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

Engineering Commons

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

Articles 1 - 15 of 15

Full-Text Articles in Engineering

Morphology And Electric Potential-Induced Mechanical Behavior Of Metallic Porous Nanostructures, Sunghan Kim, Andreas A. Polycarpou, Hong Liang Oct 2020

Morphology And Electric Potential-Induced Mechanical Behavior Of Metallic Porous Nanostructures, Sunghan Kim, Andreas A. Polycarpou, Hong Liang

Friction

Understanding mechanical behaviors influenced by electric potential and tribological contacts is important for verifying the robustness and reliability of applications based on metallic porous nanostructures in electrical stimulations. In this work, nickel-based metallic porous nanostructures were studied to characterize their mechanical properties and morphologically dependent contact areas during application of an electric potential using a nanoindenter. We observed that the indentation moduli of nickel-based metallic porous nanostructures were altered by pore size and application of electric potential. In addition, the structural aspects of the surface morphology of nickel-based porous nanostructures had a critical effect on the determination of contact area ...


Hydrophobic, Mechanical, And Tribological Properties Of Fluorine Incorporated Hydrogenated Fullerene-Like Carbon Films, Li Qiang, Bin Zhang, Kaixiong Gao, Zhenbin Gong, Junyan Zhang Oct 2020

Hydrophobic, Mechanical, And Tribological Properties Of Fluorine Incorporated Hydrogenated Fullerene-Like Carbon Films, Li Qiang, Bin Zhang, Kaixiong Gao, Zhenbin Gong, Junyan Zhang

Friction

Fluorine-incorporated hydrogenated fullerene-like nanostructure amorphous carbon films (F-FLC) were synthesized by employing the direct current plasma enhanced chemical vapor deposition (dc-PECVD) technique using a mixture of methane (CH4), tetra-fluoromethane (CF4), and hydrogen (H2) as the working gases. The effect of the fluorine content on the bonding structure, surface roughness, hydrophobic, mechanical, and tribological properties of the films was systematically investigated using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman analysis, atomic force microscope (AFM), contact angle goniometer, nano-indenter, and reciprocating ball-on-disc tester, respectively. The fluorine content in the films increased from 0 to 2.1 ...


Predicting The Mechanical Properties Of Nanocomposites Reinforced With 1-D, 2-D And 3-D Nanomaterials, Scott Edward Muller May 2019

Predicting The Mechanical Properties Of Nanocomposites Reinforced With 1-D, 2-D And 3-D Nanomaterials, Scott Edward Muller

Theses and Dissertations

Materials with features at the nanoscale can provide unique mechanical properties and increased functionality when included as part of a nanocomposite. This dissertation utilizes computational methods at multiple scales, including molecular dynamics (MD) and density functional theory (DFT), and the coupled atomistic and discrete dislocation multiscale method (CADD), to predict the mechanical properties of nanocomposites possessing nanomaterials that are either 1-D (carbyne chains), 2-D (graphene sheets), or 3-D (Al/amorphous-Si core-shell nanorod).

The MD method is used to model Ni-graphene nanocomposites. The strength of a Ni-graphene nanocomposite is found to improve by increasing the gap between the graphene sheet and ...


Mechanical Characterizations Of 3d-Printed Plla/Steel Particle Composites, Hozhabr Mozafari, Pengfei Dong, Haitham Hadidi, Michael P. Sealy, Linxia Gu Jan 2019

Mechanical Characterizations Of 3d-Printed Plla/Steel Particle Composites, Hozhabr Mozafari, Pengfei Dong, Haitham Hadidi, Michael P. Sealy, Linxia Gu

Mechanical & Materials Engineering Faculty Publications

The objective of this study is to characterize the micromechanical properties of poly-L-lactic acid (PLLA) composites reinforced by grade 420 stainless steel (SS) particles with a specific focus on the interphase properties. The specimens were manufactured using 3D printing techniques due to its many benefits, including high accuracy, cost effectiveness and customized geometry. The adopted fused filament fabrication resulted in a thin interphase layer with an average thickness of 3 μm. The mechanical properties of each phase, as well as the interphase, were characterized by nanoindentation tests. The effect of matrix degradation, i.e., imperfect bonding, on the elastic modulus ...


Fabrication Of Highly Dense Isotropic Nd-Fe-B Nylon Bonded Magnets Via Extrusion-Based Additive Manufacturing, Ling Li, Kodey Jones, Brian Sales, Jason L. Pries, I. C. Nlebedim, Ke Jin, Hongbin Bei, Brian K. Post, Michael S. Kesler, Orlando Rios, Vlastimil Kunc, Robert Fredette, John Ormerod, Aaron Williams, Thomas A. Lograsso, M. Parans Paranthaman May 2018

Fabrication Of Highly Dense Isotropic Nd-Fe-B Nylon Bonded Magnets Via Extrusion-Based Additive Manufacturing, Ling Li, Kodey Jones, Brian Sales, Jason L. Pries, I. C. Nlebedim, Ke Jin, Hongbin Bei, Brian K. Post, Michael S. Kesler, Orlando Rios, Vlastimil Kunc, Robert Fredette, John Ormerod, Aaron Williams, Thomas A. Lograsso, M. Parans Paranthaman

Materials Science and Engineering Publications

Magnetically isotropic bonded magnets with a high loading fraction of 70 vol.% Nd-Fe-B are fabricated via an extrusion-based additive manufacturing, or 3D printing system that enables rapid production of large parts. The density of the printed magnet is ∼ 5.2 g/cm3. The room temperature magnetic properties are: intrinsic coercivity Hci  = 8.9 kOe (708.2 kA/m), remanence Br  = 5.8 kG (0.58 T), and energy product (BH)max = 7.3 MGOe (58.1 kJ/m3). The as-printed magnets are then coated with two types of polymers, both of which improve the thermal stability as revealed by flux ...


Characterization Of 3d Printed Polylactic Acid/ Polycaprolactone/Titanium Dioxide Composites For Bone Replacement And Grafting, Sandra Elena Najera Beltran Jan 2018

Characterization Of 3d Printed Polylactic Acid/ Polycaprolactone/Titanium Dioxide Composites For Bone Replacement And Grafting, Sandra Elena Najera Beltran

Open Access Theses & Dissertations

A material that mimics the properties of bones was developed by optimizing the ratio of polymer composites of polylactic acid (PLA) and poly-ε-caprolactone (PCL), containing small amounts of titanium oxide (TiO2). Although titanium-based alloys have commonly been used for bone replacement procedures due to their biocompatibility with the human body and their mechanical properties, stress shielding continues to be a problem. The structure of a bone has a porosity which permits the flow of nutrients, blood, oxygen and minerals, and is an issue at the time of creating bone replacements using conventional methods. PLA and PCL have been used in ...


Multi-Principal Element Alloys: Design, Properties And Heuristic Explorations, Aayush Sharma Jan 2018

Multi-Principal Element Alloys: Design, Properties And Heuristic Explorations, Aayush Sharma

Graduate Theses and Dissertations

Computational investigations of structural, chemical, and deformation behavior in high entropy alloys (HEAs), which possess notable mechanical strength, have been limited due to the absence of applicable force fields. First by employing Lennard-Jones (LJ) type potential, we explore the atomic origins of the structural phase transformations (PTs) in AlxCrCoFeNi multi-principal element alloys (MPEAs) using classical molecular dynamics (MD) simulations. We report that the amorphous phase exists above the melting temperatures of the participating elements when the concentration of Al 20 %, while for Al > 20 %, a gradual molten-amorphous phase transition is noted. To extend investigations for mechanical properties, we propose a ...


Ultrasonic And Magnetic Barkhausen Emission Measurements For Characterization Of Pipeline Steels, Brady J. Engle, Lucinda J. Smart, Leonard J. Bond Jan 2016

Ultrasonic And Magnetic Barkhausen Emission Measurements For Characterization Of Pipeline Steels, Brady J. Engle, Lucinda J. Smart, Leonard J. Bond

Aerospace Engineering Conference Papers, Presentations and Posters

To ensure that the aging pipeline infrastructure in the USA can be safely operated, the mechanical properties of the pipe materials must be verified. It is hypothesized that characterization of the pipeline steels and their microstructures through nondestructive methods will allow for the estimation of the mechanical properties of interest, namely yield strength, tensile strength, toughness, and ductile-to-brittle transition temperature. This work will discuss how material properties, such as microstructure and chemical composition, affect the mechanical properties as well as strategies for measuring the material properties nondestructively using magnetic Barkhausen emission and ultrasonic velocity and attenuation measurements. Preliminary results on ...


Thermal Shock Studies On Carbon-Carbon Composites: Experimentation And Analysis, Alma Lucia Leanos Jan 2015

Thermal Shock Studies On Carbon-Carbon Composites: Experimentation And Analysis, Alma Lucia Leanos

Open Access Theses & Dissertations

The oxidation behavior of C/C composites under thermal shock conditions in air is understood and predicted experimentally and by computational efforts. In Chapter. 1, both compressive properties and oxidation behavior of pristine and thermal shock exposed 2D C/C composite specimens were examined. Pristine test specimens were exposed to thermal shock conditions with temperatures ranging from 400°C to 1000°C in an oxidizing environment, followed by compression tests on pristine and thermal shock exposed specimens to obtain their compressive responses.

Similarly, in Chapter. 2, the influence of thermal shock conditions on both, the extent of carbon materials decomposition ...


Role Of Interphase In The Mechanical Behavior Of Silica/Epoxy Resin Nanocomposites, Yi Hua, Linxia Gu, Sundaralingam Premaraj, Xiaodong Zhang Jan 2015

Role Of Interphase In The Mechanical Behavior Of Silica/Epoxy Resin Nanocomposites, Yi Hua, Linxia Gu, Sundaralingam Premaraj, Xiaodong Zhang

Mechanical & Materials Engineering Faculty Publications

A nanoscale representative volume element has been developed to investigate the effect of interphase geometry and property on the mechanical behavior of silica/epoxy resin nanocomposites. The role of interphase–matrix bonding was also examined. Results suggested that interphase modulus and interfacial bonding conditions had significant influence on the effective stiffness of nanocomposites, while its sensitivities with respect to both the thickness and the gradient property of the interphase was minimal. The stiffer interphase demonstrated a higher load-sharing capacity, which also increased the stress distribution uniformity within the resin nanocomposites. Under the condition of imperfect interfacial bonding, the effective stiffness ...


Single Fiber Mechanical Properties Using Nano-Tensile Testing And Carbon Fiber Structure-Property Relationship, Matthew Erich Kant Dec 2014

Single Fiber Mechanical Properties Using Nano-Tensile Testing And Carbon Fiber Structure-Property Relationship, Matthew Erich Kant

Doctoral Dissertations

Single carbon fibers are studied using a nano-tensile testing system. This system has unprecedented load and displacement resolution, nN and nm respectively, and the ability to perform dynamic testing for storage and loss modulus during quasi-static tensile extension. Furthermore, improved fiber mounting and alignment procedures coupled with the precision of the nano-tensile testing system assist in unprecedented resolution in single fiber mechanical testing for axial modulus and strength. Hence, using these unique capabilities, the moduli and their statistical distribution of many high performance carbon fibers are reported here. From this, a simplified single parameter model describing the strain dependent modulus ...


Polyurethane Films, Foams And Nanocomposites Prepared From Vegetable Oil-Based Polyols, Chaoqun Zhang Jan 2014

Polyurethane Films, Foams And Nanocomposites Prepared From Vegetable Oil-Based Polyols, Chaoqun Zhang

Graduate Theses and Dissertations

ABSTRACT

Polyurethanes (PUs) have been widely used in coatings, adhesives, sealants, and foams. Historically, the raw materials of a PU, polyol and isocyanate, were derived from petroleum. Nowadays, the increasing concerns regarding the depletion of petroleum resources and environmental problems caused by fossil fuels, has triggered great interest in the development of monomers based on renewable resources for PU production. In this project, a novel solvent-free/catalyst-free method was developed to prepare polyols from epoxidized soybean oil and castor oil for PU production. The effects of reaction temperature, reaction time, and reaction ratios of carboxyl acid and epoxy groups on ...


Nanoparticle-Shelled Bubbles For Lightweight Materials, Teresa Brugarolas Brufau Jan 2014

Nanoparticle-Shelled Bubbles For Lightweight Materials, Teresa Brugarolas Brufau

Publicly Accessible Penn Dissertations

Lightweight materials that are mechanically robust are of great interest in automotive, aerospace, and construction industries. However due to the nature of materials, it is challenging to obtain materials that have high strength, stiffness and toughness, and light weight simultaneously. One approach that tries to address this limitation is the use of composite materials containing hollow microparticles, also known as syntactic foams. The incorporation of hollow microparticles decreases the density of the material at the same time that increases its specific strength. Conventional methods of fabrication of hollow particles involving bulk reactions result in high heterogeneity in geometry as well ...


Study Of Mechanical And Thermal Properties Of Soy Flour Elastomers, Kendra Allen Jan 2014

Study Of Mechanical And Thermal Properties Of Soy Flour Elastomers, Kendra Allen

Graduate Theses and Dissertations

Bio-based plastics are becoming viable alternatives to petroleum-based plastics because they decrease dependence on petroleum derivatives and are more environmentally friendly. Raw materials such as soy flour are widely available, low cost, lightweight, stiffness and have high strength characteristics, but weak interfacial adhesion between the soy flour and the polymer poses a challenge. In this study, soy flour was utilized as a filler in thermoplastic elastomer composites. A surface modification called acetylation was investigated at soy flour concentrations of 10 wt%, 15 wt% and 20 wt%. The mechanical properties of the composites were then compared to that of elastomers without ...


The Electronic And Mechanical Properties Of The Xyb14 Complex Borides Studied By First-Principles Methods, Liwen Wan Jan 2013

The Electronic And Mechanical Properties Of The Xyb14 Complex Borides Studied By First-Principles Methods, Liwen Wan

Graduate Theses and Dissertations

Intensive scientific efforts have been invested in searching and designing new superhard materials for applications as abrasives, polishing and cutting tools, wear-resistant and protective coatings. The best-known superhard material to date is diamond. However, its industrial applications are greatly limited by its high cost and susceptibility to chemical corrosion. Alternatively, boron compounds are promising candidates because of boron's hardness and excellent chemical and thermal stability.

Conventional superhard materials, such as diamond and cubic boron nitride, are usually comprised of a strong, covalently bonded network of atoms. This bonding usually results in a dense, highly symmetric crystal structure that is ...