bluuebunny/crossref_metadata_2025 huggingface dataset:
Validation of a microbial detection system for use with ACD‐A platelets with PAS III platelet additive solution
Authors: Dumont Larry J. , Hay Shauna N. , Herschel Louise , Brantigan Barbara , Houghton Jaime , Elfath M. Dean , Brecher Mark E.
Published: April 2011

BACKGROUND: The BacT/ALERT microbial detection system (BTA) is used for testing leukoreduced apheresis platelets (LR‐AP) in plasma. Platelet additive solutions (PASs) such as InterSol (PAS III) may be used to reduce the amount of plasma transfused in LR‐AP. This study evaluated the performance of the two‐bottle BTA testing scheme in the recovery of seeded microorganisms from LR‐AP in InterSol‐plasma compared to a reference plate culture method.

STUDY DESIGN AND METHODS: Hyperconcentrated, double LR‐AP were collected from healthy donors; InterSol was added (65% Intersol:35% plasma), equally divided into two containers, and then inoculated with an isolate of 1 of 10 clinically relevant index organisms at two levels. Aerobic (BPA) and anaerobic (BPN) BTA bottles were inoculated with 4 mL each of the inoculated LR‐AP, and blood agar plates (BAPs) for aerobic and anaerobic culture (0.5 mL each).

RESULTS: Zero false‐positives from 103 bottle pairs were observed. All 400 two‐bottle BTA tests were positive within 24 hours, except for Propionibacterium acnes (maximum time‐to‐detection of 86.4 hr) and 13 of 20 pairs of Streptococcus viridans (maximum time‐to‐detection of 31.7 hr). Thirteen of 400 BAP two‐plate tests were negative for starting bacterial concentrations of 10 colony‐forming units (CFUs)/mL or less. At 40 CFUs/mL or less, BTA was 100% positive while BAP was 94% positive.

CONCLUSION: Seeded organism recovery was superior in the two‐bottle BTA test system compared to the two‐plate BAP system using InterSol platelets (PLTs). This performance is comparable to previously published results for PLTs in plasma. The use of InterSol does not appear to have a detrimental effect on the performance of the two‐bottle BTA system.
On the use of antiangiogenetic medications for retinopathy of prematurity
Authors: Hård Anna‐Lena , Hellström Ann
Published: April 2011

In contrast to the adult, the third‐trimester foetus experiences one of the most intense periods of growth and maturation of its lifetime. Early development is characterized by the existence of critical periods when environmental factors effectively produce long‐lasting changes.

Proliferative retinopathy of prematurity (ROP) is a potentially blinding disease characterized by uncontrolled retinal angiogenesis. This pathologic angiogenesis is the target for two new treatment modalities for ROP, i.e. intravitreal anti‐VEGF (bevacizumab) and systemic propranolol, which are being evaluated in ongoing or planned studies. VEGF is essential for normal angiogenesis in a growing infant, and the adrenergic system is important for many organ systems and, in addition, for plasticity of the visual and olfactory systems.

Conclusion:  This viewpoint raises concerns regarding the currently studied antiangiogenetic treatments for ROP and their possible general effects on the developing preterm infant.
Pneumococcal vaccination in children at risk of developing recurrent acute otitis media – a randomized study
Authors: Gisselsson‐Solén Marie , Melhus Åsa , Hermansson Ann
Published: April 2011

Aim:  Acute otitis media (AOM) is a common childhood disease, which often becomes recurrent (rAOM). A small reduction in AOM episodes has been noted in unselected child cohorts after vaccination with heptavalent conjugate pneumococcal vaccine (PCV7). The purpose of this study was to investigate how vaccination affects young children at risk of developing rAOM.

Methods:  Ninety‐six children with an AOM onset before 6 months of age, implying a high risk for rAOM, were closely monitored until the age of 2 years. Forty‐six were vaccinated with PCV7 and 50 were not. All episodes of AOM, emergency visits and ventilation tube insertions were registered.

Results:  A total of 363 AOM episodes were diagnosed. The incidence was reduced by 26% (p = 0.03), the number of emergency visits because of suspected AOM by 36% (p = 0.01) and the proportion of children who received ventilation tubes was halved in the vaccine group (p = 0.02).

Conclusions:  During the first 2 years of life, PCV7 significantly reduced AOM episodes, emergency visits and ventilation tube insertions in children with rAOM. Pneumococcal vaccine may be a future route to reduce antibiotic use and health care consumption in otitis‐prone children.
Spontaneous closure of muscular trabecular ventricular septal defect: comparison of defect positions
Authors: Miyake Toshiharu , Shinohara Tohru , Inoue Tomohiro , Marutani Satoshi , Takemura Tsukasa
Published: April 2011

Aim:  To evaluate the timing and frequency of spontaneous closure of the muscular trabecular ventricular septal defect (VSD).

Methods:  We performed a historical cohort study for which 150 patients <3 months of age (median age, 9 days) diagnosed as having a muscular trabecular VSD were selected. Median age at latest follow‐up was 2.8 years. Another 32 patients diagnosed after 3 months of age were also reviewed. Using colour Doppler, defects were classified into three groups: anterior, apical and midventricular.

Results:  Spontaneous closure occurred in 126 patients (84%): anterior, 36 of 47 (83%); apical, 26 of 31 (84%); and midventricular, 64 of 72 (89%). Multivariate analyses showed a lower frequency of spontaneous closure for patients of age of ≥20 days at initial echocardiography [hazard ratio 0.60, 95% confidence interval (CI) 0.39–0.89] and for anterior and apical muscular trabecular VSD (hazard ratio 0.66, 95% CI 0.47–0.95). The prevalence of the midventricular muscular trabecular VSD was significantly lower in patients ≥3 months of age at initial echocardiography than in those <3 months (p = 0.010).

Conclusion:  We infer that midventricular muscular trabecular VSD tends to close spontaneously earlier and more frequently than either anterior or apical muscular trabecular VSD.
Metabolism of N‐methyl‐amide by cytochrome P450s
Authors: Perrin Lionel , Loiseau Nicolas , André François , Delaforge Marcel
Published: April 2011

We report unambiguous proof of the stability of a carbinol intermediate in the case of P450 metabolism of an N‐methylated natural cyclo‐peptide, namely tentoxin. Under mild acidic or neutral conditions, the lifetime of carbinol‐amide is long enough to be fully characterized. This metabolite has been characterized using specifically labeled 14C‐methyl tentoxin isotopomers, HPLC, HPLC‐MS, MS‐MS and NMR. Under stronger acidic conditions, the stability of this metabolite vanishes through deformylation. A theoretical mechanistic investigation reveals that the stability is governed by the accessibility of the nitrogen lone pair and its protonation state. For carbinol‐amines, even in neutral conditions, the energy barrier for deformylation is low enough to allow rapid deformylation. Carbinol‐amide behaves differently. Under neutral conditions, delocalization of the nitrogen lone pair increases the energy barrier of deformylation that is a slow process under such conditions. After protonation, we were able to optimize a deformylation transition that is lower in energy and thus accounts for the lower stability of carbinol‐amides observed experimentally in acidic conditions. Finally, by considering the protocol usually used for extraction and analysis of this type of metabolite, carbinol‐amide may thus be frequently ignored in drug metabolism pathways.
Effects of ageing and endurance exercise training on alpha‐actinin isoforms in rat plantaris muscle
Authors: Ogura Y. , Naito H. , Kakigi R. , Ichinoseki‐Sekine N. , Kurosaka M. , Yoshihara T. , Akema T.
Published: April 2011

Aim:  We recently reported that α‐actinin adaptation occurs at the isoform level. This study was undertaken to clarify the effects of: (1) ageing‐induced shift of myosin heavy chain (MyHC) composition and (2) endurance exercise training on α‐actinin isoforms in rat plantaris muscle.

Methods:  Adult (18 mo) and old (28 mo) male Fischer 344 rats were assigned to either sedentary control or endurance exercise training groups. Animals in the training groups ran on a treadmill for 8 week with training intensity adjusted to be equal for adult and old groups. After the training was completed, the plantaris muscles were taken for analyses of α‐actinin‐2, α‐actinin‐3, and MyHC composition and metabolic enzyme activities.

Results:  The proportion of type IIb MyHC was lower, and that of type I MyHC was higher in old animals than in adult animals. α‐actinin‐3 was significantly lower in old animals than in adult animals. No significant difference was found in α‐actinin‐2 and citrate synthase (CS) activity between adult and old animals. Citrate synthase activity was higher in trained animals than in sedentary animals. Endurance training produced a fast‐to‐slow shift within type II MyHC isoforms in both adult and old animals. α‐actinin‐2 was significantly higher in trained animals than in sedentary animals. No significant difference was found in α‐actinin‐3 between trained and sedentary animals.

Conclusion:  These results support the α‐actinin adaptation at the isoform level and show that the α‐actinin‐3 expression depends on the amount of type II MyHC, whereas α‐actinin‐2 expression is associated with improvement of muscular aerobic capacity.
Investigation of the Photodynamic Effects of Curcumin Against Candida albicans
Authors: Dovigo Lívia N. , Pavarina Ana Cláudia , Ribeiro Ana Paula D. , Brunetti Iguatemy L. , Costa Carlos Alberto de S. , Jacomassi Denis P. , Bagnato Vanderlei S. , Kurachi Cristina
Published: April 2011

This study describes the association of curcumin with light emitting diode (LED) for the inactivation of Candida albicans. Suspensions of Candida were treated with nine curcumin concentrations and exposed to LED at different fluences. The protocol that showed the best outcomes for Candida inactivation was selected to evaluate the effect of the preirradiation time (PIT) on photodynamic therapy (PDT) effectiveness, the uptake of curcumin by C. albicans cells and the possible involvement of singlet oxygen in the photodynamic action. Curcumin‐mediated PDT was also assessed against biofilms. In addition to the microbiological experiments, similar protocols were tested on a macrophage cell line and the effect was evaluated by Methyltetrazolium assay (MTT) and SEM analysis. The optical properties of curcumin were investigated as a function of illumination fluence. When compared with the control group, a statistically significant reduction in C. albicans viability was observed after PDT (P < 0.05), for both planktonic and biofilm cultures. Photodynamic effect was greatly increased with the presence of curcumin in the surrounding media and the PIT of 20 min improved PDT effectiveness against biofilms. Although PDT was phototoxic to macrophages, the therapy was more effective in inactivating the yeast cell than the defense cell. The spectral changes showed a high photobleaching rate of curcumin.
Telmisartan and Amlodipine Single‐Pill Combinations vs Amlodipine Monotherapy for Superior Blood Pressure Lowering and Improved Tolerability in Patients With Uncontrolled Hypertension: Results of the TEAMSTA‐5 Study
Authors: Neldam Steen , Lang Margreet , Jones Russell ,   On behalf of the TEAMSTA‐5 Investigators
Published: April 2011

J Clin Hypertens (Greenwich). 2011;13:459–466.©2011 Wiley Periodicals, Inc.

An 8‐week, randomized, double‐blind, controlled study with single‐pill combinations of telmisartan 40 mg or 80 mg/amlodipine 5 mg (T40/A5 or T80/A5) vs monotherapy with amlodipine 5 mg or 10 mg (A10) in 1097 patients with uncontrolled hypertension (diastolic blood pressure [BP] ≥90 mm Hg). T40/A5 and T80/A5 resulted in significantly greater (P<.0001) reductions in seated trough systolic/diastolic BP vs A5 (−7.4 mm Hg/−3.6 mm Hg; −8.8 mm Hg/−4.9 mm Hg) and a significantly greater (P<.001) proportion of patients achieving systolic/diastolic BP goal rate (60.0%/56.7%; 65.7%/63.8%) vs A5 (39.2%/42.0%). Superior BP reductions were also seen with T40‐T80/A5 vs A10, with BP goal rates at least as high as with A10; however, there was significantly more peripheral edema with A10 (27.2% vs 4.3% for pooled T40‐T80/A5; P<.0001). Switching patients with uncontrolled BP to a single‐pill combination of T40/A5 or T80/A5 is a better treatment option than up‐titration to full‐dose monotherapy with A10.
Assessment of Overlapped Internal and External Volumetric Flaws in p-M Diagram
Authors: Konosu Shinji , Miyata Hikaru
Published: April 2011

Assessment of overlapped internal and external volumetric flaws is one of the most common problems related to pressure vessel and piping components. Under the current fitness for service rules, such as those provided in ASME, BS, and so on, the procedures for the assessment of these flaws have not yet been defined. In this paper, a reference stress, incorporating the decrease in the effective cross section as a function of flaw depth and flaw angle in a cylinder, has been proposed in order to assess the flaws using the simple p-M (pressure-moment) diagram method. Numerous finite element analyses for a cylinder with overlapped internal and external flaws were conducted to verify the proposed procedure. There is good agreement among them.
Influence of Turbocharger Bearing Design on Observed Linear and Nonlinear Vibration
Authors: Kirk R. Gordon , Mondschein Brian , Alsaeed Ali A. , Gallimore Daniel , Frank Andy , Crouch Jakob , Tiller Matt , Vo Tu , Thrush Kyle , Lloyd Robert
Published: April 2011

Automotive turbochargers are known to have operation into the self-excited unstable vibration region. In the past these instabilities have been accepted as unavoidable, but recent developments in analysis and instrumentation may make it possible to reduce or eliminate them. A test stand has been developed at Virginia Tech to measure the vibrations of a 3.9 liter diesel engine stock turbocharger with both stock floating bushing journal bearings and also custom design fixed geometry bearings. Vibration spectrum content clearly identifies the shaft instabilities and provides the basis for additional evaluation of current and future improved bearing design modifications. The current results, for a series of custom fixed geometry journal bearings, show a shift in the frequencies of the two unstable modes for the no load operating condition. These results can be compared to the linear analysis predicted instability frequencies to better understand the actual response of the high speed turbocharger. This paper documents the spectrum content for three different bearing designs and compares the results to a stock floating bush journal bearing result for the same no load operating condition.
A Comparative Study of a Multirecess Hybrid Worn Journal Bearing System Operating in Turbulent Regime Compensated With Different Flow Control Devices
Authors: Sharma Satish C. , Nicodemus E. Rajasekhar
Published: April 2011

The objective of the present work is to study analytically the performance of a four-pocket hybrid worn journal bearing system operating in turbulent regime compensated with different flow control devices i.e. orifice, capillary and constant flow valve (CFV) restrictors. The wear caused on the bearing surface is modeled using Dufrane’s abrasive wear model. The Reynolds equation based on Constantinescu turbulent lubrication theory has been solved using FEM and Newton Raphson method along with the appropriate boundary conditions. The numerically simulated results have been presented for a wide range of restrictor design parameter, non-dimensional external load, wear depth parameter and Reynolds number. The numerically simulated results suggest that when the bearing operates in turbulent regime under unworn condition, the performance of the bearing from the viewpoint of minimum fluid film thickness, fluid film stiffness and damping coefficients and the lubricant flow requirement gets improved vis a vis the bearing operating in laminar regime under unworn condition for all the compensated bearings studied. However, this improvement in bearing performance comes at the cost of higher value of frictional torque. Further, it has been observed that when the bearing operates in turbulent regime, the influence of wear on bearing performance is appreciably less as compared to bearing operating in laminar regime for all the compensated bearings studied. Another notable observation made from the study is that among the various compensated bearings studied in the present work, the constant flow valve compensated bearing appears to be more suitable from the viewpoint of minimum fluid film thickness, fluid film stiffness and damping coefficients and stability threshold speed margin, when the bearing operates in turbulent regime under worn/unworn conditions. The present study suggests that, a proper selection of type of flow control device and the value of its restrictor design parameter is essential in order to obtain an improved performance of a bearing operating in turbulent regime under worn/unworn conditions.
Effects of Angular Motion on Planar Rough Surfaces Contact From Static to Sliding
Authors: Ni Ting , Shi Xi
Published: April 2011

Due to the friction moment, there is an angular displacement when two flat rough surfaces come to sliding contact or quasi sliding contact. A 2-DOF inclined rough surface contact model is presented in this work, and the effects of the angular displacement on the friction coefficient, interfacial forces and moments are investigated. The numerical simulations show that both interfacial forces and moments increase with the increasing inclined angle, while the friction coefficient decreases instead. In addition, for a given sliding mass block system, the effects of the friction coefficient and the base sliding speed on the stability of the sliding contact are also discussed. The simulations indicate that a larger friction coefficient and a higher base sliding speed tend to turn over the mass block during the sliding.
A Numerical Solution for Fretting Contacts
Authors: Wang Zhan-jiang , Hu Yuan-zhong , Wang Wen-zhong , Wang Hui
Published: April 2011

When two surfaces in static contacts are subjected to combined loads applied in the normal and tangential directions, or just a normal load for dissimilar materials, microscopic slip would take place at certain areas of the contact region even though the contacting bodies remain still without macroscopic movement. The micro-slip is considered a major cause of fretting wear for the materials in contacts under alternating dynamic load or vibration, referred as the fretting contacts in this study. The fretting contact problem was solved using a semi-analytical method (SAM), in which analytical relations between a unite stress and corresponding surface displacement were obtained on the basis of Green functions. The contact pressure and shear tractions were then calculated by minimizing the complementary energy, and by a numerical procedure based on Conjugate Gradient Method (CGM) and Fast Fourier Transform (FFT) technique. The algorithm is very effective since the meshes are applied to the positions just in the contact areas of interest, which saves the computing time. The fretting contacts of dissimilar materials were studied and the effects of surface roughness were analyzed. Results show that the coupled effects of shear traction and material dissimilarity make the traction distributions quite different with the solutions from similar materials. The solutions under dynamic load depend on the path or history of the loading process, but the stress distributions and load-displacement curves will quickly converge to a periodic stability after several load cycles.
From 3-D OLROYD-B PTT Models to 2-D Thin Film Non Newtonian Laws
Authors: Bayada G. , Chupin L. , Martin S.
Published: April 2011

The PTT-OLROYD-B model for solute-solvent mixtures introduces visco elastic effects by way of five parameters, namely Deborah number De, a viscosity ratio r, a viscosity, a parameter related to the convected derivation and an elongation parameter κ. Asymptotic expansion is used to gain a description of the flow in the thin film situation. Two cases are considered depending of the relative magnitude of the parameters De and κ with respect to the thickness ratio. In the first situation, the elongation effects disappear at the limits and the constitutive law of the film flow is a double Newtonian Rabinowisch model whose parameters are completely described by those of the original 3-D model. In the second case in which the elongation parameter is of order zero with respect of the film thickness ratio, however small, a perturbation procedure allows to retain this parameter in the asymptotic constitutive law. This law appears to be a small modification of the double Newtonian Rabinowisch law. Last a new numerical procedure is proposed. Numerical examples will be presented for 3-D flows.
Behavior of Advanced Space Lubricant Under Impact Load
Authors: Ohno Nobuyoshi , Mia Sobahan , Nagao Soichiro , Tamura Yoshitaka , Morita Shigeki , Shiomi Hiroshi , Obara Shingo
Published: April 2011

The squeeze film formation ability of advanced space lubricant is studied under impact load by falling bearing steel ball against a flat anvil made of mild steel. Two synthetic base oils (PFPE815Z and MAC2001A) and six greases (600EF, 601EF, 602EF, R2000, ML and MU) are investigated for the EHL dimple film thickness and a breakdown of lubricant film under elastic-plastic impact. The results showed that the viscosity of the base oil 815Z, which contains the acetal group, was decreased by the high shear rate under the EHL squeeze action. To prevention of surface damage under impact load, EHL dimple film thickness is shallow, and becomes as efficient as the grease of which oil film formation is high. From the viewpoint, MU-G and ML-G are good.
Effects of Grease Types on Vibration and Acoustic Emission of Defective Linear-Guideway Type Recirculating Ball Bearings
Authors: Ohta Hiroyuki , Hayashi Shinya , Kato Soichiro , Igarashi Yutaka
Published: April 2011

In this paper, vibrations and acoustic emissions (AEs) of defective linear-guideway type recirculating ball bearings under grease lubrication were measured. The experimental results show that the vibration and AE amplitudes (the pulse amplitudes, the RMS values) of both the normal and defective bearings have a tendency to be reduced when a grease with higher base oil viscosity is used. Under the same type of grease, the RMS values of the vibrations and AE of the defective bearings increase as the defect angle increases. However, the increases of the RMS values due to increased defect angle are reduced when a grease with higher base oil viscosity is used.
Water: An Extraordinary, Ordinary Lubrication Liquid. Influence of Water Salinity, Pressure and Temperature on Water Lubricated Bearings Properties
Authors: Litwin Wojciech
Published: April 2011

Lubrication liquid characteristic has significant influence on bearing properties and working conditions. In calculations of oil lubricated bearings oil viscosity changes resulting from increasing temperature are usually taken into consideration. In water lubricated bearings the isothermal model is usually applied. In most cases, it is a correct method because of negligible viscosity changes resulting from increasing pressure and temperature in the lubrication film. In reality, water has surprisingly unique properties. One of them is strong influence of pressure and temperature on viscosity. In addition, salinity of sea water influences viscosity, as well. Since typical ships can freely sail on all oceans, the sea-water temperature could change more than twenty degrees. This wide range of temperature change has influence on properties of water lubricated bearings.
Multi-Impact Simulation: Effect of the Covering Rate on the Mean Plastic Strain Profiles
Authors: Chaise T. , Ne´lias D.
Published: April 2011

Multi-impact modeling is a challenge in the simulation of processes such as shot peening, with its variants laser peening and ultrasonic peening, or cold spray. Shot peening is commonly used to induce compressive stresses in machine elements subject to fatigue. The large number of impacts involved in the process implies consequent computation time to obtain representative results. In this paper, we present a new approach to model shot peening by using a semi-analytical method that accounts for plasticity. The numerical efficiency of the code along with the use of a small representative area allows reduction in the computation time. It is also possible to observe, with a small number of impacts, the effect of several coverage rates. Thus the improving efficiency of the process with increasing covering rate can be observed as well as potential saturation effect when the covering rate is too high.
Numerical Method of Analyzing Contact Mechanics Between a Sphere and a Flat Considering Lennard-Jones Surface Forces of Contacting Asperities and Mean Height Surfaces
Authors: Ono Kyosuke
Published: April 2011

A numerical analysis method for elastic contact mechanics between a sphere and a flat with a sub-nanometer roughness is presented by taking account of Lennard-Jones (LJ) surface forces. In contrast to conventional theories, the elastic deformations and LJ surface forces of both mean surfaces and contacting asperities are taken into account. Convergent solutions obtained by a simple under-relaxation iteration method are discussed for 2-mm radius glass slider and 20-mm radius head slider contacting with a magnetic disk. It is found that the increase in adhesion force with a decrease in surface roughness can be suppressed by deceasing asperity radius and increasing asperity density.
Multiple Normal Loading-Unloading Cycles of a Spherical Contact Under Stick Contact Condition
Authors: Zait Y. , Zolotarevsky V. , Kligerman Y. , Etsion I.
Published: April 2011

The multiple normal loading-unloading process of an elastic-plastic sphere by a rigid flat is analyzed for stick contact condition and both kinematic and isotropic hardening models. The behavior of the global contact parameters as well as the stress field within the sphere tip is presented for several loading cycles. It was found that under stick contact condition secondary plastification occurs even after the second loading cycle and that the hardening model used has little effect on the loading-unloading process. The cyclic loading process gradually converges into elastic shakedown.
Optimum Design of Fluid Film Bearing for HDD Spindle Considering the Tolerances
Authors: Sunami Yuta , Ochiai Masayuki , Hashimoto Hiromu
Published: April 2011

Fluid film bearings are widely used for high speed rotating machineries acting as rotating shaft support element. Especially, the bearings are widely applied to the OA equipments and IT devices. Optimization of bearing parameters is effective to improve the performance of the fluid film bearings since low noise and impact-proof characteristics are essential requirements for these equipments. On the other hand, bearings for miniaturized spindles are generally made by mass production process which will eventually requires reduction of production costs. In this paper, therefore small size HDD spindle using fluid film bearings is treated. Sensitivity analysis and optimum design that considered dimensional tolerances using the probabilistic techniques are conducted. As a result, the influence of bearing characteristic values on the occurrence of dimensional tolerances was clarified.
Optimum Design of Small Size Fluid Film Thrust Bearing Considering the Productivity
Authors: Sunami Yuta , Hashimoto Hiromu
Published: April 2011

In the manufacturing process of small size fluid film bearings, the machining errors of groove affect the bearing characteristics. This paper describes the optimum design of small size fluid film thrust bearings to reduce the characteristics variability caused by some productivity. Firstly, from the original result of the modified spiral bearing obtained by the geometrical optimization, critical bearing parameters related to sensitivity of dynamic stiffness was investigated. From the sensitivity analysis, it was clarified that the parameters of groove depth and groove ratio have high sensitivity towards bearing stiffness. In the optimum design with consideration of productivity, errors for groove depth and groove ratio were given using probability theory with restriction towards the dynamic stiffness variability. From the results, the reduction of dynamic stiffness variability was accomplished. Furthermore, even if the manufacturing errors exist, the optimized bearing is operated safely without contact because it is able to stay in the range of the allowable film thickness.
Friction and Wear Behavior of Polyetherimide(PEI) Filled With Polytetrafluoroethylene(PTFE)
Authors: Wang LiQin , Sun JianWei , Gu Le
Published: April 2011

The tribological performance of Polyetherimide (PEI) composites filled with different Polytetrafluoroethylene (PTFE) content was comparatively evaluated on MM-200 test rig in block-on-ring configuration under dry friction condition. The microstructures of worn surfaces, fractured surfaces and wear mechanisms of the PEI composite were examined under scanning electron microscope (SEM). The variations of elastic modulus and surface hardness with variation in composition were also investigated. The results showed that under conditions of dry friction the PTFE can lower the friction coefficient and reduce wear of the PEI composites. When filled with 10 wt. % PTFE, the composite had the lowest wear rate. For PEI filled with 5wt. % PTFE the friction coefficient was about 0.3 and remained comparatively stable with increase of the PTFE content.
Friction of Nanoparticle-Covered Surfaces
Authors: Sharma D. , Yang Y. , Ruths M.
Published: April 2011

We present preliminary results from a study of the friction of surfaces with nanoscopic roughness. Surfaces with asperities of a chosen height and average spacing were formed by self-assembly of nanometer-sized solid particles on a flat substrate. The adsorption density of particles was investigated with Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM), and the suitability of these substrates for friction experiments at different length scales was evaluated. Initial results from friction experiments with a nanoparticle-covered surface in non-adhesive contact with an atomically flat surface in a surface forces apparatus (SFA) are presented.
Cavitation Phenomena in Pure-Sliding Grease EHL Films
Authors: Otsu Takefumi , Nagata Yuichiro , Sugimura Joichi , Glovnea Romeo
Published: April 2011

Grease lubricants are widely used in many machine elements which work in elastohydrodynamic (EHD) lubrication regime. They have advantages over lubricating oils, but are prone to starvation, especially when operating at large speeds. At the same time the complex nature of lubricating grease is little understood and only little knowledge about its chemistry and physics is accessible, which makes the prediction of grease film behavior difficult. In the present paper the relation between lubricating grease composition and operating parameters on one hand and the cavitation length on the other, was evaluated.
Surface Damage Under Extreme Conditions Existed in Aircraft Bearings
Authors: Peng Bo , Wang Liqin , Gu Le , Zheng Dezhi
Published: April 2011

The extreme conditions of aircraft bearing steel M50 have been simulated by a two-disk test rig for investigating the surface damage of the ball/raceway contact surfaces. The slide/roll ratio are 0.12 and 0.15, correspondingly, the rolling speed are 43.2m/s and 49.5m/s. Aircraft engine oil 4050 as the supplied oil has been maintained at approximately 80°C in the tests. The ultimate Hertzian contact stresses of the surface damage obtained from the experiments are 3.8GPa in 0.12 slide/roll ratio and 3.5GPa in 0.15 slide/roll ratio. The damage mode is scuffing in 0.12 slide/roll ratio and it is oxidation, thermal fatigue and scuffing in 0.15 slide/roll ratio. Cracks in the contact areas originate from surface layer in the two slide/roll ratios.
Influence of Ultra-Thin Film Tribology on Hard Disk Areal Storage Capacity
Authors: Chong W. W. F. , Teodorescu M. , Rahnejat H.
Published: April 2011

In most industrial applications, a thin film of lubricant improves the tribological behaviour of the load carrying conjunctions. Modern hard disk drives are no exception, where one of the challenges is the progressive demand for higher data storage capacity, while decreasing the physical size of the device. This paper investigates the load carrying capacity of an ultra thin lubricant film formed between the hard disk drive platter and its flying read-write head slider. Hydrodynamic wedge action is responsible for the entrainment of a film of perfluoropolyether into the conjunction, but does not account for the main share of the load carrying capacity of the very thin discretized film, several molecular diameters of the fluid in thickness. It is shown that the main mechanism of pressure generation is in fact the solvation effect. Additionally, starvation of contact may well occur, further exacerbating the thinness of a lubricant film. There is often a cavitation region at the contact exit, which is followed by film reformation, changing the density distribution of lubricant on the surface and consequently the attainable data storage density. This is caused by the observed clumps of lubricant in the reformation zones (a phenomenon referred to as lubricant mogul) which can also cause transient motions of the read-write head.
A New Solution Method for the Contact Mechanics of Graded Coatings
Authors: Chidlow S. J. , Teodorescu M. , Vaughan N. D.
Published: April 2011

This paper attempts to solve analytically for the stresses present in a graded elastic solid resulting from pressure applied to its surface by computing the Airy stress function. The horizontal dimensions of the solid are assumed finite and hence we form the solution of the stress function as a Fourier series rather than an inverse Fourier transform. Finally, a selection of contour plots is presented to exhibit the behavior of this new model.
Modeling of Carbon/Carbon Composites Under Tribological Solicitations
Authors: Mbodj Coumba , Renouf Mathieu , Baillet Laurent , Berthier Yves
Published: April 2011

The present work proposes a methodology study of Carbon/Carbon composites under dynamical stress and conditions of rubbing contact. It is based on the use of finite elements method (FEM), and homogenization technique is applied an elementary cell of composite under contact condition. The comparison of random equivalent representative volume element underlines the importance to take into account the contact interface in such process.
Oil Film Angular Stiffness Determination in a Hydroelectric Tilting Pad Thrust Bearing
Authors: Srikanth D. V.
Published: April 2011

Tilting pad thrust bearings are designed to transfer high axial loads from rotating shafts to the static support structure. In the present paper, formulation of Reynolds’ equation for the bearing is done in two dimensions (planar). A finite difference method is used to convert the terms of the Reynolds’ equation in to a set of simultaneous linear algebraic equations. A solution procedure for finding value of the pressure in the oil film is described. Numerical integration of the pressure values gives the load distribution. Subsequently, the study of angular stiffness of the film is done by varying the value of the oil film thickness and calculating torques at three different film shapes 1, 2 & 3 of the pad. The angular stiffness, differential displacement and load pertaining to the 3-2 pair are calculated for 0.5%–20% variation of ho. The results obtained show that the values of Kt* and K* converge asymptotically.
A Dynamic Analysis of a Dual Clearance Squeeze Film Damper
Authors: Moraru L. , Keith T. G. , Dimofte F. , Cioc S. , Ene N. , Fleming D. P.
Published: April 2011

Squeeze film dampers (SFD) are devices utilized to control the shafts of high-speed rotating machinery. A dual squeeze film damper (DSFD) consists of two squeeze film bearings that are separated by a sleeve, which is released when the rotor experiences abnormal operating conditions. In this part of our study of DSFD we analyze the case when both the inner and the outer oil films are active. We present computed and measured unbalance responses of a shaft supported in DSFD. The oil forces which are utilized in the calculation of the unbalance response are obtained from numerical solutions of the Reynolds equation. A finite-difference algorithm is utilized for solving the pressure equation within the calculation of the dynamic response of the shaft.
Experimental Investigation of the Development of Cavitation in a Squeeze Film Damper
Authors: Xing Changhu , Horvat Frank , Moldovan Stefan , Braun Minel J.
Published: April 2011

When cavitation takes place in the squeeze film damper (SFD), its types and extent affect the performance of the SFD significantly. Thus, a fundamental understanding of the incipience, formation and evolution of this phenomenon becomes important both for predicting the dynamic properties of the damper and for the practitioner designers. A test rig was set up to investigate the formation of the cavitation bubbles during the process of a steady-state operation. By adopting a crankshaft configuration, the SFD journal orbit can be fixed at a specified eccentricity. The journal position and its eccentricity are tracked by means of Bently proximity sensors. When cavitation takes place, its shape and evolution are recorded by a Photron APX-RS high speed camera. With the Dow Corning 200 lubricant, the gaseous bubbles form in a fern-leaf shape even at low whirling speed. The bubbles evolve to a miniature flattened shape and as the angular speed increases, the gaseous cavitation gives way or is joined by vaporous cavitation. With a further increase of whirling speed, the vaporous bubbles can be clearly seen to occupy a large area. The evolution of the cavitation can be explained by the Sommerfeld pressure curve as it relates to the gaseous and vaporous saturation pressure. The experimental results confirm the assumption made by these authors in the previous numerical simulations for the homogeneous cavitation models.
A Continuum Mechanics Model of Adhesive Contact Based on the Lennard-Jones Potential
Authors: Song Z. , Komvopoulos K.
Published: April 2011

A continuum model of adhesive interaction between elastic surfaces is presented. Surface interaction between two elastic spheres is modeled by the Lennard-Jones (L-J) potential. The analysis is based on the equivalent system of a rigid sphere of reduced radius in close proximity with an elastic half-space of effective elastic modulus. The critical gap at the instant of the “jump-in” and “jump-out” contact instabilities is determined by an elastic solution of the half-space surface displacement. A finite element model, in which surface interaction is modeled by nonlinear springs of a prescribed force-displacement governed by the L-J potential, is also used to analyze adhesive surface interaction. The analytical model is validated by finite element results of the critical central gap at the instant of jumpin and jump-out instabilities for different values of the Tabor parameter.
A Discrete Dislocation Plasticity Analysis of Plane-Strain Indentation of a Single-Crystal Half-Space by a Smooth and a Rough Rigid Asperity
Authors: Yin X. , Komvopoulos K.
Published: April 2011

A discrete dislocation plasticity analysis of plane-strain indentation of a single-crystal half-space by a smooth or rough (fractal) rigid asperity is presented. The emission, movement, and annihilation of edge dislocations are incorporated in the analysis through a set of constitutive rules [1,2]. It is shown that the initiation of the first dislocation is controlled by the subsurface Hertzian stress field and occurs in the ±45° direction with respect to the normal of the crystal surface, in agreement with the macroscopic yielding behavior of the indented halfspace. For fixed slip-plane direction, the dislocation density increases with the applied normal load and dislocation source density. The dislocation multiplication behavior at a given load is compared with that generated by a rough indenter with a fractal surface profile. The results of the analysis provide insight into yielding and plastic deformation phenomena in indented single-crystal materials.
Towards the “Green Tribology”: Biomimetic Surfaces, Biodegradable Lubrication, and Renewable Energy
Authors: Nosonovsky Michael , Bhushan Bharat
Published: April 2011

The Green Tribology is a new concept that was suggested in 2009. We discuss the scope of the new discipline and the publications on Green Tribology which are to appear in 2010 and 2011. The three areas relevant to Green Tribology are: (i) biomimetic and self-lubricating materials / surfaces (ii) biodegradable and environment-friendly lubricants (iii) tribology of renewable and/or sustainable sources of energy. The hypothesis is that these three areas can benefit from each other and, therefore, it is justified to combine these three areas into the novel field of Green Tribology. We discuss recent theoretical, modeling, and experimental research in these areas of interest and present theoretical, modeling, and experimental results in the area of environment-friendly tribology.
Friction-Induced Vibrations: From Linear Stability Criteria to Non-Linear Analysis of Limiting Cycles
Authors: Nosonovsky Michael
Published: April 2011

The contact of two elastic bodies with a frictional interface can lead to friction-induced instabilities. The instabilities are either due to the velocity-dependence of friction, or due to the coupling of friction with the thermal expansion or wear, or due to the destabilization of the interface elastic waves. The instabilities lead to friction-induced vibrations. The linear elasticity usually provides a criterion for the onset of the instability and predicts that the amplitude of the unstable vibration grows exponentially with time. However, it does not provide any information about the amplitudes of vibrations. It is expected that the amplitudes of vibrations grow exponentially until they leave the range of applicability of the linear theory and reach a certain limiting cycle. We discuss how various non-linear methods of pattern-formation analysis can be applied to this problem, including the Turing systems, self-organized criticality, etc.
Self-Lubricated Modification for Silicon Nitride Ceramic Ball Surface
Authors: Gu Le , Tang Guangze , Zhang Chuanwei , Jing Cuini , Wang Liqin
Published: April 2011

Some thin films were prepared as solid lubricants on the surfaces of silicon nitride ceramic disk and ball. DLC film about 500–800 nm thickness was deposited on the ceramic surfaces using ion implantation and deposition technology. The surface roundness measure results, as well as 80 to 90 nm, showed that DLC film was shaped uniformly on the ceramic ball surfaces. The ball-on-disk tests showed DLC coating on silicon nitride surfaces could lead the friction coefficient to about 0.1 and endure about 7h at 1.5GPa and 30 mm/s. Ball milling technology was employed to prepare MoS2 film on the ceramic ball surfaces. The film thickness and tribological test results showed that the thin MoS2 film on the ball surfaces, which hardly changed the surface roughness, also improved their wear behaviors.
Fracture Mechanics Analysis of Asperity Cracking Due to Repetitive Sliding Contact
Authors: Xu H. , Komvopoulos K.
Published: April 2011

Asperity failure due to repetitive sliding is a common process of wear particle formation. Linear elastic fracture mechanics and the finite element method (FEM) were used to analyze asperity cracking due to sliding against another rigid asperity. The maximum ranges of the tensile and shear stress intensity factors (SIFs) were used to determine the crack growth direction and the dominant mode of fracture. Simulations of repetitive sliding showed a strong dependence of the wear particle size and wear rate on the direction and rate of crack growth. The maximum ranges of tensile and shear SIFs were used to determine the dominant mode of crack growth. The effects of asperity interaction depth, sliding friction, initial crack position, crack-face friction, and material properties on crack growth direction, dominant fracture mode, and crack growth rate are discussed in the context of FEM results. It is shown that the asperity interaction depth and sliding friction exhibit the most pronounced effects on the crack growth direction and growth rate. A transition from shear- to tensile-dominant mode of crack growth was observed with the increase of the asperity interaction depth and/or sliding friction coefficient. Crack-face opening, slip, and stick mechanisms are discussed in the light of crack mechanism maps constructed for different asperity interaction depths and sliding friction coefficients.
Wear Prediction in Connecting Rod Bearings During Running-In and Transient Speed Conditions
Authors: Fatu Aurelian , Bonneau Dominique
Published: April 2011

During running-in conditions, contact occurs between surface asperities, which induce wear and bearing shell profile adaptation. Firstly, the bearing wear evolution is investigated for different but constant engine rotational speeds. Secondly, the wear is investigated for transient speed conditions. By comparison with a realistic wear coefficient, the real engine time required to reach a steady-state wear condition is predicted.
Study on the Oxidation Process of Mineral Gear and PFPE Oil During Durability Tests of Porous Sliding Bearings
Authors: Kro´l Artur , Giemza Bolesław , Kałdon´ski Tadeusz
Published: April 2011

In the article, the investigative results of the porous bearings and oil samples, after durability tests, are described. The analysis of the results showed that excellent synthetic PFPE oil constituted worse characteristics than mineral gear oil. The observed process of oil ageing was much deeper for synthetic oil than for mineral oil and it was mainly connected to the working temperature of the bearing during real tests.
CFD Study of Grinding Fluid Flow and Heat Transfer in the Abrasive Contact Region
Authors: Mihic Stefan , Cioc Sorin , Marinescu Ioan , Weismiller Michael
Published: April 2011

This paper introduces a research oriented numerical model used to simulate the fluid flow in a grinding process. Some of the most important features of the model are described, along with some results obtained. Distributions of temperatures, pressures and flow rates in and around grinding region are obtained in great detail. These results are essential in studying the influence of the fluid on the grinding process, as well as in determining the best fluid composition and supply parameters for a given application. The results agree well with global flow rates and temperature values found in literature and show the feasibility of 3-D simulations in grinding applications.
Study of the Influence of Input Parameters on the Connecting Rod Big End Bearing Behavior
Authors: Lavie T. , Francisco A. , Fatu A. , Villechaise B.
Published: April 2011

The present paper deals with the influence of functioning parameters on the connecting rod big end bearing behavior. The Design of Experiment (DOE) method is used to get the most of information from a given number of computations.