Aerospace Engineering Commons^™

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

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

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.

Arc-Heated Gas Flow Experiments For Hypersonic Propulsion Applications, Christopher Matthew Roseberry

Mechanical and Aerospace Engineering Dissertations - Archive

Although hydrogen is an attractive fuel for a hypersonic air-breathing vehicle in terms of reaction rate, flame temperature, and energy content per unit mass, the substantial tank volume required to store hydrogen imposes a drag penalty to performance that tends to offset these advantages. An alternative approach is to carry a hydrocarbon fuel and convert it on-board into a hydrogen-rich gas mixture to be injected into the engine combustors. To investigate this approach, the UTA Arc-Heated Wind Tunnel facility was modified to run on methane rather than the normally used nitrogen. Previously, this facility was extensively developed for the purpose …

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 …

Experimental Characterization Of Femtosecond Laser Micromachining For Silicon Mold Fabrication And Hot Embossing For Polymer Microreplication, Sunil Ranganath Belligundu

Mechanical and Aerospace Engineering Dissertations - Archive

Hot embossing is a fabrication technique employed for replicating microfeatures on a polymer surface that was primarily developed to fabricate MEMS devices for microfluidic applications. This manuscript deals with characterization of the femtosecond laser micromachining (FLM) and hot embossing (HEMM) processes for master mold fabrication on silicon and polymer replication respectively. Given the required size of the features to be fabricated or replicated, process parameters for FLM can be determined using the derived empirical equations, process parameters for the HEMM process can be established using the characteristic plots. A novel two-stage embossing process is developed and introduced that employs polymer …

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

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 …

A Qualitative Modeling Method For Platform Design, Michael Van Wie, Robert B. Stone, Asli Sahin, Janis Terpenny, Fabrice Alizon, Steve Shooter, Timothy Simpson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The development of a collection of related products sharing a common platform represents an important approach in modern product design. an ongoing problem is the application of design methods toward a limited set of evolving product data and archived design knowledge to search and explore alternative platform options. with the goal of maximizing the reuse of end item artifacts and supply chain elements, we propose a design modeling method using basic qualitative relationships among relevant performance, design, and noise parameters in the system of interest. by using qualitative models related to multiple levels of design data, the method provides a …

Performance Measurements Of Direct Air Injection In A Cavity-Based Flameholder For A Supersonic Combustor, Scott G. Edens

Theses and Dissertations

For several years the Air Force Research Lab Propulsion Directorate has been studying the difficulties in fueling supersonic combustion ramjet engines with hydrocarbon based fuels. Recent investigations have focused on the use of direct air injection into a directly-fueled cavity-based flameholder. Direct air injection has been shown qualitatively to be a valuable tool for improving cavity combustion. Little quantitative data is available that characterizes the performance of cavity-based flameholders. The objective of this research was to quantitatively determine the specific advantages and disadvantages of the direct air injection scheme. This was accomplished via intrusive probing into a supersonic free stream …

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

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 …

Repeatable Nanostructures In Dielectrics By Femtosecond Laser Pulse Trains, Lan Jiang, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Using the plasma model recent developed by the authors, this study predicts the existence of a constant ablation-depth zone with respect to fluence in femtosecond laser ablation of dielectrics, which has also been observed experimentally. It is found that the value of the constant ablation depth is significantly decreased by the pulse train technology. Repeatable nanostructures can be achieved with the parameters in the constant ablation-depth zone of a femtosecond pulse train, even when the laser system is subject to fluctuations in fluences.

Adaptive Control Of A Projectile Fin Using Piezoelectric Elastic Beam, Smitha Mani, Sahjendra N. Singh, Surya Kiran Parimi, Woosoon Yim, Mohamed B. Trabia

Mechanical Engineering Faculty Research

No abstract provided.

An Experimental Investigation Of Ionization Of Supersonic Air By A Corona Discharge, Udyavar S. Satyanand

Mechanical and Aerospace Engineering Dissertations - Archive

A technique is developed to ionize supersonic air flow in a shock tube by a weak corona discharge. The driven section of the tube is open to the atmosphere. The shock propagates in the driven section at about 1 km/s by means of an area contraction near the downstream end of the driven section. Air is ionized by a unipolar corona discharge device comprising of a sharp-edged wedge as a high-field electrode inserted in a 41.25 mm (2 in.) ID tube that forms a low-field electrode. The device requires less than 0.5 W. A ring probe, downstream of the corona …

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

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

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

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

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

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

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

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 …

Introduction To Product Design And Innovation: A Cross Disciplinary Mini Curriculum, Patricia Backer, Seth Bates

Faculty Publications

For the past two years, faculty at San Jose State University (SJSU) have implemented a three- semester minicurriculum in Product Design and Manufacturing. The project follows the Project- Based Learning (PBL) model and is central to the Certificate Program in Product Design in the Mechanical Engineering Department, the Manufacturing Systems concentration in the Department of Aviation and Technology, and the Industrial Design Program in the School of Art and Design. Students in the three courses in the minicurriculum face design challenges while being instructed about the constraints of manufacturability. In each course, students develop three to four products. All products …

Hierarchical Optimal Force-Position-Contour Control Of Machining Processes. Part I. Controller Methodology, Yan Tang, Robert G. Landers, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

There has been a tremendous amount of research in machine tool servomechanism control, contour control, and machining force control; however, to date these technologies have not been tightly integrated. This paper develops a hierarchical optimal control methodology for the simultaneous regulation of servomechanism positions, contour error, and machining forces. The contour error and machining force process reside in the top level of the hierarchy where the goals are to 1) drive the contour error to zero to maximize quality and 2) maintain a constant cutting force to maximize productivity. These goals are systematically propagated to the bottom level, via aggregation …

Special Issue: Engineering Applications Of Representations Of Function, Part 2, Robert B. Stone, Amaresh Chakrabarti

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.

Load Interaction Effects On Fatigue Crack Growth, Stoyan Ivanov Stoychev

Dissertations

Load excursions, in the form of tensile and compressive overloads are known to produce interaction effects during subsequent constant amplitude loading. In this work, the fatigue crack growth and crack closure levels, under both constant amplitude and variable amplitude loading, are investigated in the aluminium-lithium alloy 2090-T84, and the aluminium alloys 2024-T351 and 7150-T651. The crack closure measurements were obtained using both a crack tip opening displacement (CTOD) gauge and a crack mouth opening displacement (CMOD) gauge.

Fatigue crack growth tests were performed on specimens of thickness 1.6mm, 3mm, 6mm and 14mm. Tests were performed at load ratios of 0.1 …

Three-Dimensional Radiative Transfer In An Isotropically Scattering, Plane-Parallel Medium: Generalized X- And Y-Functions, D. W. Mueller, A. L. Crosbie

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The topic of this work is the generalized X- and Y-functions of multidimensional radiative transfer. the physical problem considered is spatially varying, collimated radiation incident on the upper boundary of an isotropically scattering, plane-parallel medium. an integral transform is used to reduce the three-dimensional transport equation to a one-dimensional form, and a modified Ambarzumian's method is used to derive coupled, integro-differential equations for the source functions at the boundaries of the medium. the resulting equations are said to be in double-integral form because the integration is over both angular variables. Numerical results are presented to illustrate the computational characteristics of …

Hierarchical Optimal Force-Position-Contour Control Of Machining Processes. Part Ii. Illustrative Example, Yan Tang, Robert G. Landers, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

There has been a tremendous amount of research in machine tool servomechanism control, contour control, and machining force control; however, to date these technologies have not been tightly integrated. This paper develops a hierarchical optimal control methodology for the simultaneous regulation of servomechanism positions, contour error, and machining forces. The contour error and machining force process reside in the top level of the hierarchy where the goals are to 1) drive the contour error to zero to maximize quality and 2) maintain a constant cutting force to maximize productivity. These goals are systematically propagated to the bottom level, via aggregation …

The Coupling Effect Of Interfacial Adhesion And Tensile Residual Stress On A Thin Membrane Adhered To A Flat Punch, Kai Tak Wan, Lior Kogut

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Adhesion and residual stress play a critical role in the performance and reliability of microdevices, in particular, the cross bridge of RF microswitches. to investigate their combinatorial influences on thin films, an elastic model is constructed for a clamped circular membrane in contact with the planar surface of a rigid cylindrical punch. External force applied to the punch leads to thin film delamination and ultimately 'pull-off' at a critical non-zero contact radius. Characteristic trends of the mechanical responses were obtained for fixed load and fixed grips in terms of pull-off force, punch displacement and contact radius. It is shown that …