Mechanical Engineering Commons^™

Development Of A Two-Fluid Drag Law For Clustered Particles Using Direct Numerical Simulation And Validation Through Experiments, Ahmadreza Abbasi Baharanchi

FIU Electronic Theses and Dissertations

This dissertation focused on development and utilization of numerical and experimental approaches to improve the CFD modeling of fluidization flow of cohesive micron size particles. The specific objectives of this research were: (1) Developing a cluster prediction mechanism applicable to Two-Fluid Modeling (TFM) of gas-solid systems (2) Developing more accurate drag models for Two-Fluid Modeling (TFM) of gas-solid fluidization flow with the presence of cohesive interparticle forces (3) using the developed model to explore the improvement of accuracy of TFM in simulation of fluidization flow of cohesive powders (4) Understanding the causes and influential factor which led to improvements and …

Using Controlled Curing In A Custom Stereolithography-Based 3d Printing Machine To Obtain Graded Property Variations, Evan S. Schwahn

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

In an effort to construct materially graded parts, a strategy was studied that is based on varying ratios of interpenetrating polymer networks (IPNs) in a manner that can be adapted to 3D printing. Using IPNs has the benefit of allowing access to a broad range of property variation. The strategy used involves controlled partial curing of the first network, followed by washing of that network to remove uncured components, then swelling of the structure with a second polymer component and curing.

This method was utilized to control final IPN properties by controlling the extent of crosslinking of the initial network, …

In-Vivo Corrosion And Fretting Of Modular Ti-6al-4v/Co-Cr-Mo Hip Prostheses: The Influence Of Microstructure And Design Parameters, Jose Luis Gonzalez Jr

FIU Electronic Theses and Dissertations

The purpose of this study was to evaluate the incidence of corrosion and fretting in 48 retrieved titanium-6aluminum-4vanadium and/or cobalt-chromium-molybdenum modular total hip prosthesis with respect to alloy material microstructure and design parameters. The results revealed vastly different performance results for the wide array of microstructures examined. Severe corrosion/fretting was seen in 100% of as-cast, 24% of low carbon wrought, 9% of high carbon wrought and 5% of solution heat treated cobalt-chrome. Severe corrosion/fretting was observed in 60% of Ti-6Al-4V components. Design features which allow for fluid entry and stagnation, amplification of contact pressure and/or increased micromotion were also shown …

Acoustic Manipulation And Alignment Of Particles For Applications In Separation, Micro-Templating, And Device Fabrication, Kamran Moradi

FIU Electronic Theses and Dissertations

This dissertation studies the manipulation of particles using acoustic stimulation for applications in microfluidics and templating of devices. The term particle is used here to denote any solid, liquid or gaseous material that has properties, which are distinct from the fluid in which it is suspended. Manipulation means to take over the movements of the particles and to position them in specified locations.

Using devices, microfabricated out of silicon, the behavior of particles under the acoustic stimulation was studied with the main purpose of aligning the particles at either low-pressure zones, known as the nodes or high-pressure zones, known as …

La0.7Sr0.3Fe0.7Ga0.3O3-Δ As Electrode Material For A Symmetrical Solid Oxide Fuel Cell, Zhibin Yang, Yu Chen, Chao Jin, Guoliang Xiao, Minfang Han, Fanglin Chen

Faculty Publications

In this research, La_0.7Sr_0.3Fe_0.7Ga_0.3O_3−δ (LSFG) perovskite oxide was successfully prepared using a microwave-assisted combustion method, and employed as both anode and cathode in symmetrical solid oxide fuel cells. A maximum power density of 489 mW cm⁻² was achieved at 800 °C with wet H₂ as the fuel and ambient air as the oxidant in a single cell with the configuration LSFG|La_0.8Sr_0.2Ga_0.83Mg_0.17O_3−δ|LSFG. Furthermore, the cells demonstrated good stability in H₂ and acceptable sulfur tolerance.

La0.6Sr1.4Mno4+Δ Layered Perovskite Oxide: Enhanced Catalytic Activity For The Oxygen Reduction Reaction, Yarong Wang, Zhibin Yang, Fanliang Liu, Chao Jin, Jiao Wu, Ming Shen, Ruizhi Yang, Fanglin Chen

Faculty Publications

Efficient electrocatalysts for the oxygen reduction reaction (ORR) is a critical factor to influence the performance of lithium–oxygen batteries. In this study, La_0.6Sr_1.4MnO_4+δ layered perovskite oxide as a highly active electrocatalyst for the ORR has been prepared, and a carbon-coating layer with thickness <5 nm has been successfully introduced to enhance the electronic conductivity of the as-prepared oxide. XRD, XPS, Raman, SEM and TEM measurements were carried out to characterize the crystalline structure and morphology of these samples. Rotating ring-disk electrode (RRDE) technique has been used to study catalytic activities of the as-prepared catalysts for the ORR in 0.1 M KOH media. RRDE results reveal that carbon-coated La_0.6Sr_1.4MnO_4+δ exhibits better catalytic activity for the ORR. For the carbon-coated La_0.6Sr_1.4MnO_4+δ, the ORR proceeds predominately via a direct four electron process, and a maximum cathodic current density of 6.70 mA cm⁻² at 2500 rpm has been obtained, …

Stabilizing Electrochemical Carbon Capture Membrane With Al2O3 Thin-Film Overcoating Synthesized By Chemical Vapor Deposition, Jingjing Tong, Fengzhan Si, Lingling Zhang, Jie Fang, Minfang Han, Kevin Huang

Faculty Publications

Development of high-efficiency and cost-effective carbon capture technology is a central element of our effort to battle the global warming and climate change. Here we report that the unique high-flux and high-selectivity of electrochemical silver-carbonate dual-phase membranes can be retained for an extended period of operation by overcoating the surfaces of porous silver matrix with a uniform layer of Al₂O₃ thin-film derived from chemical vapor deposition.

Influence Of Spatial Variations Of Railroad Track Stiffness And Material Inclusions On Fatigue Life, Celestin Nkundineza

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Railroad transportation is very important for economic growth and effective maintenance is one critical factor for its economic sustainability. The high repetitive forces from a moving railcar induce cyclic stresses that lead to rail bending and potential deterioration due to fatigue crack initiation and propagation. Previous research for prediction of fatigue life has been done under the assumptions of a uniform track bed and a homogeneous rail. However the spatial variation of the track stiffness is expected to increase the maximum stresses in the rail and, therefore, accelerate the fatigue process. The research described in this dissertation is focused on …