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Articles 61 - 90 of 255
Full-Text Articles in Aerospace Engineering
Nanoscale Mechanics Of Disordered Biomolecules In Brain, Md Ishak Khan
Nanoscale Mechanics Of Disordered Biomolecules In Brain, Md Ishak Khan
Mechanical and Aerospace Engineering Dissertations - Archive
The long-term objective of this dissertation is to link blast-induced traumatic brain injury (TBI) with multiscale, multiphysics damage evolution in the brain using experimentally verifiable computations and simulations. The short-term goal is to conduct modeling and simulation to correlate dynamic mechanical loading to damage in sub-axonal components. It is known that the interior of the brain at the macroscale (10^-1 m) is composed of two distinct components, the grey matter, and the white matter. Within the cortex, the grey matter primarily takes the form of cortical columns (mesoscale: 10^-3 m), which are six layered structures, each composed of 8-10 thousand …
Analytical And Experimental Studies On Mixing In Supersonic Flows, Vijay Gopal
Analytical And Experimental Studies On Mixing In Supersonic Flows, Vijay Gopal
Mechanical and Aerospace Engineering Dissertations - Archive
Mixing enhancement in supersonic flow is an important domain of research for enabling the realization of efficient and scalable high speed air-breathing engines (scramjet). Introducing streamwise vorticies in supersonic flow and tailoring their interactions for mixing enhancement is the primary motivation for the present research study. Leveraging the research performed in the group at the Aerodynamics Research Center (ARC), systematic experimental studies on mixing enhancement is carried out in supersonic flows by tailoring the selected modes of streamwise vortex interactions with the aid of in-house developed reduced order method VorTX. This method utilizes the lifting line-vortex theory in supersonic flow …
Automating Aerospace Synthesis Code Generation A Tool For Generic Vehicle Design And Technology Forecasting, Thomas Peter Mccall
Automating Aerospace Synthesis Code Generation A Tool For Generic Vehicle Design And Technology Forecasting, Thomas Peter Mccall
Mechanical and Aerospace Engineering Dissertations - Archive
The principal development and deliverable of this research is a generic synthesis assembling decision support environment for early conceptual design that automates the assembly of synthesis architectures for enhanced product exploration and technology forecasting. The objective of this research is to develop a baseline environment to assess complex vehicle automated synthesis architecture synthetization procedures for adaptation into a greater cognitive system. This tool has been developed as a precursory and developmental task in an initiative towards an artificial intelligence design and research assistant peer. The artificial intelligence peer is a perceived course for future design system evolution in the continued …
Theoretical Modeling Of Heat And Mass Transfer Processes In Phase Change And Electrochemical Energy Storage Systems, Mohammad Parhizi
Theoretical Modeling Of Heat And Mass Transfer Processes In Phase Change And Electrochemical Energy Storage Systems, Mohammad Parhizi
Mechanical and Aerospace Engineering Dissertations - Archive
Theoretical understanding of heat and mass transfer processes in energy storage and conversion devices is of much interest for a wide variety of engineering applications. Two commonly used mechanisms for energy storage are electrochemical energy storage, such as in Li-ion cells, and phase change based energy storage, such as in phase change materials (PCM). Previous studies show that heat and mass transfer in both PCMs and Li-ion cells are critical processes affecting the performance and safety of these systems. This dissertation investigates several theoretical aspects of heat and mass transfer in these energy storage systems, with the goal of improving …
Finite Element Based Methodology To Predict Fatigue Compression Failure In Composite Based On Fiber Kinking Damage Model, Md Saddam Hossain
Finite Element Based Methodology To Predict Fatigue Compression Failure In Composite Based On Fiber Kinking Damage Model, Md Saddam Hossain
Mechanical and Aerospace Engineering Dissertations - Archive
Advanced polymer matrix composites are widely used in designing high-performance and lightweight spacecraft, rotorcraft, and automotive structures, due to its superior performance such as specific stiffness, specific strength, and toughness, which are appealing in reducing the weight of these structures. One critical factor that limits the efficient design of structures composed of fiber-reinforced composites (FRP) is the vulnerability of the material under compression loading since compressive strength of FRP material is typically a lot less compared to the tensile strength. Moreover, composite structure may undergo compression loading either by accidentally or by deliberately, large margins of safety are usually imposed …
A Scaling Investigation Of Feasibility And Hover Endurance For Electric Quasi Quadrotor Configurations, Budhyant Venepalli
A Scaling Investigation Of Feasibility And Hover Endurance For Electric Quasi Quadrotor Configurations, Budhyant Venepalli
Mechanical and Aerospace Engineering Dissertations - Archive
Motivated by recent developments in distributed propulsion electric vehicles, an effort is made in the present study to numerically investigate the upper bound of hover endurance achievable by electric quasi-quadrotors at various mass scales in the range of 0.1 kg to 10000 kg total vehicle mass. A feasible rotor propulsion pod design space is determined considering physics-based conceptual design constraints defined by blade tip Mach number and Reynolds number to ensure effective and energy-efficient generation of lift. A conceptual level scaling optimization for two-bladed rotor quasi-quadrotors was carried out at constant blade tip speed. A momentum theory model, a blade …
A Molecular Scale Study Of Cavitation Growth And Shock Response In Soft Materials, Khandakar Mahmud
A Molecular Scale Study Of Cavitation Growth And Shock Response In Soft Materials, Khandakar Mahmud
Mechanical and Aerospace Engineering Dissertations - Archive
Cavitation is a mechanism through which small vapor-filled cavities are formed in a liquid medium due to rapid changes of pressure. In liquid, the cavitation bubble is created when surrounding pressure drops below the saturation vapor pressure. Here, cavitation formation due to shock wave is considered. The molecular level heterogeneous and homogenous cavitation mechanisms and bubble growth kinetics in soft gelatin hydrogel and water has been studied. Gelatin, which is derived from collagen, is frequently used as a brain simulant material. As such, the morphology of gelatin is very different from water. In the heterogeneous cavitation study, using molecular dynamics …
Experimental And Numerical Study Of Open Bath Immersion Cooling Of Microprocessors., Amirreza Niazmand
Experimental And Numerical Study Of Open Bath Immersion Cooling Of Microprocessors., Amirreza Niazmand
Mechanical and Aerospace Engineering Dissertations - Archive
The increase on demand of communication and networking has resulted to increase for more powerful servers and bigger data centers. With increase the power of electronics, thermal management and cooling of the equipment become a gigantic challenge due to lower surface, they have higher power density and traditional methods of cooling become ineffective. Generally, air cooling method is the first option for cooling of the electronics due to cheaper price. To increase the efficiency and capacity of cooling liquid immersion cooling is used due to higher thermal properties like heat capacity and thermal conductivity compare to air. Two methods of …
Hypoid Gear Noise And Vibration Control In Automotive Rear Axle Systems, Chia-Ching Lin
Hypoid Gear Noise And Vibration Control In Automotive Rear Axle Systems, Chia-Ching Lin
Mechanical and Aerospace Engineering Dissertations - Archive
Gear whine is a key issue for the vehicle powertrain system, and the design of a quiet, reliable driveline system is highly desirable for the automotive industry. From past studies, the main source of excitation for gear vibration and noise is the transmission error (TE), which generates the dynamic mesh force between the gear teeth. Then the vibration transmits through the flexible axle components and radiates off from the surface of the axle housing structure. The dynamic responses of the hypoid geared rotor system in the rear axle have a significant effect on the performance of noise, vibration, and harshness …
A Multiscale Study Of Cavitation Mechanism And Damage In Soft Materials, Fuad Hasan
A Multiscale Study Of Cavitation Mechanism And Damage In Soft Materials, Fuad Hasan
Mechanical and Aerospace Engineering Dissertations - Archive
Cavitation is defined as the formation and growth of the gaseous bubble in bulk liquid due to the tensile pressure followed by the violent collapse. The collapse of the bubble is particularly significant due to its potential to cause damage to relatively stronger materials by either creating pressure waves (symmetric collapse) or liquid jet (asymmetric collapse). The study of cavitation in soft materials (e.g., tissue, brain, gelatin gel, etc.) has, therefore, gained a fair share of attention in the scientific communities. Recent studies have indicated that cavitation could be one of the leading causes of the mild Traumatic Brain Injury …
Molecular Level Mechanical Properties Of Ultra High Temperature Ceramics And Their Nanocomposites, Md Riaz Kayser
Molecular Level Mechanical Properties Of Ultra High Temperature Ceramics And Their Nanocomposites, Md Riaz Kayser
Mechanical and Aerospace Engineering Dissertations - Archive
Ultra High-Temperature Ceramics (UHTC) have been of great interest in the spacecraft, aerospace, and aeronautic industry due to their high melting point and their potential application as a protective material for the stagnation areas of leading edges. In this work, the effect of nanoparticle reinforcement for achieving tailored mechanical properties of UHTC’s has been studied. Two different material systems have been considered, namely the ZrB2-based and the HfO2-based nanocomposites. In the first study, the grain boundary driven mechanical behavior of polycrystalline ZrB2 and ZrC-ZrB2 nanocomposites using large-scale molecular dynamics simulations have been performed. The atomistic models of polycrystalline ZrB2 and …
Reliability Enhancement Of Heterogeneous 3d Integrated Circuit And Characterization Of Thermal Interface Material, A S M Raufur Chowdhury
Reliability Enhancement Of Heterogeneous 3d Integrated Circuit And Characterization Of Thermal Interface Material, A S M Raufur Chowdhury
Mechanical and Aerospace Engineering Dissertations - Archive
Electronic products require high functional integration in small footprints with lower cost. At the same time, it is required to maintain effective communication between the IC’s and the electronic systems. Various challenges are arising due to these factors such as signal processing time, heat dissipation, structural integrity, chip package interaction which need to be dealt effectively during electronic packaging. 3D stacking of the processors and the components accomplishes these goals and in high computing application it reduces the delay. Through-silicon via (TSV) is the heart of 3D integration, and the stacking of chips is emerging now as a powerful tool …
Attraction, Transport And Release Of Water Fleas’ Ephippia For Migration, Xiang Wang
Attraction, Transport And Release Of Water Fleas’ Ephippia For Migration, Xiang Wang
Mechanical and Aerospace Engineering Dissertations - Archive
Planktonic crustaceans of the genus Daphnia live in aquatic environments. Although they are lack of walking and flying capabilities, they have developed adaptations that facilitate the dispersal of their dormant forms, ephippia to cross terrestrial barriers and reach neighborhood waterbodies. It increases the survival rate of their species. A possible way for this spread to occur is the transport of their ephippia through waterfowls’ legs. Yet, little is known about the key role of the legs in the dispersal and the main mechanisms. The ephippia first get attached to the waterfowls’ legs. The waterfowls may then carry these ephippia to …
Investigation Of The Impact Of Material Models On Reliability Assessment Of Electronic Packages, Abel Misrak
Investigation Of The Impact Of Material Models On Reliability Assessment Of Electronic Packages, Abel Misrak
Mechanical and Aerospace Engineering Dissertations - Archive
Drop testing, thermal cycling, power cycling, etc. are some of the tests used to assess the reliability of new electronic products. However, performing experimental study of every new design is costly and time consuming. Computational tools are often employed to perform the required reliability analysis in a shorter time period and save valuable resources. Extensive set of material characterization work needs to be done before an accurate material model can be developed and used in computational analysis. Structural components such as printed circuit boards (PCBs) are critical in the thermomechanical reliability assessment of electronic packages. The bulk material properties of …
Heat Transfer Measurements And Enhancement For Materials And Processes In Polymer Extrusion Based Additive Manufacturing, Hardikkumar Mangaldas Prajapati
Heat Transfer Measurements And Enhancement For Materials And Processes In Polymer Extrusion Based Additive Manufacturing, Hardikkumar Mangaldas Prajapati
Mechanical and Aerospace Engineering Dissertations - Archive
Additive manufacturing (AM) is a burgeoning method for manufacturing over the subtractive manufacturing methodologies. Among the various method of polymer additive manufacturing the fused deposition modeling (FDM) also known as 3D printing is the most popular technique. In this technique, a rastering extruder dispenses a thermoplastic material on to a bed at a temperature greater than its glass transition temperature to build the part. Due to the additive nature of the process, AM introduces several challenges related to functional properties such as strength, thermal conductivity, etc of the eventual part. Measurement of thermal conductivity of additively manufactured polymer samples in …
Reinitiation Mode Study Of Highly Irregular Detonation, Nandakumar Vijayakumar
Reinitiation Mode Study Of Highly Irregular Detonation, Nandakumar Vijayakumar
Mechanical and Aerospace Engineering Dissertations - Archive
The propagation of detonation waves is governed by their stability characteristics. Interest in highly unstable detonation grew when early experiments revealed limits of operation to be directly proportional to the stability of detonation. This research focuses on reinitiation pathways of highly irregular self-sustaining detonation. This is an important aspect of stability which is not yet fully understood, while many possible mechanisms have been proposed in the literature. First, a one-dimensional instability model simulation was performed using a global one-step chemistry mechanism to understand the different unstable modes by increasing the activation energy of a mixture of hydrogen and oxygen. The …
Measurement And Optimization Of Thermal Transport Phenomena For Weld Strength Improvement In Polymer Extrusion Based Additive Manufacturing, Darshan Babu Ravoori
Measurement And Optimization Of Thermal Transport Phenomena For Weld Strength Improvement In Polymer Extrusion Based Additive Manufacturing, Darshan Babu Ravoori
Mechanical and Aerospace Engineering Dissertations - Archive
Additive manufacturing (AM) processes involve layer-by-layer addition of material to fabricate a 3-dimensional part. AM offers significant design and manufacturing flexibility compared to traditional manufacturing approaches. The major challenge in polymer-based additive manufacturing (AM) is that printed parts often have poor thermal/structural properties. These properties depend on weld strength of filaments and which intern depends on the degree of healing/neck growth between deposited polymers. The major contribution of this dissertation is understanding the importance of heat transfer during the printing process on the polymer neck growth and presented with techniques to improve the thermal and structural strength of finished part. …
Design And Optimization Of Thermal Management Approaches In Data Center Applications, Rajesh Kasukurthy
Design And Optimization Of Thermal Management Approaches In Data Center Applications, Rajesh Kasukurthy
Mechanical and Aerospace Engineering Dissertations - Archive
In the present day to day life, Internet of Things (IOT) is everything, i.e., Internet and telecommunication is needed for almost every task of our life, which require data centers. These data centers provide various facilities such as, data processing, storage, transmission, maintenance, operations etc., To perform these tasks, a huge amount of power is consumed, which in turn generates large amount of heat. As these data centers are to be made operational throughout the year, cooling of data centers is of utmost importance. The continued increase in heat flux at the chip level due to new and robust technology …
Design Optimization Of An Elastically Supported Multi-Beam Rotordynamic System To Minimize Flexural Response With Considerations For Robustness, Bret R. Hauser
Design Optimization Of An Elastically Supported Multi-Beam Rotordynamic System To Minimize Flexural Response With Considerations For Robustness, Bret R. Hauser
Mechanical and Aerospace Engineering Dissertations - Archive
Modern rotating machines are often required to operate with a small physical footprint and/or overall weight; necessitating that they utilize wide-ranging shaft speed to accomplish needed power levels. It is not uncommon that these designs also be required to support operation through a speed range encompassing multiple Critical Speeds while also limiting flexural vibrations to acceptable levels. Design optimization of this class of problem can be particularly difficult in that responses can be highly multi-modal and, when coupled with Finite Element (FE) solvers meet the conditions of a High Dimensional, Computationally Expensive Black Box (HEB) system. Because of this, some …
Pulsed Detonation Engine Nozzle Design And Analysis, Rahul Kumar
Pulsed Detonation Engine Nozzle Design And Analysis, Rahul Kumar
Mechanical and Aerospace Engineering Dissertations - Archive
For a hypersonic flight mission, different flight regimes have been recognized. The successful and efficient operation of the aircraft to traverse through all the flight regimes requires the integration of various propulsion cycles into a single flow path. Using the phenomenon of detonation initiation and propagation, a multi-mode detonation based propulsion concept was proposed for hypersonic flight. Of the different modes proposed, it was recognized that the efficient operation of Normal Detonation Wave Engine (NDWE) mode and Oblique Detonation Wave Engine (ODWE) mode played an important role as they delivered thrust at critical parts of the trajectory. For this study, …
Improving Compressive Strength Of High Modulus Carbon-Fiber Reinforced Polymeric Composite With Varying Modulus Fibers, Sarvenaz Ghaffari
Improving Compressive Strength Of High Modulus Carbon-Fiber Reinforced Polymeric Composite With Varying Modulus Fibers, Sarvenaz Ghaffari
Mechanical and Aerospace Engineering Dissertations - Archive
There has been a strong demand in using high-modulus (HM) carbon-fiber composites potentially enabling lightweight aircraft structures with significant weight savings. However, extremely low fiber-direction compressive strength has been a well-recognized weakness of the HM composites, preventing their implementation in aircraft platforms. Fiber-direction compressive strength of HM and intermediate-modulus (IM) carbon fiber-reinforced polymers (CFRP’s) is presumably governed by microstructural stability. However, strong decrease in fiber-direction compressive strength of HM carbon-fiber composites, compared to their intermediate modulus (IM) counterparts, contradicts predictions from available microstructural buckling theories. A recent work demonstrated that significant improvement in the fiber-direction compressive strength of HM carbon-fiber …
Numerical Study Of Detonation Flame Arrestor Performance And Detonation Interaction With The Arrestor Element, Hoden Ali Farah
Numerical Study Of Detonation Flame Arrestor Performance And Detonation Interaction With The Arrestor Element, Hoden Ali Farah
Mechanical and Aerospace Engineering Dissertations - Archive
A numerical study of detonation propagation and interaction with a flame arrestor product in a combustible gas/vapor transport pipeline system is conducted. The flame arrestor element is modeled as a porous medium using the Forchheimer equation, which is incorporated in the governing conservation equations as a momentum sink. The Forchheimer porous medium model is then used to model the flow through a representative four-inch detonation flame arrestor and is validated with experimental data. The detonation propagation simulation is modeled with the Reynolds averaged Navier-Stokes (RANS) equations extended for reacting flow. A 21-step chemical kinetic mechanism with 10 species is used …
Numerical Study Of High–Frequency Fluidic Valve Injectors For Detonation Engine Applications, Sushma Yalavarthi
Numerical Study Of High–Frequency Fluidic Valve Injectors For Detonation Engine Applications, Sushma Yalavarthi
Mechanical and Aerospace Engineering Dissertations - Archive
The feasibility of fluidic valves for use in detonation-based engines was studied numerically. The fluidic valve acted by shutting off reactant flow through the high pressure behind detonation waves propagating past the valve opening. The valve which featured a plenum cavity was mounted to the side of a pulsed detonation engine, an arrangement that allowed the valve to be characterized under a sustained operation. A series of different cavity lengths were studied. Further, a numerical study of the high-frequency fluidic valve was conducted by using a two-dimensional reactive Euler solver. A 19–step elementary mechanism was employed for the stoichiometric oxyhydrogen …
Dynamics Of A Pulse Detonation Engine Driven Linear Power Generator, Umang Umeshkumar Dighe
Dynamics Of A Pulse Detonation Engine Driven Linear Power Generator, Umang Umeshkumar Dighe
Mechanical and Aerospace Engineering Dissertations - Archive
The dynamics of a pulse detonation engine driven linear power generator were studied. For an ideal pulse detonation engine, the thrust generated is in the form of a piecewise function given by the Endo-Fujiwara model. Nonlinear electromagnetic damping is also introduced in the system due to the rare earth permanent magnets present in the linear generator architecture. Various linear generator topologies were studied using static magnetic analysis. Two configurations of a single degree-of-freedom oscillator system, one with a linear spring restoring force and another with geometric nonlinear spring restoring force, were investigated to study any potential advantages of using nonlinear …
Droplet-Based Microextraction Of Dna Enabled By Electrowetting-On-Dielectric Digital Microfluidics, Shubhodeep Paul
Droplet-Based Microextraction Of Dna Enabled By Electrowetting-On-Dielectric Digital Microfluidics, Shubhodeep Paul
Mechanical and Aerospace Engineering Dissertations - Archive
In recent years there have been significant advances in micro/nanotechnologies employing miniaturized platforms to achieve efficient sample pre-processing, separation, and quantification processes. The idea of bringing several lab-scale protocols on to a single chip, i.e., a lab-on-a-chip (LOC) device along with automation, is a reality now. Miniaturization of biochemical operations usually handled in a laboratory has numerous advantages, such as cost effectiveness, multiplexing, assay speed, and sensitivity. Microfluidic technologies used in LOC devices can manipulate tiny volumes of samples and reagents to perform on-chip protocols with minimal human intervention. Electrowetting-on-dielectric (EWOD)-based digital microfluidics (DMF) is one of the LOC platforms …
Assessment Of Material State In Composites Using Global Dielectric State Variable, Vamsee Vadlamundi
Assessment Of Material State In Composites Using Global Dielectric State Variable, Vamsee Vadlamundi
Mechanical and Aerospace Engineering Dissertations - Archive
Composites are heterogeneous in nature and a fundamental understanding of the material response to applied mechanical, thermal, electrical and other multi-physical fields is required to efficiently design and synthesize the material system and demands attention to long-term behavior in particular. Unlike metals, composites are designed to develop distributed damage and initiation of a single microscopic crack does not individually affect the strength/life of these materials. Therefore, the primary interest is not in single local events but in the process of interaction of multiple events that have a collective global effect on the material behavior. The interaction of these local events …
Analysis Of Laminated Curved Beam With And Without Defects And Imperfections, Wei-Tsen Lu
Analysis Of Laminated Curved Beam With And Without Defects And Imperfections, Wei-Tsen Lu
Mechanical and Aerospace Engineering Dissertations - Archive
Several studies have focused on the modeling and response characterization of composite structural members, with particular emphasis on composite curved beams. The class of curved beam is explored to determine mechanical response in primary aerospace structural applications. The present work focuses on developing analytical closed-form solutions for investigating composite curved beams with and without fiber waviness and delamination. The present work can efficiently characterize the structural behavior of composite curved beams under bending. This work shows the development of a novel mathematical approach to predict structural performance by investigating axial stiffness, bending stiffness with consideration of shear deformation in composite …
Electrowetting-On-Dielectric (Ewod) Digital Microfluidic Device For Synthetic Organic Chemistry, Matin Torabinia
Electrowetting-On-Dielectric (Ewod) Digital Microfluidic Device For Synthetic Organic Chemistry, Matin Torabinia
Mechanical and Aerospace Engineering Dissertations - Archive
Over the past decades, microscale chemical reaction technology has been attractive in diverse areas of chemistry. It allows the precise control of quantified reagents and highly efficient heat and mass transfer, because of a large interface-to-volume ratio–particularly in case of the exothermic reaction and mixing–, reduced consumption of toxic or expensive agents, improved reaction profiles, and enhanced selectivity compared to macro-scale reactions. The mainstream microscale reaction processes were established using continuous microchannel flow systems, which has emerged as a powerful complement to batch chemistry on the laboratory scale due to relative advantages, some of which include: increased safety, more accurate …
An Implementation Of The Regularized Extended Finite Element Method In Abaqus, Yu-Jui Liang
An Implementation Of The Regularized Extended Finite Element Method In Abaqus, Yu-Jui Liang
Mechanical and Aerospace Engineering Dissertations - Archive
The Regularized eXtended Finite Element Method (Rx-FEM) methodology is a discrete damage modeling (DDM) technique, which represents an approach to the progressive damage analysis (PDA) in laminated composites when multiple damage events such as matrix cracks and delamination are introduced into the model via the displacement discontinuities. In the Rx-FEM, the Heaviside step function that is typically used to introduce a displacement discontinuity across a crack surface in the eXtended Finite Element Method (x-FEM) is replaced by a continuous function approximated by using the finite element (FE) shape functions. This regularization offers unique possibility for the implementation of the Rx-FEM …
Nonlinear Control Of Unmanned Aerial Vehicles With Cable Suspended Payloads, Ameya Godbole
Nonlinear Control Of Unmanned Aerial Vehicles With Cable Suspended Payloads, Ameya Godbole
Mechanical and Aerospace Engineering Dissertations - Archive
The research focuses on the mathematical modeling and control of an unmanned aerial vehicle with cable suspended payload. A comprehensive mathematical model is derived for a quadcopter with a cable suspended payload using the Newton-Euler method and the Euler-Lagrange formulation. These methods assume that the cable is massless and always taut and cannot be used to simulate the cases when the cable is flexible. Hence, an alternative approach to model the flexibility of the cable is presented using Lagrangian mechanics by approximating the cable to be a chain of serially connected links. The motion of the payload induces disturbances on …