Open Access. Powered by Scholars. Published by Universities.®

Materials Science and Engineering Commons™

Open Access. Powered by Scholars. Published by Universities.®

Purdue University

Discipline
Keyword
Publication Year
Publication
Publication Type

Articles 301 - 330 of 458

Full-Text Articles in Materials Science and Engineering

Dynamic Triaxial Compression Experiments On Borosilicate And Soda-Lime Glass, John T. Chojnacki Oct 2015

Dynamic Triaxial Compression Experiments On Borosilicate And Soda-Lime Glass, John T. Chojnacki

Open Access Theses

A series of compression experiments were performed on borosilicate and soda-lime glass using a triaxial compression Kolsky bar. The triaxial compression Kolsky bar differs from a traditional Kolsky bar by having two pressure chambers, one enclosing the specimen and the other enclosing the end of the transmission bar, so that a specimen may be pre-stressed axially and radially before a dynamic axial load is applied. The result is a modified Kolsky bar capable of measuring axial deformation and axial stresses of a specimen at various strain rates under a range of confinement pressures. Borosilicate glass was subjected to triaxial confinement …

Go to article

Molexpl: A Tool For Ab Initio Data Exploration And Visualization, Xueying Wang, Nicolas Onofrio, Alejandro Strachan Sep 2015

Molexpl: A Tool For Ab Initio Data Exploration And Visualization, Xueying Wang, Nicolas Onofrio, Alejandro Strachan

The Summer Undergraduate Research Fellowship (SURF) Symposium

Density functional theory (DFT) based on ab initio theory, is a powerful method to resolve the electronic structure of atoms, molecules and solids. However, in practical, DFT is limited to few hundreds of atoms. To overcome this limitation, researchers have developed empirical interatomic potentials implemented in molecular dynamics (MD) simulations. MD ignores the movements of electrons and describes bonding and non-bonding interaction as a function of the distance between atoms called force fields (FF) or interatomic potentials. These empirical potentials are optimized against large datasets of DFT calculations relevant to describe the interactions between the atoms included in the training …

Go to article

Grain Boundary Migration Of Nio-Mgo Alloys, Xin Li Phuah, David Lowing, John Blendell Aug 2015

Grain Boundary Migration Of Nio-Mgo Alloys, Xin Li Phuah, David Lowing, John Blendell

The Summer Undergraduate Research Fellowship (SURF) Symposium

Grain boundary engineering offers enhanced control of microstructure development during processing, leading to improved final material properties. However, using the effects of the interfacial energy anisotropy on grain boundary mobility to control microstructure development is not well understood. The NiO-MgO system is studied as it has complete solid solubility and a transition in the faceting behavior with composition due to changes in the interfacial energy anisotropy. NiO-MgO powders were produced through the amorphous citrate process and modifications to the process were made to reduce particle and agglomerate size. The powders were pressed and sintered in various conditions to produce fine …

Go to article

Simulating Low-Frequency Sonic Pulsations To Achieve Thrombolysis, Joseph C. Muskat, Matthew C. Pharris, Charles F. Babbs Aug 2015

Simulating Low-Frequency Sonic Pulsations To Achieve Thrombolysis, Joseph C. Muskat, Matthew C. Pharris, Charles F. Babbs

The Summer Undergraduate Research Fellowship (SURF) Symposium

Cardiovascular thrombosis may result in critical ischemia to a range of anatomical regions, constituting a leading cause of death in the United States. Current invasive treatments for such arterial blockages often yield blood clot recurrence, resulting in repeated hospitalization of patients. This research aims to show how internally introduced pressure oscillations may be used to initiate thrombolysis. We present a novel computational model for determining the resonant frequency and corresponding deformation of an idealized thrombus. Sinusoidal pressure differences across the thrombus induce axial displacements of frequency dependent amplitude. The maximum peak displacement occurs at a resonant frequency of 73 Hz …

Go to article

Characterizing Strain Accumulation, Residual Stress, And Microstructure Of Additive Manufactured Materials, Hannah K. Woods, Todd A. Book, Catalina Parada, Michael D. Sangid Aug 2015

Characterizing Strain Accumulation, Residual Stress, And Microstructure Of Additive Manufactured Materials, Hannah K. Woods, Todd A. Book, Catalina Parada, Michael D. Sangid

The Summer Undergraduate Research Fellowship (SURF) Symposium

Additive Manufacturing (AM) is a rapidly evolving fabrication technology beneficial for its cost-saving potential to produce complex, low-volume shapes. However, AM materials are currently limited to nonstructural applications due to variability in their structural integrity, particularly their fatigue lives. IN718, Ti64, and Al10MgSi specimens manufactured by Direct Metal Laser Sintering (DMLS) were characterized based on variation of post-processing techniques and build direction. To understand the impact of each variable, surface roughness, hardness, residual stresses, microstructure, and strain accumulation in response to Low Cycle Fatigue (LCF) were studied. The use of Electron Backscatter Diffraction (EBSD) provided grain orientation and grain size …

Go to article

Interactive Computer Aided Design Of Electrochemical Systems, Lucas D. Robinson Mr., R. Edwin García Dr., Aniruddha Jana Mr. Aug 2015

Interactive Computer Aided Design Of Electrochemical Systems, Lucas D. Robinson Mr., R. Edwin García Dr., Aniruddha Jana Mr.

The Summer Undergraduate Research Fellowship (SURF) Symposium

The most popular and widely used rechargeable battery numerical model, the dualfoil, was developed in fortran by John Newman and coworkers1-3, and enables the user to describe the time-dependent electrochemical transport of lithium and charge, through the application of concentrated solution theory in porous media. Such a model has enabled the design of many advanced lithium-ion batteries for hybrid and plug-in electric vehicles that can operate under high current densities. Historically, however, the dualfoil and other subsequently derived models are cumbersome and unwieldy when used, and offer limited flexibility regarding parameter variability, integration into more sophisticated numerical descriptions, coupling to …

Go to article

Effect Of Helium Ions Energy On Molybdenum Surfaces Under Extreme Conditions, Joseph Fiala, Jitendra K. Tripathi, Sean Gonderman, Ahmed Hassanein Aug 2015

Effect Of Helium Ions Energy On Molybdenum Surfaces Under Extreme Conditions, Joseph Fiala, Jitendra K. Tripathi, Sean Gonderman, Ahmed Hassanein

The Summer Undergraduate Research Fellowship (SURF) Symposium

Plasma facing components (PFCs) in fusion devices must be able to withstand high temperatures and erosion due to incident energetic ion radiations. Tungsten has become the material of choice for PFCs due to its high strength, thermal conductivity, and low erosion rate. However, its surface deteriorates significantly under helium ion irradiation in fusion-like conditions and forms nanoscopic fiber-like structures, or fuzz. Fuzz is brittle in nature and has relatively lower thermal conductivity than that of the bulk material. Small amounts of fuzz may lead to excessive contamination of the plasma, preventing the fusion reaction from taking place. Despite recent efforts, …

Go to article

Influence Of Warping On Stress For Restrained Concrete Slabs: For Application To Crcp, Corey M. Beck, W. Jason Weiss, Nathan T. Todd Aug 2015

Influence Of Warping On Stress For Restrained Concrete Slabs: For Application To Crcp, Corey M. Beck, W. Jason Weiss, Nathan T. Todd

The Summer Undergraduate Research Fellowship (SURF) Symposium

Continuously-reinforced concrete pavement (CRCP) is widely used in transportation system because of its low maintenance requirement. However, the need for large volumes of steel creates a high cost for new construction. The Illinois Tollway is preparing to substantially renovate highways in and around Chicago and this work seeks to understand how concretes of varying mixture designs can be made thinner by reducing the amount of built-in stress. The experiment examines warping in beams subjected to various degrees of restraint, in an effort to assess effectiveness at reducing warping in continuously reinforced concrete pavements. Value added methodologies such as internal curing …

Go to article

Characterization Of Hydrogel Curing Methods For Manufacturability, Hannah E. Brown, Rebecca K. Kramer, Edward L. White Aug 2015

Characterization Of Hydrogel Curing Methods For Manufacturability, Hannah E. Brown, Rebecca K. Kramer, Edward L. White

The Summer Undergraduate Research Fellowship (SURF) Symposium

In the field of soft robotics, hydrogels possess material properties that allow them to function as both soft strain sensors and dielectric elastomer actuators. However, there is still much that needs to be understood about the curing process of hydrogels and the resulting material characteristics before manufacturing these devices can be accomplished. In this study, we investigated the effect of curing time and sample volume on the as-cured material properties of acrylamide-based hydrogels hydrated with lithium and magnesium chloride salt solutions. Samples were cured at room temperature, 60° C and 100° C, and the resulting changes in mechanical stiffness and …

Go to article

Electron Energy Loss Spectroscopy Signal Processing Tool For Materials Research, Scott Mullen, Chang Wan Han, Volkan Ortalan Aug 2015

Electron Energy Loss Spectroscopy Signal Processing Tool For Materials Research, Scott Mullen, Chang Wan Han, Volkan Ortalan

The Summer Undergraduate Research Fellowship (SURF) Symposium

Allowing scientists to analyze materials’ structure and chemistry at an atomic level, the electron microscope has become a vital tool in materials engineering. Due to the inherent nature of signals (inelastic electrons or X-ray) having a low signal-to-noise ratio, processing the signal collected with an electron microscope is frequently required and uses sophisticated computer code. The software written to do this can be very difficult to learn and use. To make these tools more easily accessible to new users, we will create a simple user interface and host it online. Using the Rappture development tool, a menu driven graphical user …

Go to article

Exploring The Effect Of Sample Properties On Spark-Induced Breakdown Spectroscopy, Michael J. Marino, Payson Dieffenbach, Liesl A. Krause, Prasoon Diwakar, Ahmed Hassanein Aug 2015

Exploring The Effect Of Sample Properties On Spark-Induced Breakdown Spectroscopy, Michael J. Marino, Payson Dieffenbach, Liesl A. Krause, Prasoon Diwakar, Ahmed Hassanein

The Summer Undergraduate Research Fellowship (SURF) Symposium

Optical emission spectroscopy techniques such as laser-induced breakdown spectroscopy (LIBS) and spark-induced breakdown spectroscopy (SIBS) provide portable and robust methods for elemental detection in real-time. Laser-produced emissions are then used for quantitative and qualitative analysis of a sample material with applications in explosives detection. For both techniques, the main obstacles have always been signal intensity, accuracy, and sensitivity of detection. The main advantage of the SIBS method is more safe operation, while still maintaining the portability of the technique. In this study, detailed characterization of spark induced plasma, analyte emission intensity, plasma temperature, electron density, and plasma persistence has been …

Go to article

Fracture Mechanics-Based Simulation Of Pv Module Delamination, Dominic I. Jarecki, Johanna B. Palsdottir, Peter Bermel, Marisol Koslowski Aug 2015

Fracture Mechanics-Based Simulation Of Pv Module Delamination, Dominic I. Jarecki, Johanna B. Palsdottir, Peter Bermel, Marisol Koslowski

The Summer Undergraduate Research Fellowship (SURF) Symposium

Photovoltaic (PV) cells are rapidly growing as a renewable alternative to fossil fuels like coal, oil, and natural gas. However, greater adoption has also reduced government subsidies, placing the onus of making solar panels economically competitive on innovative research. While multiple methods have been considered for reducing costs, with each reduction in cost comes the associated peril of reduction in quality and useful lifetime. Several problems considered solved have now resurfaced as potential failure mechanisms with the introduction of cheaper PV cell technologies. However, to remain economically viable, PV modules will not only have to become cheaper, they will have …

Go to article

Examining The Hydration And Mechanical Properties Of Cement Paste Containing Cellulose Nanocrystals, Yvette Valadez-Carranza, Charles Y. Chiu, W. Jason Weiss, Pablo Zavattieri, Jeffrey P. Youngblood Aug 2015

Examining The Hydration And Mechanical Properties Of Cement Paste Containing Cellulose Nanocrystals, Yvette Valadez-Carranza, Charles Y. Chiu, W. Jason Weiss, Pablo Zavattieri, Jeffrey P. Youngblood

The Summer Undergraduate Research Fellowship (SURF) Symposium

Cellulose nanocrystals (CNCs) are a nano-scaled particulae material that has been shown to improve strength in cementitious pastes. One advantage of CNCs compared to other nano-materials is that CNCs are renewable and sustainable. The objective of this investigation is to investigate the influence of additional alkali content on the behavior of CNCs in cement paste. This work evaluates flexural and compressive strength as a function of heat of hydration—which measures the extent of reaction. Previous mechanical tests on cement paste containing cellulose nanocrystals (CNCs) have shown CNCs to improve the flexural strength of cement paste by approximately 30%. Isothermal calorimetry …

Go to article

Towards An Optical In-Line Characterization Of Nano Petals, Yiming Ding, Huisung Kim, Euiwon Bae Aug 2015

Towards An Optical In-Line Characterization Of Nano Petals, Yiming Ding, Huisung Kim, Euiwon Bae

The Summer Undergraduate Research Fellowship (SURF) Symposium

Carbon Nano Petals (i.e. CNPs) are cantilevered multilayer grapheme sheets that are seeded from core graphite fibers. The resulting structure offers a possibility of minimizing interfacial losses in transport application, improved interactions with surrounding matrix materials in composites, and a route toward substrate independence for device applications. The mass production of CNPs on the substrate required a method that can provide synchronous feedback on the sample status without pulling them out of the production line. Different optical properties can be observed when surfaces with different roughness are illuminated with a highly coherent light such as a laser beam. Similarly, CNPs …

Go to article

Adsorption Mechanisms Of Palladium On The Tobacco Mosaic Virus Surface, Gloriia D. Novikova, Oluwamayowa Adigun, Erin Retzlaff-Roberts, Michael T. Harris Aug 2015

Adsorption Mechanisms Of Palladium On The Tobacco Mosaic Virus Surface, Gloriia D. Novikova, Oluwamayowa Adigun, Erin Retzlaff-Roberts, Michael T. Harris

The Summer Undergraduate Research Fellowship (SURF) Symposium

Organic-inorganic materials synthesis using biological templates has recently drawn immense attention of researchers. Biotemplating has shown to be an efficient and economic means of nanomaterials production. Naturally stable, readily available and genetically malleable, Tobacco Mosaic Virus (TMV) is one of the most extensively studied and characterized biotemplates. Particularly, templated synthesis using TMV has produced high quality nanorods and nanowires that have been applied to batteries, memory devices and catalysis. The fundamental mechanisms, governing the adsorption of palladium on the TMV Wild Type and genetically modified versions (TMV1Cys and TMV2Cys), are not fully understood; this knowledge, however, is essential for future …

Go to article

Synthesis, Characterization, And Thermoelectric Properties Of Radical Siloxanes, Arnold J. Eng, Bryan Boudouris, Edward P. Tomlinson, Martha Emily Hay Aug 2015

Synthesis, Characterization, And Thermoelectric Properties Of Radical Siloxanes, Arnold J. Eng, Bryan Boudouris, Edward P. Tomlinson, Martha Emily Hay

The Summer Undergraduate Research Fellowship (SURF) Symposium

More than half of the annual energy consumption in the United States is lost as waste heat. Polymer-based thermoelectric devices have the potential to utilize this waste heat both sustainably and cost-effectively. Although conjugated polymers currently dominate research in organic thermoelectrics, the potential of using polymers with radical pendant groups have yet to be realized. These polymers have been found to be as conductive as pristine (i.e., not doped) poly(3-hexylthiophene) (P3HT), a commonly-used charge-transporting conjugated polymer. This could yield promising avenues for thermoelectric material design as radical polymers are more synthetically tunable and are hypothesized to have a high Seebeck …

Go to article

Membrane Pre-Treatment Using Chemical Disinfectants In Halide Impaired Waters, Holly M. Haflich, Kun Huang, Amisha D. Shah, John Howarter, Logan Kearney Aug 2015

Membrane Pre-Treatment Using Chemical Disinfectants In Halide Impaired Waters, Holly M. Haflich, Kun Huang, Amisha D. Shah, John Howarter, Logan Kearney

The Summer Undergraduate Research Fellowship (SURF) Symposium

The use of membrane filtration processes for desalination, water reuse, and water reclamation techniques are becoming more prevalent given freshwater shortages. However, the treatment of these waters is challenging because of the membranes used in these processes. During nanofiltration and reverse osmosis the membranes undergo biofouling. Reverse osmosis and nanofiltration are high-pressure membrane filtration techniques that treat seawater, brackish waters, and industrial wastewaters. Because of the biofouling, the polyamide thin film needs to be pretreated with chlorine (HOCl/ OCl-) as a disinfectant, but this damages the polyamide membrane. When the free chlorine is in the presence of halide-impaired waters, it …

Go to article

Thermal And Mechanical Properties Of Polymers Using Molecular Dynamics, Daniel Glass, Alejandro Strachan, Lorena Alzate-Vargas, Chunyu Li, Benjamin Haley Aug 2015

Thermal And Mechanical Properties Of Polymers Using Molecular Dynamics, Daniel Glass, Alejandro Strachan, Lorena Alzate-Vargas, Chunyu Li, Benjamin Haley

The Summer Undergraduate Research Fellowship (SURF) Symposium

Polymer systems have gained attention during the past years because of their technological and industrial applications. Simulations, particularly molecular dynamics, are very useful for exploring properties of amorphous polymers, without using experiments. Our goal is to create a readily-available tool that will perform MD simulations in order to get thermal and mechanical properties (Glass transition temperature, Young Modulus) of the polymers. The work that has been done will be part of a tool to help people to learn about polymer properties including Glass Transition Temperature. We model some polymers at a scale of 10,000 atoms. The tool uses LAMMPS to …

Go to article

Nanomechanics Simulation Toolkit - Dislocations Make Or Break Materials, Michael N. Sakano, Alejandro Strachan, David Johnson, Mitchell Wood Aug 2015

Nanomechanics Simulation Toolkit - Dislocations Make Or Break Materials, Michael N. Sakano, Alejandro Strachan, David Johnson, Mitchell Wood

The Summer Undergraduate Research Fellowship (SURF) Symposium

The goal of computational material science is to improve existing materials and design new ones through mathematical calculations. In particular, molecular dynamic simulations can allow for visualization of dislocations in a material, along with its resulting behavior when under stress. For example, plastic deformation and strain hardening result from the movement, multiplication and interaction of dislocations within the crystal structure. A simulation tool to study these phenomena was developed for the nanoHUB web resource as a part of the Network for Computational Nanotechnology at Purdue University and targets audiences ranging from undergraduate students to researchers. We created a user-friendly environment …

Go to article

Freeze-Drying Silica Based Aerogels Using Cryoprotectants And Eutectic Solvent Mixtures, Alyssa R. Bass, Shane Peng, Jeffrey Youngblood Aug 2015

Freeze-Drying Silica Based Aerogels Using Cryoprotectants And Eutectic Solvent Mixtures, Alyssa R. Bass, Shane Peng, Jeffrey Youngblood

The Summer Undergraduate Research Fellowship (SURF) Symposium

Silica based aerogels have unique properties, including good thermal insulation and convective inhibition. A sol-gel process can be used to produce semi-opaque, monolithic gels, which can then be dried to produce aerogels. Multiple drying methods are available industrially, however, these methods require high temperatures and pressures, specialized equipment, and are time consuming. This project aims to experimentally study the possibility of a new method for drying wet gels through a freeze-drying process, with the use of cryoprotectants, eutectics, and polymers to inhibit and control ice formation and growth during drying. Silica wet gels were produced using tetraethylorthosilicate (TEOS), ethanol, water, …

Go to article

Lignopolymers As Viscosity-Reducing Additives In Magnesium Oxide Suspensions, Lisa R. Murray, Chetali Gupta, Newell R. Washburn, Kendra Erk Jul 2015

Lignopolymers As Viscosity-Reducing Additives In Magnesium Oxide Suspensions, Lisa R. Murray, Chetali Gupta, Newell R. Washburn, Kendra Erk

School of Materials Engineering Faculty Publications

Lignopolymers are a new class of polymer additives with the capability to be used as dispersants in cementitious pastes. Made with kraft lignin cores and grafted polymer side- chains, the custom-synthesized lignopolymers were examined in terms of the molecular architecture for viscosity reducing potential in inert model suspensions. Lignin-poly(acrylic acid) (LPAA) and lignin-polyacrylamide (LPAm) have been found to vary the rheology of magnesium oxide (MgO) suspensions based on differences in chain architecture and particle- polymer interactions. A commercial comb-polymer polycarboxylate ester was compared to LPAA and LPAm at 2.7 mg/mL, a typical dosage for cement admixtures, as well as 0.25 …

Go to article

Near-Congruent Solidification Of Castings, Kevin J Chaput Apr 2015

Near-Congruent Solidification Of Castings, Kevin J Chaput

Open Access Dissertations

A study on the microstructure development of as-cast Cu-Mn alloys based around the congruent minimum at 34.6 wt % Mn and 873 °C was performed. Initially, this was to evaluate the alloy as an alternative to wide freezing range Pb and Sn bronzes that are plagued with porosity. The shallow minimum and associated narrow freezing ranges around the congruent point result in a completely cellular (non-dendritic) solidification morphology for a composition range ~3 wt % Mn about the congruent composition (C c). The degree of cellular solidification was found to depend on the mold material. Increased mold conductivity lead …

Go to article

Investigations Of Carbon Nanotube Catalyst Morphology And Behavior With Transmission Electron Microscopy, Sammy M. Saber Apr 2015

Investigations Of Carbon Nanotube Catalyst Morphology And Behavior With Transmission Electron Microscopy, Sammy M. Saber

Open Access Dissertations

Carbon nanotubes (CNTs) are materials with significant potential applications due to their desirable mechanical and electronic properties, which can both vary based on their structure. Electronic applications for CNTs are still few and not widely available, mainly due to the difficulty in the control of fabrication. Carbon nanotubes are grown in batches, but despite many years of research from their first discovery in 1991, there are still many unanswered questions regarding how to control the structure of CNTs. This work attempts to bridge some of the gap between question and answer by focusing on the catalyst particle used in common …

Go to article

Delamination Of C/Pekk I-Beam Using Virtual Crack Closure Technique And Cohesive Zone Method, Greeshma Ramakrishna Apr 2015

Delamination Of C/Pekk I-Beam Using Virtual Crack Closure Technique And Cohesive Zone Method, Greeshma Ramakrishna

Open Access Theses

A damage study is conducted on a carbon epoxy/PEKK (poly-ether-ketone-ketone) thermoplastic composite I-Beam, with a pre crack of 100 mm modeled between the top flange and the filler (butt joint between filler and web). This project is in collaboration with Fokker Aerostructures, Netherlands and is part of the Thermoplastic Primary Aircraft Structure innovation program (TAPAS). The C/PEKK I-Beam is modeled after a section of the Gulfstream G650 aircraft's centre beam, which was previously a carbon fiber/epoxy hat-stiffened skin construction. The objective of the thesis is to identify if the crack propagates in the I-Beam within the load range that act …

Go to article

Nanomechanical Characterization Of Thermo-Mechanical Properties Of Irradiated Zirconium With Consideration Of Temperature And Microstructure, Jonathan Thomas Marsh Apr 2015

Nanomechanical Characterization Of Thermo-Mechanical Properties Of Irradiated Zirconium With Consideration Of Temperature And Microstructure, Jonathan Thomas Marsh

Open Access Theses

Zirconium (Zr) and zirconium-alloys have been utilized in the nuclear industry for decades, most commonly in nuclear fuel cladding. The characteristics which make Zr ideal for these applications include: low density, high hardness, high ductility, and high corrosion resistance. Efforts have been made to further enhance these properties through the use of Zr-alloys, such as Zircaloy-2 and Zircaloy-4, which are made up 95-99% Zr by weight, with the remaining weight percentage being made of other metals (tin, niobium, nickel, iron, chromium). The performance of these materials directly influences the efficiency of the nuclear reactor and are thus of primary concern. …

Go to article

The Effects Of An Electric Field On The Sintering Of Ceramics, Kara E. Luitjohan Apr 2015

The Effects Of An Electric Field On The Sintering Of Ceramics, Kara E. Luitjohan

Open Access Theses

Sintering is a method used to condense a solid powder material into a single solid mass allowing for the production of metal or ceramic parts. Different sintering techniques involve the manipulation of different processing variables. To fully exploit the processing variables, how they affect the sintering process must be fully understood. One such processing variable is an applied electric field, utilized in spark plasma sintering and flash sintering. Both techniques allow for densification to occur at lower temperatures and in shorter times when compared to other sintering techniques. Though various theories exist in literature for how the electric field affects …

Go to article

Quantifying Moisture Transport In Cementitious Materials Using Neutron Radiography, Catherine L. Lucero Apr 2015

Quantifying Moisture Transport In Cementitious Materials Using Neutron Radiography, Catherine L. Lucero

Open Access Theses

A portion of the concrete pavements in the US have recently been observed to have premature joint deterioration. This damage is caused in part by the ingress of fluids, like water, salt water, or deicing salts. The ingress of these fluids can damage concrete when they freeze and expand or can react with the cementitious matrix causing damage. To determine the quality of concrete for assessing potential service life it is often necessary to measure the rate of fluid ingress, or sorptivity. Neutron imaging is a powerful method for quantifying fluid penetration since it can describe where water has penetrated, …

Go to article

Machining As A Mechanical Property Test Revisited, David L. Smith Apr 2015

Machining As A Mechanical Property Test Revisited, David L. Smith

Open Access Theses

There is much need for data on mechanical behavior of metals at high strains and strain rates. This need is dictated by modeling of processes like forming and machining, wherein the material in the deformation zone is subjected to severe deformation conditions atypical of conventional material property tests such as tension and torsion. Accurate flow stress data is an essential input for robust prediction of process outputs. Similar requirements arise from applications in high speed ballistic penetration and design of materials for armor. Since the deformation zone in cutting of metals is characterized by unique and extreme combinations of strain, …

Go to article

Failure Analysis Of High Performance Ballistic Fibers, Jennifer S. Spatola Apr 2015

Failure Analysis Of High Performance Ballistic Fibers, Jennifer S. Spatola

Open Access Theses

High performance fibers have a high tensile strength and modulus, good wear resistance, and a low density, making them ideal for applications in ballistic impact resistance, such as body armor. However, the observed ballistic performance of these fibers is much lower than the predicted values. Since the predictions assume only tensile stress failure, it is safe to assume that the stress state is affecting fiber performance. The purpose of this research was to determine if there are failure mode changes in the fiber fracture when transversely loaded by indenters of different shapes. An experimental design mimicking transverse impact was used …

Go to article

Dielectric Coating Of Iron Particles By Electrostatic Colloidal Deposition, Daniel Kim Apr 2015

Dielectric Coating Of Iron Particles By Electrostatic Colloidal Deposition, Daniel Kim

Open Access Theses

Iron is a soft magnetic material widely used in electric motors, generators, and transformers because they demand high permeability and low core loss. The main goal of this project is to develop a commercially viable coating of iron powders for press-and-sinter processing that would enable higher firing temperatures to anneal out magnetic defects, while maintaining high electrical resistivity (∼10,000 μΩ-cm) and high iron density (>90 %). An alumina-modified colloidal silica (LUDOX CL), was used in early work to make Fe (-)/SiO2 (+) in a wet-pressed route. The highest relative density and resistivity measurements for a wet-pressing route were …

Go to article

First Prev Next Last