Matching Items (479)
Description
In order to better understand the physical properties of polyethylene, an extremely common plastic used mostly in packaging, many scientists and engineers use olecular dynamics. To reduce the computational expense associated with traditional atomistic molecular dynamics, coarse-grained molecular dynamics is often used. Coarse-grained molecular dynamics groups multiple atoms into single beads, reducing the number of degrees of freedom in a system and eliminating smaller atoms with faster kinematics. However, even coarse-grained methods have their limitations, one of which is timestep duration, which is limited by the maximum vibrational frequency in the coarse-grained system. To study this limitation, a coarse-grained model of polyethylene was created such that every C 2 H 4 unit was replaced with a bead. Coarse-grained potentials for bond-stretching, bond-bending, and non-bonded interaction were generated using the iterative Boltzmann inversion method, which matches coarse-grained distribution functions to atomistic distribution functions. After the creation of the model, the coarse-grained potentials were rescaled by a constant so that they were less stiff, decreasing the maximum vibrational frequency of the system. It is found that by diminishing the bond-stretching potential to 6.25% of its original value, the maximum stable timestep can be increased 85% over that of the unmodified potential functions. The results of this work suggest that it may be possible to simulate lengthy processes, such as the crystallization of polyethylene, in less time with adjusted coarse-grained potentials. Additionally, the large discrepancies in the speed of bond-stretching, bond-bending, and non- bonded interaction dynamics suggest that a multi-timestep method may be worth investigating in future work.
ContributorsWiles, Christian Scott (Author) / Oswald, Jay (Thesis director) / Dai, Lenore (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2015-12
Description
The goal of this thesis project was to build an understanding of supersonic projectile dynamics through the creation of a trajectory model that incorporates several different aerodynamic concepts and builds a criteria for the stability of a projectile. This was done iteratively where the model was built from a foundation of kinematics with various aerodynamic principles being added incrementally. The primary aerodynamic principle that influenced the trajectory of the projectile was in the coefficient of drag. The drag coefficient was split into three primary components: the form drag, skin friction drag, and base pressure drag. These together made up the core of the model, additional complexity served to increase the accuracy of the model and generalize to different projectile profiles.
ContributorsBlair, Martin (Co-author) / Armenta, Francisco (Co-author) / Takahashi, Timothy (Thesis director) / Herrmann, Marcus (Committee member) / Mechanical and Aerospace Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
This paper discusses the design of experimental setup and procedures to characterize polymethyl methylate (PMMA) at its glass transition temperature by studying its strain fields, process zone, and crack speed under different loading conditions. These loading conditions are different steady-state temperatures and initial crack lengths. Steady-state temperature testing uses a temperature control loop. Crack speed / resistivity testing is set up using a voltage drop method. From initial steady-state temperature testing, it was confirmed that the behavior of a PMMA sample becomes more ductile at higher temperatures, and that it is plausible for a crack process zone to be measured using DIC as temperature increases. From finite element simulations, it was validated that the crack speed is not constant relative to an initial crack length.
ContributorsKwan, Brandon (Author) / Oswald, Jay (Thesis director) / Hoover, Christian (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
Solar panels need to be both cost effective and environmentally friendly to compete with traditional energy forms. Photovoltaic recycling has the potential to mitigate the harm of waste, which is often landfilled, while putting material back into the manufacturing process. Out of many, three methods show much promise: Full Recovery End-of-Life Photovoltaic (FRELP), mechanical, and sintering-based recycling. FRELP recycling has quickly gained prominence in Europe and promises to fully recover the components in a solar cell. The mechanical method has produced high yields of valuable materials using basic and inexpensive processes. The sintering method has the potential to tap into a large market for feldspar. Using a levelized cost of electricity (LCOE) analysis, the three methods could be compared on an economic basis. This showed that the mechanical method is least expensive, and the sintering method is the most expensive. Using this model, all recycling methods are less cost effective than the control analysis without recycling. Sensitivity analyses were then done on the effect of the discount rate, capacity factor, and lifespan on the LCOE. These results showed that the change in capacity factor had the most significant effect on the levelized cost of electricity. A final sensitivity analysis was done based on the decreased installation and balance of systems costs in 2025. With a 55% decrease in these costs, the LCOE decreased by close to $0.03/kWh for each method. Based on these results, the cost of each recycling method would be a more considerable proportion of the overall LCOE of the solar farm.
ContributorsMeister, William Frederick (Author) / Goodnick, Stephen (Thesis director) / Phelan, Patrick (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
The project consists of steps that a Formula SAE team could take into developing their first carbon fiber monocoque chassis. The project is based on an interview with a successful team that has build carbon monocoques for the last several years. The project covers the steps into designing a carbon monocoque, including aspects that need to be highlighted in the design process as well as an outline of the overall rules and regulations regarding carbon fiber monocoques. The project also encompasses simple finite element analysis procedure that would introduce teams into carbon fiber composite sandwich analysis and its applications in racecar monocoques. The project also includes steps in manufacturing a carbon fiber monocoque beginning from methods to acquire necessary materials to the final process of de-molding the monocoque. The method has been used before from several FSAE teams, proving its viability. The goal is that through this report, teams could have an idea of where to start in developing their carbon monocoques and have a clear path to take on going from initial designs up until a final finished product.
ContributorsEhrke, Lawrence Herman (Co-author) / Andiyastika, Gede P. (Co-author) / Patel, Jay (Thesis director) / Middleton, James (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
The operating principles of bicycle drivetrains have remained largely static since the invention of the derailleur in 1905. A bicycle-specific Continuously Variable Transmission has the potential to eliminate many of these issues. This paper explores the current state of bicycle CVT technology, details the advantages and disadvantages of these designs, and analyzes the many human factors that play into their adoption. Finally, a conceptual design for a novel bicycle CVT is described, and a physical model is created to demonstrate the mechanical principles of operation.
ContributorsBurgard, Kyle (Author) / Singh, Anoop (Thesis director) / Trimble, Steven (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
The goal of this project was to conduct a preliminary performance analysis of an early Next Generation Air Dominance (NGAD) design by Lockheed Martin. NGAD is a sixth-generation air superiority initiative for the United States Air Force (USAF), not to be confused with the United States Navy variant, looking to replace the F-22 Raptor due to rising tensions with China in the Pacific. A three-stream double-bypass adaptive cycle engine (ACE) model was developed in MATLAB to analyze thermodynamic states throughout the engine and generate performance data such as thrust and fuel requirements. The variable area bypass injectors (VABIs) of an ACE allow it to improve range and thrust while also reducing spillage drag when compared to a standard low-bypass turbofan for military aircraft. The aircraft was simulated at 15, 16, 17, and 18 km, and at a cruise Mach of 1.8, in accordance with expected NGAD requirements. Engine performance data was then used, alongside rough aerodynamic data based on the aircraft’s geometry, to determine the ideal wet weight, dry weight, and wing loading for an assumed air-superiority mission profile. Plots of wet weight, wing span, and wing area as functions wing loading were used to visualize the design space for a given mission.
ContributorsTokishi, Shane (Author) / Wells, Valana (Thesis director) / Dahm, Werner (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2024-05
Description
This thesis investigates auxetic structures' specific energy absorption properties, characterized by their negative Poisson's Ratio (NPR). Auxetics, derived from natural materials and engineered designs, are increasingly applied in automotive, aerospace, and defense industries due to their enhanced material properties like indentation resistance and fracture toughness.
The research commenced with a thorough literature review to gather relevant methodologies and insights into auxetic geometries. This was followed by analytical experiments and simulations focused on the re-entrant auxetic pattern, known for its simplicity and effectiveness. The study tested modifications to this pattern, aiming to enhance energy absorption by adjusting parameters like base thickness and adding filets.
Simulations were performed using ANSYS 2023 R2, modeling the materials under plane stress conditions to assess their mechanical responses. Two main variants were examined: the Enhanced Stiffness pattern, which alters thickness, and the Filet Re-entrant pattern, which incorporates fillets to reduce stress concentrations. Results indicated that both modifications improved energy absorption compared to the standard re-entrant design, with Filet patterns showing superior performance due to their efficient stress distribution.
This work extends the understanding of auxetic materials, demonstrating significant potential to improve safety and functionality in engineering applications through advanced material design.
ContributorsSastriawan, Yoga (Author) / Kang, Wonmo (Thesis director) / Safari, Hamid (Committee member) / Mahmoudi, Mohammadreza (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor) / Dean, W.P. Carey School of Business (Contributor)
Created2024-05
Description
The objective of this project is to determine whether a finite-element model can predict the threshold temperatures at which mechanical failure will occur in perovskite-silicon tandem modules. No such computational thermomechanical analysis has been performed on perovskite-silicon tandem modules. Previous literature has demonstrated the effectiveness of finite element methods in predicting cracking of perovskites under bending loads and for characterizing the thermomechanical behavior of solar photovoltaic devices. This work computationally synthesizes these two research areas to determine design criteria for mechanically robust next-generation tandem photovoltaic devices and modules.
ContributorsMachbitz, David (Author) / Rolston, Nicholas (Thesis director) / Ladani, Leila (Committee member) / Murthy, Raghavendra (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor) / Department of English (Contributor)
Created2024-05
Description
This thesis explores strategies to enhance visibility and engagement within local music ecosystems using a data-driven approach that leverages streaming platform data. It employs a two-pronged approach, consisting of a Proof of Concept (PoC) and a Business Model Canvas (BMC). The PoC involves the development and refinement of two novel machine learning-based music recommendation algorithms, specifically tailored for local stakeholders in the Valley Metro area. Empirical testing of these algorithms has shown a significant potential increase in visibility and engagement for local music events. Utilizing these results, the study proposes informed revisions to the existing streaming BMC, aiming to better support local music ecosystems through strategic enhancements derived from the validated PoC findings.
ContributorsEllini, Andre (Author) / Clarkin, Michael (Co-author) / Bradley, Robert (Co-author) / Mancenido, Michelle (Thesis director) / Sirugudi, Kumar (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2024-05