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Methodology For Analyzing Epoxy-Cnt Phononic Crystals For Wave Attenuation And Guiding, Madhu Kolati 2016 Michigan Technological University

Methodology For Analyzing Epoxy-Cnt Phononic Crystals For Wave Attenuation And Guiding, Madhu Kolati

Dissertations, Master's Theses and Master's Reports

Phononic crystals (PhnCs) control, direct and manipulate sound waves to achieve wave guiding and attenuation. This dissertation presents methodology for analyzing nanotube materials based phononic crystals to achieve control over sound, vibration and stress mitigation. Much of the analytical work presented is in identifying frequency band gaps in which sound or vibration cannot propagate through these PhnCs. Wave attenuation and mitigation analysis is demonstrated using finite element simulation. Engineering principles from current research areas of solid mechanics, solid-state physics, elasto-dynamics, mechanical vibrations and acoustics are employed for the methodology. A considerable effort is put to show that these PhnCs can ...


The Early Stage Wheel Fatigue Crack Detection Using Eddy Current Pulsed Thermography, Jianping Peng, Kang Zhang, Kai Yang, Zhu He, Yu Zhang, Chaoyong Peng, Xiaorong Gao 2016 Southwest Jiaotong University

The Early Stage Wheel Fatigue Crack Detection Using Eddy Current Pulsed Thermography, Jianping Peng, Kang Zhang, Kai Yang, Zhu He, Yu Zhang, Chaoyong Peng, Xiaorong Gao

Review of Progress in Quantitative Nondestructive Evaluation

The in-service wheel-set quality is one of critical challenges for railway safety, especially for the high-speed train. The defect in wheel tread, initiated by rolling contact fatigue (RCF) damage, is one of the most significant phenomena and has serious influence on rail industry. Eddy current pulsed thermography (ECPT) is studied to compensate the Ultrasonic Testing (UT) method for detection these early stage of fatigue cracks in wheel tread. This paper proposes several induction coils, such as linear coil, Yoke coil and Helmholtz coils, based ECPT method to meet the imaging of multiple cracks and irregular surface in wheel tread through ...


Early Detection Of Materials Degradation - Still A Challenge For Conventional And Advanced Materials, To Be Applied For Lightweight Constructions, Norbert Meyendorf 2016 Iowa State University

Early Detection Of Materials Degradation - Still A Challenge For Conventional And Advanced Materials, To Be Applied For Lightweight Constructions, Norbert Meyendorf

Review of Progress in Quantitative Nondestructive Evaluation

Lightweight components for transportation and aerospace applications are designed for an estimated lifecycle, taking expected mechanical and environmental loads into account. The main reason for catastrophic failure of components within the expected lifecycle are material inhomogeneities, like pores and inclusions as origin for fatigue cracks, that have not been detected by NDE. However, material degradation by designed or unexpected loading conditions or environmental impacts can accelerate the crack initiation or growth. Conventional NDE methods are usually able to detect cracks that are formed at the end of the degradation process, but methods for early detection of fatigue, creep, and corrosions ...


The Design And Construction Of A Torque Measuring Arm For An Air Motor, Logan Dearinger 2016 Central Washington University

The Design And Construction Of A Torque Measuring Arm For An Air Motor, Logan Dearinger

All Undergraduate Projects

There is a system efficiency lab that sits in the thermodynamics lab of the Mechanical Engineering Technologies department. To expand this lab, a torque measuring device was needed to measure the torsional force that the pump exerts on the air motor. The expansion of this lab is important to give a better understanding of how the different mechanical parts effect the efficiency of the overall system. The first step in the expansion process was the design of a suitable torque measuring device. The most efficient design was a simple one with minimal moving parts. When the air motor is energized ...


Rheology And Filtration Of Mono- And Bi-Disperse Settling Suspensions, Tejaswi Soori 2016 Iowa State University

Rheology And Filtration Of Mono- And Bi-Disperse Settling Suspensions, Tejaswi Soori

Graduate Theses and Dissertations

Rheological properties are of great interest in oil & gas, pharmaceutical, food, plastics and cosmetic industries which process different types of multi-phase suspensions. Review of existing literature on rheological studies and experiments are conducted to verify the effect of total solid concentration � on the viscosity of mono-disperse and bi-disperse suspensions.

Gravity filtration involves flow of fluid through a porous filter medium and a time dependent cake layer which act as additional filter media. Filtration rate and cake build up as a function of time are examined for mono- and bi-disperse suspensions through theory and experimentation. Darcy's Law, which describes fluid ...


Mechanical Behavior Of Nanotwinned Materials-Experimental And Computational Approaches, Hakan Yavas 2016 Iowa State University

Mechanical Behavior Of Nanotwinned Materials-Experimental And Computational Approaches, Hakan Yavas

Graduate Theses and Dissertations

Nanotwinned materials exhibit high strength combined with excellent thermal stability, making them potentially attractive for numerous applications. When deposited on cold substrates at high rates, for example, silver films can be prepared with a high-density of growth twins with an average twin boundary spacing of less than 10 nm. These films show a very strong {111} texture, with the twin boundaries being perpendicular to the growth direction. The origins of superior mechanical and thermal properties of nanotwinned materials, however, are not yet fully understood and need further improvements.

The aim of this research is to develop a connected experimental and ...


Material Removal Modeling And Life Expectancy Of Electroplated Cbn Grinding Wheel And Paired Polishing, Tianyu Yu 2016 Iowa State University

Material Removal Modeling And Life Expectancy Of Electroplated Cbn Grinding Wheel And Paired Polishing, Tianyu Yu

Graduate Theses and Dissertations

Paired polishing process (PPP) is a variant of the chemical mechanical polishing process which facilitates defect mitigation via minimization of maximum force as well as effective planarization via profile driven determination of force gradient. The present embodiment of PPP machine employs two polishing wheels, radially spanning the wafer surface on a counter-gimbaled base. The PPP machine is deployed to experimentally investigate the role of the process parameters on the surface roughness evolution, and the effective material removal rate. Two sets of copper and aluminum blanket layers were polished under a range of applied down force, polishing wheel speed and transverse ...


Fatigue Properties Of Magnetorheological Elastomers And The Design Of Interfacial Layers To Improve Fatigue Life., Yanfen Zhou 2016 Dublin Institute of Technology

Fatigue Properties Of Magnetorheological Elastomers And The Design Of Interfacial Layers To Improve Fatigue Life., Yanfen Zhou

Doctoral

The primary aim of this PhD programme was to understand the fatigue behaviour of magnetorheological elastomers (MREs) and provide a reliable fatigue life predictor for this class of materials. To realise this aim required the study of the dynamic behaviour of MREs using the equi-biaxial bubble inflation test method. Isotropic and anisotropic MREs were fabricated from silicone rubber (SR) filled with soft carbonyl iron (CI) particles. The equi-biaxial fatigue behaviour of these samples was determined using a bubble inflation method. Wöhler (S-N) curves for both isotropic and anisotropic MREs were produced by subjecting the compounds to cycling over a range ...


A Multiphysics Phase Field Model On Melting And Kinetic Superheating Of Aluminum Nanolayer And Nanoparticle, Yong Seok Hwang 2016 Iowa State University

A Multiphysics Phase Field Model On Melting And Kinetic Superheating Of Aluminum Nanolayer And Nanoparticle, Yong Seok Hwang

Graduate Theses and Dissertations

It has been found during the last decade that a nanoscale melting of metal has very distinctive features compared to its microscale counterpart. It has been observed that a highly non-equilibrium state can result in extreme superheating of a solid state, which cannot be explained well by thermodynamic theories based on equilibrium or nucleation. An endeavor to find the superheating limit and mechanisms of melting and superheating becomes more complicated when various physical phenomena are involved at the similar scales. The main goal of this research is to establish a multiphysics model and to reveal the mechanism of melting and ...


Modeling Heat And Mass Transfer In Reacting Gas-Solid Flow Using Particle-Resolved Direct Numerical Simulation, Bo Sun 2016 Iowa State University

Modeling Heat And Mass Transfer In Reacting Gas-Solid Flow Using Particle-Resolved Direct Numerical Simulation, Bo Sun

Graduate Theses and Dissertations

Reacting gas-solid flows occur in nature and many industrial applications. Emerging carbon-neutral and sustainable energy generation technologies such as CO2 capture and biofuel production from fast pyrolysis of biomass are examples of reacting gas-solid flows in industry. Fundamental scientific understanding of reacting gas-solid flows is needed to overcome technological barriers for the successful development of these technologies. Multiphase computational fluid dynamics (CFD) simulations are increasingly being used for scale-up of reactors from laboratory to pilot to full-scale plants, and also for evaluation of different design options. Device-scale CFD simulations of reacting gas-solid flow are based on statistical descriptions that require ...


Continuum And Computational Modeling Of Flexoelectricity, Sheng Mao 2016 University of Pennsylvania

Continuum And Computational Modeling Of Flexoelectricity, Sheng Mao

Publicly Accessible Penn Dissertations

Flexoelectricity refers to the linear coupling of strain gradient and electric polarization. Early studies of this subject mostly look at liquid crystals and biomembranes. Recently, the advent of nanotechnology revealed its importance also in solid structures, such as flexible electronics, thin films, energy harvesters, etc. The energy storage function of a flexoelectric solid depends not only on polarization and strain, but also strain-gradient. This is our basis to formulate a consistent model of flexoelectric solids under small deformation. We derive a higher-order Navier equation for linear isotropic flexoelectric materials which resembles that of Mindlin in gradient elasticity. Closed-form solutions can ...


Phase Boundary Propagation In Mass Spring Chains And Long Molecules, Qingze Zhao 2016 University of Pennsylvania

Phase Boundary Propagation In Mass Spring Chains And Long Molecules, Qingze Zhao

Publicly Accessible Penn Dissertations

Martensitic phase transitions in crystalline solids have been studied and utilized for many technological applications, including biomedical devices. These transitions typically proceed by the nucleation and propagation of interfaces, or phase boundaries. Over the last few decades, a continuum theory of phase transitions has emerged under the framework of thermoelasticity to study the propagation of these phase boundaries. It is now well-established that classical mechanical and thermodynamic principles are not sufficient to describe their motion within a continuum theory, and a kinetic relation must be supplied to complete the constitutive description. A few theoretical techniques that have been used to ...


Mechanics Of Impulse Force Reduction For Mitigating Dump Truck Vibrations Under Hislo Conditions, Danish Ali 2016 Missouri University of Science and Technology

Mechanics Of Impulse Force Reduction For Mitigating Dump Truck Vibrations Under Hislo Conditions, Danish Ali

Masters Theses

"The deployment of large capacity shovels and dump trucks, for achieving economic bulk production capacities, has resulted in high impact shovel loading operations (HISLO). These large shovels generate high impact forces when loading dump trucks with over 100-ton passes under gravity. The impact forces also generate high frequency shock waves, which cause severe truck vibrations, and thus, expose dump truck operators to high levels of whole body vibrations (WBV). The dynamic impact force generates these vibrations, and thus, there is a need to develop efficient technologies to eliminate or reduce its impact. Existing literature and industry practice show that this ...


Electromechanics Of An Ocean Current Turbine, Vasileios Tzelepis 2015 University of New Orleans

Electromechanics Of An Ocean Current Turbine, Vasileios Tzelepis

University of New Orleans Theses and Dissertations

The development of a numeric simulation for predicting the performance of an Ocean Current Energy Conversion System is presented in this thesis along with a control system development using a PID controller for the achievement of specified rotational velocity set-points. In the beginning, this numeric model is implemented in MATLAB/Simulink® and it is used to predict the performance of a three phase squirrel single-cage type induction motor/generator in two different cases. The first case is a small 3 meter rotor diameter, 20 kW ocean current turbine with fixed pitch blades, and the second case a 20 meter, 720 ...


Finite Element Analysis (Fea) Study Of The Thermal Stress Concentrations In Planar-Type Sodium Sulfur (Nas) Secondary Batteries, Jeffrey P. Colker 2015 University of Wisconsin-Milwaukee

Finite Element Analysis (Fea) Study Of The Thermal Stress Concentrations In Planar-Type Sodium Sulfur (Nas) Secondary Batteries, Jeffrey P. Colker

Theses and Dissertations

The importance of a reliable and safe way to store energy, and allow for on-demand usage, has led to much research in the field of secondary battery development. The thesis herein explores a technology that has shown promising results when implemented in large-scale energy grid applications. Though the technology has proven viable in both load-leveling on existing grids as well as serving to legitimize renewable energy sources, the development of such advanced battery systems is not without challenge. Sodium-sulfur (NaS) secondary cells have shown promising results when implemented in the aforementioned energy storage applications. One of the main drawbacks to ...


Field And Laboratory Study Of The Flàajökull Glacier, Iceland, William Russell Jacobson, Jr. 2015 University of Wisconsin-Milwaukee

Field And Laboratory Study Of The Flàajökull Glacier, Iceland, William Russell Jacobson, Jr.

Theses and Dissertations

The increased surface melting of the outlet glaciers of the Vatnajökull Ice Cap has a profound affect on the dynamics of the ice-bed couple and landform genesis. Soft-bedded glaciers are largely inaccessible, which creates a problem. One challenge is to understand the complex interactions of the glacier bed and its resultant depositional and deformational landform systems. This study investigates an outlet glacier from the Vatnajökull Ice Cap, described herein as the Fláajökull glacier system. To circumvent some of these problems, three separate projects were conducted in this dissertation: (1) magnetic fabric study of effective pressure (difference between the ice-overburden pressure ...


Failure Simulations At Multiple Length Scales In High Temperature Structural Alloys, Chao Pu 2015 University of Tennessee - Knoxville

Failure Simulations At Multiple Length Scales In High Temperature Structural Alloys, Chao Pu

Doctoral Dissertations

A number of computational methodologies have been developed to investigate the deformation and damage mechanism of various structural materials at different length scale and under extreme loading conditions, and also to provide insights in the development of high-performance materials.

In microscopic material behavior and failure modes, polycrystalline metals of interest include heterogeneous deformation field due to crystalline anisotropy, inter/intra grain or phase and grain boundary interactions. Crystal plasticity model is utilized to simulate microstructure based polycrystalline materials, and micro-deformation information, such as lattice strain evolution, can be captured based on crystal plasticity finite element modeling (CPFEM) in ABAQUS. The ...


Investigation Of A Numerical Algorithm For A Discretized Rubber-Belt Continuously Variable Transmission Dynamic Model And Techniques For The Measurement Of Belt Material Properties., Brian Gene Ballew 2015 University of Arkansas, Fayetteville

Investigation Of A Numerical Algorithm For A Discretized Rubber-Belt Continuously Variable Transmission Dynamic Model And Techniques For The Measurement Of Belt Material Properties., Brian Gene Ballew

Theses and Dissertations

A numerical algorithm for modeling the dynamic response of a rubber-belt Continuously Variable Transmission (CVT) belt is recreated. The numerical attributes applied to the algorithm and difficulties with numerical stability are discussed in detail. The degrees of freedom of the system have been expanded to include the dynamics of the engine torque output and vehicle loads such as rolling resistance and aerodynamic drag. This was done to emphasize the use of the model as an analysis tool for simulating CVT/engine/vehicle response. The increased degrees of freedom require the addition of a linear dampening element between belt nodes to ...


Development Of A Two-Fluid Drag Law For Clustered Particles Using Direct Numerical Simulation And Validation Through Experiments, Ahmadreza Abbasi Baharanchi 2015 Florida International University

Development Of A Two-Fluid Drag Law For Clustered Particles Using Direct Numerical Simulation And Validation Through Experiments, Ahmadreza Abbasi Baharanchi

FIU Electronic Theses and Dissertations

This dissertation focused on development and utilization of numerical and experimental approaches to improve the CFD modeling of fluidization flow of cohesive micron size particles. The specific objectives of this research were: (1) Developing a cluster prediction mechanism applicable to Two-Fluid Modeling (TFM) of gas-solid systems (2) Developing more accurate drag models for Two-Fluid Modeling (TFM) of gas-solid fluidization flow with the presence of cohesive interparticle forces (3) using the developed model to explore the improvement of accuracy of TFM in simulation of fluidization flow of cohesive powders (4) Understanding the causes and influential factor which led to improvements and ...


Biomechanical Characerization And Evaluation Of Conservative Clubfoot Correction, Tamara Loren Cohen 2015 Marquette University

Biomechanical Characerization And Evaluation Of Conservative Clubfoot Correction, Tamara Loren Cohen

Dissertations (2009 -)

Congential talipes equinovarus, or clubfoot, affects approximately 200,000 newborns worldwide each year and presents with equinovarus of the hindfoot, as well as cavus and adduction of the midfoot. In addition to bone malformation and displacement, soft tissue contractures encapsulate the medial and posterior aspects of the affected foot. The Ponseti method is a conservative treatment that progressively repositions the clubfoot through weekly casting, followed by bracing. Concerns exist regarding the variability in outcomes, resistance to treatment, and risk of relapse, which occur in approximately 10% of the population. Potential factors contributing to variability and resistant clubfoot include cast material ...


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