bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Underwater Shock Wave on Endothelial Cells in Vitro Using Shock Tube
Authors: Tamagawa Masaaki , Ishimatsu Norikazu
Published: March 2009

This paper describes effects of shock waves on cells to certificate the angiogenesis by shock wave (pressure wave) in the clinical application such as ESW (Extracorporeal Shock Wave). Especially, to investigate the effects of shock waves on the endothelial cells in vitro, the cells worked by plane shock waves using shock tube apparatus are observed by microscope. The peak pressure working on the endothelial cells at the test case is 0.4 MPa. After working shock waves on suspended cells, the disintegration, shape and growth rate (area per one cell and population of cells) are measured by image processing. It is found that the younger generation cells have small differences of shape index, and the growth rate of the shock-worked cells from 0 to 4h are clearly high compared with control ones. It is concluded that once shock waves worked, some of them are disintegrated, but the other has capacity to increase growth rate of cell culture in vitro. This preliminary result will be applied to fundamental investigations about shock wave stimulus on several kinds of cells in future.
Effect of Inlet Diameter on the Discharge Coefficients of Toroidal-Throat Critical-Flow Venturi Nozzles
Authors: Ishibashi Masahiro , Morioka Toshihiro
Published: March 2009

The effect of the inlet diameter Din on the discharge coefficient Cd of critical-flow Venturi nozzle with a toroidal throat is investigated in the laminar boundary layer region. Din ranged from 5.00D to 1.73D, which were obtained by shaving the inlet of a high-precision nozzle that was originally complying with ISO 9300. Flat, freestanding lip, and frustum inlets were investigated.
Distributed Processing of High-Speed Stereo Particle Image Velocimetry Data With a Low Power Beowulf Cluster
Authors: Hauser Thomas , Perl Mark A. , Smith Barton L.
Published: March 2009

In this paper, we present our design of a portable cluster supercomputer created specifically for processing PIV image data. To make the system portable for a laboratory environment, the cluster computer is required to run on minimal power and be light weight. The final cluster design was based on the Intel® Quad-Core Xeon®X3210 low-power processors. This hardware setup allows for a total system consisting of twelve processing nodes with a total of 48 CPU cores, one master node with 5 TB of storage, and a Gigabit Ethernet connection. The total configuration along with the case has an approximate gross weight of 390 lbs and works well on one standard 120-V, 20-Amp electric circuit. With this cluster computer, a speedup of about 28 relative to standard serial processing of a PIV data set could be achieved.
Prediction of Asymmetric Tip Clearance Effect on Flow Redistributions in an Axial Compressor
Authors: Kang Young-Seok , Kang Shih-Hyoung
Published: March 2009

Asymmetric tip clearance in an axial compressor induces pressure and velocity redistributions along the circumferential direction in an axial compressor. This paper presents the mechanism of the flow redistribution due to the asymmetric tip clearance with a simple numerical modeling. The flow field of a rotor of an axial compressor is predicted when an asymmetric tip clearance occurs along the circumferential direction. The modeling results are supported by CFD results not only to validate the present modeling but also to investigate more detailed flow fields. Asymmetric tip clearance makes local flow area and resultant axial velocity vary along the circumferential direction. This flow redistribution ‘seed’ results in a different flow patterns according to the flow coefficient. Flow field redistribution patterns are largely dependent on the local tip clearance performance at low flow coefficients. However, the contribution of the main flow region becomes dominant while the tip clearance effect becomes weak as the flow coefficient increases. The flow field redistribution pattern becomes noticeably strong if a blockage effect is considered when the flow coefficient increases. The relative flow angle at the small clearance region decreases which result in a negative incidence angle at the high flow coefficient. It causes a recirculation region at the blade pressure surface which results in the flow blockage. It promotes the strength of the flow field redistribution at the rotor outlet. These flow pattern changes take an effect on the blade loading perturbations. The integration of blade loading perturbation from control volume of the circumferential momentum analysis leads to well-known Alford’s force. Alford’s force is always negative when the flow blockage effects are excluded. However when the flow blockage effect is incorporated into the modeling, main flow effects on the flow redistribution is also reflected on the Alford’s force at the high flow coefficient. Alford’s force steeply increases as the flow coefficient increases, because of the tip leakage suppression and strong flow redistribution. The predicted results are well agreed to CFD results by Kang and Kang (2006).
Wet Gas Performance of Differential Pressure Flowmeters
Authors: Evans Russell , Ifft Stephen A.
Published: March 2009

Wet gas flow measurement is becoming vital to the natural gas production industry. New wells with marginal outputs cannot justify gas-liquid separation equipment and must transfer gas which contains some liquid volume. The flow measurement device on each well dictates the allocation earnings and must therefore provide gas flow measurement as accurately as possible. Several types of differential pressure based flowmeters are currently being used in wet gas flow measurement. DP based flowmeters share many performance characteristics in wet gas applications. However, studies have also found that there can be significant differences in the correlations between meter over reading and liquid content depending of the type of DP meter being tested. Emerson Process Management conducted a series of wet gas tests on a standard orifice plate, a V-Cone, a Venturi and two Rosemount conditioning orifice plates at the National Engineering Laboratory in Scotland (NEL). Previously, tests of conditioning orifice plates in wet gas were conducted at the Colorado Engineering Experiment Station, Inc. (CEESI). The work described in this paper is aimed at investigating the similarities and differences in the performance of these meter types in wet gas flows. Comparisons of these data to those from previous studies on the meter types tested are presented. Also, as a result of these studies, a general method for correcting the over-reading of DP-based, wet gas flowmeters using process measurements and the flow computing capabilities of modern multivariable DP transmitters was developed and is presented.
Development of Engineering Profession Through Engineering Educational Programs of Kogakuin University Accredited by the JABEE
Authors: Saika T. , Furuya O.
Published: March 2009

The Japan Accreditation Board for Engineering Education (JABEE) established in 1999 is a nongovernmental organization that examines and accredits the college and university programs in engineering education. “The Basic Engineering in Global Environment” of Kogakuin University is an engineering program, leading to bachelor’s degree, accredited in the field of “General Engineering” by JABEE in 2001, one of the first three programs accredited in Japan. Since the accreditation is valid for five years, the program recently went through an examination again by JABEE for another 5 years from 2006. The JABEE criteria as well as the procedures and methods of accreditation and examination were not quite well defined in details for a couple of years after 2001. The authors have investigated whether the accreditation system really could help educational improvements for students, faculties and industries. Most of senior students in Japanese technical colleges have to complete graduation thesis work. They will be trained to be researchers rather than engineers, because those themes with a strong scientific aspect belong to their professors. Unlike the graduation thesis work, in the program of the Basic Engineering in Global Environment accredited by JABEE, are offered the subjects like ethics, engineering design, management skills and communication skills, which are required and essential for the engineer. The students can be trained to become true and useful engineers or embryos demanded by industrial companies through these curricula. Furthermore, the graduates of the accredited engineering programs are exempted from Primary Examination for Professional Engineer, since the fundamental capability as an entry-level engineer is assured by the program itself. Basic specialized knowledge is examined in the Primary Examination for PE. In the Final Examination for PE practical engineering experience and skill are examined. The graduates of the program of Basic Engineering in Global Environment will possibly pass the Final Examination without much difficulty, since they learn the management ability, creativity, communication ability and so on with the industry-university co-operational education in the program.
Analytical Procedure on Fluid Mixing Phenomena in Boiling Water Reactor Core With Advanced Interface Tracking Method
Authors: Yoshida Hiroyuki , Misawa Takeharu , Takase Kazuyuki , Akimoto Hajime
Published: March 2009

Thermal-hydraulic design of a boiling water reactor (BWR) is performed by correlations with empirical results of actual-size tests. Then, when the reactor of a new design is developed, an actual size test that simulates its design is required to confirm or modify the correlations. Development of a method that enables the thermal-hydraulic design of nuclear rectors without these actual size tests is desired, because these tests take a long time and entail great cost. For this reason we developed an advanced thermal-hydraulic design method for BWRs using an innovative two-phase flow simulation technology. For this design method, we are developed an advanced interface tracking method that improves fluid volume conservation, to enable high accuracy prediction of two-phase flow fluid mixing phenomena in the fuel bundles. It was incorporated in the detailed two-phase flow simulation code: TPFIT. And the vectorization and parallelization of TPFIT code was conducted to analyze enormous amounts of data. In this study, to verify the TPFIT code performance, the TPFIT code was applied to the air-water and steam-water bubbly two-phase flow in various flow channels and the numerical results were compared with experimental results. Furthermore, the numerical results applied to the fluid mixing phenomena in boiling water reactor rod bundles are shown, and the existing correlations for the fluid mixing phenomena are evaluated by use of these results.
Enhancement of Mixing in a Micro TAS by Micro-Bubble Emission Boiling
Authors: Kato H. , Kimura T. , Yamazaki K. , Yamaguchi M.
Published: March 2009

The mixing of two fluids is important in enhancing chemical reactions in a micro TAS. Some devices or methods are needed to enhance the mixing, because the Reynolds number is very low, on the order of 1. In the present research, we studied the possibility of using micro-bubble emission boiling. A heater made of a platinum wire of 30 micrometer was installed in a Y-shaped micro-channel whose cross sectional area was 2 mm × 0.5 mm. The heater was directly powered by electric current up to 1.5 A. The maximum heat flux was 7.47 MW/m2, which was well above the burnout heat flux. The subcool was 80 degrees and the velocity of fluid (colored water) was changed from 0.5 to 2.0 mm/s. When micro-bubble emission boiling occurred, the mixing was improved drastically. The mixing efficiency reached above 90% at v = 2.0 mm/s and q = 7.47MW/m2. In contrast, the mixing efficiency was poor in the case of normal nucleate boiling. The effect of the mixing chamber was also examined.
Development of a Wet Wall: An Undergraduate Research Project
Authors: Samuel Matt , Henley Jeremiah , Shakerin Said
Published: March 2009

This paper reports an undergraduate research activity on developing a wet wall, which is among the field of water features with special effects. These fountains blend in elements of engineering and the arts in elegant ways, and as such provide an excellent medium of scholarly activity as well as learning. A team of two students worked for one semester to conduct this research. Variables such as water flow rate, wall surface texture, and method of distribution were thoroughly examined. The final apparatus was a dynamic wet wall with visually attractive features that incorporated a programmable microcontroller. The project is low cost, safe and easy to adapt at other institutions, especially in mechatronics courses. The most valuable learning outcomes for the students (the first two authors) were new knowledge about electronics and improvement in communication skills. They also enjoyed developing a visually pleasing product.
A Simulation Study of the BERL Combustor
Authors: Chen Xuelei , Lorra Michael , Yeates Devin , Jian Christopher
Published: March 2009

A simulation study of the BERL Combustor 1, 2, using Computational Fluid Dynamics (CFD), is presented. This work is part of John Zink Company’s effort to validate the CFD models most frequently used by the Simulation Technology. Solutions group to provide modelling services for its customers and to support internal R&D. The CFD results are carefully compared with the experimental data from the BERL project. The current study focused mainly on combustion models and turbulence models. To simulate combustion processes, the selection of an applicable combustion model is a key decision a CFD engineer has to make. The PDF model, multiple flamelets model, eddy dissipation model, and finite-rate/eddy-dissipation model with two different global rates were tested. Simulation results show that the finite-rate/eddy-dissipation model provided the closest agreement with the BERL data. The standard k-ε, realizable k-ε, RNG k-ε, and Reynolds Stress turbulence models were evaluated as the closures. The simulation study indicates that all the turbulence models yielded good agreement with measurements in the highly reacting zone. However, the accuracy of these models varied in areas away from the reacting zone. In some cases, the discrepancy between the predictions and measurements was as high as 20% at certain locations. Finally, discussions and future work are provided.
Identification of Large Scale Structures in Cavitating Wakes
Authors: Wosnik Martin , Arndt Roger E. A.
Published: March 2009

Large-scale three-dimensional cavitating structures can be found in the wake of two-dimensional hydrofoils, as a result of sheet/cloud cavitation on the suction side. This type of cavitation produces unsteady lift on most hydrofoils, including the NACA 0015 hydrofoil studied here, but is periodic and therefore offers the potential for control. In addition to hydrofoils on marine vehicles complex cavitation characteristics are observed in many types of fluid machinery. Examples range from the high-pressure fuel pumps in the Space Shuttle Main Engine to a variety of hydroturbines. Associated with the deleterious effects of performance breakdown, noise, and vibration, there is a possibility of erosion. The purpose of this research is to investigate the twophase flow structure in the wake of a hydrofoil undergoing unsteady partial cavitation using an integrated experimental/numerical approach. This topic provides both numerical and experimental challenges. A two-dimensional NACA 0015 hydrofoil was selected for study, because of its previous use by several investigators around the world. The simulation methodology is based on a Large Eddy Simulation (LES), using a barotropic phase model to couple the continuity and momentum equations. The complementary experiments were carried out at two different scales in two different water tunnels. Tests at the St. Anthony Falls Laboratory (SAFL) were carried out in a 0.19×0.19m2 water tunnel and a geometrically scaled up series of tests was carried out in the 0.3×0.3 m2 water tunnel at the Versuchsanstalt fu¨r Wasserbau (VAO) in Obernach, Germany. The tests were designed to complement each other and to capitalize on the special features of each facility. Time-resolved Particle Image Velocimetry (TR-PIV) was used at SAFL to confirm the existence of the large-scale flow structure observed with the LES.
Fluid Kinetic Energy Based Limits in the Design of Control Valves and Valve-Related Systems
Authors: Sherikar Sanjay V. , Nagpal Vinay
Published: March 2009

The term 1/2ρV2 represents kinetic energy per unit volume; it is also known as dynamic pressure, or velocity head, in flowing fluids and has units of pressure. It is one of the primary parameters in many wide-ranging phenomenon of practical interest in control valves and valve-related systems. The phenomena of interest include vibration, noise, solid particle erosion, liquid impingement erosion, cavitation and more. The description of the extent of these phenomena through their physics, as relating to acceptability of the system performance, is closely tied to the magnitude of the kinetic energy of the flowing stream; this permits use of this parameter as a criterion for reliable performance of control valves and valve-related systems. Kinetic energy criterion is a more general approach, when compared to the older engineering practice of specifying velocity limits only, because it takes into account the effect of fluid density which can be different by orders of magnitude depending on the process. The robustness of this criterion is confirmed by the results of its application in solving valve problems. Its main advantages are simplicity while staying close to the phenomena of interest.
Computational and Experimental Characterization of Single Bubble Dynamics in Isothermal Liquid Pools
Authors: Subramani A. , Kasimsetty S. K. , Manglik R. M. , Jog M. A.
Published: March 2009

The process of bubble growth is of great influence on the bubble volume and bubble rise velocity. The overall behavior of bubbles at fluid interfaces depends strongly on bubble growth and the closely linked process of bubble detachment. In the present study, the dynamics of a single gas bubble emanating from an orifice submerged in isothermal liquid pools is investigated computationally and experimentally. The parametric effects of liquid properties, capillary diameters and air flow rates on the bubble shape, equivalent diameter, and growth times on the dynamic behavior (incipience, growth and necking) of air bubbles, in fluids of varying surface tension and viscosity, as it grows from a tip of a sub-millimeter-scale capillary orifice have been studied. Computational solutions have been obtained by solving the complete set of governing equations using Volume of Fluid (VOF) interface tracking method. The CFD model has been verified experimentally using optical high speed micro-scale flow visualization techniques. The results were analyzed in a theoretical stand point considering the various forces acting on the bubble such as forces due to buoyancy, viscosity, surface tension, liquid inertia, and gas momentum transport, and the consequent motion of the gas-liquid interface. The results obtained ascertain the role of liquid-gas interfacial forces as well as the fluid properties on the bubble growth dynamics.
Numerical Simulations of Three-Dimensional Fluid Flow and Coupled Heat Transfer in Bipolar Plates
Authors: Wu Jianfei , Nie Jianhu , Chen Yitung
Published: March 2009

Bipolar plate is one of the key components in PEM electrolysis cell stacks, and it performs a number of essential functions in stack operation, such as reactant supply to the cell active area, current collection, and mechanical support to the MEA. High efficient PEM electrolysis cell stacks will require optimized bipolar plates. Improvements in the design of bipolar plates can help achieve the set goals of cost and performance for the PEM electrolysis cell. In the present work, numerical simulations were performed for three-dimensional fluid flow and coupled heat transfer in bipolar plates. The Reynolds number of inlet flow is varied from 100 to 900 on the anode side while the Reynolds number is maintained as a constant of 100. The solid wall surfaces of the bipolar plates are assumed to be adiabatically insulated, except that the active areas of the channels are supplied with uniform heat flux. Results of velocity and temperature distributions for different Reynolds numbers will be presented and discussed.
Dynamic Indentation Characteristics of Spherical Sliders Colliding With Stationary Magnetic Disks With a Thin Lubricant Layer
Authors: Ono Kyosuke , Nakagawa Kenji
Published: March 2009

We measured the dynamic adhesion force when spherical sliders with a radius of 1 and 2 mm collided with smooth magnetic disks with lubricant layers of zero, 1, 2, and 3 nm thickness to clarify the dynamic interfacial force between a slider and disk in the nanometer region of flying height. From the measured slider velocity, we calculated the relationship between acceleration (acting force) and displacement. We found that a strong adhesion force observed at zero lubricant vanishes when 1-nm thick lubricant with UV is applied. As the mobile lubricant thickness was increased, we observed a clear dynamic adhesion force at the instant of separation. These results indicate that adhesion force is most likely to result from meniscus formation.
An Analysis of Three-Dimensional Elasto-Plastic Sinusoidal Contact
Authors: Krithivasan Vijaykumar , Jackson Robert L.
Published: March 2009

Researchers have developed many models to simulate the elasto-plastic contact of spheres. However, there does not appear to exist a closed-form analytical model for elasto-plastic three-dimensional sinusoidal contact. This work uses a finite element model (FEM) to characterize elasto-plastic sinusoidal contact. Although at initial contact the sphere and sinusoidal case are very similar and can both be described by the classic elastic Hertz contact case, once the contact is pressed past a critical range of deformation the two cases are very different. The model produces equations which can be used to approximately relate the area of contact to the contact pressure for elasto-plastic sinusoidal contact. The equations are fit to the FEM results and existing elastic solutions to sinusoidal contact. An empirical expression for the average pressure which causes complete contact between elasto-plastic sinusoidal contacts is also provided.
Characterisation of the Mechanical Properties of MEMS Devices Using Nanoscale Techniques
Authors: Randall N. X.
Published: March 2009

This presentation will focus on recent developments in the localized characterization of the mechanical properties of Microsystems and MEMS devices and structures. Conventional indentation techniques provide a highly powerful method for measuring the load and depth response of bulk and coated materials, but can also be used to measure the mechanical properties of very small micro-machined silicon structures. Beam structures, such as are used for accelerometers, need to be characterized in terms of the number of cycles to failure, the spring constant or the energy required to bend the beam by a required amount. Such localized testing needs to be adapted to work at various distances from the origin of the beam with a positioning accuracy of less than a micron. Initial studies have proved to be highly repeatable. A variety of examples are presented which cover a range of application areas, including accelerometer beam structures, micro-switches and printer head components. In addition, the localized testing of friction and wear in MEMS devices will be covered with some examples of the technology available and how it may be applied to such small contact areas in an accurate and reproducible way.
Study on Antioxidation Properties of the Complex of Dithiocarbamate With Tolutriazole Antioxidant
Authors: Zhang Yi , Luo Yan , Hu Jian-Qiang , Zhang Tao , Xu Yun-Yun
Published: March 2009

The antioxidation properties of methylene bis(di-n-butyldithiocarbamate) (V 7723) - and tolutriazole derivative (V 887) - containing poly-a-olefin (PAO)-derived lubricants were evaluated by differential scanning calorimetry (DSC) and modified penn state micro-oxidation test (PMOT). DSC test measures incipient oxidation temperature (OT) and oxidation induction time (IT) of the lubricant at high temperatures and the oxidation stability of oil weight loss is measured by PMOT test. DSC test shows that OT and IT of V 7723-containing PAO were improved significantly by V 887 addition. PMOT test indicates that when combining with V 7723 antioxidants, V 887 can also effectively reduce the increase in weight loss of PAO. In addition, FTIR results from PMOT test confirm that addition of V 887 can significantly enhance the oxidation induction time of oils. These results suggest that the V 7723 shows a good oxidative synergism with V 887 antioxidant.
Solid-Liquid Interface Slip as a Rate Process
Authors: Martini A. , Lichter S. , Snurr R. Q. , Wang Q.
Published: March 2009

Thin film lubrication may be significantly affected by slip at the solid-liquid interface. Slip occurs when there is a jump in the mean speed between the walls and the first layer of liquid molecules. Using molecular simulation, we show that the amount of slip is greatly affected by solvation pressure and that this dependence can be accounted for by treating slip as a rate process. This treatment enables formulation of a quantitative relationship between solvation pressure and interface slip.
Fragility and the Dynamic Crossover in Lubricants
Authors: Bair Scott , Roland C. M. , Casalini R.
Published: March 2009

The property of fragility in glass forming liquids is introduced to elastohydrodynamic lubrication (EHL). Using viscosity measurements for two liquids that have been the subject of traction studies, the fragility of liquids is shown to be important to EHL traction and the property that most influences the representative (Eyring) stress. The derivative Stickel analysis is then carried out for lubricants. Using viscosity measurements, the dynamic crossover is detected for the first time in lubricants. The viscosity at the crossover is either constant or varies slowly with temperature and pressure and the crossover pressure varies with temperature in a manner similar to the glass transition pressure. The free volume model fails to predict the occurrence of the dynamic crossover.
Experimental Modelisation of Organosulphurs Tribochemistry by Gas Phase Lubrication
Authors: Tannous J. , De Barros Bouchet M. I. , Le Mogne T. , Martin J. M. , Charles P.
Published: March 2009

Organosulphurs compounds have been used for many years as Extreme Pressure (EP) and Anti Wear (AW) additives in a wide range of metal working applications. These additives act in severe conditions by building up a reaction film (tribofilm) on the metallic surfaces. Several interpretations have been proposed to explain the (EP) and the (AW) properties of these compounds, but the detailed mechanisms and surface reactions products are still largely unknown. To better understand the tribochemistry of these compounds, we developed a new device in our laboratory called “Environmentally Controlled Tribometer”. This apparatus permits to study the interaction of one or several additives on different metallic surfaces using a gas having the same chemical function as the additive. After friction experiments, in-situ surface analyses (XPS and AES) were carried out on the tribofilm, to clearly identify the reactions products in order to understand the tribochemical mechanism. In this paper, we simulate the metal working lubrication of steel by the gas phase lubrication. The results show a clear difference in tribological behaviour and surface products between triboreactivity on nascent and oxidized surfaces. These observations gave us new information to better understand the tribochemical reactions of these additives. The comparison between the liquid phase lubrication and the gas phase lubrication results validates this methodology.
Comprehensive Nano-Mechanical and Tribological Characterization of Hair
Authors: Gitis Norm , Hermann Ilja , Kuiry Suresh , Khosla Vishal
Published: March 2009

This paper presents test procedures and results of tribological and mechanical characterization of hair, treated with various shampoo and conditioners. They allow for a comprehensive functional comparison of hair care products.
Thermal Degradation of Soybean and Sunflower Oils
Authors: Siniawski Matthew , Saniei Nader , Pfaendtner Jim
Published: March 2009

Although the chemical composition of vegetable oils is responsible for their enhanced lubricity at ambient conditions, it is also the main reason for their degradation at elevated temperatures. Therefore, this study focuses on the friction and wear of soybean and sunflower oils at elevated temperatures in comparison to a base mineral oil. It was found that the wear and friction are less severe for the vegetable-based lubricants up to temperatures around 100°C. The observed performance of the vegetable-based lubricants is verified using a kinetic reaction mechanism model of the lubricant degradation.
Study on the Life Distribution and Reliability of Roller Based Linear Bearing
Authors: Shimizu Shigeo , Shimoda Hirokazu , Tosha Katsuji
Published: March 2009

A study on the life distribution and reliability for roller guides with cage is carried out with a total number of 90 test samples in two lots (Ns = 38 and 52), and fatigue life distribution functions, such as two and three parameters Weibull distribution, and log-normal distribution are used for analyzing the test data. The basic dynamic load rating formula standardized by ISO in 2004 is also compared with the life test data in relation to the effect of crowning on both ends of the carriage raceway. Weibull slope, compatibility of distribution functions and λbm factor are also examined.
Evaluation of DLC Coatings for Foil Bearing Applications
Authors: Jahanmir Said , Heshmat Hooshang , Heshmat Crystal , Eryilmaz Osman , Erdemir Ali
Published: March 2009

A critical component in oil-free air foil bearings is the tribological coating system that must be used on the journal/runner and the foil pads to ensure reliable operation during transient periods and start-stop cycles. The purpose of the present investigation was to evaluate the performance characteristics of hydrogenated diamond like carbon coatings (H-DLC) for foil bearing applications. Tribological tests were performed using a single thrust foil bearing in contact with a rotating flat disk at room temperature. While the performance of H-DLC coating on the foils tested against disks coated with MiTi® Korolon™ 900 was acceptable, the reverse coating combination provided an excellent performance. Although the H-DLC film had suffered some wear along narrow scratches, both coatings survived the 500 start/stop cycles. The liftoff speed, which is an important design parameter, was less than 1,000 rpm, much lower than uncoated foil and disk combination. It is, therefore, concluded that the combination of H-DLC foil coating with the Korolon™ 900 coating on the disk will provide excellent performance for foil bearing applications at room temperature.
Shakedown in Frictional Contact Problems
Authors: Barber J. R. , Klarbring A. , Ciavarella M.
Published: March 2009

If a linear elastic system with frictional interfaces is subjected to periodic loading, any slip which occurs generally reduces the tendency to slip during subsequent cycles and in some circumstances the system ‘shakes down’ to a state without slip. It has often been conjectured that a frictional Melan’s theorem should apply to this problem — i.e. that the existence of a state of residual stress sufficient to prevent further slip is a sufficient condition for the system to shake down. Here we discuss recent proofs that this is indeed the case for ‘complete’ contact problems if there is no coupling between relative tangential displacements at the interface and the corresponding normal contact tractions. By contrast, when coupling is present, the theorem applies only for a few special two-dimensional discrete cases. Counter-examples can be generated for all other cases. These results apply both in the discrete and the continuum formulation.
Tribological Testing of Graphite and Boron Nitride Lubricant Formulations for High Temperature Aluminum Sheet Forming Processes
Authors: Hanna M. David , Krajewsk Paul E. , Schroth James G.
Published: March 2009

The tribological behavior of AA5083 aluminum sheet sliding against tool steel impacts the quality of components manufactured with the elevated temperature metal forming processes such as Quick Plastic Forming (QPF), Superplastic Forming (SPF), or warm forming. This study focuses on the tribological performance and evaluation of alternative solid lubricants using a flat-on-flat tribo-tester to simulate sheet forming at high temperature applications. Improved lubricant formulations containing boron nitride with graphite additions were found to enhance lubricity while maintaining good adherence to the surface of the aluminum blank at a temperature of 450°C.
Frictional Characteristics of Mesoporous SiO2 Thin Film Formed by Sol-Gel and Self-Assembly Method
Authors: Shin Yun-Ha , Jeon Hong-Gyu , Son Jeong-Kuk , Kim Ji-Man , Kim Tae-Sung , Lee Young Ze
Published: March 2009

Frictional characteristics of mesoporous SiO2 thin films were evaluated with different pore sizes. The films were manufactured by sol-gel and self-assembly methods to have a porous structure. The pores on the surface may play as the outlet of wear particle and the storage of lubricant so that the surface interactions could be improved. The pores were exposed on the surface by chemical mechanical polishing (CMP) or plasma-etching after forming the porous films. The ball-on-disk tests with mesoporous SiO2 thin films on glass specimen were conducted at sliding speed of 15rpm and a load of 0.26N. The results show considerable dependency of friction on pore size of mesoporous SiO2 thin films. The friction coefficient decreased as increasing the pore size. CMP process was very useful to expose the pores on the surface.
Effect of Side Feed Pressurization on the Dynamic Performance of Gas Foil Bearings
Authors: San Andre´s Luis , Kim Tae Ho
Published: March 2009

Oil-free micro turbomachinery implementing gas foil bearings (GFBs) has improved mechanical efficiency and reliability. Adequate thermal management for operation in high temperature environments is an issue of importance in applications such as in gas turbines and turbochargers. GFBs often need a cooling gas flow, axially fed through one end of the bearing, to transport the heat conducted from a hot turbine, for example. Side gas pressurization, however, has a paramount effect on reducing amplitudes of motion, synchronous and subsynchronous. Presently, shaft motion measurements in a test rotor supported on GFBs show this remarkable effect. A computational gas film model implementing the evolution of gas circumferential flow velocity as a function of the imposed side pressure is advanced. Predicted direct stiffnesses and damping coefficients for the test GFB increase as the magnitude of feed pressure raises, while the difference in cross-coupled stiffnesses, directly related to rotor-bearing system stability, decreases. Predictions of threshold speed of instability and whirl frequency ratio are in close agreement with the measurements.
Wetting and Adhesion Properties of Organic Monolayer Modified Nano-Topography-Engineered Surfaces
Authors: Premachandran Nair R. , Song Y. , Zou M. , Wang Y. A.
Published: March 2009

This paper reports a study of wetting and adhesion properties of nano-topography-engineered surfaces (NTES) modified with Octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM). Samples of various surface topographies were fabricated using aluminum-induced crystallization (AIC) of amorphous silicon (a-Si) technique by changing process parameters. The effects of surface topography on the wetting and adhesion properties were investigated. The results showed that surface wetting and adhesion properties were significantly improved for OTS modified NTES surfaces compared to OTS modified smooth silicon surfaces, and there is a direct correlation between surface morphology, and the wetting and adhesion properties of surfaces. Superhydrophobic surfaces with water contact angle (WCA) of 155° were achieved at optimum surface texture area coverage.
A Continuum Model for Dense Third Body Thin Film Flow: Interactions With Discrete Simulations
Authors: Tichy John , Bertier Yves , Iordanoff Ivan
Published: March 2009

The present paper applies a recent continuum theory due to Aranson and Tsimring [1] for dense granular flows to thin film flows. Such third body granular flow may apply to solid lubrication mechanisms. The continuum theory is unique in that it addresses solid-like behavior and the transition to fully fluidized behavior. The continuum studies are complemented by a discrete particle dynamics model of Iordanoff et al. [2].
Thermal-Elastic-Plastic Contact Analysis for Rough Bodies With a Semi-Analytical Method
Authors: Boucly Vincent , Ne´lias Daniel , Brunet Michel
Published: March 2009

Nowadays, Finite Elements softwares allow the user to model efficiently the contact between two solids. It is though necessary to make numerous assumptions in order to compute a contact in a reasonable time: generally surfaces are smooth and the mesh is too coarse to accurately study transient phenomena. Moreover, friction on the surface is rarely taken into account since models are usually axi-symmetric. This paper presents a semi-analytical formulation that allows computing the contact between two elastic-plastic solids with rough surfaces. The numerical methods used, i.e. the conjugate gradient and the fast Fourier transform allow to refine the mesh drastically. The main advantage of this formulation over Finite Elements method is the much shorter computation times. This model takes into consideration the hardening of material as well as friction and frictional heating at the interface. Loading can be vertical or rolling/sliding. This formulation allows realizing cyclic loadings in order to model numerous engineering problems as running-in, fretting, asperities tugging, as well as electro-mechanical micro-contacts. A comparison is made between the vertical contact (static loading) and the rolling/sliding contact (transient loading) in the case of an adiabatic elastic sphere rotating and pressed against a rough and stationary elastic-plastic surface. The influence of the friction coefficient is underlined.
Performance Analysis of Double-Bumped Air Foil Bearings
Authors: Kim Y. C. , Lee D. H. , Kim K. W.
Published: March 2009

This paper presents a theoretical model for the analysis of double-bumped Air Foil Bearings (AFBs). The stiffness and damping coefficients of the double bump vary depending on the external load and its friction coefficient. The double bump can be either in the single or double active region depending on vertical deflection. The equivalent stiffness and damping coefficients of the bump system are derived from the vertical and horizontal deflection of the bump, including the friction effect. The results of the performance analysis for a double bumped AFB are compared with those obtained for a single bumped AFB. This paper successfully proves that a double bumped AFB has higher load capacity, stiffness, and damping than a single bump AFB in a heavily loaded condition.
Experimental Study of Stabilisation of Small Size Journal Bearing With Oil Supply Groove by Using Starved Lubrication and Bearing Orientation Angle Change
Authors: Ochiai Masayuki , Hashimoto Hiromu
Published: March 2009

Journal bearings are widely used for supporting high speed rotating machinery such as turbine, compressor and HDD spindle etc, because of their high load carrying capacity, stability and durability. Recently, the engineering trend is oriented to higher speed and smaller sizes of rotating machinery, and then it is important to enhance stabilities for the journal bearings. Tilting pad journal bearing is generally used for high-speed rotating machineries because of their advantages of stabilization. However, there are some problems using for compact size rotating machineries for their high manufacturing cost and complicated structure. Therefore, it is necessary to enhance the stability of more simple bearings compared with tilting pad bearing in order to use for small size rotating machinery. This paper describes the stabilization method of journal bearing based on the combination mechanism with starved lubrication and orientation angle change. From the results of stability experimental study of journal bearings, it is clarified that the stabilization of bearings is improved drastically by using above techniques.
Response of Materials During Sliding on Various Surface Textures
Authors: Menezes Pradeep L. , Kishore  , Kailas Satish V.
Published: March 2009

In the present investigation, basic studies were conducted using Inclined pin-on-plate sliding Tester to understand the role of surface texture of hard material against soft materials during sliding. Soft materials such as Al-Mg alloy, pure Al and pure Mg were used as pins and 080 M40 steel was used as plate in the tests. Two surface parameters of steel plates — roughness and texture — were varied in tests. It was observed that the transfer layer formation and the coefficient of friction which has two components, namely adhesion and plowing component, are controlled by the surface texture of harder material. For the case of Al-Mg alloy, stick-slip phenomenon was absent under both dry and lubricated conditions. However, for the case of Al, it was observed only under lubricated conditions while for the case of Mg, it was observed under both dry and lubricated conditions. Further, it was observed that the amplitude of stick-slip motion primarily depends on plowing component of friction. The plowing component of friction was highest for the surface that promotes plane strain conditions near the surface and was lowest for the surface that promotes plane stress conditions near the surface.
Influence of Surface Textures During Metal Forming
Authors: Menezes Pradeep L. , Kishore  , Kailas Satish V.
Published: March 2009

Friction plays an important role in metal forming processes. In the present investigation, various kinds of surface texture with varying roughness were produced on steel plates. Pins made of Al-8Mg alloy were then slid against the prepared steel plates using inclined pin-on-plate sliding tester to understand the role of surface texture of the harder surface and load on coefficient of friction and transfer layer formation under both dry and lubricated conditions. It was observed that both the coefficient of friction and transfer layer formation are highly dependent on the surface texture of harder counterface. Numerical analysis of simulated compression test, assigning different magnitude of coefficient of friction at different regions between the die and work piece, was carried out to understand the effect of friction on deformation and stress distribution. Results of simulation revealed that, owing to the difference in coefficient of friction, there is a difference in metal flow pattern. Both experimental and numerical results confirmed that the surface texture of the die surface and thus coefficient of friction directly affects the strain rate and flow pattern of the work-piece.
Design, Fabrication and Performance of Open Source Generation I and II Compliant Hydrodynamic Gas Foil Bearings
Authors: DellaCorte Christopher , Radil Kevin C. , Bruckner Robert J. , Howard S. Adam
Published: March 2009

Foil gas bearings are self-acting hydrodynamic bearings made from sheet metal foils and are used in selected lightly loaded, highspeed turbo-machines such as compressors and small microturbines. The general lack of familiarity of the foil bearing design and manufacturing process has hindered their widespread dissemination. Using information from publicly available literature, this paper demonstrates design, fabrication and performance testing of first and second generation bump style foil bearings and serves as an effective starting point for new Oil-Free turbomachinery development activities.
Rolling of an Elastic Ellipsoid Upon an Elastic-Plastic Flat
Authors: Ne´lias D. , Antaluca E. , Boucly V.
Published: March 2009

The paper presents a numerical analysis of the rolling contact between an elastic ellipsoid and an elastic-plastic flat. Numerical simulations have been performed with the help of a contact solver called Plast-Kid®, with an algorithm based on an integral formulation or semi-analytical method. The effects of the ellipticity ratio k — ranging from 1 to 16 — and of the normal load — from 4.2 to 8 GPa — are investigated. The reference simulation corresponds to the rolling of a ceramic ball on a steel plate made of AISI 52100 bearing steel under a load of 5.7 GPa. The results which are presented are first the permanent deformation of the surface, and second the contact pressure distribution, the Von Mises stress field, the hydrostatic pressure and the equivalent plastic strain state within the elastic-plastic body. A comparison with an experimental surface deformation profile is also given to validate the theoretical background and the numerical procedure.
Investigation of New Bionic Therapeutic Lubricants
Authors: Zhang Jianhua , Hua Zikai , Su Shihu
Published: March 2009

Based on the bionic artificial joint system, new therapeutic bionic lubricants not only for artificial joints lubrication but also for the treatment of particle-induced osteolysis are developed and investigated. In this study, their tribological characteristics and mechanisms are studied. The tribological experimental results show that the therapeutic lubricants have the best anti-wear performance among the lubricants tested in the experiments, such as hyaluronic acid (HA), bovine serum et al. It is found that there is some membrane self-assembled on the surface of the cup which may give a likely answer to the high lubricating performance of the therapeutic lubricants. The calculated film thickness of therapeutic lubricants is about 0.310 μm. The result indicates it is still in the boundary lubrication state. The preliminary biological experiments show that therapeutic lubricants have good biocompatibility. More tests are needed to clarify the form of the membrane and the medical performance of the therapeutic bionic lubricants towards the undesired reactions induced by the wear debris.