bluuebunny/crossref_metadata_2025 huggingface dataset:
A Simplified Hydroplaning Simulation for a Straight-Grooved Tire by Using FDM, FEM and an Asymptotic Method
Authors: Oh Changwon , Kim Taewung , Park Kwonshik , Jeong Hyun-Yong
Published: May 2009

Much research has been conducted to simulate the hydroplaning phenomenon of tires using commercial explicit FEM (finite element method) codes such as MSC.Dytran and LS-DYNA. However, it takes a long time to finish such a simulation because its model has a great number of Lagrangian and Eulerian elements and a contact should be defined between the two different types of elements, and the simulation results of the lift force and the contact force are oscillatory. Thus, in this study a new methodology was proposed for the hydroplaning simulation using two separate mathematical models; an FDM (finite difference method) code was developed to solve Navier-Stokes and continuity equations and consequently to obtain the pressure distribution around a tire with the inertia and the viscous effects of water taken into account, and an FE tire model was used to obtain the deformed shape of the tire due to the vertical load and the pressure distribution. The two models were iteratively used until a converged pressure distribution was obtained. Since the converged pressure distribution could not be obtained near or at the contact zone due to very shallow water, an asymptotic method was also proposed to estimate the pressure distribution. This new simulation methodology was applied to a straight-grooved tire, and its hydroplaning speed was determined for the water depth of 5 mm, 10 mm, 15 mm and 20 mm. In addition, a simplified simulation method was proposed instead of the fully iterative method. Only one iteration was conducted at each speed to reduce the total number of iterations, still resulting in a similar hydroplaning speed. Moreover, a new simulation methodology of using LS-DYNA was proposed, and its results were compared with those from the iterative method in terms of accuracy and efficiency.
Conductivity Measurement of Ferrofluid Using Transient Hot Wire Method
Authors: Gutierrez Gustavo , Rodriguez Radhames
Published: May 2009

Thermal conductivity of the ferrofluids is a difficult property to predict theoretically. Existing models can not explain the real behavior of such fluids and mismatch the results found in the experiments. Experimentation is then the most reliable way to determine the observed enhancement in thermal conductivity of ferrofluids. The transient hot wire method is an experimental technique in which the thermal conductivity is obtained by measuring a temperature change, respect to time in a thin wire, caused by a constant current passing through it. Some advantages of this method are the almost complete elimination of natural convection effects, its fast implementation and its high accuracy. In order to use the transient hot-wire technique in a ferrofluid a modification must be made because the transient hot-wire method cannot be applied to electrical conducting fluids since part of the current will be conducted by the fluid, generating uncertainties in the current passing through the wire. These uncertainties will affect the voltage measurement over predicting the thermal conductivity. To prevent the current to pass through the fluid the hot wire has to be covered with an electrical insulating coating. Then, it is necessary to calibrate the wire with a calibrating constant in order to correct the effect of the coating in the RTD. For calibration purposes, thermal conductivity measurements of known fluids have been carried out. For this purpose, substances like water, toluene acetone and heptane are used. In this study the transient hot-wire method is implemented to measure the thermal conductivity of different water-based ferrofluids and oilbased ferrofluids. Parametric Studies are carried out numerically to understand the effect of the coating in the technique.
Phase-Field Modeling of Droplet Movement Using the Discontinuous Finite Element Method
Authors: Chen H. , Shu Y. , Li B. Q. , Mohanty P. , Sengupta S.
Published: May 2009

In this paper, a discontinuous finite element method is presented for the fourth-order nonlinear Cahn-Hilliard equation that models multiphase flows together with the Navier-Stokes equations. A flux scheme suitable for the method is proposed and analyzed together with numerical results. The model is applied to simulate the droplet movement and numerical results are presented.
Measurement of Arterial Wave Velocity With Ultrasound
Authors: Zhang Xiaoming , Pislaru Cristina , Kinnick Randall R. , Greenleaf James F.
Published: May 2009

Pulse wave velocity (PWV) is widely used for estimating the stiffness of an artery. PWV is measured by the time of travel of the “foot” of the pressure wave over a known distance. This technique has a low time resolution and is an average measurement of artery stiffness between the two measuring positions. In this paper an arterial wave is generated non-invasively in the vessel wall by the radiation force of ultrasound. The wave velocity in the vessel is measured non-invasively by ultrasound with high time resolution over a short distance of a few millimeters.
Mechanical Response of Single Biological Cells to Externally Applied Forces
Authors: Samuel B. A. , Haque M. A.
Published: May 2009

We present an experimental technique capable of applying and measuring very small forces (nanoNewtons) on live biological cells. The technique is based on combing microfabricated molded elastomeric microneedles, and substrate deformation to actively apply loads on single cells. By using fluorescence and differential interference contrast imaging we can quantitatively study the response of biological cells to force exerted on it via the extra cellular matrix. Bovine Aortic Endothelial Cells were cultured on the micropillars and strained in-vitro to demonstrate the experimental technique.
Advanced Model of Radiative Heat Transfer in a Rod Geometry
Authors: Kobelev Gennadii V. , Strizhov Valerii F. , Vasiliev Alexander D.
Published: May 2009

Radiative heat transfer is very important in different fields of mechanical engineering and related technologies including heat transfer in furnaces, aerospace, nuclear reactors, different high-temperature assemblies. In particular, in the course of a hypothetical severe accident at pressurized water reactor (PWR) the temperatures inside the reactor vessel reach high values at which taking into account of radiative heat exchange between the structures of reactor (including core and other reactor vessel elements) gets important. Existing models of radiative heat exchange use many limitations and approximations like approximate estimation of view factors and beam lengths. The module MRAD was used in this paper to model the radiative heat exchange in rod-like geometry typical of PWR. Radiative heat exchange is computed using dividing on zones (zonal method) as in existing radiation models implemented to severe accident numerical codes such as ICARE, SCDAP/RELAP, MELCOR but improved in following aspects: • new approach to evaluation of view factors and mean beam length; • detailed evaluation of gas absorptivity and emissivity; • account of effective radiative thermal conductivity for the large core; • account of geometry modification in the course of severe accident. Special attention is paid to deriving of exact analytical values of view factors and mean beam lengths (which are a good tool in radiative heat transfer concerning gas media) for a number of “standard” geometries. Generalized Hottel’s method of strings is used for rods of finite lengths. Monte-Carlo method is used for validation of new model in application to “standard” geometries. The developed model is successfully applied for modeling of PARAMETER-SF1 and QUENCH-06 tests, which use the triangular and square rod assembly respectively.
A Model-Independent Technique for Eigenvalue Identification and Its Application in Predicting Cardiac Alternans
Authors: Zhao Xiaopeng , Schaeffer David G. , Krassowska Wanda , Gauthier Daniel J.
Published: May 2009

Predicting cardiac alternans is a crucial step toward detection and prevention of ventricular fibrillation, a heart rhythm disorder that kills hundreds of thousands of people in the US each year. According to the theory of dynamical systems, cardiac alternans is mediated by a period-doubling bifurcation, which is associated with variations in a characteristic eigenvalue. Thus, knowing the eigenvalues would allow one to predict the onset of alternans. The existing criteria for alternans either adopt unrealistically simple assumptions and thus produce erroneous predictions or rely on complicated intrinsic functions, which are not possible to measure experimentally. In this work, we present a model-independent technique to estimate a system’s eigenvalues without requirements on the knowledge of the underlying dynamic model. The method is based on principal components analysis of a pseudo-state space; therefore, it allows one to compute the dominant eigenvalues of a system using the time history of a single measurable variable, e.g. the transmembrane voltage or the intracellular calcium concentration in cardiac experiments. Numerical examples based on a cardiac model verify the accuracy of the method. Thus, the technique provides a promising tool for predicting alternans in real-time experiments.
Mixing Enhancement in Two-Component Microchannel Flow: Geometric and Pulsed Flow Effects
Authors: Bhopte Siddharth , Sammakia Bahgat , Murray Bruce
Published: May 2009

The ability to control mixing of reagents in MEMS systems is crucial for many biological and chemical analysis applications. However mixing in these microfluidic devices is a challenge because the flows are laminar corresponding to very low Reynolds number. Recent numerical and experimental research studies have investigated the effect of microchannel geometries and time pulsing on mixing enhancement. In this paper, mixing of two aqueous reagents is studied in a “T” shaped microchannel by means of computational fluid dynamics (CFD). The baseline microchannel geometry has three branches: two inlets and one outlet. All the branches are 200 μm wide and 120 μm deep, which is a typical scale for mass produced disposable devices. A simple geometric modification to the baseline case is made by splitting one of the inlets in half such that the net flow rate at the outlet remains same as the baseline case. The two split inlets impinge the microchannel lateral flow from opposite directions. Significant improvement in mixing using the two-way split flow modification is predicted from the modeling. Previous studies have also shown that by adding well -shaped cavities or grooves in microchannels enhance mixing, so well-shaped cavities are added at the two split inlets. Considerable improvement over the two-way split flow model is seen by adding well-shaped cavities at the split inlets. Three geometries have been systematically studied for both constant and time dependent flows.
Thin Filament Pyrometry Temperature Measurements in Microgravity Droplet Combustion
Authors: Yozgatligil A. , Park S. H. , Choi M. Y.
Published: May 2009

Thin filament pyrometry (TFP) temperature measurement technique was implemented for the first time in microgravity ethanol droplet combustion experiments at NASA 2.2s drop tower. This technique was first developed by Vilimpoc and Goss [1] and later used by several researchers in both diffusion and premixed flames [2–4]. The advantages of this technique are related to rapid temporal response and spatially-resolved temperature distribution rather than single point measurements (as in the case with thermocouples). The SiC filament is an ideal material as a temperature probe in a flame due to its low thermal conductivity, high resistance to oxidation and its small size. TFP was implemented in microgravity droplet combustion experiments at NASA 2.2s drop tower. An 8 bit CCD camera was used to record the emission from the SiC fiber that was positioned through the center of the droplet (the fiber is also used to suspend the droplet and keep it in the field view of the camera). The camera is equipped with a lens and a 700 nm interference filter, with a FWHM of 25 nm was placed in front of the camera. Neutral density filters were used in order to obtain unsaturated filament images for the various experimental conditions (oxygen concentration, inert, pressure). A 300 nm plano convex lens was placed in front of the droplet flame in order to improve spatial resolution by magnifying the image. The emission measured by the camera along the location of the filament results from the emission from the filament and the flame in the intervening region between the filament and the camera. Figure 1 displays a schematic from the top of the flame and shows the rays from filament towards the camera and the rays from the medium (gas/soot) in front of the filament towards the camera).
Modeling Head Motion During Explosive Events to Assess Brain Injury Severity in a Battlefield Environment
Authors: Connolly Thomas J. M. , Clutter J. Keith
Published: May 2009

The occurrence of blast induced brain injury in individuals serving in Iraq and Afghanistan is dramatically higher than in past conflicts. This has been attributed in part to the prevalence of roadside improvised explosive devices, or IEDs. There is a call from the military medical community to reduce the reliance on victim self-reporting as the primary diagnosis technique to determine the likelihood of brain injury after a blast. This study demonstrates the utility of computational modeling in establishing clear criteria that denotes the probability of cerebral contusion and, thus, brain injury. Computational fluid dynamics (CFD) is used to establish the environment from a full range of threats. This is combined with bond graph modeling of varying levels of fidelity to estimate the dynamics of the skull and brain. Results clearly show that a boundary exists in the threat parameter space that determines whether brain injury occurs.
Estimation of Spatial Temperature Distribution in Co-Flow Planar Solid Oxide Fuel Cells
Authors: Xi Handa , Sun Jing , Chen Jian
Published: May 2009

Significant temperature distribution has been identified in planar Solid Oxide Fuel Cells (SOFCs) during both steady state and transient operations. In order to ensure the material stability and device protection, the maximum temperature and temperature gradient have to be closely monitored and securely maintained below certain limits. In practical implementation, however, direct measurement of the temperature distribution inside the SOFC is difficult and costly. In this paper, an observer is designed and the corresponding performance is analyzed for estimating the temperature distribution in the co-flow planar SOFC. To facilitate the observer design, we introduce a reduced-order nonlinear SOFC model that is obtained based on the high-order detailed model derived in our previous work. Using three easily accessible measurements, namely the stack voltage and the temperatures of the solid structure at the entrance and exit of the SOFC, the observer designed based on the low order model can effectively estimate the temperature profile during both steady-state and transient operations. Model-based analysis and simulation results are presented to demonstrate the performance of the estimation scheme and to provide design guidelines.
Recommendations for Recycling, Processing and Reuse of Concrete
Authors: El Dalati Rouba , Matar Pierre , Youssef Emile , Yotte Sylvie , Homsi Farah , Haykal Saiid
Published: May 2009

Some countries started to recycle concrete materials for reuse in structural or other issues. Some of them, like Germany, Australia and Canada have established their own recommendation guide for recycling concrete [1,2]. The recycling consists of crushing old concrete into aggregates, and then processing it into new mixture using recycled aggregates with specified sizes [3,4]. The aim of this recycling is to save nature from deforestation and dryness, by reducing the need to gravel and so the quarries work, and also to economize the waste management [5,6]. The present research work consists of an experimental study assessing the impact of using recycled aggregates on the concrete behavior and on the country’s economy. We are especially interested in determining the best composition for the new mixture of concrete resulting from reusing different types of recycled aggregates. Different types of tests have been done depending on the aggregates sizes, their origin and their state (burned or safe). The analysis is based on the comparison between compressive strength, water-cement ratio, slump, porosity and durability. Otherwise, the impact on economy is analyzed, a priori, by studying the effect of reducing the cost of the resulting concrete on construction spending. The resulted recommendations indicate the sizes of aggregates which may constitute the best composition for recycling and processing concrete, and the best use for each type of concrete depending on behavior and economy effect.
Analysis of Water Mains Failure Frequencies: Artificial Neural Networks Versus Poisson Regression, Case Study — Sanandaj-Iran
Authors: Asnaashari Ahmad , Shahrour Isam
Published: May 2009

This paper includes analysis of water mains failure in Sanandaj city (in Iran) using both the artificial neural networks and the Poisson regression. This issue constitutes a major challenge in Iranian water authorities for its environmental consequences and associated direct and indirect costs such as the lost of purified water and the social impacts. According to 10-years collected data in Sanandaj city, an artificial neural networks model is proposed for the prediction of failure in water mains network; the performances of this model are then compared to the conventional Poisson regression. The input indicators include pipe material, size, age, thickness, length, depth, traffic category, maximum daily pressure and pervious failure events. Analyses show that both the artificial neural networks and the Poisson regression methods can be used for predicting and evolution of the water mains network. However, the former method showed better performances than the latter.
Development of Wet Wire Drawing Machine and Pass Schedule With Ultra High Speed for High Carbon Steel Wire
Authors: Lee S. K. , Kim B. M. , Ko W. S.
Published: May 2009

High speed wet wire drawing has become very common for the production of fine high-carbon steel wire (up to 0.70wt%C) because of the increase in customer demand and production rates in real industrial fields. Although the wet wire drawing process is performed at a high speed usually above 1000m/min, greater speed is required to improve productivity. However, in the high-carbon steel wire drawing process, the wire temperature rises greatly as the drawing speed increases. The excessive temperature rise makes the wire more brittle and finally leads to wire breakage. Therefore, the control of wire temperature is very important. In this study, the variations in wire temperature during the high speed wet wire drawing process were investigated. A multi-stage wet wire drawing process with 21 passes, which is used to produce steel wire, was redesigned by considering the increase in temperature. In order to apply the redesigned pass, a new wet wire drawing machine was developed. Through a wet wire drawing experiment with the new drawing machine and the redesigned pass, it was possible to increase the maximum final drawing speed to 2000m/min without the deterioration of the qualities of drawn wire.
Design Optimization and Efficiency Modeling of a Hot Gas Vane Motor
Authors: Bommarito Gregory E. , Fales Roger
Published: May 2009

The purpose of this work is to model and analyze the dynamics of a hot gas vane motor for later design optimization work. The pneumatic motor is a portable direct drive actuator that is intended as an alternative to battery-powered electromagnetic motors. It is believed that the vane motor could eventually replace other solution for portable power generation. An optimal design of the motor is desirable to maximize portability and efficiency. Modeling the device will make it possible to optimize the mechanical efficiency by altering the geometry of the motor’s vanes and respective chambers. While the efficiency of the motor is affected to a great extent by its geometry, losses from leakage and friction will also be considered. For the device to remain portable, there are limitations on the size of the final design which will restrict the optimal efficiency of the vane motor.
Thermal Wake of a Single Rising Air Bubble in a Large Body of Stagnant Liquid
Authors: Molki Majid , Abbasi Bahman
Published: May 2009

A computational effort was undertaken to study the thermal field behind a slowly rising solitary air bubble. Starting from rest, the bubble moves upward in water due to buoyancy force in the gravitational field and induces both internal and external motion. The bubble, being colder than the surrounding water, is heated by water. The upward motion deforms the shape of the bubble and generates a convective heat transfer process. Variation of temperature at the gas-liquid interface causes a local variation of surface tension. Although the problems of this type have been generally treated by the axisymmetric assumption, the present work employs a three-dimensional model that captures the azimuthal variation of flow parameters. High-speed photography was employed to visualize the bubble evolution from the onset until the bubble reached a certain velocity. The computations were performed using the finite-volume and Volume of Fluid (VOF) techniques. The shape and evolution of the bubble as predicted by the computations are compared with those captured on the high-speed photographs. The computations revealed details of the pressure and temperature fields inside and outside the bubble. They also indicated the thermal field in the wake region behind the bubble.
Heat Transfer Characteristics of Suspension Flow Inside a Microchannel
Authors: Khiabani Reza H. , Joshi Yogendra , Aidun Cyrus
Published: May 2009

This paper presents computational results on the effect of suspended cylindrical solid particles in channel flow on the rate of heat transfer. The results provide insight into the effect of suspended solid particles on the rate of heat transfer. The computational method is based on the solution of the lattice-Boltzmann equation for the fluid flow, coupled with the energy equation for thermal transport and the Newtonian dynamics equations for direct simulation of suspended particle transport. The effects of Reynolds number, particle-to-channel size ratio and the eccentricity of the particle on heat transfer from the channel walls for single and multiparticles are presented. The multiparticle flow condition represents a case with solid particles suspended in the cooling medium, such as in micro/nanofluids, to augment heat transfer. The results provide insight into the mechanism by which suspended particles can effectively change the rate of heat transfer in a microchannel.
Fluid Flow and Heat Transfer in a Curved Square Duct Using Lattice Boltzmann Method (LBM)
Authors: Liao Quan , Jen Tien-Chien
Published: May 2009

In this paper, the 3DQ27 model of Lattice Boltzmann Method (LBM) is employed to simulate the fully-developed fluid flow and heat transfer in a curved square duct with curvature ratio (0.02–0.5) and Dean Number (0 – 200). The Dean instability in the curved square duct is fully investigated and a stability diagram is obtained with the parameters of curvature ratio and Dean number. It is found that for the square duct with high curvature ratio (i.e. curvature ratio is greater than 0.2) the onset of transition from single vortex pair to double vortex pairs depends on the Dean number and curvature ratio, while at the small curvature (i.e. curvature ratio is smaller than 0.1) the onset can be characterized by the Dean number alone. This is consistent with the results obtained from the conventional Computational Fluid Dynamic (CFD) method and experimental data. For the friction coefficient and Nusselt number, which are the functions of Dean number and curvature ratio, it was found that the present numerical results are in good agreement with the available experimental data and conventional CFD results within the given parameters range in this paper.
Gas Metal Arc Welding (GMAW) Process Optimization for Uncoated Dual Phase 600 Material Combination With Aluminized Coated and Uncoated Boron Steels for Automotive Body Structural Applications
Authors: Koganti Ramakrishna , Angotti Sergio , Joaquin Armando , Jiang Cindy , Karas Chris
Published: May 2009

With the increasing demand for safety, energy saving and emission reduction, Advanced High Strength Steels (AHSS) have become very attractive steels for automobile makers. The usage of AHSS steels is projected to grow significantly in the next 5–10 years as new safety and fuel economy regulations are enacted. These new steels pose significant manufacturing challenges, particularly for welding and stamping. Welding of AHSS remains one of the technical challenges in the successful application of AHSS in automobile structures, especially when durability of the welded structures is required. In this paper, Gas Metal Arc Welding (GMAW) of uncoated DP 600 and boron (coated and uncoated boron) steels were investigated. In the first study, 2.0 mm DP 600 and 2.0 mm uncoated boron lap joints (Joint #1 and #2) were investigated. In the second study, 1.00 mm DP 600 and 2.0 mm USIBOR (aluminized coated boron) lap joints (Joint # 3 and #4) were investigated. Static and fatigue tests were conducted on the four joint configurations. The effects of steel stack-ups and microhardness distribution along the tensile stress flow direction of the joints on fatigue performance defined by fatigue life as well as crack initiation site and propagation path were analyzed. Metallurgical properties of the dissimilar metal lap joints were evaluated using optical microscopy. The boron steel shows a significant drop in hardness at the heat affected zone (HAZ) as compared to the DP600 steel side. It was found that for the 2.0 mm DP600 and 2.0 mm boron steel dissimilar joint, fatigue life of the joint is better when boron steel was on the top of the joint (Joint #2). However, in the case of 1.0 mm DP 600 and 2.0 mm USIBOR lap joint, the fatigue life of the joint is better when 1.0 mm DP 600 was on the top of the joint (Joint # 3). Ductility of boron steel and significant HAZ softening in boron steel are believed to be the key factors for the fatigue failure at the boron steel side (in all four joint configurations).
Performance and Degradation Effects of Anode-Supported Cells With LSM and LSCF Cathodes
Authors: Lanzini A. , Leone P. , Santarelli M. , Asinari P. , Cali` M.
Published: May 2009

The performance of solid oxide fuel cells is affected by various polarization losses, usually grouped in ohmic, activation and concentration polarization. Under typical operating conditions, these polarization losses are largely dependent on cell materials, electrode microstructures, and cell geometry: as an example, the performance of a tubular cell is strongly limited by the ohmic polarization due to the long current path of electrons, while in a planar cell each of these losses has a comparable effect. It is therefore of interest, in case of planar geometry, to investigate the performance limiting factors. In this paper, a performance evaluation of planar circular-shaped seal-less SOFC cells from InDEC® was performed, with an outline of the limiting factors at reduced temperature. Two different designs of planar cells are considered: both have porous NiO-YSZ anode as mechanical support, NiO-YSZ anode active layer, yttria-stabilized zirconia (YSZ) electrolyte, and only differ for the cathode design: (1) strontium doped lanthanum manganate (LSM)-YSZ cathode functional layer (CFL) and LSM cathode current collector layer (CCCL); (2) yttria doped ceria (YDC) blocking layer and lanthanum strontium cobalt ferrite oxide (LSCF) functional layer. The characterization was performed by taking V-I measurements over a range of temperatures between 650°C and 840°C with hydrogen as fuel, and air as oxidant. The dependence of the cell performance on the various polarization contributions was rationalized on the basis of a analytical model, through a parameter estimation on the experimental data, devoted to the determination of the temperature dependence of the area specific resistance (ASR) and of the cathode exchange current density: in particular, the performance limitation at low temperature is due to activation polarization for ASC1 and ohmic polarization for ASC2. Based on the results of the investigation, it is concluded that LSCF cathodes are really effective for decreasing the cathode activation polarization, allowing the reduction of operating temperature. Finally, a microstructural analysis with SEM and optical microscopy has been performed on the ASC2 cell after the polarization testing. The aim of this investigation was in particular to evaluate the degradation phenomena occurring in the anodic structure and over the interfaces between the various active layers. The ASC2 elastic modulus has also been estimated before and after polarization testing in order to evaluate the decreasing of the mechanical strength of the cell after a complete thermal cycle. The results describe a mechanical degradation of the structure and of the distribution of the phases.
Gas Metal Arc Welded (GMAW) Joint Strength Comparison of Aluminum Sheet (5754) and Exturded (6063) Alloys
Authors: Koganti Ramakrishna , Joaquin Armando , Zaluzec Matthew , Karas Chris
Published: May 2009

The development of lightweight vehicles, in particular aluminum intensive vehicles, require significant manufacturing process development for joining and assembling aluminum structures. Currently, 5xxx and 6xxx aluminum alloys are being used in various structural applications in a number of lightweight vehicles worldwide. Various joining methods, such as GMAW (it is also referred as Metal Inert Gas Welding), Laser and adhesive bonding have been investigated as technology enablers for high volume joining of 5xxx, and 6xxx series alloys. In this study, GMA welding was used to join 5754 non-heat-treatable alloy sheet and 6063-T6 heat treatable extrusion products. The objective of this study was to develop optimum weld process parameters for non-heat-treatable 5754 aluminum and heat treatble 6063-T6 alloys. For both the alloys, the lap joint configuration was used. The GMA welding equipment used in this study was an OTC/Daihen CPD-350 welding systems and DR-4000 pulse power supply. In the first phase of the experiments for 5754 aluminum alloy, the factors selected for the experiment were power input (torch speed, voltage, current, wire feed), pulse frequency, gas flow rate and surface condition. A full factorial design of experiment (DOE) was conducted (DOE #1) to understand the main and interaction effects on lap joint failure and weld penetration. Based on the results from phase 1 results, surface condition was eliminated in the phase 2 experiments. In phase 2 experiments for heat treatable alloys 6063 T6, the factors selected were power input (torch speed, voltage, current, wire feed), pulse frequency, gas flow rate, torch angle, and arc intensity. A partial factorial DOE was conducted (DOE # 2) primarily to understand the main effects and some two level interaction effects. For both phase 1 (non-heat treatable alloy 5754) and phase 2 (heat treatable alloy 6063-T6) experiments, the factors influence on the mechanical properties of the lap joint, metallurgy (weld penetration) and micro hardness were evaluated. Post weld analysis indicates for non heat treatable alloy 5754, power input and gas flow rate are the two signficant factors (statistically) based on lap shear load to failure and weld penentration data. For heat treatable alloy 6063, power input was the significant factor on joint load to failure, however, for weld penetration, power input, pulse frequency and gas flow rate were the significant factors. Based on the joint strength and weld penetration, optimum weld process factors were determined for both non-heat treatable alloy 5754 and heat treatble alloy 6063 T6.
Acquiring Torque and Rotational Speed Data From a Stationary Bicycle for Undergraduate Teaching
Authors: Calhoun Sean A. , Diwanji Bhumil , Panicker Philip K. , Lu Frank K.
Published: May 2009

A laboratory module was recently developed for an introductory experimental course for sophomore mechanical and aerospace engineering students. The goal of this laboratory is to provide the students with an understanding of digital data acquisition systems for measuring torque and angular velocity in real time. The laboratory comprises of a stationary exercise bicycle, adapted to house a torquemeter on its front axle, an optical tachometer, the data acquisition system and software which converts a computer into a virtual instrument. A group of two or three students is rotated through the laboratory as part of a larger number of laboratory modules. The students access the experiment via the virtual instrument. The experiment requires a student to ride the bicycle. The data acquired are then subsequently analyzed by the students who are required to write individual laboratory reports.
Studies on Blood Rheology in a Coronary Artery Using CFD Technique With an AE Sensor
Authors: Kim Yong Hyun , Chungag Goddy , Lee Joon Sang , Ayorinde Emmanuel , Wu Xin
Published: May 2009

There still exists a need for developing more accurate generalized models for multiscale biofluids systems that enable clearer understanding of normal microcirculation and complexities of disease hemorheology. Such work will yield enhanced computational and experimental techniques for a wider class of flows having fluid-solid interactions, complex moving boundaries, and involving red blood cell (RBC) aggregation under physiological conditions. The work reported here has involved the multiphase non-Newtonian fluid simulations of pulsatile flow in an idealized coronary artery model have been performed using numerical and experimental studies. The secondary flow affected a local RBC accumulation on the inside curvature and it changed the local flow characteristics as well. RBC viscosity and wall shear stress (WSS) were changed with a function of local hemotocrit. In practical work involving specialized velocity measurement and acoustic emission monitoring of flow characteristics, flow-induced vibration effects, as well as material and physiological aspects of arterial systems were conducted. Computations of arterial flows were made and experimental investigations using glass microtube simulations of arteries were carried out. This work contributes to an understanding of the mechanics of relationship between the progression of certain inherited diseases and the mechanical deformation characteristics of the arterial system and the RBC.
Modeling of an Ultrasonic Communication System
Authors: Roa-Prada S. , Scarton H. A. , Saulnier G. J. , Shoudy D. A. , Ashdown J. D. , Das P. K. , Gavens A. J.
Published: May 2009

This paper discusses the use of ultrasound to convey data from one side of a metallic wall to the other side. A communication channel is established by attaching a set of three ultrasonic transducers to the wall. The first transducer injects a continuous ultrasonic wave into the wall. The second transducer is mounted on the inside and operates as a receiver and signal modulator. The third transducer is installed on the same side as the first transducer and receives the signal that is reflected from the inside transducer. A sensor on the inside provides analog data that is then digitized. The digitized bits are used to vary the electrical load applied to the electrical terminals of the inside transducer, changing its acoustic impedance in accordance with the data bits. The impedance changes, in turn, modulate the amplitude of the reflected ultrasonic signal. This modulated signal is detected at the outside receiving transducer, where it is then demodulated to recover the data. Additionally, some of the acoustic power received at the inside transducer is harvested to produce the electrical power needed to operate the communication and sensor system on the inside. The entire system (ultrasonic, solid wall, and electronic) is modeled in the electrical domain through electro-mechanical analogies. This approach enables the simultaneous examination of the ultrasonic and electronic components. The electric circuit simulation package PSpice is used to simulate the communication system, which assisted in the analysis and optimization of the communication channel. Both simulation and experimental results are presented and discussed.
Experimental Study of Single-Bubble Dynamics in Isothermal Liquid Pools: Effects of Fluid Properties, Orifice Diameter and Flow Rate
Authors: Subramani A. , Jog M. A. , Manglik R. M.
Published: May 2009

The dynamics of a single bubble as it grows at and eventually detaches from the tip of submerged capillary orifices in isothermal pools of pure liquids of varying fluid properties is studied experimentally. The transient interfacial behavior around the evolving isolated bubble (from inception through growth, necking, and detachment) is mapped by means of optical micro-scale flow visualization that uses a high-speed high-resolution digital camera and image processing system. Parametric effects of capillary orifice diameter (do = 0.32, 1.0, and 1.76 mm), air flow rate (2 ≤ Q˙ ≤ 20 ml/min), and liquid properties (surface tension and viscosity), on the bubbling signature (growth time, departure diameter, and bubble interval) are explored and highlighted. It is found that bubble evolution, in a first order scaling, can be correlated by a balance of forces due to buoyancy, viscosity, surface tension, liquid inertia, and gas momentum transport at the transient gas-liquid interface.
Exploratory Experiments on Machined Riblets for 2-D Compressor Blades
Authors: Oehlert Karsten , Seume Joerg R. , Siegel Frank , Ostendorf Andreas , Wang Bo , Denkena Berend , Vynnyk Taras , Reithmeier Eduard , Hage Wolfram , Knobloch Karsten , Meyer Robert
Published: May 2009

During the last decades, riblets have shown a potential for viscous drag reduction. Several investigations and measurements of skin-friction in the boundary layer over flat plates and on turbomachinery type blades with ideal riblet geometry have been reported in the literature. The purpose of the present study is to investigate whether laser machined and ground riblet-like structures could be successfully employed on conventional 2-D (NACA) compressor blades in order to assess the potential of industrial machining processes for the creation of the riblet effect. Perfectly trapezoid riblets were designed specifically for the flow parameters in the wind tunnel. Parameters describing the geometry and the deviation from ideal riblets are developed. Riblet machining by high precision material ablation has the potential of achieving micro-machining quality. In comparison to ns-laser processing using either Q-switched solid-state lasers or excimer lasers, the results for high precision material ablation show the enormous potential of ps-laser radiation and achieve the required quality, free of thermally induced defects and, consequently, with high reproducibility. For grinding riblets, geometrically defined microprofiles must firstly be generated via a profile dressing process and then ground onto the work piece surface. A precise adjustment of the grinding wheel system (grit, bonding) and the dressing/grinding conditions is necessary, in order to satisfy the opposing requirements at both dressing and grinding. The blade specimens were geometrically measured with a confocal microscope as well as secondary electron microscope using a specially developed riblet-oriented analysis. For verifying the measurement results, an Atomic Force Microscope was used. The specimens, i.e. flat plates and compressor blades, are aerodynamically tested in a cascade wind tunnel and properly scaled model surfaces were tested in an oil channel in order to quantify skin-friction reduction. Wake measurements of a cascade with NACA-profiles which have the resulting riblet-like structured surface show that the laser shaped as well as ground riblets reduce skin-friction almost as well as the ideal ones, which means a skin friction reduction of up to 7%.
The Effect of Nanoparticles on the Thermal Conductivity of Crystalline Thin Films at Low Temperatures
Authors: Katika Kamal M. , Pilon Laurent
Published: May 2009

This study is concerned with the prediction of the effective thermal conductivity of nanocomposite thin films consisting of nanoparticles randomly distributed in a solid matrix. Crystalline sodium chloride with embedded monodisperse silver nanoparticles is investigated as a case study for thin films where phonons are the main heat carriers. To the best of our knowledge, the equation for phonon radiative transfer is solved for the first time with an exact scattering transport cross-section of the nanoparticles as a function of frequency which was obtained from the literature. The one-dimensional equation for phonon radiative transfer based on the isotropic scaling approximation is solved on a spectral basis using the discrete ordinates method to predict the temperature profile and the heat flux across the nanocomposite thin films. The thermal conductivity is retrieved at temperatures where the effects of Umklapp and Normal processes can be neglected and scattering by the particles on phonon transport dominates. The method of solution and closure laws were validated with experimental data of thermal conductivity for bulk samples at 2.53, 5.94, and 10.56 K. The effects of the film thickness (1 μm to 2.5 cm), nanoparticle diameter (5 nm to 100 nm) and volume fraction (0.0001 to 0.2) on the thermal conductivity of the nanocomposite thin film are investigated. The results indicate that the thermal conductivity decreases with decreasing particle radius as well as with increasing particle concentration. Finally, a dimensionless analysis revealed a power law relationship between the dimensionless thermal conductivity and a dimensionless length of the order of the acoustic thickness of the medium. These results can be used to design nanocomposite thin films for various low temperature thermal applications by choosing optimal nanoparticle radius and volume fraction, and film thickness.
Frequency Response Identification and Dynamic Modeling of a Magnetic Levitation Device
Authors: Shameli Ehsan , Khamesee Mir Behrad , Huissoon Jan Paul
Published: May 2009

Magnetic levitation is an emerging technology in applications such as MEMS production, high speed transportation and biomechanics. Due to the lack of mechanical contact, magnetically levitated devices are unimpeded by problems caused by friction, lubrication and sealing. This paper presents a dynamic model of a magnetic levitation device through the frequency response identification technique. Experimental results verify that the proposed model reasonably matches the actual system’s behavior. The magnetic levitator consists of a set of modules comprising the electromagnets, an iron yoke, a power amplifier, laser position sensors, and a controller. In order to obtain the total transfer function of the system, the dynamic model of each of these modules was obtained individually. The routine presented in this work is remarkable as it leads to the model of a highly nonlinear system through a modular approach that can be applied to a variety of systems.
Abrasive Waterjet Peening With Elastic Prestress: Subsurface Residual Stress Distribution
Authors: Sadasivam Balaji , Hizal Alpay , Arola Dwayne
Published: May 2009

Recent advances in abrasive waterjet (AWJ) technology have resulted in new processes for surface treatment that are capable of introducing compressive residual stresses with simultaneous changes in the surface texture. While the surface residual stress resulting from AWJ peening has been examined, the subsurface residual stress field resulting from this process has not been evaluated. In the present investigation, the subsurface residual stress distribution resulting from AWJ peening of Ti6Al4V and ASTM A228 steel were studied. Treatments were conducted with the targets subjected to an elastic prestress ranging from 0 to 75% of the substrate yield strength. The surface residual stress ranged from 680 to 1487 MPa for Ti6Al4V and 720 to 1554 MPa for ASTM A228 steel; the depth ranged from 265 to 370 μm for Ti6Al4V and 550 to 680 μm for ASTM A228 steel. Results showed that elastic prestress may be used to increase the surface residual stress in AWJ peened components by up to 100%.
Innovative Structural and Joining Concepts for Lightweight Design of a Scaled Model of a Heavy Vehicle System
Authors: William Gergis W. , Shoukry Samir N. , Prucz Jacky C. , Evans Thomas H.
Published: May 2009

The research work presented in this paper aims at investigating the benefits and practicality of implementing lightweight composite materials and design concepts in heavy trailer systems. The overall purpose is to devise innovative, lightweight design and joining concepts for heavy vehicle structures. A 1 to 4 scaled model representation of a trailer was built to assess the feasibility of creating a trailer from fiber-reinforced polymer (FRP) composite materials and therefore using innovative bonding methods to join the design parts. This portion of work focused on using the process of designing and fabricating the model to have first hand knowledge and experience on possible bonding methods and the types of materials and structures that will optimize strength and weight saving characteristics. Current trailer configurations were studied and shown to have high weight sources in the flooring structure. The process of analyzing innovative bonding methods and the implementation of composite sandwich technology created an alternative lightweight structure to replace heavy flooring constituents of trailer hauls. Finite element modeling and experimental analysis reveal that sandwich technology with a core structure that adds flexural stiffness to the overall design and is aided by an FRP faceplate that geometrically matches the core structure provides solutions to decrease heavy vehicle system weight.
Application of Electromagnetic Force in Laser Welding
Authors: Zhou J. , Tsai H. L.
Published: May 2009

In recent years, lasers have been widely used in the welding processes for automotive, aerospace, electrical and heavy manufacturing industries due to their high power density, small heat-affected zone and high productivity. Especially, with high depth-to-width ratio and high welding efficiency, keyhole-mode laser welding is more promising compared to the conventional welding processes. However, a number of defects, such as porosity, irregular beads, undercut and humping are frequently observed in laser welds, which deteriorates the strength and quality of the welded parts. In current study, an externally controllable electromagnetic force is introduced into the laser welding process to prevent porosity formation and to control weld bead shape. Numerical models are developed to study the transport phenomena in laser welding and to accurately calculate the current density and magnetic flux fields and the resulting electromagnetic forces in three-dimensional weldments. Effects of the electromagnetic force on metal flow, heat and mass transfer and weld bead shape are investigated. The continuum model is used to handle the entire domain including solid phase, liquid phase and mush zone. The enthalpy method is employed to handle the absorption and release of latent heat during melting and solidification. Inverse Bremsstrahlung (IB) absorption, Fresnel absorption and multiple reflections of laser beam energy at the keyhole walls are considered for the study of laser-plasma interaction. Volume of Fluid (VOF) technique is adopted to calculate the free surface evolution in the computation. As indicated by this study, porosity-free laser welds with desired bead shapes can be achieved with appropriate applications of electromagnetic forces.