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Articles 331 - 360 of 953
Full-Text Articles in Aerospace Engineering
Board Level Solder Joint Reliability Assessment Study Of Megtron 6 Vs Fr-4 Under Power Cycling And Thermal Cycling, Jyotirmoy Denria
Board Level Solder Joint Reliability Assessment Study Of Megtron 6 Vs Fr-4 Under Power Cycling And Thermal Cycling, Jyotirmoy Denria
Mechanical and Aerospace Engineering Theses - Archive
High frequency laminates like Nelco N4000-13, Isola FR408 and Panasonic Megtron 6 packages gained popularity among the industry due to better and improved electrical performances, Improved impedance control, low moisture absorption, good thermal management. High speed laminates are extensively used in high-speed system-level interconnects like high speed network equipment, mainframes, IC testers and high frequency measuring instruments. When an electronic device is turned off and then turned on multiple times, it creates a loading condition called power cycling. The die is the only heat source causing non-uniform temperature distribution. In this paper, the solder joint reliability assessment of Megtron 6 …
A Design Methodology For Continuous Fiber Additive Manufacturing Using Advanced Computer Aided Engineering Techniques, Nicholas Venter
A Design Methodology For Continuous Fiber Additive Manufacturing Using Advanced Computer Aided Engineering Techniques, Nicholas Venter
Mechanical and Aerospace Engineering Theses - Archive
A design methodology for Continuous Carbon Fiber Additive Manufacturing (CCFAM) developed using Computer Aided Engineering (CAE) techniques takes advantage of both the mechanical strength of composite materials and the Fused Filament Fabrication (FFF) method. By performing topology optimization and Finite Element Analysis (FEA) on a load-bearing part, engineers can design much lighter optimized parts that are just as strong as those produced using FFF. This weight reduction is achieved by relying on the mechanical strength of continuous carbon fibers printed alongside a traditional thermoplastic matrix. The FFF additive manufacturing method enables the production of complex shapes, which can match the …
Effect Of Underfill Material & Gap Height On Reliability Of Low-K Large-Die Flip Chip Package Under Thermal Loading, Paul Crisanth
Effect Of Underfill Material & Gap Height On Reliability Of Low-K Large-Die Flip Chip Package Under Thermal Loading, Paul Crisanth
Mechanical and Aerospace Engineering Theses - Archive
The reliability assessment of package assembly is important to predict the performance of any microelectronic devices. Formation of fatigue cracks at the interface between the solder joint and component is the common failure occurring in widely used microelectronic devices. Lead-free solders and advanced silicon process nodes with the low-k dielectrics flip chip package are used and are facing significant reliability challenges. The mismatch of coefficient of thermal expansion (CTE) between the chip and substrate affect solder joint reliability. The underfill encapsulant packaging is widely used to improve chip device reliability. In this paper, we are studying the effect of different …
A Comparative Study Of Wooden And Hyrbid Composite Crossarms Of An Electric Utility Pole, Rohit Avadhani
A Comparative Study Of Wooden And Hyrbid Composite Crossarms Of An Electric Utility Pole, Rohit Avadhani
Mechanical and Aerospace Engineering Theses - Archive
Most of the cross arms in the country are made from wood. Wood, although easily accessible, has its own defects. Environmental effects which includes the expansion and contraction of wood over the years which will disrupt its structural integrity, the presence of termites and other insects which dig into wood and destroy it from the inside, Materials wastage when it comes to improving the structural strength by increasing the cross-sectional thickness and height The replacement of wood with composites seems like a logical idea and also a solution to most of the problems. The applications of composites in our day …
Effect Of Solder Voids And Distance To Neutral Point (Dnp) On Sjr Of Wcsp Under Reflow Condition And Thermal Cycling, Aniruddha Doiphode
Effect Of Solder Voids And Distance To Neutral Point (Dnp) On Sjr Of Wcsp Under Reflow Condition And Thermal Cycling, Aniruddha Doiphode
Mechanical and Aerospace Engineering Theses - Archive
Since the introduction of Chip Scale Packages (CSP’s) in the early 2000s, they have become one of the biggest packaging trends in recent history. There are currently over 50 different types of CSP’s available throughout the industry and the numbers are increasing almost daily. Wafer Level Chip Scale Package’s (WCSP) is kind of CSP’s used widely due to its small form factor which offers efficient use of limited space and miniaturization of the electronic device. On the other hand, small form factor typically incurs greater initial cost in product design and development. In an electronic device, it is equally important …
Strength And Damage Prognosis Of Adhesive Bond And Inter-Ply Hybrid Composites Based On Dielectric Properties, Priyanshu K. Banerjee
Strength And Damage Prognosis Of Adhesive Bond And Inter-Ply Hybrid Composites Based On Dielectric Properties, Priyanshu K. Banerjee
Mechanical and Aerospace Engineering Theses - Archive
Composite materials have found their applications in a wide range of industries particularly in the aerospace and automotive sectors. This is because they are comparatively light-weight and provide a much better corrosion and wear resistance as compared to other ceramics and metals. Adhesive bonding can be used to improve the stress distribution between these composite materials. Moreover, adhesive bond decreases the weight and concentration of stresses in the structure. Broadband Dielectric Spectroscopy, BbDS is a robust tool used for analyzing the dielectric properties of a polymer composite. This method can be used to monitor the curing process of the specimen. …
Multiphase Flow Modeling And Analysis Of Phased Filling Process For Pulsed Detonation Engine, Nirmal Kumar Umapathy
Multiphase Flow Modeling And Analysis Of Phased Filling Process For Pulsed Detonation Engine, Nirmal Kumar Umapathy
Mechanical and Aerospace Engineering Theses - Archive
Filling of reactants into a pulsed detonation engine (PDE) should be carried out quickly because any lengthening of the fill time will lead to an increased cycle time. The fill process and, the purge process constitutes a large proportion of time in a cycle. The purpose of this research was to improve the time of fill by implementing various injection geometries in two injection schemes with five different premixed stoichiometric fuel-air mixture injected at wide range of velocity. The different configurations examined were end wall injection, side wall injection with ports angled and normal to the flow direction and staggered …
An Investigation Of Topology Optimization For Coupled Thermo-Structural Loading For Additive Manufacturing, Vaibhav Shankar Gaikwad
An Investigation Of Topology Optimization For Coupled Thermo-Structural Loading For Additive Manufacturing, Vaibhav Shankar Gaikwad
Mechanical and Aerospace Engineering Theses - Archive
This work investigates the ability of topology optimization methods to design multifunctional components with coupled thermo-structural loading for fabrication with additive manufacturing technologies. Topology Optimization is a mathematical approach developed to perform design optimization with the purpose of reducing material usage, while maximizing the structural and thermal performance, in accordance to specific design constraints. Additive manufacturing provides the capability to create internal structures and complex surfaces developed by topology optimization that would not be possible to produce by conventional manufacturing. The more structurally efficient configuration generated by topology optimization and fabricated with additive manufacturing can result in components with improved …
Numerical Study Of Droplet Evaporation, Ritul Gandhi
Numerical Study Of Droplet Evaporation, Ritul Gandhi
Mechanical and Aerospace Engineering Theses - Archive
Droplet evaporation plays a vital role in various engineering fields such as air/fuel premixing, inkjet printing and many more. The high rate of power dissipation from the integrated circuits and chips of electronic devices creates a need for cooling it to achieve their optimal functionality. The high rate of cooling can be achieved by thin film evaporation of water by phase change as compared to the air cooling methods. Therefore, the study of droplet evaporation is necessary to understand the underlying physics and effects of different parameters on cooling performance. Numerical study of droplet evaporation has been done by using …
Self-Propulsion Of Leidenfrost Drops Between Non-Parallel Structures, Cheng Luo, Manjarik Mrinal, Xiang Wang
Self-Propulsion Of Leidenfrost Drops Between Non-Parallel Structures, Cheng Luo, Manjarik Mrinal, Xiang Wang
Mechanical and Aerospace Faculty Publications - Archive
In this work, we explored self-propulsion of a Leidenfrost drop between non-parallel structures. A theoretical model was first developed to determine conditions for liquid drops to start moving away from the corner of two non-parallel plates. These conditions were then simplified for the case of a Leidenfrost drop. Furthermore, ejection speeds and travel distances of Leidenfrost drops were derived using a scaling law. Subsequently, the theoretical models were validated by experiments. Finally, three new devices have been developed to manipulate Leidenfrost drops in different ways.
Conditions For Barrel And Clam-Shell Liquid Drops To Move On Bio-Inspired Conical Wires, Cheng Luo, Xiang Wang
Conditions For Barrel And Clam-Shell Liquid Drops To Move On Bio-Inspired Conical Wires, Cheng Luo, Xiang Wang
Mechanical and Aerospace Faculty Publications - Archive
It has been reported that, in a foggy environment, water drops with either barrel or clam-shell shapes are capable of self-running on conical wire-like structures, such as cactus spines, spider silk, and water striders’ legs. On the other hand, the corresponding moving mechanisms are still not quite understood. For instance, it is unclear under what conditions clam-shell drops would move from the tip towards the root on a conical wire. In this work, based on the balance of forces, we derive conditions for a drop to self-transport towards or away from the root. We find that, although barrel and clam-shell …
Advanced Methods Of Nondestructive Inspection Of Composite Structures Based On Limited Angle X-Ray Computed Tomography, Ekaterina Bostaph
Advanced Methods Of Nondestructive Inspection Of Composite Structures Based On Limited Angle X-Ray Computed Tomography, Ekaterina Bostaph
Mechanical and Aerospace Engineering Dissertations - Archive
This research aimed to study the potential for breaking through object size limitations of current X-ray computed tomography (CT) systems by implementing a limited angle scanning technique. CT stands out among other industrial nondestructive inspection (NDI) methods due to its unique ability to perform 3D volumetric inspection, unmatched micro-focus resolution, and objectivity that allows for automated result interpretation. This work attempts to advance NDI technique to enable microstructural material characterization and structural diagnostics of composite structures, where object sizes often prohibit the application of full 360o CT. Even in situations where the objects can be accommodated within existing micro-CT configuration, …
Modeling And Measurements Of Thermal Transport In Li-Ion Based Energy Conversion And Storage Devices, Krishna Shah
Modeling And Measurements Of Thermal Transport In Li-Ion Based Energy Conversion And Storage Devices, Krishna Shah
Mechanical and Aerospace Engineering Dissertations - Archive
Heat transfer is of significant importance in energy conversion and storage devices such as Lithium-ion batteries for its safe operation and performance. Li-ion batteries are considered to be the state of the art among the energy storage devices due to their very high energy density and high power density. However, the safety of Li-ion batteries has become a concern in light of recent incidents, where there have been catastrophic events reported due to overheating of large battery packs. It is imperative to fully understand the nature of thermal transport in Li-ion cells. However, this has not been explored in detail …
Space Access Systems Design: Synthesis Methodology Development For Conceptual Design Of Future Space Access Systems, Loveneesh Rana
Space Access Systems Design: Synthesis Methodology Development For Conceptual Design Of Future Space Access Systems, Loveneesh Rana
Mechanical and Aerospace Engineering Dissertations - Archive
The early Conceptual Design (CD) of a Space Access System (SAS) is the most abstract, innovative, and technologically challenging phase throughout the entire aerospace product development life-cycle. While it is the most important life-cycle phase which influences around 80 percent of the overall life-cycle-cost, it is also the least understood design phase. The history of space access vehicle design provides numerous examples of projects that failed due to lack of a proper technology-hardware-mission assessment in the CD phase. The present dissertation addresses this crucial phase and develops a prototype best practice solution process to advance the current state of the …
Micro/Nanoencapsulated Phase Change Materials (Pcms) Toward High Temperature Thermal Energy Storage Applications, Hanfei Zhang
Micro/Nanoencapsulated Phase Change Materials (Pcms) Toward High Temperature Thermal Energy Storage Applications, Hanfei Zhang
Mechanical and Aerospace Engineering Dissertations - Archive
Thermal energy is one of the most important renewable energy sources because of its abundancy. However, despite the long history of people practically trying to harvest thermal energy, the efficiency of thermal energy storage and application to daily life utilization is still a major limitation, especially for high temperature (>300oC) applications. Concentrating solar power (CSP) is one of the very few technologies that have been used commercially to produce electricity from solar thermal energy. Benefiting from the extra latent heat stored during melting/freezing, phase change materials (PCMs) with a high melting point are commonly used in these systems functioning …
Field-Directed Fabrication Of Hierarchical Structures Toward Electrochemical Applications, Anirudh Balram
Field-Directed Fabrication Of Hierarchical Structures Toward Electrochemical Applications, Anirudh Balram
Mechanical and Aerospace Engineering Dissertations - Archive
The ubiquity of hierarchical structures in nature indicates an inherent advantage to having morphological features comprised of multiple length scales. Such structures help maximize interfacial surface area, allowing for efficient chemical reactions and mass transport despite volumetric constraints. In electrochemical applications such as batteries, supercapacitors, electrolysis, fuel cells, catalysis etc. there is a similar necessity to maximize electrochemically active surface area to facilitate facile charge and mass transport. Inspired by examples in nature, this work seeks to develop scalable fabrication techniques to obtain hierarchically structured high-performance electrodes for electrochemical applications, with a focus on energy applications. Particular emphasis was laid …
Numerical Investigation Of Stability Characteristics Of A Jet In Counterflow, Siddarth Chintamani
Numerical Investigation Of Stability Characteristics Of A Jet In Counterflow, Siddarth Chintamani
Mechanical and Aerospace Engineering Dissertations - Archive
A jet in counterflow is a configuration in which a jet is issued into an opposing external stream of fluid. Some of the possible applications of this configuration include study of pollutant discharge into body of water, aerodynamic flame holder in after burner, reduction of drag and cooling of bluff body by ejecting a jet of coolant gas into counterflowing stream, thrust vectoring of supersonic jets, sonic boom mitigation. The instability associated with flow reversal which is observed in this configuration of the jet leads to enhanced mixing. However, a detailed understanding of the dynamics and control is needed to …
Multi-Mesh Reduced-Order Basis Method For Finite Element Analysis, Ashkan Akbariyeh
Multi-Mesh Reduced-Order Basis Method For Finite Element Analysis, Ashkan Akbariyeh
Mechanical and Aerospace Engineering Dissertations - Archive
Reduced order modeling of differential equations parametrized over a parameter space can be used to accelerate optimization and parameter estimation problems. The method of snapshots or reduced order basis is well established among researchers as a tool to build reduced order models of ordinary differential equations. The reduced order basis method has been utilized for numerical solution of parametric PDE problems by researchers in recent years and has many advantages over response surface methods. The application of ROB to finite element analysis has been restricted to using a fixed mesh for snapshots. In this work, a new method is developed …
Thermal Measurement And Optimization Of Materials And Processes In A Li-Ion Cell, Vivek Vishwakarma
Thermal Measurement And Optimization Of Materials And Processes In A Li-Ion Cell, Vivek Vishwakarma
Mechanical and Aerospace Engineering Dissertations - Archive
Applications of Lithium-ion cells range from consumer electronics to electric cars because of their excellent electrochemical performance and energy density. However, a Li-ion cell also suffers from poor thermal transport characteristics, which reduces performance, causes overheating and thermal runaway. This work contributes towards thermal characterization of key Li-ion battery materials and identifies and improves the rate-limiting, material-level thermal conduction process in a Li-ion cell. Among the various materials within a Li-ion cell, the separator is expected to have the lowest thermal conductivity. In this work, we have carried out first-ever measurements of thermal conductivity and heat capacity of the separator …
Flexible-Continuum Robot For Bladder Tissue Diagnostics, Samson Abimbola Adejokun
Flexible-Continuum Robot For Bladder Tissue Diagnostics, Samson Abimbola Adejokun
Mechanical and Aerospace Engineering Theses - Archive
The aim of this thesis is to investigate and develop a robotic system capable of a transurethral palpation of any targeted area on the bladder interior wall tissue to determine the biomechanical properties of the tissue considering the urinary tract geometric constraints and to demonstrate the motion kinematics of such robot to achieve a desired robot pose normal to any localized region throughout the bladder workspace. Current technologies have, to varied degree of success, provide approximate, global diagnostics information to bladder tissue elasticity. However, no direct access qualitative methods to measure the bladder tissue properties are known. For this reason, …
Enhancing Indirect / Direct Evaporative Heat Exchanger In Data Center Cooling By Using Phase Change Material, Ahmed Ali Abuklam
Enhancing Indirect / Direct Evaporative Heat Exchanger In Data Center Cooling By Using Phase Change Material, Ahmed Ali Abuklam
Mechanical and Aerospace Engineering Theses - Archive
Electrical usage in data center continues to grow and recent projection estimate that it contributes 2% in the electricity use in the U.S. One method of controlling the electrical usage during cooling is to reduce or eliminate mechanical cooling; however, using indirect/direct evaporative (IDE) cooling system is starting to be quite popular. IDE has limitations and in this paper we will show how phase change material (PCM) can extend the cooling capacity of IDE. The PCM has been used for temperature control operations. Latent heat storage is one of the most efficient ways of storing thermal energy in PCM. The …
Cfd Simulation And Design Optimization To Improve Cooling Performance Of Open Compute ‘Big Sur’ Server, Mangesh Mohan Dhadve
Cfd Simulation And Design Optimization To Improve Cooling Performance Of Open Compute ‘Big Sur’ Server, Mangesh Mohan Dhadve
Mechanical and Aerospace Engineering Theses - Archive
In recent years, there have been a phenomenal increase in Artificial Intelligence and Machine Learning that require data collection, mining and using data sets to teach computers certain things to learn, analyze image and speech recognition. Machine Learning tasks require a lot of computing power to carry out numerous calculations. Therefore, most servers are powered by Graphics Processing Units (GPUs) instead of traditional CPUs. GPUs provide more computational throughput per dollar spent than traditional CPUs. Open Compute Servers forum has introduced the state-of-the-art machine learning servers “Big Sur” recently. Big Sur unit consists of 4OU (OpenU) chassis housing eight NVIDIA …
Analysis Of Composite Structures With Curvature Under Temperature Environment, Muthu Ram Prabhu Elenchezhian
Analysis Of Composite Structures With Curvature Under Temperature Environment, Muthu Ram Prabhu Elenchezhian
Mechanical and Aerospace Engineering Theses - Archive
Composite structures are frequently exposed to environments with change in temperatures during their service life. The thermal behaviours of the laminated composite structures are more pronounced than that of the structures made of isotropic materials. For the structures under thermal environment, extensive studies have been conducted to investigate the induced thermal stresses and deformation of composite laminated plates by linear/non-linear analysis and composite structures by finite element analysis. The main focus of this study is concentrated on development of an analytical method for analyzing composite thin shells and/or moderate curved beam structures under temperature environment. This includes the derivation of …
Finite Element Analysis On Hybrid Boron-Carbon Composites, Amruta Rupa Nemani
Finite Element Analysis On Hybrid Boron-Carbon Composites, Amruta Rupa Nemani
Mechanical and Aerospace Engineering Theses - Archive
Adaptability to different situations and the ease of combination makes composites one of the most extensively used materials in the engineering industries. One of the ways of managing properties of composites is hybridization of different fibers in one composite. This work merely focuses upon the analysis of effective stiffness of Hybrid materials which is carried out using Finite Element Method. A series of models were experimented in a sequence by imposing various conditions on each of them. Boron and Carbon fibers were used primarily for these experiments because of their better compatibility than other combinations of fibers. Due to the …
Thermal Modeling Of 3-Dimensionally Stacked Dram Memory, Ratnesh Raj
Thermal Modeling Of 3-Dimensionally Stacked Dram Memory, Ratnesh Raj
Mechanical and Aerospace Engineering Theses - Archive
A large fraction of energy consumed in modern microelectronic devices and systems is taken up by memory access operations, which is expected to cause significant temperature rise. Since memory access operations are very short this is expected to inherently be a transient thermal phenomenon. Despite the critical importance of thermal management in microelectronics, not much work exists on understanding the nature of thermal transport during memory access operations. In this work, a mathematical model to predict the transient temperature rise within a 3D layered memory chip is presented. Most heat-generating memory access processes occur over a short timescale for which …
Numerical Simulation Of Flow In Fluidic Valves In Rotating Detonation Engines, Nandini Gopalakrishnan
Numerical Simulation Of Flow In Fluidic Valves In Rotating Detonation Engines, Nandini Gopalakrishnan
Mechanical and Aerospace Engineering Theses - Archive
Rotating detonation engines (RDE) have received considerable research attention in recent times for use in propulsion systems. The cycle frequency of operation of an RDE can be as high as 10,000 Hz. Conventional mechanical valves cannot operate at such high frequencies, leading to the need for propellant injectors or valves with no moving parts. A fluidic valve is such a valve and is the focus of this study. The valve consists of an orifice connected to a constant area plenum cavity which operates at constant pressure. The fluidic valve supplies propellants to the detonation tube through the orifice. Hydrogen – …
Experimental And Computational Study Of Multi-Level Cooling Systems At Elevated Coolant Temperatures In Data Centers, Manasa Sahini
Experimental And Computational Study Of Multi-Level Cooling Systems At Elevated Coolant Temperatures In Data Centers, Manasa Sahini
Mechanical and Aerospace Engineering Dissertations - Archive
Data centers house a variety of compute, storage, network IT hardware where equipment reliability is of utmost importance. Heat generated by the IT equipment can substantially reduce its service life if T_(J,Max), maximum temperature that the microelectronic device tolerates to guarantee reliable operation, is exceeded. Hence, data center rooms are bound to maintain continuous conditioning of the cooling medium. This approach often results in over-provisioned cooling systems. In 2014, U.S. Data center electricity consumption is about 1.8% of the total electrical energy in the country. Hence, data center power and cooling have become significant issues facing the IT industry. The …
Prediction Of Process-Induced Defects By Ply-Drops In The Design Optimization Of A Complex Composite Laminate, Sitanshu Pandya
Prediction Of Process-Induced Defects By Ply-Drops In The Design Optimization Of A Complex Composite Laminate, Sitanshu Pandya
Mechanical and Aerospace Engineering Theses - Archive
The objective of this work is to characterize manufacturing process-induced warping defects due to ply drops in composite laminates to guide composite laminate design. Composite laminate optimization seeks weight efficient models, but the process can also generate complex ply geometry, which compounds the challenges of the already rigorous composite laminate manufacturing process. Increased design complexity enhances the likelihood of manufacturing process-induced defects like warping; therefore, it is important to predict such defects in the design phase to make the product more efficient yet producible and thereby avoid such defects. This work study is manufacturing process induced warpage in complex composite …
Gain Scheduling Controller For Aircraft With Mass And Inertia Variation, Eunyoung Kim
Gain Scheduling Controller For Aircraft With Mass And Inertia Variation, Eunyoung Kim
Mechanical and Aerospace Engineering Dissertations - Archive
Robustness is one of the main control design requirements for aircraft control.Robustness is sought in the stability and performance of closed loop system against various factors such as disturbance, measurement error, modeling error or un-modeled dynamics. In aircraft control design, it is common to assume that the mass and inertia properties of aircraft are constant. Further, aircraft is assumed to have symmetry inits mass distribution relative to its mid-vertical plane. There are, however, cases where the aircraft mass changes rapidly, most notably in aerial refueling operation.The mass change also results in changes in the inertia matrix. An aircraft may also …
On Space Program Planning: Quantifying The Effects Of Spacefaring Goals And Strategies On The Solution Space Of Feasible Programs, Mark Douglas Coley
On Space Program Planning: Quantifying The Effects Of Spacefaring Goals And Strategies On The Solution Space Of Feasible Programs, Mark Douglas Coley
Mechanical and Aerospace Engineering Dissertations - Archive
An organization's space program represents the coalescence of top-level goals and strategies with the specific, lower-level combinations of mission architectures, hardware, and technology. High costs and long lead times necessitate substantial planning and key decisions to be made years, possibly decades, in advance. Unfortunately, the methods and processes available for planning have historically been unable to provide decision-makers with objective, quantitative information from both the top and lower levels of the space program. Instead, decision-makers are forced to turn to top-level, qualitative assessments, disconnected from any of the fundamental, technical details, where inconsistent comparisons and secondary effects often become the …