Mechanical Engineering Commons^™

Cycloidal-Drive Joint Design For Wearable Exoskeletons, Abhi J. Rawal

Theses

This thesis's scope was to construct a highly back drivable and compact joint design that can be used for wearable exoskeletons specifically designed to assist with rehabilitation. A compact cycloidal gear transmission was designed to satisfy the compactness requirement while ensuring the minimum torque is required for backdriving the mechanism. The joint was designed based on the compact cycloidal drive specifications, and the backdrivability test was performed to measure the minimum torque required (1.20 Nm) to backdrive. The joint design incorporates various important features such as rotation lock feature to prevent hyperextension, a housing design that offers the benefit of …

Mechanics Of Binder-Particle Interactions In Composite Battery Electrodes, Richard Johnson

Theses

A study into the particle level mechanics of polymer binder and active material used in composite lithium-ion batteries (LIB) has been conducted. Silicon is highly sought after material that can be used as an active material in a composite anode. Its high theoretical capacity can result in batteries that can store more energy than current LIBs, but high volume expansion of Si during charge/discharge cycles leads to rapid capacity fade and poor cyclic life. Understanding the stress that is generated in the binder and the active material due to the volume expansion has not been fully understood. In this study …

Tomato Puree Convective Heat Transfer Simulation Using Boussinesq Approximation, Matteo Fabbri

Theses

With the advance of new technologies, the food industries are requiring systems that allow to produce the desired products with faster rates at cheaper costs. In this case, the study was initiated with the purpose to better understand what happens inside a package containing tomato puree when this is heated above 343 K in a tunnel pasteurizer. If the fluid must reach the thermal and microbiological condition of “pasteurization”, the system must guarantee that the temperature (around 343° Kelvin) is kept for a certain time allowing to pasteurize even the cooler package’s fluid-particle. The faster the system can heat the …

Effect Of Turbostratic Orientations And Confined Fluid On Mechanical Strength Of Bi-Layer Graphene: A Molecular Dynamics Study, Nil B. Dhankecha

Theses

The rise of graphene as a reinforcement material in the last decade has been exponential owing to its superior mechanical properties. This one atom thick 2D material is applicable in many industries related to nanomechanical, nanoelectronics and optical devices. Despite its strength and superior properties, single-layer graphene tends to be unstable in a free-standing form. This led to active use of bi-layer and multilayered graphene in many of the above-stated applications. Though properties of single-layer graphene have been extensively investigated both computationally as well as experimentally for over a decade, bilayer graphene and its turbostratic form are still under research. …

Mechanical Design Automation: A Case Study On Plastic Extrusion Die Tooling, Allen Prasad Varghese

Theses

The Skills Gap in Mechanical Engineering (ME) Design has been widening with the increasing number of baby boomers retiring (Silver Tsunami) and the lack of a new generation to acquire, practice and perfect their knowledge base. This growing problem has been addressed with several initiatives focused on attracting and retaining young talent; however, these types of initiatives may not be timely for this new group to be trained by an established Subject Matter Expert (SME) group. Automated Engineering Design provides a potential pathway to address not only the Skills Gap but also the transfer of information from SMEs to a …

Modelling Of Oxygen Diffusion In Cork, Swapnil Shivputra Rane

Theses

The primary objective of this project is to better understand gas diffusion through natural cork structures by comparing simulations of gas diffusion through natural cork to experimental measurements of oxygen gas diffusion through the same structure. The cork's internal structure is measured using x-ray computed tomography (CT). From the measured internal structure, a simple mapping is assumed converting the measured x-ray computed tomography images into a 3D map of local diffusion coefficient. Specifically, it is assured that the x-ray CT pixel value is inversely proportional to the diffusion coefficient of oxygen through the cork. A diffusion model for the cork …

Effect Of Temperature On The Fracture Behavior Of Lead-Free Solder Joints, Patrick Thompson

Theses

The objective of the present study is to examine the effect of temperature on the fracture behavior of Cu-SAC305-Cu joints. To this end, double cantilever beam (DCB) specimens, consisting of a thin layer of Sn96.5Ag3.0Cu0.5 (SAC305) solder sandwiched between two copper bars, fabricated under standard surface mount (SMT) processing conditions are fractured under various temperatures with a MTS machine equipped with an environment chamber. The load-displacement behavior corresponding to crack initiation and the subsequent toughening before ultimate failure and the displacements near crack tip are recorded and used to calculate the fracture energy release rates. The fracture surfaces and the …

Shock Wave Interaction With A Fluid Filled Cylinder Experimental Methods, Praveen Kumar Baba Siddabattuni

Theses

In the recent wars of Iraq and Afghanistan, many soldiers sustained bTBI (blast-induced traumatic brain injury). The blasts are created by extensive use of improvised explosive devices (IED’s). Whether pure blast-shock waves cause TBI or what is the mechanism of injury are not fully known. Research efforts are underway to find answers to these questions.

The primary objective of this project is to understand how the shockwave interacts with a fluid-filled cylinder of different thicknesses. Here, the cylinder is idealized as head and the fluid filled inside it as the brain material. The primary interest here is, how the pure …

Effect Of Endplate On The Blast Wave Profile In A Compressed Gas Shock Tube, Sudeepto Kahali

Theses

Blast related brain injuries are commonly encountered in the recent wars of Iraq and Afghanistan increased use of improvised explosive devices (IEDs). An estimated 20% of veterans returning from these operations have suffered traumatic brain injuries (TBI). The mechanisms and long-term effects of the injury are not fully understood, and extensive research effort is being focused toward identifying the mechanisms of primary blast injury. When a pure shock-blast wave encounters a subject, in the absence of shrapnel, casing or gaseous products, the loading is termed as primary blast loading, and its effects can be studied using shock tubes.

The wave …

Development Of A Finite Element Method For Light Activated Polymers, Craig Hamel

Theses

Traditional Shape Memory Polymers (SMPs) belong to a class of smart materials which have shown promise for a wide range of applications. They are characterized by their ability to maintain a temporary deformed shape and return to an original parent permanent shape. The first SMPs developed responded to changes in temperature by exploiting the difference in modulus and chain mobility through the glass transition temperature. However, in recent years, new SMPs have been developed that respond to other stimuli besides temperature; these can include electricity, magnetism, changes in chemical concentration, and even light.

In this thesis, we consider the photo-mechanical …

Influence Of Lateral Boundaries In Tapped Densification Of Granular Materials, Nathaniel Ching

Theses

Granular systems are widely present in the world. Soil, pharmaceutical pills, and silos filled with grain all are examples of granular systems. Experiments have long established an empirical understanding of granular systems, but an analytical understanding has been much more difficult to establish. One of the behaviors of a granular system that is well documented but poorly understood is the change in density the system undergoes when excited, also known as the densification process.

This thesis investigates the densification process of a tapped granular system using Discrete Element Model (DEM) simulations. Contact interactions in the simulations obey a well-established inelastic …

The Mechanical Testing Of Single Nanofiber, Pratik Manohar Dahule

Theses

Polymer nanofibers exhibit properties that make them a favorable material for the development of tissue engineering scaffolds, filtration devices, sensors, and high strength lightweight materials. Perfectly aligned PLLA Nanofibers were fabricated by an electrospinning technique under optimum conditions and the diameter of the electrospun fibers can easily be tailored by adjusting the concentration of the polymer solution. To align the nanofibers, special arrangement was made in terms of two aluminum plates. Good alignment of polymer nanofibers on specimen was confirmed by SEM observation. The effect of different electro-spinning parameters on maximum fiber length, average fiber diameter, diameter uniformity, and fiber …

Design And Fabrication Of A Tapped Densification Apparatus For Bulk Solids, Joshua H. De Jong

Theses

Experiments are commonly used to ascertain the flow properties of bulk solids. One such property is a measurement quantity known as the tapped density. Here, a container of granular material is subjected to a long sequence of discrete taps, after which the bulk density - the total mass divided by the volume occupied –- is determined. Current technology exists to achieve the maximum tap density by subjecting a container to a user defined number of taps at a specific, predetermined amplitude and frequency. However, the final bulk density is known to be dependent on the tap parameters. It can therefore …

Stochastic And Deterministic Dynamics Investigation Of The Microstructure Of Granular Materials, Vishagan Ratnaswamy

Theses

Granular materials are ubiquitous in one's daily life. They can be found in the cereal you eat, the sugar you put in your coffee or the sand you walk on in the beach. The study of granular materials has a rich history dating back to the 17th century where Kepler studied the packing of particles. The compaction of granular materials is a problem that is studied by using theory, experiments and simulations. While these studies have yielded some important results, there still are many details about the mechanisms of granular compaction that are unknown.

In this thesis, the density relaxation …

Dem Simulated Radial And Axial Pressure In A Cylindrical Granular Column, Meng Cui

Theses

The study of packed beds of granular spheres and their applications are of great interest to industries, and one of the most important subjects that has been studied is cylindrical beds. In 1895, H. A. Janssen discovered that in a vertical cylinder the pressure measured at the bottom does not depend upon the height of the filling in contrast to Newtonian fluids that possess linear hydrostatic pressure equilibrium. One of assumptions of his theory stated that the horizontal pressure is proportional to the vertical. In this thesis, this physical hypothesis is investigated using Discrete Element Simulations of inelastic with a …

Ignition Of Metal Powder By Electrostatic Discharge Stimulation, Ervin Beloni

Theses

Energetic formulations with metal fuel additives are extensively used in propellants, explosives, pyrotechnics, and incendiaries. Currently, replacement of regular metal powders with nanocomposite metal-based materials is being considered. Such nanocomposite reactive materials are capable of very high reaction rates while maintaining the high combustion enthalpies characteristic of metals. However, such novel reactive nano-materials are often highly sensitive to impact, friction, and electrostatic discharge, making them difficult to handle. In particular, their high electrostatic discharge sensitivity (ESD) was reported. While ESD testing is very common and standardized, the mechanisms of powder ignition by electric spark remain unclear. This project is aimed …

Design Of Gait Rehabilitation System, Andriy Pletenetskyy

Theses

This thesis describes the conceptual design of an innovative robotic rehabilitation machine whose purpose is to help in the recovery of people with motor function disabilities. The machine is smaller, simpler and cheaper than current solutions on the market yet it delivers same functionality.

The conceptual development of the gait rehabilitation system also features a human model with average anthropometric dimensions that allows better visualization and understanding of the actual machine operation. The human model is kinematically coupled to the machine and the whole assembly presents a complex mechanism that closely simulates gait training session.

Three-dimensional modeling and analysis techniques …

Fully Dense Aluminum-Rich Aluminum Copper Oxide Powders For Energetic Formulations, Demitrios Stamatis

Theses

The thermite reaction between Al and CuO is well known and highly exothermic. For a conventional thermite mixture comprising mixed metal and oxide powders, this reaction is rate limited by the slow heterogeneous mass transfer at the metal and oxide interface. The relatively low reaction rate and a difficult ignition have restricted practical applications for this reaction. For newly developed, nano-composed thermites, the interface area can be substantially increased resulting in a much higher reaction rate and a new range of possible applications. Nanocomposite Al-CuO materials are produced using a technique referred to as arrested reactive milling. Regular metal and …

Phase Transfer In A Collision Between A Droplet And Solid Spheres, Zheng Shen

Theses

The hydrodynamics of a liquid droplet impinging on a particle is of direct relevance to many engineering applications. The mechanism of heat and mass transfer during the droplet solid collision is essential to the design and operation of many industrial systems. However, very limited systemic research is available to describe the droplet impact on hot solid spheres.

This paper aims to establish a systematic investigation of phase transfer due to the droplet-solid impact, by both experimental and modeling approaches. The targeted phase transfer includes the surface attachment, mass of vaporization, heat transfer to droplet and its partition between vaporization and …

Numerical Analysis Of The Operation Of A Water Cannon, Teymuraz G. Bitadze

Theses

This study was designed to investigate the operational process of a launcher for generation of high speed water projectiles, and it involved the optimization of the geometry of a launcher body. The objective of the optimization of the internal geometry was to increase the effective momentum of the projectile while the optimization of the external geometry resulted in the reduction of the mass of the launcher.

In the course of the optimization of the internal geometry the exit velocity variation was determined, and used to compute an effective projectile momentum, which actually affects a workpiece. In this research, it was …

Burmester Curve And Numerical Motion Generation Of Grashof Mechanisms With Perimeter And Transmission Angle Optimization In Mathcad, Peter J. Martin

Theses

An infinite number of planar four-bar mechanism solutions exist for a series of prescribed rigid-body positions. Given a set of Burmester curves or numerically-generated fixed and moving pivot curves, sorting through the limitless number of possible mechanism solutions to find one that ensures full link rotatibility, satisfies compactness criteria and produces feasible transmission angles can be a daunting task. In this work, two algorithms are developed and presented by which the user can select optimum planar four-bar motion generators (optimum with respect to Grashof criteria, mechanism perimeter criteria and transmission angle criteria) from a set of all mechanism solutions produced …

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

Theses

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

Dry Magnetic Assisted Impaction Mixing Of Sub-Micron Boron And Barium Chromate For A Time Delay Composition, Ryan Barrow

Theses

The objective of this investigation is to improve the mixture homogeneity of, Boron and Barium Chromate, a delay composition called T-10, using a novel dry mixing technique, , called the Magnetic Assisted Impaction Mixing (MAIM). Two additional mixing methods, ultra-sonic mixing and shaker mixing (dry and wet), were used for comparative analysis, to evaluate the mixing effectiveness of the MAIM which was also compared to two Navy mixed T-l0 samples. Characterization of the homogeneity is described by how well boron is effectively distributed throughout the mixture, which is a challenging task since the mixture's composition is 3% Boron versus 97% …

Doppler Ultrasound Technique Used To Determine The Blood Flow Viscosity In The Middle Cerebral Artery Of A Canine Animal Model, Raj P. Ganpath

Theses

The cerebral blood flow velocity in the middle cerebral artery of an canine animal model was measured using the Doppler Ultrasound technique. A transducer was designed with a 20 MHz piezoelectric crystal and used for the application. An in vitro calibration system was designed and machined for the purpose of testing and calibrating every transducer before using it in vivo. Preliminary tests included experiments on the in vitro system and measurement of blood flow velocity in the human wrist artery (metacarpal artery). The effect of using different transmission media (agarose and gelatin) was determined through the many in vitro and …

A Gait Generation Mechanism For Leg Rehabilitation Therapy, Yazan Ahmad Manna

Theses

While most take their ability to walk for granted, some are unable to walk secondary to any number of pathologies, such as traumatic brain injury (TBI), spinal cord injury (SCI), cerebrovascular accidents (CVA), cerebral palsy (CP), multiple sclerosis (MS), Parkinson's disease, as well as various orthopedic conditions. Decreased activity has been shown to be associated with rapidly deconditioning and other co-morbidities. Rehabilitation techniques that afford patients the ability to begin reconditioning through walking sooner may ultimately enhance their return to a better quality of life.

The overall goal of this study is to design a gait generation mechanism for rehabilitation …

Heat Transfer Model For The Ignition Of Metal Powder On A Heated Filament, Trent Stanton Ward

Theses

The thermal processes leading to ignition of metal powders in environments that experience rapid temperature changes are currently poorly understood. In this research, a methodology for studying and quantification of such processes is developed. In the experimental case study, the ignition temperature of Mg powder coated on the surface of an electrically heated filament is detected optically at different heating rates. To interpret the results, a heat transfer model has been developed for a multilayer powder coating on top of an electrically heated filament. The coating is modeled using a hexagonal close packed geometry and the heat transfer equations are …

Combustion Of Aerosolized Spherical Aluminum Powders And Flakes In Air, Binu Zacharia Eapen

Theses

Combustion rates and completeness of aerosolized spherical aluminum powders and flakes are compared using constant volume explosion experiments. The comparison of particles and flake sizes was made based on their specific surface areas determined using the Brunauer-Emmett-Teller (BET) method and respective "BET diameters". It is observed that the rates of pressure rise and rates of flame propagation were higher for aluminum powders with BET diameters of about 2 to 5 μm compared to aluminum flakes for which the BET diameters were under 1 μm In agreement with the flame propagation rates, the overall completeness of combustion was also higher for …

Magneto-Rheological Fluid Orthosis For Suppressing Tremor, Hyoung-Joo Yeo

Theses

Tremor is a common movement disorder that occurs with specific neurological conditions. This condition may seriously impact daily living activities. The aim of the present study is to evaluate the possibility of the development of a wearable technology that is capable of exerting torques at a user's joints for suppressing tremor.

This thesis is based on the concept of "smart structures" which are made of Magneto-Rheological (MR) fluid that can dynamically alter its viscosity under magnetic field. The wearable tremor suppressing orthosis needs several conditions. It should be safe, light weight, simple and small in structure, and easily attachable. An …

Characterization Of Aluminum Powder Ignition, Salil Mohan

Theses

Heating rate effect and particle size effect on ignition temperature of Al powder were studied to collect data for development of a possible Al powder ignition model. Aluminum ignition is associated with a highly accelerated burn rate and high combustion enthalpy. A new ignition model, which can adequately interpret these conditions, is needed to develop better propulsion fuels, explosives and incendiaries that use Al as an additive. This experimental program was focused on preparing framework for characterization of ignition kinetics of Al powder by determining the ignition temperature for different, systematically varied, heating rates and particle size. The experimental setup …

Synthesis Of Nano/Micro Particles Using Supercritical Method And Particle Characterization, Abhijit Aniruddha Gokhale

Theses

The thesis work consists of the two parts, jet behavior of solvents (ethanol and acetone) and the particle formation using SAS method. In the first part, the study of the effects of process parameters like temperature, pressure, injection velocity and internal diameter of nozzle on liquid jets are studied. The critical pressure for which liquid jet of solvents changes to gas - like jet, is investigated.

In the second part, the experiments are done to study the process of the particle formation using SAS method. Effects of process parameters like pressure, injection velocity of solution, the inner diameter of nozzle …