Mechanical Engineering Commons^™

Evolution Of The Pore Size Distribution In Sheared Binary Glasses, Nikolai V. Priezjev, Maxim A. Makeev

Mechanical and Materials Engineering Faculty Publications

Molecular dynamics simulations are carried out to investigate mechanical properties and porous structure of binary glasses subjected to steady shear. The model vitreous systems were prepared via thermal quench at constant volume to a temperature well below the glass transition. The quiescent samples are characterized by a relatively narrow pore size distribution whose mean size is larger at lower glass densities. We find that in the linear regime of deformation, the shear modulus is a strong function of porosity, and the individual pores become slightly stretched while their structural topology remains unaffected. By contrast, with further increasing strain, the shear …

Wettability Tailoring Of Nanotube Carpets: Morphology-Chemistry Synergy For Hydrophobic–Hydrophilic Cycling, Lymeng He, Anil Karumuri, Sharmila M. Mukhopadhyay

Mechanical and Materials Engineering Faculty Publications

Carpet-like arrays of carbon nanotubes (CNTs) on graphitic carbon materials have been investigated in order to understand all-carbon hierarchical structures for multifunctional surface-active devices. Pure CNT carpets are seen to be super-hydrophobic as long as they are well aligned. For future applications involving aqueous environments, the ability to tailor the surface wettability and switch it on demand can be very useful, and enable unprecedented devices related to microfluidics, catalysis and sensing/detection systems. In this study, microwave plasma treatments were used to functionalize CNT carpets for a progressive increase in wettability so that they could eventually become super-hydrophilic. This change could …

Automated Impact Device, Jason Montavon

The University Honors Program

This report outlines the progress and development ofan automated impact device (AID). This device was designed to be inexpensive, user-friendly, and modular. Developed with the parameters of vibration analysis. the AID can perform a variety of experimental procedures. Using simple C code and components that are both affordable and easy to obtain, the AID was designed to perform the same task as its more expensive counterparts. With this thought-process, the device was engineered to easily and quickly interchange components depending on the required task. Outlined in the report is the code used to operate the AID and the basic components …

Engine Analysis, Thomas Gaier

The University Honors Program

Engines were invented two hundred years ago but early dynamometers did not benefit from the technological advances until the last hundred years. A John Deere Model E hit-and-miss engine has a nominal power of3hp. The purpose of this project was to analyze this engine, including verifying power.

Outcomes of the analysis of this engine include brake horsepower and thermal efficiency. The first step was to put the engine under a load. This was done with a water pump system. Pressure, water flow, and rotation were measured from tests using the system.This type of system is analogous to a water brake …

Collective Nonaffine Displacements In Amorphous Materials During Large-Amplitude Oscillatory Shear, Nikolai V. Priezjev

Mechanical and Materials Engineering Faculty Publications

Using molecular dynamics simulations, we study the transient response of a binary Lennard-Jones glass subjected to periodic shear deformation. The amorphous solid is modelled as the three-dimensional Kob-Andersen binary mixture at a low temperature. The cyclic loading is applied to slowly annealed, quiescent samples, which induces irreversible particle rearrangements at large strain amplitudes, leading to stress-strain hysteresis and a drift of the potential energy towards higher values. We find that the initial response to cyclic shear near the critical strain amplitude involves disconnected clusters of atoms with large nonaffine displacements. In contrast, the amplitude of shear stress oscillations decreases after …

Identifying Two Regimes Of Slip Of Simple Fluids Over Smooth Surfaces With Weak And Strong Wall-Fluid Interaction Energies, Haibao Hu, Luyao Bao, Nikolai V. Priezjev, Kai Luo

Mechanical and Materials Engineering Faculty Publications

The slip behavior of simple fluids over atomically smooth surfaces was investigated in a wide range of wall-fluid interaction (WFI) energies at low shear rates using non-equilibrium molecular dynamics simulations. The relationship between slip and WFI shows two regimes (the strong-WFI and weak-WFI regimes): as WFI decreases, the slip length increases in the strong-WFI regime and decreases in the weak-WFI regime. The critical value of WFI energy that separates these regimes increases with temperature, but it remains unaffected by the driving force. The mechanism of slip was analyzed by examining the density-weighted average energy barrier (∆E) encountered by fluid atoms …

Low Velocity Impact And Rf Response Of 3d Printed Heterogeneous Structures, Sandeep Keerthi

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Three-dimensional (3D) printing, a form of Additive manufacturing (AM), is currently being explored to design materials or structures with required Electro-Mechanical-Physical properties. Microstrip patch antennas with a tunable radio-frequency (RF) response are a great candidate for 3D printing process. Due to the nature of extrusion based layered fabrication; the processed parts are of three-layer construction having inherent heterogeneity that affects structural and functional response. The purpose of this study is to identify the relationship between the anisotropy in dielectric properties of AM fabricated acrylonitrile butadiene styrene (ABS) substrates in the RF domain and resonant frequencies of associated patch antennas and …

Four-Terminal Square Piezoresistive Sensors For Mems Pressure Sensing, Awlad Hossain, Ahsan Mian

Mechanical and Materials Engineering Faculty Publications

The sensitivity of four-terminal piezoresistive sensors commonly referred to as van der Pauw (VDP) structure is investigated. The VDP sensor is considered to be fabricated on (100) silicon due to its potential application in MEMS (microelectromechanical systems) pressure sensors. The sensitivity of the VDP sensor may be affected by misalignment during the etching/diffusion process, the nonuniformity of piezoresistive coefficients through the sensor thickness, and pad size with respect to the sensor size. For this particular analysis, the effect of VDP stress sensitivity on variations in pad sizes and through-the-thickness -coefficient variation are studied as the effect of misalignment has already …

Defect Engineering: A Path Toward Exceeding Perfection, Hamed Attariani, Kasra Momeni, Kyle R. Adkins

Mechanical and Materials Engineering Faculty Publications

Moving to nanoscale is a path to get perfect materials with superior properties. Yet defects, such as stacking faults (SFs), are still forming during the synthesis of nanomaterials and, according to common notion, degrade the properties. Here, we demonstrate the possibility of engineering defects to, surprisingly, achieve mechanical properties beyond those of the corresponding perfect structures. We show that introducing SFs with high density increases the Young’s Modulus and the critical stress under compressive loading of the nanowires above those of a perfect structure. The physics can be explained by the increase in intrinsic strain due to the presence of …

Modeling Two Phase Flow Heat Exchangers For Next Generation Aircraft, Hayder Hasan Jaafar Al-Sarraf

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Two-phase heat exchangers offer the potential of significant energy transfer by taking advantage of the latent heat of vaporization as the working fluid changes phase. Unfortunately, the flow physics of the phase change process is very complex and there are significant gaps in the fundamental knowledge of how several key parameters are affected by the phase change process. Therefore, an initial investigation modeling a two-phase flow heat exchanger has been accomplished. Many key assumptions have been defined which are critical to modeling two-phase flows. This research lays an initial foundation on which further investigations can build upon. Two-phase heat exchangers …

Development Of Guidance Laws For A Reduced Order Dynamic Aircraft Model, Jack W. Brendlinger

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A set of guidance control laws has been developed for enabling three distinct modes of operation of a reduced order dynamic aircraft model. These include 1) a waypoint following control law, 2) a trajectory tracking control law, and 3) a set of kinematically constrained control laws for reaching a commanded altitude, speed or heading. The formulation of the reduced order model is presented so that the capabilities and limitations of the model are understood, and so that the interface architecture between the controllers and the plant is clearly defined. The controller formulations are then presented, together with sample results. The …

An Automated Controller Design Methodology For Six Degree-Of-Freedom Aircraft Models, Dominic J. Dierker

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This thesis presents an automated design methodology for development of six degree-of-freedom aircraft controllers. The essential functions required of the controller design are 1) to provide sufficient inner loop compensation to guarantee dynamic stability and acceptable handling qualities over the full flight envelope, and, 2) to enable automated mission following capabilities through implementation of outer loop trackers. A hierarchical control architecture consisting of nested nonlinear dynamic inversion control loops is proposed as a means of achieving these top level objectives. Gain tuning based on an automated linearization methodology is then suggested. Next, an automated optimal control allocation algorithm is tested …

Analysis And Sensitivity Study Of Zero-Dimensional Modeling Of Human Blood Circulation Network, Roussel Rahman

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The systemic circulation has a large number of vessels; therefore, 3-D simulation of pulse-wave propagation in the entire cardiovascular system is difficult and computationally expensive. Zero-Dimensional (Zero-D) and One-Dimensional (1-D) models are simplified representations of the cardiovascular network; they can be coupled as supplements to regional 3-D models for closed-loop multi-scale studies or be simulated as self-sufficient representations of the blood-flow network. Unlike Zero-D models, 1-D models can provide linear space-wise information for the vessels. However, Zero-D models can prove to be more useful in particular cases; as flexibility in adjusting parameters facilitate in tailoring the model to specific needs. …

Design And Testing Of Scalable 3d-Printed Cellular Structures Optimized For Energy Absorption, Sagar Dilip Sangle

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Sandwich panel structures are widely used due to their high compressive and flexural stiffness and strength-to-weight ratios, good vibration damping, and low through-thickness thermal conductivity. These structures consist of solid face sheets and low-density cellular core structures that are often based upon honeycomb topologies. Interest in additive manufacturing (AM), popularly known as 3D printing (3DP), has rapidly grown in past few years. The 3DP method is a layer-by-layer approach for the fabrication of 3D objects. Hence, it is very easy to fabricate complex structures with complex internal features that cannot be manufactured by any other fabrication processes. Due to the …

An Investigation On The Stress Intensity Factor Of Surface Micro-Cracks, Sirisha Divya Arli

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The contact fatigue failure in the form of micro or macro-scale pitting is an important failure mode for rolling mechanical elements, such as bearings and gears that are widely used in the automotive, aerospace and wind turbine fields. The micro-pitting process in some cases, gradually removes the surface material through fatigue wear, altering the geometry of the contact surfaces to alleviate the contact pressure decelerating the continued pitting rate. The propagation of the micro-cracks in other cases, goes deep into the material along a shallow angle, turns parallel to the surface at a certain depth, where the maximum shear or …

One Dimensional Computer Modeling Of A Lithium-Ion Battery, Ashwin S. Borakhadikar

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Renewable energy storage is vitally important to many applications for which batteries are the finest choice. As energy storage technology may be applied to a number of areas that differ in power and energy requirements, modeling of battery performance is required. In recent years, a lot of research has been done in this area but, the earliest model was designed by Marc Doyle, T. F. Fuller, and J. Newman in 1993. This work involves the development of a one-dimensional computer model of a lithium-ion battery which consists of three domains: the negative electrode, the separator, and the positive electrode. The …

3d Cfd Investigation Of Low Pressure Turbine Aerodynamics, Jacob Andrew Sharpe

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A 3-D Reynolds-Averaged Navier Stokes (RANS) model of a highly-loaded blade profile has been developed using a commercial CFD code with an unstructured/structured grid and several different turbulence models. The ability of each model to predict total pressure loss performance is examined in terms of the spanwise loss distribution and the integrated total pressure loss coefficient. The flowfield predicted by each model is investigated through comparisons of isosurfaces of Q criterion to previous Implicit Large Eddy Simulation (ILES) results. The 3-equation k-kl-¿ model was shown to provide the most accurate performance predictions for a baseline 3-D LPT geometry, and was …

Turboelectric Distributed Propulsion System For Nasa Next Generation Aircraft, Hashim H. Abada

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Next generation aircraft, more specifically NASA aircraft concepts, will include new technologies and make many advancements in fuel economy and noise. However, there are some challenges associated with the latest technologies that NASA is planning to use for the next generation aircraft. For example, these aircraft concepts require large amounts of electrical power to generate the required thrust throughout a notional flight profile. One of the new technologies is using advanced propulsion systems, such as the Turboelectric Distributed Propulsion (TeDP) system, which is significantly different from current aerospace high bypass turbofan based propulsion system. The TeDP propulsion system replaces the …

A Look At The Optimum Slope Of A Fixed Solar Panel For Maximum Energy Collection For A One Year Time Frame, Salah Alhaidari

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A rule-of-thumb for orientating fixed solar panels for optimum yearly collection of solar radiation that is not influenced by atmospheric effects is to face the panel due south in the Northern Hemisphere or due north in the Southern Hemisphere and to tilt the panel from the horizontal plane at an angle equal to the latitude of the location of the solar panel. The work presented in this thesis shows that this rule-of-thumb is an approximation for no-atmosphere, panel orientation; but not a precise value. This project presents a detailed method for determining the precise optimum tilt angle of a fixed …

Electrical Power And Storage For Nasa Next Generation Aircraft, Saif Al-Agele

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Next generation aircraft will incorporate more electrical power generation and storage for both a distributed electric propulsion system and onboard subsystems. The power generation in this type of aircraft will require orders of magnitude higher than today’s commercial aircrafts, thus producing many challenges. For this reason, a unique, high-powered electric propulsion system primarily powered by a turbo-generator system with electrical storage is being considered. A Simulink/Matlab model has bee created for the electrical power system of the next generation blended wing commercial aircraft proposed by NASA. The components of the electrical system include turbo-generators, generators, battery banks, and electrical distribution …

Low-Velocity Impact Behavior Of Sandwich Panels With 3d Printed Polymer Core Structures, Andrew Joseph Turner

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Sandwich panel structures are widely used in aerospace, marine, and automotive applications because of their high flexural stiffness, strength-to-weight ratio, good vibration damping, and low through-thickness thermal conductivity. These structures consist of solid face sheets and low-density cellular core structures, which are often based upon honeycomb topologies. The recent progress of additive manufacturing (AM) (popularly known as 3D printing) processes has allowed lattice configurations to be designed with improved thermal-mechanical properties. The aim of this work is to design and print lattice truss structures (LTS) keeping in mind the flexible nature of AM. Several 3D printed core structures were created …

Dynamic Modeling And Simulation Of A Variable Cycle Turbofan Engine With Controls, Robert W. Buettner

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Next generation aircraft (especially combat aircraft) will include more technology and capability than ever before. This increase in technology comes at the price of higher electrical power requirements and increased waste heat that must be removed from components to avoid overheating induced shutdowns. To help combat the resulting power and thermal management problem, a vehicle level power and thermal management design and optimization toolset was developed in MATLAB®/Simulink®. A dynamic model of a three-stream variable cycle engine was desired to add to the capabilities of the power and thermal management toolset. As an intermediate step to this goal, the dynamic …

Resilience And Toughness Behavior Of 3d-Printed Polymer Lattice Structures: Testing And Modeling, Mohammed Al Rifaie

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This research focuses on the energy absorption capability of additively manufactured or 3D printed polymer lattice structures of different configurations. The Body Centered Cubic (BCC) lattice structure is currently being investigated by researchers for energy absorption applications. For this thesis, the BCC structure is modified by adding vertical bars in different arrangements to create three additional configurations. Four designs or sets of the lattice structure are selected for comparison including BCC, BCC with vertical bars added to all nodes (BCCV), BCC with vertical bars added to alternate nodes (BCCA), and BCC with gradient arrangements of vertical bars (BCCG). Both experimental …

A Numerical And Experimental Investigation Of Steady-State And Transient Melt Pool Dimensions In Additive Manufacturing Of Invar 36, Chigozie Nwachukwu Obidigbo

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The use of additive manufacturing (AM) in tooling enables low production components to be fabricated with lower costs, reduced waste, increased design flexibility and reduced lead time. Invar 36 is a popular metal tooling material known for its low coefficient of thermal expansion. This work uses thermal finite element (FE) modeling as a tool to determine the feasibility of using Invar 36 in AM and to investigate the transient effect from common scanning strategies. Results show that the steady-state melt pool dimensions behave similar to traditional AM materials for varying process parameters. Transient results show that the melt pool response …

Dynamic Modeling Of Thermal Management System With Exergy Based Optimization, Marcus J. Bracey

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System optimization and design of aircraft is required to achieve many of the long term objectives for future aircraft platforms. To address the necessity for system optimization a vehicle-level aircraft model has been developed in a multidisciplinary modeling and simulation environment. Individual subsystem models developed exclusively in MATLAB-SimulinkTM, representing the vehicle dynamics, the propulsion, electrical power, and thermal systems, and their associated controllers, are combined to investigate the energy and thermal management issues of tactical air vehicle platforms. A thermal vehicle level tip-to-tail model allows conceptual design trade studies of various subsystems and can quantify performance gains across the aircraft. …