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Articles 661 - 683 of 683
Full-Text Articles in Aerospace Engineering
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 …
Modular Multi-Scale Assembly System For Mems Packaging, Rakesh Murthy
Modular Multi-Scale Assembly System For Mems Packaging, Rakesh Murthy
Mechanical and Aerospace Engineering Theses - Archive
A multi-scale robotic assembly problem is approached here with focus on mechanical design for precision positioning at the microscale. The assembly system is characterized in terms of accuracy/repeatability and calibration via experiments. The MEMS packaging requirements are studied from an assembly point of view. The tolerance budget of the assembly ranges from 4 microns to 300 microns. The system components include robots, microstages, end-effectors and fixtures that accomplish the assembly tasks. Task assignment amongst this hardware has been accomplished based on precision and dexterity availability. Various end-effectors and fixtures have been designed for use with off-the-shelf hardware (robots and microstages) …
Design And Analysis Of Multi-Functional Laparoscopic Tool, Vadakkapattu Candadai Venkat Raghavan
Design And Analysis Of Multi-Functional Laparoscopic Tool, Vadakkapattu Candadai Venkat Raghavan
Mechanical and Aerospace Engineering Theses - Archive
Laparoscopic tools have been developed over many years, but there is a need for a laparoscopic tool that can be used for multiple purposes without the need to be removed and reinserted in the body. This thesis discusses the design of such a multi-functional laparoscopic tool with the ability to independently actuate grasping and shearing mechanisms, and is modular enough to be easily adapted to robot assisted surgical techniques. The envisioned tool can be divided into three main sections - the surgeon interface, the transmission mechanism, and the end effector. The surgeon interface mainly consists of a handle and two …
Parametric Cycle Analysis For Pulse Detonation Engines, Haider Hekiri
Parametric Cycle Analysis For Pulse Detonation Engines, Haider Hekiri
Mechanical and Aerospace Engineering Theses - Archive
The performance of an ejector-driven pulse detonation engine (PDE) with an afterburner is analytically estimated. In the analysis, the PDE was modeled as a straight tube, closed at the front end and open at the other. A detonation wave starts to travel after it is ignited at the closed end, causing a Chapman-Jouguet detonation wave followed by a Taylor rarefaction to travel to the open end. At that point, rarefaction waves are reflected back to the closed end. The result is a high thrust due to both the primary and secondary flows of the ejector-driven PDE. A theoretical analysis is …
Airy Stress Function For Two Dimensional Inclusion Problems, Dharshini Rao Kavati
Airy Stress Function For Two Dimensional Inclusion Problems, Dharshini Rao Kavati
Mechanical and Aerospace Engineering Theses - Archive
This thesis addresses a problem of finding the elastic fields in a two-dimensional body containing an inhomogeneous inclusion using the Airy stress function which is determined so that the prescribed boundary condition at a far field and the continuity condition of the traction force and the displacement field at the interface are satisfied exactly. All the derivations and solving simultaneous equations are carried out using symbolic software.
Reliability Of Lead-Free Solder Under Cyclic Bending, Fahad Zahedi
Reliability Of Lead-Free Solder Under Cyclic Bending, Fahad Zahedi
Mechanical and Aerospace Engineering Theses - Archive
To characterize particular compositions of lead free solder, four point cyclic bending test was conducted to study the affects of accelerated stress testing on the package to board interconnects. Nine CTBGA packages with 0.5 mm ball pitch and 12 x 12 mm package size were reflowed on 8 layered PWB's using solder balls with lead free composition alloys and different PWB copper pad finishes. The boards were subjected to test conditions based on proposed standards by JEDEC. Strain gages were mounted at different locations on the test boards as well as on bare boards in order to observe the difference …
Failure Analysis Of Composite Laminates With A Hole By Using Finite Element Method, Moumita Roy
Failure Analysis Of Composite Laminates With A Hole By Using Finite Element Method, Moumita Roy
Mechanical and Aerospace Engineering Theses - Archive
Predicting the strength of a given laminate has been extensively studied. There have been several fracture models proposed but still the immense tests of composite laminates are still needed. Different material systems or lay-ups exhibit different failure modes and failure mechanisms. This thesis focuses in investigation of the failure mechanism of the [±?/02]s and [02/±?]s laminates with a hole. ANSYS finite element models with and without a crack in vicinity of hole were developed to investigate the effect of the stress distribution due to the presence of the angle ply crack. The stress concentrations were obtained. It is found that …
Structural Optimization Using Ansys And Regulated Multiquadric Response Surface Model, Ajaykumar Menon
Structural Optimization Using Ansys And Regulated Multiquadric Response Surface Model, Ajaykumar Menon
Mechanical and Aerospace Engineering Theses - Archive
The high computational expense of large non-linear and complex finite element analysis limits or often prohibits the use of conventional codes in engineering design and multidisciplinary optimization. Consequently alternate methods such as Design of experiments (DOE) and Response surface approximation are commonly used to minimize the computational cost of running such analysis and simulation. The basic approach of such methods is to construct a simplified mathematical approximation of the computationally expensive simulation and analysis code, which is then used in place of the original code to facilitate multidisciplinary optimization, design space exploration, reliability analysis etc. When such codes along with …
Investigation Of Pool Boiling Heat Transfer With Nanofluids, Gilberto Moreno
Investigation Of Pool Boiling Heat Transfer With Nanofluids, Gilberto Moreno
Mechanical and Aerospace Engineering Theses - Archive
This investigation conducts pool boiling experiments under saturated conditions (Tsat=60°C) using nanofluids as coolants. Four different nanofluids were tested including zinc oxide (ZnO)-water, aluminum oxide (Al2O3)-water, aluminum oxide (Al2O3)-water+ethylene glycol (ethylene glycol solution) and gold (Au)-water. At saturation (Tsat=60 °C), the pool boiling performance of Al2O3-water and ZnO-water nanofluids were similar. The maximum CHF enhancement as compared to predicted Zuber's [1] CHF evaluated at an equivalent saturation temperature is about 180% for Al2O3-water nanofluids and about 240% for ZnO-water nanofluids. In both cases, no degradation in the boiling heat transfer rate was observed for lower nanoparticle concentrations. The dispersion of …
The Thermal Characteristics Of Liquid-Heat-Spreader, Sang Muk Kwark
The Thermal Characteristics Of Liquid-Heat-Spreader, Sang Muk Kwark
Mechanical and Aerospace Engineering Theses - Archive
The present study is an experimental research of a liquid-heat-spreader (LHS) with saturated water at ~2.29 psia. A LHS, indirect liquid cooling module, was successfully fabricated using thin copper blocks and copper tubes using solder. Three types of LHS, Flat-type, L-type, and T-type, were developed for different orientations and were compared with solid metal blocks such as aluminum and copper. The Flat-type LHS, 100 (W) × 254 (L) × 3 (T) mm3, was designed for vertical orientation. It showed a remarkable thermal performance by dissipating heat flux of 119 W/cm2 with below 100? chip temperature at the typical condition. The …
Numerical Simulation Of Pulse Detonation Phenomena In A Parallel Environment, Prashaanth Ravindran
Numerical Simulation Of Pulse Detonation Phenomena In A Parallel Environment, Prashaanth Ravindran
Mechanical and Aerospace Engineering Theses - Archive
The objective of this work was to develop a parallel algorithm that would be used in the simulation of the detonation process in the chamber of a pulse detonation engine. The emphasis is laid on reducing computation time while maintaining the accuracy of the solution and subsequently developing a numerical solution to be in agreement with real-world physical characteristics of a detonation wave initiation, build-up and progression. The flow is assumed to be unsteady, inviscid and non heat conducting. To adhere to real time effects, the flow equations are coupled with finite rate chemistry and the vibrational energy equation are …
An Approximate Solution To Buckling Of Plates By The Galerkin Method, Yattender Rishi Dubey
An Approximate Solution To Buckling Of Plates By The Galerkin Method, Yattender Rishi Dubey
Mechanical and Aerospace Engineering Theses - Archive
This thesis presents a semi-analytical method to solve the governing differential equation of plates using the Galerkin method. Symbolic algebra software is extensively used to perform necessary calculations. In this thesis, the lateral deflection of a plate is expressed in a series of polynomials each of which satisfies the given homogeneous boundary conditions. The coefficients of these polynomials are found out by the Galerkin method. Symbolic algebra software works best while handling necessary algebra to generate admissible polynomials and build required matrices for solving for the coefficients.This thesis demonstrates the calculation of the lateral load for different plates under different …
Spreading, Solidification And Remelting Behavior Of Liquid Metal Droplets Sequentially Impinging Onto A Metal Substrate, Lister Manohar Pinto
Spreading, Solidification And Remelting Behavior Of Liquid Metal Droplets Sequentially Impinging Onto A Metal Substrate, Lister Manohar Pinto
Mechanical and Aerospace Engineering Theses - Archive
The fluid dynamics and simultaneous solidification of two successive molten metal droplets impacting a flat substrate is investigated numerically. The primary objective is to investigate the effects of initial droplet and substrate temperature, and the latent heat of substrate material, on the spreading, solidification and remelting of molten tin droplets impacting a substrate of the same material. A robust fluid-flow solver that is capable of modeling rapidly deforming free surfaces involving a moving phase-change boundary is employed in the study. The Navier-Stokes equations are solved using a finite volume formulation. A two-step projection method is used to solve for incompressible …
Design Optimization And Synthesis Of Manipulators Based On Various Manipulation Indices, Sandipak Bagchi
Design Optimization And Synthesis Of Manipulators Based On Various Manipulation Indices, Sandipak Bagchi
Mechanical and Aerospace Engineering Theses - Archive
Design optimization of serial manipulators involves striking a balance between an appropriate joint angle and exact link lengths. The optimization technique used in this thesis uses a unique algorithm that optimizes the joint angle through an Inverse Kinematics program. The synthesis problem involves setting up an accurate design length so as to reach a set of given target points inside the workspace without any singularity. The optimization process based on task specification focuses on the maximization of manipulability index, the objective function subjected to link length and joint angle constraints. The results obtained were plotted and animated to visualize the …
Polymer Tube Embedded In-Plane Micropump: Design, Analysis And Fabrication, Ashutosh Kole
Polymer Tube Embedded In-Plane Micropump: Design, Analysis And Fabrication, Ashutosh Kole
Mechanical and Aerospace Engineering Theses - Archive
This thesis presents the design, analysis, and fabrication of a novel polymer tube embedded in-plane micropump. The key component of the proposed micropump is a Parylene polymer tube that is embedded into the trench of a silicon die. Advantages of embedding a Parylene polymer tube are biocompatibility and leakage free environments. The issue of leakage of fluid presented in [1] is eliminated by inserting the polymer tube. The tube itself acts as a diaphragm, which transfers the force and motion of thermal actuators to fluid. The structural analysis and the fabrication of the Parylene tube along with the coupled-field multiphysics …
Study Of Blast Wave Impact On Concrete, Ajit Geevarghese John
Study Of Blast Wave Impact On Concrete, Ajit Geevarghese John
Mechanical and Aerospace Engineering Theses - Archive
The past decade has brought an upsurge of terrorist attacks throughout the world. A common form of attack is bombings employed against a civilian structure. These bombs lead to blast waves resulting from high explosive bursts in air, causing severe structural damage to buildings that often collapse before evacuation is possible. These blast waves subject the buildings to repeated dynamic loading in the form of reflecting shock waves which then finally lead to their destruction. Many studies have been carried out to understand the static loading of these structures. The current study is to protect existing buildings from an explosion. …
Research For Dynamic Seal Friction Modeling In Linear Motion Hydraulic Piston Applications, Brian Edward Suisse
Research For Dynamic Seal Friction Modeling In Linear Motion Hydraulic Piston Applications, Brian Edward Suisse
Mechanical and Aerospace Engineering Theses - Archive
This paper presents a unique physics-based analytic model for dynamic seal friction in hydraulic actuators as a function of cylinder pressure, seal material, piston rod dimensions, piston rod seal gland dimensions, and other influencing factors. Results from a series of friction tests are presented. Finite element analysis of an installed seal is used to predict contact stress between the seal and the gland, providing a normal force against the sealing surface. This information is used to determine coefficients of friction within the test specimen. From the analysis, a pressure-sensitive model is generated. The friction model is overlaid on the test …
Investigation Of Minimum Response For Damage Assessment, Jeffrey Kirk
Investigation Of Minimum Response For Damage Assessment, Jeffrey Kirk
Mechanical and Aerospace Engineering Theses - Archive
Assessment of structural damage based on changes in vibratory response characteristics has been researched for many years, with much attention directed toward the use of modal parameters. Modal responses contribute to form points of local minima in the frequency response of a system. The frequency and amplitude values corresponding to these points of minimum response can be analytically determined, experimentally measured, and shown to exhibit sensitivity to damage. This work was performed to investigate the possible contribution that explicitly targeted minimum response information could provide in a damage detection process. A simple 6-DOF discrete spring-mass system was used to conduct …