Engineering Commons^™

The Evolution Of Best Practices With High Performance Steel For Bridges, Edward P. Wasserman, W. Henry Pate, Tim Huff

Advanced Materials for Construction of Bridges, Buildings, and Other Structures III

High Performance Steel, grade 70 (HPS-70W) became available for use in early 1996 for fabrication and testing in bridges. Two (2) states, Nebraska and Tennessee agreed to be the first to implement usage. This paper provides a discussion of 3 Tennessee case histories in which high performance steel has been used to achieve weight and cost economies.

Variable Engagement Model For The Design Of Fibre Reinforced Concrete Structures, Jackie Yen Lei Voo, Stephen J. Foster

Advanced Materials for Construction of Bridges, Buildings, and Other Structures III

In this paper a model is developed to describe the behaviour of randomly orientated discontinuous fibres in reinforced composites subject to uniaxial tension. The model is built by integrating the behaviour of single, randomly oriented, fibres over 3D space and is capable of describing the peak and post-peak response of fibre-cement-based composites in tension. The model is used to form a constitutive law for use in finite element analysis of reactive powder concrete members with a prestressed reactive powder beam failing in shear analysed. A good correlation between the theoretical and experimental results attained.

The Effect Of Aggregate Particle Size On Formation Of Geopolymeric Gel, Christine Isabella , Grant C. Lukey, Hua Xu, Jannie S.J. Van Deventer

Advanced Materials for Construction of Bridges, Buildings, and Other Structures III

Due to enhanced mechanical and chemical properties, geopolymeric materials are a potential alternative to ordinary Portland cement and high-strength cement for the construction industry. The effects of aggregate particle size on the formation and the mechanical properties of geopolymeric materials are investigated in the current work. The addition of soluble silicates to the alkaline activator was found to increase the dissolution of silicate ions from the aggregate into the geopolymer binder phase. The results indicate that the surface area of aggregate influences the strength development of a geopolymer.

Histar High Performance Hot-Rolled Beams, Lucien Weber

Advanced Materials for Construction of Bridges, Buildings, and Other Structures III

The construction industry is continuously looking for superior building components. Innovative production processes are, in combination with tight quality control, the keys to structural steel grades with outstanding properties. Especially the thermomechanical treatment allows for combining material properties which were formerly thought to be incompatible: high yield strength for big material thicknesses, good toughness and excellent weldability.

This paper presents the Quenching and Self-Tempering (QST) process which allows for the production of heavy hot-rolled H-beams in high strength structural steel grades with excellent weldability characteristics. The new steel grades fully comply and even exceed the requirements of the European and …

Thermal Properties Of La₀.₅Sr₀.₅Co₁₋ₓnixo₃-D Ceramics Using Photopyroelectric Technique, M. T. Sebastian, C. Preethy Menon, J. Philip, Robert W. Schwartz

Mechanical and Aerospace Engineering Faculty Research & Creative Works

La0.5Sr0.5Co1-xNixO3-delta (0<= x<= 0.6) ceramics were prepared using a conventional solid-state ceramic route. The thermal properties—thermal conductivity and heat capacity—of these ceramics were measured by the photopyroelectric technique. The thermal conductivity was found to increase with increasing Ni content. These materials were also found to exhibit a metallic-type variation of thermal conductivity with temperature, and no metal-insulator (M-I) transition was found to occur in any of the samples prepared by this route. However, a M-I transition was found to occur in La0.5Sr0.5CoO3-delta samples prepared by hot pressing. The difference is attributed to variations in oxygen content in the samples.

Finite-Temperature Anisotropy Of Ptco Magnets, Ralph Skomski, Arti Kashyap, David J. Sellmyer

Materials Research Science and Engineering Center: Faculty Publications

The temperature dependence of the magnetocrystalline anisotropy of PtCo and its atomic origin are investigated by first-principle and model calculations. The Pt spin moment necessary to realize the leading 5d anisotropy contribution is due to neighboring Co atoms. At finite temperatures, Co spin disorder strongly reduces the Pt moment and the anisotropy. This is in contrast to the situation encountered in 3d and 3d–4f magnets, where the atomic magnetic moments remain largely conserved, even above the Curie temperature. A consequence of the L1₀ mechanism is that theK₁ (T) curve of exhibits a negative curvature, in contrast to the …

Exchange Interactions And Curie Temperature Of Y–Co Compounds, Arti Kashyap, Ralph Skomski, Renat F. Sabiryanov, Sitaram Jaswal, David J. Sellmyer

Materials Research Science and Engineering Center: Faculty Publications

The Curie temperature of rare-earth Co intermetallics is investigated by self-consistent spin-polarized electronic-structure calculations on Y–Co compounds. The total exchange interaction of a given site with all other sites (J_o) is calculated by the linear-muffin-tin-orbital method using the local force theorem and employed to obtain mean-field Curie-temperature estimates. The theoretical predictions for YCo₃, YCo₅, and Y₂Co₁₇ are in fair agreement with the experimental Curie temperatures. For YCo₅, the variation of exchange interactions (J_ij) with distance is analyzed, and it is discussed how the presence of nonequivalent cobalt …

Modeling Corrosion In Oxygen Controlled Lbe Systems With Coupling Of Chemical Kinetics And Hydrodynamics-Task V: Fourth Quarterly Report 06/01/2003-08/30/2003, Samir Moujaes, Yitung Chen

Transmutation Sciences Materials (TRP)

The Lead-Bismuth eutectic (LBE) has been determined from previous experimental studies by the Russians and the European scientific community to be a potential material that can be used as a spallation target and coolant for the TRP proposed application. Properly controlling the oxygen content in LBE can drastically reduce the LBE corrosion to structural steels. However, existing knowledge of material corrosion performance was obtained from point-wise testing with only very sparse experimental data. Scientists have noticed that the concentration of oxygen dissolved in the liquid alloy could control the corrosion rate of steels exposed to Pb or Pb-Bi. At high …

Modeling Corrosion In Oxygen Controlled Lbe Systems With Coupling Of Chemical Kinetics And Hydrodynamics-Task V: Annual Report -Phase Ii 09/01/2002-08/30/2003, Samir Moujaes, Yitung Chen

Transmutation Sciences Materials (TRP)

The Lead-Bismuth eutectic (LBE) has been determined from previous experimental studies by the Russians and the European scientific community to be a potential material that can be used as a spallation target and coolant for the TRP proposed application. Properly controlling the oxygen content in LBE can drastically reduce the LBE corrosion to structural steels. However, existing knowledge of material corrosion performance was obtained from point-wise testing with only very sparse experimental data. Scientists have noticed that the concentration of oxygen dissolved in the liquid alloy could control the corrosion rate of steels exposed to Pb or Pb-Bi. At high …

Semiconductor Wafer Processing System With Vertically-Stacked Process Chambers And Single-Axis Dual-Wafer Transfer System, Richard N. Savage, Frank S. Menagh, Helder R. Carvalheira, Philip A. Troiani, Dan L. Cossentine, Eric R. Vaughan, Bruce E. Mayer

Materials Engineering

A semiconductor wafer processing system including a multi-chamber module having vertically-stacked semiconductor wafer process chambers and a loadlock chamber dedicated to each semiconductor wafer process chamber. Each process chamber includes a chuck for holding a wafer during wafer processing. The multi-chamber modules may be oriented in a linear array. The system further includes an apparatus having a dual-wafer single-axis transfer arm including a monolithic arm pivotally mounted within said loadlock chamber about a single pivot axis. The apparatus is adapted to carry two wafers, one unprocessed and one processed, simultaneously between the loadlock chamber and the process chamber. A method …

Research On Advanced Technologies For Housing: Optimized Frp-Reinforced Osb Panels For Disaster-Resistant Construction, William S. Davids

University of Maine Office of Research Administration: Grant Reports

The satisfactory performance of wood-framed housing in a seismic or wind event requires a sufficiently strong, ductile, and energy-absorbing lateral force-resisting system. This project will focus on the development of optimized synthetic fiber-reinforced OSB panels to improve the disaster resistance of conventional wood-frame construction. The project research will employ response simulation, small-scale connection and durability testing, and full-scale shear wall testing. Various fiber-reinforced polymer (FRP) systems will be investigated for reinforcing the OSB panels. Shear tests of individual nailed connections between FRP-reinforced and plain OSB panels and lumber framing will be conducted to determine monotonic and cyclic fastener load-slip relationships. …

Design And Analysis For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides: Quarterly Progress Report 5/16/03- 8/15/03, Yitung Chen, Randy Clarksean, Darrell Pepper

Fuels Campaign (TRP)

The analysis of mold filling and solidification continues with progress being made for the consideration of these two features within one model. Analysis of the induction heating process of an Induction Skull Melter (ISM) is under study. Efforts are underway to validate the modeling procedure and specific comparisons are being made to previously published work. Few detailed modeling results have been reported by other researchers, making the validations an important part of the overall modeling process. Skin heating depths, power deposition rates, and other process parameters are being evaluated for use in upcoming furnace design simulations. Efforts are beginning on …

Modeling Corrosion In Oxygen Controlled Lbe Systems With Coupling Of Chemical Kinetics And Hydrodynamics - Phase Three, Samir Moujaes, Yitung Chen

Transmutation Sciences Materials (TRP)

The proposed work will combine chemical kinetics and hydrodynamics in target and test-loop lead-bismuth eutectic (LBE) systems to model system corrosion effects. This approach will result in a predicative tool that can be validated with corrosion test data, used to systematically design tests and interpret the results, and provide guidance for optimization in LBE system designs. The task includes two subtasks. The first subtask is to try to develop the necessary predictive tools to be able to predict the levels of oxygen and corrosion products close to the boundary layer through the use of Computational Fluid Dynamics (CFD) modeling. The …

Oscillatory Interlayer Exchange Coupling And Its Temperature Dependence In [Pt/Co]3/Nio/[Co/Pt]3 Multilayers With Perpendicular Anisotropy, Z. Y. Liu, Shireen Adenwalla

Materials Research Science and Engineering Center: Faculty Publications

Interlayer exchange coupling that oscillates between antiferromagnetic and ferromagnetic as a function of NiO thickness has been observed in [Pt(5 Å)/Co(4 Å)]₃/NiO(t_NiO Å)/[Co(4 Å)/Pt(5 Å)]₃ multilayers with out-of-plane anisotropy. The period of oscillation corresponds to ~2 monolayers of NiO. This oscillatory behavior is possibly attributed to the antiferromagnetic ordering in NiO. The antiferromagnetic interlayer exchange coupling for the 11 Å NiO layer shows an increase in coupling strength with increasing temperature, in agreement with the quantum interference model of Bruno for insulating spacer layers. A coexistence of exchange biasing and antiferromagnetic interlayer exchange coupling has …

Closely Linear Temperature Dependence Of Exchange Bias And Coercivity In Out-Of-Plane Exchange-Biased [Pt/Co] 3/Nio (11 Å) Multilayer, Z.Y. Liu, Shireen Adenwalla

Materials Research Science and Engineering Center: Faculty Publications

Strong out-of-plane exchange biasing has been observed in out-of-plane exchange biased [Pt (5 Å)/Co (4 Å)] ₃/NiO (11 Å) multilayer with perpendicular easy axis. Both the exchange field H_E and coercivity H_C display a closely linear temperature dependence except at very low temperatures. A thin NiO layer coated on the top of a Pt/Co multilayer has a great effect on the domain pattern of the Pt/Co multilayer, which is in a more irregular configuration with much smaller domain sizes than the uncoupled Pt/Co multilayer. A simulation according to Malozemoff's random field model gives a good agreement to …

Development Of Advanced High Temperature Heat Exchangers: Proposal, University Of Nevada, Las Vegas. Research Foundation

Publications (NSTD)

A research team led by the University of Nevada, Las Vegas (UNLV) Research Foundation proposes a project to develop advanced high temperature heat exchangers (HTHX) for hydrogen production and electrical energy conversion from advanced nuclear reactor concepts. This project will also support the development of Generation IV reactors. The research team includes researchers from UNLV, General Atomics (GA), Sandia National Laboratories (SNL), The University of California, Berkeley UCB) and Oak Ridge National Laboratory (ORNL).

The proposed project will be administered by the University of Nevada Las Vegas Research Foundation (UNLVRF). UNLVRF will provide the overall contract administration and is the …

Comment On: 'Depolarization Corrections To The Coercive Field In Thin-Film Ferroelectrics', Stephen Ducharme, Vladimir Fridkin

Stephen Ducharme Publications

The Letter by Dawber et al. [J. Phys.: Condens. Matter 15 L393 (2003)] notes that incomplete screening in the electrodes of a ferroelectric capacitor can result in an underestimate for the true coercive field in films of nanometer thickness. We show that their estimate of the magnitude of this correction it too large in the case of ferroelectric copolymer Langmuir- Blodgett films and, as a result, invalidates the claim that finite-size scaling of the ferroelectric coercive field is evident in films thinner than 15 nm.

Niti - Magic Or Phase Transformation?, Katherine C. Chen

Materials Engineering

NiTi alloys possess exciting properties and are staples in materials demonstrations. The shape memory effect and superelasticity property of NiTi fascinate people, but actually require significant materials knowledge to fully understand the phenomena. A laboratory dealing with phase transformations was thus developed to capitalize on the allure of NiTi for a junior/senior level “Thermodynamics and Kinetics of Materials” course. Students examine and characterize the shape memory and superelastic properties of NiTi wire, and then realize the difference is in the transformation temperature (i.e., Af - the austenitic finish temperature). They then use the phase diagram and TTT diagram to develop …

How We Learned To Love The Phase Diagram With A Ti-Cr Alloy Characterization Lab, Katherine C. Chen

Materials Engineering

While many students learn how to read and use a phase diagram in introductory materials courses, greater appreciation for such a tool can be garnered through the laboratory setting. A laboratory module for a “Structures of Materials” class (a “core class” for materials majors) has been developed to demonstrate the usefulness of phase diagrams, as well as, to emphasize the connections among processing, structure, and properties. Competence in determining stable phases, phase compositions, and mass fractions of phases are not the end goal, per se, but transpire since the skills are required to help solve a puzzle. Students are given …

Environment-Induced Degradation And Crack-Growth Studies Of Candidate Target Materials: Annual Progress Report (May 2002 – May 2003), Ajit K. Roy, Brendan O'Toole

Transmutation Sciences Materials (TRP)

As indicated in the original proposal, the primary objective of this task is to evaluate the effect of hydrogen on environment-assisted cracking of candidate target materials for applications in spallationneutron- target (SNT) systems such as accelerator production of tritium (APT) and accelerator transmutation of waste (ATW). The materials selected for evaluation and characterization are martensitic stainless steels including Alloy HT-9, Alloy EP 823 and Type 422 stainless steel. The susceptibility to stress corrosion cracking (SCC) and hydrogen embrittlement (HE) of these materials are being evaluated in aqueous environments of interest using tensile specimens under constant load and slow-strain-rate (SSR) conditions. …

Use Of Positron Annihilation Spectroscopy For Stress-Strain Measurements: Annual Progress Report (May 2002 – May 2003), Ajit K. Roy

Transmutation Sciences Materials (TRP)

The purpose of this collaborative research project involving the University of Nevada Las Vegas (UNLV) and Idaho State University (ISU) to evaluate the feasibility of determining residual stresses of welded, bent (three-point-bend), and cold-worked engineering materials using a new non-destructive technique based on positron annihilation spectroscopy. The proposed technique is the use γ-rays from a small MeV electron Linear accelerator (LINAC) to generate positrons inside the sample via pair production. This method can be used for materials characterization and investigation of defects in thick samples, which could not be accomplished by conventional positron technique or other non-destructive methods. The data …

Modeling, Fabrication, And Optimization Of Niobium Cavities: Phase Ii Final Report, Robert A. Schill Jr., Mohamed Trabia, William Culbreth

Transmutation Sciences Materials (TRP)

Niobium cavities are important parts of the integrated NC/SC high-power linacs. Over the years, researchers in several countries have tested various cavity shapes. They concluded that elliptically shaped cells are the most appropriate shape for superconducting cavities. The need for very clean surfaces lead to the use of a buffered chemical polishing produce for surface cleaning to get good performance of the cavities. The second phase has resulted in an experimental setup of a fluid flow experiment with experimentation to be completed in the third year. Some of these results were presented at American Nuclear Society, Student Conference April 2-5, …

Students' Perceptions Of Both The Certainty And The Deterrent Effect Of Potential Consequences Of Cheating, Cynthia J. Finelli, Trevor S. Harding, Donald D. Carpenter, Honor J. Passow

Materials Engineering

No abstract provided.

Quarterly Report For The Trp Project, March–June 2003, Samir Moujaes, Yitung Chen, Kanthi Kiran Daiska, Chao Wu

Transmutation Sciences Materials (TRP)

The MTL is assumed to be a 5m long rectangular loop with a circular cross-section. Because of the non-symmetry, and due to the active participation of the secondary flows due to the elbows present in the rectangular loop model, the geometry is considered as a 3D model.

When the regions of maximum corrosion and precipitation are compared, they fall in the same zone for both the analytical and simulated models. The reason for a larger concentration flux in the case of turbulent flow than for the laminar flow can be explained by the concept of higher lateral diffusion in the …

Growth And Optical Properties Of Srbi₂Nb₂O₉ Ferroelectric Thin Films Using Pulsed Laser Deposition, Pingxiong Yang, David L. Carroll, John Ballato, Robert W. Schwartz

Mechanical and Aerospace Engineering Faculty Research & Creative Works

High quality SrBi2Nb2O9 ferroelectric thin films were fabricated on platinized silicon using pulsed laser deposition assisted with dc glow discharge plasma. Microstructure and ferroelectric properties of the films were characterized. Optical properties of the thin films were studied by spectroscopic ellipsometry and photoluminescence from the ultraviolet to the infrared region. Optical constants, n~0.56 in the infrared region and n~2.24 in the visible spectral region, were determined through multilayer analyses on their respective pseudodielectric functions. The band-gap energy is estimated to be 3.60 eV. A photoluminescence peak at 0.78 µm, whose intensity decreases with decreasing temperature, was observed when excited with …

Ferromagnetic Domain-Wall Behavior During Reversal And Thermally Activated Antiferromagnetic Reversal In An Exchange-Biased Nio/Nife Bilayer, Z. Y. Liu, Shireen Adenwalla

Materials Research Science and Engineering Center: Faculty Publications

The magnetization reversal mechanism in an exchange-biased NiO/Ni₈₁Fe₁₉ bilayer has been investigated using the magneto-optic Kerr effect and magnetic force microscopy imaging. The asymmetric reversal along the unidirectional axis and the two-step reversal process along the hard axis are promoted by ferromagnetic domain-wall behavior in the decreasing and increasing field branches of the as-deposited hysteresis loop, which is strongly related to the exchange coupling at the interface and the distribution of orientation of the net magnetization at the interface carried by the antiferromagnetic domains. The temperature dependence of the exchange bias and coercivity shows the thermally activated …

Development Of A Mechanistic Understanding Of High-Temperature Deformation Of Alloy Ep-823 For Transmutation Applications Trp Task-10: Quarterly Progress Report (March 01 – May 31, 2003), Ajit K. Roy, Brendan O'Toole

Transmutation Sciences Materials (TRP)

The purpose of this project is to evaluate the elevated temperature tensile properties of Alloy EP- 823, a leading target material for accelerator-driven waste transmutation applications. This alloy has been proven to be an excellent structural material to contain the lead-bismuth-eutectic (LBE) nuclear coolant needed for fast spectrum operations. Very little data exist in the open literature on the tensile properties of this alloy. The test material will be thermally treated prior to the evaluation of its tensile properties at temperatures relevant to the transmutation applications. The deformation characteristics of tensile specimens, upon completion of testing, will be evaluated by …

Development Of A Mechanistic Understanding Of High-Temperature Deformation Of Alloy Ep-823 For Transmutation Applications, Ajit K. Roy, Brendan O'Toole

Transmutation Sciences Materials (TRP)

The purpose of this project is to evaluate the elevated temperature tensile properties of Alloy EP-823, a leading target material for accelerator-driven waste transmutation applications. This alloy has been proven to be an excellent structural material to contain the lead-bismuth-eutectic (LBE) nuclear coolant needed for fast spectrum operations. However, very little data exist in the open literature on the tensile properties of this alloy. The selection of Alloy EP-823 as the test material in the proposed task is based on the recommendation of our collaborator at the Los Alamos National Laboratory (LANL). The test material will be thermally treated prior …

Atomic, Electronic, And Magnetic Properties Of Magnetic Tunnel Junctions, I.I. Oleynik, Evgeny Y. Tsymbal

Materials Research Science and Engineering Center: Faculty Publications

We report results of first-principles density-functional studies of the atomic and electronic structure of Co/Al₂O₃/Co and Co/SrTiO₃/Co magnetic tunnel junctions (MTJs). The atomic structure has been studied for different interface terminations and the interfacial energetics was quantified based on the work of separation. Based on energetics of cohesion, the O-terminated and TiO₂-terminated interfaces were identified as the most stable structures for Co/Al₂O₃/Co and Co/SrTiO₃/Co MTJs, respectively. The electronic structure was analyzed using local densities of states. We found that the electronic structure of the O-terminated Co/Al …

Design And Analysis For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides: Quarterly Progress Report 2/16/03- 5/15/03, Yitung Chen, Randy Clarksean, Darrell Pepper

Fuels Campaign (TRP)

Progress continues on the analysis of casting and solidification of the melt into molds. Modeling results for constant pressure casting, which is more realistic, have been obtained and produce physically realistic results for flow that starts, flows, and then eventually stops as it enters the mold. Potential mass transfer modeling features (Lammuir’s law for example) are being studied to enhance the capabilities of a mass transfer in a detailed system model. Different parameters are being varied as part of a parametric study to evaluate factors that impact the flow of the melt into the molds. The ability to include the …