Mechanical Engineering Commons^™

Evolution Of Surface Morphology Of Thermo-Mechanically Cycled Nicocraly Bond Coats, J. Shi, Anette M. Karlsson, B. Baufeld, M. Bartsch

Mechanical Engineering Faculty Publications

We investigate morphological surface instabilities on bond coat surfaces of thermal barrier coatings, induced due to thermo-mechanical loading. Experimental results of hollow circular cylindrical specimens, consisting of a directionally solidified superalloy (IN 100 DS) coated with a NiCoCrAlY bond coat, show that the morphological instabilities are strongly dependent on the load conditions. In particular, the morphological instabilities develop during thermal cycling with a thermal gradient over the cylinder wall, whereas the surface remains smooth for thermal cyclic conditions without a gradient. Furthermore, if a cyclic, axial tensile force is applied (synchronized with the thermal cycling), the morphological instabilities become aligned …

Effects Of Middle Plane Curvature On Vibrations Of A Thickness-Shear Mode Crystal Resonator, J. S. Yang, Xiaomeng Yang, Joseph A. Turner, John A. Kosinski, Robert A. Pastore, Weiping Zhang

Department of Engineering Mechanics: Faculty Publications

We study the effects of a small curvature of the middle plane of a thickness-shear mode crystal plate resonator on its vibration frequencies, modes and acceleration sensitivity. Two-dimensional equations for coupled thickness-shear, flexural and extensional vibrations of a shallow shell are used. The equations are simplified to a single equation for thickness-shear, and two equations for coupled thickness-shear and extension. Equations with different levels of coupling are used to study vibrations of rotated Y-cut quartz and langasite resonators. The influence of the middle plane curvature and coupling to extension is examined. The effect of middle plane curvature on normal acceleration …

Task-Driven Multi-Formation Control For Coordinated Uav/Ugv Isr Missions, Herbert G. Tanner

Mechanical Engineering Faculty Publications

The report describes the development of a theoretical framework for coordination and control of combined teams of UAVs and UGVs for coordinated ISR missions. We consider the mission as a composition of an ordered sequence of subtasks, each to be performed by a different team. We design continuous cooperative controllers that enable each team to perform a given subtask and we develop a discrete strategy for interleaving the action of teams on different subtasks. The overall multi-agent coordination architecture is captured by a hybrid automaton, stability is studied using Lyapunov tools, and performance is evaluated through numerical simulations.

Agglomeration Of Bed Particles In Low-Temperature Black Liquor Gasification, Mark A. Woodruff

Theses and Dissertations

The increasing concern for emissions and pollutants from power generation plants has increased the desire for and the study of biomass fuels. Biomass combustion produces less carbon monoxide as well as other greenhouse gases. Black liquor is a byproduct from the Kraft process in making paper. Black liquor can be gasified and used as a fuel in recovery boilers and fluidized bed steam reformers. Recovery boilers have a low efficiency and are used today because of their reliability. Steam reformers have a much higher efficiency but they are a relatively new science and are not as reliable. One of the …

Building America Industrialized Housing Partnership (Baihp), Final Project Report, September 1, 1999 - June 30, 2006, Florida Solar Energy Center, Janet Mcilvaine

FSEC Energy Research Center®

This final report summarizes the work conducted by the Building America Industrialized Housing Partnership (www.baihp.org ) for the period 9/1/99 - 6/30/06. BAIHP is led by the Florida Solar Energy Center of the University of Central Florida and focuses on factory built housing. In partnership with over 50 factory and site builders, work was performed in two main areas - research and technical assistance.

In the research area -- through site visits in over 75 problem homes, we discovered the prime causes of moisture problems in some manufactured homes and our industry partners adopted our solutions to nearly eliminate this …

Torque Ripple Sensor And Mitigation Mechanism, Jason Neely, Steven Pekarek, Jason M. Banaskavich, Daniel S. Stutts

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A torque ripple sensor and method for torque ripple sensing and/or mitigation. A piezoelectric sensor is positioned relative to a motor so that torque fluctuations due to torque ripple of the motor are transmitted to the sensor, resulting in strain of a piezoelectric element. A resulting signal can be amplified and conditioned for determining a magnitude of the torque ripple and/or fed into a feedback loop for applying current control or a counter-torque to the motor for torque ripple mitigation.

Investigation Of The Lead-Free Solder Joint Shear Performance, James Webster, Jianbiao Pan, Brian J. Toleno

Industrial and Manufacturing Engineering

Reflow profile has significant impact on solder joint performance because it influences wetting and microstructure of the solder joint. The purpose of this study is to investigate the effects of reflow profile and thermal shock on the shear performance of eutectic SnPb (SnPb) and Sn3.0Ag0.5Cu (SAC305) solder joints. Test boards were assembled with four different sized surface mount chip resistors (1206, 0805, 0603 and 0402). Nine reflow profiles for SAC 305 and nine reflow profiles for SnPb were developed with three levels of peak temperature (12ºC, 22ºC, and 32ºC above solder liquidus temperature, or 230ºC, 240ºC, and 250ºC for SAC …

Internal Small Volume Storage Water Heater, Kelly Homan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The invention concerns devices for water storage, heating and delivery. A storage water heater of the invention provides an amount of unmixed recently heated water from an internal small volume during a draw along with water from a main volume. When water is drawn from the storage water heater, an amount of recently heated water substantially unmixed with the remaining volume of the tank is drawn along with heated water from the remaining volume. Substantial performance increases in the hot water that may be delivered over a period, such as an hour, may be achieved compared to an otherwise identical …

Ole Miss Engineer 2006

Ole Miss Engineer

No abstract provided.

An Initial Non-Equilibrium Porous-Media Model For Cfd Simulation Of Stirling Regenerators, Roy C. Tew, Terry Simon, David Gedeon, Mounir B. Ibrahim, Wei Rong

Mechanical Engineering Faculty Publications

The objective of this paper is to define empirical parameters for an initial thermal non-equilibrium porous-media model for use in Computational Fluid Dynamics (CFD) codes for simulation of Stirling regenerators. The two codes currently used at Glenn Research Center for Stirling modeling are Fluent and CFD-ACE. The codes’ porous-media models are equilibrium models, which assume solid matrix and fluid are in thermal equilibrium. This is believed to be a poor assumption for Stirling regenerators; Stirling 1–D regenerator models, used in Stirling design, use non-equilibrium regenerator models and suggest regenerator matrix and gas average temperatures can differ by several degrees at …

Transient Response Of Rotor On Rolling-Element Bearings With Clearance, David P. Fleming, Brian T. Murphy, Jerzy T. Sawicki, J. V. Poplawski

Mechanical Engineering Faculty Publications

Internal clearance in rolling element bearings is usually present to allow for radial and axial growth of the rotor-bearing system and to accommodate bearing fit-up. The presence of this clearance also introduces a “dead band” into the load-deflection behavior of the bearing. Previous studies demonstrated that the presence of dead band clearance might have a significant effect on synchronous rotor response. In this work, the authors investigate transient response of a rotor supported on rolling element bearings with internal clearance. In addition, the stiffness of the bearings varies nonlinearly with bearing deflection and with speed. Bearing properties were accurately calculated …

Modeling And Simulation Of The Interaction Between Lubricant Droplets On The Slider Surface And Air Flow Within The Head/Disk Interface Of Disk Drives, Lin Wu

Department of Mechanical and Materials Engineering: Faculty Publications

The dynamic interaction phenomenon between three-dimensional (3-D) lubricant droplets located on the air bearing surface and air flow within the head-disk interface is modeled and numerically simulated. A strong interaction is observed for ultra low flying slider design. The droplet motion and deformation are able to induce non-negligible air bearing force and moment change, which in turn may impose a non-negligible disturbance on the slider’s flying attitude.

Role Of Atomic Scale Interfaces In The Compressive Behavior Of Carbon Nanotubes In Composites, S. Namilae, Namas Chandra

Department of Engineering Mechanics: Faculty Publications

Carbon nanotubes (CNT) are potentially promising fibers for ultra high strength composites. In order to fully har-ness the outstanding mechanical properties of carbon nanotubes as fiber reinforcements, it is essential to understand the nature of load transfer between fiber and matrix under various types of loading conditions that include tension, compression, torsion and a combination thereof. In this paper, we study the compressive behavior (buckling and post-buckling) of carbon nanotubes in the neat form, when they are embedded in polyethylene matrix and with in¬terface chemical modifications using molecular dynamics simulations based on Tersoff–Brenner potential. It is ob¬served that the critical …

The Effect Of Thermal Exposure On The Mechanical Properties Of 2099-T6 Die Forgings, 2099-T83 Extrusions, 7075-T7651 Plate, 7085-T7452 Die Forgings, 7085-T7651 Plate, And 2397-T87 Plate Aluminum Alloys, J. Jabra, M. Romios, J. Lai, E. Lee, M. Setiawan, E. W. Lee, J. Witters, N. Abourialy, J. Ogren, R. Clark, T. Oppenheim, W. E. Frazier, Omar S. Es-Said

Mechanical Engineering Faculty Works

Aluminum alloys 2099-T6 die forgings, 2099-T83 extrusions, 7075-T7651 plate, 7085-T7452 die forgings, 7085-T7651 plate, and 2397-T87 plate were thermally exposed at temperatures of 180 degrees C (350 degrees F), 230 degrees C (450 degrees F), and 290 degrees C (550 degrees F) for 0.1, 0.5, 2, 10, 100, and 1000 h. The purpose of this study was to determine the effect of thermal exposure on the mechanical properties and electrical conductivity of these alloys. The data shows that higher temperatures and longer exposure times generally resulted in decreased strength and hardness and increased percent elongation and electrical conductivity.

Load Characteristics For An Aluminum Alloy Friction Stir Weld, Lewis T. Henderson

Mechanical & Aerospace Engineering Theses & Dissertations

A process was developed to modify a vintage 1960's milling machine to allow axial load measurements to be taken and to allow automated control of the plunging stage during the friction stir welding process. The installation of a load cell in the housing of the mill machine was accomplished by way of modifying internal machine parts and introducing new external hardware. Successful post removal inspections and operational checks show that the conversion of a vintage 1960's milling machine to allow axial load measurements is feasible. The automation of the plunge process during friction stir welding was proven feasible by the …

A Study Correlating Entropy Generation To Parameters Characterizing Thermal Comfort In A Conditioned Room, Sai Shrinivas Sreedharan

Mechanical & Aerospace Engineering Theses & Dissertations

Although significant advances have been made to analyze and study a room as an open thermodynamic system experiencing indoor airflow and heat exchanges with surroundings, studies incorporating entropy generation in the analysis have been sparse. This study focuses on correlating indoor thermal comfort with entropy generation, which hopefully will result in efficient utilization of energy supplied to the system. The problem that this thesis attempts to solve involves calculation of entropy production in conditioned space and its correlation to parameters that characterize thermal comfort. Thermal comfort in a conditioned space is governed by many thermal, mechanical and psychrometric parameters. The …

Performance Of Algebraic Multigrid For Parallelized Finite Element Dns/Les Solvers, Gregory James Larson

Theses and Dissertations

The implementation of a hybrid spectral/finite-element discretization on the unsteady, incompressible, Navier-Stokes equations with a semi-implicit time-stepping method, an explicit treatment of the advective terms, and an implicit treatment of the pressure and viscous terms leads to an algorithm capable of calculating 3D flows over complex 2D geometries. This also results in multiple Fourier mode linear systems which must be solved at every timestep, which naturally leads to two parallelization approaches: Fourier space partitioning, where each processor individually and simultaneously solves a linear system, and physical space partitioning, where all processors collectively solve each linear system, sequentially advancing through Fourier …

Numerical Simulation Of Plasma-Based Actuator Vortex Control Of A Turbulent Cylinder Wake, Nathan Keith Mcmullin

Theses and Dissertations

A numerical study has been performed to investigate the mechanics of the turbulent wake of a circular cylinder that is controlled by a plasma actuator. The numerical investigation implements a straightforward moving wall boundary condition to model the actuator's effects on the flow. Validations of the moving wall for this simulation are set forth with the understanding that the moving wall can model the plasma actuator bulk flow effects at a distance downstream and not in a region near or on the plasma actuator. The moving wall boundary condition is then applied to a circular cylinder at a Reynolds number …

Pneumatic Tire, Alan Neville Gent, Joseph D. Walter

Mechanical Engineering Faculty Research

For many years, tire engineers relied on the monograph, 'Mechanics of Pneumatic Tires', for detailed information about the principles of tire design and use. Published originally by the National Bureau of Standards, U.S. Department of Commerce, in 1971, and a later (1981) edition by the National Highway Traffic Safety Administration (NHTSA), U.S. Department of Transportation, it has long been out of print. No textbook or monograph of comparable range and depth has appeared since. While many chapters of the two editions contain authoritative reviews that are still relevant today, they were prepared in an era when bias ply and belted-bias …

Averaged Inertia Principle For Non-Newtonian Squeeze Films In Wide Parallel Plates: Couple Stress Fluid, Jaw-Ren Lin, Chi-Ren Hung, Rong-Fang Lu

Journal of Marine Science and Technology–Taiwan

On the basis of the Stokes micro-continuum theory, the combined effects of non-Newtonian couple stresses and convective fluid inertia forces upon the squeeze film characteristics of two wide parallel plates are investigated by using the averaged inertia principle. A numerical solution of the film height versus response time is calculated by using the fourth-order Runge-Kutta method. Compared to the Newtonian-lubricant non-inertia case of Hamrock [4], the qualitative effects of couple stresses and convective inertia forces provide an increase in the film pressure, the load capacity and the response time. Moreover, the quantitative effects are more pronounced for wide parallel plates …

Integrating Design Throughout The Mechanical Engineering Curriculum: A Focus On The Engineering Clinics, Krishan Bhatia, Tirupathi R. Chandrupatla, John C. Chen, Eric Constans, Jennifer A. Kadlowec, Anthony J. Marchese, Paris Von Lockette, Hong Zhang

Mechanical Engineering

At Rowan University, we have infused design into the curriculum through an eight-semester course sequence called the Engineering Clinic. Through this experience students learn the art and science of design in a multidisciplinary team environment. While many engineering programs currently include a Capstone Design course taken near the end of the college career to meet the design needs, Engineering Clinic at Rowan allows students to hone their design skills throughout their four-year career. This paper will describe in further detail the objectives and execution of each year in the design sequence, types of projects and how the Clinics complement traditional …

Design And Fabrication Of Rotationally Tristable Compliant Mechanisms, Tyler M. Pendleton

Theses and Dissertations

The purpose of this research is to develop the tools necessary to create tristable compliant mechanisms; the work presents the creation of models and concepts for design and a demonstration of the feasibility of the designs through the fabrication of tristable compliant mechanism prototypes on the macro scale. Prior methods to achieve tristable mechanisms rely on detents, friction, or power input; disadvantages to these methods include a high number of parts, the necessity for lubrication, and wear. A compliant tristable mechanism accomplishes tristability through strain energy storage. These mechanisms would be preferable because of increased performance and cost savings due …

Maximizing Miniature Aerial Vehicles, Stephen Griffiths, Jeffery Brian Saunders, Andrew Curtis, Blake Barber, Timothy W. Mclain, Randal W. Beard

Faculty Publications

Despite the tremendous potential demonstrated by miniature aerial vehicles (MAV) in numerous applications, they are currently limited to operations in open air space, far away from obstacles and terrain. To broaden the range of applications for MAVs, methods to enable operation in environments of increased complexity must be developed. In this article, we presented two strategies for obstacle and terrain avoidance that provide a means for avoiding obstacles in the flight path and for staying centered in a winding corridor.

Obtaining Mode Mixity For A Bimaterial Interface Crack Using The Virtual Crack Closure Technique, A. Agrawal, Anette M. Karlsson

Mechanical Engineering Faculty Publications

We review, unify and extend work pertaining to evaluating mode mixity of interfacial fracture utilizing the virtual crack closure technique (VCCT). From the VCCT, components of the strain energy release rate (SERR) are obtained using the forces and displacements near the crack tip corresponding to the opening and sliding contributions. Unfortunately, these components depend on the crack extension size, Δ, used in the VCCT. It follows that a mode mixity based upon these components also will depend on the crack extension size. However, the components of the strain energy release rate can be used for determining the complex stress intensity …

Design Of Piezoresistive Mems Force And Displacement Sensors, Tyler Lane Waterfall

Theses and Dissertations

MEMS (MicroElectroMechanical Systems) sensors are used in acceleration, flow, pressure and force sensing applications on the micro and macro levels. Much research has focused on improving sensor precision, range, reliability, and ease of manufacture and operation. One exciting possibility for improving the capability of micro sensors lies in exploiting the piezoresistive properties of silicon, the material of choice in many MEMS fabrication processes. Piezoresistivity—the change of electrical resistance due to an applied strain—is a valuable material property of silicon due to its potential for high signal output and on-chip and feedback-control possibilities. However, successful design of piezoresistive micro sensors requires …

Design And Numerical Simulation Of Two Dimensional Ultra Compact Combustor Model Sections For Experimental Observation Of Cavity-Vane Flow Interactions, David S. Moenter

Theses and Dissertations

An improved computational fluid dynamics (CFD) model was developed for numerical simulation of the Ultra Compact Combustor (UCC) concept to enhance turbulent flow characterization of the circumferentially traveling, centrifugal-force enhanced combustion, cavity flow into the engine main flow passage via a radial cavity in the turbine axial guide vanes. The CFD model uses a dense grid on a 60° periodic, axisymmetric combustor section, with the RNG κ-ε turbulence model to resolve turbulent flow details. An overall analysis and performance evaluation of the experimentally tested UCC configuration and an axially shortened cavity baseline configuration was conducted at various experimentally documented operating …

Constitutive Modeling Of The Thermo-Mechanics Associated With Crystallizable Shape Memory Polymers, Gautam Barot

Dissertations

This research addresses issues central to material modeling and process simulations. Here, issues related for developing constitutive model for crystallizable shape memory polymers are addressed in details. Shape memory polymers are novel material that can be easily formed into complex shapes, retaining memory of their original shape even after undergoing large deformations. The temporary shape is stable and return to the original shape is triggered by a suitable mechanism such heating the polymer above a transition temperature. Crystallizable shape memory polymers are called crystallizable because the temporary shape is fixed by a crystalline phase, while return to the original shape …

Field Monitoring And Hourly Simulation Modeling Of The Melink Intellihood Exhaust Control System At Two Supermarkets, One Restaurant, And One Fast Food Restaurant; Final Report, Florida Solar Energy Center, Lixing Gu

FSEC Energy Research Center®

Monitoring of variable speed control of exhaust and make-up air on four Florida buildings is performed. Computer modeling is used to determine energy and demand savings on a yearly basis.

Modeling Dynamics And Exploring Control Of A Single-Wheeled Dynamically Stable Mobile Robot With Arms, Eric M. Schearer

Mechanical Engineering Faculty Publications

This paper focuses on simulations of a dynamically stable mobile robot (Ballbot) with arms. The simulations are of Ballbot lifting its arms in various directions. A PD arm controller works independently of an LQR-designed balancing/station keeping controller. The PD controller drives the arms to follow desired trajectories. When the arms are raised, Ballbot assumes a leaning equilibrium (the physical equilibrium) as opposed to the standing equilibrium (body stands totally upright - a predefined desired equilibrium) that the LQR drives toward. The conflict between these two equilibria causes the robot to lose its balance when lifting heavy (10 kg) loads. A …

Dem Simulated Floor Pressure Induced By A Granular Column, Shawn A. Chester

Theses

At the end of the 19th century, H. A. Janssen discovered that the bottom floor pressure in a cylindrical container of granular material asymptotes exponentially to a value less than the weight of the material i.e., the pressure becomes independent of the fill height of the column. This phenomenon is investigated using discrete element simulations of inelastic, frictional spheres in a cylindrical vessel having a particle-to-cylinder diameter ratio at approximately 13.3 or 26.6, with varying bed heights in both cases. The axial pressure profile and the load experienced by a piston that is supporting the granular column are computed. In …