Mechanical Engineering Commons^™

Synthesis Of Multi-Wall Carbon Nanotubes Using Unseeded Hydrocarbon Diffusion Flames, Kozo Saito, Forman A. Williams, Alvin S. Gordon, Liming Yuang

Mechanical Engineering Faculty Patents

A method is provided for synthesizing carbon nanotubes from unseeded methane-air diffusion flames. A novel stainless steel and Ni—Cr wire probe is also provided for collecting carbon nanotubes from those diffusion flames.

Laminar Film Condensation On A Horizontal Plate In A Porous Medium With Surface Tension Effects, Tong-Bou Chang

Journal of Marine Science and Technology–Taiwan

The problem of steady filmwise condensation on a finite-size horizontal plate embedded in a porous medium is studied for the case in which a cold plate faces upwards with a dry saturation vapor. Due to the effects of surface tension forces, there is a two-phase zone lying between the liquid film and the vapor zone. As in classical filmwise condensation problems, it is assumed that; (a) the inertia within the liquid film is negligible, and (b) the properties of porous medium, dry vapor, and condensate are constant. A dimensionless parameter Boc is introduced to characterize liquid flow due to surface …

A Note On Grashof’S Theorem, Wen-Tung Chang, Chen-Chou Lin, Long-Iong Wu

Journal of Marine Science and Technology–Taiwan

In this paper, Grashof’s theorem is justified from the perspective of the occurrence of stationary configurations and uncertainty configurations of four-link chains. The link length relations at stationary configurations and uncertainty configurations are examined in detail based on the triangle inequality, and then the conditions for the existence of a crank and a change point are deduced.

Analysis Of Indentation Loading Of Cortical Bone Using Acoustic Emission Techniques, Ashkan Safari, Ger Reilly, Brendan Mccormack

Conference Papers

In this study, we recorded the number of Acoustic emission (AE) hits and related AE energy during indentation fracture of cortical bone using a PAC PCI-2 card and pico sensor. A threshold value of 43dB was used to filter premature trigger due to background noise. Registered AE hits had more than one count (threshold crossing). Amplifier gain was set at 40dB with a (0.1-1) MHz band pass filter. 8mm cubes of cortical bones were indented in the longitudinal direction at constant crosshead speed of 1 mm min-1 using a large 2D, 50˚ wedge indenter. We hypothesised that signals occurring as …

College Of Engineering Senior Design Competition Fall 2005, University Of Nevada, Las Vegas

Fred and Harriet Cox Senior Design Competition Projects

Part of every UNLV engineering student’s academic experience, the senior design project stimulates engineering innovation and entrepreneurship. Each student in their senior year chooses, plans, designs and prototypes a product in this required element of the curriculum. A capstone to the student’s educational career, the senior design project encourages the student to use everything learned in the engineering program to create a practical, real world solution to an engineering challenge.

The senior design competition helps to focus the senior students in increasing the quality and potential for commercial application for their design projects. Judges from local industry evaluate the projects …

Top-Down Structure And Device Fabrication Using In Situ Nanomachining, Xiaodong Li, Xinnan Wang, Qihua Xiong, Peter C. Eklund

Faculty Publications

We demonstrate the potential of an alternative tool for the fabrication of nanoscale structures and devices. A nanoindenter integrated with an atomic force microscope is shown to be a powerful machine tool for cutting precise length nanowires or nanobelts and for manipulating the shortened wires. We also demonstrate its utility in cutting grooves and fabricating dents (or periodic arrays of dents) in ZnSnanobelts. This approach permits the direct mechanical machining of nanodevices that are supported on a substrate without the inherent complications of e beam or photolithography.

Fully Compliant Tensural Bistable Micro-Mechanisms (Ftbm), D. L. Wilcox, Larry L. Howell

Faculty Publications

A new class of bistable mechanisms, the fully compliant tensural bistable micromechanism (FTBM) class, is introduced. The class consists of linear bistable micromechanisms that undergo tension loads, in addition to the bending loads present, through their range of motion. Proof-of-concept designs fabricated in two different microelectromechanical systems (MEMS) surface micromachining processes were demonstrated. Three sets of refined designs within the FTBM class were designed using optimization methods linked with nonlinear finite element analysis (FEA), then fabricated and tested. Measured force and displacement performance are compared to values obtained by FEA. On-chip actuation of the bistable mechanisms was achieved using thermomechanical …

A Detailed Approach For Concept Generation And Evaluation In A Technology Push Product Development Environment, Andrew Nelson

Theses and Dissertations

Many companies rely on successful product development as a means to increase their revenues and expand their operations. Market pull, the most common form of product development, begins with a specific customer, and focuses on how to satisfy that customer's needs. Technology push is a product development process where a technology is first discovered, then embodied in products that may be marketed to specific customers. Technology push presents several obstacles not encountered in market pull processes, such as a lack of a defined market, lack of established processes and difficulty in execution. These complications keep technology push from being more …

Ole Miss Engineer 2005

Ole Miss Engineer

No abstract provided.

Numerical Study Of Chemically Reacting Viscous Flow Relevant To Pulsed Detonation Engines, Tae-Hyeong Yi

Mechanical and Aerospace Engineering Dissertations - Archive

A computational fluid dynamics code for two-dimensional, multi-species, laminar Navier-Stokes equations is developed to simulate a recently proposed engine concept for a pulsed detonation based propulsion system and to investigate the feasibility of the engine of the concept.The governing equations that include transport phenomena such as viscosity, thermal conduction and diffusion are coupled with chemical reactions. The gas is assumed to be thermally perfect and in chemically non-equilibrium. The stiffness due to coupling the fluid dynamics and the chemical kinetics is properly taken care of by using a time-operator splitting method and a variable coefficient ordinary differential equation solver. A …

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

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 …

Effect Of Gender On Lower Extremity Kinematics During Rapid Direction Changes: An Integrated Analysis Of Three Sports Movements, S. G. Mclean, K. B. Walker, Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

Anterior cruciate ligament (ACL) injury is a common sports injury, particularly in females. Gender differences in knee kinematics have been observed for specific movements, but there is limited information on how these findings relate to other joints and other movements. Here we present an integrated analysis of hip, knee and ankle kinematics across three movements linked to non-contact ACL injury. It was hypothesised that there are gender differences in lower extremity kinematics, which are consistent across sports movements. Ten female and ten male NCAA basketball players had three-dimensional hip, knee and ankle kinematics quantified during the stance phase of sidestep, …

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 …

Determination Of Stiffness Matrix Of Tapered Roller Bearings For Vibration Models, Jeeva Kumar

Masters Theses

The stiffness matrix of tapered roller bearings under radial and axial load conditions was evaluated using an analytical model and an experimental approach. An experimental test system was designed and manufactured to determine the radial stiffness of the bearing under combined axial and radial load conditions. A second fixture was designed to measure the stiffness of the bearing under pure axial load conditions. The stiffness coefficients determined have been compared with those obtained from the analytical model, OEM (Original Equipment Manufacturer) data and ABAQUS model (finite element analysis software).

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 …

A K-Epsilon Extension For Wall-Bounded Flows On The Broadband Aeroacoustic System Simulator, David González

Masters Theses

The turbulence modeling capabilities of the Broadband Aeroacoustic System Simulator (BASS), an experimental code developed at NASA Glenn Research Center, have been extended to include wall-bounded flow capabilities. This was done by first validating the code's viscous solving routines by comparing numerical solutions to known, simple analytic solutions. Finally, the dynamics of the wall shear flows were accounted for with the use of wall-damping functions incorporated into the turbulence model. The results for both viscous and turbulence routines agree well with published data.

Mixing Flow Structures Of Scalloped, Forced Lobed Mixers Using Piv And Plif Measuring Techniques, Nathan J. Cooper

Masters Theses

An Experimental study of internal forced lobed mixers similar to those used in jet aircraft engines is performed using whole field species concentration and velocity measuring techniques. Planar temperature and velocity measurements using Planar Laser Induced Fluorescence (PLIF) and 2D Particle Image Velocimetry (PIV) are performed for lobed, lobed scalloped and splitter mixers in aqueous solution. Specific emphasis is given to study scallops or notches cut into the mixer trailing edge and their role in mixing enhancement. Mixing is compared through velocity and species concentration measurements on axial and streamwise planes for the three dimensional, forced mixers in a confined …

Ductile Regime Nano-Machining Of Silicon Carbide, Biswarup Bhattacharya

Masters Theses

This thesis describes experimental work carried out to study the ability to ductile . single point diamond turn both polycrystal Silicon Carbide (SiC) and chemically vapor deposited (CVD) SiC. A Precitech diamond turning machine was used for ductile regime machining of polycrystal SiC at depths of 10 and 25 nm. The possibility of machining SiC in the ductile mode was substantiated by post process analysis of the chips collected during machining and the surface profiles. The force data obtained during machining was recorded and compared later with the different depth of cuts. An investigation into the ability to single point …

Composite Mechanical Property Enhancement Through The Use Of Y-End Shaped Short Fibers, Jin Tan

Theses and Dissertations - UTB/UTPA

This study uses Finite Element Analysis (FEA) to predict the mechanical property enhancement of the composites reinforced by end-shaped short fibers with different aspect ratios and volume fractions at microscale. Fibers used include conventional straight short fibers (CSSF), dumbbell-end shaped short fibers (DSSF), bone-end shaped short fibers (BSSF) and Y-end shaped short fibers (YSSF) with various lengths and angles. The critical distances between neighboring fiber ends for FEA modeling were theoretically deduced and numerically verified. This study has never been done before and the results fill a gap to this field.

In conclusion, planar-end Y-shaped short fiber reinforced composites showed …

Preliminary Design Approach For Prosthetic Ankle Joints Using Compliant Mechanisms, Jason Matthew Wiersdorf

Theses and Dissertations

The objective of this thesis is to develop design approaches and models for prosthetic ankle joints using kinematic models of the human ankle and compliant mechanisms technology. Compliant mechanisms offer several potential design advantages over traditional rigid-body designs including high reliability and low cost. These design advantages are ideal for use in prosthetics. Some prosthetic ankle/foot systems currently on the market have multiple degrees of freedom yet are expensive. Additionally, even though these systems have multiple degrees of freedom, none of them are designed after the actual movements of the biological ankle. In this thesis a two, single degree-of-freedom hinge …

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 …

A Gasless Method Of Spraying Thermoplastic Resin, Dan T. Rogers

Theses and Dissertations

This spraying method for thermoplastic resins is a new manufacturing process for applying thermoplastics to a mold or surface in an efficient way that has the potential of reducing cycle time. Spraying thermoplastic resins is similar to spraying other polymers, such as paint, with the differences being higher pressure and temperature. This method uses an injection molding machine with a modified nozzle to spray the plastic material. In this study, temperature, pressure, and nozzle size were factors that influenced the success of this spraying method. The method of spraying in this study proved spraying without a gas is possible, a …

Object Oriented Cae Software For The Exploration And Design Of Microstructures, Stephen D. Sintay

Theses and Dissertations

Through the use of generalized spherical harmonic basis functions a spectral representation is used to model the microstructure of cubic materials. This model is then used to predict the macroscopic elastic and plastic properties of materials with cubic crystal symmetry and various sample symmetry including triclinic and axial—symmetric. Building on the work of citeN{Barnett-FractureMechanics} the influence that anisotropy has on the fatigue response of the material is also modeled. This is accomplished through using the effective elastic stiffness tensor in the computation of crack extension force G. The resulting material model and macroscopic property calculations are the foundation for …