Mechanical Engineering Commons^™

Characterization Of Thermal And Mechanical Properties Of Porous Material For Electronic Cooling Applications, Ninad Tushar Trifale

Open Access Theses

Metal foams are considered beneficial for several applications because of its significantly large surface area for a given volume. Foams form a high thermal conductive network in a thermal interface for electro cooling applications. The porous structures are relatively compliant and can provide for a better contact and thereby have a lower thermal resistance. Porous heat sinks made of aluminum foam have been well studied in the past. It is not only cost effective due to the unique production process, but also attractive for the theoretical modeling study to determine the performance. A study on the thermal and mechanical characterization …

The Influence Of Gaps On The Frequency Response Of A Beamspring Contact System, Wenbin Zhang

Open Access Theses

Some mechanical systems with gaps such as in disc brakes and Cardan joints exhibit nonlinearity under certain load conditions, which is unpredictable and highly sensitive to initial conditions. Previous studies were mainly focused on either a single-degree-of-freedom (DOF) system or a flexible beam with uniform elastic foundation. The analysis of this thesis is a combination of these two where gaps are first introduced to a flexible beam model. A model of a beam resting on compliant foundation with gaps has been developed and analyzed. The assumed modes method is used to derive the equations of motion (EOM's) for the system. …

An Algorithm For Impacting Soft Structures, Tengfei Long

Open Access Theses

Impact among soft structures is often difficult to model because of the geometrical non-linearity involved. There are a number of previous studies of the contact dynamics of rigid bodies, but few has focused on soft structures so far.

This thesis models impact between soft structures without any restraint on their geometries. The goal is to simulate the dynamics involved among soft structures during an impact process. This has been done through designing and implementing an contact algorithm that uses the finite element method along with a three-dimensional solid element to solve the fundamental time integration problem. Modeling of the contact …

Exhaust Thermal Management Using Cylinder Deactivation And Late Intake Valve Closing, Mark E. Magee

Open Access Theses

Progressively stricter emission regulations have compelled diesel engine manufacturers to develop new technologies that reduce harmful pollutants like NOx and soot. While manufacturers have previously been able to meet these regulations through the use of on engine technology such as exhaust gas recirculation and multiple pulse injections, exhaust after treatment systems such as diesel particulate filters and selective catalytic reduction systems have become necessary to meet recent stricter policies. While these after treatment systems are incredibly effective at reducing harmful emissions, to operate effectively the system needs to be above a certain temperature level typically between 250 and 300°C. Many …

Improving Indoor Air Quality Through Botanical Air Filtration In Energy Efficient Residences, Daniel William Newkirk

Open Access Theses

According to the U.S. EPA, the average American spends 90% of their time indoors where pollutants are two to five times more prevalent than outside. The consequences of these pollutants are estimated to cost the U.S. 125 billion dollars in lost health and productivity. Background literature suggests botanical air filtration may be able to solve this problem by leveraging the natural ability of plants to purify indoor air. By improving indoor air quality, energy consumption can also be reduced by bringing in less outside air to dilute contaminants within the space. A botanical air filter, called the Biowall, was designed …

Study Of Aluminum Honeycomb Sandwich Composite Structure For Increased Specific Damping, Aditi S. Joshi

Open Access Theses

The aluminum honeycomb sandwich composite structure is commonly used in the aerospace and automotive applications where high strength to weight ratio is desirable. However the poor performance of the aluminum honeycomb sandwich composite structure in terms of the vibration damping and the sound transmission makes their applications limited. Studying the effect of different structural modifications on the damping has become an interesting area of research in past few decades. The present study addresses the effect of adding a mass on the composite beam at various locations on the damping loss factors for the modes of vibration present in the frequency …

Experimental Investigation Of A Forced Response Condition In A Multistage Compressor, William Louis Murray

Open Access Theses

The objective of this research is twofold. Firstly, the design, development, and construction of a test facility for a Honeywell APU-style centrifugal compressor was implemented, as well as the design and construction of an inlet flow experiment. Secondly, the aeromechanical response of an embedded stage in the Purdue 3-Stage axial research compressor was analyzed through a suite of different measurement techniques in the fulfillment of the end of the GUIde IV Consortium contract. ^ The purpose of the first phase of Honeywell work was to comprehensively measure the flow field of an APU-style centrifugal compressor inlet through the use of …

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 …

A Novel Multiblock Immersed Boundary Method Enabling High Order Large Eddy Simulation Of Pathological And Medical Device Hemodynamics, Anupindi Kameswararao

Open Access Dissertations

Computational fluid dynamics (CFD) simulations are becoming a reliable tool in understanding disease progression, investigating blood flow patterns and evaluating medical device performance such as stent grafts and mechanical heart valves. Previous studies indicate the presence of highly disturbed, transitional and mildly turbulent flow in healthy and pathological arteries. Accurate simulation of the transitional flow requires high order numerics together with a scale resolving turbulence model such as large eddy simulation (LES). This in turn limits one to use a structured fluid flow solver on which complex, branching arterial domains that are typical in the human blood circulatory system could …

Solution To Certain Problems In The Failure Of Composite Structures, Jonathan Goodsell

Open Access Dissertations

The present work contains the solution of two problems in composite structures. In the first, an approximate elasticity solution for prediction of the displacement, stress and strain fields within the m-layer, symmetric and balanced angle-ply composite laminate of finite-width subjected anticlastic bending deformation is developed. The solution is shown to recover classical laminated plate theory predictions at interior regions of the laminate and thereby illustrates the boundary layer character of this interlaminar phenomenon. The results exhibit the anticipated response in congruence with the solutions for uniform axial extension and uniform temperature change, where divergence of the interlaminar shearing stress is …

Electric Machine Differential For Vehicle Traction Control And Stability Control, Sandun Shivantha Kuruppu

Open Access Dissertations

Evolving requirements in energy efficiency and tightening regulations for reliable electric drivetrains drive the advancement of the hybrid electric (HEV) and full electric vehicle (EV) technology. Different configurations of EV and HEV architectures are evaluated for their performance. The future technology is trending towards utilizing distinctive properties in electric machines to not only to improve efficiency but also to realize advanced road adhesion controls and vehicle stability controls. Electric machine differential (EMD) is such a concept under current investigation for applications in the near future. Reliability of a power train is critical. Therefore, sophisticated fault detection schemes are essential in …

Subgrid Scale Modeling For Large Eddy Simulation Of Buoyant Turbulent Flows, Niranjan Shrinivas Ghaisas

Open Access Dissertations

Buoyancy effects due to small density differences commonly exist in turbulent fluid flows occurring in nature and in engineering applications. The large eddy simulation (LES) technique, which is being increasingly used for simulating buoyant turbulent flows, requires accurate modeling of the subgrid sclae (SGS) momentum and buoyancy fluxes. This thesis presents a series of LES and direct numerical simulation (DNS) studies towards a priori and a posteriori evaluation of existing SGS models, and development of new SGS models for the buoyancy flux. This thesis also presents the application of LES, in elucidating qualitative physical features and accurate measures of important …

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 Dynamic Magnetic Equivalent Circuit Model For Design And Control Of Wound Rotor Synchronous Machines, Xiaoqi Wang

Open Access Dissertations

Recently, a new magnetic equivalent circuit (MEC) model was developed to support automated multi-objective design of wound-rotor synchronous machines (WRSMs). In this research, the MEC model and its application have been enhanced. Initial enhancement has focused on using the MEC model to explore machine design and control as a unified problem. Excitation strategies for optimal steady-state performance have been developed. The optimization is implemented in two phases. First, stator and field excitation at rated power is obtained as part of a WRSM design in which the objectives are to minimize machine mass and loss. Second, a map between current and …

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 …

Synthesis Of Graphene Nanomaterials And Their Application In Electrochemical Energy Storage, Guoping Xiong

Open Access Dissertations

The need to store and use energy on diverse scales in a modern technological society necessitates the design of large and small energy systems, among which electrical energy storage systems such as batteries and capacitors have attracted much interest in the past several decades. Supercapacitors, also known as ultracapacitors, or electrochemical capacitors, with fast power delivery and long cycle life are complementing or even replacing batteries in many applications. The rapid development of miniaturized electronic devices has led to a growing need for rechargeable micro-power sources with high performance. Among different sources, electrochemical micro-capacitors or micro-supercapacitors provide higher power density …

Propagation Of Sound In The Vicinity Of Rigid Porous Interfaces, Hongdan Tao

Open Access Dissertations

Propagation of sound in the vicinity of rigid porous interfaces is investigated systematically to facilitate the acoustical characterization of sound absorption materials for noise reduction applications. Various rigid porous interfaces are considered: (1) a semi-infinite porous layer; (2) a porous hard-backed surface; and (3) a porous impedance-backed layer. A closed-form solution and numerical methods are derived with respect to each rigid porous interface condition.

A modified saddle-point method is exploited to investigate the sound field emanating from a monopole source above and below a rigid porous interface. The solutions can be expressed in a form that resembles the classical Weyl-Van …

An Experimental Investigation Of Wind Turbine Aerodynamic Interaction, Brandon Lee Ennis

Open Access Dissertations

Wind turbines have become a viable component in the overall energy makeup of the United States due to improved economics where energy prices have risen and production costs dropped. For a fixed cost, the effectiveness of a wind turbine financially is highly related to its performance. Considering the size of current wind farms, a minor performance improvement will result in large additional sums of revenue. A problem that has received attention with wind farms is that while the fixed costs of the development do get spread out further to reduce the installed cost of each wind turbine, the wind turbines …

Hybrid Opto-Electrokinetic Technique For Micro/Nanomanipulation: Towards Application Of A Novel Non-Invasive Manipulation Technique In Microbiological Assay, Jae-Sung Kwon

Open Access Dissertations

This dissertation explores various physical mechanisms of the Rapid Electrokinetic Patterning (REP) technique suggested for rapid and precise on-chip manipulation of colloids and fluids, and bio-compatibility of the technique for biological applications. REP is a hybrid opto-electrokinetic technique that is driven by the simultaneous application of an AC electric field and a heating source. It can not only effectively transport and manipulate a fluid but also concentrate and pattern particles suspended in the fluid through the combined effect of an electrohydrodynamic flow, electrostatic colloidal interactions and an electrothermal microfluidic flow. These capabilities make REP a promising tool which can provide …

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 …

Hybrid And Smart Topologically Interlocking Materials, Somesh Khandelwal

Open Access Dissertations

This thesis explores the mechanical properties of a new class of multifunctional architectured materials, Topologically Interlocking Materials (TIMs). These materials are created as an assembly of unit elements arranged in an interlocking pattern such that the load transfer between unit elements occurs by contact only. In the absence of adhesive interaction, the tensile component of the load is carried by complementary tensile elements in the form of external constraints or integrated filaments. By virtue of the bottom up design used in creating these materials, their mechanical properties are influenced by a number of controllable parameters including shape, confinement force, scale, …

Multiscale Simulation Of Thermocline Energy Storage For Concentrating Solar Power, Scott Michael Flueckiger

Open Access Dissertations

Concentrating solar power (CSP) is a renewable and demonstrated technology for large-scale power generation but requires multiple engineering advancements to achieve grid parity with conventional fossil fuels. Part of this advancement includes novel and inexpensive thermal energy systems to decouple daily power production from intermittent solar collection. Dual-media thermocline tanks, composed of molten salt and solid rock filler, offer low-cost storage capability but the concept has experienced limited deployment in CSP plants due to unresolved concerns about long-term thermal and structural stability. The main objective of the present work is to advance the understanding of thermocline storage design and operation …

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 …

Graphene Decorated Substrates And Their Interfacial Characteristics, Anurag Kumar

Open Access Dissertations

Carbon nanotubes and graphene have been extensively studied for their excellent properties. As research on carbon expands, two major issues face the scientific community: (i) Expanding the scale of synthesis and (ii) Integration of different carbon structures for improved functionality. While significant advancements have been made in large-scale synthesis, room for improvement remains. As the scale of production increases, issues such as time, cost and energy that may otherwise not be very significant, begin to play greater roles. Thus, in order to effectively transition from laboratory prototypes to industrial products, a synthesis method that can address these issues is strongly …

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 …

Numerical Techniques For The Noninvasive Assessment Of Material Properties And Stresses In Soft Biomaterials, Kent David Butz

Open Access Dissertations

The noninvasive measurement of finite displacements and strains in biomaterials by magnetic resonance imaging (MRI) may be shown to enable mathematical estimates of stress distributions and material properties within structures of the body such as articular cartilage or the intervertebral disc. Such methods will allow for non-contact and patient-specific modeling in a manner not currently possible with traditional mechanical testing or finite element techniques. Therefore, the objective of this thesis was to develop computational methods incorporating imaging-based measures of deformation, composition, and local microstructure to permit nondestructive analysis of a range of complex biomechanical systems.

Finite strain-based models were developed …

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 …

Performance-On-Demand Mems (Podmems): Electrical Control Of Effective Mass, Damping, And Stiffness, Shehrin Sayed

Open Access Theses

We propose the use of electrostatic force feedback to control the stiffness, damping, or mass of MEMS. If feedback forces are proportional to sensed displacement, velocity, or acceleration of a MEMS proof mass, then feedback can be used to increase or decrease the apparent stiffness, damping, and or mass of the MEMS. Such feedback can be used to compensate for process variations, packaging stress, thermal drift, viscous damping, etc. Prior efforts by others include position or velocity based feedback for modifying frequency, bandwidth, quality factor, or sensitivity of resonators. We present a means of quantitative control of stiffness, damping, and …

Modeling Tools For Conformal Orthotic Devices, Steven David Riddle

Open Access Theses

The purpose of this thesis is to advance the design of conformal orthotic devices through the development of two modeling tools to address knowledge gaps in the field.

The field of human orthotics has been continually troubled by identifying successful methods of harnessing devices to the body. Past orthotics have utilized a rigid framework with minimal degrees of freedom (DOFs) driven by hard actuators attached to the body at select anchor points. Many devices design the structure and anchor points such that they reduce the degrees of freedom of a targeted joint, limiting the user's mobility and often causing the …

A Study Of Inkjet Printed Line Morphology Using Volatile Ink With Non-Zero Receding Contact Angle For Conductive Trace Fabrication, Chenchao Shou

Open Access Theses

Inkjet printed lines on a homogeneous solid substrate are studied under the condition that ink evaporation is not negligible and the contact angle exhibits hysteresis with non-zero receding contact angle (NRCA). A new family of line instability is discovered, featured by formation of agglomerations within a line. The agglomeration is explained by a hydrodynamic flow that consistently drives a bead on the substrate towards fresh deposited droplets due to concentration-induced surface tension gradient. Morphologies of lines printed with multiple layers are also explored for the purpose of conductive trace fabrication. A non-uniform morphology is observed across a multi-layer line when …