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Statistical Comparative Analyses of engineering Properties of Microwave and Conventionally Sintered Alumina

MRS Online Proceedings Library 1996年第1期430卷 453-458页

作者： K.R. Binger S.A. Freeman D.J. Grellinger R.F. Cooper J.H. Booske Department of Electrical and Computer Engineering University of Wisconsin - Madison Madison USA Material Science Program University of Wisconsin - Madison Madison USA Department of Material Science and Engineering University of Wisconsin - Madison Madison USA

Processing conditions such as temperature, soak time, and heating rate affect the final density of conventionally-sintered and microwave-sintered ceramics. Of additional importance is the question of whether microwave-sintered ceramics display intrinsically superior macroscopic engineering properties compared with conventionally-sintered control specimens. An analysis using the Yates algorithm indicates that the processing condition which has the largest impact on the density of the specimen is the heating method (microwave vs. conventional). The microwave-sintered specimens resulted in higher densities and higher fracture strengths. However, it was determined that the higher fracture strengths were due to the higher sintered densities rather than a significantly different microstructure.

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A study of the enhanced oxidation of poly-N-vinylimidazole films on copper

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Journal of Polymer science 1996年第4期34卷

作者： J. E. Hansen B. I. Rickett J. H. Payer H. Ishida Department of Macromolecular Science and Engineering Case Western Reserve University Cleveland Ohio 44106-7202 Department of Material Science and Engineering Case Western Reserve University Cleveland Ohio 44106-7202

The degradation of poly- N -vinylimidazole films on copper substrates was studied by Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy. Infrared measurements on samples heated at 300°C for 15 minutes revealed that the oxidation of the polymer was accelerated by the copper. X-ray photoelectron spectroscopy showed that a layer of copper oxide was formed on top of the oxidized film. Copper ions were also detected within the polymer layer. © 1996 John Wiley & Sons, Inc.

关键词： copper corrosion poly-N-vinylimidazole oxidation

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Oriented noncrystalline structure in PET fibers prepared with threadline modification process

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Journal of Polymer science 1996年第12期34卷

作者： Gang Wu Jiao-Dong Jiang Paul A. Tucker John A. Cuculo Department of Polymer Science Beijing University of Chemical Technology Beijing 100029 China Department of Fibrous Material Engineering Beijing Institute of Clothing Technology Beijing 100029 China Fiber & Polymer Science Program College of Textiles North Carolina State University Raleigh North Carolina 27695

The development of an oriented noncrystalline phase in a semicrystalline polymer filament has been studied via X-ray scattering. These unique PET fibers contain a relatively high noncrystalline content and also have high tenacity, high modulus, and low breaking elongation. Fiber properties were found to be very responsive to the oriented amorphous phase content. This phase was utilized for interpreting noncrystalline orientation in PET fibers produced by a new extrusion technique. Here, the oriented noncrystalline regions in a series of PET fibers varies from 6% to 63%, depending strongly on the production conditions. In particular, samples produced with a newly developed threadline modification process possess a high content of oriented noncrystalline polymer. Measurements such as dynamic and static mechanical properties have been performed on various samples, and these properties are related to the oriented noncrystalline phase. The results provide direct evidence for the existence of highly oriented noncrystalline material in these unique PET fibers spun with a threadline modification process. © 1996 John Wiley & Sons, Inc.

关键词： poly(ethylene terephthalate) controlled threadline dynamics orientation oriented noncrystalline phase fiber properties crystallinity

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IMPRESSION AND DIFFUSIONAL CREEP OF ANISOTROPIC MEDIA

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JOURNAL OF APPLIED PHYSICS 1995年第1期77卷 110-117页

作者： YANG, FQ LI, JCM Material Science Program Department of Mechanical Engineering University of Rochester Rochester New York 14627

Some diffusion problems in the impression and diffusional creep of aniostropic materials are analyzed. It is found that at the limit of low stress, both the diffusional creep rate and impression velocity are proportional to the applied stress. For a parallelepiped crystal under simple tension or compression in teh Z direction, the diffusional creep rate depends on all three principal diffusivities, D//X, D//Y, and D//Z. Two limiting cases depend on the quantity √D//XD//Y/D//X. When this quantity is large the creep rate is proportional to √D//Z but when it is small the creep rat eis independent of D//Z. For a cylindrical crystal under tension or compression in the axial Z direction, the creep rate depends on D//r/D//Z. When the ratio is large, the creep rate is the same as the isotroic case except that the effective diffusivity is √C//rD//Z. When the ratio is small, the creep rate is proportional to D//r and independent of D//Z. For the impression creep of a half-space the punch velocity is proportional to the geometric mean of the principal diffusivities parallel and perpendicular to the loading direction, nd inversely proportional to the punch dimension. For impression creep of a thin film deposited on an impermeable substrate under the same punching stress the impression velocity is dependent only on the diffusivity parallel to the thin film, and inversely proportional to the square of the punch dimension. Without the substrate, the impression velocity is dependent only on the diffusivity p

关键词： DIFFUSION ANISOTROPY CREEP (materials)

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IMPRESSION TEST OF 63SN-37PB EUTECTIC ALLOY

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materialS science AND engineering A-STRUCTURAL materialS PROPERTIES MICROSTRUCTURE AND PROCESSING 1995年第1-2期201卷 40-49页

作者： YANG, FG LI, JCM YANG, FQ Material Science Program Department of Mechanical Engineering University of Rochester Rochester NY 14627 USA

Impression creep and stress relaxation experiments on the Sn-Pb eutectic alloy were carried out in the RSA II instrument modified to use a 0.5 mm diameter cylindrical punch under 1.5-47 MPa punching stress and within a temperature range of 25 degrees C to 110 degrees C. Based on a power law between the impression velocity and stress or between the stress rate and stress, the exponent increased with stress from 1 to 3.5 within the temperature range 80-110 degrees C and 2.5 to 6 within the range 25-65 degrees C. These exponents were generally comparable to those reported in the literature. Because of the change of stress exponent, several mechanisms have been proposed. However, the stress dependence was found to obey a hyperbolic sine function of stress for all the stresses and temperatures studied. Similarly before using the hyperbolic sine function, the activation energy was found to increase with stress, an abnormal behaviour. Fortunately, after using the hyperbolic sine function, a single activation energy, 55 kJ mol(-1) was obtained. Based on the present data, a single mechanism of interfacial viscous shearing between the two eutectic phases is proposed for both creep and stress relaxation. In addition to the effect of stress and temperature, the impression velocity based on this model should be directly proportional to the punch radius and inversely proportional to the nth (n = 1-3) power of the size of phase particles. These predictions are consistent with available information in the literature.

关键词： IMPRESSION CREEP STRESS RELAXATION SN-PB EUTECTIC ALLOY

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IMPRESSION CREEP BY AN ANNULAR PUNCH

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MECHANICS OF materialS 1995年第1期21卷 89-97页

作者： YANG, FQ LI, JCM Material Science Program Department of Mechanical Engineering University of Rochester Rochester NY 14627 USA

The diffusion problem of impression creep of a half-space by an annular punch is analyzed. The results indicate that, at low stresses, the impression velocity is proportional to the punching stress. For the same punching stress the impression velocity increases without limit as the annular thickness approaches zero. The limiting case for a solid punch agrees with previous results, namely, (1) the impression velocity for interface diffusion is inversely proportional to the square of the punch radius, and (2) that for bulk diffusion the impression velocity is inversely proportional to the punch radius. For a thin annular punch, the impression velocity reduces to that of impression creep by a straight punch, i.e., the impression velocity for interface diffusion is inversely proportional to the square of the thickness of the annular punch, and that for bulk diffusion it is inversely proportional to the thickness of the annular punch. In fact, the straight punch is a good approximation (larger by less than 5%) if the inner radius/outer radius ratio is larger than 0.1 for interface diffusion and 0.2 for bulk diffusion.

关键词： CREEP DIFFUSION ANNULAR PUNCH IMPRESSION INDENTATION

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DAMPING PROPERTIES OF CONSOLIDATED IRON AND GRAPHITE POWDERS

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ACTA METALLURGICA ET materialIA 1995年第2期43卷 631-638页

作者： LIAN, YC MARLER, RT LI, JCM Material Science Program Department of Mechanical Engineering University of Rochester Rochester NY 14627 U.S.A.

Upon increasing the strain amplitude, the damping capacity of sintered (800 degrees C, 1 h) pure iron powders changes slowly at low strain amplitudes, increases at a threshold strain amplitude of about 8 x 10(-5), reaches a maximum, and then decreases. This behavior is the same for sintered graphite powders as well as for mixtures of graphite and iron powders except that the threshold strain amplitude is lower (2 x 10(-5)) for the composite. However, the low threshold is similar to that of the cast iron. With increasing graphite content, the modulus of the composite decreases, but the damping capacity increases. Both the damping capacity and Young's modulus of the composite are comparable to those of cast iron.

关键词： Powder metals

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SHIP SELF-DEFENSE PERFORMANCE ASSESSMENT METHODOLOGY

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NAVAL ENGINEERS JOURNAL 1994年第3期106卷 208-219页

作者： POLK, J MCCANTS, T GRABAREK, R James Polk:is currently a principal financial and technical advisor for PRC Inc. He is working in support of PEO (TAD) Ship Self-Defense Program in several areas including performance assessment. He retired from the Navy in 1991 after several years at sea and various material command assignment including command of Caron (DD-970) and Aegis technical director. He is an ASNE Member who has an MS in physics from the Naval Postgraduate School. He graduated from the University of Notre Dame with a BS in civil engineering and earned his commission through the NROTC program there. Thomas H. McCants Jr.:is currently a principal system engineer in the ship defense department of the Naval Surface Warfare Center Dahlgren Division. He is supporting the PEO (TAD) in systems engineering and analysis and is supporting the Office of Naval Research in a 6.2 Ship Self-Defense program. He was previously the lead lab program manager for STANDARD Missile led the Aegis Systems Analysis and T&E organization at NSWC was Phalanx CIWS lead lab program manager and was the air target vulnerability program manager at the Center. In 1977–78 Mr. McCants was the NSAP science advisor to COMOPTEVFOR Norfolk. He graduated from VPI&SU with a BS in aerospace engineering and is pursuing a MS in systems engineering from VPI&SU. Robert Grabarek:is currently an electronics engineer in the requirements and analysis branch of the Ship Self-Defense Program Office. He is a 1981 graduate of the U.S. Naval Academy and served six years on active duty as a surface warfare officer. He has earned his MA in operations research and industrial engineering from VPI&SU.

Robust ship AAW defense capability is a priority requirement that enables Naval Forces to conduct joint expeditionary force operations in littoral environments. As an aid to achieving this capability for all ship classes, the Navy has reorganized its management of ship defense. A major focus of these efforts is the development of a fully automatic, integrated combat system for non-Aegis ships which is based on coordinated detection, control, and hard kill/electronic warfare (HK/EW) engagement functions. A phased approach to attaining this fully integrated capability has been established which includes major element upgrade introduction when technology and budget permit. This paper describes the ship self-defense performance assessment methodology which has been adopted to support the review and decision process for future planning and budgeting. This process is a continuation and refinement of that used to provide data for the Office of the Secretary of Defense Fall 1991 Conventional Systems Committee Ship Self-Defense Review. The performance assessment methodology starts with definition of survivability requirements by ship class, combat system configurations, Anti-Ship Missile threat, and operational scenario. Viable self-defense system element options are then identified. The capability of these options are then characterized for input into ship level performance prediction models. Three partitions of performance prediction modeling are made: hard kill elements only, electronic warfare element only, and integrated HK/EW. The most significant accomplishment of this effort, beyond providing data to support programmatic decision, has been the creation of a truly integrated HK/EW surface ship combat system model that interleaves HK and EW timelines and allows parametric variation to evaluate options. Because of classification, only generic examples of numerical result will be presented. However, the procedures for establishing the modelling process, prioritization of

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IMPRESSION CREEP OF A THIN-FILM BY VACANCY DIFFUSION .2. CYLINDRICAL PUNCH

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JOURNAL OF APPLIED PHYSICS 1993年第7期74卷 4390-4397页

作者： YANG, FQ LI, JCM Material Science Program Department of Mechanical Engineering University of Rochester Rochester New York 14627

The diffusion problem in the impression creep of a thin film by a cylindrical punch is analyzed. It is found that at low stresses the impression velocity is proportional to the punching stress. For the same punching stress and the same punch radius the impression velocity decreases for a rigid substrate, and increases without the substrate as the thickness of film decreases. Two limiting cases for the rigid substrate agree with the previous work, namely, the impression velocity is inversely proportional to the punch radius for impression creep of a half-space, and inversely proportional to the square of the punch radius for impression creep of a thin film. Without the substrate the impression velocity for impression creep of a thin film is inversely proportional to the thickness of the film and independent of the punch radius.

关键词： THIN FILMS CREEP VACANCIES DIFFUSION STRESSES THICKNESS

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IMPRESSION CREEP OF A THIN-FILM BY VACANCY DIFFUSION .1. STRAIGHT PUNCH

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JOURNAL OF APPLIED PHYSICS 1993年第7期74卷 4382-4389页

作者： YANG, FQ LI, JCM Material Science Program Department of Mechanical Engineering University of Rochester Rochester New York 14627

A closed-form solution for diffusion in two dimensions is obtained for impression creep of a thin film by a straight punch. The results show that for a rigid impermeable substrate the penetration rate is proportional directly to the thickness of the film and inversely to the square of the punch width. Without the substrate the penetration rate is inversely proportional to the thickness of the film and independent of the punch width.

关键词： THIN FILMS CREEP VACANCIES DIFFUSION THICKNESS NUMERICAL SOLUTION STRESSES

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