Digital Commons Network^™

Experimental Evaluation Of A Mixer-Ejector Hydrokinetic Turbine At Two Open-Water Test Sites And In A Tow Tank, Matthew Rowell

Master's Theses and Capstones

For marine hydrokinetic energy to become viable it is essential to develop energy conversion devices that extract energy with high efficiency, and to field-test them in an environment similar to the one in which they are designed to eventually operate. FloDesign Inc., with FloDesign Wind Turbine Corp., developed a Mixer-Ejector Hydrokinetic Turbine (MEHT) that encloses the turbine in a specially designed shroud to increase mass flow through the turbine rotor.

A scaled version of this turbine was evaluated experimentally at two open-water tidal energy test sites, and in a tow tank. State-of-the-art instrumentation was used to measure free stream and …

Multiscale Numerical Modeling And Characterization Of Carbon/Carbon Composites, Borys Drach

Doctoral Dissertations

Carbon/carbon composite is a high-performance material with a unique set of physical and thermo-mechanical properties making it irreplaceable for severe environment aerospace applications. Its complex hierarchical microstructure presents materials scientists and engineers with substantial modeling challenges when it comes to predicting material's behavior under various loading conditions. My research has been focused on characterization, mutliscale modeling and mechanical testing of this composite. A set of new elasticity solutions for the carbon fiber surrounded by multiple layers of pyrolytic carbon represented as a multicoated cylinder is presented on the microscale. On the mesoscale, deterministic and statistical approaches to evaluation of contributions …

Utilization Of Copper Alloys For Marine Applications, Andrew Drach

Doctoral Dissertations

Utilization of copper alloy components in systems deployed in marine environment presents potential improvements by reducing maintenance costs, prolonging service life, and increasing reliability. However, integration of these materials faces technological challenges, which are discussed and addressed in this work, including characterization of material performance in seawater environment, hydrodynamics of copper alloy components, and design procedures for systems with copper alloys.

To characterize the hydrodynamic behavior of copper alloy nets, mesh geometry of the major types of copper nets currently used in the marine aquaculture are analyzed and formulae for the solidity and strand length are proposed. Experimental studies of …

Investigation Of Thermal And Mechanical Effects During Electrically-Assisted Microforming, Adam Jordan

Master's Theses and Capstones

The goal of this research was to investigate Electrically-Assisted Forming (EAF) at the microscale. Past research has suggested that EAF has the potential to overcome microforming difficulties (i.e., increased data scatter caused by the individual grains affecting the global material properties). In this thesis, three point bending results are presented for both classical (non-EA) and EA processes with CuZn30 specimens containing different grain sizes. A more uniform strain distribution was achieved with the EA processes. Although the application of current did not result in the expected forming force reduction, a decrease was observed where a temperature spike occurred (believed to …

Theory And Evaluation Of A Wireless Capacitive Strain Sensor At Ultra High Frequencies (Uhf) For Cnc Applications, Kyle Francis Shaughnessy

Master's Theses and Capstones

A low cost, non-intrusive interdigitated comb capacitive strain sensor for wireless monitoring of CNC tool cutting forces was designed. Wireless resonant strain sensors were fabricated using the capacitive strain sensor and an inductive trace printed on a flexible film. A parallel-plate capacitance model matched experimental results of capacitive sensors tested in bending and torsion. An optimal sensor design of 12 fingers and a 2.54 mm grid length resulted in an average sensor gauge factor of 0.6910 +/- 0.0646 in bending and 0.9091 +/- 0.1406 in torsion. The wirelessly measured resonant strain sensor was measured to have an average gauge factor …

Two Axis Dilatometer Design And Preliminary Study Of Epoxy Microcracking In 3d Carbon Fiber Woven Composites, Jordan Mathew Kusch

Master's Theses and Capstones

Microcracking is an issue which plagues many types of composites today and is more prevalent in the advanced woven composites such as three dimensional woven carbon fiber composites. Understanding and avoiding microcracking is a process which requires special instrumentation to study the formation of microcracks and is capable of measuring stresses inside epoxy during curing. This research develops a test instrument capable of measuring deformations in samples of curing epoxy which can related to triaxial stresses up to and after failure. Our instrument can be used to study the epoxy curing process in a new light and to experiment with …

Development Of Analytical And Experimental Tools For Magnetic Pulse Welding, Ethan Hunter Thibaudeau

Master's Theses and Capstones

A key process parameter in magnetic pulse welding (MPW) is the workpiece velocity, and while some Finite Element Analysis (FEA) packages exist that are capable of modeling these processes, there is a lack of simplified analytical modeling efforts, which are attractive for their simplicity and cost. In this work, an electromagnetic actuator, named a Uniform Pressure Actuator (UPA), is analyzed, designed, constructed, and tested experimentally. The analytical model is shown to predict workpiece velocities accurately and produce an efficient forming and a robust design. Additionally, an alternative method to measure workpiece velocity is presented, implementing a fiber optic, reflectance dependent …

Mean Force Structure And Scaling Of Rough-Wall Turbulent Boundary Layers, Faraz Mehdi

Doctoral Dissertations

The combined roughness-Reynolds number problem is explored from the perspective of ordering of terms in the mean momentum balance. Existing mean velocity and Reynolds shear stress data from zero pressure gradient, rough-wall turbulent boundary layers are used to clarify the nature of the leading order balances across the boundary layer. These existing data are augmented by data from a judiciously chosen set of experiments performed at the University of New Hampshire. These low speed, Laser Doppler velocimetry based experiments were performed over three types of roughnesses. Their purpose is to clarify the trends found in the existing data sets.

By …

Comparison Of Methods For On-Line Calibration Of Cutting Force Models In End Milling, Yong Zhao

Master's Theses and Capstones

Accurate estimation of cutting coefficients is extremely important in end milling process modeling, and it forms the basis of a smart machining system that can be used for process planning and monitoring. Specific applications include feedrate selection based on force constraints and monitoring of tool wear [1, 2].

This thesis investigates five different methods to calibrate the cutting force model coefficients in end milling processes and compares them in terms of cost, efficiency, compliance, accuracy, repeatability and applicability. The five methods are based on: 1. spindle motor power, 2. Kistler average force, 3. Kistler force profile, 4. Smart Tool average …

Calibration And Characterization Of A Low-Cost Wireless Sensor For Applications In Cnc End Milling, Andrew James Harmon

Master's Theses and Capstones

Central to creating a smart machining system is the challenge of collecting detailed information about the milling process at the tool tip. This work discusses the design, static calibration, dynamic characterization, and implementation of a low-cost wireless sensor for end-milling. Our novel strain-based sensor, called the Smart Tool, is shown to perform well in a laboratory setting with accuracy and dynamic behavior comparable to that of the Kistler 3-axis force dynamometer. The Smart Tool is capable of measuring static loads with a total measurement uncertainty of less than 3 percent full scale, but has a natural frequency of approximately 630 …

Scale Separation Effects On Mechanisms Of Boundary Layer Turbulence, Caleb Morrill Winter

Master's Theses and Capstones

Correlations between specific velocity and vorticity components dictate how the distributions of mean momentum and turbulence kinetic energy are realized in the turbulent boundary layer. For turbulent inertia to remain dynamically significant at arbitrarily high Reynolds number, differences of these correlations must remain non-zero. This motivates the study of velocity vorticity products under the influence of increasing scale separation. Through the use of both laboratory and field data, scale separation between relevant velocity and vorticity components is shown to increase with distance from the wall and Reynolds number. Time-delayed correlations between the vertical velocity and spanwise vorticity fluctuations reveal that …

Waste Heat Measurement And Recovery Options In An Investment Casting Process, Patrick Timothy Kilar

Master's Theses and Capstones

In this research, the waste heat emitted from two ovens and a boiler used in the investment casting manufacturing process by New Hampshire based Hitchiner Manufacturing Inc. Co. was determined. This was achieved with measured temperature and standard volume flow rate data gathered from the exhaust stacks using a thermal anemometer. Pressure in the stacks and density were also determined using a differential pressure transducer and combustion analyzer transducer, respectively. The thermal anemometer collected data continuously over a period of 1 week per stack. To support and protect the transducers during the experiments, tripods and enclosures were designed, fabricated and …

Identification Of System Parameters For End Milling Force Simulation With Tool And Workpiece Compliance, Min Hyong Koh

Master's Theses and Capstones

A Smart Machining System being developed at UNH has the potential to produce high quality machined parts in minimum time. Integral to the success of this system is the ability to accurately simulate cutting forces. In this current work, a time-domain milling simulation is developed with a tool-workpiece compliance model to predict dynamic cutting forces. The simulation computes milling forces, tool deflections, and workpiece vibration (surface waviness).

The accuracy of the simulation depends on finding reliable system parameters. In this work, an end milling parameter identification method is developed using linear predictive coding (LPC) and Extended Kalman Filtering. The milling …

Control Of A Large Scale Wind Turbine Utilizing A Fluid Drive, Matthew Foley

Master's Theses and Capstones

As wind turbines grow in size there are added strains within the mechanical structure that need to be mitigated to improve machine life. The current area of greatest concern is the premature failure of the gearbox box due to torque variations along the drive train. This thesis incorporates a fluid coupler into the turbine's drive train. Three different controllers are developed for this model with the goal of minimizing the torque variations seen by the gearbox and providing better generator speed regulation.

The result of this study shows that the addition of the fluid coupler is a major improvement to …

Analytical And Numerical Modeling Of Performance Characteristics Of Cross-Flow Hydrokinetic Turbines, Alex J. Johnston

Master's Theses and Capstones

A model for cross-flow axis hydrokinetic turbines based on blade element theory (BET) was developed. The model combines an extensive experimental and numerical high Reynolds number data set for symmetric airfoils with governing equations to predict performance characteristics of the turbines. In this model the freestream velocity and the turbine's rate of rotation are not coupled hydrodynamically; experimental calibration of the model for a specific turbine design is necessary. The calibrated model uses velocity data from a tidal energy site to predict power and energy yield over a full tidal cycle. The experimentally calibrated model is compared to a single …

Accelerometer Calibration For Nasa's Magnetospheric Multiscale Mission Spacecraft, Benjamin M. Jenkins

Master's Theses and Capstones

This thesis presents several methods for the on-board and/or ground-based calibration of accelerometers for the spacecraft (s/c) of the NASA Magnetospheric Multi-Scale (MMS) Mission during mission operation. A lumped bias is estimated to correct for the total effect of the MMS accelerometer sensor bias, orthogonal misalignment and the shift in the s/c's center of mass.

Various estimation techniques are evaluated and compared, including both dynamically driven real-time filters/observers and post processing batch algorithms. Both methods are shown to accurately determine lumped bias, so long as the s/c inertia tensor is well known. If, however, there is any uncertainty in the …

On The Ability Of Indentation To Capture The Anisotropic Elastic Properties Of The Pyrolytic Carbon, Nikolay Timoshchuk

Master's Theses and Capstones

We used micro- and nanoindentation, macroscopic strain gage methods and FE studies to correlate the indentation modulus and the macroscopic in- and out-of-plane Young's moduli of transversely isotropic pyrolytic carbon. The out-of-plane indentation modulus of bulk PyroC was comparable with predicted values and more than a factor of two higher than the out-of-plane Young's modulus. The in-plane indentation modulus was significantly lower than predicted values which we attribute to nanobuckling of graphite-like planes. Polarized light microscopy studies on carbon-carbon composite samples infiltrated at 10, 20, 30 kPa demonstrated that the increase in pressure leads to lower texture of the PyroC …

Analytical And Numerical Prediction Of Localized Necking In Sheet Metal Forming Processes, Raed Zuhair Hasan

Doctoral Dissertations

The goal of this research is to investigate, develop and validate analytical and numerical tools that can accurately predict failure in sheet metal forming operations. The strain-based forming limit curve (FLC) is one of the tools to predict the maximum permissible strains of thin metallic sheets which are loaded in the plane of the sheet to different states of stress. It may be used to assess forming operations in the press shops as well as unintentional deformations, such as vehicle, aircraft, or train crashes. The accurate prediction of failure in sheet metal stamping can shorten product lead times, decrease tooling …

A Computational Fluid Dynamics Study Of Two-Phase Flows In The Presence Of Surfactants, Yuanyuan Cui

Doctoral Dissertations

Drop formation in co-flowing fluids and drops rising in a tube are important in applications such as microencapsulation and enhanced oil recovery. A hybrid volume-of-fluid method with a front-tracking scheme is developed to study two-phase flows in the presence of surfactants at finite Reynolds numbers. Both fluids can be Newtonian or shear-thinning, and surfactants are soluble in the adsorption-desorption limit. A drop in the co-flowing geometry typically breaks up at the primary neck. The drop breaks faster with smaller volumes as the outer flow rate increases or the drop viscosity decreases. When surfactants are present, they accumulate in the neck …

An Experimental And Analytical Study Of The Mechanism Of Material Modification When A Bias Is Applied Between Afm Tip And Gold And Highly Oriented Pyrolytic Graphite, Anjali Parkhi

Master's Theses and Capstones

The fabrication of nanostructures is of great importance for the continued development of nanodevices and molecular electronics. While field assisted tip based techniques are proposed to be versatile nanofabrication techniques that can be used for atomic-scale surface modification of wide variety of materials, the mechanism of material transport is not well understood. This research was performed to better understand the mechanisms of surface modification when the voltage bias is applied in ambient conditions; in particular, the conditions that Liu et al.1,2 proposed will cause material transport.

We studied the evolution of the current voltage behavior of a doped silicon AFM …

Design And Development Of A Debris Flow Tracking "Smart Rock", Matthew J. Harding

Master's Theses and Capstones

This thesis covers the design and development of a Smart Rock sensor package to be used in U.S. Geological Survey research of debris flow phenomena. This instrumented Rock, containing inertial sensors and pressure sensors, provides information about the movement of the flow as well as the pressures seen within the flow. The goal of the sensor package is to use this information to track the position of a particle in the flow with an accuracy of 1 m over the course of 10 s..

It is found that using an ad hoc filtering method provides the required level of accuracy. …

Development Of Engineering Tools To Analyze And Design Flexible Structures In Open Ocean Environments, Judson Decew

Doctoral Dissertations

Methods to effectively predict system response in marine settings are critical in the engineering design process. The high energy ocean environment can subject structures to large wave and current forces, causing complex coupled motions and loads. This research focused on the development of effective methods to predict flexible system response and the structural integrity of marine High Density Polyethylene (HDPE) components. Numerical modeling tools were developed to analyze and design flexible structures in open ocean environments. Enhancements to the University of New Hampshire's Aqua-FE finite element computer program were performed, including expansion of the element library to include spherical geometries …

Wireless Sensor Integrated Tool For Characterization Of Machining Dynamics In Milling, Christopher Adam Suprock

Doctoral Dissertations

A first step towards practical sensing in the machining environment is the development and use of low cost, reliable sensors. Historically, the ability to record in-process data at an end mill tool tip has been limited by the sensor location. Often, these sensors are mounted on the material workpiece or the machine spindle at significant physical distance from the cutting process. Of specific interest are the problems of tool chatter which causes limitations to productivity and part quality. Although tool chatter is a substantial issue in machining, it remains an open research topic. In this research, a sensor integrated cutting …

Characterization Of The Wave Bottom Boundary Layer Over Movable Rippled Beds, Sylvia Rodriguez-Abudo

Master's Theses and Capstones

Laboratory-scale observations of a two-dimensional near-bed velocity field were collected using a submersible PIV system. A quasi-steady approach was employed to characterize the observed wave-bottom boundary layer thickness and shear stress. Friction velocities, corresponding to Re * = 15 -- 40, were obtained from a nonlinear least-squares regression of the velocity field averaged over individual half-waves. The regressions show zero-velocity elevations located roughly 1 cm under the ripple crests. The resulting Shields parameter is O(1) greater than the reported threshold for sheet flow, even though bedforms persist. An unsteady analysis using the Double-Averaged Navier-Stokes equations show turbulent and wave-induced stresses …

Investigation Of Microscale Electromagnetic Forming, Reid Vanbenthysen

Master's Theses and Capstones

As microscale devices (e.g., cellular phones, hard drives, and sensors) become smaller in size, so do their individual component dimensions. At the microscale, size effects (i.e., variations in material properties and process parameters as the grain size approaches the specimen feature size) occur in the form of increased data scatter, shape anomalies in the final part geometries and higher springback angles. Similarly, joining at the microscale becomes difficult due to poor joint quality from thermal incompatibilities, the heat-affected zone being near the size of the part and brittle inter-metallic phases. In this research, electro-magnetic (EM) forming was investigated as an …

Investigation Of Variables For Wireless Capacitive Strain Sensing On A Cnc Mill, Justin Patrick Bray

Master's Theses and Capstones

As demand in the manufacturing sector increases, so does the need for greater process throughput and reduced component variability. These two objectives can be achieved by a process known as 'smart machining'. Smart machining utilizes sensors inside the machining environment to relay information to the machine controller. Most sensor systems adversely affect the machine dynamics, by reducing the machining envelope or reducing the machine's stiffness, or require physical connections to conditioning electronics. In this research, variables regarding a resonantly coupled wireless capacitive strain sensor were investigated. A parallel plate capacitive sensor prototype system yielded a strain sensitivity five times greater …

Experimental Investigation Of Helical Cross-Flow Axis Hydrokinetic Turbines, Including Effects Of Waves And Turbulence, Peter Bachant

Master's Theses and Capstones

A test bed for cross-flow axis (CFA) hydrokinetic turbines for the UNH tow and wave tank was designed and built, and two different turbines were evaluated. The effects of waves and turbulence on performance were also observed. Drag (thrust) and mechanical power output were measured at tow speeds of 0.6--1.5 m/s for a Gorlov Helical Turbine (GHT) and a Lucid Spherical (helical) Turbine (LST), both provided by Lucid Energy Technologies, LLP. Overall, the GHT performed with a higher power and drag coefficient than the LST. GHT performance was enhanced by progressive waves, but waves caused stalling at higher tip speed …

The Effect Of Cutting Force Model Coefficient Variability On Process Planning In Milling, Firat Eren

Master's Theses and Capstones

This thesis describes the effect of force model uncertainty on process planning. Specifically, the statistical variations in model predicted machining forces while cutting aluminum, carbon steel, stainless steel and titanium are determined. An accurate estimate of the variability is essential for use in process planning to determine appropriate factors of safety when setting cutting conditions that are both safe and efficient.

Force model coefficient calibration is described and the variability in the coefficients is determined through a least squares regression of a large number of experimental cuts. It is shown that the variability increases with changes in the calibration cutting …

On The Downstream Evolution Of The Mean Momentum Field In Turbulent Shear Wake Flows, Marc R. Bamberger

Master's Theses and Capstones

The evolution of shear wake flow formed from the interaction of two turbulent boundary layers was investigated. Primary interest was given to the post-separation region, very close to the trailing edge of the splitter plate. Two velocity ratios and two trailing edge geometries were explored. Data were acquired using four-element hotwire traverses for multiple downstream locations. With these data sets, a comparison to DNS data, the mean streamwise velocity and its wall normal gradients, Reynolds stress and its gradient, velocity intensities, the mean momentum balance were analyzed. A primary finding is that, post-separation, the inertial terms in the mean momentum …

A Two-Dimensional Hexagonal Network Model Of Alveolar Mechanics, Danielle Nangle

Master's Theses and Capstones

Pulmonary micromechanics (at the scale of alveoli) involves a delicate balance among tissue material properties, geometry, surface tension, pressure and stress distribution. To date, there is not a consensus among alveolar mechanics researchers about how these factors interact, in part because alveoli are so difficult to image and study in vivo. Here, we propose a basic mathematical model of a two-dimensional hexagonal network of mechanically coupled alveoli. We investigate equilibrium configurations of both dry and wet, internally pressurized elastic networks. Specifically, we compute pressure-area curves to quantify the differences among networks with different spring constants, internal pressures, network size and …