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Model-Based Inversion For Flash Thermography, Stephen D. Holland, Brian Schiefelbein 2017 Iowa State University

Model-Based Inversion For Flash Thermography, Stephen D. Holland, Brian Schiefelbein

Stephen D. Holland

The thermal image sequences from thermography experiments are blurred by lateral diffusion and therefore hard to interpret. The widely used one-dimensional heat flow model provides a robust interpretation of thickness or delamination from “break time” where lateral diffusion is significant, but is less effective otherwise. As a result, it remains quite common to interpret defects by contrast from the surrounding “acreage” rather than by the intrinsic properties of the defect signal itself.

In this paper, we present an approach for model-based inversion of flash thermography image sequences that attempts to approximately reconstruct the flow or back-surface geometry from the thermal ...


Adhesion Hysteresis And Its Role In Vibrothermography Crack Heating, Bryan E. Schiefelbein, Tyler Lesthaeghe, Ashraf F. Bastawros, Stephen D. Holland 2017 Iowa State University

Adhesion Hysteresis And Its Role In Vibrothermography Crack Heating, Bryan E. Schiefelbein, Tyler Lesthaeghe, Ashraf F. Bastawros, Stephen D. Holland

Stephen D. Holland

Vibrothermography is an NDE inspection which uses vibration to stimulate surface cracks and measure the resultant heat generation. For years, the accepted assumption has been that heat generation in Vibrothermography NDE is due to friction between opposing crack surfaces [1–3]. A frictional mechanism suggests that crack surfaces in sliding shear would generate heat, whereas crack surfaces coming into and out of contact in an opening-closing mode would not, or would generate much less. But cracks heat easily in opening/closing mode and experimental evidence [4] is not consistent with the prediction that heat generation for shear vibration should be ...


Simple Tester For Measuring Lateral Thermal Diffusivities In Composites, Stephen D. Holland, Elizabeth Gregory, Daniel Romero 2017 Iowa State University

Simple Tester For Measuring Lateral Thermal Diffusivities In Composites, Stephen D. Holland, Elizabeth Gregory, Daniel Romero

Stephen D. Holland

Model-based analysis and inversion of thermography data relies on knowledge of thermal diffusivities. Through-thickness diffusivity is readily measured using the flash method [1]. In composite materials, lateral diffusivities may be drastically different from the through-thickness values, but there is no comparable simple and standard approach for measuring those lateral thermal diffusivities. Welch, Heath, and Winfree [2] proposed a technique based on laser line pulse excitation, but that approach requires a reasonably powerful laser and thermal camera with the concomitant costs and safety requirements. In this presentation, we show a simple and low cost (but not entirely nondestructive) system and method ...


Inspection And Model Based Inversion Of Highly Curved Composite Surfaces With Flash Thermography, Bryan E. Schiefelbein, Stephen D. Holland 2017 Iowa State University

Inspection And Model Based Inversion Of Highly Curved Composite Surfaces With Flash Thermography, Bryan E. Schiefelbein, Stephen D. Holland

Stephen D. Holland

With the development of advanced aircraft structures and stringent mechanical requirements, robust and reliable inspection methods are needed to ensure safe operation and maximum utilization of the equipment [1]. Aircraft composite parts can exhibit complex geometries and tight curvature, such as leading edges and chines. These curved structures are difficult to inspect for defects, especially where the local curvature is high [2–4]. Pulsed thermography has the potential for rapid inspection of large areas, making it attractive for depot or field inspection of large aircraft parts. When imaging areas of high curvature, there are a number of confounding factors, including ...


Turbulent Combustion Of Polydisperse Evaporating Sprays With Droplet Crossing: Eulerian Modeling And Validation In The Infinite Knudsen Limit, S. de Chaisemartin, L. Freret, D. Kah, F. Laurent, Rodney O. Fox, J. Reveillon, M. Massot 2017 Ecole Centrale Paris

Turbulent Combustion Of Polydisperse Evaporating Sprays With Droplet Crossing: Eulerian Modeling And Validation In The Infinite Knudsen Limit, S. De Chaisemartin, L. Freret, D. Kah, F. Laurent, Rodney O. Fox, J. Reveillon, M. Massot

Rodney O. Fox

The accurate simulation of the dynamics of polydisperse evaporating sprays in unsteady gaseous flows with large-scale vortical structures is both a crucial issue for industrial applications and a challenge for modeling and scientific computing. The difficulties encountered by the usual Lagrangian approaches make the use of Eulerian models attractive, aiming at a lower cost and an easier coupling with the carrier gaseous phase. Among these models, the multi-fluid model allows for a detailed description of the polydispersity and size-velocity correlations for droplets of various sizes. The purpose of the present study is twofold. First, we extend the multi-fluid model in ...


Conditional-Moment Closure With Differential Diffusion For Soot Evolution In Fire, J. C. Hewson, A. J. Ricks, S. R. Tieszen, A R. Kerstein, Rodney O. Fox 2017 Sandia National Laboratories

Conditional-Moment Closure With Differential Diffusion For Soot Evolution In Fire, J. C. Hewson, A. J. Ricks, S. R. Tieszen, A R. Kerstein, Rodney O. Fox

Rodney O. Fox

The conditional-moment closure (CMC) equation for the evolution of a large Lewis number scalar, soot, is derived starting from the joint probability density function (pdf) equation for the gas-phase mixture fraction, ξ g , and the soot mass fraction, Y s . Unlike previous approaches starting with the joint pdf, the residual terms that result from the typical closure models were retained. A new formulation of the one-dimensional turbulence (ODT) model suitable for spatially evolving flows with buoyant acceleration and radiative transport in participating media was employed to carry out simulations of a prototypical ethene fire. The resulting ODT evolution of ξ ...


Improved Method Of Co2 Laser Cutting Of Aluminum Nitride, Raathai Molian, Pranav Shrotriya, Pal Molian 2017 Iowa State University

Improved Method Of Co2 Laser Cutting Of Aluminum Nitride, Raathai Molian, Pranav Shrotriya, Pal Molian

Pranav Shrotriya

The traditional “evaporation∕melt and blow” mechanism of CO2 laser cutting of aluminum nitride (AlN) chip carriers and heat sinks suffers from energy losses due to its high thermal conductivity, formation of dross, decomposition to aluminum, and uncontrolled thermal cracking. In order to overcome these limitations, a thermochemical method that uses a defocused laser beam to melt a thin layer of AlN surface in oxygen environment was utilized. Subsequent solidification of the melt layer generated shrinkage and thermal gradient stresses that, in turn, created a crack along the middle path of laser beam and caused material separation through unstable crack ...


Applications Of Femtosecond Laser Processed Metallic Surfaces: Leidenfrost Point And Thermal Stability Of Rare Earth Oxide Coatings, Anton Charles Hassebrook 2017 University of Nebraska-Lincoln

Applications Of Femtosecond Laser Processed Metallic Surfaces: Leidenfrost Point And Thermal Stability Of Rare Earth Oxide Coatings, Anton Charles Hassebrook

Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research

In this thesis, micro/nano structured surfaces were created through the use of Femtosecond Laser Surface Processing (FLSP). In the first part of the thesis, an experimental investigation of the effects of droplet diameters and fluid properties on the Leidenfrost temperature of polished and nano/microstructured surfaces has been carried out. Leidenfrost experiments were conducted on a stainless steel 304 polished surface and a stainless steel surface which was processed by a femtosecond laser to form Above Surface Growth (ASG) nano/microstructures. Surface preparation resulted in a root mean square roughness (Rrms) of 4.8 µm and 0.04 ...


Computer Simulation Of Pore Migration Due To Temperature Gradients In Nuclear Oxide Fuel, Ian Wayne Vance 2017 University of Arkansas, Fayetteville

Computer Simulation Of Pore Migration Due To Temperature Gradients In Nuclear Oxide Fuel, Ian Wayne Vance

Theses and Dissertations

A phase-field simulation model is being presented that captures the thermal-gradient-driven migration of pores in oxide fuel associated with fuel restructuring. The model utilizes a Cahn-Hilliard equation supplemented with an advection term to describe the vapor transport of fuel material through the pore interior due to gradients in vapor pressure. In addition, the model also captures changes in a migrating pores’ morphology. Simulations demonstrate that the model successfully predicts pore migration towards the hottest portion of the fuel, the centerline. The simulations also demonstrate changes in pore shape that are in agreement with previous experimental observations. Initially isotropic pores are ...


Characterization Of Plastic Deformation Evolution In Single Crystal And Nanocrystalline Cu During Shock By Atomistic Simulations, Mehrdad Mirzaei Sichani 2017 University of Arkansas, Fayetteville

Characterization Of Plastic Deformation Evolution In Single Crystal And Nanocrystalline Cu During Shock By Atomistic Simulations, Mehrdad Mirzaei Sichani

Theses and Dissertations

The objective of this dissertation is to characterize the evolution of plastic deformation mechanisms in single crystal and nanocrystalline Cu models during shock by atomistic simulations. Molecular dynamics (MD) simulations are performed for a range of particle velocities from 0.5 to 1.7 km/s and initial temperatures of 5, 300 and 600 K for single crystal models as well as particle velocities from 1.5 to 3.4 km/s for nanocrystalline models with grain diameters of 6, 11, 16 and 26 nm. For single crystal models, four different shock directions are selected, <100>, <110>, <111> and <321>, and dislocation density behind ...


Modeling And Computation Of The Maximum Braking Energy Speed For Transport Category Airplanes, Nihad E. Daidzic 2017 AAR Aerospace Consulting, LLC

Modeling And Computation Of The Maximum Braking Energy Speed For Transport Category Airplanes, Nihad E. Daidzic

Journal of Aviation Technology and Engineering

Transport-category or FAR/CS 25 certified airplanes may occasionally become braking energy capacity limited. Such limitation may exist when heavy airplanes are departing airports at high-density altitudes, on relatively long runways, and/or possibly with some tailwind component. A maximum braking energy VMBE speed exists which may limit the maximum allowable takeoff decision/action speed V1. The ever-existing possibility of high-speed rejected takeoff in such conditions may also limit the airplane gross weight for declared available distances. To gain deeper insights and acquire better understanding of the topic, a theoretical model of the maximum braking energy and the related VMBE ...


In-House Fabrication Of Temperature Sensitive Paint For Turbine Cooling Research, Mayur D. Patel, Mark A. Ricklick 2017 Embry-Riddle Aeronautical University

In-House Fabrication Of Temperature Sensitive Paint For Turbine Cooling Research, Mayur D. Patel, Mark A. Ricklick

Beyond: Undergraduate Research Journal

The Temperature Sensitive Paint (TSP) is a widely used method in measuring and visualizing flow separation and heat transfer. Compared to the cost and time consumption needed for methods such as pitot tubes, temperature sensitive paint is a cheaper alternative. Due to high usage in College of Engineering research projects, it was determined that in house fabrication of temperature sensitive paint would reduce time and cost limitations. For initial stages, literature research was performed to determine the recipe of intensity based TSP with luminophore and polymer binder that operated optimum at temperatures from 0-100°C. Europium III thenoyltrifluoroacetonate was determined ...


Convection In Corrugated Slots, Seyed Arman Abtahi 2017 The University of Western Ontario

Convection In Corrugated Slots, Seyed Arman Abtahi

Electronic Thesis and Dissertation Repository

This thesis consists of two parts. The first part deals with the development of proper methodology, i.e. a spectrally accurate algorithm suitable for analysis of convection problems in corrugated slots. The second part is devoted to the study of natural convection in corrugated slots.

The algorithm uses the immersed boundary conditions (IBC) concept to deal with the irregular form of the solution domain associated with the presence of corrugated plates. The field equations are discretized on a regular domain surrounding the flow domain using Fourier expansions in the horizontal direction and Chebyshev expansions in the vertical direction. The boundary ...


Investigation Of The Thermal Performance Of Sierpinski Carpet Fractal Fins In A Natural Convection Environment, Jennifer P. Shaffer 2017 Georgia Southern University

Investigation Of The Thermal Performance Of Sierpinski Carpet Fractal Fins In A Natural Convection Environment, Jennifer P. Shaffer

University Honors Program Theses

This experimental investigation studies the thermal performance of the first four iterations of the Sierpinski carpet pattern in a natural convection environment. This particular fractal geometry is promising in that it increases the available surface area for heat transfer while simultaneously decreasing the mass of the system. This makes it a potentially advantageous design for fins or heat sinks, especially in aerospace applications where minimizing mass of the system is essential. The thermal performance was evaluated by comparing the efficiency, effectiveness, and effectiveness per unit mass for each fractal iteration. The results indicate that efficiency decreases with each fractal iteration ...


A Study Of High Temperature Heat Pipes And The Impact Of Magnetic Field On The Flow Of Liquid Metal, Udit Sharma 2017 Michigan Technological University

A Study Of High Temperature Heat Pipes And The Impact Of Magnetic Field On The Flow Of Liquid Metal, Udit Sharma

Dissertations, Master's Theses and Master's Reports

A study of high temperature heat pipe was conducted to understand its characteristics. A review of working fluid, temperature, wick structure, problems, operational limit and applications was done. Alkali metal were concluded as the most viable candidate for the working fluid.

The impact of three parameters namely magnetic field, heat flux and temperature was analyzed on the performance of HTHP (High Temperature Heat Pipe). The presence of magnetic field had the most considerable impact on reducing the pumping limit of the heat pipe while the temperature had almost negligible effect. Magnetic field results in the pressure drop and adversely affect ...


Incorporation Of Higher Carbon Number Alcohols In Gasoline Blends For Application In Spark-Ignition Engines, Kristina Lawyer 2017 Michigan Technological University

Incorporation Of Higher Carbon Number Alcohols In Gasoline Blends For Application In Spark-Ignition Engines, Kristina Lawyer

Dissertations, Master's Theses and Master's Reports

The 2007 U.S. Renewable Fuel Standard (RFS2) requires an increase in the use of advanced biofuels up to 36 billion gallons by 2022. Higher carbon number alcohols, in addition to cellulosic ethanol and synthetic biofuels, could be used to meet this demand while adhering to the RFS2 corn-based ethanol limitation. Alcohols of carbon numbers 2 through 8 are chosen based on their chemical and engine-related properties.

Blend comparison metrics are developed from automotive industry trends, consumer expectations, U.S. fuel legislation, and engine requirements. The metrics are then used to create scenarios by which to compare higher alcohol fuel ...


Heat Transfer Analysis In A Paddle Reactor For Biomass Fast Pyrolyis, Ankith Ullal 2017 Michigan Technological University

Heat Transfer Analysis In A Paddle Reactor For Biomass Fast Pyrolyis, Ankith Ullal

Dissertations, Master's Theses and Master's Reports

Heat transfer analysis was performed on a novel auger reactor for biomass fast pyrolysis. As part of this analysis, correlations for specific heat capacity and heat transfer coefficients for biomass (sawdust) and sand (used as heat transfer medium) were developed. For sand, the heat transfer coefficient followed a power law distribution with reactor fill level and temperature. For raw biomass, the heat transfer coefficient also showed similar dependence on fill level, but was independent of temperature up to 300°C. These correlations were used in a one dimensional heat transfer model developed to calculate the heating time and heating rate ...


A Physics-Based Approach To Modeling Wildland Fire Spread Through Porous Fuel Beds, Tingting Tang 2017 University of Kentucky

A Physics-Based Approach To Modeling Wildland Fire Spread Through Porous Fuel Beds, Tingting Tang

Theses and Dissertations--Mechanical Engineering

Wildfires are becoming increasingly erratic nowadays at least in part because of climate change. CFD (computational fluid dynamics)-based models with the potential of simulating extreme behaviors are gaining increasing attention as a means to predict such behavior in order to aid firefighting efforts. This dissertation describes a wildfire model based on the current understanding of wildfire physics. The model includes physics of turbulence, inhomogeneous porous fuel beds, heat release, ignition, and firebrands. A discrete dynamical system for flow in porous media is derived and incorporated into the subgrid-scale model for synthetic-velocity large-eddy simulation (LES), and a general porosity-permeability model ...


Proceedings Of The 2nd Resrb 2017 Conference, June 19-21, Wrocław, Poland, Wojciech M. Budzianowski 2016 Wroclaw University of Technology

Proceedings Of The 2nd Resrb 2017 Conference, June 19-21, Wrocław, Poland, Wojciech M. Budzianowski

Wojciech Budzianowski

No abstract provided.


Call For Abstracts - Resrb 2018, June 18-20, Brussels, Belgium, Wojciech M. Budzianowski 2016 Wroclaw University of Technology

Call For Abstracts - Resrb 2018, June 18-20, Brussels, Belgium, Wojciech M. Budzianowski

Wojciech Budzianowski

No abstract provided.


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