Mechanical Engineering Commons^™

Computational Analysis And Validation Of The Hans Head And Neck Support, Kapil Tyagi

Mechanical & Aerospace Engineering Theses & Dissertations

One of the major causes of racing fatalities is basilar skull fracture from excessive head motions and neck loading in a frontal impact. There are many head/neck restraints available in the market but HANS head and neck support has proved to be the most efficient one in sled testing. This paper evaluates and compares the performance of the HANS device in MAthematical DYnamic MOdel (MADYMO) software with the sled testing. The tests were conducted for the frontal impact motions, with a crash pulse of 45 G's.

The goal of the tests was to evaluate the performance of HANS without the …

Conjugate Gradient Method For Solving System Of Nonlinear Equations, Abhijit Prakash Honrao

Mechanical & Aerospace Engineering Theses & Dissertations

In this thesis, the conjugate gradient method will be extended to solve symmetric and non-symmetric nonlinear equations. Several variations of the conjugate gradient method are introduced and investigated. To extend the conjugate gradient method for nonlinear problems, there are four methods discussed; the pre-conditioning conjugate gradient method, the pre-conditioning conjugate gradient method for better initial guess, the fixed point conjugate gradient method and the fixed point conjugate gradient method for better initial guess. The four methods are discussed in detail and tested on various numerical examples. The linear numerical examples include a two dimensional structural frame problem, a Hilbert matrix …

An Analysis Of A Finite Element Human Brain In Low Speed Rear Impact Automobile Collision Comparison, Model Development And Study Using Tno Rear Impact Dummy, Mangesh S. Kadam

Mechanical & Aerospace Engineering Theses & Dissertations

According to the National Safety Council, rear-end collisions are the most common types of collisions with approximately two and a half million cases reported every year. Crash tests indicate a change of vehicle velocity of 4km/h (2.5 mph) may produce occupant symptoms. Vehicle damage may not occur until 14-15km/h (8.7 mph) (Davis CG, 1998). Occupants, in rear-end vehicle impacts sustain a motion associated with whiplash, where the head snaps backwards quickly, resulting in linear and/or angular acceleration forces acting on the brain. This angular motion tends to subject the brain to shear deformations from rapid rotation. This study is a …

Complexity Measure Of A Product Or Process By Application Of Fuzzy Multi-Attribute Utility Theory, Shrikant Chandrakant Nagpure

Mechanical & Aerospace Engineering Theses & Dissertations

During the early phases of design, the development cost of complex products or systems is very difficult to obtain because of the uncertainties related to their work breakdown structures and the wide choice of manufacturing technologies with no historical data specific to these products. This thesis presents a method to derive a complexity index to capture the non-additive property and inherent uncertainty, i.e. fuzziness, of the technologies that could be used for complex objects. This complexity index can then be used as a cost index for comparing various candidate manufacturing processes.

Macros are written in Microsoft Excel to establish a …

Design And Fabrication Of A Prototype Fabry-Perot Cavity For The Compton Polarimeter Upgrade At Jefferson Lab, Deepa Deepa

Mechanical & Aerospace Engineering Theses & Dissertations

Upcoming experiments at Hall A at Jefferson lab require 1 % absolute accuracy of the electron beam polarization measurement at 0.85 Ge V energy. The Compton polarimeter at Hall A is capable of measuring beam polarization with 3 - 4 % accuracies at this beam energy. Hence it was proposed to upgrade the present Compton by doubling the laser frequency [2]. The present Compton polarimeter operates with a 1064 nm, continuous wave laser at 200 mW. This power is enhanced to 1.5 kW using a 0.85 m long Fabry-Perot Cavity. Changing to 532 nm laser with the same power would …

Investigation And Applications Of Latin Hypercube Sampling Methods, Prashant K. Patel

Mechanical & Aerospace Engineering Theses & Dissertations

The Latin hypercube sampling method, sometimes called the stratified sampling method, is a commonly used variance reduction method. Recently, the optimal Latin hypercube sampling method (OLH) and the modified optimal Latin hypercube sampling method (MOLH) are introduced in the literature, which use the genetic algorithm to adjust the distance between sampled points.

This paper will compare the basic Latin hypercube, the optimal Latin hypercube and the modified optimal Latin hypercube methods for generating the sample points for statistical application and curve fitting, in te1ms of accuracy and efficiency. Analytical and structural examples are used in this thesis to facilitate the …

Static And Modal Analysis Of The Magnetic Levitation Vehicle, Santosh Kumar Desetty

Mechanical & Aerospace Engineering Theses & Dissertations

The magnetic levitation train project at Old Dominion University has been stalled due to many technical problems. The control system is the main component of the vehicle, which is supposed to maintain an intended gap of 1 cm between the vehicle and the track while traveling, hence providing a smooth ride. The goal of the project is to document the mathematics of the complete system so that the control algorithm can be implemented and modified with the expectation of obtaining an improved levitation and propulsion.

The complete system includes the vehicle, the track, and the concrete guide-way. The focus of …

Modeling Multilevel Supply Chain Systems To Optimize Order Quantities And Order Points Through Mathematical Models, Discrete Event Simulation And Physical Simulations, Alok K. Verma

Mechanical & Aerospace Engineering Theses & Dissertations

Managing supply chains in today's distributed manufacturing environment has become more complex. To remain competitive in today's global marketplace, organizations must streamline their supply chains. The practice of coordinating the design, procurement, flow of goods, services, information and finances, from raw material flows to parts supplier to manufacturer to distributor to retailer and finally to consumer requires synchronized planning and execution. Efficient and effective supply chain management assists an organization in getting the right goods and services to the place needed at the right time, in the proper quantity and at acceptable cost. Managing this process involves developing and overseeing …

Nonlinear Flutter Of Curved Panels Under Yawed Supersonic Flow Using Finite Elements, Mohamed Salim Azzouz

Mechanical & Aerospace Engineering Theses & Dissertations

In the extensive published literature on panel flutter, a large number of papers are dedicated to investigation of flat plates in the supersonic flow regime. Very few authors have extended their work to flutter of curved panels. The curved geometry generates a pre-flutter behavior, triggering a static deflection due to a static aerodynamic load (SAL) over the panel as well as dynamic characteristics unique to this geometry. The purpose of this dissertation is to provide new insights in the subject of flutter of curved panels. Finite element frequency and time domain methods are developed to predict the pre/post flutter responses …

P-Version Time-Discontinuous Galerkin's Method For Nonlinear Transient Heat Transfer Analysis And Sensitivity Analysis, Ta-Cheng Chien

Mechanical & Aerospace Engineering Theses & Dissertations

The finite element method is a powerful tool for approximating the solution of most engineering problems. Traditionally, the finite element method uses linear approximation of field variables over each element, where numerical results converge to the exact solution by increasing the number of elements. A newer finite element method called the p-version finite element method uses higher-order elements which assume a polynomial of order p for the approximation on each element. Here, the approximation will achieve accuracy without increasing the number of elements but by increasing the value of order p.

The focus of this research is on …

Modal Analysis And Validation Of A Gasoline Fuel Injector Using Ansys And Laser Vibrometer, Ravi Kiran Kothamasa

Mechanical & Aerospace Engineering Theses & Dissertations

In the present day market it has been demonstrated that quality and speed make a product successful. An automobile has hundreds of components, which work in synchronization to make the automobile run smoothly. The fuel injector is one of the key components of an automobile. The primary functions of a fuel injector are: to deliver measured quantity of fuel to the engine, to atomize fuel for efficient combustion process, to deliver measured or atomized quantity of fuel to the desired target within manifold/head, and to shut off the fuel supply when no fuel is required. When this fuel injector is …

Effects Of Initial Seated Position On Whiplash In Low Speed Rear-End Impacts Comparison And Study Using The Tno Rear Impact Dummy (Trid) Model, Manjunath P. Venkataramana

Mechanical & Aerospace Engineering Theses & Dissertations

Despite numerous investigations devoted to its scrutiny, injury causing mechanism associated with rear-end impact collision producing injury such as Whiplash Associated Disorder (WAD) has remained a mystery. Several criteria have been proposed to predict the injury causing mechanism, but none have been universally accepted. The challenge lies in determining a set of testing procedures representative of real-world collisions, wherein the results obtained are not only the same as human testing, but remain consistent with various subjects and impact conditions. It is hypothesized that one of the most important considerations is the effect of initial seated position (ISP).

This thesis can …

Effects Of Track Irregularities On Dynamic Responses Of A Moving Maglev Train, Aravind M. Hanasoge

Mechanical & Aerospace Engineering Theses & Dissertations

The Maglev project at Old Dominion University is a collaboration between Old Dominion, American Maglev Technology (AMT), Lockheed Martin, other industry participants and the federal and state governments. This project began at the Norfolk campus in 2002. Under this project, researchers are aiming for a demonstrable engineering prototype that will operate smoothly at speeds of 40 - 45 miles per hour along the 3400 feet long track.

During testing, the vehicle is found to vibrate violently when operated on the ground. Furthermore, the vehicle failed to levitate when operated on the elevated track. As part of the investigation to determine …

Distal Placement Of An End-To-Side Bypass Graft Anastomosis A 3-D Computational Study, John Robert Di Cicco

Mechanical & Aerospace Engineering Theses & Dissertations

A three-dimensional computational fluid dynamics study of blood flow through stenotic arteries has been conducted. Flow phenomena, such as separation regions and turbulence, can be found distal to an arterial stenosis. Frequently, a bypass graft using an end-to-side technique is attached to a stenotic artery to restore adequate blood flow. However, a significant percentage of these grafts fail after thirty postoperative days due to intimal hyperplasia development around the distal anastomosis. Moreover, aberrant wall shear rates have been implicated as a factor in the development of intimal hyperplasia. Thus, the present study examines whether placement of the distal end of …

Field Effect Control Of Electrokinetic Transport Phenomena In Nanofluidics, Song Xue

Mechanical & Aerospace Engineering Theses & Dissertations

Naturally nanofluidics has applications demanding the samples to be handled in exceedingly small quantities due to the small size of the fluidic channels in nanofluidic devices, such as characterization of single biomolecules. Fluids confined in channels of nanometer characteristic dimensions exhibit physical behaviors not observed in large conduits. Charge properties of the nanochannel wall in contact with an aqueous solution play essential roles in the involved electrokinetic transport phenomena occurring in nanofluidic devices. In addition to tuning the charge properties of the nanofluidic channel wall by adjusting the solution properties such as pH and background salt concentration, field effect transistor …

Uncertainty Propagation And Robust Design In Cfd Using Sensitivity Derivatives, Michele M. Putko

Mechanical & Aerospace Engineering Theses & Dissertations

This study investigates and demonstrates a methodology for uncertainty propagation and robust design in Computational Fluid Dynamics (CFD). Efficient calculation of both first- and second-order sensitivity derivatives is requisite in the proposed methodology. In this study, first- and second-order sensitivity derivatives of code output with respect to code input are obtained through an efficient incremental iterative approach.

An approximate statistical moment method for uncertainty propagation is first demonstrated on a quasi one-dimensional (1-D) Euler CFD code. This method is then extended to a two-dimensional (2-D) subsonic inviscid model airfoil problem. In each application, given statistically independent, random, normally distributed input …

Numerical Study Of Combustion Of Hydrogen And Ethylene In A Two-Dimensional Dual-Mode Scramjet Combustor, Robert A. Carson

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis presents computational fluid dynamics results for two-dimensional flow geometries utilizing two fuels, hydrogen (H2) and ethylene (C2H4). Upstream interaction was evident with the use of both fuels due in part to recirculation in the combustor, the inlet pressures and the combustion process. Results were obtained for hydrogen using a reduced chemical kinetic model while results obtained for ethylene employed a reduced chemical kinetic model as well as an expanded chemical kinetic model.

Initially, an examination of grid composition was conducted in order to select the most numerically efficient and accurate grid for reacting flow in the current combustor …

Analysis Of Human Thermal Comfort Using A Coupled Model For Predicting Human Body-Environment Heat And Mass Exchange, Ahmed M. Al-Mogbel

Mechanical & Aerospace Engineering Theses & Dissertations

Recent advances in computational fluid dynamics (CFD) make it possible to accurately predict many features of airflow within ventilated spaces. The present study investigates thermal comfort aspects of an occupant in a conditioned space, using a CFD code.

The heat and mass transfer between the human body and the surrounding environment is analyzed by a coupled model that accounts for dispersal of metabolically generated heat in the body to the surroundings by the combined mechanisms of radiation, convection, respiration and evaporation. A two-node model in which two coupled non-linear algebraic equations govern the skin temperature and the body core temperature …

Computation Of Shock Induced Noise In Imperfectly Expanded Supersonic Jets, Bulent Imamoglu

Mechanical & Aerospace Engineering Theses & Dissertations

Screech noise exists only in imperfectly expanded jets. The exit pressure of imperfectly expanded jets does not match ambient pressure, so expansion or compression waves appear out of the nozzle and generate shock cell patterns. Screech is generated by the interaction of shock cells and instability waves. Many experiments and computations have been done to model screech noise, but it is not yet a very well known subject.

A numerical study is performed to understand screech generation mechanisms and to compare with latest experiments. A supersonic underexpanded jet of 25.4 mm diameter is modeled for cases of Mach numbers of …

Analytical Model Of A Thermomechanical Hot Channel Coupled To A Friction Stir Welding Process, Saptarshi Mandal

Mechanical & Aerospace Engineering Theses & Dissertations

Although fusion welding techniques are well established, recent developments in solid state joining techniques have produced high quality welds in materials that are difficult to fusion weld. Friction Stir Welding (FSW) was developed in 1991 as a robust solid-state joining technique that uses a specially shaped rotating tool to generate heat and plasticize material around the tool. The tool then mixes plasticized material along the joint line to produce the weld. Over the last decade, FSW has become increasingly popular for welding aluminum. The combination of attractive properties of the weld and cost-efficiency has led researchers to investigate the feasibility …

Nonlinear Response And Fatigue Estimation Of Aerospace Curved Surface Panels To Acoustic And Thermal Loads, Adam Przekop

Mechanical & Aerospace Engineering Theses & Dissertations

This work presents a finite element modal formulation for large amplitude free vibration of arbitrary laminated composite shallow shells. The system equations of motion are formulated first in the physical structural-node degrees of freedom (DOF). Then, the system is transformed into general Duffing-type modal equations with modal amplitudes of coupled linear bending-inplane modes. The linear bending-inplane coupling is due to the shell curvature as well as unsymmetric lamination stacking. Multiple modes, inplane inertia, and the first-order transverse shear deformation for composites are considered in the formulation. A triangular shallow shell finite element is developed from an extension of the triangular …

Optimization-Based Architecture For Managing Complex Integrated Product Development Projects, Hisham Mohamed El-Sayed Abdelsalam

Mechanical & Aerospace Engineering Theses & Dissertations

By the mid-1990's, the importance of early introduction of new products to both market share and profitability became fully understood. Thus, reducing product time-to-market became an essential requirement for continuous competition. Integrated Product Development (IPD) is a holistic approach that helps to overcome problems that arise in a complex product development project. IPD emphasis is to provide a framework for an effective planning and managing of engineering projects. Coupled with the fact that about 70% of the life cycle cost of a product is committed at early design phases, the motivation for developing and implementing more effective methodologies for managing …

Diode Laser Crystallization Of Hydrogenated Amorphous Silicon Thin Films For Solar Cell Applications, Brian A. Eaton

Mechanical & Aerospace Engineering Theses & Dissertations

The research objectives were to prove the crystallization of hydrogenated amorphous silicon (a-Si:H) thin films using a diode laser operating at an 805 nm wavelength and to provide morphology trends in laser crystallized samples. This work was primarily intended for solar cell applications.

One industry goal was to produce a high-efficiency and low-cost solar cell capable of competing economically with other energy sources at large scale in the world market. Excimer laser crystallization was one very promising technique. However, two important problems still hindered economic competition. This research addressed the problems associated with excimer laser crystallization by utilizing a diode …

Piezoelectric Sensor In The Application Of Rolling Bearing Health Monitoring, Yinyin Liu

Mechanical & Aerospace Engineering Theses & Dissertations

A condition-based monitoring concept for rolling element bearings in machinery utilizing a piezoelectric load sensor is investigated in this thesis. The radially polarized cylindrical piezoelectric sensor is modeled in its specific coordinates. The sensor registers the stress occurring in all directions around it. The sensor's behavior due to several typical loads is analyzed. Based on the induced stresses in the sensor, the sensor's output as an electric charge can be obtained using the method of integration.

Considering both the normal and tangential loads distributed on the rolling beating's roller-raceway contact surface, the dynamic stress distribution in the outer raceway was …

Two Dimensional Numerical Simulation Of Highly-Strained Hydrogen-Air Opposed Jet Laminar Diffusion Flames, Kyu C. Hwang

Mechanical & Aerospace Engineering Theses & Dissertations

In this study, a detailed 2-D numerical technique is utilized to investigate the structure, and flame extinction and restoration characteristics of laminar hydrogen-air opposed jet diffusion flames, using both plug (uniform) and parabolic inflow boundary conditions for 3 millimeter jet tubes, spaced 6 millimeters apart and imbedded in low velocity coflows.

First, by using the most recent of two chemical kinetic models, excellent agreement was obtained between calculated distributions of temperature and major species, and published UV laser Raman scattering measurements, for 50% and 100% hydrogen-air flames over a range of input strain rates. Agreement with measured OH profiles was …

Numerical Studies On Supersonic Mixing And Combustion Phenomena, Tarek M. Abdel-Salam

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical study is conducted to investigate the mixing, combustion, and flow characteristics of different scramjet-combustor configurations. Three-dimensional models for the combustors have been used. Numerical results are obtained using a finite volume computational fluid dynamics (CFD) code with unstructured grids with sizes between 200,000 and 400,000 cells.

In the first part of the current study, the effects of the side angle of the fuel injectors in both mixing and combustion processes are investigated. Raised (compression) and relieved (expansion) wall-mounted ramps are used with side angles of 0 (unswept), 5, and 10 degrees. Results are obtained for nonreacting flows as …

Numerical Study Of Two-Dimensional Secondary Injection Into A Mach 3.5 Freestream, Stephen C. Coghill

Mechanical & Aerospace Engineering Theses & Dissertations

Upstream interaction within a dual-mode scramjet engine is investigated numerically. The upstream interaction is investigated by increasing the freestream-to-injector pressure ratio. The constant area duct and sudden expansion geometries are used to achieve these results. Analysis using the symmetry boundary condition is compared to the full boundary condition for the constant area duct. Numerical analysis of the Mach 3.5 freestream is conducted using normal sonic injection of nitrogen gas to create the upstream interaction. Comparisons, where applicable, are made to experimental results. Due to the high speed of the flowfield, oblique shockwaves are present causing numerical convergence difficult to achieve. …

Optimal Feedback Control For Ship Roll Motion Under Sea States, Anusit Anmanatarkul

Mechanical & Aerospace Engineering Theses & Dissertations

The primary influences of ship motion are roll motion. The purpose of this dissertation is to discuss a means to reduce the roll amplitude of ship motion in the case of zero forward speed using the roll mitigation device known as the flume tank, or U-tube, tank. Passive control and active control are studied. Optimal feedback control is the designated algorithm for activated roll mitigation device. The assumed model in this study is a submarine chaser. The linear coupled equation of swaying, rolling, and yawing motion of this assumed model is studied. The roll motion of this vessel is investigated …

New Approaches To Gortler And Tollmien-Schlichting Boundary-Layer Instabilities, Vijay Kalburgi

Mechanical & Aerospace Engineering Theses & Dissertations

A detailed understanding of the physical processes that lead to instability and transition in the external viscous boundary layers of airfoils has been the goal of researchers for decades. This study seeks to enhance our understanding of Gortler and Tollmien-Schlichting instabilities through a critical review of prior theoretical methodology and fundamental experiments, the development of dimensionally consistent disturbance equations, and novel interpretation of the resulting flow physics revealed by their solutions to explain the process of transition.

Gortler vortices arise in boundary layers along concave surfaces due to centrifugal effects and these vortices in combination with other instabilities play an …

Generalized Predictive Control Of Ship Coupling Motions Using Active Flume Tanks, Abdulkarim Mohammed Alotaiwi

Mechanical & Aerospace Engineering Theses & Dissertations

This dissertation uses the Generalized Predictive Control (GPC) approach to design a control system for a ship rolling motion coupled with the sway and yaw using an activated flume tank. GPC is a strategy based on system output prediction over finite horizon known as the prediction horizon. GPC controller is designed from the coefficients of the Autoregressive model with exogenous input (ARX) that are computed directly from input and output data. It computes the future control input based on the cost function with weighted input and output. System identification approach is implemented on the system to find the ARX coefficients …