bluuebunny/crossref_metadata_2025 huggingface dataset:
Active Water Management for Proton Exchange Membrane Fuel Cells Using an Integrated Electroosmotic Pump
Authors: Buie Cullen R. , Posner Jonathan D. , Fabian Tibor , Cha Suk-Won , Prinz Fritz B. , Eaton John K. , Santiago Juan G.
Published: April 2008

We have developed proton exchange membrane fuel cells (PEMFC’s) with integrated planar electroosmotic pumping structures that actively remove liquid water from cathode flow channels. Recent experimental and numerical investigations on PEMFC’s emphasize water management as a critical factor in the design of robust, high efficiency fuel cells. Although various passive water management strategies have been proposed, water is still typically removed by pumping air into cathode channels at flow rates significantly larger than those required by fuel cell stoichiometry. This method of water removal is thermodynamically unfavorable and constrains cathode flow channel design. EO pumps can relieve cathode design barriers and simplify water management in fuel cells. EO pumps have no moving parts, scale across a wide range of operation, and result in low parasitic power. We demonstrate and quantify the efficacy of EO water pumping using a single-pass fuel cell test channel. Our results show that removing water from the cathode using integrated EO pumping structures improves fuel cell performance and stability. These pumps enable operation with air flow rates of just two to three times stoichiometric requirements.
Experimental Investigation of the Machinabilty of Polycarbonate Reinforced With Multiwalled Carbon Nanotubes
Authors: Samuel Johnson , DeVor Richard E. , Kapoor Shiv G. , Hsia K. Jimmy
Published: April 2008

The machinability of a polycarbonate nanocomposite containing multiwalled carbon nanotubes is investigated and contrasted with its base polymer and with a conventional carbon fiber composite. The material microstructures are characterized using transmission electron and scanning electron microscopy methods. Micro end milling experiments are conducted on the three materials. Chip morphology, machined surface characteristics and the nature of the cutting forces are employed as machinability measures for comparative purposes. Polycarbonate chips are seen to transition from being discontinuous to continuous as the feed-per-tooth (FPT) increases, while, at all FPT values the nanocomposite is seen to form comparatively thicker continuous chips. The nanocomposite and the carbon fiber composite are seen to have the lowest and the highest magnitudes, respectively, for both the surface roughness and cutting forces. Shearing along the nanotube-polymer interface and better thermal conductivity are speculated to be the mechanisms responsible for the observations seen in the nanocomposite.
Experimental Simulation of Piston Leakage in an Axial Piston Pump
Authors: Li Zeliang , Burton Richard , Nikiforuk Peter
Published: April 2008

A method used to introduce “artificial leakage” into an axial piston pump to simulate leakage from a worn piston is described in this paper. A pressure control servo valve with a very high frequency response was employed to divert flow from the pump outlet in a prescribed waveform directly to tank. The purpose was to simulate piston leakage from the high pressure discharge chamber to the pump case drain chamber as the “simulated worn piston” made contact with the high pressure chamber. The system and associated control algorithms mimiced the action of a single worn piston at various degrees of wear. The experimental results indicated that the experimental system could successfully introduce artificial leakage into the pump which was consistent with a unit with a “real” worn piston. Comparisons of the pressure ripples from an actual faulty pump (with one worn piston) and the artificial faulty pump (with one simulated worn piston) are presented.
Thermal Compensation Algorithm for Machine Tool
Authors: Kushnir E.
Published: April 2008

Thermal effects can contributed more than 50% of the overall error in a machine tool and as precision requirements continue to grow the necessity of reducing this error source is essential. Today’s CNC allow to perform indirect compensation of these errors based on temperature measured in different points of machine tool structure. The efficiency of thermal compensation may be measured as a ratio between capability of machining process before and after applying thermal compensation. The proposed methodology of thermal compensation algorithm development is based at testing and FEA. The efficiency of proposed approach is illustrated by compensation algorithm, developed for different type of lathe. The application of thermal compensation allowed to increase capability of machining process more the two times. The accumulated experience in thermal compensation development provides ways for further improvement of lathe machining process capabilities.
Heat Conduction in Three Dimensional Stacked Packages
Authors: Desai Anand , Geer James , Sammakia Bahgat
Published: April 2008

This paper presents the results of an analytical study of steady state heat conduction in multiple rectangular domains. Any finite number of such domains may be considered in the current study. The thermal conductivity and thickness of these domains may be different. The entire geometry composed of these connected domains is considered as adiabatic on the lateral surfaces and can be subjected to uniform convective cooling at one end. The other end of the geometry may be adiabatic and a specified, spatially varying heat generation rate can be applied in each of the domains. The solutions are found to be in agreement with known solutions for simpler geometries. The analytical solution presented here is very general in that it takes into account the interface resistances between the layers. One application of this analytical study relates to the thermal management of a 3-D stack of devices and interconnect layers. Another possible application is to the study of hotspots in a chip stack with non uniform heat generation. Many other potential applications may also be simulated.
Optimization of a Star Pattern Recognition Algorithm for Attitude Determination Using a Multi-Objective Genetic Algorithm
Authors: Seisie-Amoasi Ebenezer , Williams Brian G. , Schoen Marco P.
Published: April 2008

Attitude determination for unmanned spacecrafts usually employs star trackers. The specifications for these devices dictate fast, reliable, robust, and autonomous algorithms to satisfy various mission constraints. This results into simple algorithms for reduced power consumption and reduced overall weight. Optimizing a Star Pattern Recognition Algorithm (SPRA), using an imbedded star map, requires the optimization of the genetic operators that constitute the SPRA and the control parameters within the SPRA. Simultaneous optimization of the control parameters of the SPRA results into a multi-objective and multi-parameter constrained optimization problem. The optimizing of genetic algorithms is often time consuming and rather tedious by nature. In this work, a Multi-Objective Genetic Algorithm (MOGA) acting as a meta-level GA is applied together with a double objective transition selection scheme to achieve the optimization. This approach results in significantly expediting the cost assignment process. By evolving a pareto set, an optimization population element rule is determined to exist between the control parameters of the SPRA. The existence of this rule ensures effective balance between population exploitation and exploration in the algorithm estimation process. This leads to effective solutions for finding the optimum with multiple concurrent objectives while taking the constraints into consideration. Simulation results using the optimized parameters for the SPRA indicate an improvement of the recognition accuracy from less than 60% to 100% as well as a reduction of the processing time of over 2000 generations to under 250 generations at 99% precision.
Improved Accuracy of an Ultrasonic Based Neuro-Navigation System Using Neural Networks
Authors: Akers Jennifer , Chitikeshi Sanjeevi , Mahajan Ajay , Lal Sumeer
Published: April 2008

This paper presents the design and development of an ultrasonic based neuronavigation system to be used for real time surgery. The system formulation, hardware and a neural network model is presented that improves the accuracy of the system considerably. 1D, 2D and 3D results from the neural network model are presented along with designs for the physical and electronic hardware. The 3D system presented in this paper eliminates the space intensive camera, has an accuracy better than 1.0 mm in the operating range of about 20–40 cm, makes the system independent of line-of-sight occlusion problems, and is expected to pave the way for accurate fusion models of the future that may account for brain shifts during surgery. The results show that the performance of the proposed system provides many advantages over existing neuro-navigation systems without compromising on the accuracy.
Numerical Investigation of Heat Partition in the Primary Shear Zone in Metal Cutting
Authors: Pednekar Vasant , Madhavan Vis , Adibi-Sedeh Amir H.
Published: April 2008

The fraction of heat generated in the primary shear zone that is conducted into the workpiece is a key factor in the calculation of the shear plane temperature and in calculating the cutting forces based on material flow stress. Accurate analytical, numerical, or experimental determination of this heat partition coefficient is not available to date. This study utilizes a new approach to obtain the heat partition coefficient for the primary shear zone using results for strain, strain rate, and temperature distribution obtained from a coupled thermo-mechanical finite element analysis of machining. Different approaches, using strain rate and equivalent strain, are used for calculating the total plastic power in the primary shear zone and the heat generated by plastic deformation below the plane of the machined surface. The heat carried away by the workpiece is obtained by calculating the heat flow by convection in regions where the conduction is expected to be small. We have used an elastic perfectly plastic material model and constant thermal properties to mimic the assumptions used in analytical models. The fraction of the total heat generated in the primary shear zone that is conducted into the machined workpiece is found and compared to the prediction of different analytical models. It is found that for most of the cutting conditions, the values of heat partition coefficient are closest to those provided by Weiner’s model.
Stability and Bifurcation Analysis of a Forced Cylinder Wake
Authors: Mureithi N. W. , Rodriguez M.
Published: April 2008

We present a study on the dynamics of a cylinder wake subjected to forced excitation. Williams et al. (1992) discovered that the spatial symmetry of the excitation plays a crucial role in determining the resulting wake dynamics. Reflection-symmetric forcing was found to affect the Karman wake much more strongly compared to Z2(κ, π) asymmetric forcing. For low forcing amplitudes, the existence of a nonlinear mode interaction mechanism was postulated to explain the observed “beating” phenomenon observed in the wake. Previous work by the authors (Mureithi et al. 2002, 2003) presented general forms of the modal interaction amplitude equations governing the dynamics of the periodically forced wake. In the present work, numerical CFD computations of the forced cylinder wake are presented. It is shown that the experimentally observed wake bifurcations can be reproduced by numerical simulations with reasonable accuracy. The CFD computations show that the forced wake first looses reflection symmetry followed by a bifurcation associated with vortex merging as the forcing amplitude is increased. A bifurcation analysis of a simplified amplitude equation shows that these two transitions are due to a pitchfork bifurcation and a period-doubling bifurcation of mixed mode solutions.
Enhancement of Heat Transfer Due to Plasma Flow in Material Processing Applications
Authors: Rajamani V. , Anand R. , Reddy G. S. , Sekhar J. , Jog M. A.
Published: April 2008

Convective heating is used in materials processing industry for heat treatment and melting applications. Only recently, a new plasma device for convective heating at atmospheric pressure has become commercially available. In this paper, we have investigated heating of an aluminum sprue by conventional convective heating by air and by plasma flow. Transient temperature measurements were made in the sprue interior and the overall heat transfer coefficient was computationally predicted in the two cases. Results show that there is significant enhancement of heat transfer in convective plasma heating compared to heating due to unionized gas under identical flow and temperature conditions. For the cases considered in this study, close to a 60% increase in the heat transfer rate was obtained. The key finding is that even small amount of ionization (~ < 1%) can lead to significant increase in heat transfer coefficient.
Active Foot Pressure Control for Diabetic Neuropathy During Walking
Authors: Nandikolla Vidya K. , Schoen Marco P. , Mahajan Ajay
Published: April 2008

Diabetic Mellitus is a disease caused either due to insufficient insulin produced by the pancreas or the body cells are unable to use the existing insulin. One of the main complications associated with diabetics is neuropathy, which is caused due to complete or partial loss of sensation in the feet and legs that lead to problems like inadequate delivery of nutrients and oxygen to the foot, which will cause healing impairment. In diabetic neuropathic subject, the hardness of foot sole soft tissue gives rise to plantar ulcer development. In this work, a biomechanical model is used to study the plantar distribution of forces in the foot. The dynamic foot pressure distribution during walking is used to carry out a stress analysis. This includes the motion of heel strike, mid-stance, and push off section of the feet during walking. A control strategy is proposed to mitigate the high stress concentration occurring during the walking phase. The control strategy includes a synergy of an adaptive neuro-fuzzy inference controller and for comparison an optimal controller. The actuation is simulated through an external shoe insert. The three-dimensional multi-segment biomechanical model is used in conjunction with experimental data gathered from various literatures for simulation purposes of the proposed control strategy. The proposed intelligent controller focuses on stresses generated by the foot pressure distribution during walking and compares these with stress levels of healthy subjects. The insert changes its shape accordingly to redistribute the pressure levels at various regions so to achieve a pressure distribution equivalent to a healthy subject. It is assumed that the insert can actuate and measure the pressure distribution simultaneously. This could be achieved using smart materials for the shoe insert. The simulation results show the effectiveness of the proposed algorithms and approach.
Acoustic Cloud Condensation Nuclei Counter
Authors: Deshpande Abhijit , Zahui Marcellin
Published: April 2008

Analysis and simulation of an acoustic cloud condensation nuclei counter is presented. The instrument is capable of accurately counting the number of micro scale water droplets impacting a water surface. The sound produced underwater by the water droplets is determined when the droplets strike the water surface with an impact velocity equal to either their terminal or maximum velocity. First, the terminal velocities of the droplets are calculated using Stoke’s law and compared to measured velocities from Gunn and Kinzer. Then the maximum velocities that these droplets can sustain without breaking are calculated as a function of droplet diameter. Second, the sound due to droplet impact is estimated. Due to their size and water surface tension, there is no bubble formation at impact when the droplets are falling with terminal velocities. However conditions for regular bubble entrainments are established and limit velocities are calculated. Assuming that the micro water droplets can be accelerated, the maximum velocities for no bubble entrainments are calculated. The results show that the level of the sound produced by individual micro scale droplet falling with terminal velocity is so small that experimental verification is not possible. However, reasonable level of acoustic energy can be obtained by increasing the impact velocities of the droplets or by measuring the sound radiated by a group of impacting droplets. Finally, the droplets counting process is simulated using a water surface of one centimeter squared and a vertical growth chamber.
Characterization and Analysis of Low Profile Plate-Fin Heat Sinks for Advanced Thermal Packaging of Consumer Electronics
Authors: Yazawa K. , Yoshida T. , Nakagawa S. , Ishizuka M.
Published: April 2008

Thermal performance in conjunction with fluid dynamic characterization and analysis on low profile heat sink was carried out. Regardless to the increasing power of VLSI chip, recent advanced packaging for compact and slim enclosure for consumer electronics requires a low profile heat sink with a small space available for cooling fan that limits the power of pumping airflow. Therefore, highly integrated fins for low profile heat sink become important to be characterized and modeled. Such low profile and high fin density heat sink has non-ideal shape for shrouding that has not been modeled yet. Proposed semi-bypass model particularly for the practical application of such heat sink is discussed with experimental results and numerical analysis. The apparatus is designed to measure both thermal and fluid dynamic characteristics at the same time. The results are compared based on tested range and found in good agreement at near optimum design. With utilizing this analytic model, cooling performance is optimized with fin number for given pumping power. To understand the shroud impact, these heat sinks are compared with similar foot print and conventional open fin heat sinks which have been already characterized. In addition, semi-bypass impact is also compared with ideally full shroud case in the model. Interestingly, this semi-bypass design is found slightly better than full shroud heat sinks in terms of the performance for same given pumping power.
Coating Stresses in Thermal Barrier Coating by an In Situ Curvature-Monitoring Technique
Authors: Arai Masayuki
Published: April 2008

In this paper, coating stresses in thermal barrier coating (TBC) changing with a cyclic heating - cooling are measured with a curvature measurement device developed in this study. Coating system chosen in this study is dual-layered structure, and it consists of a partially stabilized zirconia (PSZ) as ceramic coating layer and CoNiCrAlY as metal-bond coating layer. The specimen used here is a strip-plate shape with thin thickness (600μm) extracted chemically from a thermal spraying coated carbon steel. Cyclic heating-cooling test and cyclic heating-cooling test with a dwelling time at a maximum temperature are conducted for the strip-plate specimen. Deflection and coating stresses are measured continuously under these cyclic tests, and thermal deformation mechanisms generating the deflection and coating stresses will be discussed based on a primitive knowledge by an elementary beam theory.
Design of Hybrid-Driven Servo Press Mechanism
Authors: Tso Pei-Lum , Li Cheng-Ho , Ke Jyun-Huang
Published: April 2008

Servo presses are notably developed and studied nowadays out of their flexible ram motion. In practice, press users can advantageously utilize a single servo press to deal with different stamping operations such as blanking, drawing, coining, embossing, etc. In this paper, a hybrid-driven servo press mechanism is studied. The mechanism for such servo presses is a seven-bar linkage whose degree of freedom (DOF) is “2”. Two input links of the press mechanism are driven by one normal constant-speed motor and one servo variant-speed motor respectively. The dimensional synthesis of the press mechanism that is based on an analytical method is proposed. The motion function of the servomotor that generated a specified ram motion is derived by kinematic analysis. A design example is illustrated, and it shows that one could apply the proposed method to design a hybrid-driven press mechanism capable of carrying out various ram motions. This work contributes to press mechanism designers a method of dimensional synthesis. The ram motion flexibility of the servo press is achieved, and this provides significant benefit to improve the performance of any different kind of stamping operations.
Dynamics of Multiply Expansion Bellows With Elastically Restrained Ends
Authors: Kameswara Rao C. , Radhakrishna M.
Published: April 2008

The paper presents study of the dynamic aspects of the multiply bellows with elastically restrained ends and under rotatory inertia. The influence of rotational restraint and internal pressure loading on dynamic response of such bellows configuration has been attempted here. An attempt has been made here to establish relations that are simple and compatible in computing the frequency of bellows. The “Rayleigh Quotient”, method is used for this purpose. The coupled responses obtained are compared with exact analysis for multiply configuration. Two cases are considered — bellows having same material and different materials for plies.
Passive Control of a Rectangular Plate Using Strategic Cut-Outs
Authors: Ulz Manfred H. , Semercigil S. Eren
Published: April 2008

Perforations and cut-outs are widely used in plates and shells to facilitate heat dissipation, and to provide access to different components. It is generally expected that the dynamic behavior will deteriorate because of the presence of the cut-out. As a result, vibrations due to an external excitation will be larger than those of the case without a cut-out. Summary of a numerical study is presented in this paper to investigate the possibility of making a rectangular cut-out for the purposes of employing this cut-out as a Dynamic Vibration Absorber. The concept is similar to that of the classical case. However, instead of adding an auxiliary structure, the part of the plate is suggested to act as an absorber in the form of a “designed” cut-out. The process involves numerical modeling using standard finite elements. The plate is excited with an impact force to insure the participation of the multiple modes of vibration. The numerical predictions are presented in the form of design charts to indicate the conditions under which vibration control may be possible.
Energy Dissipation with Sloshing for Absorber Design
Authors: Guzel Birhan U. , Prakash Mahesh , Semercigil Eren , Turan Ozden
Published: April 2008

Sloshing is the low frequency oscillation of the free surface of a liquid in a partially full container. Due to its detrimental effects, efforts are usually made in the direction of suppressing sloshing. In addition, intentionally induced sloshing may be employed as an effective energy sink to provide protection for resonant structures exposed to excessive vibration levels. It is generally reported that sloshing absorbers with shallow levels of liquid are more effective energy dissipators than those with deep levels. However, there has not yet been a study to reveal the mechanism of energy dissipation for practical applications, although there has been ample empirical proof for effectiveness. One of the limitations from a numerical perspective lies with the difficulty in predicting extreme free surface behaviour by traditional grid based computational methods. The objective of this paper is to report initial observations in this direction using Smoothed Particle Hydrodynamics (SPH). SPH is a Lagrangian method of solving the equations for fluid flow, that is suitable for modeling free surface phenomena such as sloshing due to its grid-free nature. Results are reported in this paper in the form of numerical case studies.
Design and Fabrication of a Cascaded Electro-Thermal Bimorph Actuator
Authors: Lin Cheng-Hsuan , Yeh Cheng-Chi , Hsu Chen-Peng , Hsu Wensyang
Published: April 2008

Here a cascaded bimorph actuator is proposed by integrating several novel actuation units to accumulate the vertical displacements. Each actuation unit comprises two types of bimorph beams and a constraint bar, and both beams will stretch outward with respect to the constraint bar while heating. In comparison with other three conventional bimorph actuator designs at the same device size, it is shown that the proposed design can provide larger vertical displacement. The proposed cascaded bimorph actuator is fabricated by surface micromachining technique and released by XeF2 silicon isotropic etching. Whole suspended structure consisting of the polysilicon and the aluminum is around 510 × 400 μm2 with four actuation units. The resistance is about 650 Ω. In testing, the fabricated device is shown to provide reversible vertical displacement of 22.5 μm at 4.5 V, and the operating temperature is measured by an infrared thermal microscope (InfraScope II, QFI). The calibrated maximum temperatures are compared with simulated results by ANSYS 6.0 in good agreement. It is found that the maximum temperature is 147 °C when the input voltage is 4.5 dc volts, and the maximum temperature is below 400°C even at 10 V. However, it is found that the residual stress in the suspended structure will affect the vertical displacement of the device.
Investigation of the Phenomena of Friction Induced Vibrations on Small-Scale Mechanical Systems
Authors: Mbumba Tony Tuzolana , De Baets Patrick , Gert Desmet
Published: April 2008

This paper presents the experimental investigation of the concept of friction-induced vibrations observed in small-scale mechanical systems. A mesoscopic flat-on-flat tribotester, simulating as close as possible the behaviour of a microfluidic device, was designed and built and sliding tests on polyamide materials sliding on steel were performed in ambient atmosphere using this mesoscopic flat-on-flat tribotester. The results of this investigation show that these phenomena can also occur in small-scale system as it occurs in macro-scale system. This concept is due to: the interaction between mechanical parameters and tribological properties of the two sliding surfaces and the existence of two friction: static and kinetic friction so that the transition from one to another can be accompanied with vibrations. The results of this investigation confirm also the general trends that: stick-slip vibrations occur generally at lower sliding velocity and quasi-harmonic vibrations at higher sliding velocity.
DC Potential Drop Technique Selecting Probes Distances Properly for Sizing Deep Surface Cracks
Authors: Takeo Fumio , Saka Masumi , Hamada Seiichi , Hayakawa Manabu
Published: April 2008

D-C potential drop (DCPD) technique is a powerful tool for quantitative NDE of cracks. The technique using four probes which are in close proximity to each other has been proposed for NDE of surface cracks; that is the closely coupled probes potential drop (CCPPD) technique. It has been shown that the sensitivity of CCPPD technique to evaluate a small crack is enhanced significantly in comparison with the usual method. On the other hand, since CCPPD technique has been developed to evaluate a small crack sensitively, it is not fit to evaluate deep cracks which are sometimes found in the structural components of power plants. The objective of this study was to enhance the sensitivity of evaluating deep surface cracks. By extending the distance between current input and output probes, the change in potential drop with the change in the depth of deeper crack becomes large. But the voltage of potential drop becomes small to measure, because the current density in the material becomes low. The voltage of the potential drop can be increased by increasing the applying current, but the current would also be limited by the equipment or contacting probes. Then the way to select the appropriate distances between probes from the viewpoints of the sensitivity and the required current has been shown.
Virtual Functional Build for Body Assembly
Authors: Gerth Richard J.
Published: April 2008

Functional build (FB) is a critical process in launching a vehicle, whereby individual prototype parts are stamped and then sent to a central location to be assembled into a prototype vehicle body. FB is premised on the realization that from a functional viewpoint the relationship between parts is important, not the relationship of the parts to their respective nominal dimensions. FB has been widely adopted in the automotive industry, and the financial benefits have been large and well documented. This paper describes Virtual Functional Build (VFB) where point cloud representations of parts are assembled virtually using assembly modeling software. The potential benefits of VFB over traditional FB techniques are reduced capital investment in tooling and, more importantly, reduced lead time due to earlier collaboration between geographically remote part and sub-assembly suppliers. This paper will contrast the FB and VFB processes on an actual automotive case study.
Distributed Adaptive Optimization in Virtual Body Assembly
Authors: Gerth Richard J. , Brueckner Sven
Published: April 2008

The Digital Body Development System (DBDS) is 4 year project to shorten the time to launch vehicles by improving the launch problem solving process. The project is based on two concepts: virtual functional build and an intelligent agent based decision support system. This paper presents a novel architecture for the decision support system that streamlines the launch process through the integration of a virtual assembly simulation, problem identification, and solution generation and evaluation. Following the virtual functional build process, the architecture deploys a number of multi-agent systems to provide system functionality, such as problem knowledge retrieval, solution generation, modification, and evaluation. The architecture has been implemented and will be explained on a simple 2-D door model and a casebase of 100 cases. Results show that the DBDS can find the correct solution much faster than a random search and can automatically implement and evaluate the solution.
Study on Tribological Properties of Cadmium Dialkyl-Dithiophosphyl-ldithiophosphate Additive
Authors: Hu Jianqiang , Du Zhanhe , Yao Junbing
Published: April 2008

An cadmium dialkyl-dithiophosphyl-dithiophosphate additive was synthesized. A four-ball tester was used to evaluate the tribological performance of the additive in mineral base oil under different loads, compared with commercial additives. The results show that it exhibits excellent antiwear and load-carrying capacities and better than these additives. The surface analytical tools such as Auger Electron Spectrometer (AES), Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) were used to investigate the topography, the contents and the depth profile of some typical elements on the rubbing surface of worn scar. Smooth and light topography of worn scar further confirms that the additive showed good antiwear capacities, the results of Auger electron spectrometer and energy dispersive X-ray analysis indicate that tribochemically protective films consists of cadmium compouds, sulfides, sulphates and phosphates were formed on the rubbing surface, which contribute to improving the tribological properties of lubricants. Particularly, the results from depth profile indicate that a large amounts of cadmium are rich in outer layer of surface, which play an important role in improving antiwear properties of oils. Finally, the antiwear mechanism of the additive were proposed.
Recent Advances in Micro/Meso-Scale Manufacturing Processes
Authors: Williams Robert E. , Huang Yong , Melkote Shreyes , Kinsey Brad , Sun Wei , Yao Donggang
Published: April 2008

The development of new manufacturing processes and process enhancements at the micro/meso-scale has expanded considerably in recent years due to the demand for miniaturized products. With this increased demand comes a critical need for a fundamental understanding of the role these reduced length scales play in the various process mechanisms. Significant research has been recently performed on a wide range of micro/meso-scale manufacturing processes to understand the role of the tribological effect, size effect and other mechanisms on process performance. This paper reviews the research and state-of-the-art for micro/meso-scale mechanical cutting and related machine technologies, micro-EDM, laser micro-machining and laser shock peening, microforming, and micro-scale bio-manufacturing and polymer fabrication. These latter areas may be of particular interest as they have not received as much attention as the traditional process areas.
Comparison of Numerical Models for Gear Tooth Root Fatigue Assessments
Authors: Jelaska Damir T. , Podrug Srdjan , Glodez Srecko
Published: April 2008

A several kinds of numerical models, including moving force model, for determination the service life of gears in regard to bending fatigue in a gear tooth root, is presented. The critical plane damage model, Socie and Bannantine [1], 1988, has been used to determine the number of stress cycles required for the fatigue crack initiation. This method determines also the initiated crack direction, what is good base for a further analyses of the crack propagation and the assessment of the total fatigue life. Finite element method and linear elastic fracture mechanics theories are then used for the further simulation of the fatigue crack growth under a moving load. Moving load produces a non-proportional load history in a gear’s tooth root. An approach that accounts for fatigue crack closure effects is developed to propagate crack under non-proportional load. Although some influences (non-homogeneous material, traveling of dislocations, etc.) were not taken into account in the computational simulations, the presented model seems to be very suitable for determination of service life of gears because numerical procedures used here are much faster and cheaper if compared with the experimental testing. The computational results are compared with other researchers’ numerical results and with service lives of real gears. The fatigue lives and crack paths determined in this paper exhibits a substantial agreement with experimental results and significant improvement compared with the existing numerical models.
Computational Methods to Predict and Avoid Design Failure
Authors: Mitchell Brian A. , McAdams Daniel A. , Stone Robert B. , Tumer Irem Y.
Published: April 2008

Component selection can be a difficult task for designers, and the components they choose can have a large impact on the robustness of the design. Using previous methods to predict and identify potential failure modes, known as the function-failure design method (FFDM), the impact on failure of selecting a particular component over another can be explored based on failure results from previous design endeavors using the same component. This assists designers in selecting the component that is best suited for the application. Since the predicted distribution of failure modes changes depending on the selected component, failure reduction is possible through component selection. Through this method of component selection, risk can be decreases and potential failures can be eliminated. Experiments based on undergraduate student competition design projects are presented to illustrate this method’s ability to predict failure modes. Initial results indicate that the predictions are accurate and meaningful to designers. The experiment also serves as initial validation previous work in the area of failure prediction.
Steady-Periodic Green’s Functions and Thermal-Measurement Applications in Rectangular Coordinates
Authors: Cole Kevin D.
Published: April 2008

Two-dimensional steady-periodic heat transfer in rectangles, slabs, and semi-infinite bodies is treated with the method of Green’s functions. The application is the measurement of thermal properties. Several types of boundary conditions are treated systematically, including convection conditions and boundaries containing a thin, high-conductivity film. Alternate forms of the Green’s function are given for several geometries, which allow for independent verification of numerical values. The method may be extended to multilayer bodies. Numerical examples are given for the steady-periodic response to a strip heater.
Modeling of Simultaneous Gas Absorption and Evaporation of Large Droplet
Authors: Elperin Tov , Fominykh Andrew , Krasovitov Boris
Published: April 2008

In this study we investigated numerically simultaneous heat and mass transfer during evaporation/condensation on the surface of a stagnant droplet in the presence of inert admixtures containing non-condensable solvable gas. The performed analysis is pertinent to slow droplet evaporation/condensation when Mach number is small (M≪1). The system of transient conjugate nonlinear energy and mass conservation equations was solved using anelastic approximation. Transport coefficients of the gaseous phase were calculated as functions of temperature and concentrations of gaseous species. Thermophysical properties of the liquid phase are assumed to be constant. Using the material balance at the droplet surface we obtained equations for Stefan velocity and the rate of change of the droplet radius taking into account the effect of solvable gas absorption at the gas-liquid interface. We derived also boundary conditions at gas-liquid interface taking into account the effect of gas absorption. The governing equations were solved using a method of lines. Numerical calculations showed essential change of the rates of heat and mass transfer in water droplet-air-water vapor system under the influence of solvable species in a gaseous phase. Consequently, the use of additives of solvable noncondensable gases to enhance the rate of heat and mass transfer in dispersed systems allows to increase the efficiency and reduce the size of gas-liquid contactors.
Formability Evaluation of Galvannealed (GA), Hot-Dip Pure Zn Galvanized (GI), Electrogalvanized (EG) and Electrogalvanized Prephosphated (EGP) Interstitial Free Steelaluation
Authors: Miranda W. J. , Carneiro J. R. G. , Brito P. P.
Published: April 2008

The formability of galvannealed (GA), hot-dip pure Zn galvanized (GI), electrogalvanized (EG), and electrogalvanized prephosphated (EGP) interstitial free (IF) steel sheets was studied. The phases in the Fe-Zn system were characterized using electronic and optic microscopy as well as X-ray diffraction. Behavior of the Zn coating when subjected to stretching, bending and drawing was also assessed. Comparison between the performance of large-scale industrial production of GA, GI, EG and EGP coated steels was made possible. The GI steels presented the best results, due to the predominantly basal crystallographic texture, lower friction coefficient with commercial oils and better press-forming response in the pressure range of 135-180kgf/cm2. It was also observed that the phosphate present in the EGP steels protected the structure of the EG coating, reducing the friction coefficient. Lastly, differences between the coatings, regarding stretching, bending and drawing, were confirmed.
An Introduction to Innovation Adoption Theories for the Design of a Product Family Information Management Infrastructure
Authors: Byron Bethany M. , Shooter Steven B.
Published: April 2008

As new computer technologies emerge for the design and development of product platforms, applied theories of innovation diffusion and technology acceptance will become increasingly important for securing user cooperation with an information management system for product families. Incorporation of human factors therein will shorten the time required to reach return on investment and increase the depth and breath of information. The history of innovation adoption theories are explored and extended to include commercially available enterprise management software and the proposed product family infrastructure. Six practices, which can be included in the infrastructure in its experimental stages, are described for improving user likelihood of adoption.
Rotating Instability in a Centrifugal Pump Impeller
Authors: Pavesi Giorgio , Ardizzon Guido , Cavazzini Giovanna
Published: April 2008

The objective of the study was the experimental and computational investigation of the unsteady flow in the centrifugal pumps. This paper analysed the effect of the vaneless stator interference on the exit flow field of a radial pump operated in the DIM facility. High-response pressure transducers were used to determine unsteady pressure field at three planes at the pump and at diffuser inflows. The experimental data showed that unsteady pressure disturbances modes change when the flow was reduced. Detailed analysis showed that disturbances occur at distinct frequencies and that these rotated in the circumferential direction. Comparison of the pressure signals measured at two circumferential locations on the casing confirmed the characteristic frequency pattern to be a so called “rotating instability”. This unsteady phenomenon was highlighted both at design flow rate and at low flow rates. The azimuthal distributions exhibited significant nonuniformities. The amplitude of this non-uniformity was sensitive to the flow rate. A simple model showed that, contrary to the common belief, the transport of the vane wake and secondary flows across the rotor was not enough to explain the magnitude of the variations. In this paper numerical investigations of the unsteady three-dimensional flow through the pump stage were also presented. Turbulence was modelled both by the k-ω transport equations model, and Reynolds Stress Model based on the ω-equation. The effects of the tip leakage flow were considered by meshing the tip clearance between rotor blade and casing. Results showed the jet-wake flow pattern induced an unstable vortex, which influenced flow discharging from the adjacent passage and destabilised jet-wake flow in the passage. Both calculations and measurements detected the periodic fluctuations at impeller discharge which were found to be coherent from blade to blade and possessed a rich harmonic content.
Direct Measurement of Slip Velocities Using Three-Dimensional Total Internal Reflection Velocimetry
Authors: Huang Peter , Guasto Jeffrey S. , Breuer Kenneth S.
Published: April 2008

The possible existence of slip of liquids in close proximity to a smooth surface is studied experimentally via the dynamics of small particles suspended in a shear flow. Sub-micron fluorescent particles suspended in water are imaged and analyzed using Total Internal Reflection Velocimetry (TIRV). For water flowing over a hydrophilic surface, the measurements are in agreement with previous experiments and indicate that slip, if present, is minimal at low shear rates, but increases slightly as the shear rate increases. Furthermore, surface hydrophobicity can be attributed for additional shear-rate dependent boundary slip. Issues associated with the experimental technique and the interpretation of results are also discussed.
Design of an Active Suspension Control for a Four DOF Model Using Genetic Algorithm
Authors: Gosselin-Brisson S. , Bouazara M. , Richard M. J.
Published: April 2008

This paper presents the design of an active suspension controller for an automotive vehicle. A four degrees of freedom linear model is used to represent a vehicle with different front and rear characteristics. Filtered road and acceleration inputs are applied to the model to simulate real life use. The performance criterion are filtered to include frequency sensitivity and weighted based on a standard passive suspension system. Independent front and rear controllers are optimised with the genetic algorithm. The controller includes linear gains and frequency dependency to take advantage of these two different control methods. The number of sensors and the order of the filters are limited to facilitate implementation on a real vehicle.
Fluid Flow and Heat Transfer in Power-Law Fluids Across Circular Cylinders: Analytical Study
Authors: Khan Waqar A. , Culham Richard J. , Yovanovich Milan M.
Published: April 2008

An integral approach of the boundary layer analysis is employed for the modeling of fluid flow around and heat transfer from infinite circular cylinders in power-law fluids. The Von Karman-Pohlhausenmethod is used to solve the momentum integral equation whereas the energy integral equation is solved for both isothermal and isoflux boundary conditions. A fourth-order velocity profile in the hydrodynamic boundary layer and a third-order temperature profile in the thermal boundary layer are used to solve both integral equations. Closed form expressions are obtained for the drag and heat transfer coefficients that can be used for a wide range of the power-law index, and generalized Reynolds and Prandtl numbers. It is found that pseudoplastic fluids offer less skin friction and higher heat transfer coefficients than dilatant fluids. As a result, the drag coefficients decrease and the heat transfer increases with the decrease in power-law index. Comparison of the analytical models with available experimental/numerical data proves the applicability of the integral approach for power-law fluids.
A Micromixer Based Upon Buoyancy
Authors: Walsh E. J. , Grimes R.
Published: April 2008

A novel micromixer is presented which may be thermally controlled to allow for the enhanced mixing of different species at the microscale. Numerical simulations are presented which demonstrate the operation of the design and methodologies for the generation of different microfluidic structures to enhance mixing at the microscale. It is found that buoyancy may be implemented to create a range of mixing regimes at the microscale. The generation of such fluidic structures allows the controlled mixing of different species
Extending Scenarios for Technology Development Planning in Power Generation
Authors: Franco Flavio J.
Published: April 2008

The Scenario Planning methodology has been applied by national and international institutions to long term studies of possible future evolutions of primary and final energy consumption, power generation capacity, emerging power generation technologies and green house gas emissions. Power generation equipment manufacturing companies are large enough to have considerable influence on how the future of the energy world will unfold, through their investment decisions in technology development. On the other hand, their future depends on external factors, out of their control, such as economics, demographics, public opinion, government policies, availability of natural resources and competitor technologies, not all of them explicitly considered in the scenarios published by those institutions. If robust technology development strategies are to be chosen, it is essential for a manufacturer, in the first place, to have as clear as possible an understanding not only of the published long-term scenarios, but also of the certainties and uncertainties regarding the driving factors that can significantly affect its future in particular. From this understanding, it should ideally create its own set of scenarios, against which it should test its strategies. In a previous paper the author discussed external factors and aspects of published scenarios, which are relevant for manufacturers within their usual planning time scales. From that discussion, two scenarios were proposed, as alternative ‘futures’ to the scenarios published by the International Energy Agency. The study was restricted to the OECD countries. In this paper, an extension of the previous work is presented, where some non-OECD countries are included and new external factors are considered, relevant in the context of these countries, which are China, Brazil and India.