Mechanical Engineering Commons^™

Optimum Preventive Maintenance By Markov Processes, Wen-Chun Chung

Mechanical & Aerospace Engineering Theses & Dissertations

The objective of this thesis is to carry out a maintenance cost analysis for a part that is subject to both random failure and deterioration failure. The analysis follows the guidelines of preventive maintenance and leads to a means of finding out the total cost of the maintenance procedure based on different maintenance cost data. The maintenance model developed in this thesis is based on a Markov Process, and its optimization is derived from a maximization of the availability of the part.

A case study was used to demonstrate the method for obtaining the optimal minimal preventive maintenance rate, steady …

Development And Validation Of Hardware To Measure The Load-Deflection Characteristics Of Any Material, Manish Govardhanrao Kalmegh

Mechanical & Aerospace Engineering Theses & Dissertations

A portable device to measure load-displacement will have applications in biomechanics and reverse engineering in the automotive and aerospace industries. Hardware was developed by attaching a load cell (LC 201, Omegadyne, Inc., Sunbury, Ohio) to a Faro Arm (Faro Technologies, Lake Mary, Florida), a portable coordinate measuring machine that accommodates standard and custom end effectors. A LabVIEW (National Instrument, Austin, Texas) program was developed to process the load cell and deflection data obtained from the Faro Arm. To validate this system, a four-inch square block, chair cushion, and head restraint of a car were tested using a material testing machine …

Caffeine Model Identification For Vigilance Performance Prediction, Chun-Hui Huang

Mechanical & Aerospace Engineering Theses & Dissertations

The pharmacodynamics and pharmacokinetics of caffeine have been well characterized. In this study, a caffeine dynamic model is developed to describe its pharmacodynamic effects on vigilance performance. Validated biomathematical models developed to address both individual and group fatigue and alertness in a non-laboratory setting represent a tremendous commercial opportunity. First, a test data set with caffeine effects isolated from circadian and homeostatic effects is created. Then a modeling approach for input and output effects is developed and different model structures for the caffeine effects are considered. Observer/Kalman filter Identification (OKID) algorithm is proposed and developed to identify the caffeine model …

Development And Validation Of A Dynamic Model Of The Maglev Transportation System At Old Dominion University, Ajinkya V. Deodhar

Mechanical & Aerospace Engineering Theses & Dissertations

A dynamic model for the vehicle-guideway coupled with a controller is developed using dynamic modelling software, MADYMO. The fundamental characteristics of the vehicle are obtained from detailed FE analysis in NASTRAN. The vehicle is then converted into a 21-degree-of-freedom rigid body system with 12 FE magnets. A two span concrete guideway of 54 meters in length is modelled using 3D solid Hex8 elements. The air gap is modelled as a penetration of the magnets in the guideway. The PD controller aims at achieving constant penetration (i.e. the air gap) of all magnets in the guideway, throughout the simulation. This PD …

The Effect Of Hans Device On Brain Pressure Values In Finite Element Brain Models, Mihir M. Jawale

Mechanical & Aerospace Engineering Theses & Dissertations

A parametric study of behavior of different brain material properties when exposed to a mid-high severity pulse is presented. Few studies have considered brain pressure as a parameter to study the effect of change of brain material properties. Specifically pressure and strain values in the frontal and posterior fossa and occipital region of the brain are investigated for mid-high severity pulse.

The brain model is composed of several parts modeled as hexahedral elements and with different material properties. A parametric study of several material types of brain is conducted using MAthematical DYnamic MOdel (MADYMO). Initially only the finite element (FE) …

Study Of Multibody Dynamics Using Matlab, Kalyani Soman

Mechanical & Aerospace Engineering Theses & Dissertations

Research in computational dynamics has gained importance in the past few years because of the demand for analysis and simulation of various multi-body systems in the growing mechanical and aerospace industry. These multi-body systems are made of individual bodies that are interconnected via mechanical joints. Mathematically, these joints that connect the bodies can be described as constraint equations imposed upon the motions of the involved free bodies. This process will result in an equation of motion expressed in the form of a differential-algebraic equation. It is the main objective of this thesis to develop a solution algorithm that can take …

Experimental Investigation Of Active Control Of Bluff Body Vortex Shedding, Ilteris Koc

Mechanical & Aerospace Engineering Theses & Dissertations

Mean and fluctuating forces acting on a body are strongly related to vortex shedding generated behind it. Therefore, it is possible to obtain substantial reductions of at least the unsteady forces if vortex shedding is controlled or its regularity is reduced. While conventional active flow control methods are mainly concerned with direct interaction with, and alteration of, the mean flow about a body, modern techniques involve altering existing flow instabilities using relatively small inputs to obtain large-scale changes of mean flows. Aerodynamic flow control may be intended to delay or suppress boundary layer separation through creation of a boundary layer …

Simulation And Thermo-Economic Analysis Of A Solar-Assisted Heat Pump System For Domestic Water Heating Application, Vaibhav D. Gagrani

Mechanical & Aerospace Engineering Theses & Dissertations

The present study examines the potential of solar-assisted heat pump (SAHP) system for domestic water heating application over conventional electrical water heating system. The focus of study is on developing a user-friendly and interactive software using Java platform with Microsoft Access being used for maintaining the database. The software developed is capable of predicting the thermal and economic performance of a SAHP system under varying conditions. The software allows the user to select the geographic location, specify condensing temperature, collector, and compressor parameters, and thermal load requirement. Location specific meteorological data, such as latitude, solar radiation, and ambient temperature, are …

Stochastic Optimization Formulations For Structure Design, Shivanandini Tanuku

Mechanical & Aerospace Engineering Theses & Dissertations

The production process and the operational environment of a product usually involve many unpredictable elements, such as the manufacturing tolerance, the service loads, the maintenance schedule, etc. Furthermore, the targeted functionality of a product can also be alternated or enhanced in its service life due to the technology advancement, new demands, or new regulation. It is thus a challenge to a designer to include these uncertainties in the early design stage of a product.

This thesis uses a simple three-bar truss problem as a vehicle to investigate the qualities of the optimal solutions resulted from various stochastic programming formulations. The …

Shaken Baby Syndrome: Retinal Hemorrhaging. A Biomechanical Approach To Understanding The Mechanism Of Causation, Steven Alex Hans

Mechanical & Aerospace Engineering Theses & Dissertations

Shaken Baby Syndrome (SBS) is a form of abuse where typically an infant, age six months or less, is held and shaken. There may or may not be direct impact associated with this action. Further, there is very little agreement on the actual mechanism of SBS. Clinical studies are limited in showing the exact mechanism of injury and only offer postulations and qualitative descriptions. SBS has received much attention in the media, has resulted in a great deal of litigation and can be the source of unfounded accusations. Therefore, it is necessary to try to quantify the forces that may …

Micro Synthetic Jets As Effective Actuator, Mehti Koklu

Mechanical & Aerospace Engineering Theses & Dissertations

Synthetic jets have previously been studied as actuators for external macroflow control and recently been proposed for internal microflow applications. Despite the wide variety of the potential applications of synthetic jet actuators, the majority of the studies have been done at macro scales. Furthermore, there has not been any design methodology that addresses the effectiveness of the micro synthetic jet actuators. Bearing these needs in mind, a micro synthetic jet configuration is considered in a microscale environment where Kn number is less than 0.1 and more than 0.001. Flowfields are simulated by solving the compressible Navier-Stokes equations. The wall boundary …

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 …

Most Probable Point-Based Design Optimization, Akhil R. Tipnis

Mechanical & Aerospace Engineering Theses & Dissertations

Modem products ranging from simple components to complex systems should be designed to be optimal and reliable. The challenge of modem engineering is to ensure that manufacturing costs are reduced and design cycle times are minimized while achieving requirements for performance and reliability. If the market for the product is competitive, improved quality and reliability can generate very strong competitive advantages. Reliability based design optimization plays a very important role in designing almost any kind of product. This investigation focuses on the development of the hybrid PMNRIA approach which uses the active-in-reliability concept for reliability based design optimization. The efficiency …

Micron-Level Actuator For Thermal-Fluid Control In Microchannels, Nurhak Erbas

Mechanical & Aerospace Engineering Theses & Dissertations

Effectiveness of an actuator is investigated for thermal-flow control in microchannels. First, simulations of a single actuator in a quiescent external medium are performed in order to study the parameters characterizing the synthetic jet flow from the actuator. For this purpose, a simplified, two-dimensional configuration is considered. The membrane motion is modeled in a realistic manner as a moving boundary in order to accurately compute the flow inside the actuator cavity. The geometric and actuation parameters of the actuator are investigated to define the effectiveness of the jet flow. The study is done initially at macro scales. Then, the flow …

Unsteady Numerical Analysis Of A 2-Dimensional, Hydrogen Fueled, Air-Breathing Dual Mode Scramjet Engine, Nathan John Luetke

Mechanical & Aerospace Engineering Theses & Dissertations

Upstream interaction in a transient two-dimensional dual-mode scramjet engine is examined. This research is performed to compare completed and verified steady results with unsteady results in order to have a better understanding of the flow field. The flow is solved numerically with a Mach 2.5 free stream and sonic normal injection of hydrogen fuel emanating from facing walls while no symmetry assumptions were made. The free stream is modeled as vitiated air in order to produce comparable flight enthalpies and stagnation properties at the combustor inlet during flight conditions of approximately Mach 7. The vitiated stream consists of water vapor …

Life Cycle Impact Assessment Method For Early Design Phase Of Industrial Products, Harpreet Singh Multani

Mechanical & Aerospace Engineering Theses & Dissertations

The objective of this thesis is to develop a simplified life cycle impact assessment method that can reliably and quickly provide the values of Eco-indicator 99 single score, the Eco-indicator damage categories score (human health, ecosystem quality, resource depletion), environmental impacts like global warming, ozone depletion, acidification, eutrophication, photochemical oxidants potential of the product/process, which could be used in the initial design stages for alternative design comparisons and product improvements, thus leading towards green manufacturing.

To achieve this, a variety of products have been chosen and the life cycle inventory data is gathered from the environmental product declarations that are …

Statistical Interpretation Of Mohr-Coulomb Theory As Applied To Fracture In Brittle Materials Containing Cracks, Mudit J. Monsi

Mechanical & Aerospace Engineering Theses & Dissertations

Fracture in brittle materials containing pre-existing cracks was studied. The probability of of crack growth under both shear and tensile stresses was determined for an arbitrary distribution of crack sizes. Two different crack orientation distributions, random and uniform, as well as friction were also taken into account. The material's reliability was assumed to depend on the number of active cracks at a particular stress level, and this was expressed as an arbitrary 2-parameter Weibull distribution. Two new and efficient methods for calculating crack growth probabilities based on spherical triangles and spherical caps were developed. They utilized normalized stress coordinates and …

Boundary Interference Assessment And Correction For Open Jet Wind Tunnels Using Panel Methods, Wael Ahmed Mokhtar

Mechanical & Aerospace Engineering Theses & Dissertations

The presence of nearby boundaries in a wind tunnel can lead to aerodynamic measurements on a model in the wind tunnel that differ from those that would be made when the boundaries of the moving fluid were infinitely far away. The differences, referred to as boundary interference or wall interference, can be quite large, such as when testing aircraft models developing high lift forces, or whose wingspan is a large fraction of the wind tunnel width, or high drag models whose frontal area is a large fraction of the tunnel cross section. Correction techniques for closed test section (solid walled) …

Mechanical Properties And Durability Of A Composite Material At Cryogenic Temperatures, Ray Walton Grenoble

Mechanical & Aerospace Engineering Theses & Dissertations

Several issues relevant to the use of a high-performance graphite-epoxy material in hydrogen storage tank applications have been examined. The tensile properties of IM7/977-2 were evaluated as a function of test temperature and thermal-mechanical load history. The temperature dependent coefficient of thermal expansion (CTE) of unidirectional specimens of the same material was measured between -200°C and 0°C. The effects of test temperature, mechanical loading, and damage state on the leak rate of hydrogen gas through IM7/977-2 laminates were evaluated using a novel test system. Finally, the mechanical properties of several commercially available polymer films, which might prove useful as leak-resistant …

Process And Product Optimization Techniques - A Comparative Analysis Using Optimization Of Surface Roughness, Amol Suresh Sonje

Mechanical & Aerospace Engineering Theses & Dissertations

Robust design improves the fundamental function of the product or process considering noise factors in DOE. G. Taguchi has made significant advances in the use of experimental design. Taguchi methods are criticized on the basis of failure to deal with interactions, use of SIN ratio and lack of sequential nature of investigation. Response Surface Methodology deals with designing models that represents response in terms of various factors affecting it. Optimization of surface finish is achieved using both Taguchi Methods and Response Surface Methodology.

Dual response approach is a combination of Taguchi methods and RSM techniques in which primary response is …

Computational Aerodynamics Study Of Ahmed Body Car Model, Rajat Trehan

Mechanical & Aerospace Engineering Theses & Dissertations

Vehicle Aerodynamics has been the focus of study by researchers for centuries. This interest can be owed to increasing demand on fuel efficiency, vehicle top speed and acceleration performance. Interior aerodynamics, such as engine cooling, air conditioning, wind noise, stability, and cross wind sensitivity play key role in customer satisfaction. Hence a complete understanding of flow around the vehicle is prerequisite to achieve any of the above parameters. Aerodynamic development of motor vehicle is expensive. Much capital must be invested in test facilities such as wind tunnels and climate tunnels. The models are costly and at the beginning of a …

Strategy For Product Reusability Based On Technical And Economic Model, Srikanth Uppuluri

Mechanical & Aerospace Engineering Theses & Dissertations

Reusing old components is considered the most profitable End-of-Life strategy in the modern day scenario of sustainable manufacturing. Though there is increasing pressure on the product designers worldwide to make reuse possible, the functionality of the products and the economic feasibility have been the main considerations for manufacturers in evaluating the reuse strategy. The quality level of the used product and mainly the economic aspect of disassembling the product have been the main uncertainties confronting the industries to move towards the product recovery strategies like reuse and disassembly. The profitability factor in designing and implementing the technology for disassembly of …

Passive And Active Nonlinear Control Of Ship Roll Motions Using U-Tube Tanks, Thongchai Phairoh

Mechanical & Aerospace Engineering Theses & Dissertations

A U-tube water tank is first designed to roll a ship floating on still water. The 6-degree of freedom (DOF) dynamic model of U-tube tank is derived and the effects of its parameters on ship roll motion are studied. Numerical simulations show that the U-tube tank is an effective stimulator to roll the ship on still water. For a rolling ship, the U-tube tank can be used as a damper to reduce ship roll motion quickly.

Active control of ship roll motion with a proportional and derivative (PD) controller, linear quadratic regulator (LQR), generalized predictive control (GPC), and deadbeat predictive …

Fixture Design For Load Measurement In Friction Stir Welding, Shekhar S. Kulkarni

Mechanical & Aerospace Engineering Theses & Dissertations

In the Friction Stir Welding Process a vertical force is required for plunging the pin or probe of the tool into the workpiece specimen material, and maintaining contact between the shoulder and the substrate. In addition to the vertical force, Friction Stir Welding Process also involves a horizontal force, which is instrumental for the advancement of the tool as the weld progresses. The essential objective of the thesis was to design, manufacture and test a fixture that can be utilized to measure the vertical force as well as the horizontal force. The designing of the fixture was concerned with various …

Processing And Characterization Of High Performance Structural Nanocomposites, Dennis C. Working

Mechanical & Aerospace Engineering Theses & Dissertations

Carbon nanotubes are considered to be a revolutionary material breakthrough due to their unique combination of properties. While many applications for SWCNTs have been projected, realization of these potential uses have been hampered by the high cost of limited supplies of high quality SWCNTs and the difficulty in the development of a suitable processing method that does not damage the filler thus diminishing the desirable properties of this material. In spite of these technical challenges, their potential to enable the fabrication of multifunctional materials is being investigated in earnest. The goal of this thesis is to investigate the feasibility of …

Robustness And Control Of A Magnetically Levitated Transportation System, Grzegorz Oleszczuk

Mechanical & Aerospace Engineering Theses & Dissertations

Electromagnetic suspension of Magnetic Levitation Vehicles (Maglev) has been studied for many years as an alternative to wheel-on rail transportation systems. In this work, design and implementation of control systems for a Maglev laboratory experiment and a Maglev vehicle under development at Old Dominion University are described. Both plants are modeled and simulated with consideration of issues associated with system non-linearity, structural flexibility and electromagnetic force modeling. Discussion concerning different control strategies, namely centralized and decentralized approaches are compared and contrasted in this work. Different types of electromagnetic non-linearities are considered and described to establish a convenient method for modeling …

Gauss-Hermite Integration For Reliability Calculation And Sensitivity Analysis, Nilesh K. Borade

Mechanical & Aerospace Engineering Theses & Dissertations

In the real world, many applications are subjected to uncertainty. A simple illustration would be a structure like a bridge where magnitude and the speed of the loads acting on it are continuously changing. Therefore it becomes essential to study this stochastic or random nature. The thrust of this research is to develop an efficient reliability and sensitivity technique based on stochastic response surfaces (polynomial chaos expansions) constructed using Gauss-Hermite integration. The focus is on calculating the uncertainty propagation using less number of function evaluations since the stochastic response surface needs to be reconstructed at each design cycle. Using the …

Validation Of Finite Element Beam Models, Pavan R. Madhineni

Mechanical & Aerospace Engineering Theses & Dissertations

Finite Element (FE) methods these days are becoming very popular to predict the responses of structures in industries, such as the aerospace and automobile industries. When there is a new design or modification of an existing design, the product must be tested to fulfill the criterion projected by the industry or external agencies before it can be launched. The product must be checked for each and every aspect, and every minute detail of each of the external forces. Hence, it becomes very important to carry out the model validation on the product.

This thesis describes validation of finite element (FE) …

Shape And Size Sensitivity Analysis Of Geometrically Nonlinear Laminated Composite Plates, Nitin R. Mane

Mechanical & Aerospace Engineering Theses & Dissertations

Since major applications of composite laminates involve large deformation, the nonlinear strain-displacement relation in the Von Karman sense has been incorporated here with the first order shear deformation to study bending analysis of composite laminated panels. The finite element model constructed here is an extension of the MIN3 element which is a displacement based element developed by Hughes and Tessler. The element avoids shear locking in the thin bending regime and achieves computational efficiency. The resultant nonlinear matrix equation is solved for analysis of composite panels by using the Newton-Raphson iterative method. Based upon the nonlinear matrix equation, the shape …