Engineering Commons^™

An Analytical Design Of Experiments Method For Fatigue Constrained Design Optimization Of A 3d Printed Structure, Ashish Pokharel

Mechanical and Aerospace Engineering Theses - Archive

A design of experiments approach has been used to analytically determine a low cycle fatigue (LCF) constraint for use in design optimization of 3D printed structures. In context of metal additive manufacturing, the process of melting, solidification and consolidation of metal powder introduces very high temperature gradient field within the build which in turn results in high compressive stresses at the core and tensile stresses at the outer surface of the part after it has cooled down to room temperature post build. An approach of finite element modeling in ANSYS Additive has been used to develop a residual stress profile …

Sensor Tasking For Satellite Tracking Utilizing Observability Measures, Mitchel T. Mcdonald

Mechanical and Aerospace Engineering Theses - Archive

In this thesis, novel observability-measure based sensor tasking methods are studied for satellite tracking applications. The tasking is performed by first computing the Hellinger Distance between ground/space based sensors and space objects, and then the measure is utilized for selecting the sensors that maximize observability. Several other measures such as the Fisher Information Gain, Largest Lyapunov Exponent, and Shannon Information Gain have also been utilized and the performance of these measures are computed against each other. The object's state estimates are obtained using nonlinear estimation techniques. The Extended Kalman Filter, Unscented Kalman Filter, and Bootstrap Particle Filter are compared within …

Design And Development Of Flexible Mems-Based Ph Sensor For Agricultural And Biomedical Applications, Shardul Sonu Pawar

Mechanical and Aerospace Engineering Theses - Archive

The purpose of this study is to demonstrate a novel method of using a flexible MEMS-based pH sensor for agricultural and biomedical applications. The first part of the thesis involves demonstration of the capability of our pH sensor for monitoring pH level change in the food product. The pH sensor we have developed consists of Iridium Oxide (IrOx) and Silver Chloride (AgCl) sensing electrodes. The sensor is designed to monitor and sustain long-term continuous usage, which makes it suitable for a wide variety of agricultural based applications. The electrochemical potential generated between IrOx and AgCl electrode is monitored and further …

Enhancing Tensile Strength Of Fdm Parts Using Thermal Annealing And Uniaxial Pressure, Rhugdhrivya Rane

Mechanical and Aerospace Engineering Theses - Archive

Additive manufacturing has been a revolutionary and disruptive technological development in the field of design and manufacturing with Fused deposition modelling (FDM) being at the forefront of this technology. But it is seen that parts printed using FDM suffer from an inherent deficiency of weak tensile strength in the out of plane direction (z-direction) thus limiting their application. This issue of weak z-direction strength is due to the weak Inter-bead bond strength of adjacent polymer interfaces. The purpose of this work is to increase this Inter-Bead bond strength thus increasing the overall tensile strength of the part. In this work, …

Inducing Vibro-Tactile Sensation At Mesoscale, Sudip Hazra

Mechanical and Aerospace Engineering Theses - Archive

Haptics, the feeling of touch, has primarily been used to provide a person a general sensation such as vibration using a joystick or cellphone. But haptics has gradually developed to a stage where it is investigated for virtual and augmented reality environments. Vibro-tactile based feedback is a modality employed to provide a more realistic and localized sensation. This research focuses primarily on providing vibro-tactile feedback at the mesoscale level on the fingertips. A research platform for mesoscale vibro-tactile feedback has been investigated and developed. The software is based on LabVIEW and could generate a number of different and distinct waveform …

Minimizing Structural Jitter In Optical Sensor Systems Using Parametric Dynamic Response Optimization, Richard Lynn Scott

Mechanical and Aerospace Engineering Dissertations - Archive

Deployed in manned and unmanned aircraft, military and commercial ground vehicles, and security and monitoring systems, optical sensor systems are ubiquitous. Developing an optical sensor system includes calculating image motion due to structural dynamics—hereafter, “structural jitter”—and adjusting system design to reduce structural jitter and meet requirements. The current process for adjusting the structural design to reduce structural jitter is manual, labor intensive, and driven mostly by engineering judgment. This paper proposes a well-defined optimization process that provides a more explicit approach to the structural design and likely will reduce labor as the process matures. This project focuses on employing dynamic …

Electrospinning Approach For The Improvement Of Mechanical And Dielectric Properties Of Anisotropic Nanofiber Mat By Using A Novel Fiber Alignment Technique, Blesson Isaac

Mechanical and Aerospace Engineering Dissertations - Archive

Many advanced applications, including aerospace, can benefit from materials with superior mechanical and dielectric properties. For these applications, most fiber alignment electrospinning research has focused on either mechanical property improvement or dielectric property improvement, but not both simultaneously. Through an improved apparatus design and system parameter optimization, this work develops an electrospinning apparatus that produces an increased electrostatic force and more tightly controlled discharged particle path to enable a more uniform distribution and higher degree of alignment in deposited electrospun material, which results in simultaneous improvement of both mechanical and dielectric properties. The current state-of-the-art in aligned electrospinning techniques are …

Foil Thrust Bearing With Pocket Grooves And Tailored Bump Stiffness Distribution For Improved Static Performance, Nguyen Thao Latray

Mechanical and Aerospace Engineering Dissertations - Archive

Gas foil thrust bearing is one of few axial bearing options for high speed turbomachinery systems. Its advantages include low cost, light weight, generous allowance for component mis-alignment and runout. However, the bearing has low load carrying capacity comparing to other types such as rigid gas bearing and magnetic bearing. This work explores two non-traditional design aspects to improve gas foil thrust bearing’s static performance. The bearing bump foil is redesigned to tailor to the bearing pressure profile; hence induces a more uniform gas film thickness. Simulation using independent elastic foundation model predicts the new tailored bump foil thrust bearing …

Underdamped Motion Of A Microbead In Optical Tweezer And Its Relationship With The Reynolds Number, Vatsal Asitkumar Joshi

Mechanical and Aerospace Engineering Theses - Archive

Optical tweezers can hold and manipulate microscopic objects with the use of a highly focused laser beam. The radiation pressure acting on the object is generally in the range of piconewtons and can be attractive or repulsive based on the reflective indexes of the object and the surrounding medium. Though the advances in the field of Optical tweezers have been enormous in the past few years, only the object's planer motion can be analyzed with the motion capture technology available today. Due to the wide applications of Optical tweezers in the field of biology and physics, the ability to simulate …

Ultraviolet Imager Application For A Cube Satellite, Jason Grillo, Troy Hajjar, Brady Hill

Mechanical Engineering

This document serves as the final design review (FDR) report for the 2018 Cal Poly CubeSat Ultraviolet Imager senior project, sponsored by UC Berkeley Space Sciences Laboratories (SSL). SSL wants to monitor the ionosphere above Earth to gain a better understanding of its properties and particle interactions. Far Ultraviolet (FUV) imaging is a good way to obtain high quality images of the ionosphere and the Earth's auroras, and advancement in optic technologies have made cube satellites (CubeSats) an ideal vessel for a FUV imager, as they are relatively low-cost, lightweight, and can be repeatedly deployed. These CubeSat FUV imagers could …

Effect Of Aerogel On The Thermal Performance Of Corrugated Composite Sandwich Structures, Jacob Dillon Chess

Master's Theses

Current insulation solutions across multiple industries, especially the commercial sector, can be bulky and ineffective when considering their volume. Aerogels are excellent insulators, exhibiting low thermal conductivities and low densities with a porosity of around 95%. Such characteristics make aerogels effective in decreasing conductive heat transfer within a solid. These requirements are crucial for aerospace and spaceflight applications, where sensitive components exist among extreme temperature environments. When implemented into insulation applications, aerogel can perform better than existing technology while using less material, which limits the amount of volume allocated for insulation. The application of these materials into composites can result …

Generating Exploration Mission-3 Trajectories To A 9:2 Nrho Using Machine Learning, Esteban Guzman

Master's Theses

The purpose of this thesis is to design a machine learning algorithm platform that provides expanded knowledge of mission availability through a launch season by improving trajectory resolution and introducing launch mission forecasting. The specific scenario addressed in this paper is one in which data is provided for four deterministic translational maneuvers through a mission to a Near Rectilinear Halo Orbit (NRHO) with a 9:2 synodic frequency. Current launch availability knowledge under NASA’s Orion Orbit Performance Team is established by altering optimization variables associated to given reference launch epochs. This current method can be an abstract task and relies on …

Micro-Nozzle Simulation And Test For An Electrothermal Plasma Thruster, Tyler J. Croteau

Master's Theses

With an increased demand in Cube Satellite (CubeSat) development for low cost science and exploration missions, a push for the development of micro-propulsion technology has emerged, which seeks to increase CubeSat capabilities for novel mission concepts. One type of micro-propulsion system currently under development, known as Pocket Rocket, is an electrothermal plasma micro-thruster.

Pocket Rocket uses a capacitively coupled plasma, generated by radio-frequency, in order to provide neutral gas heating via ion-neutral collisions within a gas discharge tube. When compared to a cold-gas thruster of similar size, this gas heating mechanism allows Pocket Rocket to increase the exit thermal velocity …

Investigating The Effect Of An Upstream Spheroid On Tandem Hydrofoils, Joel Tynan Guerra

Master's Theses

This thesis documents a series of three dimensional unsteady Reynolds Averaged Navier-Stokes CFD simulations used to investigate the influence of an upstream prolate spheroid body on tandem pitching hydrofoils. The model is validated by performing separate CFD simulations on the body and pitching hydrofoils and comparing results to existing experimental data. The simulations were run for a range of Strouhal numbers (0.2-0.5) and phase differences (0-π). Results were compared to identical simulations without an upstream body to determine how the body affects thrust generation and the unsteady flow field.

The combined time-averaged thrust increases with Strouhal number, and is highest …

Energy Harvesting Device Using Ferrofluids Slugs In Microchannels, Omkar Amar Pawar

Mechanical and Aerospace Engineering Theses - Archive

This research proposes a new concept of energy harvesting with the help of oscillating slugs of ferrofluid in microchannels. Ferrofluids are colloidal suspension of paramagnetic nanoparticles which get magnetized in the presence of magnetic field. They can conform to any shape and can be injected easily in intricate spaces. A change in the magnetic flux through the solenoid area produces electromotive force per Faraday’s law. To prove the concept of harvesting energy by having a change in magnetic flux with the help of ferrofluids, several ferrofluid slugs were made to pass through a multi turn solenoid wound around a glass …

Variable Reluctance Virtual Torque Sensor For Automotive Applications, Vivek Iddum

Masters Theses

Torque sensing has been realized as one of the critical aspects in improving the dynamic vehicle performance in automotive systems. This thesis mainly presents the work on the development of a novel torque measurement method based on the estimation of nth-order flywheel angular acceleration from the variable reluctance flywheel speed sensor pulses. The number of firings in the engine determine the order of the harmonic to be used for torque estimation. The nth-order flywheel angular acceleration is computed using a micro-controller with built in timer counter and an associated signal conditioning circuit. The pulses obtained from the flywheel speed sensor …

Process Calibration For Elastically Scaled 3d Printed Models Using Fused Deposition Modeling, Edgar Bernardo Mares

Mechanical and Aerospace Engineering Theses - Archive

With the increase in additive manufacturing capabilities the use of 3D printed models characterize a critical point for evaluating aerodynamic and aeroelastic properties on aircraft configuration. An experimental and computational approach beginning with elastically scaled 3D printed models enables for a case to be defined, developed, and extracted to match aeroelastic test behavior. The basis of this work is supported by aeroelastic tailoring and scaling methods in the application of 3D printed models. To accomplish this, stiffened 3D printed plates are scaled from elastically scaled 3D printed models for stiffness through geometric configurations, different build orientations, and bead thickness as …

Nanosatellite Launch Data-Logger (Sync), Christopher Martin Gerdom

Master's Theses

CubeSat designers are increasingly looking to incorporate delicate structures and optics into their payloads. These delicate payloads, however, may not survive the required absolute-worst-case launch vibration testing needed for flight certification. To help address this problem, and to better match testing conditions to real-world launch environments, this thesis introduces Sync, a compact 1/4U CubeSat payload designed to collect data on the vibrations and thermal environments CubeSats experience inside a deployer on the way to orbit. This data can be used to better understand the launch environment for different vehicles, and help develop new, more realistic testing guidelines that could enable …

Hybrid Processes In Material Removal Of Hard And Brittle Materials, Hossein Mohammadi

Dissertations

New technologies demand new materials with better mechanical, optical, and thermal properties. Materials that are light weight, strong with high resistance to high temperatures, and compatible with a predetermined condition. Such materials usually are challenging to manufacture and process compared to widely available materials such as metals. Ceramics and semiconductors are considered extremely hard and brittle, making them very difficult to cut and manufacture. The other major and fast-growing type of materials are composites (including Ceramic Matrix Composites, CMC) that are also considered very challenging to machine. All these materials have many applications in major industries (i.e. electronics, aerospace, optics, …

Shape-Stabilization Of Pcm/Hdpe Composites With 3d-Printing Applications For Battery Thermal Management, Thomas Benjamin Freeman

Doctoral Dissertations and Master's Theses

Phase-change materials (PCMs) are a useful alternative to more traditional methods of thermal management of Li-ion batteries in electric or hybrid-electric vehicles. PCMs are materials which absorb large amounts of latent heat and undergo solid-to-liquid phase change at near-constant temperature. The goal of this thesis is to experimentally investigate the thermal properties of a novel shape-stabilized PCM/HDPE composite extruded filament. The extruded filament can then be used in a 3D printer for custom PCM/HDPE shapes. These custom PCM/HDPE shapes can be used to help reduce weight, energy consumption, and complexity of the thermal management of the ESS. The PCM used …

Design And Implementation Of Intelligent Guidance Algorithms For Uav Mission Protection, Karina Rivera

Doctoral Dissertations and Master's Theses

In recent years, the interest of investigating intelligent systems for Unmanned Aerial Vehicles (UAVs) have increased in popularity due to their large range of capabilities such as on-line obstacle avoidance, autonomy, search and rescue, fast prototyping and integration in the National Air Space (NAS). Many research efforts currently focus on system robustness against uncertainties but do not consider the probability of readjusting tasks based on the remaining resources to successfully complete the mission. In this thesis, an intelligent algorithm approach is proposed along with decision-making capabilities to enhance UAVs post-failure performance. This intelligent algorithm integrates a set of path planning …

Control Driven Scaling Effects Of Motor And Rotors For Urban Air Mobility Design, Agustin A. Giovagnoli

Doctoral Dissertations and Master's Theses

Through this thesis research the problem of controllability and propulsion associated with scaling-up consumer drones to vehicles that may carry significantly larger payloads, including passenger will be analyzed and tested. Controllability is mainly compromised due to the increasing response time of a larger rpm controlled rotor. This requires a more powerful motor, which translates into heavier and larger devices compromising the thrust-to-weight ratio. Collective pitch control at constant rpm is proposed as a first approach to mitigate the controllability problem, and it is tested in a MATLAB Simulink environment. This solution, linked to a Non-linear Dynamic Inversion controller, is simulated …

Finite Element Modeling And Experimental Characterization Of Knot Configuration Effect On The Mechanical Performance Of Surgical Suture, Arz Y. Qwam Alden

Dissertations

Tendon injuries in orthopedic surgery and sports medicine are escalating; hence there is great interest in improving tendon repair. The integrity of tendon repair depends in part on a combination of suture material, suture size and knot configuration. Recent studies have indicated the failure of surgical knots as a failure mode during surgical repair. Further, there is still no consensus on the ideal (best/safest) surgical knot techniques. Also, this failure mode is related to stress concentrations, which cannot be easily established with traditional tensile testing. Most researchers have focused on the measurement and comparison of the gross structural response of …

Thermal Management Of Satellite Electronics Via Gallium Phase Change Heat Sink Devices, Brian O. Palmer

Theses and Dissertations

The purpose of this research was to determine the effectiveness and feasibility of additively manufactured heat sinks using gallium as a phase change material in the thermal management of satellite electronics. A design was created based on the footprint of an Astronautical Development, LLC Lithium 1 UHF radio and six heat sinks were additively manufactured; two each of stainless steel 316, Inconel 718, and ULTEM 9085. Each heat sink was filled with gallium for testing purposes. Models were created to simulate the behavior of the heat transfer and phase change processes occurring within the heat sink. Additionally, laboratory data was …

Carbon Nanotube Fibers: Mechanical Behavior And The Effects Of The Space Environment, Ryan A. Kemnitz

Theses and Dissertations

Carbon nanotube materials are promising multifunctional materials for incorporation into aerospace structures because of their high tensile strength, high electrical conductivity, and low density. This research aimed to characterize the mechanical failure mechanisms of carbon nanotube fibers and examine the effects of the space environment on their material properties. Tensile tests were conducted at varying strain rates and on fibers of varying gage lengths to examine the underlying molecular failure mechanisms and impact of defects on fiber strength. Tensile strength and elastic modulus were observed to increase with increasing strain rate and decrease with increasing gage lengths. The observed effects …

Experimental And Computational Analysis Of The Interaction Of Carbon And Silicon Ablation Products In Expanding Hypersonic Flows, Brian E. Donegan

Theses and Dissertations

Thermal protection is required for vehicles entering planetary atmospheres to protect against the severe heating loads experienced. Characterization of candidate materials is often done utilizing plasma or arc-jet facilities, which provide steady-state testing of the thermal environments experienced during hypersonic flight, but do not correctly simulate hypersonic flowfields. Conversely, impulse facilities can reproduce flight velocities and enthalpies but have extremely short test times, prohibiting testing of thermal response. Modeling ablation and heating rates, particularly in the wake region, remains a significant challenge due to the complexity of the flowfield. To better understand this complex phenomenon and provide data to validate …

Autonomous Trajectory Planning For Satellite Rpo And Safety Of Flight Using Convex Optimization, Nicholas G. Ortolano

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Optimal trajectory planning methods that implement convex optimization techniques are applied to the area of satellite rendezvous and proximity operations. This involves the development of linearized relative orbital motion dynamics and constraints for two satellites, where one maintains a near-circular reference orbit. The result is formulated as a convex optimization problem, where the objective is to minimize the amount of fuel required to transfer from a given initial condition to the desired final conditions. A traditional rendezvous and proximity operations scenario is analyzed, which includes examples of initial approach, inspection, final approach, and docking trajectories. This scenario may include trajectory …

Design Of An Attitude Control System For A Spacecraft With Propellant Slosh Dynamics, Nolan Coulter

Doctoral Dissertations and Master's Theses

The presence of propellant slosh dynamics in a spacecraft system during a maneuver leads to attitude control system (ACS) performance degradation resulting in attitude tracking errors and instability. As spacecraft missions become more complex and involve longer durations, a substantial propellant mass is required to achieve the mission objectives and perform orbital maneuvers. When the propellant tanks are only partially filled, the liquid fuel moves inside the tanks with translational and rotational accelerations generating the slosh dynamics. This research effort performs a comparative study with different optimal control techniques and a novel application of a model reference artificial immune system …

2018 Summer-Fall Graduate Recognition Program, Propulsion Research Center, Robert Frederick

PRC Graduate Recognition

This program includes the graduate recognition program for summer and fall 2018. Includes photographs, upcoming events, recent publications, and student profiles.

Comparative Analysis Of Electrodynamic Toroidal Radiation Shielding Configurations, Max Rosenberg

Master's Theses

Beyond the protective confines of Earth's atmosphere and magnetosphere, spacecraft are subject to constant bombardment by high-energy charged particles originating from our Sun in the form of Solar Particle Events (SPEs), and from outside the solar system in the form of Galactic Cosmic Rays (GCRs). The harm these particles do can be reduced or mitigated outright through radiation shielding. Because protons and other charged particles comprise most of these radiation particles, strong magnetic fields could be generated around spacecraft to deflect incoming charged radiation particles. This thesis investigates the performance of specific configurations of toroidal superconducting solenoids to generate magnetic …