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Articles 1 - 10 of 10
Full-Text Articles in Mechanical Engineering
A Decoupled Engineering Methodology For Accurate Prediction Of Ablative Surface Boundary Conditions In Thermal Protection Systems, Justin Cooper
A Decoupled Engineering Methodology For Accurate Prediction Of Ablative Surface Boundary Conditions In Thermal Protection Systems, Justin Cooper
Theses and Dissertations--Mechanical Engineering
The main objective of the present work is to demonstrate a method for prediction of aerothermal environments in the engineering design of hypersonic vehicles as an alternative to the current heritage method. Flat plate and stagnation point boundary layer theory require multiple assumptions to establish the current engineering paradigm. Chief among these assumptions is the similarity between mass and heat transfer. Origins of these assumptions are demonstrated and their relationship to conservative engineering design is analyzed, as well as conditions where they possibly break down. An alternative approach for assessing aerothermal environments from the fluid domain is presented, which permits …
Modeling Thin Layers In Material Response Solvers, Christen Setters
Modeling Thin Layers In Material Response Solvers, Christen Setters
Theses and Dissertations--Mechanical Engineering
Thermal Protection Systems (TPS) are a necessary component for atmospheric entry. Most TPS contain thin layers of various materials such as ceramic coatings, pore sealers and bonding agents. When modeling TPS, these thin layers are often neglected due to the difference in scale between the TPS (centimeters) and the thin layers (micrometers). In this study, a volume-averaging flux-conservation method is implemented in the governing equations of a finite volume material response code. The model proposes the addition of a volume and area fraction coefficient which utilizes a weighted-averaging between the amount of thin layer and heat shield material in a …
Laser Micropatterning Effects On Corrosion Resistance Of Pure Magnesium Surfaces, Yahya Efe Yayoglu
Laser Micropatterning Effects On Corrosion Resistance Of Pure Magnesium Surfaces, Yahya Efe Yayoglu
USF Tampa Graduate Theses and Dissertations
Magnesium and its alloys are good candidates to manufacture medical implants. They have excellent biocompatibility and because they biodegrade secondary surgical operation to remove the implant could be eliminated. However, in aqueous environments, magnesium alloys rapidly corrode, resulting in premature degradation of the implant along with biologically intolerable hydrogen gas generation. In literature, there are multiple studies focused on creating water repelling hydrophobic magnesium surfaces in order to decrease corrosion rates. Hydrophobic properties can be achieved by creation of a roughness profile on an initially smooth surface combined with a treatment that reduces the free surface energy. In theory, hydrophobic …
Development Of Universal Solver For High Enthalpy Flows Through Ablative Materials, Umran Duzel
Development Of Universal Solver For High Enthalpy Flows Through Ablative Materials, Umran Duzel
Theses and Dissertations--Mechanical Engineering
Atmospheric entry occurs at very high speeds which produces high temperature around the vehicle. Entry vehicles are thus equipped with Thermal Protection Systems which are usually made of ablative materials. This dissertation presents a new solver that models the atmospheric entry environment and the thermal protection systems. In this approach, both the external flow and the porous heat shield are solved using the same computational domain. The new solver uses the Volume Averaged Navier-Stokes Equations adapted for hypersonic non-equilibrium flow, and is thus valid for both domains. The code is verified using analytical problems, set of benchmarks and also a …
Modeling Of Complex Parts For Industrial Waterjet Cleaning, Braden James
Modeling Of Complex Parts For Industrial Waterjet Cleaning, Braden James
Graduate Theses and Dissertations
Industrial high-pressure waterjet cleaning is common to many industries. The modeling in this paper functions inside a collaborative robotic framework for high mix, low volume processes where human robot collaboration is beneficial. Automation of pressure washing is desirable for economic and ergonomic reasons. An automated cleaning system needs path simulation and analysis to give the operator insight into the predicted cleaning performance of the system. In this paper, ablation, the removal of a substrate coating by waterjet, is modeled for robotic cleaning operations. The model is designed to work with complex parts often found in spray cleaning operations, namely parts …
Steady State Simulation Of Pyrolysis Gases In An Inductively Coupled Plasma Facility, Nicholas C. Martin
Steady State Simulation Of Pyrolysis Gases In An Inductively Coupled Plasma Facility, Nicholas C. Martin
Graduate College Dissertations and Theses
An important step in the more efficient use of PICA (Phenolic Impregnated Carbon Ablator) as a Thermal Protection System (TPS) material for spacecraft is the understanding of its pyrolysis mechanics. The gases released during pyrolysis and their subsequent interaction with the reactive plasma environment is not yet well understood. The surface recession of PICA as it ablates during testing only makes the study and characterization of the chemical reactions more difficult. To this end, a probe has been designed for this study to simulate, in steady state, the pyrolysis gases within the UVM 30kW Inductively Coupled Plasma (ICP) Torch Facility. …
Investigation Of Pyrolysis Gas Chemistry In An Inductively Coupled Plasma Facility, Corey Tillson
Investigation Of Pyrolysis Gas Chemistry In An Inductively Coupled Plasma Facility, Corey Tillson
Graduate College Dissertations and Theses
The pyrolysis mechanics of Phenolic Impregnated Carbon Ablators (PICA) makes it a valued material for use in thermal protection systems for spacecraft atmospheric re-entry. The present study of the interaction of pyrolysis gases and char with plasma gases in the boundary layer over PICA and its substrate, FiberForm, extends previous work on this topic that has been done in the UVM 30 kW Inductively Coupled Plasma (ICP) Torch Facility. Exposure of these material samples separately to argon, nitrogen, oxygen, air, and carbon dioxide plasmas, and combinations of said test gases provides insight into the evolution of the pyrolysis gases as …
Modeling Of Spallation Phenomenon In An Arc-Jet Environment, Raghava Sai Chaitanya Davuluri
Modeling Of Spallation Phenomenon In An Arc-Jet Environment, Raghava Sai Chaitanya Davuluri
Theses and Dissertations--Mechanical Engineering
Space vehicles, while entering the planetary atmosphere, experience high loads of heat. Ablative materials are commonly used for a thermal protection system, which undergo mass removal mechanisms to counter the heat rates. Spallation is one of the ablative processes, which is characterized by the ejection of solid particles from the material into the flow. Numerical codes that are used in designing the heat shields ignore this phenomenon. Hence, to evaluate the effectiveness of spallation phenomenon, a numerical model is developed to compute the dynamics and chemistry of the particles. The code is one-way coupled to a CFD code that models …
Approximate Thermal Modeling Of Radiofrequency Cardiac Ablation, Aaron Joseph Walter
Approximate Thermal Modeling Of Radiofrequency Cardiac Ablation, Aaron Joseph Walter
Theses and Dissertations
The ultimate objective of the research which led to this thesis is to increase the efficacy and safety of radiofrequency catheter ablation (RFCA) of cardiac tissue. The purpose of RFCA is to carefully heat selected locations in the heart. The resulting thermal injury creates lesions which prevent the generation or propagation of arrhythmias. The ability to predict the appropriate amount of energy required at any ablation site is essential to increasing the efficacy and safety of RFCA. The research documented in this thesis focuses on the development of an approximate thermal model of the time-dependent temperature profile within the myocardium …
A Study Of Radiofrequency Cardiac Ablation Using Analytical And Numerical Techniques, Ryan Todd Roper
A Study Of Radiofrequency Cardiac Ablation Using Analytical And Numerical Techniques, Ryan Todd Roper
Theses and Dissertations
Studies on radiofrequency (RF) ablation are often aimed at accurately predicting tissue temperature distributions by numerical solution of the bioheat equation. This thesis describes the development of an analytical solution to serve as a benchmark for subsequent numerical solutions. The solution, which was obtained using integral transforms, has the form of a surface integral nested within another surface integral. An integration routine capable of evaluating such integrals was developed and a C program was written to implement this routine. The surface integration routine was validated using a surface integral with a known analytical solution. The routine was, then, used to …