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An Evaluation Of Ultrasonic Shot Peening And Abrasive Flow Machining As Surface Finishing Processes For Selective Laser Melted 316l, Rhys Gilmore 2018 California Polytechnic State University, San Luis Obispo

An Evaluation Of Ultrasonic Shot Peening And Abrasive Flow Machining As Surface Finishing Processes For Selective Laser Melted 316l, Rhys Gilmore

Master's Theses and Project Reports

Additive Manufacturing, and specifically powder bed fusion processes, have advanced rapidly in recent years. Selective Laser Melting in particular has been adopted in a variety of industries from biomedical to aerospace because of its capability to produce complex components with numerous alloys, including stainless steels, nickel superalloys, and titanium alloys. Post-processing is required to treat or solve metallurgical issues such as porosity, residual stresses, and surface roughness. Because of the geometric complexity of SLM produced parts, the reduction of surface roughness with conventional processing has proven especially challenging. In this Thesis, two processes, abrasive flow machining and ultrasonic shot peening ...


Thermally Stable Super-Hydrophobic Surface Creation, Caleb Turner 2018 Portland State University

Thermally Stable Super-Hydrophobic Surface Creation, Caleb Turner

Undergraduate Research & Mentoring Program

Thermally stable super-hydrophobic surface coatings are critical to applications in low gravity fluid dynamics, and in particular Leidenfrost effects. The challenges of manufacturing different super-hydrophobic coatings that are thermally stable, semi-transparent, and environmentally safe at desired operating temperatures is pursued in order to explore the applications of such coatings aboard spacecraft. A catalog of surface coating manufacturing procedures is tabulated with measures for static contact angle, thermal stability, and transparency. These quantities and methods serve as a foundation for both technology applications and follow on experimentation concerning low gravity fluid mechanics at the Portland State Dryden Drop Tower lab.


Fracture Initiation In A Transversely Isotropic Solid: Transient Three Dimensional Analysis, Louis Milton Brock 2018 University of Kentucky

Fracture Initiation In A Transversely Isotropic Solid: Transient Three Dimensional Analysis, Louis Milton Brock

Mechanical Engineering Faculty Publications

A transversely isotropic solid is at rest, and contains a semi-infinite, plane crack. The axis of rotational material symmetry lies in the crack plane. Application of normal point forces to each face of the crack causes transient 3D growth. The related problem of discontinuities in displacement and traction that exist on regions that exhibit dynamic similarity is first considered. Analytic results are obtained in integral transform space. These lead to equations of the Wiener–Hopf type for the fracture problem. Analytic solutions are again obtained and, upon inversion, subjected to a dynamic energy release rate criterion that includes kinetic energy ...


Phase Field Study Of Surface-Induced Melting And Solidification From A Nanovoid: Effect Of Dimensionless Width Of Void Surface And Void Size, Anup Basak, Valery I. Levitas 2018 Iowa State University

Phase Field Study Of Surface-Induced Melting And Solidification From A Nanovoid: Effect Of Dimensionless Width Of Void Surface And Void Size, Anup Basak, Valery I. Levitas

Physics and Astronomy Publications

The size effect and the effects of a finite-width surface on barrierless transformations between the solid (S), surface melt (SM), and melt (M) from a spherical nanovoid are studied using a phase field approach. Melting (SM → M and S → M) from the nanovoid occurs at temperatures which are significantly greater than the solid-melt equilibrium temperature θe but well below the critical temperature for solid instability. The relationships between the SM and M temperatures and the ratio of the void surface width and width of the solid-melt interface, Δ⎯⎯⎯, are found for the nanovoids of different sizes. Below a critical ratio ...


A Novel Magnetorheological Fluid Damper For A Small Spacecraft With Flexible Appendages, Robert Waelchli 2018 Embry-Riddle Aeronautical University

A Novel Magnetorheological Fluid Damper For A Small Spacecraft With Flexible Appendages, Robert Waelchli

Dissertations and Theses

Small satellites have become increasingly popular over the past thirty years, particularly since the adoption of the common CubeSat architecture early this century. Because of their restricted volume and electrical budgets however, there are practical limits to the missions that small satellites may adopt. One potential near-term solution to the problem of limited electrical power may be the adoption of larger, flexible solar arrays. However, spacecraft with flexible appendages have historically presented attitude control challenges relating to platform stability given the dynamic response of the flexible components to applied torques. These challenges may be particularly disruptive to a small spacecraft ...


Ultrasonic Nondestructive Evaluation Of Metal Additive Manufacturing., Venkata Karthik Nadimpalli 2018 University of Louisville

Ultrasonic Nondestructive Evaluation Of Metal Additive Manufacturing., Venkata Karthik Nadimpalli

Electronic Theses and Dissertations

Metal Additive Manufacturing (AM) is increasingly being used to make functional components. One of the barriers for AM components to become mainstream is the difficulty to certify them. AM components can have widely different properties based on process parameters. Improving an AM processes requires an understanding of process-structure-property correlations, which can be gathered in-situ and post-process through nondestructive and destructive methods. In this study, two metal AM processes were studied, the first is Ultrasonic Additive Manufacturing (UAM) and the second is Laser Powder Bed Fusion (L-PBF). The typical problems with UAM components are inter-layer and inter-track defects. To improve the ...


Model-Assisted Probability Of Detection Of Flaws In Aluminum Blocks Using Polynomial Chaos Expansions, Xiaosong Du, Leifur Leifsson, Robert J. Grandin, William Q. Meeker, Ronald A. Roberts, Jiming Song 2018 Iowa State University

Model-Assisted Probability Of Detection Of Flaws In Aluminum Blocks Using Polynomial Chaos Expansions, Xiaosong Du, Leifur Leifsson, Robert J. Grandin, William Q. Meeker, Ronald A. Roberts, Jiming Song

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

Probability of detection (POD) is widely used for measuring reliability of nondestructive testing (NDT) systems. Typically, POD is determined experimentally, while it can be enhanced by utilizing physics-based computational models in combination withmodel-assisted POD (MAPOD) methods. With the development of advanced physics-basedmethods, such as ultrasonic NDTtesting, the empirical information,needed for POD methods, can bereduced. However, performing accurate numerical simulationscan be prohibitivelytime-consuming, especially as part of stochastic analysis. In this work, stochastic surrogate models for computational physics-based measurement simulations are developed for cost savings of MAPOD methods while simultaneously ensuring sufficient accuracy. The stochastic surrogate is used to propagate the ...


Evaluation Of The Fidelity Of Feature Descriptor-Based Specimen Tracking For Automatic Nde Data Integration, Rafael Radkowski, Stephen D. Holland, Robert J. Grandin 2018 Iowa State University

Evaluation Of The Fidelity Of Feature Descriptor-Based Specimen Tracking For Automatic Nde Data Integration, Rafael Radkowski, Stephen D. Holland, Robert J. Grandin

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

This research addresses inspection location tracking in the field of nondestructive evaluation (NDE) using a computer vision technique to determine the position and orientation of typical NDE equipment in a test setup. The objective is the tracking accuracy for typical NDE equipment to facilitate automatic NDE data integration. Since the employed tracking technique relies on surface curvatures of an object of interest, the accuracy can be only experimentally determined. We work with flash-thermography and conducted an experiment in which we tracked a specimen and a thermography flash hood, measured the spatial relation between both, and used the relation as input ...


Numerical Simulation Of A High Strain Rate Biaxial Compression Apparatus, Michael Lagieski 2018 Washington University in St. Louis

Numerical Simulation Of A High Strain Rate Biaxial Compression Apparatus, Michael Lagieski

Engineering and Applied Science Theses & Dissertations

Few experimental methods today are capable of exploring the strength of materials at high strain rates (105 s-1). Those that are capable, such as the Split Hopkinson Bar, Taylor Anvil and Plate Impact suffer from instability and are generally limited to one dimensional wave propagation. Of particular interest is material response under biaxial compression, similar to that seen in inertial confinement fusion. Laser fusion fuel pellets typically undergo large strain rates as well as plastic deformation and non-linear behavior. This work briefly outlines an experimental procedure designed to replicate these large strain rates under biaxial compression using spherical ...


Nanoscale Multiphase Phase Field Approach For Stress- And Temperature-Induced Martensitic Phase Transformations With Interfacial Stresses At Finite Strains, Anup Basak, Valery I. Levitas 2018 Iowa State University

Nanoscale Multiphase Phase Field Approach For Stress- And Temperature-Induced Martensitic Phase Transformations With Interfacial Stresses At Finite Strains, Anup Basak, Valery I. Levitas

Aerospace Engineering Publications

A thermodynamically consistent, novel multiphase phase field approach for stress- and temperature-induced martensitic phase transformations at finite strains and with interfacial stresses has been developed. The model considers a single order parameter to describe the austenite↔martensitic transformations, and another N order parameters describing N variants and constrained to a plane in an N-dimensional order parameter space. In the free energy model coexistence of three or more phases at a single material point (multiphase junction), and deviation of each variant-variant transformation path from a straight line have been penalized. Some shortcomings of the existing models are resolved. Three different kinematic ...


Durability Assessment Of Soft Elastomeric Capacitor Skin For Shm Of Wind Turbine Blades, Austin Downey, Anna Laura Pisello, Elena Fortunati, Claudia Fabiani, Francesca Luzi, Luigi Torre, Filippo Ubertini, Simon Laflamme 2018 Iowa State University

Durability Assessment Of Soft Elastomeric Capacitor Skin For Shm Of Wind Turbine Blades, Austin Downey, Anna Laura Pisello, Elena Fortunati, Claudia Fabiani, Francesca Luzi, Luigi Torre, Filippo Ubertini, Simon Laflamme

Civil, Construction and Environmental Engineering Conference Presentations and Proceedings

Renewable energy production has become a key research driver during the last decade. Wind energy represents a ready technology for large-scale implementation in locations all around the world. While important research is conducted to optimize wind energy production efficiency, a critical issue consists of monitoring the structural integrity and functionality of these large structures during their operational life cycle. This paper investigates the durability of a soft elastomeric capacitor strain sensing membrane, designed for structural health monitoring of wind turbines, when exposed to aggressive environmental conditions. The sensor is a capacitor made of three thin layers of an SEBS polymer ...


Manufacturing Process Simulation – On Its Way To Industrial Application, Dennis Otten, Tobias A. Weber, Jan-Christoph Arent 2018 University of Applied Sciences Augsburg

Manufacturing Process Simulation – On Its Way To Industrial Application, Dennis Otten, Tobias A. Weber, Jan-Christoph Arent

International Journal of Aviation, Aeronautics, and Aerospace

Manufacturing process simulation (MPS) has become more and more important for aviation and the automobile industry. A highly competitive market requires the use of high performance metals and composite materials in combination with reduced manufacturing cost and time as well as a minimization of the time to market for a new product. However, the use of such materials is expensive and requires sophisticated manufacturing processes. An experience based process and tooling design followed by a lengthy trial-and-error optimization is just not contemporary anymore. Instead, a tooling design process aided by simulation is used more often. This paper provides an overview ...


Effects Of Manufacturing Process Variables On Ultrasonic Testing In Electron Beam Melted Ti-6al-4v, Andrew D. Durkee 2018 Air Force Institute of Technology

Effects Of Manufacturing Process Variables On Ultrasonic Testing In Electron Beam Melted Ti-6al-4v, Andrew D. Durkee

Theses and Dissertations

Further research on validating additive manufacturing production quality is required before the realization of direct print-to-fly application of critical components. This research examines the response of ultrasonic testing as a function of various manufacturing variables in electron beam melted samples of Ti-6Al-4V. Four dimensionally identical blocks with 6 spherical voids at varying depths were manufactured using different combinations of stock powder, edge treatments, and void melting. Scans were completed on two sides of each specimen with the transducer focused on the mid-plane. Additionally, one specimen was scanned 6 times, with the focal plane adjusted for each scan to match the ...


Creep Of Hafnium Diboride -20 Vol% Silicon Carbide At 1500°C In Air, Glen E. Pry 2018 Air Force Institute of Technology

Creep Of Hafnium Diboride -20 Vol% Silicon Carbide At 1500°C In Air, Glen E. Pry

Theses and Dissertations

Refractory metal borides, commonly referred to as Ultra High Temperature Ceramics (UHTCs), exhibit a number of unique properties, such as extremely high melting temperature and hardness, chemical stability, high electrical and thermal conductivity and corrosion resistance. It has been demonstrated that the addition of SiC improves the oxidation resistance of ZrB2- and HfB2-based UHTCs above 1200°C by modifying the composition of the oxide scale. Addition of SiC retards the oxidation rate of ZrB2 and HfB2 by forming a protective layer of borosilicate glass. Creep deformation is one of the critical criterion for structural application of ceramics at elevated temperatures ...


Land Cover Influences On Airborne Noise Propagation At Usaf Installations, Ariel L. Waiters 2018 Air Force Institute of Technology

Land Cover Influences On Airborne Noise Propagation At Usaf Installations, Ariel L. Waiters

Theses and Dissertations

Mitigation of aircraft noise and encroachment by residential areas at various U.S. military installations remains a challenge and hampers effective military operations. The Air Force has established standard practices that utilize computational noisemodels to generate and display noise propagation from military installations. Despite great advances in models and mitigation action plans, the current USAF Noisemap modeling tool and methods do not consider the effects of variation in land cover. Moreover, such limitations could greatly affect the accuracy of predicting aircraft noise pollution. The standard modeling method assumes a ground cover impedance of 225 Kpa*s / m2, which generalizes the ...


A Study Of The Hexakis Icosahedron Vacuum Lighter Than Air Vehicle And The Effects Of Air Evacuation On The Structural Integrity, Anthony A. Castello 2018 Air Force Institute of Technology

A Study Of The Hexakis Icosahedron Vacuum Lighter Than Air Vehicle And The Effects Of Air Evacuation On The Structural Integrity, Anthony A. Castello

Theses and Dissertations

The research this paper focuses on is comparing the structural differences between the icosahedron and hexakis icosahedron frame and skin for use as a vacuum lighter than air vehicle (VLTAV), analyzing the stress concentrations in the hexakis icosahedron both with and without the skin, and finding the optimal location and size of the air evacuation method for creating the internal vacuum. Previous research to date has identified dynamic loading on the structure and optimization of the structure, but this will be the first research to analyze the manufacturing of the structure through the development of the air evacuation design. Findings ...


Study Of Abnormal Grain Growth In Beta Annealed Ti-6al-4v Forgings, Lee R. Morris 2018 Air Force Institute of Technology

Study Of Abnormal Grain Growth In Beta Annealed Ti-6al-4v Forgings, Lee R. Morris

Theses and Dissertations

Beta annealed Ti-6Al-4V has been used extensively in current aerospace platforms due to properties such as high strength to weight ratio. Recent inspections during aircraft production have revealed regions of excessive grain sizes, resulting in quarantined parts and excessive time spent on root cause analysis and risk mitigation efforts. Uncertainty surrounding these parts has led to increased costs and may cause future aircraft production delays. Part manufacturers have intermittently reported problems with abnormal grain growth in these alloys for years, but to date no supplier has been able to determine the source of this microstructural phenomenon. Leveraging common Finite Element ...


Aerial Port Of The Future: Developing Paperless Operations, Peter J. Williams 2018 Air Force Institute of Technology

Aerial Port Of The Future: Developing Paperless Operations, Peter J. Williams

Theses and Dissertations

Air Mobility Command (AMC) is combatting manning mismatches with antiquated processes and equipment in Aerial Port operations, and has chosen to address these issues through an initiative called “Aerial Port of the Future.” This initiative is designed to understand challenges in Aerial Ports and implement technological tools, where appropriate, to aid AMC Airmen in their duties of transporting goods and personnel through military channels. Oftentimes, personnel are forced to utilize technology that may not meet their needs, and in turn may resist implementation of the imposed technology. Therefore, first, this research identifies potential technologies designed to improve Aerial Port efficiency ...


Nanoindentation Study Of Corrosion-Induced Grain Boundary Degradation In A Pipeline Steel, Denizhan Yavas, Pratyush Mishra, Abdullah Alshehri, Pranav Shrotriya, Kurt R. Hebert, Ashraf F. Bastawros 2018 Iowa State University

Nanoindentation Study Of Corrosion-Induced Grain Boundary Degradation In A Pipeline Steel, Denizhan Yavas, Pratyush Mishra, Abdullah Alshehri, Pranav Shrotriya, Kurt R. Hebert, Ashraf F. Bastawros

Aerospace Engineering Publications

High-strength low-alloy steels used for oil and gas pipelines are vulnerable to intergranular stress corrosion cracking in moderately alkaline soils. The mechanism of corrosion-induced embrittlement under such conditions is not yet understood. Nanoindentation was used to detect localized degradation of mechanical properties near internal grain boundaries of X-70 steel undergoing intergranular corrosion at active dissolution potentials at pH 8.2. The measurements identified a one-micron thick mechanically-degraded layer with 25% reduced hardness near corroded grain boundaries. It is suggested that the corrosion process may introduce an active softening agent, possibly non-equilibrium lattice vacancies generated by oxidation.


Model-Assisted Approach For Probability Of Detection (Pod) In High-Temperature Ultrasonic Nde Using Low-Temperature Signals, Prathamesh N. Bilgunde, Leonard J. Bond 2018 Iowa State University

Model-Assisted Approach For Probability Of Detection (Pod) In High-Temperature Ultrasonic Nde Using Low-Temperature Signals, Prathamesh N. Bilgunde, Leonard J. Bond

Aerospace Engineering Publications

Advanced piezoelectric-based ultrasonic transducers offer the potential for in-coolant nondestructive testing (NDT) measurements at high temperatures (HTs), including during hot standby (~260°C) for liquid-sodium–cooled advanced small modular reactors. The reliability of the NDT measurements is typically quantified by the probability of detection (POD) measured at the corresponding temperature. Obtaining such data in liquid sodium is challenging. Using a model-assisted POD approach, a transfer function is reported that enables data obtained on low carbon steel specimens at room temperature to give an estimated POD at an HT. A primary source of the difference in POD between room temperature and ...


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