Mechanical Engineering Commons^™

Modeling The Impact Of Battery Degradation Within Lifecycle Cost Based Design Optimization Of Heavy-Duty Hybrid Electric Vehicles, Ashish P. Vora

Open Access Dissertations

The optimal design of hybrid electric vehicle (HEV) powertrains from a systems perspective is critical to realize the maximum benefits for a given application. This is particularly true in the heavy-duty vehicle space where the major challenges are: (i) greater emphasis on economic viability, (ii) reluctance to take on risk associated with new technologies, and (iii) numerous diverse applications that preclude a one-size-fits-all approach to hybrid-electric powertrain design. Past studies on HEV powertrain design have either ignored battery degradation, or failed to holistically capture its impact from a lifecycle cost perspective. The focus of this effort is the development of …

Ultra-Thin Boron Nitride Films By Pulsed Laser Deposition: Plasma Diagnostics, Synthesis, And Device Transport, Nicholas Robert Glavin

Open Access Dissertations

This work describes, for the first time, a pulsed laser deposition (PLD) technique for growth of large area, stoichiometric ultra-thin hexagonal and amorphous boron nitride for next generation 2D material electronics. The growth of boron nitride, in this case, is driven by the high kinetic energies and chemical reactivities of the condensing species formed from physical vapor deposition (PVD) processes, which can facilitate growth over large areas and at reduced substrate temperatures. The use of optical emission spectroscopy during plasma growth provides insight into chemistry, kinetic energies, time of flight data, and spatial distributions within a PVD plasma plume ablated …

Preliminary Design Tools In Turbomachinery: Non-Uniformly Spaced Blade Rows, Multistage Interaction, Unsteady Radial Waves, And Propeller Horizontal-Axis Turbine Optimization, Yujun Leng

Open Access Dissertations

Turbomachinery flow fields are inherently unsteady and complex which makes the related CFD analyses computationally intensive. Physically based preliminary design tools are desirable for parametric studies early in the design stage, and to provide deep physical insight and a good starting point for the later CFD analyses. Four analytical/semi-analytical models are developed in this study: 1) a generalized flat plate cascade model for investigating the unsteady aerodynamics of a blade row with non-uniformly spaced blades; 2) a multistage interaction model for investigating rotor-stator interactions; 3) an analytical solution for quantifying the impeller wake convection and pressure wave propagating between a …

Multi-Axial Failure Of High-Performance Fiber During Transverse Impact, Matthew C. Hudspeth

Open Access Dissertations

The effect of projectile nose geometry on ensuing wave development in high-performance yarns is explored during single yarn transverse impact. Special attention has been placed on visualizing the immediate region around the projectile-yarn contact site for 0.30-cal round, 0.30-cal fragment simulation projectiles (FSP), and razor blades using high-speed imaging. Kevlar® KM2, Dyneema®SK76 and AuTx have been impacted at velocities ranging from ∼100 m/s to ∼1200 m/s depending on projectile nose shape, with an emphasis set on determining the critical velocity wherein below said velocity significant development of wave propagation occurs and above said velocity the yarn fails immediately upon impact. …

Characterization Of Pool Boiling Heat Transfer From Porous-Coating-Enhanced Surfaces, Suchismita Sarangi

Open Access Dissertations

Development of techniques for enhancement and optimization of thermal management technologies has been a highly active area of research in recent decades in response to the rapid emergence of compact, high-power electronic systems. Immersion cooling by boiling is one of the preferred methods for high power density applications, due to its passive nature and high heat transfer coefficients obtained. Pool boiling heat transfer has been extensively studied in recent decades to understand the inherent mechanisms yielding the high heat transfer rates, as well as to further enhance the heat transfer by simple modifications or additions to existing approaches. This thesis …

Analytical And Experimental Investigation Of Microstructural Alterations In Bearing Steel In Rolling Contact Fatigue, Sina Mobasher Moghaddam

Open Access Dissertations

Rolling Contact Fatigue (RCF) is one the most common failure modes in bearings. RCF is usually associated with particular microstructural alterations. Such alterations (i.e. white etching cracks, butterflies, etc.) which lead to RCF failure are known to be among the most concerning matters to bearing industry.

In the current work, an analytical as well as experimental approaches are used to investigate “butterfly wing” formation, crack initiation and propagation from inclusions. A new damage evolution equation coupled with a FE model is employed to account for the effect of mean stresses and alternating stresses simultaneously to investigate butterfly formation. The proposed …

Analytical Investigation Of Fretting Wear With Special Emphasis On Stress Based Models, Arnab Jyoti Ghosh

Open Access Dissertations

Fretting refers to the minute oscillatory motion between two surfaces in contact under an applied normal load. It can cause either surface or subsurface initiated failure resulting in either fatigue or wear or both. Two distinct regimes – partial slip and gross slip are typically observed in fretting contacts. Due to the nature of contact, various factors such as wear debris, oxidation, surface roughness, humidity etc. effect failures caused due to fretting. A number of different techniques have been developed to quantify fretting damage and several numerical models are proposed to predict damage due to fretting. Fretting wear also depends …

A Study On Flow Development In An Apu-Style Inlet And Its Effect On Centrifugal Compressor Performance, Fangyuan Lou

Open Access Dissertations

The objectives of this research were to investigate the flow development inside an APU-style inlet and its effect on centrifugal compressor performance. The motivation arises from the increased applications of gas turbine engines installed with APU-style inlets such as unmanned aerial vehicles, auxiliary power units, and helicopters. The inlet swirl distortion created from these complicated inlet systems has become a major performance and operability concern. To improve the integration between the APU-style inlet and gas turbine engines, better understanding of the flow field in the APU-style inlet and its effect on gas turbine is necessary.

A research facility for the …

Analysis And Simulation Of Small Scale Microwave Interferometer Experiments On Non-Ideal Explosives, David E. Kittell

Open Access Dissertations

Small scale experiments for non-ideal and homemade explosives (HMEs) were investigated, analyzed, and subsequently modeled in an attempt to develop more predictive capabilities for the threat assessment of improvised explosive devices (IEDs), as well as to provide new analysis capabilities for other investigators in the field. Non-ideal explosives and HMEs are challenging to characterize because of the nearly limitless parameter space (e.g. sample composition, density, particle morphology, etc.) which gives rise to a broad range of explosive sensitivity and performance. Large scale tests, such as rate stick and gap tests, are not feasible for characterizing every HME of interest due …

Semiconductor Nanomaterial Development For Photovoltaic And Thermoelectric Applications, Liangliang Chen

Open Access Dissertations

Today's world is frequently going through fossil energy shortage and environmental consequences brought by the over-emission of greenhouse gas from burning fossil fuels. Therefore, it is urgent now more than ever to discover or develop clean and sustainable power generation approaches. Among various approaches, photovoltaics and thermoelectrics have been more and more attentive both in academia and industry. Photovoltaic power generators can significantly decrease carbon dioxide emission by directly converting sunlight into electricity, and thermoelectric power generators can increase energy use efficiency by recycling waste heat into electricity. This research seeks to gain a better understanding of the mechanism that …

Mechanisms Of Microstructure Formation Under The Influence Of Ultrasonic Vibrations, Milan Rakita

Open Access Dissertations

Positive effects of ultrasound on crystallization have been known for almost 90 years. Application of ultrasound has been very successful in many industries, most notably in chemistry, creating a new branch of science - sonochemistry. However, ultrasonication has not found wide commercial application in the solidification processing. The reason for that is the complexity of underlying phenomena and the lack of predicting models which correlate processing parameters with the properties of a product. The purpose of this study is to give some contribution toward better understanding of mechanisms that lead to changes in the solidifying microstructure. It has been found …

A Novel Fluid Structure Interaction And Thermal Model To Predict The Cylinder Block / Valve Plate Interface Performance In Swash Plate Type Axial Piston Machines, Marco Zecchi

Open Access Dissertations

The cylinder block / valve plate interface represents one of the most critical design element in the rotating kit of axial piston machines. The thin film of lubricant between cylinder block and valve plate has to fulfill simultaneously a bearing and a sealing function under dynamic load conditions; on the other hand, it represents an important source of power losses due to viscous friction and leakage flow.

An accurate prediction of the time changing characteristics of the interface, in terms of fluid film thickness, dynamic pressure field, load carrying ability and energy dissipation is necessary to generate more efficient and …

Near-Field Pressure Distributions To Enhance Sound Transmission Into Multi-Layer Materials, Andrew Martin Jessop

Open Access Dissertations

The large impedance difference between air and most solids prevents significant energy transfer from incident acoustic waves across the air-material interface. Refraction also plays a role in preventing acoustic transmission, as the wave speed difference between air and solid materials results in an increase of the resulting propagation angles, creating near-field pressure distributions in the solid material. By utilizing evanescent pressure distributions, which decay normal to the usual direction of propagation and are represented as plane waves propagating with complex angles, energy propagation through the interface can be increased in the subsonic region of wave propagation: i.e., where waves typically …

Fault Detection And Diagnosis For Air Conditioners And Heat Pumps Based On Virtual Sensors, Woohyun Kim

Open Access Dissertations

The primary goal of this research is to develop and demonstrate an integrated, on-line performance monitoring and diagnostic system with low cost sensors for air conditioning and heat pump equipment. Automated fault detection and diagnostics (FDD) has the potential for improving energy efficiency along with reducing service costs and comfort complaints. To achieve this goal, virtual sensors with low cost measurements and simple models were developed to estimate quantities that would be expensive and or difficult to measure directly.

A virtual refrigerant charge sensor (VRC) was extended with three approaches for determining refrigerant charge for equipment having variable-speed compressors and …

Scalable Autonomous Operations Of Unmanned Assets, Sunghun Jung

Open Access Dissertations

Although there have been great theoretical advances in the region of Unmanned Aerial Vehicle (UAV) autonomy, applications of those theories into real world are still hesitated due to unexpected disturbances. Most of UAVs which are currently used are mainly, strictly speaking, Remotely Piloted Vehicles (RPA) since most works related with the flight control, sensor data analysis, and decision makings are done by human operators. To increase the degree of autonomy, many researches are focused on developing Unmanned Autonomous Aerial Vehicle (UAAV) which can takeoff, fly to the interested area by avoiding unexpected obstacles, perform various missions with decision makings, come …

Identification And Quantification Of Nonlinear Behavior In A Disbonded Aluminum Honeycomb Panel Using Single Degree-Of-Freedom Models, Eric Richard Dittman

Open Access Dissertations

There is not a complete understanding of how damage mechanisms in composite materials react to nondestructive testing inputs. A deeper understanding of composite damage mechanisms and their responses to external vibratory excitation is sought using nonlinear modeling of damping and stiffness characteristics related to the damage. Different types of damping and stiffness single degree-of-freedom models are presented with analysis of their behavior at specific harmonics of the primary resonance of the system. After an understanding of the approximate behaviors of the models is obtained, experimental tests on a damaged specimen are conducted. An aluminum honeycomb sandwich panel is damaged by …