Engineering Commons^™

Self-Diffusion In Misoriented Aluminum (111) Substrates After Jump-To-Contact, Noah Kane Manuel

Mechanical Engineering Master's Theses

Self-diffusion between misoriented aluminum (111) substrates after jump-to-contact (JC) is studied using molecular dynamics simulations. Diffusive behaviors of three twist misorientation angles, 2.45°, 4.40° and 6.00°, are studied at temperatures ranging from 75% to 95% of the melting temperature of aluminum. The existence of the post-JC interface is found to enhance diffusive behavior of atoms near the interface. The 4.40° misorientation angle has the highest pre-exponential factor of diffusion and the lowest activation energy, when compared to the other angles. For all misorientations the activation energies in the direction perpendicular to the JC interface was found to be the lowest. …

Investigation Of An Optimized Occupancy-Driven Hvac Control Strategy And Development Of A Scalable House/Grid Simulation, Kaleb Pattawi

Mechanical Engineering Master's Theses

Energy consumption in buildings is projected to increase more than 50% by 2050. Renewable energy sources are expected to increase and will help alleviate some of the energy demand; however, the intermittent nature of renewables makes it tough to effectively use energy in buildings. Various pricing schemes, including time of use electricity pricing, are used to encourage users to shift loads. Buildings need to be able to proactively react to changing energy sources and electricity prices in order to reduce over-generation of electricity and save money. This work demonstrates an optimized Heating Ventilation and Air Conditioning (HVAC) control strategy that …

Predictive Energy Optimization Model For Grid-Interactive Residential Buildings, Patrick J. Mccurdy

Mechanical Engineering Master's Theses

The consumption and production of energy are more dynamic as distributed energy resources (DER) such as solar photovoltaic (PV) are deployed within the electric distribution system. The traditional energy price at a predetermined rate cannot accommodate these dynamics and can lead to wasted energy and higher costs for both utility companies and consumers. Commercial building and residential energy management systems are usually on a fixed schedule and are not able to respond to changes in energy price instantaneously. There is a need for a real-time pricing structure that can accommodate the fluctuating cost of energy based on supply and demand, …

Feasibility Study Of Serial Hybrid-Electric Systems In Small Aircraft, Kyle Rosenow

Mechanical Engineering Master's Theses

Three different small aircraft, a Diamond DA40, a Cessna Skyhawk 172S and a Cirrus SR22, are used to assess the feasibility of converting an existing aircraft's power system to a serial-hybrid system or an all-electric system. The serial-hybrid system uses a gasoline engine to generate electricity that can power the main electric motor or charge onboard batteries, while the all-electric system uses batteries only and does not carry a gasoline engine. General system designs are proposed, and a calculation model was developed to allow for analysis of the three different aircraft and their variants. The all-electric and serial-hybrid variants are …

Shape Memory Alloy Actuator And Fluid Sampler Development For Extreme Environments, Rachel Stolzman

Mechanical Engineering Master's Theses

Due to the high temperature, high pressure environments of deep-sea boreholes, using conventional electronics to capture temperature-specific water samples may be unreliable or even impossible. In this project, we introduce the use of shape memory alloys as thermal sensors to trigger an actuator to take a water sample at a specified temperature. A custom sampler that can interface with a variety of developed triggers was also designed and fabricated for use in deep-sea boreholes. All of the developed triggers are modular and designed for ease-of-use by users on a drillship with limited tools and equipment. The shape memory alloys used …

Swarm-Based Techniques For Adaptive Navigation Primitives, Nathan Metzger

Mechanical Engineering Master's Theses

Adaptive Navigation (AN) has, in the past, been successfully accomplished by using mobile multi-robot systems (MMS) in highly structured formations known as clusters. Such multi-robot adaptive navigation (MAN) allows for real-time reaction to sensor readings and navigation to a goal location not known a priori. This thesis successfully reproduces MAN cluster techniques via swarm control techniques, a less computationally expensive but less formalized control technique for MMS, which achieves robot control through a combination of primitive robot behaviors. While powerful for large numbers of robots, swarm robotics often relies on “emergent” swarm behaviors resulting from robot-level behaviors, rather than top-down …

Generation And Analysis Of Stop-Hole Geometries For Crack-Like Structures In Auxetic Materials, Max De Jesús Barillas Velásquez

Mechanical Engineering Master's Theses

In this investigation, the main interest was studying low porosity auxetic metamaterials generated out of linearly elastic materials, meaning bodies made out of linearly elastic materials (e.g., metals) that, due to alternating patterns of elongated voids perforated on them, exhibit a negative effective Poisson ratio (property commonly called auxeticity). This kind of metamaterials, often obtained by a pattern of elongated ellipsis, generally face the issue of presenting high stress concentration when loaded. The objective of this study is to solve this problem by adding rounded shapes (stop-holes) at the end of elongated grooves, as a replacement for the previously mentioned …

Development Of Image Analysis Technique For Quantification Of Recrystalization, Bersabe Morales

Mechanical Engineering Master's Theses

Development of metallic components with desired properties for the new generation of applications requires precise design of grain structure. One of the most effective techniques for manipulating grain structure is by controlling the recrystallization process. Although recrystallization has been studied for many years, its proper and fast quantification is still a challenge. This work develops a new image analysis technique for quantification of recrystallization, as an alternative to intensive and expensive electron backscatter diffraction (EBSD) analysis. The image analysis program run on an optical micrograph, detect recrystallized regions and report: fraction recrystallized, average grain size and distribution. To examine the …

The Effect Of Ultrasonic Power In Aluminum Wire Bonding Hardness Profiles, Matthew D. Mckay

Mechanical Engineering Master's Theses

Ultrasonic wire bonding is a critical process used widely across the microelectronics industry. Despite its ubiquity, there is a breadth of literature and ongoing active research into the basic principles of wire bonding. In particular, the effects of ultrasonic bonding on material properties are not fully understood. This thesis presents the effects of different ultrasonic bond powers on material properties. The changes in mechanical properties were measured by collecting Vickers microhardness data and nanoindentation data. The hardness in the bonded wire varied with two parameters: the distance from the bond interface, and the applied ultrasonic power. The hardness varied 5 …

Crystal Misorietation And Defect Generation During Contact Between Two Aluminum Substrates, Milad Khajehvand

Mechanical Engineering Master's Theses

With the use of molecular dynamics simulations, the nanoscale contact between two aluminum substrates at room temperature is studied. The so-called jump-to-contact (JC) phenomenon between (111) surfaces is observed to occur for interfacial distances below 5.8 ± 0.05 Å. This critical distance is approximately equal to 2.5 times the interplanar spacing of (111) planes in a perfect aluminum crystal at 300 K. The critical distance for JC is shown to be higher at higher contact temperatures because of the higher amplitude of atomic vibrations. The effect of employed interatomic potential on the critical distance is also discussed.

The critical distance …

Measuring The Vortex-Shedding Frequency Behind Staggered Cylinders In Cross-Flow, Christopher Clark

Mechanical Engineering Master's Theses

In this thesis, the Strouhal numbers from the downstream cylinder in a two cylinder configuration have been measured experimentally. Special apparatuses were designed to secure the cylinders in the wind tunnel as well as to hold a hot film anemometer probe in the center of the downstream cylinder’s wake. The cylinders were smooth, of equal diameter and extended the entire width of the wind tunnel. Because the cylinders used in this thesis were sufficiently long compared to their diameters and measurements were taken at center span, they were assumed to be infinite. The anemometer was calibrated according to King’s Law, …

Design Of Metamaterials With Graduating Poisson's Ratio Through Periodic Void Patterns, Xiaoming Liang

Mechanical Engineering Master's Theses

It has been known that when introducing alternating elliptical extrusions in a solid material with a positive Poisson's Ratio, the material's effective Poisson's Ratio can become negative. Furthermore, the change in the effective Poisson's ratio depends on two factors: the elliptical extrusions' aspect ratio and the porosity. Using this phenomenon, a study is conducted by combining elliptical extrusions with different aspect ratios and porosity to construct a composite material with gradually varying Poisson's Ratio. Numerical and physical compression studies are conducted to characterize the material's effective properties. The results show that the material can effectively stabilize its own structure under …

Numerical Analysis Of Fatigue Crack Growth Of Low Porosity Auxetic Materials Using The Contour J-Integral, Garivalde S. Dominguez

Mechanical Engineering Master's Theses

Recent studies suggest that auxetic materials such as porous metals with orthogonal periodic void patterns have an increased fatigue life compared to non-auxetic materials. This study provides numerical solution to support the existing experiments with the use of contour J-integral as a parameter of stress intensity factor for computing the number of fatigue life cycle of the materials with auxetic structures. Representative volume elements (RVEs) were constructed to characterize the physical test specimens with void patterns such as ellipse, slot, and stop-hole. Extended finite element method (XFEM) was performed to verify the direction of crack propagation on auxetic materials. Sixty-five …

Development Of Economic Water Usage Sensor And Cyber-Physical Systems Co-Simulation Platform For Home Energy Saving, Joe Singer

Mechanical Engineering Master's Theses

In this thesis, two Cyber-Physical Systems (CPS) approaches were considered to reduce residential building energy consumption. First, a flow sensor was developed for residential gas and electric storage water heaters. The sensor utilizes unique temperature changes of tank inlet and outlet pipes upon water draw to provide occupant hot water usage. Post processing of measured pipe temperature data was able to detect water draw events. Conservation of energy was applied to heater pipes to determine relative internal water flow rate based on transient temperature measurements. Correlations between calculated flow and actual flow were significant at a 95% confidence level. Using …

Material Characterization Of Intermetallic Compound Formation With Respect To Thermosonic Bonding Duration, Mahin Khan

Mechanical Engineering Master's Theses

Intermetallic Metallic Compounds (IMCs) formation is a common cause for wire bond failures. This research studied the effect of US vibration duration on IMC formation and growth in Copper-Aluminum (Cu-Al) wire bonded samples. Wire bonded samples, using 2.5 mil (63.5 μm) thick Palladium coated Copper wire, is ultrasonically bonded on a 2 cm thick Aluminum (1”x1”) coupon. Segmented bonding technique using 200 gf force and 220 gf force are applied during segment 1 and segment 2 of the bonding respectively. Ultrasonic (US) vibration frequency of 115-117 khz and a bonding temperature of 175°C is used. A pair of 5 samples …

Evaluation Of Heat Available From Calcium Chloride Desiccant Hydration Reaction For Domestic Heating In San Francisco, Ca, Michael Giglio

Mechanical Engineering Master's Theses

Thermochemical energy storage has the potential to support the use of solar thermal energy collection in ways that traditional thermal energy storage, like sensible and latent heat storage, have fallen short. Thermochemical energy storage has been shown to have higher storage capacities than sensible and latent storage for dehumidifying applications and does not require insulation like sensible and latent heating do. Sensible heating is focused on maintaining an increased temperature of a storage medium while latent heat storage is focused on maintaining a phase of the storage material. Both sensible and latent heat storage have been shown to have lower …

Computerized Heat Transfer Modeling For Solar Powered Water Purification System, Houtan Neynavaee

Mechanical Engineering Master's Theses

Since drinkable water resources are limited, as the human population increases it is predicted that providing pure water is a future human challenge. However, a huge resource of the water exists on the earth surface in seas and oceans, which are not proper for drinking and cultivate. Exploiting of a solar powered water purification system is an economy and environment-friendly solution to this human problem.

In this thesis, we present computerized heat transfer model for solar powered water purification system. This Model can be used for calculating the heat transfer, system temperature, and other variable parameters such as boiler pressure, …

Influence Of Slippery Pacemaker Leads On Lead-Induced Venous Occlusion, Sagar Bhatia

Mechanical Engineering Master's Theses

The use of medical devices such as pacemakers and implantable cardiac defibrillators have become commonplace to treat arrhythmias. Pacing leads with electrodes are used to send electrical pulses to the heart to treat either abnormally slow heart rates, or abnormal rhythms. Lead induced vessel occlusion, which is commonly seen after placement of pacemaker or implantable cardiac defibrillators leads, may result in lead malfunction and/or superior vena cava syndrome, and makes lead extraction difficult. The association between the anatomic locations at risk for thrombosis and regions of venous stasis have been reported previously. The computational studies reveal obvious flow stasis in …

Hybrid Fuzzy Logic And Extremum Seeking Attitude Control Of Solar Sail Spacecraft, Nikolai Kalnin

Mechanical Engineering Master's Theses

This thesis explores four controllers applied to the attitude control of a solar sail craft with control masses with the goal of showing benefits over more standard control schemes. The controllers examined in this paper are: 1) a PID controller that incorporates a discrete extremum seeking algorithm, 2) a type-1 fuzzy logic controller that incorporates a discrete extremum seeking algorithm, 3) a type-1 fuzzy logic controller, and 4) a type-2 fuzzy logic controller. The first two controllers are examined for their ability to quickly converge to a set of optimal gains over time. The latter two controllers are evaluated for …

Object Manipulation Using A Multirobot Cluster With Force Sensing, Matthew H. Chin

Mechanical Engineering Master's Theses

This research explored object manipulation using multiple robots by developing a control system utilizing force sensing. Multirobot solutions provide advantages of redundancy, greater coverage, fault-tolerance, distributed sensing and actuation, and reconfigurability. In object manipulation, a variety of solutions have been explored with different robot types and numbers, control strategies, sensors, etc. This research involved the integration of force sensing with a centralized position control method of two robots (cluster control) and building it into an object level controller. This controller commands the robots to push the object based on the measured interaction forces between them while maintaining proper formation with …

A Molecular Dynamics Study Of Self-Diffusion Along A Screw Dislocaton Core In Face-Centered Cubic Crystals, Siavash Soltanibajestani

Mechanical Engineering Master's Theses

The topic of this research is self-diffusion along a 1⁄2 〈110〉 screw dislocation core in face-centered cubic metals. Using molecular dynamics, self-diffusion along a screw dislocation core in four FCC metals, aluminum, copper, nickel and silver is investigated. In all metals under study except in Ag, the results show high diffusivity along the core even in the absence of any preexisting point defects (intrinsic diffusion). Enhanced self-diffusion due to screw dislocations is more remarkable in Al and Ni than in Cu. This behavior has been related to the stacking fault energy and dissociation width of partial dislocations.

The simulations show …

Fuzzy Attitude Control Of Solar Sail, Joshua Baculi

Mechanical Engineering Master's Theses

This study presents various fuzzy type controllers for a solar sail. First, a Twin Parallel Distributed Compensator (TPDC) is built for a Takagi-Sugeno fuzzy model of the solarsail. The T-S fuzzy model is constructed by linearizing the existing nonlinear equations fo motion of the solar sail. The T-S fuzzy model is used to solve a set of linear matrix inequalities to derive state feedback controller gains. The TPDC controls the solar sail using a combination of reaction wheels and roll stabilizer bars for attitude control and trim masses for disturbance rejection. The TPDC tracks and stabilizes the solar sail to …

An Algorithm For Calculating The Inverse Jacobian Of Multirobot Systems In A Cluster Space Formulation, Christopher Jude Waight

Mechanical Engineering Master's Theses

Multirobot systems have characteristics such as high formation re-configurability that allow them to perform dynamic tasks that require real time formation control. These tasks include gradient sensing, object manipulation, and advanced field exploration. In such instances, the Cluster Space Control approach is attractive as it is both intuitive and allows for full degree of freedom control. Cluster Space Control achieves this by redefining a collection of robots as a single geometric entity called a cluster. To implement, it requires knowing the inverse Jacobian of the robotic system for use in the main control loop. Historically, the inverse Jacobian has been …

Passive Unitized Regenerative Fuel Cell (Purefc) For Energy Storage Applications, Sandeep Lele

Mechanical Engineering Master's Theses

Passive Unitized Regenerative Fuel Cell (PUReFC) prototypes were designed, fabricated, and tested as new energy storage devices capable of meeting demands in offgrid applications. Although flooded lead-acid batteries are typically used to provide low cost energy storage, improper disposal infrastructure and lack of education on battery maintenance can lead to serious health concerns. A Passive Unitized Regenerative Fuel Cell can generate energy in a sustainable manner and possesses the ability to run in reverse, providing energy storage capability.

As Proton Exchange Membrane (PEM) fuel cells rely on effective internal water transport to provide stable operation, an energy efficient flood mitigation …

Effects Of The Fiber Distribution And Number Of Nearby Fibers On The Thermal Conductivity For Aligned Cnt-Silicon Oil Composites, Diana Grandio

Mechanical Engineering Master's Theses

Carbon Nanotubes (CNT) are seen as promising materials for thermal transport applications. The high thermal conductivity and structural flexibility of the CNT present them as very attractive components to be used as particle fillers in thermal interface materials. It is important to understand the effective thermal conductivity for CNT-matrix composites at high CNT volume fraction.

In prior work, an effective medium approach (EMA) has been developed to evaluate composite physical properties such as thermal conductivity, dielectric function or elastic modulus (C-W Nan, Prog. Mat. Sci. V 37, 1993). This model combined with the Kapitza interface resistance can predict the effective …

Molecular Dynamics Study On The Grain Growth In Nanocrystalline Aluminum, Jielong Yin

Mechanical Engineering Master's Theses

In recent years, nano-materials have been a popular direction of research in the field of materials science. Nanocrystalline aluminum has been of particular intrest among the nano-materials. This thesis describes the results of three-dimensional molecular dynamics simulations that have been performed to study grain growth in nanocrystalline FCC aluminum. This project built the models by using the Voronoi geometry method to study the grain growth mechanism, grain boundary structure and the effects of temperature and grain size on the crystal structure and grain growth by Energy Analysis, Radial Distribution Function (RDF) analysis, and investigating changes in Centro symmetric parameters.

The …

Investigation Of Thermal Properties And Latent Heat Reduction Mechanisms In Nanofluid Phase Change Materials, Aitor Zabalegui

Mechanical Engineering Master's Theses

The thermal properties of paraffin-based nanofluids have been examined to investigate the use of enhanced phase change materials (PCMs) for thermal energy storage (TES). PCMs are promising for TES applications, but low thermal conductivity limits their rate of heat exchange with a working fluid. The nanofluid approach has been established as a method of thermal conductivity enhancement, but effects of particle addition on other thermal properties affecting TES are relatively ignored. Significant reduction in latent heat of fusion below traditional effective medium theory has been observed in nanofluids. An experimental study of paraffin nanofluids, containing various diameter multi-walled carbon nanotubes, …

Navigation & Control Of An Automated Swath Surface Vessel For Bathymetric Mapping, Ketan Rasal

Mechanical Engineering Master's Theses

With the abundant amount of water on the earth, the study of underwater terrain plays an important role in the use and sustainability of marine resources. A wide variety of technical systems are used to collect such bathymetric data, and autonomous vehicles are being explored as a manner in which to make this process more cost-effective. Students in Santa Clara University's Robotic Systems Laboratory are contributing to this effort through the development of an autonomous SWATH boat that can create such maps. As part of this thesis work, the navigation and control system of this SWATH boat has been significantly …

Cfd Study On Aerodynamic Effects Of A Rear Wing/Spoiler On A Passenger Vehicle, Mustafa Cakir

Mechanical Engineering Master's Theses

Aerodynamic characteristics of a racing car are of significant interest in reducing car-racing accidents due to wind loading and in reducing the fuel consumption. At the present, modified car racing becomes more popular around the world. Sports cars are most commonly seen with spoilers, such as Ford Mustang, Subaru Impreza, and Chevrolet Corvette. Even though these vehicles typically have a more rigid chassis and a stiffer suspension to aid in high-speed maneuverability, a spoiler can still be beneficial. One of the design goals of a spoiler is to reduce drag and increase fuel efficiency. Many vehicles have a fairly steep …