants vary from crystallite to crystallite.