bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiscale Modeling of Fluid Turbulence and Flocculation in Industrial Applications
Authors: Jafari Arezou , Henttinen Krista , Zamankhan Piroz
Published: April 2008

The present effort is the development of a multiscale modeling, simulation methodology for investigating complex phenomena arising from flowing fiber suspensions. Here, a mathematically rigorous, multiscale modeling methodology is presented capable of coupling behaviors from the Kolmogrov turbulence scale through the full scale system in which a fiber suspension is flowing, (i) a computational simulation framework built around this methodology into which techniques for investigating behaviors at the various scales can be effectively integrated, and (ii) a proof of concept of the developed core technologies using synergetic interactions with experimental studies. Here the key aspect is adaptive hierarchical modeling. Numerical results are presented for which focus is on fiber floc formation and destruction by hydrodynamic forces in turbulent flows. Specific consideration was given to moleculardynamic-type simulations of viscoelastic fibers in which the fluid flow is predicted by a method which is a hybrid between Direct Numerical Simulations (DNS) and Large Eddy Simulation techniques (LES) and fluid fibrous structure interactions (FSI) will be taken into account. The present results may elucidate the physics behind the break up of a fiber floc, opening the possibility for developing a meaningful numerical model of the fiber flow at the continuum level where an Eulerian multi-phase flow model can be developed for industrial use.
Efficient Concept of Low Energy Building
Authors: Hassan Mahmoud A.
Published: April 2008

Low energy architect is a major target of building researchers and designers worldwide. Obviously, any portion of energy that can be saved in this respect can be directed to industrial processes, if any. Building energy consumption can be reduced through various systems such as air conditioning (a major building energy consumer), lighting, equipment, etc. In regions where energy is limited or scarce, air conditioning would have to be replaced by natural ventilation for the removal of the building heat load for thermal comfort. Also, energy conservation issues are being more important in hot arid regions, especially because the building are consuming more than 60% of electric energy generated and about 65% of this energy is consumed for cooling. There is a set of complex factors, which determine energy needs in building, such as solar radiation, type of A/C systems, building operation, thermal properties of the building envelop... etc. In the present decade the aim is to discuss the advantage of energy efficient building design. There is several ways to reduce the energy consumed for the human comfort process, but what is the most energy efficient or more energy saving from these ways. One of these is the insulation, which can be used for insulating the wall and the roof, which subjected to the large amount of the solar heat gain. The insulation of the roof is intended to maximize resident’s thermal comfort and minimize energy consumption of housing. The parameters, which are effect on the thermal performance of the roof, are the color, general construction, insulation and ventilation. This paper present the effect of insulation of the roof on the amount of energy consumed for different types of insulation in order to select the suitable insulation which give the minimum cost and maximum energy saving. This work was done using an energy software program (Visual DOE). This paper provided suggestions to improve the building construction for the thermal comfort. A parametric analysis was investigated for the economic analysis of various insulating building materials.
The Effects of Hole Size and Eccentricity on the Reliability of Notched Laminates
Authors: Ganesan R. , Ibrahim Md.
Published: April 2008

Most of the practical engineering structures contain holes and cutouts of different sizes designed as parts of basic design, as in joints and assemblies, and for maintenance purposes. It is well known that holes and cutouts cause serious problems of stress concentrations due to the geometry discontinuity. These problems are even more serious in structures made of composite materials since the materials exhibit anisotropic behavior, and the structures are more sensitive to stress concentrations due to their brittle behavior. Because of its importance, engineers want to determine the effects of stress concentration, predict the failure and strength, and develop methods to reduce these effects. The stress distribution in the notched composite laminate is very sensitive to the size of the hole and the eccentricity of the hole from its desired location. In practice, many times during manufacturing the drilled hole is slightly offset from the desired location, and further there is variability in the size of the hole. These variations have a random distribution over the ensemble of laminates. In addition, composite materials display significant variability in their mechanical properties. As a result of the above-mentioned variabilities, the stress distribution in the laminate becomes stochastic in nature. In this circumstance, it becomes appropriate that the analysis of the notched laminates be carried out based on a stochastic approach and that the design is performed based on reliability requirement.
Laser Digitizer/Stereo Vision Methods for Simultaneous Measurement/Analysis of Sheet Metal Forming Strain/Geometry
Authors: Chan H.-L. , Mitchell J. P. , Spence A. D. , Sklad M. P. , Capson D. W.
Published: April 2008

Conventionally, strain has been measured using scribed, etched, or printed grids together with a ruler and dividers or a graduated, transparent Mylar® overlay. Touch trigger probe equipped Coordinate Measuring Machines (CMMs) are used to measure geometry. More recently, stereo computer vision has been proposed, but, because accuracy quickly diminishes with camera distance to the part, application has been limited to small test samples. On CMMs, laser digitizers are growing in use. To date, however, accurate, simultaneous measurement / analysis of both strain and geometry has not been reported. This paper presents two new CMM based research methods that address this. The laser digitizer method uses a circle grid, and the stereo computer vision approach uses a square grid. Parallel computing is used to accelerate computer processing time. A dual thickness tailor welded steel test dome, an aluminum test dome, and a wrinkled double layer truck part illustrate practical application.
Real-Time Vehicle Dynamics Parameter Estimation
Authors: Shin Kwang-Keun
Published: April 2008

Vehicle dynamics parameters such as understeer coefficient are very important factors to determine the stability and dynamic handling behavior of a vehicle. These parameters vary during the lifetime of a vehicle according to different loading, tire pressure/wear or vehicle-to-vehicle variations of suspension characteristics, etc. The parameter deviations from nominal values may cause performance degradation of chassis/vehicle control systems, which is often designed based on the nominal values. Therefore, if the vehicle dynamics parameters can be estimated and monitored in real-time, the performance of chassis/vehicle control systems could be further enhanced. This paper presents a real-time vehicle dynamics parameter estimation method that estimates vehicle understeer coefficient and front/rear cornering compliances. The algorithm is implemented using Simulink, and analyzed, and validated using VehSim, which is a PC windows-based vehicle simulation software for vehicle dynamics controls and integration. The simulation results show that the developed algorithm is well capable of estimating vehicle dynamics parameters of VehSim, and, therefore, is highly feasible for in-vehicle applications.
Fatigue Analysis of Rigid-Flexible PCB for Cellular Phone and Design of Bending Endurance Reliability Tester
Authors: Moon Yang Ho
Published: April 2008

Flexible PCB of cellular phone constructed of flexible Copper Clad Laminate (FCCL) covered with cover-layer is opened electrically under repeated bending due to formation and propagation of fatigue crack in copper. The life of rigid-flexible PCB is estimated using the finite element method and fatigue analysis considering contact condition of assembly process of the rigid-flexible PCB, opening and closing the phone. And rigid-flexible PCB bending endurance tester is designed to test bending reliability without cellular phone. Using rigid-flexible PCB bending endurance tester, bending reliability quality of rigid-flexible PCB can be guaranteed faster than before.
Free Flexural Vibrations Response of Composite Mindlin Plates or Panels With a Centrally Bonded Symmetric Double Lap Joint (or Symmetric Double Doubler Joint)
Authors: Yuceoglu U. , Gu¨vendik O. , O¨zerciyes V.
Published: April 2008

The present study is concerned with the “Free Flexural Vibrations Response of Composite Mindlin Plates or Panels with a Centrally Bonded Symmetric Double Lap Joint (or Symmetric Double Doubler Joint). The plate “adherends” and the plate “doublers” are considered as dissimilar, orthotropic “Mindlin Plates” with the transverse and the rotary moments of inertia. The relatively, very thin adhesive layers are taken into account in terms of their transverse normal and shear stresses. The mid-center of the bonded region of the joint is at the mid-center of the entire system. In order to facilitate the present solution technique, the dynamic equations of the plate “adherends” and the plate “doublers” with those of the adhesive layers are reduced to a set of the “Governing System of First Order ordinary Differential Equations” in terms of the “state vectors” of the problem. This reduced set establishes a “Two-Point Boundary Value Problem” which can be numerically integrated by making use of the “Modified Transfer Matrix Method (MTMM) (with Interpolation Polynomials)”. In the adhesive layers, the “hard” and the “soft” adhesive cases are accounted for. It was found that the adhesive elastic constants drastically influence the mode shapes and their natural frequencies. Also, the numerical results of some parametric studies regarding the effects of the “Position Ratio” and the “Joint Length Ratio” on the natural frequencies for various sets of support conditions are presented.
Performance Analysis of Integrated Active Desiccant Rooftop Air-Conditioning System Operating in Heating Mode
Authors: Petrov Andrei Yu. , Sand James R. , Zaltash Abdolreza , Fischer John , Mitchell Rick , Wetherington G. Randall
Published: April 2008

This investigation describes the performance study of a novel Integrated Active Desiccant-Vapor Compression Hybrid Rooftop (IADR) at Oak Ridge National Laboratory (ORNL) in heating mode. The tests were performed at two different ratios of outdoor/return air. Analysis of performance characteristics under each operating mode, including heating capacity and energy efficiency ratio, are given. Results of defrost cycle are also presented. Comparison between the experimental performance of IADR unit and the calculated performance of other commercially available heat pump systems at comparable operating conditions has been conducted.
Residential Water Heating Dehumidifier (WHD) With Devoted Dehumidification
Authors: Ball Aaron K. , Ferguson Chip W. , Miceli Frank T. , Baskin Evelyn
Published: April 2008

A new a dual-service dehumidifier water heater (WHD) appliance is being researched and developed by the authors. Prior research on a similar appliance, a heat pump water heater (HPWH), has demonstrated the unit’s increased performance and energy saving, and through collaboration, significant progress has been made toward developing the WHD into a potentially marketable product. The primary energy use in residential households is space conditioning (49%), and the second major energy use is hot water consumption. In DOE’s 2004 Buildings Data Book, 15.5 percent of residential energy utilization is consumed by water heating (DOE 2004, Table 1.2.3). The two major types of residential water heaters are direct gas fired (~55%) and electric resistance (~45%) (DOE 2004, Appliance Magazine 2005). The maximum efficiency of a standard electric resistance water heater is 1 (100%), and progress has been made to increase the efficiency of the current standard heaters to approximately 95 percent (DOE 2004, Table 5.10.6), which is roughly the maximum available with today’s technology. However, if the standard system is replaced by a Heat Pump Water Heater (HPWH), the performance can be increased by 140 percent (Zogg and Murphy 2004). The WHD operates as a HPWH while heating water and as a dedicated dehumidifier when water heating is not necessary. This paper presents the general design and laboratory testing results of a WHD. Preliminary performance data reveal coefficient of performances (COP) of approximately 2.2 during water heating. Further, market analysis has revealed that a potential need for this new technology is in regions with high humidity (Ashdown et al. 2004). These regions are primarily in the Northeast, Southeast and some coastal areas of the U.S. Current HPWH units do not have dedicated dehumidification and have a very small share of the residential water heat market. Of the 9.55 million residential water heaters sold in 2003 only about 2,000 of them were HPWHs (DOE 2004, Table 5.10.15).
Study of Micro Ultrasonic Machining of Silicon
Authors: Yu Z. , Hu X. , Rajurkar K. P.
Published: April 2008

As a micro mechanical machining process, micro ultrasonic machining (micro USM) has the major advantage of producing micro-scale components or features in brittle (glass, quartz crystal, and sapphire) and hard (ceramics) materials. Micro USM is used to generate micro holes with 5μm in diameter and 3D micro cavities. However, the relationship of machining parameters such as static load, abrasive particle and amplitude of vibration and the material removal rate is not clearly understood. In this paper, a mathematical model is developed to describe the material removal process in micro USM. Experiments were carried out to verify the model. It was found that the machining speed decreases when the load is over a certain value, which is different from that of theoretical model. To understand this phenomenon, a simple model was proposed to analyze it qualitatively. It was found that the debris accumulation around the crater in a short time is the main reason resulting in the low machining efficiency.
Application of System Modeling to Road Load Data Synthesis for Automobile Product Development
Authors: Hughes Sarah , Jones R. Peter , Burrows Andrew J.
Published: April 2008

A new system-modeling tool has been developed to reduce the need for prototype vehicles for automobile product development by synthesizing Road Load Data. This tool uses MATLAB/Simulink for driver and vehicle control systems and employs a compiled Dymola subsystem within the Simulink environment for the vehicle model itself. This paper describes the design of the tool and its application in the product development process, including an analysis of how the use of system modeling and computer-aided engineering has shortened development time and cut costs. The results presented in this paper show that the methods used in this tool can recreate measured data with an error of less than 13% — this is believed to give greater confidence in the synthesized Road Load Data than other published methods. It is also capable of generating a torque time history for driveline components, and overall load profiles for a number of different vehicle test routes to allow fatigue analysis of those components.
Influence of Two Rows Compound and Simple Angle Holes in Inline and/or Staggered on Film Cooling and Heat Transfer
Authors: Maiteh Bilal Y.
Published: April 2008

This paper describes the results of an experimental investigation into the effect of the mainstream flow history on the film cooling effectiveness and the heat transfer characteristics from the combination of one row of simple angle holes and one row of compound angle holes. The mainstream flow history includes: favorable pressure gradient factors in the range −1.11 × 10−6 to +1.11 × 10−6 and turbulence intensity in the range 0.3% to 4.7%. The presence of favorable pressure gradients in the flow reduces the film cooling protection of the surfaces from both compound angle holes or combination of simple and compound angle holes, while the presence of adverse pressure gradients increases the film cooling effectiveness at low blowing rate and decreases it at high blowing rate. Increasing the turbulence intensity reduces the film cooling effectiveness from compound angle holes or combination of simple and compound angle holes.
Issues Associated With MQL Implementation: Effect on Peripheral Milling Process Performance and Impact on Machining Economics
Authors: Ju C. , Keranen L. P. , Haapala K. R. , Michalek D. J. , Sutherland J. W.
Published: April 2008

The copious use of metal working fluids in machining applications carries with it worker health, environmental, and cost concerns. Driven by these concerns, minimum quantity lubrication (MQL) technology has been proposed as an intermediate alternative between flood and dry machining applications. However, widespread use of MQL is inhibited by worries related to unknown costs, thermal distortions, chip flushing problems, flammability of airborne metal dust, and system reliability/repeatability. More information is needed on the effects of lubricant flow rate and droplet characteristics on the cutting performance. One challenge associated with implementing MQL technology has been the difficulty in reconfiguring dedicated transfer line systems. To address some of the above issues, tests have been conducted to investigate the effects of lubricant flow rate and droplet characteristics on cutting performance in terms of cutting force, workpiece temperature, surface finish, and air quality. Comparisons are made among dry, MQL, and fluid flood applications to show that MQL and flood application provide similar benefit in terms of work temperature. Machining cost analysis for both multistage and single-stage operations provides insight into the relative difference between transfer line and FMS machining systems in terms of costs for different fluid applications.
Sol-Gel Coating Facilitating Si-to-Si Wafer Bonding at Low Temperature
Authors: Wei J. , Deng S. S. , Tan C. M.
Published: April 2008

Silicon-to-silicon wafer bonding by sol-gel intermediate layer has been performed using acid-catalyzed tetraethylthosilicate-ethanol-water sol solution. High bond strength near to the fracture strength of bulk silicon is obtained at low temperature, for example 100°C. However, The bond efficiency and bond strength of this intermediate layer bonding sharply decrease when the bonding temperature increases to elevated temperature, such as 300 °C. The degradation of bond quality is found to be related to the decomposition of residual organic species at elevated bonding temperature. The bubble generation and the mechanism of the high bond strength at low temperature are exploited.
Systematic Investigation of Tool Wear Monitoring in Turning Operations
Authors: Xu Nuo , Huang Samuel , Snyder John
Published: April 2008

This study investigates the feasibility of monitoring tool wear and surface finish based on force signal by conducting a set of experiments in turning operations. Our study shows that the force signal appears curvi-linear with both uniform and maximal tool wear and shifts systematically across different cutting conditions; the force frequency spectrum contains extra information yet proves difficult to interpret and utilize; the surface finish behaves rather erratic. Three modeling techniques, multi-layer neural networks, adaptive neural-fuzzy inference system and multiple linear regressions are all capable of capturing the underlying force-wear dependency. Inferences are made regarding some essential issues, e.g. wear classification versus continuous wear estimation, force, vibration, acoustic emission versus sensor fusion. The study also suggests that a monitoring scheme should ultimately link measured signals to workpiece geometry inaccuracy rather than just to tool wear parameters. Additionally greater efforts should be directed to the integration of tool wear monitoring and geometry tolerances control.
A New Integrated Design and Fabrication Process for Profiled Edge Laminae (PEL) Tooling
Authors: Walczyk Daniel F. , Yoo Seungryeol
Published: April 2008

Profiled Edge Laminae (PEL) tooling is a thick-layer Rapid Tooling (RT) method that was developed a decade ago. Even with demonstrable advantages for large-scale tool applications over conventional CNC-machining of a solid billet and other commercially available RT methods, PEL tooling has not seen widespread use by industry because prior research related to laminated tooling has (1) focused on small-scale tools and perpendicular laser-cutting that required extensive surface finishing, and (2) there is no integrated and practical design and fabrication approach to tooling development. This paper describes a more streamlined and integrated approach to PEL tooling development, called the PEL Process, that builds upon prior work in this area. Critical components of the process that are described in detail include how to obtain lamina slicing information directly from a CAD model of the intended tool surface, how to measure dimensional errors between the PEL and CAD tool surfaces, and improved Abrasive Waterjet cutting trajectory and laminae slicing algorithms. The PEL Process is then demonstrated for the design and fabrication of aluminum PEL tooling used for hydroforming aircraft sheet metal components.
An Application of Swept-Volume Computation In Machine Tool Probing
Authors: Maiteh Bilal
Published: April 2008

The machine tool probing can improve efficiency in many different ways, but it is underused in almost every manufacturing location. Part of the reason, probing is underused, is the complexity that often comes with adding probing to the process. Manufacturing companies generate milling and drilling tool paths with ease, using any of a variety of CAM systems. But probing calls for macros that are often either added to the NC code through manual editing, or else entered right at the CNC. This papers present a method to address this shortcoming. A method has been developed using a swept-volume computation to emulate the physical environment for probing process. The virtual probing trajectories are obtained from CAM software. In the mathematical algorithm, the swept volumes of the probing tools are computed from the probing tools’ geometric data and trajectories. Collision operations are then performed on the swept volumes of the virtual probing tools and the virtual machined workpiece to verify the probing process.
Mechanical Effects of Galvanic Corrosion of Thin Film Polysilicon
Authors: Miller David C. , Gall Ken , Stoldt Conrad R.
Published: April 2008

Mechanical, and electrical effects generated by the galvanic corrosion of polysilicon immersed in various hydrofluoric acid (HF)-based solutions are described. Micromachined test structures consisting of phosphorus-doped polysilicon in contact with a gold metallization layer are utilized. A suite of otherwise identical test (metal added) and reference (no metal) structures were used to investigate changes in key performance parameters. Corroded test structures demonstrate an increase in through-thickness strain gradient, a decrease in the characteristic frequency of mechanical resonance, no change in in-plane strain, greatly increased electrical resistance, a decrease in hardness, and a decrease in elastic modulus. Noteworthy results were observed for aqueous-hydrochloric acid, ethanol, water, ammonium fluoride (found in buffered oxide etchant), Triton-X-100, as well as vapor-HF based chemistries. This first systematic study validates preliminary experiments and demonstrates the impact of corrosion on miniaturized structures, indicating a potential influence upon the material properties, design, performance, fatigue, tribology (friction/ wear), manufacture, and packaging of micro-and nano-scale devices.
Heat and Mass Transfer Between Three Heat Carriers
Authors: Sheyman Vladimir
Published: April 2008

In this paper, a specific heat and mass transfer case between three components is considered, namely the heat and mass transfer of the suspension of solids particulates in air, in short a mixture, and the third heat carrier (gaseous or liquid) separated by the wall. Actually, this is a heat transfer between three heat carriers: a convection heat-and mass transfer between solid particulates and air as a conveying medium and a conduction heat transfer of this mixture with the third heat carrier through the wall.
Influence of Steam Injection on Thermal Efficiency and Operating Temperature of GE-F5 Gas Turbines Applying VODOLEY System
Authors: Ghazikhani Mohsen , Manshoori Nima , Tafazoli Davood
Published: April 2008

An industrial gas turbine has the characteristic that turbine output decreases on hot summer days when electricity demand peaks. For GE-F5 gas turbines of Mashad Power Plant when ambient temperature increases 1° C, compressor outlet temperature increases 1.13° C and turbine exhaust temperature increases 2.5° C. Also air mass flow rate decreases about 0.6 kg/sec when ambient temperature increases 1° C, so it is revealed that variations are more due to decreasing in the efficiency of compressor and less due to reduction in mass flow rate of air as ambient temperature increases in constant power output. The cycle efficiency of these GE-F5 gas turbines reduces 3 percent with increasing 50° C of ambient temperature, also the fuel consumption increases as ambient temperature increases for constant turbine work. These are also because of reducing in the compressor efficiency in high temperature ambient. Steam injection in gas turbines is a way to prevent a loss in performance of gas turbines caused by high ambient temperature and has been used for many years. VODOLEY system is a steam injection system, which is known as a self-sufficient one in steam production. The amount of water vapor in combustion products will become regenerated in a contact condenser and after passing through a heat recovery boiler is injected in the transition piece after combustion chamber. In this paper the influence of steam injection in Mashad Power Plant GE-F5 gas turbine parameters, applying VODOLEY system, is being observed. Results show that in this turbine, the turbine inlet temperature (T3) decreases in a range of 5 percent to 11 percent depending on ambient temperature, so the operating parameters in a gas turbine cycle equipped with VODOLEY system in 40° C of ambient temperature is the same as simple gas turbine cycle in 10° C of ambient temperature. Results show that the thermal efficiency increases up to 10 percent, but Back-Work ratio increases in a range of 15 percent to 30 percent. Also results show that although VODOLEY system has water treatment cost but by using this system the running cost will reduce up to 27 percent.
X-Ray Microanalysis of Metallic Thin Films
Authors: Ng F. L. , Wei J.
Published: April 2008

Nickel and gold films are widely used for microsystems fabrication and packaging, as well as under bump metallization. In this paper, x-ray microanalysis was used to measure the thickness of Ni and Au films. Au and Ni films with varied thicknesses were deposited on silicon (Si) substrate by magnetron sputtering method. Incremental electron beam energy ranging from 4 keV to 30 keV was applied while other parameters were kept constant to determine the electron beam energy required to penetrate the metallic films. The effects of probe current at a fixed electron beam energy on the penetration depth were investigated too. With higher energy applied, the electron beam can penetrate deeper and more Si signal can be detected. The Ni and Au film thicknesses almost have linear relationship with the required penetration electron beam energy. The probe current has minimal effect on the specimen once it has reached the critical excitation probe current. For Ni and Au films with same thickness, higher energy or probe current is needed to penetrate the Au film to reach Si substrate due to the higher Au atomic weight.
Calculated Behavior and Effective Factors for Bolt Self-Loosening Under a Transverse Cyclic Load Generated by a Linearly Vibrating Washer
Authors: Fujioka Yasuo , Sakai Tomotsugu
Published: April 2008

It is common knowledge that a bolt is apt to loosen due to slippage between the contact surfaces of joined parts. Loosening tests using real parts enable precise scrutiny of real phenomena under the influence of multiple factors such as slip distance, surface roughness, and coefficient friction. However, estimating the influence of the individual factors is very difficult because the friction forces of real contact surfaces are compiled based on variations in friction coefficients, meaning friction is not stable. Therefore, the effects of factors were investigated using Finite Element Analysis (FEA) to control friction coefficients. The procedures were as follows. Assuming a joined structure consisting of a bolt, nut, and washer, bolt axial tension was generated through constant movement of a washer in the bolt’s axial direction, following which the washer was constantly vibrated in one direction transverse to the bolt axis. This vibration generated displacements equivalent to the degree of slippage between the two clamped parts. During vibration, the rotating angles of the bolt and the contact pressure of the threads and bearing surfaces were calculated. The results were as follows. The vibrating displacements of a washer have considerable influence on the rotational loosening of a bolt. In cases where there was only minor displacement of the washer vibrations, the rotational loosening angle rapidly decreased, although the loosening did not cease completely. Therefore, the magnitude of what is called “critical slip” was not confirmed under the conditions of this study. In addition, the friction coefficient has a significant influence on the rotational loosening of a bolt. When the respective friction coefficient values of the threads and bearing surfaces are not balanced, rotational loosening cannot continue. Surface roughness readily affects contact pressure, so it tends to make the contact pressure localized. In particular, high-pressure areas were affected by several projections set on the threads. However, under those conditions the rotational loosening did not differ greatly from the results of the fine surface models subject to the same vibrating amplitude and friction coefficient. Consequently, the localized contact pressure had little evident effect on loosening. Above all, FEA reproduced the loosening of the bolt, and the reference made in this analysis is useful.
Effect of Grain Configuration on High Temperature Fatigue Crack Propagation of Ni-Based Directionally Solidified Superalloy
Authors: Yamamoto M. , Ogata T. , Kitamura T.
Published: April 2008

The crack assessment for the boilers or steam-turbines of conventional power plants has been carried out by means of conventional fracture mechanics. Here, the cracks are large enough in comparison with the grains in the material, so that the inhomogeneity due to the microstructure can be ignored. However, in the gas-turbine blade, the size of grain is relatively larger than that in conventional plant components, and the crack propagation property may be affected by the local grain configuration. Here, in order to clarify the crack propagation property of an anisotropic material (Ni-based directionally solidified superalloy for the gas-turbine blades), high temperature fatigue tests are conducted using longitudinal loading specimens with a crack (L-specimens) and transverse loading ones (T-specimens). The crack propagation rate is roughly correlated well with the effective stress intensity factor range regardless of the propagation direction (specimens L and T), the stress range, and the stress ratio. In detail, however, the crack propagation rate shows eminent fluctuation particularly in the T-specimens. It is about 5 times faster than the average at most. The feature of fracture surface can be classified into 4-types where 3 of them are transgranular and the other is intergranular. In the former, though the crack is along {100} or {110} planes in the macroscopic scale, it threads through {111} or {100} planes in the microscopic scale. The crack propagation is eminently accelerated in the intergranular region while the deceleration is caused by the crack-branching.
Thermal Needs and Challenges for the Solid State Lighting Devices: Materials to Packages
Authors: Arik Mehmet , Weaver Stanton , Setlur Anant , Haitko Deborah
Published: April 2008

Light emitting diodes historically have been used for indicators and produced low amounts of heat. The introduction of high brightness LEDs with white light and monochromatic colors have led to a movement towards specialty and general illumination applications. The increased electrical currents used to drive the LEDs have focused more attention on the thermal paths in the LED packages and developments in LED power packaging. The luminous efficiency of LEDs is soon expected to reach over 80 Lumens/Watt that is approximately 6 times more than a conventional tungsten bulb. The thermal challenges include but not limited to chip architecture, packaging, phosphors for light conversion, encapsulants and fillers for optical transparency, interconnects for both electrical and thermal reasons. A typical LED power-package has a 1mm2 surface area with a total heat generation of 1 W. This corresponds to a heat flux of 100 W/cm2, which is much higher than heat fluxes at the current electronics packaging. In this paper, effect of the thermal management on packaging architectures, as well as phosphor and encapsulants are discussed. Discussions on the microscopic defects due to packaging problems as well as chip active layer defects are presented through experimental findings.
Simultaneous Structure and Mechanism Design for an Adaptive Wing Using Topology Optimization
Authors: Joo James J. , Sanders Brian
Published: April 2008

A synthesis technique using a topology optimization scheme for an adaptive wing structure and mechanism design will be described. This enables the design of energy efficient adaptive structures with controllable deformation characteristics. This is accomplished by using a multi-objective function that minimizes strain energy and maximizes mutual potential energy to design the structure and mechanism simultaneously. To enable simultaneous design for structure and mechanism, the reference structure is composed of three layers; a membrane layer for skin, a frame element layer for structure, and truss element layer for an efficient mechanism. The attachment points between mechanism and structure are also identified with linear springs that are located between mechanism and structure layers. We focus on a simultaneous design of a wing structure and mechanism for large shape change applications. The geometrically large deformation analysis scheme is also added to the synthesis to capture nonlinear effects in design and it will be compared with linear synthesis results.
Large Medical Data Manipulation for Bone Surgery Simulation
Authors: Niu Qiang , Chi Xiaoyi , Leu Ming C.
Published: April 2008

Medical image data obtained from Computed Tomography (CT) are used as input to reconstruct and visualize 3-D structures of human bones for the purpose of developing a virtual reality (VR) based bone surgery system. These data are used for geometric modeling, force modeling, and model update to perform simulation of material removal with graphic and haptic rendering. One important issue in bone surgery simulation is to handle the large, complex, and often poor-quality data. Although the processing power of personal computer has increased greatly over the years, improper data handling can still cause implementation problems such as excessive memory consumption, low data processing speed, and incapability of real-time simulation. This paper presents a method for managing large CT scan data based on the consideration of implementation complexity, memory storage and computational overhead. Besides medical data acquisition and image processing, two important computer graphics concepts, i.e. bounding volume and adaptive subdivision, are applied to remove irrelevant data and to organize the rest data. Two data structures, a complex linked list and a Quadtree list, are developed to store and organize the image data. These data are processed before VR simulation so as to reduce the data update time. With the proposed method, the memory bandwidth requirement is reduced drastically and real-time simulation performance is achieved.
Methodology for Modeling of Passive Shunt Damping of Systems With Bonded Piezocomposites
Authors: Saigal Anil , Greif Robert , Ng Jane
Published: April 2008

An aluminum cantilever beam bonded with 1-3 piezocomposite dampers is modeled by means of ANSYS finite element and SIMULINK simulation softwares. ANSYS currently cannot account for heat dissipation in piezoelectric materials. As such, ANSYS is used to obtain strain energies to be input into the SIMULINK model to investigate the dynamic behavior of the system and calculate the damping ratio. The impact of two different shunting arrangements, a damper in conjunction with a simple resistive electrical circuit in series and parallel, is investigated. In addition, a simply supported beam and a simply supported straight pipe are also analyzed for their wide applications in industry, and as an indication of the utility of this methodology to analyze complex structural configurations. For a typical cantilever beam, energy dissipation and transient analysis are used to calculate the tip displacement as a function of time and the damping ratio. Then using ANSYS, with the parameter BETAD to incorporate damping as a stiffness multiplier, a comparison of the transient results is used to quantify the damping response of aluminum beams with bonded 1-3 piezocomposite dampers. The system loss factor due to the piezoelectric damping is also compared to the inherent loss factor of different beam materials. The results show that circuits in series provides a better damping ratio (0.000581) as compared to circuits in parallel (0.000374). In addition, for different boundary conditions (cantilever, simply supported), the damping ratios (0.000581, 0.000202) and the BETAD values (6.3 E-6, 0.7 E-6), respectively, are functions of the boundary conditions and are not directly related to each other. Finally, damping using 1-3 piezocomposites effectively increases the overall system loss factor by at least 100% to almost 300% as compared to the inherent material damping. In general, this methodology of combining finite element method (ANSYS) and transient modeling tools (SIMULINK) can be used to study damping characteristics of any structural system damped with 1-3 piezocomposites.
Analytical Study of the Effect of Heat Pipe Cooling in Machining
Authors: Chiou Richard Y. , Aynbinder Vitaliy , Stepanskiy L. G. , Lu Lin , Rauniar Shreepud , Chen Jim S. J. , North Mark T.
Published: April 2008

Tool wear of machine tools and large usage of cutting fluids is one of the major problems in manufacturing. Cutting fluids are used to cool down the tool and have been shown to cause environmental problems in machine shops. Tool life and temperature have an inverse relationship, namely that the higher the temperature at the tool-chip interface is, the lower the tool life will be, and vice-versa. In this paper an innovative approach was taken to create an analytical solution to the effect of the embedded heat pipe on temperature of the tool and tool life. It has been well documented in the industry that the major factors that contribute to tool wear are the material properties of the tool insert and the work piece, cutting speed, depth of cut and feed rate. The analytical approach taken in this project is unique because it does not only take into account the complex boundary conditions of heat transfer but also the aforementioned factors and variety of possible cutting conditions. The analytical solution is in the form of set of equations which were developed to simulate the behavior of the tool insert under normal cutting conditions. Both cases, with and without heat-pipe were considered. The predicted temperature data was then compared to the existing experimental data, with very good results. In the end the project yields a quantitative evaluation on influence of mechanical properties of insert, work piece, heat pipe and cutting conditions on tool wear.
Transition Boiling Heat Transfer of Droplet Streams and Sprays
Authors: Bernardin John D. , Mudawar Issam
Published: April 2008

An experimental study was performed to characterize the transition boiling heat transfer rate from a surface to a stream of impinging water droplets, and to extrapolate this information to predict the transition boiling heat transfer of a dilute spray. First, transition boiling heat transfer data was gathered for a continuous stream of monodispersed water droplets striking a polished nickel surface. From this data, empirical correlations were developed to describe the heat transfer rate and heat transfer efficiency for droplet velocities between 1.0 and 7.1 m s−1, droplet diameters ranging from 0.250 × 10−3 to 1.002 × 10−3 m, and surface temperatures covering 110 to 240°C. By properly accounting for the hydrodynamic differences between a spray and a single droplet stream, the empirical single droplet stream heat transfer correlations were effectively extrapolated into a model for predicting the transition boiling heat flux of dilute sprays (Q′ ≈ 0.5 × 10−3 m3s−1m−2).
Eliminating Redundant Operations While Improving Part Quality by Modeling Machining Errors
Authors: Agapiou John , Steinhilper Eric , Bandyopadhyay Pulak , Xie Jeffrey Q.
Published: April 2008

A methodology to predict part quality was applied to the perpendicularity quality of the bell face and main axis of a transmission case. By modeling the quality of different processing sequences, we were able to show that the quality of the part - perpendicularity of critical features - does not improve significantly by performing two-pass machining process instead of a single-pass. This application of our quality methodology required the modeling of additional system errors which were not developed in the earlier version and which were needed to predict certain types of form errors. In addition to improved part quality, changing the existing line to a single-pass process eliminated a bothersome job-setting procedure and tooling costs at the second-pass and increased productivity of a rebalanced line.
Superharmonics-Free Adaptive Semiactive Magneto-Rheological Suspension
Authors: Song Xubin , Ahmadian Mehdi , Southfield Steve , Miller Lane
Published: April 2008

This paper focuses on laboratory implementation of a semiactive seat suspension with application of magneto-rheological (MR) dampers. We firstly introduce the nonlinear dynamics phenomena induced with the skyhook control that is now widely applied from structural vibration suppression to commercialized vehicle suspensions. However, superharmonic dynamics has not been clearly addressed in such vibration control systems. This paper tries to explain how superharmonics are created with skyhook controls through testing data analysis. Furthermore, in order to avoid this dynamics issue, this study implements a nonlinear model-based adaptive control into this MR damper based seat suspension. Based on a nonparametric MR damper model, the adaptive algorithm is expanded mathematically, and the system stability is discussed. Then in the following sections, this paper describes implementation procedures such as modeling simplification and validation, and testing results. Through the laboratory testing, the adaptive suspension is compared to two passive suspensions: hard-damping (stiff) suspension with max current of 1A to the MR damper, and low-damping (soft) suspension with minimum of 0A, while broadband random excitations are applied with respect to the seat suspension resonant frequency in order to test the adaptability of the adaptive control. Furthermore, mass and spring rate are assumed known and unknown for this adaptive controller to investigate the capability of this algorithm with the simplified model, respectively. Finally the comparison of testing results is presented to show the effectiveness and feasibility of the proposed adaptive algorithm to eliminate the superharmonics from the MR seat suspension.
Sliding Mode Control of Underactuated Biped Robots
Authors: Nikkhah Mehdi , Ashrafiuon Hashem , Fahimi Farbod
Published: April 2008

This paper presents a robust tracking control algorithm for underactuated biped robots. The biped considered in this work is modeled as a five-link planar robot with four actuators located at hip and knee joints to control the joint angles. The control law is defined based on the sliding mode control approach. The objective of the controller is to generate stable walking based on predefined desired trajectories. The planning of the trajectory in swing phase is discussed while the double support phase is considered to be instantaneous and the impact of the swing leg with the ground is modeled as rigid body contact. In order to formulate the sliding control law, we define four first-order sliding surfaces, based on the number of actuators, as a linear combination of tracking joint positions and velocities. The control approach is shown to guarantee that all trajectories will reach and stay on these surfaces. The surface parameters are then selected to ensure the stability of the surfaces leading to an asymptotically stable control law. Numerical simulation is presented for tracking a multi-step walk of a biped robot.
Nanoparticle Concentration in Buoyancy Flows
Authors: Nnanna A. G. Agwu
Published: April 2008

The presence of nanoparticles in buoyancy-driven flows affects the thermophysical properties of the fluid and consequently alters the rate of heat transfer. The focus of this paper is to estimate the range of volume fractions that results in maximum thermal enhancement in buoyancy-driven nanofluids. In this study, a two-dimensional rectangular enclosure with isothermal vertical walls and adiabatic horizontal surface is filled with 27nm Al2O3 - H2O nanofluid. The volume fraction is varied between 0 to 12%. Results shows that for small volume fraction, 0.2≤Φ≤2%, the presence of the nanoparticles does not impede the free convective heat transfer, rather it augments the rate of heat transfer. However, for large volume fraction, Φ>2%, the convective heat transfer coefficient declines due to reduction in the Rayleigh number but the rate of thermal diffusion is enhanced.
Surface Tension Actuators Droplets in Microchannels
Authors: Baird Eric , Mohseni Kamran
Published: April 2008

A unified model is presented for the velocity of discrete droplets in microchannels actuated by surface tension modulation. Specific results are derived for the cases of electrowetting on dielectric (EWOD), dielectrophoresis (DEP), continuous electrowetting (CEW), and thermocapillary pumping (TCP). This treatment differs from previously published works by presenting one unified analytic model which is then simply applied to the specific cases of EWOD, CEW, DEP and TCP. In addition, the roles of equiliubrium contact angle and contact angle hysteresis are unambiguously described for each method. The model is shown to agree with experimental and theoretical results presented previously, predicting fluid velocities for a broad range of applications in digitized microfluidics.