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Articles 31 - 60 of 114
Full-Text Articles in Engineering Mechanics
Experimental Characterization Of Stress Relaxation In Glass, Hemanth Kadali
Experimental Characterization Of Stress Relaxation In Glass, Hemanth Kadali
All Theses
Glass viscoelasticity has gained importance in recent years as glass lens molding appeared as a valuable alternative to the traditional grinding and polishing process for manufacturing glass lenses. In the precision lens molding process, knowledge of viscoelastic properties of glass in the transition region, which affect the stress relaxation behavior, is required to precisely predict the final size and shape of molded lenses. The purpose of this study is to establish a step-by-step procedure for characterizing the viscoelastic behavior of glass in the glass transition region using a finite term Prony series of a Generalized Maxwell model. This study focuses …
Charging Kinetics Of Electric Double Layer Capacitors, Clint Cagle
Charging Kinetics Of Electric Double Layer Capacitors, Clint Cagle
All Theses
A recent increase in the popularity of EDLCs and AC-EOF has necessitated a deeper understanding of the structure and charging kinetics of electrical double layers (EDLs) at electrode-electrolyte interfaces. Here, the charging kinetics of EDLs in nanoscale EDLCs is studied by a circuit model, a Poisson-Nernst-Planck (PNP) mo del, and molecular dynamics (MD) simulations. The results of the MD simulations demonstrate a linear charging behavior of EDLs near planar electrodes for both aqueous and organic electrolytes at charging below 90% and time larger than tens of picoseconds. Additionally, we will show that the circuit and PNP models are capable of …
Design And Analysis Of Alternating Spoke Pair Concepts For A Non-Pneumatic Tire With Reduced Vibration At High Speed Rolling, Shashank Bezgam
Design And Analysis Of Alternating Spoke Pair Concepts For A Non-Pneumatic Tire With Reduced Vibration At High Speed Rolling, Shashank Bezgam
All Theses
Recently, Michelin has invented an innovative non-pneumatic tire which has potential for improved handling, grip, comfort, and less rolling resistance when compared to a traditional pneumatic tire. The non-pneumatic wheel is manufactured from a molding process with integrated shear ring and collapsible spokes designed to provide optimal uniform ground contact patch with low rolling resistance. The shear band is constructed from a polyurethane material with imbedded inextensible reinforcements. During high speed rolling in initial testing, the original prototype showed high noise levels at frequencies above 100 Hz. A possible source of noise could be due to vibration initiated from the …
Robust Parameter Design And Finite Element Analysis For A Non-Pneumatic Tire With Low Vibration, Amarnath Proddaturi
Robust Parameter Design And Finite Element Analysis For A Non-Pneumatic Tire With Low Vibration, Amarnath Proddaturi
All Theses
During rolling of a non-pneumatic tire, vibration may be produced by the interaction of collapsible spokes with a shear deformable ring as they enter the contact region, buckle and then snap back into a state of tension. Other potential sources of vibration include the interaction of tire tread with the ground and ring vibration. In the present work, a systematic study of the effects of key geometric design parameters is presented using Taguchi's Robust Parameter Design Method and Orthogonal Arrays.
In the present work, a 2D planar finite element model with geometric non-linearity and explicit time-stepping is used to simulate …
Monitoring Co Concentration In Fuel Cells Using Microcantilever Sensors, Tugba Demir
Monitoring Co Concentration In Fuel Cells Using Microcantilever Sensors, Tugba Demir
All Theses
Estimating the concentration of gases including carbon monoxide (CO) in the hydrogen fuel exiting the reformer and entering the fuel cell is imperative. A high concentration of CO can cause fuel-cell catalyst poisoning, which permanently destroys the cell. Current practices call for utilizing expensive and bulky spectral analyzers to achieve this task. In addition to their high cost, these methodologies, undoubtedly, hinder the portability and self-containment of the cell. To overcome these problems and achieve the desired objectives of a portable, self-contained, and real-time measurement module, this thesis presents and experimentally investigates a new enabling technology based on utilizing an …
Relationships Between Lane Change Performance And Open-Loop Handling Metrics, Robert Powell
Relationships Between Lane Change Performance And Open-Loop Handling Metrics, Robert Powell
All Theses
This work deals with the question of relating open-loop handling metrics to driver-in-the-loop performance (closed-loop). The goal is to allow manufacturers to reduce cost and time associated with vehicle handling development. A vehicle model was built in the CarSim environment using kinematics and compliance, geometrical, and flat track tire data. This model was then compared and validated to testing done at Michelin's Laurens Proving Grounds using open-loop handling metrics. The open-loop tests conducted for model validation were an understeer test and swept sine or random steer test. Four commonly used handling metrics (steady state yaw rate gain, yaw rate damping …
Friction Stir Welding Process And Material Microstructure Evolution Modeling In 2000 And 5000 Series Of Aluminum Alloys, Harshavardhan Yalavarthy
Friction Stir Welding Process And Material Microstructure Evolution Modeling In 2000 And 5000 Series Of Aluminum Alloys, Harshavardhan Yalavarthy
All Theses
Interactions between the rotating and advancing pin-shaped tool (terminated at one end with a circular-cylindrical shoulder) with the clamped welding-plates and the associated material and heat transport during a Friction Stir Welding (FSW) process are studied computationally using a fully-coupled thermo-mechanical finite-element analysis. To surmount potential numerical problems associated with extensive mesh distortions/entanglement, an Arbitrary Lagrangian Eulerian (ALE) formulation was used which enabled adaptive re-meshing (to ensure the continuing presence of a high-quality mesh) while allowing full tracking of the material free surfaces. To demonstrate the utility of the present computational approach, the analysis is applied to the cases of …
Straight Line Braking Performance Of A Road Vehicle With Non Linear Tire Stiffness Formulation, Anup Khekare
Straight Line Braking Performance Of A Road Vehicle With Non Linear Tire Stiffness Formulation, Anup Khekare
All Theses
The capability of a road vehicle equipped with an Anti-Lock Braking System (ABS) to come to a safe stop depends on factors such as dynamic force between tire and road, surface adhesion coefficient, and the vertical profile of the road. When in panic, a driver's reaction is to step hard on the brakes to make the vehicle stop as soon as possible. Although the use of modern technologies such as ABS and Electronic Stability Control (ESC) have reduced the number of accidents significantly, any further improvement in stopping distance would only complement these technologies.
Michelin has undertaken the development of …
Characterization And Enhancement Of Sensing Properties Of Piezoelectric Materials With Applications To Vibration Suppression, Siddharth Aphale
Characterization And Enhancement Of Sensing Properties Of Piezoelectric Materials With Applications To Vibration Suppression, Siddharth Aphale
All Theses
This thesis undertakes the study of piezoelectric properties of polymer-based fabric and film sensors. An enhancement in piezoelectric properties of such sensors, as noted through earlier work, is observed with increasing weight ratios of nanomaterials dispersed in the polymer matrix. A comprehensive mathematical model using cantilever beams is developed to analyze this enhancement both qualitatively and quantitatively. An experimental setup is also developed to implement the proposed real time signal processing necessary to collect required data towards the characterization. In order to distinguish piezoelectric materials from other materials, study of the frequency response of developed fabric sensors to periodic chirp …
On The Modeling Of Energy Harvesters And Analysis Of Their Response Under Time-Varying Frequency Excitations, Thiago Seuaciuc-Osorio
On The Modeling Of Energy Harvesters And Analysis Of Their Response Under Time-Varying Frequency Excitations, Thiago Seuaciuc-Osorio
All Theses
Energy harvesting is a process by which otherwise wasted ambient energy can be captured and transformed into a useful form. Historical examples of this concept include windmills, sailing ships, and waterwheels. Modern technologies and current energy needs have brought this same concept to a smaller scale wherein small wireless devices with minute energy consumption can be operated autonomously. Today, many critical electronic devices, such as health-monitoring sensors, pace makers, spinal stimulators, electric pain relievers, etc. require minimal amounts of power to function, which permits utilizing energy from their environment to power them. By exploiting the ability of active materials and …
Use Of Orthogonal Arrays For Efficient Evaluation Of Geometric Designs For Reducing Vibration Of A Non-Pneumatic Wheel During High-Speed Rolling, William Rutherford
Use Of Orthogonal Arrays For Efficient Evaluation Of Geometric Designs For Reducing Vibration Of A Non-Pneumatic Wheel During High-Speed Rolling, William Rutherford
All Theses
During high speed rolling of a non-pneumatic wheel, vibration may be produced by the interaction of collapsible spokes with a shear deformable ring as they enter the contact region, buckle and then snap back into a state of tension. In the present work, a 2D planar finite element model with geometric nonlinearity and explicit time-stepping is used to simulate rolling of the non-pneumatic wheel. Vibration characteristics are measured from the FFT frequency spectrum of the time-signals of perpendicular distance of marker nodes from the virtual plane of the spoke, thickness change in the ring between spokes, and ground reaction forces. …
Development Of A Rigid Ring Tire Model And Comparison Among Various Tire Models For Ride Comfort Simulations, Norm Frey
All Theses
One vehicle subassembly that is of great importance to automobile manufacturers for tuning final vehicle performance is the pneumatic tire. Pneumatic tires present themselves as unique tuning tools as they 1) are the sole link between the roadway surface and the integrated vehicle suspension, chassis and steering systems, and 2) provide a wide range of tunability over many vehicle performances, including handling (steering feel as well as chassis dynamics), traction (braking, driving, and cornering), and ride comfort (roadway isolation). Therefore the vehicle manufacturing industry continues to research and refine various aspects of tire modeling to improve up-front integrated tire/vehicle CAE/CAD …
Survey Of Concurrent Engineering Environments And The Application Of Best Practices Towards The Development Of A Multiple Industry, Multiple Domain Environment, Jonathan Osborn
All Theses
This thesis investigates the best practices of fifteen existing Concurrent Engineering Environments (CEE). A CEE is defined as any environment, from physical to virtual, designed to facilitate concurrent engineering with multiple domain experts real time. All existing environments surveyed have been focused on the aerospace industry showing significant reductions in design time and cost. I have identified hardware, software, and peopleware as three major classifications as well as sixteen subcategories with which to compare the different CEEs. The success in reducing time and cost of designs seen in the aerospace industry with the introduction of CEEs can and should be …
Dynamic Finite Element Simulation Of Ultrasonic Consolidation, Daniel Mccullough
Dynamic Finite Element Simulation Of Ultrasonic Consolidation, Daniel Mccullough
All Theses
Ultrasonic Consolidation (UC) is a promising solid state rapid manufacturing process that provides the ability to create functional, multilayered, and often geometrically complex parts. This thesis seeks to address one of the primary obstacles faced when using the process, namely the apparent build height limit encountered when using UC to construct high aspect ratio specimens. A fully transient, three dimensional Finite Element model is created to study the dynamic behavior of an ultrasonically consolidated part during the UC process. The model is used to find the cause of bond failure at the build height limit and a potential way to …
Predictive Energy Management In Smart Vehicles: Exploiting Traffic And Traffic Signal Preview For Fuel Saving, Behrang Asadi
Predictive Energy Management In Smart Vehicles: Exploiting Traffic And Traffic Signal Preview For Fuel Saving, Behrang Asadi
All Theses
This master thesis proposes methods for improving fuel economy and emissions of vehicles via use of future information of state of traffic lights, traffic flow, and deterministic traffic flow models.
The first part of this thesis proposes use of upcoming traffic signal information
within the vehicle's adaptive cruise control system to reduce idle time at stop lights and lower fuel use. To achieve this goal an optimization-based control algorithm is formulated for each equipped vehicle that uses short range radar and traffic signal information predictively to schedule an optimum velocity trajectory for the vehicle. The objectives are timely arrival at …
A Study In The Information Content, Consistency, And Expressive Power Of Function Structures In Mechanical Design, Chiradeep Sen
A Study In The Information Content, Consistency, And Expressive Power Of Function Structures In Mechanical Design, Chiradeep Sen
All Theses
In engineering design research, function structures are used to represent the intended functionality of technical artifacts. Function structures are graph-based representations where the nodes are functions, or actions, and the edges are flows, or objects of those actions. For the consistent description of artifact functionality, multiple controlled vocabularies have been developed in previous research. The Functional Basis is one such vocabulary that provides for a set of verbs and a set of nouns, organized in the three-level hierarchy. This vocabulary is extensively studied in design research. Two major application of this vocabulary are the Design Repository, which is a web-base …
Development Of A Falling Sphere Instrument For High-Resolution Neutral Wind Measurements In The Mesosphere And Lower Thermosphere, Arpan Shah
All Theses
Passive falling spheres launched from small rockets have been used extensively in the past to measure the winds and densities in the mesosphere. In principle, the same technique can be extended to higher altitudes that cover the lower thermosphere, in addition to the mesosphere. The main difficulties are that accelerations decrease rapidly with height due to the decreasing atmospheric density and rigid spheres are required at higher altitudes, which implies larger mass and smaller accelerations. Accelerometers with broad dynamic range and high sensitivity are required for the measurements, but such devices are not readily available. We describe an instrumented falling …
A Priori Analysis Of Subgrid Scalar Phenomena And Mass Diffusion Vectors In Turbulent Hydrogen-Oxygen Flames, Justin Foster
A Priori Analysis Of Subgrid Scalar Phenomena And Mass Diffusion Vectors In Turbulent Hydrogen-Oxygen Flames, Justin Foster
All Theses
Direct Numerical Simulations (DNS) of high pressure, turbulent H2/O2 non-premixed flames employing real gas effects, detailed chemistry, multicomponent, differential, and cross diffusion are conducted. The results of these simulations are analyzed to provide important subgrid information relevant to Large Eddy Simulation (LES) of turbulent combustion. Subgrid filtered scalar dissipation and scalar variances, species concentrations, reaction rates, and flame temperature are presented as a function of mixture fraction. The analysis also includes a detailed comparison of the actual filtered mass flux vectors with their corresponding forms evaluated with the filtered primitive variables. The results show a reasonable correlation …
Development Of A Nonlinear Ride Quality Model To Aid In Tweelå© Parameter Selection, Marc Paradiso
Development Of A Nonlinear Ride Quality Model To Aid In Tweelå© Parameter Selection, Marc Paradiso
All Theses
The ride comfort of a vehicle is very important to both automotive and tire manufacturers. Unfortunately the ride comfort provided by the tire has an inverse relationship with the handling ability of the vehicle. Michelin has sought to decouple ride comfort and handling capability by developing a non-pneumatic tire they have dubbed the TWEEL©. To better understand what effects fitting a TWEEL with specific characteristics would have on the ride comfort of a vehicle a computer simulation was developed to study the effects of TWEEL stiffness and deflection on ride comfort.
The vehicle model used in the simulation is a …
Taxonomy Of Physical Prototypes: Structure And Validation, Ashwin Michaelraj
Taxonomy Of Physical Prototypes: Structure And Validation, Ashwin Michaelraj
All Theses
This thesis introduces a taxonomy of physical prototypes, and validates the proposed taxonomy by five different approaches. The proposed taxonomy is validated by, (i) checking the orthogonality of individual elements of the taxonomy, (ii) benchmarking the taxonomy with existing classifications of prototypes, (iii) demonstrating its utility by applying it to classify different prototypes, (iv) building a prototype database containing 35 different prototypes, and (v) consistency evaluation of the prototype database using a description logic based software called ProtŽgŽ.
The results indicate that the proposed taxonomy is capable of distinguishing prototypes with greater accuracy when compared to existing classifications. The orthogonality …
An Evaluation Of Function-Based Representations And Information Archival In Engineering Design, Benjamin Caldwell
An Evaluation Of Function-Based Representations And Information Archival In Engineering Design, Benjamin Caldwell
All Theses
Recent research in function-based design includes the development of a vocabulary of functions, the Functional Basis, and a repository of products and their functions. Many design tools are being developed around this vocabulary and repository to support conceptual design. The usefulness of these tools, however, is dependent on the quality of the vocabulary and the information contained in the repository. In this research, both the vocabulary and the repository are empirically evaluated to understand their strengths and limitations. A statistical analysis is performed on function models in the repository to determine the frequency of usage of Functional Basis terms. It …
Independent Torque Distribution Management Systems For Vehicle Stability Control, Indrasen Karogal
Independent Torque Distribution Management Systems For Vehicle Stability Control, Indrasen Karogal
All Theses
Vehicle Dynamics Control (VDC) systems, also called Electronic Stability Control (ESC) systems, are active on-board safety systems intended to stabilize the dynamics of vehicle lateral motion. In so doing, these systems reduce the possibility of the driver's loss of control of the vehicle in some critical or aggressive maneuvers. One approach to vehicle dynamics control is the use of appropriate drive torque distribution to the wheels of the vehicle. This thesis focuses on particular torque distribution management systems suitable for vehicles with independently driven wheels.
In conducting this study, a non-linear seven degree-of-freedom vehicle model incorporating a non-linear tire model …
Nonlinear Finite Element Analysis Of Tweel Geometric Parameter Modifications On Spoke Dynamics During High Speed Rolling, Maya Ramachandran
Nonlinear Finite Element Analysis Of Tweel Geometric Parameter Modifications On Spoke Dynamics During High Speed Rolling, Maya Ramachandran
All Theses
The acoustic signature and noise produced by non-pnuematic wheels such as the Michelin TWEELTM is a critical design criteria for automotive and other mobility applications. The TWEELTM structure consists of three basic parts: (1) a circular deformable 'shear beam', (2) collapsible spokes and (3) a rigid hub. During high speed rolling the TWEELTM produces acoustic noise which is hypothesized to be due to resonant vibration of the TWEELTM spokes as they enter the contact region, buckle and then snap back into a state of tension. In order to identify and help understand the causes of acoustic noise for a rolling …
Modeling, Analysis And Control Of Flexible Solid-State Hysteretic Actuators, Kushan Vora
Modeling, Analysis And Control Of Flexible Solid-State Hysteretic Actuators, Kushan Vora
All Theses
A distributed parameters modeling and control framework for flexible solid-state hysteretic actuator is presented in this work. For the simplicity of analysis, the actuator dynamic behavior is decoupled and treated separately from the hysteresis nonlinearity. To include the effects of widely-used flexural mechanisms, a mass-spring-damper boundary condition is considered for system. Moreover, the effect of electromechanical actuation is included as a concentrate force at the boundary. The problem is then divided into two parts: first part deals with free motion analysis of system in order to obtain eigenvalues and eigenfunctions using the expansion theorem and a standard eigenvalue problem procedure. …
An Investigation On Spot-Weld Modeling Complexity For Crash Simulation, Srinivasan Vimalanathan
An Investigation On Spot-Weld Modeling Complexity For Crash Simulation, Srinivasan Vimalanathan
All Theses
In order to design car body structures which are safe during crash, modern automotive manufacturers perform both full-scale experimental crash tests and computer simulation of vehicle crash events using commercially available Finite Element Analysis (FEA) packages such as ABAQUS or LS-DYNA. Use of crash simulations significantly reduces the number of real time crash experiments needed and reduces the time required for design changes. However, in order to capture accurately crash behavior during high-speed impact, a large amount of detailed FEA modeling features such as number and types of elements, mesh element size, number of components, different types of connectors, material …
Computational Analysis Of Input-Shaping Control Of Microelectromechanical Mirrors, Thomas Starling
Computational Analysis Of Input-Shaping Control Of Microelectromechanical Mirrors, Thomas Starling
All Theses
Advances in micromachining technology have enabled the design and development of high performance microelectromechanical systems (MEMS). There is a pressing need for control techniques that can be used to improve the dynamic behavior of MEMS such as the response speed and precision. In MEMS applications, open-loop control is attractive as it computes a priori the required system input to achieve desired dynamic behavior without using feedback, thus eliminating the problems associated with closed-loop MEMS control. While the input-shaping control is attractive due to its simplicity, the effectiveness of this control approach depends on the accuracy of the model that is …
Finite Element Analysis Of Carbon Fiber Composite Ripping Using Abaqus, Joy Pederson
Finite Element Analysis Of Carbon Fiber Composite Ripping Using Abaqus, Joy Pederson
All Theses
An energy dissipation system is proposed for use on consumer passenger automotive vehicles and auto racing stock cars. This system will be utilized to protect the occupants from frontal impacts with stationary or near stationary objects. The system will be affixed to the front of the car's primary structure. It is proposed to replace the traditional steel bumper currently in use. This system will not increase the weight of the car, nor will it adversely affect the aerodynamics of the body. The system will improve the crashworthiness of the vehicle. Advanced composites will be the primary sacrificial element in the …
Ultracapacitor Assisted Powertrains: Modeling, Control, Sizing, And The Impact On Fuel Economy, Dean Rotenberg
Ultracapacitor Assisted Powertrains: Modeling, Control, Sizing, And The Impact On Fuel Economy, Dean Rotenberg
All Theses
This thesis investigates possible fuel economy gains attainable by a combination of high-power density ultracapacitors (also called supercapacitors) and an induction motor integrated into a conventional vehicle powertrain for power assistance.
Periods of quick acceleration require a much higher power output from an automobile than what is encountered under more typical driving conditions. A simple kinetic energy calculation can show that accelerating a 2000 kg vehicle (roughly the size of a Ford Explorer SUV) from 0 to 60 mph in 10 seconds requires almost 70 kW of power, in addition to the power needed to overcome road and air drag …
Non-Linear Finite Element Analysis And Optimization For Light Weight Design Of An Automotive Seat Backrest, Prasanna Balaji Thiyagarajan
Non-Linear Finite Element Analysis And Optimization For Light Weight Design Of An Automotive Seat Backrest, Prasanna Balaji Thiyagarajan
All Theses
ABSTRACT
With the goal of reduced weight, free-size finite element based optimization with constraints on stresses and displacements of a commercially available automotive seat backrest frame manufactured from several stamped and welded low carbon ductile steel sheets is performed using OptiStruct linear optimization package from Altair under the loading requirements of mandatory ECE R-17 backrest-moment test and headrest test for vehicles sold in Europe. In the free-size optimization, sheet metal thickness in a finite element shell model of the backrest frame are design variables with stress and displacement limits as the constraints, with an objective to minimize mass. Using the …
Analysis Of Non Load Bearing Two Component (2k) Adhesives; Under The Automotive Hemming Process Variations; Thermogravimetric, Calorimetric And Composition Analyses, Kameswara Nara
All Theses
The work focuses on the analysis of non-load bearing, two component adhesives used in joining the automotive closures. The study is concerned with the thermo-gravimetric and the calorimetric attributes of the 2K adhesive. The study includes the impact of the robotic applicators capability, in terms of the mixing ratio between the resin and the hardener, and the mechanical mixing quality. A Fourier Transform Infrared Spectroscopy (FTIR) procedure analyzes the adhesive chemical groups and tracks the growth and decay of the hydroxyl and epoxy peaks. Additionally, the cure-rate based on a reaction-type, is investigated through a Differential Scanning Calorimetry (DSC). The …