Engineering Commons^™

Coalescence Speed Of Two Equal-Sized Nanobubbles, Eric Bird, Jun Zhou, Zhi Liang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In This Work, We Use Molecular Dynamics (MD) Simulations Coupled with Continuum-Based Theoretical Analysis to Study the Coalescence Dynamics of Two Equal-Sized Nanobubbles (NBs). We First Derive a Governing Equation for the Evolution of the Capillary Bridge Radius between Two Coalescing NBs from the Axisymmetric Navier-Stokes Equation. to Verify the Prediction from the Governing Equation, We Carry Out MD Simulations of the Coalescence of Two NBs in a Lennard-Jones Fluid System and Directly Measure the Bridge Radius, Rb, as a Function of Time, T. by Varying the Bubble Diameter, We Change the NB Ohnesorge Number from 0.46 to 0.33. in …

Vibration Analysis Of Simultaneous Drilling And Reaming Bha, Mohammed F. Al Dushaishi, Daniel S. Stutts

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The drillstring used in the oil and gas exploration is a complex structure due to the different forces acting on it. One of the primary sources of drillstring vibrations is the cutting forces caused by the drill bit contact with the rock formation. In some drilling applications, such as hole enlargement and underreaming, the source of the cutting action originates from the drill bit as well as the reamer which increases the dynamic complexity of the drillstring. This paper’s objective is to investigate the torsional vibration behaviors of the bottom hole assembly (BHA) under simultaneous drilling and reaming. More specifically, …

In-Plane Anisotropic Third-Harmonic Generation From Germanium Arsenide Thin Flakes, Huseyin Sar, Jie Gao, Xiaodong Yang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A newly introduced two-dimensional (2D) layered germanium arsenide (GeAs) has attracted growing interest due to its promising highly in-plane anisotropic crystal structure and electronic properties for photonic and optoelectronic applications. The potential of 2D layered GeAs for many applications such as anisotropic photodetection, electronics, superconductivity and thermoelectricity is being investigated in recent studies. However, the intrinsic nonlinear optical properties of 2D layered GeAs have not been explored yet. Here, thickness- and incident polarization-dependent in-plane anisotropic third-harmonic generation (THG) from the mechanically exfoliated thin GeAs flakes is reported. Furthermore, the effect of the flake thickness on the THG conversion efficiency is …

Explosive Compaction Of Additively Manufactured Material, Phillip R. Mulligan, Cody Lough, Douglas A. Bristow, Edward Kinzel, Catherine E. Johnson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Selective Laser Melting (SLM) is an additive manufacturing (AM) technique that uses a laser to locally fuse material in a metal-powder bed. The process is performed in layers enabling significant geometric freedom over traditional manufacturing techniques. During the deposition process, the metal is locally melted and rapidly self-quenched, leading to rapid solidification with well-defined melt-pool boundaries. Analogies are often drawn to the microstructure created in welding, albeit extending to the entire part. The SLM process parameters are optimized to produce near full density metal parts. The process parameters can also be adjusted to produce local regions that are of unmelted …

Direct 3d Printing Of Silica Doped Transparent Magnesium Aluminate Spinel Ceramics, John M. Pappas, Xiangyang Dong

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Transparent magnesium aluminate spinel ceramics were additively manufactured via a laser direct deposition method in this study. With a minimum porosity of 0.3% achieved, highly transparent spinel samples with the highest total optical transmittance of 82% at a wavelength of 632.8 nm, were obtained by a 3D printing approach. However, cracking was found to be a major issue affecting printed spinel samples. To control prevalent cracking, the effect of silica dopants was investigated. Increased silica dopants reduced average total crack length by up to 79% and average crack density by up to 71%. However, a high dopant level limited optical …

Maximum Evaporating Flux Of Molecular Fluids From A Planar Liquid Surface, Eric Bird, Zhi Liang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In This Work, We Use the Kinetic Theory of Gases (KTG) to Develop a Theoretical Model to Understand the Role of Internal Motions of Molecules on the Maximum Evaporation Flux from a Planar Liquid Surface. the Kinetic Theory is Applied to Study the Evaporation of Molecular Fluids into a Vacuum and Predict the Dimensionless Maximum Evaporation Flux (JR,max, I.e., the Ratio of the Maximum Evaporation Flux to the Molar Flux Emitted from a Liquid Surface). the Key Assumptions Regarding the Velocity Distribution Function (VDF) of Polyatomic Molecules in the Highly Nonequilibrium Vapor Near the Evaporating Surface Are Validated by the …

Laser Metal Deposition Of An Alcocrfeniti₀.₅ High-Entropy Alloy Coating On A Ti6al4v Substrate: Microstructure And Oxidation Behavior, Wenyuan Cui, Wei Li, Wei Ting Chen, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Ti6Al4V has been recognized as an attractive material, due to its combination of low density and favorable mechanical properties. However, its insufficient oxidation resistance has limited the high-temperature application. In this work, an AlCoCrFeNiTi_0.5 high-entropy alloy (HEA) coating was fabricated on a Ti6Al4V substrate using laser metal deposition (LMD). The microstructure and isothermal oxidation behaviors were investigated. The microstructure of as-deposited HEA exhibited a Fe, Cr-rich A2 phase and an Al, Ni, Ti-enriched B2 phase. Its hardness was approximately 2.1 times higher than that of the substrate. The oxidation testing at 700⁰C and 800⁰C suggested that the HEA coating …

Lateral Migration Of A Ferrofluid Droplet In A Plane Poiseuille Flow Under Uniform Magnetic Fields, Md Rifat Hassan, Cheng Wang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The lateral migration of a two-dimensional (2D) viscous ferrofluid droplet in a plane Poiseuille flow under a uniform magnetic field is studied numerically by using the level set method. Focusing on low droplet Reynolds number flows (Re_d ≤ 0.05), several numerical simulations are carried out to analyze the effects of magnetic field direction and strength, droplet size, and viscosity ratio on the lateral migration behavior of the droplet. The results indicate that the magnetic field direction plays a pivotal role in the trajectory of lateral migration of the droplet and the final equilibrium position in the channel. When the …

A Review On Metallic Alloys Fabrication Using Elemental Powder Blends By Laser Powder Directed Energy Deposition Process, Yitao Chen, Xinchang Zhang, Mohammad Masud Parvez, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The laser powder directed energy deposition process is a metal additive manufacturing technique, which can fabricate metal parts with high geometric and material flexibility. The unique feature of in-situ powder feeding makes it possible to customize the elemental composition using elemental powder mixture during the fabrication process. Thus, it can be potentially applied to synthesize industrial alloys with low cost, modify alloys with different powder mixtures, and design novel alloys with location-dependent properties using elemental powder blends as feedstocks. This paper provides an overview of using a laser powder directed energy deposition method to fabricate various types of alloys by …

Plasmon-Phonon Coupling Between Mid-Infrared Chiral Metasurfaces And Molecular Vibrations, Md Shamim Mahmud, Daniel Rosenmann, David A. Czaplewski, Jie Gao, Xiaodong Yang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Plasmon-phonon coupling between metamaterials and molecular vibrations provides a new path for studying mid-infrared light-matter interactions and molecular detection. So far, the coupling between the plasmonic resonances of metamaterials and the phonon vibrational modes of molecules has been realized under linearly polarized light. Here, mid-infrared chiral plasmonic metasurfaces with high circular dichroism (CD) in absorption over 0.65 in the frequency range of 50 to 60 THz are demonstrated to strongly interact with the phonon vibrational resonance of polymethyl methacrylate (PMMA) molecules at 52 THz, under both left-handed and right-handed circularly polarized (LCP and RCP) light. The mode splitting features in …

Determination Of Effective Parameters Of Fishnet Metamaterials With Vortex Based Interferometry, Wei Cao, Jie Gao, Xiaodong Yang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Metamaterials are artificially engineered structures that have unique properties not usually found in natural materials, such as negative refractive index. Conventional interferometry or ellipsometry is generally used for characterizing the optical properties of metamaterials. Here, we report an alternative optical vortex based interferometric approach for the characterization of the effective parameters of optical metamaterials by directly measuring the transmission and reflection phase shifts from metamaterials according to the rotation of vortex spiral interference pattern. The fishnet metamaterials possessing positive, zero and negative refractive indices are characterized with the vortex based interferometry to precisely determine the complex values of effective permittivity, …

Effects Of Zirconia Doping On Additively Manufactured Alumina Ceramics By Laser Direct Deposition, John M. Pappas, Aditya R. Thakur, Xiangyang Dong

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The ability to additively manufacture functional alumina ceramics has the potential to lower manufacturing costs and development time for complex components. In this study, the doping effects of zirconia on laser direct deposited alumina ceramics were investigated. The microstructure of the printed samples was analyzed in terms of grain size and composition distribution. The addition of zirconia was found to accumulate along alumina grain boundaries and resulted in significant grain refinement. The zirconia doping largely reduced crack formation during processing compared to that of pure alumina samples. In the case of 10 wt% zirconia, cracking during deposition was nearly completely …

Numerical Study On The Temperature-Dependent Viscosity Effect On The Strand Shape In Extrusion-Based Additive Manufacturing, Behrouz Behdani, Matthew Senter, Leah Mason, Ming-Chuan Leu, Joontaek Park

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A numerical model that incorporates temperature-dependent non-Newtonian viscosity was developed to simulate the extrusion process in extrusion-based additive manufacturing. Agreement with the experimental data was achieved by simulating a polylactic acid melt flow as a non-isothermal power law fluid using experimentally fitted parameters for polylactic acid. The model was used to investigate the temperature effect on the flow behavior, the cross-sectional area, and the uniformity of the extruded strand. OpenFOAM, an open source simulation tool based on the finite volume method, was used to perform the simulations. A computational module for solving the equations of non-isothermal multiphase flows was also …

Thermal Transport Across The Interface Between Liquid N-Dodecane And Its Own Vapor: A Molecular Dynamics Study, Eric Bird, Jesus Gutierrez Plascencia, Zhi Liang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

There Are Two Possible Thermal Transport Mechanisms at Liquid-Gas Interfaces, Namely, Evaporation/condensation (I.e., Heat Transfer by Liquid-Vapor Phase Change at Liquid Surfaces) and Heat Conduction (I.e., Heat Exchange by Collisions between Gas Molecules and Liquid Surfaces). using Molecular Dynamics (MD) Simulations, We Study Thermal Transport Across the Liquid-Vapor Interface of a Model N-Dodecane (C12H26) under Various Driving Force Conditions. in Each MD Simulation, We Restrict the Thermal Energy to Be Transferred Across the Liquid-Vapor Interface by Only One Mechanism. in Spite of the Complex Intramolecular Interactions in N-Dodecane Molecules, Our Modeling Results Indicate that the Schrage Relationships, Which Were Shown …

3d-Printed Biomimetic Bioactive Glass Scaffolds For Bone Regeneration In Rat Calvarial Defects, Krishna C. R. Kolan, Yue-Wern Huang, Julie A. Semon, Ming-Chuan Leu

Biological Sciences Faculty Research & Creative Works

The pore geometry of scaffold intended for the use in the bone repair or replacement is one of the most important parameters in bone tissue engineering. It affects not only the mechanical properties of the scaffold but also the amount of bone regeneration after implantation. Scaffolds with five different architectures (cubic, spherical, x, gyroid, and diamond) at different porosities were fabricated with bioactive borate glass using the selective laser sintering (SLS) process. The compressive strength of scaffolds with porosities ranging from 60% to 30% varied from 1.7 to 15.5 MPa. The scaffold's compressive strength decreased significantly (up to 90%) after …

A Molecular Dynamics Study Of Transient Evaporation And Condensation, Zhi Liang, Anirban Chandra, Eric Bird, Pawel Keblinski

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We Use Molecular Dynamics (MD) Simulations to Study the Transient Evaporation and Condensation of a Pure Fluid Ar in a Nanochannel. in the MD Model, the Evaporation and Condensation of Fluid Ar is Initiated by a Sudden Increase of the Temperature or Periodically Varying the Temperature in the Solid Substrate on One Side of the Nanochannel. in Both Cases, We Find the Transient Evaporation and Condensation Rates Obtained Directly from MD Simulations Are in Good Agreement with the Predictions from the Schrage Relationships. Furthermore, Our Analyses Show that the Kinetics of the Transient Heat and Mass Transfer between the Evaporating …

Laser-Assisted Micromachining Systems And Methods, Yung C. Shin, Xiangyang Dong

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Laser-assisted micromachining methods and systems capable of providing flexible beam positioning and low incident angles. Such laser-assisted micromachining systems preferably include a laser beam source, a cutting tool, means for engaging a workpiece with the cutting tool, optical elements arranged to define a path of a laser beam emitted by the laser beam source wherein the optical elements include at least a first mirror mounted in fixed relation to the laser beam source, and means for adjustably mounting a second mirror to project the laser beam onto the workpiece in proximity to the cutting tool and at an incidence angle …

Frequency-Selective Metasurface Integrated Uncooled Microbolometers, Mahmoud Almasri, Edward C. Kinzel

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A metasurface integrated microbolometer having a sensing layer (e.g., SixGeyO1-x-y). The presence of the metasurface provides selectivity with respect to wavelength, polarization and angle-of-incidence. The presence of the metasurface into the microbolometer affects conversion of electromagnetic to thermal energy, thermal response, electrical integration of the microbolometer, and the tradeoff between resistivity and temperature coefficient of resistance, thereby allowing the ability to obtain a sensing with high temperature coefficient of resistance with lower resistivity values than that of films without the metasurface. The presence of the metasurface removes the need for a Fabry-Perot cavity.

Aluminum Parts Fabricated By Laser-Foil-Printing Additive Manufacturing: Processing, Microstructure, And Mechanical Properties, Chia Hung Hung, Yingqi Li, Austin Sutton, Wei Ting Chen, Xiangtao Gong, Heng Pan, Hai Lung Tsai, Ming-Chuan Leu

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Fabrication of dense aluminum (Al-1100) parts (>99.3% of relative density) by our recently developed laser-foil-printing (LFP) additive manufacturing method was investigated as described in this paper. This was achieved by using a laser energy density of 7.0 MW/cm2 to stabilize the melt pool formation and create sufficient penetration depth with 300 μm thickness foil. The highest yield strength (YS) and ultimate tensile strength (UTS) in the LFP-fabricated samples reached 111 ± 8 MPa and 128 ± 3 MPa, respectively, along the laser scanning direction. These samples exhibited greater tensile strength but less ductility compared to annealed Al-1100 samples. Fractographic …

Metal Additive Manufacturing Parts Inspection Using Convolutional Neural Network, Wenyuan Cui, Yunlu Zhang, Xinchang Zhang, Lan Li, Frank W. Liou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Metal additive manufacturing (AM) is gaining increasing attention from academia and industry due to its unique advantages compared to the traditional manufacturing process. Parts quality inspection is playing a crucial role in theAMindustry, which can be adopted for product improvement. However, the traditional inspection process has relied on manual recognition, which could suffer from low efficiency and potential bias. This study presented a convolutional neural network (CNN) approach toward robust AM quality inspection, such as good quality, crack, gas porosity, and lack of fusion. To obtain the appropriate model, experiments were performed on a series of architectures. Moreover, data augmentation …

On The Investigation Of Hot Tearing Behavior Of Continuous Cast Steel, Yanru Lu

Masters Theses

”Hot tearing has long been recognized as a major problem that plagues the development of the continuous casting process and results in low-quality products. Understanding of the mechanisms and the required conditions for the hot tearing formation is important for industries but has not been well-established yet. Thus, this research focuses on the hot tearing issue observed in continuous cast steel, by providing a summary of the current research progress and then introducing a new laboratory method to determine the thermo-mechanical properties relevant to hot tearing of different steel grades under different solidification conditions. In this method, an apparatus was …

Time- And Space-Dependent Uncertainty Analysis And Its Application In Lunar Plasma Environment Modeling, Xinpeng Wei

Doctoral Dissertations

”During an engineering system design, engineers usually encounter uncertainties that ubiquitously exist, such as material properties, dimensions of components, and random loads. Some of these parameters do not change with time or space and hence are time- and space-independent. However, in many engineering applications, the more general time- and space-dependent uncertainty is frequently encountered. Consequently, the system exhibits random time- and space-dependent behaviors, which may result in a higher probability of failure, lower average lifetime, and/or worse robustness. Therefore, it is critical to quantify uncertainty and predict how the system behaves under time- and space- dependent uncertainty. The objective of …

Hydrokinetic Turbine Composite Blades And Sandwich Structures: Damage Evaluation And Numerical Simulation, Mokhtar Fal

Doctoral Dissertations

“Composite materials are gaining interest due to their high strength to weight ratio. This study deals with both experimental and numerical approaches to cover the aspects of the failure of composite materials in hydrokinetic turbine applications. In Part I, the location and magnitude of failure in the horizontal axis water turbine carbon fiber-reinforced polymer (CFRP) composite blades with different laminate stacking sequences were investigated. Two lay-up orientations were adopted for this work ([0⁰]₄ and [0⁰/90⁰]_2s). A finite element analysis model was generated to examine the stresses along the blade. Five angles were introduced to study the effect …

Performance Evaluation Of Alsi10mg Fabricated By A Selective Laser Melting Process, David Michael Murphy

Masters Theses

“Selective laser melting is becoming a widely used additive manufacturing technique that melts metal powder in a layer by layer process in order to build a desired part or geometry. Like many additive processes, selective laser melting allows for fabrication of parts with complex geometries. In order to fabricate a fully dense part there are a number of variables to take into account including: powder characteristics, laser parameters, and environmental parameters. Each of these variables can affect the microstructure and thus the mechanical performance of an additively manufactured part. In this work, the aluminum alloy AlSi10Mg was investigated. AlSi10Mg is …

Modal Analysis As Non-Destructive Testing Technique For Additively Manufactured 304l Stainless Steel Parts, Tristan N. Cullom

Masters Theses

“Non-Destructive Testing (NDT) methods for Additively Manufactured (AM) parts is an ongoing field of research in the additive community due to its ability to determine if a part can be deemed viable for field usage. This study presents modal analysis as a NDT method for AM parts. For production builds that have multiple copies of the same part, a correcting technique can be used such that the frequencies of the parts under test can be reliably compared against each other, which saves both time and money compared to other traditional NDT methods. This study was able to develop a novel …

Influence Of Input Energy On Mechanical Properties Of Laser Powder Bed Fused Aisi 304l Stainless Steel, Tan Pan

Masters Theses

“Powder Bed Fusion process with selective laser melting technique is popularly adopted in additive manufacturing area on account of its layer by layer manufacturing fashion capable of fabricating components with complex internal and external geometries and structures. However, the process-property map is unique and vital for different materials and AM configurations used for fabrication. The process parameter is identified as a significant factor that heavily influences the properties and performances of the printed materials.

Current work aimed to extend the existing knowledge on Laser Powder Bed Fusion fabricated AISI 304L by accessing the influence of varying energy input on the …

Mid-Infrared Chiral Metsurface Coupling With Molecular Vibration, Md Shamim Mahmud

Masters Theses

“The mid-infrared design of chiral metamaterial shows a tremendous absorption capability of infrared rays, and it has the significant application of circular dichroism based device development. Plasmon-phonon coupling is one of the application of metamaterial that provides a new path for tailoring the surface in the nanoscale, which is also applicable in molecules detection. It is possible to change the Plasmon-Phonon coupling strength not only through the chemical change of molecules but also by changing the metamaterial light-matter interaction property. So far, linearly polarized light shows the strong coupling between metamaterial and molecules. However, it is possible to observe strong …

Finite Time Suboptimal Control Design Of Nonlinear Systems With Θ-D Technique And Implementation To Aerospace Applications, Jie Yao

Doctoral Dissertations

“A finite time suboptimal control strategy (named θ - D approximated algorithm) was proposed in this study, which can provide the control engineers with a novel effective and efficient design tool from the finite time optimal perspective. Based on the framework of this proposed method, the original nonlinear dynamics were formulated in pseudo-linear form, and the performance index was denoted by a linear quadratic regulator prototype in this research. After that, the approximated solutions to intractable Hamilton-Jacobi-Bellman (HJB) equation were acquired by putting vanishing perturbation terms into the performance index. By tuning the parameters in perturbation terms, semi-global stability and …

Combustion And Emission Characteristics Of Ic Engines Fueled By Hydrogen And Hydrogen/Diesel Mixtures And Multi-Objective Optimization Of Operating Parameters, Abdulhakim Issa Jabbr

Doctoral Dissertations

“The present study considers combustion of hydrogen in IC engines. In general, the work focuses on simulating the engine performance and emissions at different operation parameters, and using optimization techniques. Task I work deals with the engine performance and emissions of a single cylinder spark-ignition (SI) engine fueled by hydrogen. The engine was simulated at different equivalence ratios, exhaust gas recirculation (EGR) and ignition timing. The results indicate that NOx emissions, engine power, and efficiency are reduced by increasing EGR level, and increased with increasing equivalence ratio and advanced ignition timing. The best operating conditions for hydrogen engines were obtained …

Human Behavior Understanding For Worker-Centered Intelligent Manufacturing, Wenjin Tao

Doctoral Dissertations

“In a worker-centered intelligent manufacturing system, sensing and understanding of the worker’s behavior are the primary tasks, which are essential for automatic performance evaluation & optimization, intelligent training & assistance, and human-robot collaboration. In this study, a worker-centered training & assistant system is proposed for intelligent manufacturing, which is featured with self-awareness and active-guidance. To understand the hand behavior, a method is proposed for complex hand gesture recognition using Convolutional Neural Networks (CNN) with multiview augmentation and inference fusion, from depth images captured by Microsoft Kinect. To sense and understand the worker in a more comprehensive way, a multi-modal approach …