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Articles 151 - 180 of 953
Full-Text Articles in Aerospace Engineering
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 …
Experimental Investigation Of Effect Of Support Structure Geometry On The Microstructure And Metallurgical Properties Of In718 Parts Fabricated By Selective Laser Melting, Sourabh Hemant Thakare
Experimental Investigation Of Effect Of Support Structure Geometry On The Microstructure And Metallurgical Properties Of In718 Parts Fabricated By Selective Laser Melting, Sourabh Hemant Thakare
Mechanical and Aerospace Engineering Theses - Archive
Additive Manufacturing is a modern manufacturing technique that provides extreme design freedom and the ability to manufacture multiple parts with high complexities at the same time. Various fabrication techniques have been developed, and this study focuses on selective laser melting (SLM) due to its ability to provide near-perfect parts at low cost while being able to work with a wide range of materials. In SLM, the part is manufactured, layer-by-layer, by melting and solidification of powder material under controlled inert conditions. The fabrication of complex geometries is not possible without proper allocation of support structures for the part, which keeps …
Experimental Investigation Of Laser Scan Strategy On The Microstructure, Mechanical Properties And Residual Stress Of Inconel 718 Parts Fabricated By Selective Laser Melting, Kiriti Mamidi
Mechanical and Aerospace Engineering Theses - Archive
Inconel 718 (IN718) is a nickel-based superalloy which exhibits excellent tensile and impact resistant properties along with good corrosion resistance at high temperatures. However, due to the high toughness and work hardening, the machinability of this superalloy is low. Therefore, the selective laser melting (SLM) process has been adopted as an efficient technique to fabricate IN718 parts as it overcomes the problems associated with conventional manufacturing of superalloys. SLM is a widely used additive manufacturing technique which offers the possibility to induce multi-functionality into a single component, and thus reduce the number of components that are needed. In the SLM …
Numerical Analysis Of Immersion Cooling On A Server Using Al2o3/Mineral Oil Nanofluid, Prajwal Srinivas Murthy
Numerical Analysis Of Immersion Cooling On A Server Using Al2o3/Mineral Oil Nanofluid, Prajwal Srinivas Murthy
Mechanical and Aerospace Engineering Theses - Archive
In the current world, technology has developed significantly, with a massive processing and storage of data, resulting in the high increase in Power Density and Heat Generation of servers, computers and its components in data centers. This calls for an engineering solution, for efficient heat dissipation of these servers to ensure their reliability and prolonged working. Air cooling is a prominent method of data center cooling. However, due to its low heat carrying capacity, it is not an efficient method for cooling high heat generating servers. There are two methods to remove this heat, increasing the area of heat transfer …
Optimum Design Of Shimmed Foil Bearing Considering Rotordynamic Stability, Venkata Sai Jyothish Atluri
Optimum Design Of Shimmed Foil Bearing Considering Rotordynamic Stability, Venkata Sai Jyothish Atluri
Mechanical and Aerospace Engineering Theses - Archive
Air foil bearing technology has made substantial development in the past years and has found its applications in high speed turbomachinery. Yet the rotordynamic instability has still been a persisting issue in the single pad air foil bearings. The single pad bearing can resolve this issue by using large clearance with the shaft but the large clearance requires large impeller tip clearance which is not ideal. Multi pad air foil bearings with non-uniform clearance distribution can be used to improve the rotodynamic stability, but the three pad bearings have inferior load capacities due to the less angular length of each …
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 …
Sub-Modelling Approach For Computationally Efficient Thermal Simulations Of Large Li-Ion Battery Packs, Vishnu V. Ganesan
Sub-Modelling Approach For Computationally Efficient Thermal Simulations Of Large Li-Ion Battery Packs, Vishnu V. Ganesan
Mechanical and Aerospace Engineering Theses - Archive
Accurate and rapid prediction of temperature distribution in a large Li-ion battery pack comprising thousands of cells is critical for ensuring safety and performance of battery packs for electric vehicles (EVs). Due to the multiscale geometry and the large number of individual cells in an EV battery pack, full-scale thermal simulations typically take a long time to complete. Approaches for rapidly computing the temperature field in a large battery pack without significant loss of accuracy is, therefore, a key technological need. This paper presents thermal simulations of a large, air-cooled Li-ion battery pack containing thousands of individual cells using the …
Correlation And Effect Of Process Parameters On The Properties Of Inconel 718 Parts Fabricated By Selective Laser Melting Using Response Surface Method, Bharath Bhushan Ravichander
Correlation And Effect Of Process Parameters On The Properties Of Inconel 718 Parts Fabricated By Selective Laser Melting Using Response Surface Method, Bharath Bhushan Ravichander
Mechanical and Aerospace Engineering Theses - Archive
Inconel 718 (i.e., IN718) is a nickel-based superalloy that exhibits outstanding tensile and impact-resistant properties, along with good high-temperature corrosion resistance. However, the machinability is poor due to the high stiffness of IN718. Therefore, additive manufacturing provides an effective solution to overcome the work hardening. Selective laser melting (SLM) is the most common powder-bed additive manufacturing technique designed to use a high power-density laser to melt and fuse the metallic powder to fabricate functional parts with high accuracy. However, the accuracy and the functional properties of the fabricated parts are greatly dependent on the process parameters. Thus, depending on the …
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 …
Computational Study Of Air-Cooled Servers With Improved Ducting And Chassis Re-Design, Himanshu Girishchandra Modi
Computational Study Of Air-Cooled Servers With Improved Ducting And Chassis Re-Design, Himanshu Girishchandra Modi
Mechanical and Aerospace Engineering Theses - Archive
In recent years there has been a phenomenal increase in cloud computing, net-working, virtualization, and storage which has led to an increase in demand for data centers. To meet this demand, there is a need for the latest computing nodes which causes an increase in power consumption. The cooling system occupy almost 40% portion of total energy consumption. Per ASHRAE TC 9.9, IT equipment needs to operate within recommended and allowable temperatures and humidity zone based on the circumstances. As the inlet air temperature increases, fan power consumption increases too and the Central Processing Units (CPUs) and high heat-generating components …
Experimental Study Of Dynamic Cooling Of Racks Using Flow Control Devices, Fnu Akash
Experimental Study Of Dynamic Cooling Of Racks Using Flow Control Devices, Fnu Akash
Mechanical and Aerospace Engineering Theses - Archive
A data center is a cluster of multiple servers that a company uses to store and process large amounts of data. Due to never-ending demands, the processor densities are increasing every day. A higher processor density would result in the servers heating up more than it would normally creating a need for an efficient cooling system. On an average a water-cooled system would consume up to 40% of the total power required by a data center. Studies are being conducted on improving the overall efficiency of the system by either improving the thermal properties of the system or by improving …
Modeling, Fabrication, And Characterization Of Porous Inconel 718 Structures Using Selective Laser Melting Process, Srihari Srivathsan
Modeling, Fabrication, And Characterization Of Porous Inconel 718 Structures Using Selective Laser Melting Process, Srihari Srivathsan
Mechanical and Aerospace Engineering Theses - Archive
Bio-inspired cellular structures are of great interest these days for many applications, from engineering research to industries. Honeycomb, Body-Centered Cubic with/without Z-struts (BCC-Z/ BCC), Face Centered Cubic with/without Z-struts (FCC-Z/ FCC), and Triply Periodic Minimal Surface (TPMS) such as Gyroid, Diamond, and Schwartz lattices are the most common bio-inspired lattice structures. These structures can be tailored based on their structural organization resulting in superior materials with lightweight properties, adequate strength, and low stiffness. Thankfully, additive manufacturing (AM) has made the fabrication of these complex cellular materials realistic. However, the use of AM could lead to several defects, such as damaged …
Cfd Analysis On Liquid Cooled Cold Plate Using Copper Nanoparticles, Sarthak Agarwal
Cfd Analysis On Liquid Cooled Cold Plate Using Copper Nanoparticles, Sarthak Agarwal
Mechanical and Aerospace Engineering Theses - Archive
In today’s world, most data centres have multiple racks with numerous servers in each of them. The high amount of heat dissipation has become the largest server-level cooling problem for the data centres. The higher dissipation required, the higher is the total energy required to run the data centre. Although still the most widely used cooling methodology, air cooling has reached its cooling capabilities especially for High-Performance Computing data centres. Liquid-cooled servers have several advantages over their air-cooled counterparts, primarily of which are high thermal mass, lower maintenance and eventually lower costs by maintenance by labour. Nano-fluids have been used …
Prediction And Validation Of Continuous Fiber Stiffened Plates Manufactured With Continuous Fiber Fabrication, Nabeel Ahmed Khan
Prediction And Validation Of Continuous Fiber Stiffened Plates Manufactured With Continuous Fiber Fabrication, Nabeel Ahmed Khan
Mechanical and Aerospace Engineering Theses - Archive
The purpose of this thesis was to develop an analytical method for predicting the structural properties of continuous fiber stiffened plates, which was then validated both experimentally and via finite element analysis. The MarkForged Mark Two 3D printer enables parts to be printed with continuous carbon fibers embedded within them. A manufacturing process was developed for printing stiffened grids with our without skins, with continuous fiber reinforcement on the top and bottom of the stiffening ribs, which allows bending stiffness can be maximized. An orthotropic grid was printed using Continues Filament Fabrication (CFF), an additive manufacturing process that embeds reinforcing …
Impact Of Viscoelastic Properties Of Low Loss Printed Circuit Boards (Pcbs) On Reliability Of Wcsp Packages Under Drop Test, Akshay Boovanahally Lakshminarayana
Impact Of Viscoelastic Properties Of Low Loss Printed Circuit Boards (Pcbs) On Reliability Of Wcsp Packages Under Drop Test, Akshay Boovanahally Lakshminarayana
Mechanical and Aerospace Engineering Theses - Archive
Reliability of electronic packages is a major concern as different failure modes are induced due to factors such as temperature loads, mechanical stresses, humidity, corrosion and so on. Finite element analysis (FEA) is often performed to assess reliability under different loading conditions such as thermal cycling, drop testing, power cycling and vibrational loads. Having accurate material property data is one of the key requirements to perform successful FEA study, and a significant amount of time and money is spent to perform accurate material characterizations. Lump modeling approach, where components are represented by a block and assigned effective properties, is commonly …
Measurement Of Change In Cte Of Pcbs Due To Single Phase Immersion Cooling And Impact Of Changed Properties Of Pcbs On Solder Joint Reliability Of Bga Package, Sameer Hemant Dhandarphale
Measurement Of Change In Cte Of Pcbs Due To Single Phase Immersion Cooling And Impact Of Changed Properties Of Pcbs On Solder Joint Reliability Of Bga Package, Sameer Hemant Dhandarphale
Mechanical and Aerospace Engineering Theses - Archive
Oil immersion cooling in high-density data centers is emerging as an alternative for traditional air cooling because of the less power consumption, capacity to handle high power density and less space requirement. To adopt this technique extensively, effect of immersion on reliability of server components in dielectric coolant needs to be evaluated. One of the major reliability concerns in BGA package is 2nd level solder joint failure. The primary reason of solder joint failure is CTE mismatch between the PCB and the package. Also, difference in stiffness of the PCB and the package affects the solder joint reliability. As properties …
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, …