bluuebunny/crossref_metadata_2025 huggingface dataset:
New Electrical Potential Method for Measuring Crack Growth in Nonconductive Materials
Authors: Nayeb-Hashemi H. , Swet D. , Vaziri A.
Published: May 2008

D.C. electric potential technique has been used to monitor crack growth in conductive materials. A constant DC current is ppased through thesse materials and the crack length is measured through the changes in the electrical voltage at the crack mouth. However, this method is not applicable in crack growth measurement in nonconductive materials or adhesively bonded joints. For these materials, a new method is developed and is shown to provide a very accurate method for measuring the crack length. The surface of these materials is coated with a thin layer of carbon paint and the crack lenght is measured through the changes in the electrical resistance of the carbon paint, as the crack grows both in the base material and the thin layer carbon paint. In contrast to the D.C. electric potential technique where the position of the probes for measuring the crack length is very important for an accurate measurement of the crack length, the new technique is little sensitive to the probe location. Crack growth is measured in adhesively bonded joints subjected to creep loadings. A modified Compact tension specimen is cut in two pieces across its notch area. The pieces are then glued jusing an adhensive. The surface of the specimen is painted with a thin layer of carbon paint and the changes in its electrical resistance are monitored. It is shown that the carbon paint method provides a quiet sensitive method for monitoring the crack growth. The creep crack growth rate in the adhesively bonded joint is related to Mode I energy release rate, G1. It is shown that the crack grows in the middle of the adhesive layer rather than at the interface of the joint. Micromechanisms of the crack growth are studied using a scanning electron microscope. The damage consists of numerous crazed regions at the crack tip. Crack grows by the linkage of the crazed region.
Validation and Implementation of Control Strategies for Liquid Composite Molding Processes
Authors: Devillard Mathieu , Hsiao Kuang-Ting , Advani Suresh G.
Published: May 2008

The manufacturing of polymeric composites ranges from using a rudimentary hand lay-up to the use of automated processes such as Liquid Composite Modeling (LCM) developed over the past decades in order to increase the yield of manufactured composite parts. In these processes, fiber preforms are placed in a closed mold and resin is infused into the mold to saturate the preform. After the resin cures, the mold is opened and the net shape composite part is demolded. However, by introducing more complexity into the part, one also introduces higher probability of flow disturbances, such as race tracking along preform edges, into the molding system. This can lead to incomplete saturation of fiber performs resulting in flaws such as dry spots in the composite part. The strength and existence of race-tracking is a function of the fabric type, perform manufacturing method, and its placement in the mold. It can vary from one part to the next in the same production run, and therefore it is not repeatable. In this work, after illustrating experimentally the unpredictability of variation of race-tracking and its influence on the flow, two approaches have been investigated and validated to address this issue associated with the variation of inherent disturbances in LCM processes. An active control strategy method using process models and simulations along with sensing and control to address flow disturbances during the impregnation stage of the process was shown to be reliable and effective for Resin Transfer Molding (RTM) process. In an attempt to improve the automation of RTM process, a modular RTM workstation including all hardware and software necessary to implement active control strategies for various part geometries and a novel injection system was designed and tested. In addition, a passive control method for Vaccum Assisted RTM (VARTM) aimed at optimizing the placement of distribution media for a given set-up in order to reduce dry spot formation and filling time was developed and validated experimentally. The optimization method employs numerical flow simulations and global optimization search techniques (Genetic algorithm) to generate the design for strategic flow control system.
3-D Simulations of Non-Newtonian Fluid Flow in Rectangular Cavity
Authors: Bakhtiyarova Ayten S.
Published: May 2008

In this paper we present the results of the 3-D simulations of the power law model fluid flow in rectangular cavity. FLOW-3D commercial, software (Flow-Simulations, Inc.) has been used to predict flow velocity distributions and pressure losses when non-Newtonian fluid flows through the square cavity.
The Treasure in Technical Information: A Research Project for All Disciplines
Authors: Harding Bruce A.
Published: May 2008

Engineering practitioners often find themselves required to locate technical and non-technical information from a variety of sources. They may generate quotes, research equipment specifications, determine market shares, delineate a proposed manufacturing process, find company profiles, retrieve demographics data, certify compliance with international or national standards, or research any one of countless other pieces of information. This may involve books, CDs, periodicals, newspapers, corresponding via email, fax, letters or the worldwide web, across several languages. Few classroom projects address practitioner’s needs for broad information research skills. This paper details strategies for a unique student research project leading to useful experience applicable to engineering and engineering technology practitioners in any discipline, in any locality. The project could be instituted in virtually any class at any level and run in any language. It is readily adaptable to changing technology, any textbook, and has now been in use since 1982. As implemented at Purdue University, it has been cited by multiple ABET re-accreditation teams for innovation and as an excellent example of continuously improved instruction. Over the years it has grown to become one of the more noteworthy experiences cited in both student exit surveys and in graduate surveys.
Visual Information Model of Car-Body Welding and Assembly Process
Authors: Sui Bo , Du Dong , Chang Baohua , Zhai Feng , Wang Li
Published: May 2008

The complexity of car-body welding and assembly process makes it difficult for engineers to design and analyze the process parameters. Therefore, a tree-relation mixed data model, based on the characteristics of car-body assemply process, is put forward to represent the welding and assembly process. By integrating this data model with CAD/CAM model and 3d graphic simulation platform, a visual information model is built up. A case study is performed on the visualization of car-door welding and assembly process plan using this information model. The result shows that the model is able to represent the process plan of welding and assembly process visually and integrally. The model can be used for auto-body design, welding-process analysis and design, process information management, quality control and personalized selling.
Large Electrostatic Deformation of a Dielectric Elastomer Annulus
Authors: Yang Eunice E. , Frecker Mary , Mockensturm Eric
Published: May 2008

A large quasi-static deformation analysis of a thin annulus made of dielectric elastomer is presented in this paper. The material is assumed to be perfectly elastic, isotropic, and incompressible. An electric field is applied through the thickness of the annulus. The outer periphery of the annulus is held fixed, while the inner periphery is free to move. The radial stress and strain distributions are determined using two nonlinear differential equations obtained from equilibrium, stress-strain and geometric relations. Mooney’s (1940) from of the strain energy function is used for the analysis. The non-linear differential equations are solved for the principal extension ratios, λ1 and λ2, using Matlab’s two-point boundary value function BCP4C. The radial and circumferential stresses are calculated using the derived solutions. The resluts of the mathematical model showed that for increasing effective (squeeze) pressure, the readial and circumferential stress transitions from tensile to compressive states at a “critical” effective (squeeze) pressure. Also, for the annulus with non-zero hole pressure, there exists an operating range for both the hole pressure and effective (squeeze) pressure of which the model is mathematically as well as physically viable.
Steady Flow of Visco-Plasto-Elastic Fluids in Pipes
Authors: Letelier Mario F. , Siginer Dennis A.
Published: May 2008

The objective of the paper is to analyze the main dynamic characteristics of steady pipe flow for the case of a fluid whose constitutive is determined by a linear superposition of a viscoelastic Phan-Thien-Tanner fluid and a Bingham-type plastic fluid. The combined effects of viscoelasticity and yield stress are explored through some variables of the flow, such as velocity, and plug region. The fluid is considered incompressible and laminar, the pipe circular. One main motivation of this work is the study of possible relevant interaction among the physical properties of the fluid. The elasticity of the fluid is expressed by means of two parameters that include the relaxation time. The plasticity is modelled though the Bingham constitutive equation, which involves, in general, a constant yield stress and a non-linear viscosity, when the flow is non-axisymmetric. Analytical expressions for the dependent variables are presented, and their plots in terms of the constants of the fluid, as well. This paper is continuation of previous work by the authors, mainly related to investigating the structure of secondary flow and of the associated heat transfer in non-circular ducts, for the case of a purely viscoelastic fluid.
Hardware-in-the-Loop Simulation for Control Development in EHPV Applications
Authors: Jung Sooyong , Lee Young J. , Book Wayne J.
Published: May 2008

The creation of a PC-based Hardware-In-the-Loop Simulation facility for testing hydraulic and other drive components and their controllers is described. High performance electric motors are used to produce both drive and load characteristics as commanded by the simulated environment. To enable rapid development of new application scenarios an integrated software environment has been incorporated to rapidly model, program and simulate the environment’s behavior and the controlled response. In order to validate the HIL testbed developed, the experiment is performed on hydraulic component with wide range of applications. For the next stage, a novel Electroi Hydraulic Popper Valve (EHPV) is targeted to be studied.
Monte Carlo Simulation of Boundary Scattering Effects for Power MOSFET Performance
Authors: Marathe A. , Walker D. G.
Published: May 2008

Miniaturization of microelectronic devices has lead to many new issues not seen in larger structures, such as hot carrier effects and interfacial effects. In power MOSFETs, degradation of the transconductance can occur over the lifetime of a device. This decrease in performance is a result of hot carriers in the channel region scattering at a Si/SiO2 interface that has been passivated with hydrogen. Eventually hot carriers liberate the hydrogen, leaving silicon bonds with an entirely different scattering cross section. The current work presents a Monte Carlo simulation of carrier transport in silicon near an interface. Scattering parameters at the interface are parameterized and studied. It was found that electron mobility, which is proportional to transconductance, is a function of the energy loss rate and type of scattering at the interface. Results indicate that dangling bonds and H-Si bonds can be characterized by different scattering mechanisms.
Exergoeconomic Assessment of the Performance Degradation in a Power Plant at Full and Partial Load
Authors: Cziesla Frank , Tsatsaronis George
Published: May 2008

Power plant performance deteriorates during operation due to degradation of plant components. This paper deals with the calculation of costs associated with the degradation of selected plant components in a 400 MW pulverized coal-fired subcritical power plant at full and partial load. A commercial process simulator (Gate/Cycle) is used to study the thermodynamic behavior of the plant at various loads. In several case studies, the performance of one or more plant components is deteriorated by altering performance factors (i.e., fouling factor for heat exchangers and isentropic efficiency for turbomachinery). An exergy analysis and a detailed exergoeconomic evaluation are conducted for each case study. Selected exergoeconomic variables defined for each plant component assist in identifying the location of degradation and its effect on the performance and the product coast for single components and the total plant. Such an approach can be applied to process monitoring of a real plant and provides useful information for the diagnosis and assessment of deteriorated power plant performance.
The Mixed Mode Crack Problem in a FGM Layer
Authors: Long X. , Delale F.
Published: May 2008

Functionally graded materials (FGMs) are multiphase composites whose composition, microstructure and properties vary gradually. They can be tailored to meet the requirements encountered in practice through the design of their constituents. In this paper, analytical expressions for stress intensity factors off mixed-mode cracks in a FGM strip have been derived for the first time. A parametric study, by varying both the geometric and material parameters, is conducted to determine their effects on the stress intensity factors.
Simulating the Response of Composite Reinforced Floor Slabs Subjected to Blast Loading
Authors: Lawver Darell , Daddazio Raymond , Oh Gwang Jin , Lee C. K. B. , Pifko Allan B. , Stanley Michael
Published: May 2008

The threat of terrorist attack against civil infrastructure in the US and other countries has led to the need to better understand the response of structures and structural components to an impulsive air blast overpressure. One scenario that is present in many cities is delivery trucks entering basement or street level loading/unloading areas. A bomb present in one of these delivery trucks could cause considerable damage to the floor slab (and consequently the building) above the blast by causing a vertical uplift, a condition that the slab was not designed to resist. Traditional methods to retrofit floor slabs to resist an upwards blast pressure require that additional tension sustaining reinforcing bars (rebars) be placed near the slab upper surface. This reinforcing method is costly, difficult to produce, and adds additional weight to the overall structure in building retrofit situations. Another approach to reinforcing the slab is to bond light-weight, high strength fiber composite material to the slab upper surface as a means of resisting the tensile forces from the slab upward motion. This paper presents results from an effort to simulate the response of a reinforced concrete floor slab with a fiber composite retrofit subjected to a blast overpressure. The simulations were performed using the Weidlinger Associates’ FLEX [1] finite element code for structural response calculations. The MAZ [2] computational fluid dynamics code was used to generate blast pressure. This paper will discuss the modeling effort used to predict the response of fiber composite retrofitted slabs and compare the computational analysis to test results1.
Computation of Internal Separated Flows Using a Zonal Detached Eddy Simulation Approach
Authors: Slimon Scot
Published: May 2008

This paper investigates the use of the Spalart-Allmaras one-equation turbulence model with detached eddy simulation (DES) modifications for predicting internal separated flows. For these flows, it is shown that the use of grid spacing to segregate Reynolds-averaged Navier Stokes (RANS) and large eddy simulation (LES) modes in the DES approach is cumbersome, and not practical in some cases. To allow DES to be more readily applied to such flows, a zonal approach is proposed. In this approach the LES mode in DES is only used in detached shear layer regions. These regions are dynamic, and are defined by local flow and turbulence quantities during the computation. No blending of RANS-based and LES-based regions is used in the approach such that the attached shear layer calibration of the underlying RANS-based turbulence model is not affected. The zonal DES approach is applied to two internal flows: a stenosis in a pipe and a 180° turn-around duct. Results show that the zonal DES predictions are in excellent agreement with the experimentally measured velocity profiles and pressure distributions, and are significantly improved relative to RANS predictions.
A Reagent Dispense Verification System for a Fully-Automated, Amplified Nucleic Acid Diagnostic Instrument
Authors: Kennedy Mark R. , Pacheco Raul , Van Doorn John , Hipolito Rommel
Published: May 2008

Amplified nucleic acid diagnostics have brought extraordinarily powerful biochemical tools to bear on screening for and diagnosing infectious diseases. For example, current assays routinely permit the detection of 100 particles of human immunodeficiency virus or hepatitis C virus in one mL of blood. Such assays are used for screening the blood supply. To permit reliable automation of these complex and sensitive assays fluidic measurement and control systems are required. Such controls are needed to ensure that correct reagents are reliably dispensed into the reaction tubes. In this paper we will review the design and performance of a prototype Reagent Dispense Verification system for use on a fully-automated, amplified, nucleic acid diagnostic instrument. The system design utilizes hydraulic pressure drop and conductivity as the primary dispense parameters. In addition to the dispense verification function, the system provides a capacitive liquid level sensing function. The pipetting probe design and manufacturing process provide two conductive surfaces separated by an electrically insulating gap over which conductivity is measured. Hydraulic pressure drop is measured with an in-line, flow-through pressure transducer. The time-varying pressure and conductivity signals are used to classify each dispense operation as acceptable or not. Overall system performance data are presented demonstrating the viability of the design.
Dependence of Pressure Losses on Angle of Attack for Flow Through Perforated Plates
Authors: Yavuzkurt Savas , Catchen Gary L.
Published: May 2008

We have measured the dependence of pressure losses on angle of attacks in pipe flow through a set of seven perforated metal plates. Pressure losses were measured in air flow at temperature and pressure about 24°C and 736 mm Hg. The nominal pipe diameter is 3.5″ resulting an internal pipe diameter of 90.17 mm. Specifically, the plates differ in type of metal, thickness, hole size, and hole spacing. Using a pipe-flow apparatus in which the angle of attacks for the plate was set at either, 0°, or 45°, or 22.5°, we measured the pressure losses over speeds ranging up to approximately 30 m/s. Generally, the pressure loss increases linearly with the square of the air speed; and, in this context, the ratio of pressure loss to air speed squared represents a classical loss coefficient, K, for perforated plates. For a specific air speed, the magnitude of the loss coefficients positively with the ratio of the distance between hole centers to the hole diameter, s/D. The geometric effects associated with changing the angle of attack are complex, and a single dimensionless ratio such as s/D provides insufficient information to describes this effect. However, the measurements do indicate that the loss coefficient K depends on the ratio, s/D, raised to a power of approximately 4.8. Flow visualization may provide some more insight into the specific physical phenomena responsible for these pressure losses.
Fabrication of Ti Retinal Microtacks Using Ultra-High-Precision Micromilling
Authors: Cambron Scott , Keynton Robert , Walsh Kevin , Naber John , Kaplan Henry , Shire Doug , Rizzo Joseph
Published: May 2008

To adhere an artificial retinal implant onto the epiretinal surface of the eye, our group has designed retinal microtacks. The microtacks were fabricated by first bonding titanium foil to a silicon wafer; the tacks were then machined using an ultra-high precision micromilling technique with a 150-μm end-mill. The versatility of the micromilling technique allowed a partially conical, tapered tip to be added to the Ti tack, which created a sharp point. The Ti tacks average overall length and width were measured to be within 1% and 6%, respectively, of the design. Additionally, the grip width, stop thickness, and the tip taper angle of the Ti tacks were within 3%, 9%, and 4%, respectively, of the design.
Thermophysical Modeling of CO2 Laser-Silica Glass Interaction
Authors: Zhao Jian , Sullivan James , Zayac John , Bennett Ted D.
Published: May 2008

The thermophysical nature of rapid CO2 laser heating of silica glass is explored using a numerical simulation that considers the temperature dependence of the glass thermophysical properties. A three dimensional heat transport model is developed to investigate the change in glass fictive temperature that occurs as a result of a CW CO2 laser processing of silica glass. The model reveals that the laser processing results in an increase in fictive temperature in the local laser affected zone. The fictive temperature is elevated by about 1000K, uniform to within 5% over the laser affected zone, and transitions abruptly to the untreated glass value outside of the laser affected zone. This increase corresponds to a change in the glass physical and chemical properties, which can be revealed through wet chemical etching. The relationship between etch rate and the fictive temperature is determined by etching samples of known fictive temperature. The thermal penetration depth, defined as the maximum depth to which the glass fictive temperature is increased by the laser-silica glass interaction, can be determined from the thermophysical model and compared with the results from wet chemical etching.
Predicting Residual Thermal Stresses in Friction Stir Welding
Authors: Khandkar Mir H. Zahedul , Khan Jamil A.
Published: May 2008

Sequentially coupled finite element models of the friction stir welding process have been proposed to study the residual stresses caused by the thermal cycles during friction stir welding of metals. This is a two step simulation process. In the first step, the thermal history is predicted from an input torque based thermal model. The temperature history generated by the thermal model is then sequentially coupled to a mechanical model that predicts the residual stresses. The model does not deal with the severe plastic deformations within the weld nugget and the thermo-mechanically affected regions, a fact that may cause modeled results to deviate from experimentally measured residual stresses. The model is three dimensional and uses temperature dependent material and thermophysical properties.
Fuel Savings Analysis and Weapon Platform Thermal Management Options in a Tactical Aircraft
Authors: Ramalingam Mysore , Mahefkey Thomas , Donovan Brian
Published: May 2008

A general thermodynamic analytical program was developed to investigate the impact of secondary power system (SPS) improvements on mission effectiveness and weapon power generation in a tactical aircraft. Preliminary analysis revealed, among other things, that the engine performance was more sensitive to pneumatic bleed than to shaft power extraction and the use of a More Electric secondary power system resulted in a savings in fuel consumption. Using the total fuel consumption of the conventional aircraft for a typical tactical mission as a baseline, the fuel savings could potentially offer two alternatives to improved performance. The first alternative addresses multiple combat mission legs with varying altitudes and consequently a longer combat duration. The second alternative addresses the use of excess power to activate an airborne weapon platform and subsequent evaluation of thermal management limitations posed by several exploratory concepts. Three different thermal management approaches were considered for a typical airborne solid-state laser based power system with a laser output power of 100 kW. Some of the consequences of using these thermal management concepts on the mission legs in a tactical mission from a time-constraint and mass-constraint points of view are also presented.
Analysis of Collision Safety Associated With Conventional and Crash Energy Management Cars Mixed Within a Consist
Authors: Severson Kristine J. , Tyrell David C. , Perlman A. Benjamin
Published: May 2008

A collision dynamics model of a passenger train-to-passenger train collision has been developed to simulate the potential safety hazards and benefits associated with mixing conventional and crash energy management (CEM) cars within a consist. This paper presents a comparison of estimated injuries and fatalities for seven collision scenarios based upon the variable mix of conventional and CEM cars. Based on the analysis results, recommended car placement when mixing cars within a consist is identified. The model includes a 6 car cab car-led consist colliding with a 6 car locomotive-led stationary consist. The stationary consist is made up of all conventional cars. The moving consist has a variable mix of conventional and CEM cars. For comparison, the bounding scenarios are: - a moving consist with all conventional cars, and - a moving consist with all CEM cars. The collision speed ranges from 15 to 35 mph. Since the two car designs behave differently under impact conditions, there is a concern that there may be hazards associated with mixing the two designs in the same consist. In none of the cases evaluated is the mixed consist less crashworthy than the conventional consist. The modeling results indicate that the least crashworthy consists are ones in which a conventional cab car is leading any combination of vehicles. The conventional cab car incurs nearly all the damage and prevents trailing cars from participating in energy absorption, whether they are conventional or CEM. The most crashworthy consists are ones in which a CEM cab is leading. The CEM cab can absorb a significant amount of energy without intruding into the occupied volume. The CEM cab also allows trailing cars to participate in energy absorption, which provides further occupant protection. The recommended strategy for car placement is to put the CEM car(s) at the leading end(s) and the conventional car(s) at the trailing end or in the middle of the consist in push-pull operation. There is also significant benefit to placing the seats in the leading CEM car or two so they are rear-facing. Rear-facing seats can reduce the severity of secondary impact injuries because the occupant is already in contact with the seat in the direction of travel and does not develop a significant velocity relative to the seat.
Qualification and Acceptance Testing of a High-Speed Passenger Locomotive Using Instrumented Wheelsets
Authors: Lewis Kevin M. , Jackson Randall L. , Carter David W.
Published: May 2008

New Jersey Transit’s (NJT) ALP-46 locomotives have been successfully introduced into revenue service. On April 7, 2003, NJT received Federal Railroad Administration (FRA) approval to operate at 100 mph on Amtrak’s Northeast Corridor. Bombardier Transportation (Holding) USA, Inc. supplied these all-electric locomotives after proving the safety and performance of their product by passing an aggressive test specification prescribed by the FRA. The FRA specifications call for strict dynamic performance and compliance with wheel/rail interaction forces. Transportation Technology Center, Inc. (TTCI), a wholly owned subsidiary of the Association of American Railroads (AAR), designed and constructed two instrumented wheelsets (IWS) for use on NJT’s ALP-46 Locomotive Project. This Cardan drive locomotive required an innovative wheelset design because the right and left wheel plate shapes were not the same. To complete this unique system, TTCI incorporated a new amplifier system that digitized all the signals and transmits them via a single fiber optic cable to the data collection and analysis computer. This system eliminated the need for traditional slip rings normally used to transmit signals from rotating equipment. The vehicle qualification tests were conducted on Bombardier’s ALP-4601 locomotive in Amtrak’s Northeast Corridor (NEC) from Newark, New Jersey, to Philadelphia, Pennsylvania. The maximum speed achieved was 110 mph and the maximum cant deficiency (CD) was 6 inches. The FRA criteria for the vehicle qualification test were pre-programmed into TTCI’s real-time data analysis system to produce exception reports every 3 minutes during the actual testing. All data and any exception reports are referenced to a milepost via Global Positioning System (GPS) signals that are incorporated as part of the data collection.
Diffusion-Limited Evaporation in Long Microchannels
Authors: Jin Songwan , Breuer Kenneth S.
Published: May 2008

The evaporation of liquids confined to long, shallow microchannels is studied experimentally. Channels with dimensions 5 microns high, 100 microns wide and approximately 9000 microns long are filled with a liquid and then allowed to dry out due to evaporation through ports at both ends of the channel. The slug of fluid is observed to shrink at a rate that is, after some adjustment time, found to be linearly depend on the inverse of the meniscus position. In case of the water, the contribution of film flow in the microchannel evaporation is found to be larger than ethanol. But the surfactant cannot make much difference on the microchannel evaporation.
Impact of High Velocity Objects Into Concrete Structures: Methodology and Application
Authors: James R. J. , Zhang L. , Rashid J. Y. R.
Published: May 2008

Lifeline safety structures, such as, for example, concrete dams, nuclear power plants, and highway bridges, are designed to high levels of safety using traditionally conservative methods. Events of recent years, however, have raised public concerns about the degree of vulnerability of these structures to deliberate attacks involving large-airplane crash or close-proximity blast loading. This paper presents recent development in the state of the art of finite-element-based constitutive modeling and computational methodology of reinforced concrete with emphasis on severe damage modeling and failure evaluation. Verification and validation of the developed methodology is illustrated using high-velocity impact tests conducted in the U.S. and Japan. This involves explicit finite element computations for high velocity rigid missiles impacting reinforced concrete walls. Application of the methodology to nuclear fuel facilities is discussed.
Application and Validation of CFD in a Turbomachinery Design System
Authors: Anderson Mark R. , Gu Fahua , MacLeod Paul D.
Published: May 2008

CFD (Computational Fluid Dynamics) has enjoyed widespread use in the turbomachinery industry for some time. When coupled with other solvers, such as meanline and streamline curvature, it can be an integral part of a comprehensive design and analysis system. The pbCFD (Pushbutton CFD®) product is the CFD component of Concepts NREC’s Agile Engineering Design System®. It is a structured grid CFD flow solver optimized for turbomachinery analysis. Concepts NREC has made an extensive validation effort over a wide range of diverse turbomachinery stages including, compressors, pumps, and turbines for both radial and axial machines. Detailed comparison to test data of 10 different stages is shown in this paper and clearly demonstrates the high performance of pbCFD in quantifying fluid dynamic losses and pressure changes over a wide range of geometries and flow conditions.
A Development of Virtual Manufacturing System for Magnesium High Pressure Die Casting Processes
Authors: Chen Weilong
Published: May 2008

In recent years, high-pressure die-casting magnesium components have been gaining currency worldwide because of the excellent properties that magnesium alloys can offer to meet new product requirements. With the increasing application of magnesium parts worldwide, many research and development projects have been carried out to advance HPDC technology. However, truly optimized mold design and production of defect free castings remains a challenge for die casters. For many HPDC magnesium products, especially those specified for porosity-free and high cosmetic requirement, the challenge not only comes form a lack of a deeper understanding of how molten magnesium alloys fill the mold cavity and form defects, but also from improper preliminary part design. This study proposes a virtual prototyping system that integrates several effective soft and hardware tools for both the part and mold-design engineer to evaluate part manufacturability. Also, investigated in this study are the major causes of those defects that are the predominant cause of rejection of thin walled, leak-free magnesium parts requiring highly cosmetic finishes.
Development of an Electrohydrodynamic Injection Micropump for Cryogenic Cooling
Authors: Darabi J. , Wang H.
Published: May 2008

Cryogenic cooling has become a widely adopted technique to improve the performance of electronics and sensors. A potential application of an electrohydrodynamic (EHD) pumping system is its use in pumping fluids in cryogenic cooling systems. In this paper we present the results of a theoretical/experimental investigation to study the feasibility of using an EHD injection micropump for pumping liquid nitrogen. First, the mechanisms of charge transport and ionization phenomenon in cryogenic liquids are discussed. Next, the design and fabrication of an EHD injection micropump that employs an array of interdigitated saw-tooth/plane electrodes are described. Finally, experimental results and observations are presented. An asymmetric saw-tooth/plane geometry was designed to achieve strong inhomogeneous electric field. Each saw-tooth had a base length of 10 μm with a tip angle of 60°. The gap between emitter and collector electrodes was 20 μm and the distance between each stage (a pair of emitter and collector electrodes) from neighboring stage was 40 μm. The dimensions of the patterned area were 10 mm by 20 mm allowing approximately 300 stages to be fabricated along the length of the micropump. The maximum pressure head achieved by this micropump was 550 Pa and 205 Pa for HFE-7100 and liquid nitrogen, respectively.
Generation of Rough Design Plans for Mechanical Products Using a Module Library
Authors: Matsuda Michiko , Naoda Yuki , Kimura Fumihiko
Published: May 2008

In this paper, a preliminary design support system for mechanical products is proposed. The preliminary design stage, in which rough design plans are generated, can be supported by a mechanism for automatic translation from functional requirements to modules and by optimization of arrangements in a module combination set. A module library is proposed as a mechanism for automatic translation. In this library, relationships among functional requirements, primitive functions and modules are represented in a hierarchical class description. The module combination sets that satisfy the functional requirements are generated from selected modules by referencing the module library. A genetic algorithm is applied to optimization of module arrangements in each combination set. Several module arrangements which satisfy functional requirements are obtained. These arrangements offer a rough design plan for the product. A trial implementation of the above procedure is applied to “Lego Mindstorms” a building block kit for toy robots.
Methanol Oxidation Induction Times Using the Rate-Controlled Constrained-Equilibrium Method
Authors: Ugarte Sergio , Metghalchi Mohamad , Keck James C.
Published: May 2008

Methanol oxidation has been modeled using the Rate-Controlled Constrained-Equilibrium method (RCCE). In this method, composition of the system is determined by constraints rather than by species. Since the number of constraints can be much smaller than the number of species present, the number of rate equations required to describe the time evolution of the system can be considerably reduced. In the present paper, C1 chemistry with 29 species and 140 reactions has been used to investigate the oxidation of stoichiometric methanol/oxygen mixture at constant energy and volume. Three fixed elemental constraints: elemental carbon, elemental oxygen and elemental hydrogen and from one to nine variable constraints: moles of fuel, total number of moles, moles of free oxygen, moles of free oxygen, moles of free valence, moles of fuel radical, moles of formaldehyde H2CO, moles of HCO, moles of CO and moles of CH3O were used. The four to twelve rate equations for the constraint potentials (LaGrange multipliers conjugate to the constraints) were integrated for a wide range of initial temperatures and pressures. As expected, the RCCE calculations gave correct equilibrium values in all cases. Only 8 constraints were required to give reasonable agreement with detailed calculations. Results of using 9 constraints showed compared very well to those of the detailed calculations at all conditions. For this system, ignition delay times and major species concentrations were within 0.5% to 5% of the values given by detailed calculations. Adding up to 12 constraints improved the accuracy of the minor species mole fractions at early times, but only had a little effect on the ignition delay times. RCCE calculations reduced the time required for input and output of data in 25% and 10% when using 8 and 9 constraints respectively. In addition, RCCE calculations gave valuable insight into the important reaction paths and rate-limiting reactions involved in methanol oxidation.
Modeling of Waste-to-Energy Combustion With Continuous Variation of the Solid Waste Fuel
Authors: Nakamura Masato , Zhang Hanwei , Millrath Karsten , Themelis Nickolas J.
Published: May 2008

A mathematical model of a mass-burn, waste-to-energy combustion chamber has been developed that includes stochastic representation of the variability of the fuel (municipal solid waste, MSW). The drying, pyrolysis, gasification and combustion processes on the moving grate are governed by several factors such as proximate and ultimate analysis, particle size, moisture, heating value, and bulk density, all of which change continuously. This extreme variability has not been considered in past mathematical models of WTE combustion that used mean values of the MSW properties. The Monte Carlo stochastic method has been applied to provide a time series description of the continuous variation of solid wastes at the feed end of the traveling grate. The combustion of the solid particles on the grate is simulated using percolation theory. The feed variation and the percolation theory models are combined with the FLIC two-dimensional bed model developed by Sheffield University to project the transient phenomena in the bed, such as the break-up of waste particles and the channeling of combustion air throughout the bed, and their effects on the combustion process.
Application of Higher-Order Compact Finite Difference Schemes to Out of Plane Vorticity Measurements
Authors: Etebari Ali , Vlachos Pavlos P.
Published: May 2008

The accuracy of out-of-plane vorticity from in-plane experimental velocity measurements is investigated with particular application to Digital Particle Image Velocimetry (DPIV). Higher-order compact finite difference schemes are proposed as alternatives for the vorticity estimation. Simulations of known flow fields are used to quantify errors associated with the different methods of estimation. The effects of spatial sampling resolution with respect to the range of flow scales on the bias errors of the method accuracies are explored. In addition, estimation of the velocity measurement random error propagation into the vorticity measurement is presented. The higher-order compact schemes deliver improved accuracy compared with previously used methods, even when that domain is spatially undersampled or in the presence of strong velocity gradients. The compact schemes demonstrated less than 0.3% bias error throughout the core of the vortex, resolving flow structures as small as the Nyquist sampling frequency of the system, while the error in the conventional methods increased as the spatial sampling and the range of wave numbers present in the flow field was reduced. The bias error is an irrecoverable loss due to the truncation error of the method, and thus poses significant limitations to the system, whereas the random error propagation can be reduced for the higher-order schemes by applying a simple Gaussian smoothing to the flow field. Thus, the reduction in bias error is of greater importance to the accuracy of the system, particularly as modern global flow measurement technologies achieve higher spatial and temporal resolutions, as well as higher accuracies in velocity measurements. Overall, the compact schemes provide an improved approach for vorticity evaluation compared to conventional algorithms.
On the Challenges of Quieting a Freight Locomotive Cab Interior
Authors: Ahmadian Mehdi
Published: May 2008

The primary purpose of this paper is to discuss some of the challenges—both from an engineering standpoint and economically—facing the railway industry in improving the noise and vibration characteristics in locomotive cabs. To this end, we will first establish the vibration characteristics of a typical locomotive cab used in freight locomotives in North America. Next, we will evaluate the effect of separating the cab structure from the reminder of the locomotive structure by elastomeric mounts. This cab configuration is commonly referred to as “soft-mounted cab,” in contrast to a “hard-mounted cab,” which is rigidly attached to the remainder of the locomotive structure. The structural dynamics of a production locomotive cab is studied in a laboratory environment. The cab is excited by a hydraulic actuator, in a manner closely resembling field inputs. After establishing the baseline vibrations of the cab, the study presents the results of vibration tests for the soft mounted cab. A comparison between the hard-mounted and soft-mounted cabs indicate that soft mounting the locomotive cab can result in substantial noise and vibration reduction at all locations in the cab, and therefore provide: • more crew comfort, • less equipment damage, and • manufacturing cost savings. The paper will also discuss the effect of the measures that are needed for quieting the cab, such as soft mounting it, on the locomotive manufacturers from an engineering and business perspective.
Online Analysis of Textile Card Web Density
Authors: Saxena Abhinav , Dorrity Jordan L. , Wang Youjiang
Published: May 2008

One area of research at Georgia Tech recently has focused on the measurement of Card-web density. This research is part of a study to spin yarns directly from a card web thus eliminating several processes. A Card-Spinning system has been designed which can quantify the cross-machine and machine direction web non-uniformity using a non-contact web density measurement technique. The web monitoring system for Card-Spinning uses a line scan camera to capture the image continuously and is equipped with an image analysis program, to characterize the web quantitatively, predicting the product quality. A multifunctional graphical interface has been designed for the image analysis program, which can be used to calculate the statistics for the non-uniformity of the card web both online and offline. This would help in characterizing the nature of non-uniformity and to understand the system better before employing methods to improve it. This paper discusses the development and results from the work.
A Decomposition Strategy Applied to the Optimal Synthesis/Design and Operation of an Advanced Fighter Aircraft System: A Comparison With and Without Airframe Degrees of Freedom
Authors: Rancruel Diego F. , von Spakovsky Michael R.
Published: May 2008

A decomposition methodology based on the concept of “thermoeconomic isolation” applied to the synthesis/design and operational optimization of an advanced tactical fighter aircraft is the focus of this research. Conceptual, time, and physical decomposition were used to solve the system-level as well as unit-level optimization problems. The total system was decomposed into five sub-systems as follows: propulsion sub-system (PS), environmental control sub-system (ECS), fuel loop sub-system (FLS), vapor compression and PAO loops sub-system (VC/PAOS), and airframe sub-system (AFS) of which the AFS is a non-energy based sub-system. A number of different configurations for each sub-system were considered. The most promising set of candidate configurations, based on both an energy integration analysis and aerodynamic performance, were developed and detailed thermodynamic, geometric, physical, and aerodynamic models at both design and off-design were formulated and implemented. A decomposition strategy called Iterative Local-Global Optimization (ILGO) developed by Mun˜oz and von Spakovsky (2000b,c) was then applied to the synthesis/design and operational optimization of the advanced tactical fighter aircraft. This decomposition strategy is the first to successfully closely approach the theoretical condition of “thermoeconomic isolation” when applied to highly complex, highly dynamic non-liner systems. This contrasts with past attempts to approach this condition, all of which were applied to very simple systems under very special and restricted conditions such as those requiring linearity in the models and strictly local decision variables. This is a significant advance in decomposition and has now been successfully applied to a number of highly complex and dynamic transportation and stationary systems. This paper presents the detailed results from one such application, which additionally considers a non-energy based sub-system (AFS).
Non Linear Systems Under Complex α-Stable Le´vy White Noise
Authors: Di Paola M. , Vasta M.
Published: May 2008

The problem of predicting the response of linear and nonlinear systems under Le´vy white noises is examined. A method of analysis is proposed based on the observation that these processes have impulsive character, so that the methods already used for Poisson white noise or normal white noise may be also recast for Le´vy white noises. Since both the input and output processes have no moments of order two and higher, the response is here evaluated in terms of characteristic function.
Triaxial Failure of Aluminium Foams
Authors: Ruan D. , Lu G. , Wang B.
Published: May 2008

Aluminium foam is a type of cellular materials and offers potential for lightweight structures and energy absorbers in automotive and aerospace industries. They may be subject to multiaxial loads in these applications and it is essential to have a failure criterion in terms of the stresses which cause yield. Three criteria have been proposed so far. Gibson and Ashby deduced a yield surface by using dimentional arguments for ideal, isotropic, homogenous foams. Miller’s yield surface was based on the model of Drucker and Prager, which was originally proposed as a model for soil. It incorporated a linear and quadratic dependence on the pressure. Deshpande and Fleck modified the yield criterion of solid metals to account for the effect of porosity on the yield criterion for a metallic foam. In this paper, triaxial tests of CYMAT aluminium foams were conducted by using MTS (Mechanical Test System) with a Hoek Cell to investigate their yield surfaces experimentally. Five types of aluminium foams with nominal relative densities. of 5%, 10%, 15%, 17% and 20% were tested for a range of axisymmetric compressive stress states. Experimental results were compared with three theoretical criteria. Triaxial tests at various strain rates (from 10−4 to 10+1 s−1) were also performed in this paper to investigate the influence of strain rate on the yield surface.