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Articles 631 - 660 of 677
Full-Text Articles in Mechanical Engineering
Complete Stress Analysis For Two Dimensional Inclusion Problem Using Complex Variables, Rohan Arun Patil
Complete Stress Analysis For Two Dimensional Inclusion Problem Using Complex Variables, Rohan Arun Patil
Mechanical and Aerospace Engineering Theses - Archive
This thesis addresses the problem of finding stresses and displacements in an infinite plate with a two dimensional circular inclusion with different material properties using complex variable method with biaxial loading acting on it. The complex variable method is used so that the continuity equations of traction force and displacement field are satisfied at the interface .All the complex equations are solved using software Mathematica.
Stress Analysis Of An Ellipsoidal Inclusion, Mahesh Kailas
Stress Analysis Of An Ellipsoidal Inclusion, Mahesh Kailas
Mechanical and Aerospace Engineering Theses - Archive
The focus of the present thesis is to develop a mathematical model to calculate the stresses inside an ellipsoidal inclusion present in an infinitely extended matrix region and to validate the mathematically derived model by the Finite Element Method. To this end, a theoretical model has been developed to predict the stress inside an ellipsoidal inclusion. This model is based on equivalent inclusion method used to evaluate the stress distribution theoretically. Though there have been many theories to predict the stress distribution inside an ellipsoidal inclusion, its numerical validation is new despite its importance. A finite element model of a …
Exploratory Studies Of Convective Flows Due To Arc Tracking, Richard R. Mitchell
Exploratory Studies Of Convective Flows Due To Arc Tracking, Richard R. Mitchell
Mechanical and Aerospace Engineering Theses - Archive
The objective of the research was to develop an understanding of how a flame propagates through an electronic enclosure. FLUENT®, a Navier-Stokes solver, was chosen due to its widespread commercial use, the availability of turbulence models and its ability to handle combustion. The relevance of this study with respect to the aerospace and domestic appliance industry was shown through case reports. Initial observations were made on arc discharges, chemical compounds and their relevance to establishing the flame. Experimental bench tests highlighted the instigating factors for flame ignition. The first round of bench testing revealed that solder node separation played an …
Design, Analysis And Development Of A Morphable Wing Structure For Unmanned Aerial Vehicle Performance Augmentation, Abhijit Hiraman Supekar
Design, Analysis And Development Of A Morphable Wing Structure For Unmanned Aerial Vehicle Performance Augmentation, Abhijit Hiraman Supekar
Mechanical and Aerospace Engineering Theses - Archive
In this research, we propose mechanisms to continuously morph a wing from a lower aspect ratio to a higher and to further extremities of a gull and an inverted-gull configuration. The mechanism comprises of a linear actuator for the extension of the wing and the servo motors to obtain the gull and inverted gull configurations. The initial design and preliminary finite element representation using 3D-beams and plates in ANSYS Classic were the benchmarks to proceed for the detailed structural analysis of the complete wing in ANSYS Workbench. An elliptical pressure distribution at the quarter cord is assumed for the linear …
Design And Implementation Of A Feedback Linearizing Controller And Kalman Filter For A Magnetic Levitation System, John Andrew Henley
Design And Implementation Of A Feedback Linearizing Controller And Kalman Filter For A Magnetic Levitation System, John Andrew Henley
Mechanical and Aerospace Engineering Theses - Archive
The principal investigation undertaken in this research is the development and subsequent implementation of a feedback linearizing nonlinear controller and extended Kalman filter for a laboratory-based Magnetic Levitation (Maglev) device. The Maglev hardware is both highly nonlinear and open-loop unstable in its dynamic response. The control and estimation scheme proposed in this work is first validated using an increasingly sophisticated level of simulations. The control and estimation algorithm had the sensor noise identified using hardware data. Then, the plant noise covariance is tuned using both on-line and off-line hardware data. Additionally, the output of the nonlinear controller is then mapped …
A Generic Stability And Control Tool For Flight Vehicle Conceptual Design: Aeromech Software Development, Gary John Coleman
A Generic Stability And Control Tool For Flight Vehicle Conceptual Design: Aeromech Software Development, Gary John Coleman
Mechanical and Aerospace Engineering Theses - Archive
During the conceptual design (CD) phase, various solution concepts must, and should, be explored to select the best flight vehicle size and configuration in order to meet the mission requirements. As the aerospace industry advances novel aerospace flight vehicle configurations promising larger operational performance and overall efficiency, demanding integrated flight vehicles like the flying wing configuration (FWC) or blending wing body (BWB) are under investigation. Some of these novel configurations rely on novel control effectors (CE) and complex flight control systems in order to obtain the desired performance objectives. Clearly, stability and control plays an important roll in the design …
An Evaluation Of Using Component Mode Synthesis For Structural Models, Richard Lynn Scott
An Evaluation Of Using Component Mode Synthesis For Structural Models, Richard Lynn Scott
Mechanical and Aerospace Engineering Theses - Archive
Structural analysts have used component mode synthesis (CMS), also known as substructuring, for decades to divide large structural models into smaller, more manageable models, and to reduce the size of the associated mathematical problem. Applying CMS can also reduce the front-end effort to build models, even models that are smaller than those for which CMS has typically been applied. This paper presents an evaluation of the accuracy of two smaller substructured models so that analysts might feel confident in applying CMS to gain the benefits. The evaluation starts with an introduction to CMS. Then, CMS is applied to a small, …
Control And Simulation Of Relative Motion For Aerial Refueling In Racetrack Maneuver, Eunyoung Kim
Control And Simulation Of Relative Motion For Aerial Refueling In Racetrack Maneuver, Eunyoung Kim
Mechanical and Aerospace Engineering Theses - Archive
This thesis addresses the problem of controlling the receiver aircraft to achieve a successful aerial refueling. For the performance verification of the controller, a new set of nonlinear, 6-DOF, rigid body equations of motion for the receiver aircraft has been used. The equations are written in terms of state variables that are relative to the reference frame that is attached to, translates and rotates with the tanker aircraft. Furthermore, the nonlinear equations contain the wind effect terms and their time derivatives to represent the aerodynamic coupling involved between the two aircraft. These wind terms are obtained using an averaging technique …
Analysis Of Tapered Laminated Composite Tubes Under Tension And Torsion, Chethana Shankara Rao
Analysis Of Tapered Laminated Composite Tubes Under Tension And Torsion, Chethana Shankara Rao
Mechanical and Aerospace Engineering Theses - Archive
Closed form expressions for determining the displacement and twisting angle of tapered composite tubes are developed. The analytical expressions are developed based on the modified laminated plate theory which includes the tubular wall curvature of the laminate. It is found that the axial deformation and the twisting angle calculated by the current method agree well with the results obtained from the finite element method. The effect of stacking sequence, taper angle and fiber orientations on the axial deformation and twisting angle are studied by using the developed method. It is found that the taper angle plays a significant role on …
Multi-Sensor Fusion Based Control For Autonomous Operations: Rendezvous And Docking Of Spacecraft, Jonathan Bryan Mcdonald
Multi-Sensor Fusion Based Control For Autonomous Operations: Rendezvous And Docking Of Spacecraft, Jonathan Bryan Mcdonald
Mechanical and Aerospace Engineering Theses - Archive
The project considers the problem of motion synchronization of free flying robotic spacecraft and serviceable floating objects in space. The synchronization maneuvers are based on sample and hold nonlinear translational and attitude control laws. GPS pseudorange signals and a vision based sensor unit are modeled to give position measurements; position and velocity estimates are extracted from the measurements based on Extended Kalman Filter models. A sensor data fusion algorithm in the form of a Federated Extended Kalman Filter is implemented that blends the estimates of the individual filters into a global estimate. Nonlinear simulations where a Pursuer spacecraft attempted to …
Flexible Microfluidic Circuit With Embedded In-Plane Valve, Srikar C. Paruchuri
Flexible Microfluidic Circuit With Embedded In-Plane Valve, Srikar C. Paruchuri
Mechanical and Aerospace Engineering Theses - Archive
Recent developments in Microfluidic systems have demonstrated many potential applications related to biology, chemistry and medical sciences. Fluidic manipulation with precise volume control is a basic function in these systems, and microvalves play an important role in control and delivery of the fluid sample. One of the key issues in such valve design is to make large membrane deflections compared to the channel dimension. This thesis reports a flexible microfluidic chip with embedded in-plane valves for fluid manipulation. Silicone elastomer (Polydimethylsiloxane - PDMS) is one of the most suitable materials to fabricate microvalve membranes, because of its low Young's modulus, …
Computer-Aided Patient Specific Treatment Planning Of Cryosurgery For Breast Cancer, Junkyu Jung
Computer-Aided Patient Specific Treatment Planning Of Cryosurgery For Breast Cancer, Junkyu Jung
Mechanical and Aerospace Engineering Theses - Archive
Cryosurgery, which is to destroy tumors by use of localized freezing, is an emerging treatment modality for breast cancer as the size of detectable tumor becomes smaller due to more frequent use of various diagnostic imaging including MRI, CT and mammogram. Although general surgical guideline has been developed and its effectiveness has been demonstrated, cryosurgical protocol should be adjusted for a given patient to accommodate patient-specific variations including tumor size, location and geometry of patient's breast. In this study, a computerized treatment planning tool was developed to aid surgeons to determine surgical parameters considering patient specific diagnostic information. This tool …
Freezing-Induced Microstructural Changes Of Collagen Scaffolds, Jeffrey David Miller
Freezing-Induced Microstructural Changes Of Collagen Scaffolds, Jeffrey David Miller
Mechanical and Aerospace Engineering Theses - Archive
Understanding the effects of freezing on the functional properties of tissues is critical to cryopreservation of native and artificial tissues, and prognosis after cryotherapies. Although investigations have been performed to correlate macroscopic properties such as mechanical properties with freezing parameters, the effects are typically tissue-type dependent and no physical understanding is available to explain these effects. Since the mechanical and optical properties of a tissue are based on the characteristics of its extracellular matrix (ECM), understanding and quantifying these changes could assist in predicting the response a tissue will have to freezing under different circumstances. In this study, the microstructural …
Finite Element Modeling Of Carbon Nanotube Reinforced Polymer Composites And Evaluating Its Thermal Conductivities, Raghuram Basavanahalli
Finite Element Modeling Of Carbon Nanotube Reinforced Polymer Composites And Evaluating Its Thermal Conductivities, Raghuram Basavanahalli
Mechanical and Aerospace Engineering Theses - Archive
High thermal conductivity of carbon nanotubes has motivated us to study and understand the thermal mechanisms in nanocomposites. Though several theoretical models predict a high thermal conductivity for CNT reinforced polymer composites, the experimental validation are not so encouraging. A finite element model of MWNT reinforced nanocomposite is developed based on continuum mechanics approach. The finite element model is a representative volume element (RVE) with single MWNT inclusion. The inclusion is modeled based on the continuum model of MWNT as effective solid fiber [22].The interface resistance between the nanotube and the matrix material is modeled using thermal contact elements. The …
Structural Analysis Of Fiber Reinforced Composite Materials, Cesar Augusto Rojas
Structural Analysis Of Fiber Reinforced Composite Materials, Cesar Augusto Rojas
Mechanical and Aerospace Engineering Theses - Archive
A study of fiber reinforced composite structures is conducted .This study includes laminate analysis, analysis of laminated composite beams and parametric study of composite beams. Finite element analysis for each beam model is conducted to verify the results obtained by analytical model. The analysis of the laminated beams in this study covers: 1. beam with a solid rectangular cross-section subjected to a transverse load 2. beam with a I-section under bending 3. beam with a squared tubular section under bending 4. beam with truss section under bending One of the principal purposes of this thesis is to create a user …
Design And Optimization Of Heat Spreaders And Selection Of Fan In Laptop, Kranthi Kumar Manne Sambaiah
Design And Optimization Of Heat Spreaders And Selection Of Fan In Laptop, Kranthi Kumar Manne Sambaiah
Mechanical and Aerospace Engineering Theses - Archive
Technical advancements lead to the need for faster processors and reduced sizes in electronic systems. The urge for faster and compact systems leads to two major problems. Firstly over heating of chips which degrade the chip performance and secondly formation of heat spots on the surface which makes the user uncomfortable. Thermal management engineers, as a result have a major challenge in improving the cooling systems. In this research project simulation using the thermal modeling tool selected is Icepak. The prototype model of the laptop is designed, boundary conditions are applied and analysis is done. The results so obtained in …
Thermal Enhancement Of Stacked Dies Using Thermal Vias, Baekyoung Sung
Thermal Enhancement Of Stacked Dies Using Thermal Vias, Baekyoung Sung
Mechanical and Aerospace Engineering Theses - Archive
Following Moore's law, the number of transistors on a die continues to rise and has recently exceeded a billion on high end processors. In light of the convergence of technology, power requirements is becoming a serious concern even on low density interconnect systems such as cellular phones and personal digital assistants. Also, in order to minimize foot prints, the recent trend in packaging is stacking. The stacking, however, creates challenges in cooling and especially if one is to include logic in the stack. The primary heat flow path for stacking is through the substrate and as the number of stacks …
Uncertainty Characterization Of Orbital Debris, Jolanta Matusewicz
Uncertainty Characterization Of Orbital Debris, Jolanta Matusewicz
Mechanical and Aerospace Engineering Theses - Archive
The increase of orbital debris in the low Earth orbit is a concern for the space industry. Spacecraft and satellites are at risk of collision with orbital debris. Collisions can damage sensitive components or result in catastrophic failure. Organizations such as the United States Space Command are responsible for tracking orbital debris using ground based sensor sites located around the world. Orbit determination techniques are used to estimate the position and velocity of the orbit using range, azimuth, and elevation measurements obtained from the sensors. Nine sensors from the Space Surveillance Network are simulated to track a debris object in …
Analysis And Design Of A Piezoelectric Micro-Actuator, Po-Shiun Chen
Analysis And Design Of A Piezoelectric Micro-Actuator, Po-Shiun Chen
Mechanical and Aerospace Engineering Theses - Archive
Micro-grippers are usually fabricated of silicon using traditional semiconductor manufacturing processes and actuated based on thermal energy input causing their temperature to substantially increase and render unsuitable for certain applications such as biological tissue handling. In this research work, the design of a micro-gripper using piezoelectric ceramics (PZT) is presented as an alternative to silicon based micro gripper. The design procedure utilized ANSYS, a Finite Element Method based software tool to verify simple PZT models and subsequently evaluate the stroke for a family of configurations. The configurations were further explored and optimized considering that the fabrication would be performed using …
Mems Packaging: Fluxless Soldering And Reliability Assessment, Amit L. Patil
Mems Packaging: Fluxless Soldering And Reliability Assessment, Amit L. Patil
Mechanical and Aerospace Engineering Theses - Archive
This thesis presents process development and reliability assessment of the fluxless packaging of the MEMS devices. This packaging consists of metallized Kovar package with side wall of same material and circular holes for the optical fiber interconnect between the microstructures on the chip and the macro-environment. The back of the MEMS chip and the soldering part of the optical fiber is metallized. A thin solder perform is placed between the chip and the metallized package to attach the chip and a circular solder perform is used to attach the fiber to the metal substrate. The soldering process is fluxless hence …
Spacecraft Formation Flight: Analysis Of The Perturbed J2-Modified Hill-Clohessy-Wiltshire Equations, Jeffery Scott Ginn
Spacecraft Formation Flight: Analysis Of The Perturbed J2-Modified Hill-Clohessy-Wiltshire Equations, Jeffery Scott Ginn
Mechanical and Aerospace Engineering Theses - Archive
With the recent technological gains made in satellite design and manufacturing, there has been great interest in utilizing a cluster of satellites to perform the same tasks performed by larger satellites. Historically, this has been done utilizing the Clohessy-Wiltshire equations, or the Hill's equations, as a benchmark for understanding the physics of the relative motion between two spacecraft. A variety of different models have been derived and implemented to study the relative motion dynamics since the Hill-Clohessy-Wiltshire (HCW) equations. Some of these models, like the HCW equations, are linearized and have analytical solutions. These models make the underlying physics due …
Effect Of Crac Location On A Fixed Rack Layout Of A Data Center, Vishwas Bedekar
Effect Of Crac Location On A Fixed Rack Layout Of A Data Center, Vishwas Bedekar
Mechanical and Aerospace Engineering Theses - Archive
Microprocessor driven escalation of thermal management needs has resulted in significant cooling challenges at the data center facility level, which can house thousands and tens of thousands of heat producing processors. Raised floor air ducting is the most common configuration, where chilled air from the air conditioning units is forced into the room via a under floor plenum and through perforated tiles on the floor. The hot air from the racks finds its way to the top of the air conditioning units and is then cooled and blown into the under floor plenum. The temperature at inlet of the racks …
Enhancement Of Cryoinjury By Use Of Eutectic Crystallization Of An Amino Acid Adjuvant, Chuo-Li Wang
Enhancement Of Cryoinjury By Use Of Eutectic Crystallization Of An Amino Acid Adjuvant, Chuo-Li Wang
Mechanical and Aerospace Engineering Theses - Archive
Enhancement of cryoinjury by use of eutectic formation was investigated to improve the efficacy of cryosurgery. Although the enhancement of cryoinjury associated with eutectic crystallization of sodium chloride (NaCl) has been demonstrated, its advantage can be maximized with adjuvants which are biocompatible and have higher eutectic temperature than NaCl. In this study, the feasibility of glycine, which is less toxic and have higher eutectic temperature than NaCl, was tested. Two groups of MCF-7 human breast cancer cell were suspended in isotonic saline with glycine, then were frozen and thawed on a directional solidification stage in the same protocol except that …
Parameters Affecting Critical Heat Flux Of Nanofluids: Heater Size, Pressure Orientation And Anti-Freeze Addition, Madhav Rao Kashinath
Parameters Affecting Critical Heat Flux Of Nanofluids: Heater Size, Pressure Orientation And Anti-Freeze Addition, Madhav Rao Kashinath
Mechanical and Aerospace Engineering Theses - Archive
This research aims at investigating the effect, heater size, pressure, heater orientation and effect of anti-freeze addition on critical heat flux of nanofluids which have shown large potentials as coolants for high power generating uses. Nanofluids have shown about ~180 - 200% enhancement in the critical heat flux values. The effect of heater size employing three different sized heaters yielded about ~180% enhancement over pure water. The effect of pressure on critical heat flux investigated by testing nanofluids at three pressures showed ~240% increase in critical heat flux. Surface orientation effect on critical heat flux carried out for a 2 …
Development Of Three Block Thermal Compact Model And Verification Of Modified Linear Superposition Technique For Stacked Die, Suresh G. Nikalaje
Development Of Three Block Thermal Compact Model And Verification Of Modified Linear Superposition Technique For Stacked Die, Suresh G. Nikalaje
Mechanical and Aerospace Engineering Theses - Archive
Over the last few years an impressive amount of progress has been achieved in the field of compact modeling of chip packages. But available compact modeling methods could not address the issue of limitation on the mesh statistics which is major concern while modeling in FEM softwares with limited number of nodes and elements. It is not possible to attain convergence of solution for thermal simulation of detailed model with the constraint on the number of nodes and elements. In this thesis, a simple and straight forward three block (3B) compact modeling method is developed. 3B compact modeling method has …
Air Jet Impingement For Levitation, James Frederick Huber
Air Jet Impingement For Levitation, James Frederick Huber
Mechanical and Aerospace Engineering Theses - Archive
Traditional part acquisition methods such as vacuum cups and robotic grippers do not meet the handling needs of truly fragile materials, because both of these methods require surface contact. An alternative to these traditional approaches is the use of air jet impingement for levitation. This technique confines impinged air to a thin disk above the target to form radial diffuser. The Bernoulli Effect causes a pressure difference between the fast-moving impinged air above the surface and ambient air below it. The net pressure difference is sufficient to lift objects weighing more than one kilogram using standard shop air. This method …
Frequency Response Approximation Methods Of The Dissipative Model Of Fluid Transmission Lines, John King
Frequency Response Approximation Methods Of The Dissipative Model Of Fluid Transmission Lines, John King
Mechanical and Aerospace Engineering Theses - Archive
This thesis introduces an accurate and efficient method of obtaining a linear approximation for a nonlinear model of a complete fluid transmission line system using Matlab® Signal Processing Toolbox and Symbolic Math Toolbox programs. This technique is then packaged in a Graphical User Interface program to streamline the process of analyzing a total system. The method of approximating the frequency response of a fluid transmission line with a rational polynomial transfer function using the Matlab® 'invfreqs' least squares curve fitting algorithm has already been introduced. This research improves the technique by applying the 'invfreqs' command to a total system rather …
Structural Optimization Using Femlab And Smooth Support Vector Regression, Divija Odapally
Structural Optimization Using Femlab And Smooth Support Vector Regression, Divija Odapally
Mechanical and Aerospace Engineering Theses - Archive
In recent years support vector machine (SVM) has been emerging as a popular tool for function approximation. Application of SVM for approximation of mathematical functions and complex engineering analysis has been represented by Palancz et al and Clarke et al, respectively. However the training of the original SVM involves the solution of a quadratic programming (QP) problem. This makes the application of SVM to large problem computationally expensive. To circumvent this difficulty, Lee et al developed a more efficient SVM formulation namely epsilon-SSVR which drastically improved the training efficiency of SVM. In this research the SSVR is used to build …
Finite Element Analysis Of Moisture And Thermal Induced Stress In Flip Chip Packages, Santanu Ghosh
Finite Element Analysis Of Moisture And Thermal Induced Stress In Flip Chip Packages, Santanu Ghosh
Mechanical and Aerospace Engineering Theses - Archive
The process of moisture absorption and subsequent hygroswelling stress development is a cause of concern in the IC packaging industry. Also thermal stresses developed during the lead free reflow process with a high peak temperature (~ 250oC) add to the problem. In Flip Chip packages, the related effects are high shear stresses at the multilayer interfaces and normal stresses in solder balls. This can lead to phenomenon like delamination at the interfaces and UBM opening. In this work we have made an attempt to simulate the moisture absorption process, subsequent hygroswelling stress development, and thermal stress generated during reflow using …
Viscoplastic Finite-Element Simulation To Predict The Solder Joint Fatigue Life Of Different Flash Memory Die Stacking Architectures, Yong Je Lee
Mechanical and Aerospace Engineering Theses - Archive
This thesis focuses on the viscoplastic finite-element simulation to predict the solder joint fatigue life of different die stacking architectures for flash memory products. Four different stacked package architectures were evaluated as follows: pyramid, rotated, and spacer stacking, while interconnection (solder joint) was held constant. Number of dies for all four stacking configurations were varied from three, five and seven. To keep the package height constant, the die and die attach thickness were varied and the resulting effects on the stresses were investigated. A quarter and half symmetry model of stacked flash package are generated using ANSYS APDL script. The …