Mechanical Engineering Commons^™

Introduction Of Planar Compliant Joints Designed For Combined Bending And Axial Loading Conditions In Lamina Emergent Mechanisms, Samuel E. Wilding, Larry L. Howell, Spencer P. Magleby

Faculty Publications

This work introduces three joints to allow motion in lamina emergent mechanisms (LEMs) that were designed to have minimal parasitic motion under tension, compression, and a combination of tension and compression loading. Closed-form models of the joints were developed and combined with optimization algorithms for maximum flexibility in bending and then modeled using finite element analysis (FEA). The FEA results were used to predict the stiffness of the joints in bending, tension, and compression. As a baseline, lamina emergent torsional (LET) joints were designed to match the bending stiffness of each of the joints, so that the tensile-compressive performance could …

Thermal And Mechanical Properties Of Nitrate Thermal Storage Salts In The Solid-Phase, Brian D. Iverson, Scott T. Broome, Alan M. Kruizenga, Joseph G. Cordaro

Faculty Publications

Implementation of molten salt compounds as the heat transfer fluid and energy storage medium provides specific benefits to energy collection and conversion. Nitrate salts have been identified as a strong candidate for energy transfer and storage and have been demonstrated for use in these applications over time. As nitrate salts have solidification temperatures above ambient, concern for recovery from salt freezing events has instigated efforts to understand and predict this behavior. Accurate information of salt property behavior in the solid-phase is necessary for understanding recovery from a freeze event as well as for phase change thermal energy storage applications. Thermal …

Enhanced Methanol Oxidation And Co Tolerance Using Ceo2-Added Eggshell Membrane-Templated Pd Network Electrocatalyst, Qunwei Tang, Zhengping Mao, Shuguo Ma, Kevin Huang

Faculty Publications

Macroporous Pd and CeO₂-added Pd network catalysts have been synthesized using eggshell membrane (ESM) as a template for enhanced methanol oxidation and CO tolerance. The microstructural characterization revealed a hierarchically ordered macroporous network of Pd reproducing the fibrous structure of ESM for a Pd-only catalyst, and a flower-like CeO₂-decorated Pd morphological architecture for the CeO₂-added Pd catalyst synthesized by a precipitation method. XRD patterns indicated Pd and CeO₂ phases with good crystallinity. The cyclic voltammetry studies showed an enhanced electrocatalytic activity for methanol oxidation in acidic aqueous medium. Because of the preferential formation …

A Comparison Of Homes Built To The 2009 And 1984 Florida Energy Codes, Florida Solar Energy Center, Charles Withers, Jr.

FSEC Energy Research Center®

The Florida Solar Energy Center conducted research into the effectiveness of the Florida energy code to reduce energy use in residential buildings. FSEC examined two groups of homes: those built to the 1984 energy code (June 1,1984-1985) and those built to the 2007 with 2009 supplement energy code (March 1, 2009-2010). This report discusses data collection methods, analysis and results that focus on comparisons of measured energy use and house characteristics between both code periods.

Liquid Jet Impingement Experiments On Micro Rib And Cavity Patterned Superhydrophobic Surfaces In Both Cassie And Wenzel States, Michael G. Johnson

Theses and Dissertations

Experiments were performed to characterize hydraulic jumps that form due to liquid jet impingement on superhydrophobic surfaces with alternating micro-ribs and cavities. If the surface is unimmersed, a surface tension based transition into droplets occurs, so a known depth of water was imposed downstream from the hydraulic jump to ensure the existence of a hydraulic jump. The surfaces are characterized by the cavity fraction, which is defined as the width of a cavity divided by the combined width of a cavity and an adjoining rib. Four different surface designs were studied, with respective cavity fractions of 0 (smooth surface), 0.5, …

Effects Of Haptic And 3d Audio Feedback On Pilot Performance And Workload For Quadrotor Uavs In Indoor Environments, Robert Mark Philbrick

Theses and Dissertations

Indoor flight of unmanned aerial vehicles (UAVs) has many applications in environments in which it is undesirable or dangerous for humans to be, such as military reconnaissance or searching for trapped victims in a collapsed building. However, limited visual feedback makes it difficult to pilot UAVs in cluttered and enclosed spaces. Haptic feedback combined with visual feedback has shown to reduce the number of collisions of UAVs in indoor environments; however, it has increased the mental workload of the operator. This thesis investigates the potential of combining novel haptic and 3D audio feedback to provide additional information to operators of …

An Experimental Investigation Of Strain Rate, Temperature And Humidity Effects On The Mechanical Behavior Of A Perfluorosulfonic Acid Membrane, Zongwen Lu, Melissa Lugo, Michael H. Santare, Anette M. Karlsson, F. Colin Busby, Peter Walsh

Mechanical Engineering Faculty Publications

The time-dependent hygro-thermal mechanical behavior of a perfluorosulfonic acid (PFSA) membrane (Nafion^® 211 membrane) commonly used in Proton Exchange Membrane Fuel Cells (PEMFCs) is investigated at selected strain rates for a broad range of temperatures and humidities. Tensile tests and relaxation tests are conducted to determine Young’s modulus and proportional limit stress as functions of strain rate, temperature and humidity. The results show that Young’s modulus and proportional limit stress increase as the strain rate increases, and decrease as the temperature or humidity increases. The results also show that the mechanical response of Nafion^® 211 membrane is more …

Effect Of Time-Dependent Material Properties On The Mechanical Behavior Of Pfsa Membranes Subjected To Humidity Cycling, Narinder S. Khattra, Anette M. Karlsson, Michael H. Santare, Peter Walsh, F. Colin Busby

Mechanical Engineering Faculty Publications

A viscoelastic-plastic constitutive model is developed to characterize the time-dependent mechanical response of perfluorosulphonic acid (PFSA) membranes. This model is then used in finite element simulations of a representative fuel cell unit, (consisting of electrodes, gas diffusion layer and bipolar plates) subjected to standardized relative humidity (RH) cycling test conditions. The effects of hold times at constant RH, the feed rate of humidified air and sorption rate of water into the membrane on the stress response are investigated. While the longer hold times at high and low humidity lead to considerable redistribution of the stresses, the lower feed and sorption …

Platinum Nanocatalytic Combustion Of Methanol-Air Mixture, James Applegate

Theses and Dissertations

Catalytic combustion's ability to release the potential energy of high energy density fuels could transform the portable electronic device market by removing the reliance on batteries. Catalytic combustion is a generally well understood combustion technique, but the effects of specific experimental conditions (catalyst loading, flow rates and substrates) on catalyst performance are not as well known. Systhesized catalytic Pt nonoparticles (dp ~ 11.6 nm) were dispersed on a cordierite substrate and were characterized using TEM, XRD and SEM. Experimental results were obtained in a miniature-scale continuous flow reactor. Subsequent studies report the effect catalyst loading and reactor flow parameters have …

Novel Crankshaft Mechanism And Regenerative Braking System To Improve The Fuel Economy Of Light Duty Vehicles And Passenger Cars, Alberto A. Boretti, Joseph Scalzo

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Improvements of vehicle fuel economy may be achieved by the introduction of advanced internal combustion engines (ICE) improving the fuel conversion efficiency of the engine and of advanced power trains (PWT) reducing the amount of fuel energy needed to power the vehicle. the paper presents a novel design of a variable compression ratio advanced spark ignition engine that also permits an expansion ratio that may differ from the compression ratio hence generating an Atkinson cycle effect. the stroke ratio and the ratio of maximum to minimum in-cylinder volumes may change with load and speed to provide the best fuel conversion …

Molecular Dynamics Simulations Of Oscillatory Couette Flows With Slip Boundary Conditions, Nikolai V. Priezjev

Mechanical and Materials Engineering Faculty Publications

The effect of interfacial slip on steady-state and time-periodic flows of monatomic liquids is investigated using non-equilibrium molecular dynamics simulations. The fluid phase is confined between atomically smooth rigid walls, and the fluid flows are induced by moving one of the walls. In steady shear flows, the slip length increases almost linearly with shear rate. We found that the velocity profiles in oscillatory flows are well described by the Stokes flow solution with the slip length that depends on the local shear rate. Interestingly, the rate dependence of the slip length obtained in steady shear flows is recovered when the …

Energy Storage Characteristics Of A New Rechargeable Solid Oxide Iron-Air Battery, Xuan Zhao, Nansheng Xu, Xue Li, Yunhui Gong, Kevin Huang

Faculty Publications

Cost effective and large scale energy storage is critical to renewable energy integration and smart-grid energy infrastructure. Rechargeable batteries have great potential to become a class of cost effective technology suited for large scale energy storage. In this paper, we report the energy storage characteristics of a newly developed rechargeable solid oxide iron–air battery. Investigations of the battery’s performance under various current densities and cycle durations show that iron utilization plays a determining role in storage capacity and round-trip efficiency. Further studies of the battery's cycle life reveal a unique charge-cycle originated degradation mechanism that can be interpreted by a …

Measured Performance Of Occupied, Side-By-Side, South Texas Homes, Florida Solar Energy Center, Dave Chasar

FSEC Energy Research Center®

The performance of three occupied homes built in 2009 in San Antonio, Texas with identical floor plans and orientation were evaluated through a partnership between the Florida Solar Energy Center, CPS Energy, and Woodside Homes of South Texas. Measurements included whole-house gas and electricity use as well as heating, cooling, hot water, major appliances, and indoor and outdoor conditions. One home built to the builder's standard practice served as the control; the other homes demonstrated high performance features.

The goals of this research were to: (1) learn how energy systems affect peak load profiles during the hottest weather conditions; (2) …

Controlled Deflection Approach For Rotor Crack Detection, Zbigniew Kulesza, Jerzy T. Sawicki

Mechanical Engineering Faculty Publications

Atransverse shaft crack is a serious malfunction that can occurdue to cyclic loading, creep, stress corrosion, and other mechanismsto which rotating machines are subjected. Though studied for manyyears, the problems of early crack detection and warning arestill in the limelight of many researchers. This is dueto the fact that the crack has subtle influence onthe dynamic response of the machine and still there areno widely accepted, reliable methods of its early detection. Thispaper presents a new approach to these problems. The methodutilizes the coupling mechanism between the bending and torsional vibrationsof the cracked, nonrotating shaft. By applying an external lateralforce …

Mitigation Of Pore Generation In Laser Welding Of Magnesium Alloy Az31b In Lap Joint Configuration, Masoud Harooni, Fanrong Kong, Blair Carlson, Radovan Kovacevic

Mechanical Engineering Research

Magnesium, as the lightest structural metal, has been widely used in the automotive and aerospace industries. Porosity is the main issue in the welding of magnesium alloys and can be caused by surface coatings, hydrogen gas, pre-existing porosity, the collapse of an unstable keyhole and vaporization of alloying elements. In this study, the effect of the oxide layer on pore generation in the welding of AZ31B-H24 magnesium alloy is investigated. A fiber laser with a power of up to 4 kW is used to weld samples in a lap joint configuration. Two groups of samples are studied: as received (AR) …

Studying The Effect Of Laser Welding Parameters On The Quality Of Zek100 Magnesium Alloy Sheets In Lap Joint Configuration, Masoud Harooni, Fanrong Kong, Blair Carlson, Radovan Kovacevic

Mechanical Engineering Research

Magnesium, as the lightest structural metal, has been widely used in the automotive and aerospace industries. Porosity is the main issue in the welding of magnesium alloys and can be caused by surface coatings, hydrogen gas, pre-existing porosity, the collapse of an unstable keyhole and vaporization of alloying elements. In this study, the effect of the oxide layer on pore generation in the welding of AZ31B-H24 magnesium alloy is investigated. A fiber laser with a power of up to 4 kW is used to weld samples in a lap joint configuration. Two groups of samples are studied: as received (AR) …

Stochastic Reactor Modelling Of Multi Modes Combustion With Diesel Direct Injection Or Hydrogen Jet Ignition Start Of Combustion, Alberto A. Boretti

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Recent papers [1-5] have proposed two different systems to more efficiently and more rapidly burn the fuel in highly boosted, high compression ratio, directly injected internal combustion engines permitting multi-mode combustion operation. in a first system, a second direct injector is coupled with the standard Diesel direct injector and glow plug. the second direct injector introduces most of the fuel while the Diesel direct injector only introduces a minimum amount of fuel to control the start of the combustion about top dead center. the fuel injected before the Diesel ignition injection burns premixed, the fuel injected after the Diesel ignition …

Me-Em Enewsbrief, September 2012, Department Of Mechanical Engineering-Engineering Mechanics, Michigan Technological University

Department of Mechanical and Aerospace Engineering eNewsBrief

No abstract provided.

Maximal Force Characteristics Of The Ca2+-Powered Actuator Of Vorticella Convallaria, Sangjin Ryu, Matthew J. Lang, Paul Matsudaira

Department of Mechanical and Materials Engineering: Faculty Publications

The millisecond stalk contraction of the sessile ciliate Vorticella convallaria is powered by energy from Ca²⁺ binding to generate contractile forces of ~10 nN. Its contractile organelle, the spasmoneme, generates higher contractile force under increased stall resistances. By applying viscous drag force to contracting V. convallaria in a microfluidic channel, we observed that the mechanical force and work of the spasmoneme depended on the stalk length, i.e., the maximum tension (150–350 nN) and work linearly depended on the stalk length (~2.5 nN and ~30 fJ per 1 mm of the stalk). This stalk-length dependency suggests that motor units of …

A Method To Generate Pressure Gradients For Molecular Simulation Of Pressure-Driven Flows In Nanochannels, Zhi Liang, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

One of the Difficulties in Molecular Simulation of Pressure-Driven Fluid Flow in Nanochannels is to Find an Appropriate Pressure Control Method. When Periodic Boundary Conditions (PBCs) Are Applied, a Gravity-Like Field Has Been Widely Used to Replace Actual Pressure Gradients. the Gravity-Fed Method is Not Only Artificial, But Not Adequate for Studying Properties of Fluid Systems Which Are Essentially Inhomogeneous in the Flow Direction. in This Paper, a Method is Proposed Which Can Generate Any Desired Pressure Difference to Drive the Fluid Flow by Attaching a "Pump" to the Nanofluidic System, While the Model is Still Compatible with PBCs. the …

Optimal Reduction Of Electrical Energy Consumption By Supply Air Ac Motors, Keyhan Rafiee

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

The Nebraska Center for Energy Sciences Research (NCER) at the University of Nebraska-Lincoln (UNL) strives to be energy efficient through Green Energy. Of course, in meeting some of the requirements for different types of Leadership in Energy and Environmental Design (LEED) certification, certain minimum levels of energy efficiency practices must be met. One such level of energy efficiency, in particular, is reduction in the consumption of electrical energy in buildings. This thesis is a study of methods of reducing the consumption of electrical energy (measured in kW of electrical power) in the UNL Jorgensen Hall (JH) air handling unit 2 …

H3Po4-Imbibed Three-Dimensional Polyacrylamide/Polyacrylamide Hydrogel As A High-Temperature Proton Exchange Membrane With Excellent Acid Retention, Qunwei Tang, Guoging Qian, Kevin Huang

Faculty Publications

We herein report the use of polyacrylamide/polyacrylamide interpenetrating polymer network (PAM/PAM IPN) hydrogel as a matrix to imbibe proton conducting H₃PO₄, forming a robust proton exchange membrane (PEM) suitable for high-temperature PEM fuel cells by combining excellent acid retention, simple synthesis, and low cost. Its extraordinary ability to absorb large quantity of aqueous solution is fully utilized to achieve high H₃PO₄ loading, showing a proton conductivity of 0.0833 S cm−1 at 183 °C in dry air. The synthesized membrane also shows excellent acid retention even under mechanical load and high humidity. These profound …

Rigid Finite Element Model Of A Cracked Rotor, Zbigniew Kulesza, Jerzy T. Sawicki

Mechanical Engineering Faculty Publications

The article introduces a new mathematical model for the cracked rotating shaft. The model is based on the rigid finite element (RFE) method, which has previously been successfully applied for the dynamic analysis of many complicated, mechanical structures. In this article, the RFE method is extended and adopted for the modeling of rotating machines. An original concept of crack modeling utilizing the RFE method is developed. The crack is presented as a set of spring–damping elements of variable stiffness connecting two sections of the shaft. An alternative approach for approximating the breathing mechanism of the crack is introduced. The approach …

The Role Of Transport Phenomena In The Direct Oxidation Of Solid Fuels, Charles J. Banas

Master's Theses

Direct carbon fuel cells have shown promise for stationary power generation by utilizing the direct oxidation of a solid carbon fuel source at the anode. In laboratory settings, researchers have reported up to 300mA/cm2 of current density from these cells types which suffer from mass transport losses. This paper studies the surface properties of the solid fuel source, and describes the process of CO2 evolution through an analogy to pool boiling. In nucleate boiling (a subset of pool boiling) vapor bubbles grow from nucleation sites where gas are trapped in micro-cavities on the surface. Carbon surfaces possess these same features, …

Magneto-Elastic Behavior In Hard- And Soft-Mre's Including Demagnetizing Effects, Juan Roche

Theses and Dissertations

This thesis studies the magnetic and mechanical behavior of magnetorheological elastomers (MREs) based on four possible permutations defined along particle alignment (Aligned and Unaligned) and magnetization (Hard- or Soft-magnetic) pairs. These pairs designations yield classes A-H, U-H, A-S and U-S. The last two classes comprise traditional MREs. Samples were fabricated by mixing DOW HS II silicone elastomer compound and 30% by volume of either nominally 40-micron M-type barium hexaferrite (BaM) or 325-mesh iron (Fe) particles cured with or without the presence of a magnetic field. Magnetization and density measurements were employed to help confirm fabrication of the four distinct classes. …

Friction Stir Spot Welding Of Ultra-High Strength Steel, Trent J. Hartman

Theses and Dissertations

Friction stir spot welding (FSSW) is quickly becoming a method of interest for welding of high strength steel (HSS) and ultra high strength steel (UHSS). FSSW has been shown to produce high quality welds in these materials, without the drawbacks associated with fusion welding. Tool grade for polycrystalline cubic boron nitride (PCBN) tools has a significant impact on wear resistance, weld quality, and tool failure in FSSW of DP 980 steel sheet. More specifically, for a nominal composition of 90% CBN, the grain size has a significant impact on the wear resistance of the tool. A-type tools performed the best, …

Mechanism State Matrices For Spatial Reconfigurable Mechanisms, Philip A. Voglewede, Brian Korves, Brian Slaboch

Mechanical Engineering Faculty Research and Publications

This paper improves augmented mechanism state matrices by replacing joint code with screw system notation. The proposed substitution allows for a more specific description of the joints in the mechanism and the capability to describe both spatial and planar mechanisms. Examples are provided which elucidate the proposed approach.

Fuzzy Statistical Refinement For The Forecasting Of Tenders For Roadway Construction, Jeng-Wen Lin, Cheng-Wu Chen, Ting-Chang Hsu

Journal of Marine Science and Technology–Taiwan

Due to market competition, construction companies often place low bids when tenders are invited for domestic public construction projects. Over-competition can lead to vicious price wars to win a tender, which can in turn seriously affect the quality of construction. This study aims to establish an accurate Taiwan based model for the forecasting of the tendered price for roadway construction. This model is designed to assist the public sector to determine what would be a reasonable reserve price or award price. In order to ensure accurate predictions, a data classification system is established using fuzzy set theory. For each category …

An Arc Code To Predict The Thermal Crack Of Welded Sample, Je-Ee Ho

Journal of Marine Science and Technology–Taiwan

In this study, a numerical code with enthalpy method in upwind scheme is proposed to estimate the distribution of thermal stress in the molten pool, which is primarily determined by the type of the input power and travel speed of heating source. To predict the cracker deficit inside the workpiece, a simulated program satisfying the diagonal domination and Scarborough criterion provides a stable iteration. Meanwhile, an experimental performance, operated by robot arm “DR-400” to provide a steady and continuous arc welding, was also conducted to verify the simulated result. By surveying the consistence of molten pool bounded by contrast shade …

Rust-Expansion-Crack Service Life Prediction Of Existing Reinforced Concrete Bridge/Viaduct Using Time-Dependent Reliability Analysis, Ming-Te Liang, Jiang-Jhy Chang, Han-Tung Chang, Chi-Jang Yeh

Journal of Marine Science and Technology–Taiwan

It is necessary to develop a calculation method to help in the making of feasible, reliable, and serviceable predictions for the service lives of bridge or viaduct structures. This article presents the basis for doing rust-expansion-crack service life predictions for existing reinforced concrete (RC) bridges and viaducts in chloride-laden environments based on timedependant reliability modeling due to the corrosion of steel in concrete. The corrosion process has three stages, the initiation (diffusion or carbonation) time (ti = tc), the depassivation time (tp), and the propagation (corrosion) time (tcorr). The rustexpansion-crack service lives (tcr) of existing RC bridges or viaducts can …