Mechanical Engineering Commons^™

Finite Element Analysis Of Forging, Aditya Ashok Battin

Mechanical and Aerospace Engineering Theses - Archive

Numerical modeling and simulation of metal forming is very effective in saving production time, effort and economy and has thus gained prominence in many industries all over the world. In metal-forming finite element analysis, software like Deform, Qform, Forge, Simufact, Hyperform are used extensively for the forming analysis. Apart from having narrow applications, these softwares are expensive. The object of this study was to examine the robustness of general package softwares in regards to forging. Software such as Abaqus and Ansys LSDyna were used to simulate the forging process. The case examined was that of a circular metal disc restrained …

Multi Objective Optimization Of Graphite Heat Spreader For Portable Systems Application, Arijit Banerjee

Mechanical and Aerospace Engineering Theses - Archive

The advancement made in portable electronic systems has primarily been due to miniaturization of electronic systems. This in turn leads to an increase in power density which leads to higher temperatures and formation of hot spots. There is a temperature specification of system surfaces for human comfort (such as the surface close to a keyboard on laptops). Challenge in cooling portable devices is that there is not enough room to accommodate heat sinks. It is therefore important to have heat spreaders that can transfer the heat from critical devices to regions where cooling is available. Traditionally, copper has been the …

A Numerical Study On The Dynamics Of Bubble Growth And Detachment From An Orifice, Sheshi Kumar Takkallapally

Mechanical and Aerospace Engineering Theses - Archive

The study of bubble formation from an orifice finds numerous industrial applications which include bubble acoustics in ocean physics and chemical reactors. Numerical simulations have been performed to investigate the dynamics of bubble formation, growth and detachment from an orifice. The full transient Navier - Stokes equation is solved in a two-dimensional axi-symmetrical coordinate system. The surface tension implementation algorithm known as the Pressure Boundary Method (PBM) is used to model the surface tension. The robustness of PBM method on Two-Phase flows with different conditions has been shown. The results achieved by numerical simulations have been compared with the available …

Heat Transfer Analysis Of A Pulse Detonation Engine, Neelima Kalidindi

Mechanical and Aerospace Engineering Theses - Archive

A thermal analysis of the effect of sensible heat release on the walls of the detonation chamber for stoichiometric mixtures of hydrogen/air, octane/air and octane/oxygen was presented. The detonation tube was assumed to operate at 20 Hz and cooled by a water jacket to dissipate the heat from the walls which ensures the effective operation for a longer period. Wall material was assumed to be made of copper because of its high thermal conductivity.The study showed a slow temperature rise along the walls of the combustion chamber for multiple pulses. It can be concluded that due to the space-time averaging …

Thermal Conduction Equations For A Medium With An Inclusion Using Galerkin Method, Thiagarajan Sivalingam

Mechanical and Aerospace Engineering Theses - Archive

The Galerkin method is used to semi-analytically solve the heat conduction equation in non-homogeneous materials. The problem under deliberation is a square plate with a circular inclusion having different thermal conductivities. A generalized procedure that involves the Galerkin method and formulation of the final solution in terms of the procured base functions is adopted. The Galerkin method basically involves expressing the given boundary value problem in terms of a standard mathematical relation, generating a set of continuous base functions, formulating the matrix equation, and determining the solution.For the non-homogeneous material, a set of base functions for the plate and inclusion …

Structural Optimization Using Ansys Classic And Radial Basis Function Based Response Surface Models, Vijay Krishna

Mechanical and Aerospace Engineering Theses - Archive

This thesis describes a methodology to develop an effective and simple structural optimization method using Response Surfaces. It also further demonstrates how these Response Surfaces can then be utilized for further Multi Objective Optimization. The true or exact responses were calculated using Ansys Classic while the codes for the training and simulation of Response Surface is pro-grammed in Matlab. Initially we used a Halton sequence to generate a DOE of the design variables. Then we used Ansys Classic to generate the exact responses. Once the responses were imported the Response Surface are generated using a RBF approximation model. This RBF …

Electrowetting On Dielectric (Ewod) Digital Microfluidics For Electronic Hotspot Cooling, Govindraj Shreyas Bindiganavale

Mechanical and Aerospace Engineering Theses - Archive

Electronics cooling was a field dominated by bulky and heavy heat sinks, heat pipes and fans for decades. Lately, the size of the electronic components has decreased to a substantial extent with an increase in performance. This has fuelled a need for smaller, lighter, yet efficient cooling systems. A lot of research has been done to build innovative cooling solutions which satisfied most of the requirements as stated above. Some of them still have limitations like use of the right coolants and design challenges. Digital microfluidics is one field which can solve all these issues by providing a simple, reliable …

A Unified Analysis Of Stiffener Reinforced Composite Beams With Arbitrary Cross-Section, Gianfranco Rios

Mechanical and Aerospace Engineering Dissertations - Archive

A number of methods are available to analyze the laminated composite beams using smear property of laminate stiffness ignoring unsymmetrical behavior of laminates. Some include their effect of laminate but did not include the unsymmetrical effect of the cross-section of the beam. On the other hand, using finite element method to analyze the beam is dependent on the structural configurations including the laminate lay-up sequence. An analytical method was developed from lamination theory in order to study the structural response of composite laminated beams. The present method is capable of predicting the axial and bending stiffnesses, the centroid location, and …

A Generic Methodology For Flight Test And Safety Evaluation At Conceptual Design, Amit R. Oza

Mechanical and Aerospace Engineering Theses - Archive

The current research is dedicated to the application of a simulation suite that emulates flight testing and is applicable to the aircraft conceptual and preliminary design environment. The configuration concept available for study is an unmodified Cessna Citation X. The research goal is to arrive at a systematic process that reduces aircraft design risk while creating transparency for the manager and engineer during product life-cycle simulation. When integrating the discipline of flight test emulation into the development methodology, the objective is to complement and enrich the design simulation through a correct representation of flight safety relevant disciplines like aircraft certification, …

High Temperature Microporous Coatings: The Effects Of Wetting And Wicking On Nucleate Boiling And Chf, Ross Evan Pivovar

Mechanical and Aerospace Engineering Theses - Archive

Porous coatings have long been a method to enhance boiling heat transfer. Previous researchers have thoroughly explained most of the physics behind the enhancement, but some holes still exist. Correlations, setup to predict nucleate boiling, are often only accurate in specific scenarios. CHF correlations that take into account wettability do not consider microstructure changes that decrease contact angle, but do not enhance CHF. A solution to these problems is presented via the wicking and wetting of liquid on a porous surface. CHF is found to be enhanced with increases in wicking speeds and flow rate. Wetting, measured by apparent contact …

Numerical Modeling Of The Constraint Effects On Cleavage Fracture Toughness, Sunil Prakash, Xiaosheng Gao, T. S. Srivatsan

Mechanical Engineering Faculty Research

Cleavage fracture has been an important subject for engineers primarily because of its catastrophic nature and consequences. Experimental studies of cleavage fracture did reveal a considerable amount of scatter and provided evidence of noticeable constraint effects. This did provide the motivation for the development of statistical-based and micromechanics-based methods in order to both study and analyze the problem. The Weibull stress model, which is based on the weakest link statistics, uses two parameters (m and σ u) to effectively describe the inherent distribution of the micro-scale cracks once plastic deformation has occurred and to concurrently define the relationship between the …

Robust Estimation And Adaptive Guidance For Multiple Uavs' Cooperation, Randal Allen

Electronic Theses and Dissertations

In this paper, an innovative cooperative navigation method is proposed for multiple Unmanned Air Vehicles (UAVs) based on online target position measurements. These noisy position measurement signals are used to estimate the target's velocity for non-maneuvering targets or the target's velocity and acceleration for maneuvering targets. The estimator's tracking capability is physically constrained due to the target's kinematic limitations and therefore is potentially improvable by designing a higher performance estimator. An H-infinity filter is implemented to increase the robustness of the estimation accuracy. The performance of the robust estimator is compared to a Kalman filter and the results illustrate more …

Topology Optimization Using Hyper Radial Basis Function Network, Aditya P. Apte

Mechanical and Aerospace Engineering Dissertations - Archive

Topology optimization has been conventionally used in automobile and aerospace industries to produce lightweight structures for minimum compliance or maximum fundamental frequency. Today, topology optimization finds application in solving diverse types of problems ranging from medicine to consumer products. Popular continuum based method SIMP fails to provide global solution due to too many variables involved. In this work, a novel hyper radial basis function network is presented as topology description function. The proposed approach provides drastic reduction in number of design variables involved in topology optimization. This makes the use of heuristic global solution possible. Parallel processing, reanalysis formulation and …

Optimal-Control Theoretic Methods For Optimization And Regulation Of Distributed Parameter Systems, Jennifer Dawn Goss

Mechanical and Aerospace Engineering Dissertations - Archive

Optimal control and optimization of distributed parameter systems are discussed in the context of a common control framework. The adjoint method of optimization and the traditional linear quadratic regulator implementation of optimal control both employ adjoint or costate variables in the determination of control variable progression. As well both theories benefit from a reduced order model approximation in their execution. This research aims to draw clear parallels between optimization and optimal control utilizing these similarities. Several applications are presented showing the use of adjoint/costate variables and reduced order models in optimization and optimal control problems. The adjoint method for shape …

Transient Flow Analysis Of Filling In Pulse Detonation Engine, Veera Venkata Suneel Jinnala

Mechanical and Aerospace Engineering Theses - Archive

The Pulse Detonation Engine (PDE) is considered to be a propulsion system of future air vehicles. The objective of the present study is to model an efficient inlet system for filling the detonation tube completely with the fuel/air mixture. In the present study the filling processes is modeled numerically using CFD code FLUENTTM. Calculations for the gas flow are carried out by solving the Navier-Stokes equations coupled with the k- ? turbulence model. Five different inlet configurations were proposed and simulated in both two-dimensionally and three-dimensionally. The model with an orifice plate at the inlets ensured the desired optimum results. …

Guidance Of Receiver Aircraft To Rendezvous With Tanker In The Presence Of Wind, Jane-Wit Kampoon

Mechanical and Aerospace Engineering Theses - Archive

This thesis work addresses the problem of aircraft rendezvous in the presence of prevailing wind for automated aerial refueling operations. A modified point-parallel rendezvous procedure is defined. The tanker aircraft performs a racetrack maneuver along a pre-specified refueling orbit. The receiver aircraft enters the refueling area through a fixed point and flies along the refueling line that is aligned with on of the straight legs of the race track. It is the responsibility to meet the tanker at the rendezvous point. A virtual target is used to define the trajectory of the refueling orbit. A nonlinear guidance algorithm is used …

Experimental Investigation Of Flow Boiling And Spray Cooling On Enhanced Surfaces In Fc-72, Gilberto Morenp

Mechanical and Aerospace Engineering Dissertations - Archive

In this study the effect of a recently developed, thermally conductive microporous coating on flow boiling and spray cooling performance was studied using FC-72 as the working fluid. The overall goal is to further increase heat transfer in forced convection systems and in doing so, provide a viable option for future cooling applications. In flow boiling, the coating increased heat transfer coefficients by as much as 400% and produced values exceeding 40,000 W-m-2 K-1. This enhancement is believed to be a result of both an increase in active nucleation sites and a decrease of the superheated liquid layer. It is …

Structural Analysis And Active Vibration Control Of Tetraform Space Frame For Use In Micro-Scale Machining, Kevin Knipe

Electronic Theses and Dissertations

This research thesis aims to achieve the structural analysis and active vibration damping of the Tetraform machining structure. The Tetraform is a space frame made up of four equilateral triangles with spherical masses at the four vertices. This frame was originally developed for grinding of optical lenses and is now being adapted for use in micro-precision milling. The Tetraform is beneficial to the milling process due to its exceptionally high dynamic stiffness characteristics, which increases the machining stability and allows for higher material removal rates and accuracy. However, there are still some modes of vibration that are critical to the …

Tertiary Creep Damage Modeling Of A Transversely Isotropic Ni-Based Superalloy, Calvin Stewart

Electronic Theses and Dissertations

Anisotropic tertiary creep damage formulations have become an increasingly important prediction technique for high temperature components due to drives in the gas turbine industry for increased combustion chamber exit pressures, temperature, and the use of anisotropic materials such as metal matrix composites and directionally-solidified (DS) Ni-base superalloys. Typically, isotropic creep damage formulations are implemented for simple cases involving a uniaxial state of stress; however, these formulations can be further developed for multiaxial states of stress where materials are found to exhibit induced anisotropy. In addition, anisotropic materials necessitate a fully-developed creep strain tensor. This thesis describes the development of a …

Study Of Film Cooling Effectiveness: Conical, Trenched And Asymmetrical Shaped Holes, Humberto Zuniga

Electronic Theses and Dissertations

Film cooling is a technique whereby air from the compressor stage of a gas turbine engine is diverted for cooling purposes to parts, such as the turbine stage, that operate at very high temperatures. Cooling arrangements include impingement jets, finned, ribbed and turbulated channels, and rows of film cooling holes, all of which over the years have become progressively more complex. This costly, but necessary complexity is a result of the industry's push to run engines at increasingly higher turbine inlet temperatures. Higher temperatures mean higher efficiency, but they also mean that the turbine first stage operates hundreds of degrees …

Flow Visualization In Microfluidic Expansion And Mixing, Ehsan Yakhshi-Tafti

Electronic Theses and Dissertations

Micro particle image velocimetry (microPIV) is a non-intrusive tool for visualizing flow in micron-scale conduits. Using this investigative instrument, two experimental studies were performed to understand flow behaviors in microfluidic channels - a sudden expansion step flow and laminar velocity profile variation in diffusion driven mixing. First, flow in a backward facing step feature (1:5 expansion ratio) in a microchannel was taken as the subject of microPIV flow visualization. The onset and development of a recirculation flow was studied as a function of flow rate. This flow pattern was further used to investigate two major parameters affecting microPIV measurements; the …

Study Of The Hydrodynamics Of Droplet Impingement On A Dry Surface Using Lattice Boltzmann Method, Xin Gu

Electronic Theses and Dissertations

In this work, a two-phase lattice Boltzmann method (LBM) approach is implemented to investigate the hydrodynamic behavior of a single droplet impingement on a dry surface. LBM is a recently developed powerful technique to compute a wide range of fluid flow problems, especially in applications involving interfacial dynamics and complex geometries. Instead of solving the non-linear Navier-Stokes equations, which are complicated partial differential equations, LBM solves a set of discretized linear equations, which are easy to implement and parallelize. The fundamental idea of LBM is to recover the macroscopic properties of the fluid which obeys Navier-Stokes equations, by using simplified …

Characterization Of A Hydrogen-Based Synthetic Fuel In A Shock Tube, Troy Flaherty

Electronic Theses and Dissertations

Shock-tube experiments were performed with syngas mixtures near atmospheric pressure with varying equivalence ratios behind reflected shock waves. Pressure and hydroxyl radical (OH*) emission traces were recorded and used to calculate ignition delay time for a single mixture at equivalence ratios of [phi ]=0.4, 0.7, 1.0, and 2.0 over a range of temperatures from 913-1803 K. The syngas mixture was tested at full concentration as well as with 98% dilution in Argon. The full concentration mixtures were used to compare ignition delay time measurements with the theoretical calculations obtained through the use of chemical kinetics modeling using the Davis et …

Characterization Of An Inline Row Impingement Channel For Turbine Blade Cooling Applications, Mark Ricklick

Electronic Theses and Dissertations

Gas turbines have become an intricate part of today's society. Besides powering practically all 200,000+ passenger aircraft in use today, they are also a predominate form of power generation when coupled with a generator. The fact that they are highly efficient, and capable of large power to weight ratios, makes gas turbines an ideal solution for many power requirement issues faced today. Designers have even been able to develop small, micro-turbines capable of producing efficient portable power. Part of the turbine's success is the fact that their efficiency levels have continuously risen since their introduction in the early 1800's. Along …

Renewable Energy Resources And Technologies Applicable To Ireland, Fergal O'Rourke, Fergal Boyle, Anthony Reynolds

Articles

The energy consumed in Ireland is primarily achieved by the combustion of fossil fuels. Ireland’s only indigenous fossil fuel is peat; all other fossil fuels are imported. As well as fossil fuels continually becoming more expensive, their use as an energy source also has a negative impact on the environment. Ireland’s energy consumption can be separated into 3 divisions; transportation, electricity generation and heat energy. Ireland however has a vast range of high quality renewable energy resources. Ireland has set a target of 33% of its electricity will be generated from renewable sources by 2020[1]. The use of biomass, wind …

Identification Of Multiple Oscillation States Of Carbon Nanotube Tipped Cantilevers Interacting With Surfaces In Dynamic Atomic Force Microscopy, Mark Strus, Arvind Raman

Birck and NCN Publications

Carbon nanotubes (CNTs) have gained increased interest in dynamic atomic force microscopy (dAFM) as sharp, flexible, conducting, nonreactive tips for high-resolution imaging, oxidation lithography, and electrostatic force microscopy. By means of theory and experiments we lay out a map of several distinct tapping mode AFM oscillation states for CNT tipped AFM cantilevers: namely, noncontact attractive regime oscillation, intermittent contact with CNT slipping or pinning, or permanent contact with the CNT in point or line contact with the surface while the cantilever oscillates with large amplitude. Each state represents fundamentally different origins of CNT-surface interactions, CNT tip-substrate dissipation, and phase contrast …

Systematic Functional And Object-Oriented Product Design Frameworks, Jen-Chi Wu

Doctoral Dissertations

"The existing co-design methods of mechatronic products focus on co-design of mechanical and electronic components or co-design of computer hardware and software components. There exist no effective co-design methods for mechanical, electronic and software components at the concept design stage. The research objective of this dissertation work is to develop more effective systematic product design approaches for co-design of mechatronic products. Three innovative functional and object-oriented integrated design frameworks and one virtual prototyping application, which leverages on these three design frameworks, have been developed for co-design of mechatronic products. The three frameworks are: I) Hierarchical Object-Oriented Functional Modeling Framework, 2) …

Numerical Study Of Encapsulated Phase Change Material (Epcm) Slurry Flow In Microchannels, Sarada Kuravi

Electronic Theses and Dissertations

Heat transfer and flow characteristics of phase change material slurry flow in microchannels with constant heat flux at the base were investigated. The phase change process was included in the energy equation using the effective specific heat method. A parametric study was conducted numerically by varying the base fluid type, particle concentration, particle size, channel dimensions, inlet temperature, base heat flux and melting range of PCM. The particle distribution inside the microchannels was simulated using the diffusive flux model and its effect on the overall thermal performance of microchannels was investigated. Experimental investigation was conducted in microchannels of 101 [micro]m …

Automated Network Planning For Industrial Ethernet Networks, Holger Machens

Theses

Engineers usually use computer aided methods to ease the increasingly complex planning task of automation plants. One such computer aided method for automated planning of Industrial Ethernet networks under given network QoS requirements is presented in this thesis. The method is based on partitioning the given set of network nodes according to specified communication relationships between the nodes, thereby creating subsets of nodes which are joined using given networking algorithms. Several networking algorithms may be applicable for each subset of nodes and any complete solution is a combination of several partial solutions, one for each subset of nodes. Enumeration through …

Optimisation Of Heat Sink Design, Kevin Moore

Theses

In the field of electronics cooling and more specifically processor cooling, the ability to cool a micro-chip is becoming a major issue. Power dissipation in home and office computers has risen from 30W to over 120W in the past 10 years, forcing heat sink designers to search for new ideas in the design of their heat spreaders.

This thesis studies in detail the fundamental technical designs used for modern day processor cooling. Using Computational Fluid Dynamics (CFD), various different pin/fin shapes were analysed to determine which yielded maximum heat transfer and contact area with forced air flow. Elliptical and teardrop …