bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of surface roughness features on mixed‐film lubrication
Authors: Choo J. W. , Olver A. V. , Spikes H. A.
Published: July 2006

An optical technique (three‐dimensional spacer layer imaging) has been developed to map accurately lubricant film thickness in thin‐film elastohydrodynamic (EHD) contacts. This experimental technique has been used to study the influence of surface roughness features, asperity height, and slope on EHD film thickness and pressure. Single ridges transverse to the entrainment direction were used to represent asperities. It was found that the ridges with lower slopes generate films of greater minimum thickness. Below a certain entrainment speed, the minimum film thickness declined at a rate dependent on the ridge slope. At low speeds, the ridges with higher slopes entrapped a larger volume of lubricant ahead of the ridge and along the entrainment direction. For all speeds, the highest ridges entrapped the most lubricant. Both ridge slope and ridge height had a negligible effect on mean film thickness in the contact. Asperity pressure increased with higher ridge slope, but was not influenced by entrainment speed. An increase in pressure was found where lubricant is entrapped upstream of a ridge.
Comparison of an optimum‐profile hydrodynamic thrust bearing with a typical tilting‐pad thrust bearing
Authors: Wasilczuk M.
Published: July 2006

The oil gap profile in a hydrodynamic thrust bearing exerts a great influence on the bearing properties, and hence the optimisation of the oil gap profile is one method for improving the bearing properties. In the present work, the properties of two hydrodynamic thrust bearings have been experimentally compared under realistic load/ speed conditions. One was a typical tilting‐pad bearing and the other was an unconventional bearing with an elastic thrust plate. The latter was designed using oil gap profile optimisation and design parameter selection. Owing to the design method used, the oil gap profile was close to optimum for the assumed load/speed conditions. The results show a substantial increase in the minimum oil film thickness and lower temperature in the bearing with the elastic thrust plate. This improvement of properties is thought to be because of the optimised oil gap profile in the bearing.
Copolymeric succinamic acids as antiwear additives: Synergistic and adverse effects
Authors: Mehrotra A. K. , Nandi T. , Agnihotri R. K. , Mathur G. N.
Published: July 2006

Copolymeric succinamic acid (COSMA) additives have been synthesised in the laboratory and evaluated for their antiwear performance, both alone and in combination with zinc dialkyl‐dithiophosphate (ZDDP) in HVI light neutral oil. COSMA additives show antiwear behaviour and, in combination with ZDDP, exhibit a good synergistic effect, reducing the wear‐scar diameter by 60% and increasing the initial seizure load from 50 kg to 85–95 kg.
Tribochemical effect of impurities in zinc dialkyldithiophosphate in engine oil
Authors: Hu Xianguo , Wo Hengzhou , Han Guopei , Lu Yaling
Published: July 2006

This study deals with the effects of alcohols and ketones, two substances usually found in commercial zinc dialkyldithio‐phosphate (ZDDP), on the tribological behaviour of ZDDP. Experimental results show that two alcohol and ketone compounds, namely 2‐ethylhexanol and methyl isopropyl ketone, respectively, have an influence on the lubricity, wear resistance, and friction‐reducing properties of ZDDP. 2‐Ethylhexanol can increase the extreme‐pressure properties of ZDDP (the load‐carrying capacity of a lubricating oil being enhanced from 710 to over 1100 N). At the same time, the alcohol can also improve the wear resistance of ZDDP. However, this alcohol is detrimental to the antifriction properties of ZDDP, the friction coefficient of a lubricating oil being increased from 0. 0919 to 0. 1010. The antioxidative ability of ZDDP is weakened to some extent. The presence of a ketone, with a carbonyl group, greatly decreases the load‐carrying capacity of ZDDP, which goes down from 710 N to 597. 8 N on the addition of 1. 5 wt. % methyl isopropyl ketone to ZDDP. The mechanisms of the influence of the alcohol and ketone on ZDDP are also investigated.
Friction and wear behaviour of Sialon/ (Ca,Mg)‐Sialon with lubrication by coated PbS nanoparticles as oil additives
Authors: Zhang Wenguang , Chen Shuang , Liu Weimin , Yu Laigui
Published: July 2006

The friction and wear behaviour of Sialon/(Ca,Mg)‐Sialon with lubrication by liquid paraffin containing PbS nano‐particles coated with dialkyldithiophosphate or oleic acid as additives was investigated using an SRV ball‐on‐disc test rig. It was found that the addition of such nanoparticles reduced the friction coefficient of the friction couple irrespective of the concentration of the additive and the wear volume of (Ca,Mg)‐Sialon, especially under relatively high loads such as 150 N or more. X‐ray photoelectron spectroscopy and electron probe microanalysis revealed that a tribochemical film composed of PbSO4, PbS2O3, PbSO3, etc., was formed on the worn surface, and contributed to the lubricity of the PbS nanoparticles.
Tribological behaviour of S‐esters and amine salts of the O, O‐polybutoxyglycol diester of dithiophosphoric acid in mineral oil solution
Authors: Mizerski M. , Celichowski G.
Published: July 2006

The tribological properties of derivatives of the polyalkoxyglycol esters of dithiophosphoric acid were tested using four‐ball and ball‐on‐disc machines. Polybutoxyglycol dithiophosphoric acid derivatives were found to be effective load‐carrying additives in mineral base oil. Four‐ball and ball‐on‐disc data of some of these additives showed them to have very good antiwear/extreme‐pressure and antifriction properties. These properties were dependent upon the additive's chemical nature, concentration, sliding speed, and load. The presence of polybutoxy groups decreased the concentration of phosphorus in the additive in comparison to zinc dialkyldithiophosphates.
Improvement of antiseizure, antiwear, and anticorrosion properties of thin nitrided layers by impregnation with oil‐ or solvent‐based formulations
Authors: Iwanow J. , Senatorski J. , Tacikowski J.
Published: July 2006

The results of some corrosion and tribological investigations are presented in this paper. Samples with thin (white layer, WL = 16.5 μm) nitrided layers on 45‐grade steel obtained in a controlled gas nitriding process (at 570°C, 6 h; WL = 16.5 μm; grey porous zone or grey layer, GL = 6.0 μm) and impregnated by multifunctional oil‐based formulations containing BS‐MOD corrosion inhibitor (CI) as well as tribological additives (TAs) were used. The TAs when present alone (without the CI) in oil have no corrosion‐inhibiting features and also do not affect the corrosion resistance of WLs impregnated with formulations containing both the CI and TAs; corrosion resistance is mainly connected with the presence of the CI. Synergistic effects observed between TAs and the CI as well as TA concentration vs. BS‐MOD in multifunctional additives are more apparent in seizure features and wear resistance of impregnated WLs. The influence of the TAs in combination with the CI depends on their type and concentration; it can be positive or negative. Hence, the choice of composition of CI and TA for multifunctional impregnating formulations is determined, above all else, by the relation between the CI and the grade of TA. The anti‐corrosion effect as well as the tribological function is dominated by the CI component (BS‐MOD).
The influence of lubricating oil on the performance of a metal V‐belt‐type continuously variable transmission
Authors: Narita Keiichi , Deshimaru Junichi , Kato Masayuki
Published: July 2006

The influence of lubricating oil on the torque capacity and the efficiency of a continuously variable transmission (CVT) of metal V‐belt type were experimentally investigated using a commercial CVT unit with a belt assembly and pulley. In order to analyse the friction characteristics of each of the contacting parts in the CVT, a block‐on‐disc type friction testing machine was used. The maximum torque capacity between the belt and pulley in the actual CVT correlated with the friction coefficient under high contact pressure (200 MPa) and relatively high sliding velocity (0.1 m/s) on the friction testing machine. The transmission efficiency decreased as the load decreased. The maximum difference in the efficiency between all the commercial automotive transmission and CVT fluids tested reached 6%. It was found that the requirements for the efficiency of transmission at a lower load were in contradiction with the maximum torque capacity.
The temperatures at scuffing and seizure in a four‐ball contact
Authors: Wisniewski M. , Szczerek M. , Tuszynski W.
Published: July 2006

The temperature of surface asperities affects lubricant‐surface tribochemical interactions. It is important to know the nature of this to identify ways of preventing scuffing and seizure under extreme‐pressure (EP) conditions. A new model for the determination of the temperature of contacting asperities is presented in this paper. It assumes the superposition of thermal processes occurring on the macroscale and thermal phenomena in the contact of asperity tips (microscale). Numerical results have been obtained for conditions of four‐ball testing of various lubricating oils — a mineral base oil with and without antiwear and EP additives. To calculate the scuffing and seizure temperatures, knowledge of the mechanical and physical properties of the test ball material (bearing steel) and lubricants, as well as the parameters describing the surface topography of the balls, was necessary. Friction coefficient curves were also needed; they were determined during four‐ball tests with a continuously increasing load. For the base oil with lubricating additives, the temperature of contacting surface asperities at the moment of scuffing initiation was calculated to be about 230°C and increased to over 1000°C at the highest loading of the four‐ball tribosystem. This suggests the possibility of tribochemical reactions of the lubricating additives with the steel surface, and diffusion of some elements, a modified surface layer having good antiseizure properties being produced. Such a layer prevents seizure of the tribosystem. For the base oil without lubricating additives, scuffing initiated at about 150°C and the temperature exceeded 1200°C at seizure. The temperature values obtained agree with results in the literature.
Tribochemistry of aluminium and aluminium alloy systems lubricated with liquids containing alcohol or amine additive types and some other lubricants — a review
Authors: Kajdas C. , Liu W.
Published: July 2006

The ability of a lubricating oil to reduce wear and prevent damage of interacting solids is a crucial factor controlling lubricant formulation. It is well known that friction produces local high temperatures. Many chemical reactions that are initiated by the friction process itself occur at much lower temperatures than those needed to provide the activation energy. Under boundary lubrication conditions, a clean surface exposed as a result of mechanical activity of the solid surface is extremely reactive, especially in the case of metals. This review mostly relates to the tribochemistry of aluminium, and discusses the tribological characteristics of alcohol‐ and amine‐type liquids used as either additives or lubricants to lubricate aluminium and its alloys under boundary friction conditions. Although tribochemical reactions during sliding are perceived in various ways, here the emphasis is on the negative‐ion‐radical action mechanism (NIRAM) approach. This review addresses the question as to how present knowledge of tribochemistry can be applied to the elucidation of the mechanisms of action by which the boundary lubricant compounds considered reduce aluminium‐on‐aluminium, steel‐on‐aluminium, and aluminium‐on‐steel wear. Also, information and a discussion on the tribological behaviour of other additives and/or lubricants in relation to the friction and wear of aluminium and its alloys are presented. A concise review of the most recent work on the tribochemistry of selected fluorinated alcohols is also included.
Action mechanisms of boundary lubrication additives — A review, Part I
Authors: Choudhary R. B. , Jha M. K.
Published: July 2006

A wide range of literature has been published in the period 1950–2000 concerning emerging concepts relating to the action mechanisms of boundary lubrication additives. Some of the details of these additives in terms of chemical nature, surface adsorption, surface film generation, thermal stability, thermodynamics of contact surfaces, and rise in surface temperature, as reported in this literature, are reviewed in the present paper. It has been observed that the chemical constituents of boundary lubrication additives, particularly of organosulphur and organosulphur—phosphorus origin, are very complex in nature and no comprehensive details are readily available. Regarding action mechanisms, different researchers have suggested different mechanisms for different conditions. However, information on the thermodynamics of surfaces and thermal stability of additives is not readily available. Other details, such as the effect of sliding speed, operating load, surface roughness, and material design, are not covered in this paper. Overall, the literature reveals that attempts to correlate additive characteristics with boundary lubrication activity have met with limited success, and efforts aimed at achieving ever‐increasing performance levels are continuing.

In this first part, the authors examine the chemical nature of boundary lubrication additives, the surface films produced, and surface temperature.
The influence of soot and dispersant on ZDDP film thickness and friction
Authors: Ratoi M. , Castle R. C. , Bovington C. H. , Spikes H. A.
Published: July 2006

The effect of dispersed soot in engine oils is an increasingly important issue in terms of both engine durability and fuel efficiency. Using carbon black as a soot analogue, a study has been carried out to investigate the main factors that determine the impact of soot on friction and ZDDP film formation in formulated oils. It has been found that dispersed carbon black can rapidly remove ZDDP reaction films by abrasion. However, this removal can be prevented or limited by the choice of an optimal dispersant additive.
Pressure distribution in a curvilinear hydrostatic bearing lubricated by a micropolar fluid in the presence of a cross magnetic field
Authors: Walicka A. , Walicki E.
Published: July 2006

The flow of a micropolar fluid in the clearance of a curvilinear hydrostatic thrust bearing in the presence of a cross magnetic field was considered. By solving the equations of motion for the orthogonal curvilinear coordinate system, a formula describing the pressure distribution was obtained. Plane and spherical thrust bearings were considered as examples.
The effect of ZDDP and MoDTC additives in engine oil on the friction properties of DLC‐coated and steel cam followers
Authors: Kano M. , Yasuda Y. , Ye J. P.
Published: July 2006

Friction tests simulating cam follower sliding conditions were conducted using a pin‐on‐disc test rig. In the case of SAE 5W‐30 class engine oil, the friction coefficient of the combination of steel pins sliding on a steel disc increased from 0.11 to 0.12, while that of steel pins sliding on a diamond‐like carbon (DLC)‐coated disc decreased from 0.12 to 0.10. For 5W‐20 oil containing the friction modifier MoDTC (molybdenum dithio‐carbamates), the friction coefficient of steel pins sliding on a steel disc decreased markedly from 0.12 to 0.04. In contrast, that of steel pins sliding on a DLC‐coated disc decreased more moderately, from 0.11 to 0.08. In both cases, Zn, P, S, and Mo elements derived from ZDDP (zinc dialkyldithiophosphate) and MoDTC additives were not detected on the DLC‐coated disc, while these elements were detected on the steel disc and pins using electron probe microanalysis and X‐ray photo‐electron spectroscopy surface analysis. It appears that a tribochemical reaction film did not form on the DLC material due to its inactive chemical properties. Therefore, an increase in friction due to the formation of the film derived from ZDDP and a decrease in friction due to the formation of the film derived from MoDTC were clearly suppressed in the case of the steel pins sliding on the DLC‐coated disc. It is thought that the tribo‐chemical reaction film was instrumental in reducing friction substantially. The lateral force of the film formed on the steel disc was then measured using an atomic force microscopy lateral force microscopy test. The lateral force of the film resulting from the 5W‐30 oil was much higher than that of the film formed from the 5W‐20 oil with MoDTC. This result coincided well with the results of the friction tests. Judging from these results, it is thought that the high friction coefficient observed for the steel pins on the steel disc for the 5W‐30 oil was caused by the higher shear strength of the film formed from ZDDP. On the other hand, the very low friction coefficient observed for the steel pin‐steel disc combination for the 5W‐20 oil was presumably caused by the formation of a solid MoS2 lubricant from the MoDTC additive.
Low level laser therapy partially restores trachea muscle relaxation response in rats with tumor necrosis factor α‐mediated smooth airway muscle dysfunction
Authors: Aimbire F. , Bjordal J.M. , Iversen V.V. , Albertini R. , Frigo L. , Pacheco M.T.T. , Castro‐Faria‐Neto H.C. , Chavantes M.C. , Labat R.M. , Lopes‐Martins R.A.B.
Published: July 2006

Background and Objective

It is unknown if the decreased ability to relax airway smooth muscles in asthma and other inflammatory airways disorders can be influenced by low level laser therapy (LLLT) irradiation. To investigate if LLLT could reduce impairment in inflamed trachea smooth muscles (TSM) in rats.

Study Design/Materials and Methods

Controlled rat study where trachea was dissected and mounted in an organ bath apparatus with or without a TNF‐α solution.

Results

Low level laser therapy administered perpendicularly to a point in the middle of the dissected trachea with a wavelength of 655 nm and a dose of 2.6 J/cm2, partially restored TSM relaxation response to isoproterenol. Tension reduction was 47.0 % (±2.85) in the laser‐irradiated group compared to 22.0% (±2.21) in the control group (P < 0.01). Accumulation of cAMP was almost normalized after LLLT at 22.3 pmol/mg (±2.1) compared to 17.6 pmol/mg (±2.1) in the non‐irradiated control group (P < 0.01).

Conclusion

Low level laser therapy partially restores the normal relaxation response in inflamed TSM and normalizes accumulation of cAMP in the presence of isoproterenol. Lasers Surg. Med. 38:773–778, 2006. © 2006 Wiley‐Liss, Inc.
Glass transition of crosslinked polystyrene shells formed on the surface of calcium carbonate whisker
Authors: Sasaki Takashi , Kawagoe Shoko , Mitsuya Hajime , Irie Satoshi , Sakurai Kensuke
Published: July 2006

Glass transition of core/shell capsules consisting of calcium carbonate whisker as a core and crosslinked polystyrene as a shell was studied by differential scanning calorimetry. The thickness of the crosslinked shell was in the range of 26–81 nm. The crosslinked shells were revealed to show higher glass transition temperatures (Tg) than the corresponding bulk values. It was revealed that a thicker shell exhibits a lower Tg than a thinner shell, and that capsules without core (hollow capsules) exhibit lower Tg's than the corresponding core/shell capsules. These results suggest that the interfacial molecular interaction plays a role in the segmental relaxation, which is responsible for the glass transition. The difference in Tg between the core/shell and hollow samples was reduced when a coupling agent, methacrylic acid 3‐(trimethoxysilyl)propyl ester, was not included. This also suggests the interfacial effect on Tg. However, the results still suggest that the enhancement of Tg for the present crosslinked shells is not only due to the interfacial effect but also to the effects of chain configuration and heterogeneous crosslink. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2475–2485, 2006
Thermal properties and fracture toughness of a liquid‐crystalline epoxy resin cured with an aromatic diamine crosslinker having a mesogenic group
Authors: Harada Miyuki , Watanabe Yutaka , Tanaka Yuko , Ochi Mitsukazu
Published: July 2006

A mesogenic‐type curing agent was synthesized to introduce a mesogenic group not only into epoxy resin backbones but also into the crosslink units. In the mesogenic curing agent system, the domain size became larger, and the network arrangement in each domain existed to a greater extent than that in a system cured with the ordinary diamine curing system according to the evidence from polarized optical micrographs and polarized Fourier transform infrared mapping measurements. Moreover, the fracture toughness of the system was considerably improved. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2486–2494, 2006
KL4‐surfactant prevents hyperoxic and LPS‐induced lung injury in mice
Authors: Kinniry Paul , Pick Jeremy , Stephens Scott , Jain Deepika , Solomides Charalambos C. , Niven Ralph , Segal Robert , Christofidou‐Solomidou Melpo
Published: July 2006

KL4‐surfactant contains the novel KL4 peptide, sinapultide, which mimics properties of the hydrophobic pulmonary surfactant protein SP‐B, in a phospholipid formulation and may be lung protective in experimental acute respiratory distress syndrome/acute lung injury. Our objective was to determine the protective role of airway delivery of KL4‐surfactant in murine models of hyperoxic and lipopolysaccharide (LPS)‐induced lung injury and further explore the mechanisms of protection. For the hyperoxic injury model, mice exposed to 80% O2 for 6 days received an intranasal bolus of vehicle, beractant, or KL4‐surfactant on days 3, 4, 5, and 6 of the exposure, and lungs were evaluated on day 7. Mice in the LPS‐induced lung injury model received an intratracheal bolus of LPS followed by an intranasal bolus of KL4‐surfactant or control at 1, 3, and 19 hr post‐LPS challenge, and lungs were evaluated after 24 hr. To explore the mechanisms of protection, in vitro assays were performed with human and murine endothelial cell monolayers, and polymorphonuclear leukocyte (PMN) transmigration in the presence or absence of KL4‐surfactant or lipid controls was evaluated. Based on morphology, histopathology, white blood cell count, percentage of PMNs, and protein concentration in bronchoalveolar lavage fluid, our data showed KL4‐surfactant, unlike vehicle or beractant, blocked neutrophil influx into alveoli and suppressed lung injury. Furthermore, in vitro assays showed KL4‐surfactant decreased neutrophil transmigration at the endothelial cell level. KL4‐surfactant decreased inflammation and lung permeability compared with controls in both mouse models of lung injury. Evidence suggests the anti‐inflammatory mechanism of the KL4‐peptide is through inhibition of PMN transmigration through the endothelium. Pediatr Pulmonol. 2006, 41:916–928. © 2006 Wiley‐Liss, Inc.
Modifications to HEDIS and CSTE algorithms improve case recognition of pediatric asthma
Authors: Wakefield Dorothy B. , Cloutier Michelle M.
Published: July 2006

Our objective was to validate the Council of State and Territorial Epidemiologists (CSTE) definition of “probable” asthma and the Health Plan Employer Data and Information Set (HEDIS) definition of persistent asthma for diagnosis of pediatric asthma, and examine modifications that improve case recognition. CSTE and HEDIS criteria were applied to a cross‐sectional study of 3,905 Medicaid children with physician‐confirmed diagnosis of asthma/no asthma using a validated survey instrument based upon National Asthma Education and Prevention Program (NAEPP) Guidelines. Modified criteria were applied to another group of 1,458 non‐Medicaid children from a managed care organization (MCO). Of 1,852 Medicaid children with physician‐confirmed asthma, 906 had persistent asthma. CSTE identified 61% of children with “probable” asthma; HEDIS identified 44% of children with persistent asthma. Correct identification increased with greater disease severity. A modified CSTE increased sensitivity from 0.61 to 0.90, while maintaining high specificity. Three new HEDIS algorithms increased sensitivity from 0.44 to >0.84, with specificity >0.89. When applied prospectively to MCO children, these new algorithms demonstrated improved sensitivity. In conclusion, studies using current CSTE or HEDIS algorithms for case recognition underestimate asthma prevalence and overestimate asthma severity in children. Modified algorithms improve the identification of “probable” and persistent asthma. Pediatr Pulmonol. 2006, 41:962–971. © 2006 Wiley‐Liss, Inc.
Bogoliubov‐normal interaction and calculation of thermal conductivity of superfluid A1‐3He
Authors: Afzali R. , Ebrahimian N.
Published: July 2006

The diffusive thermal conductivity tensor of the A 1‐phase of superfluid 3He at low temperatures and melting pressure are calculated by s‐p approximation, by using the Boltzmann equation approach. We obtain that the elements of the diffusive thermal conductivities, Kxx, Kyy, and Kzz, are proportional to T –1. Then we compare the results of this paper and our results of thermal conductivity based on Pfitzner procedure. Temperature dependence of both results is equal but numerical coefficients of them are little different. Also we show that Boguliubov‐normal interaction is important in comparison to other interactions. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Weak‐field thermal Hall conductivity of YBa2Cu3O6.99 at low temperature
Authors: Shahzamanian A. , Yavary H. , Yousefvand A.
Published: July 2006

We calculate the thermal Hall conductivity of YBa2Cu3O6.99 by using Kubo formula approach. The longitudinal thermal conductivity, Kxx,is calculated and then by the relation between Kxx and Kxy the thermal Hall conductivity is evaluated. Our results show an increase in the thermal Hall conductivity with the applied field at low temperatures and weak field, i.e. K xy ∼ T √H. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic of vortices in YBa2Cu3O7–δ single crystal near the temperature of the vortex glass transition by the use of voltage noise measurements
Authors: Bghour M. , Labrag A. , Bouaaddi A. , Abaragh A. , Ramzi A. , Taoufik A. , Senoussi S.
Published: July 2006

We have studied the voltage noise Vn and the voltage noise spectral density SV of YBa2Cu3O7–δ superconductor in the regime of high magnetic field. Our studies were performed in a large range of temperature T (70 K‐90 K) covering the vortex‐glass ‐ vortex‐liquid transition which appears at Tg temperature. The sample is driving by a current I = 1 nA, under a different high magnetic fields H (2.4 T, and 5 T). The noise spectral density noted SV(f) exhibits a 1/fα. Approaching Tg the vortex glass transition, the voltage noise spectral density SV(T) is found to vanish critically according to the critical power law SV ∝ (T‐Tg)x, with x = 1.64 ± 0.1 which represents the critical exponent. The behaviour exhibited by Sv(T) cannot be simply interpreted by thermal fluctuations as we conclude by comparing SV(T) with (dR/dT)2 curve. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Partial substitution of calcium in Bi‐Sr‐Ca‐Cu‐O superconductor
Authors: Sýkorová D. , Smrčková O. , Michna E.
Published: July 2006

Chemical substitutions may change structural and physical parameters in HTS. Substituents influence formation of Bi‐2223 phase, pinning centers, intergrain connection and change hole carrier concentration. Bulk samples with partial substitution of calcium in Bi3.2Pb0.8Sr4Ca5–yMxCu7Oy by 5 B elements (M = V, Nb, Ta), x = 0–0.8 were prepared by solid state reaction in air. Resistivity and magnetic susceptibility measurements evaluated superconducting properties. Phase composition was checked by X‐ray diffraction (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bi‐based superconductors with nanosized silver dopant
Authors: Sýkorová D. , Jakeš V. , Smrčková O.
Published: July 2006

The effect of nanosized silver on formation and transport properties of Bi‐2223 phase was studied. Samples with nominal composition Bi3.2Pb0.8Sr4Ca5Cu7Ox were prepared by solid state synthesis. Ag as additive was used in three different weight percentage 5, 10 and 15. Ag powder was added to the initial mixture or after second calcination. All samples have critical temperature Tc in the range 108‐109 K. An increase of the Bi‐2223 phase content was observed at Ag concentration 10 wt%. Prolonged sintering time (400 h) improved critical current density Jc(77) above the value of the undoped sample. The values of porosity and density of the long sintered samples demonstrated their densification. The SEM micrographs have shown that addition of the silver improves the connectivity between the grains. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transport in MgB2near critical temperature
Authors: Vašek P.
Published: July 2006

Longitudinal and transverse voltages have been studied on samples of MgB2. The non‐zero transverse voltage has been observed in close vicinity of critical temperature in zero external magnetic field while far enough from Tc this voltage has been zero. It merges into transverse even voltage in magnetic field which is suppressed with increasing field and increasing transport current as well. New scaling between transverse and longitudinal resistivities has been observed in the formρxy∼ dρxx/dT. Several models trying to explain observed results are discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Changing an insulating state with Wigner‐like correlations into a superconductor with applications to doped fullerides
Authors: Squire Richard H. , March Norman H.
Published: July 2006

We propose a microscopic mechanism for superconductivity in an alkali‐metal doped fulleride. Support is given for the notion that a fulleride doped with two electrons exhibits Wigner‐like correlations. Doping a third electron into this system leads to a transition to superconductivity. The present work has expanded interactions to include not only Wigner‐like correlations between electrons, but also phonons and plasmons. The strength and influence of the numerous interactions are discussed. In the latter context, a “Marel plot” is briefly considered along with electron energy loss measurements. Lastly, we propose that a “soft” electron‐pair quasi‐particle is involved in pairing. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Orbital‐dependent representation of the correlation energy functional: Properties of second‐order Kohn–Sham perturbation expansion
Authors: Engel E. , Jiang H.
Published: July 2006

Exchange‐correlation energy functionals depending on the Kohn–Sham (KS) orbitals and eigenvalues promise to resolve some of the most pressing deficiencies of the local density and generalized gradient approximations. Such functionals can be derived in first‐principles fashion by use of standard many‐body techniques, using the KS single‐particle Hamiltonian as noninteracting reference Hamiltonian. In this way, one can establish an exact relation for the exchange‐correlation functional, which provides several options for the derivation and treatment of approximate functionals. Straightforward expansion in powers of the electron–electron coupling constant gives, to first order, the exact exchange of density functional theory (DFT) and, to second order, the simplest first‐principles correlation functional. The properties of this second‐order correlation functional are reviewed in detail. It is demonstrated that this functional reproduces both the shell structure in the exact correlation potential and dispersion effects. In response to the variational instability of the functional, observed for the Be atom, a simple and computationally efficient extension is suggested and is shown to be quite accurate for the atomic systems considered so far. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
A statistical model describing wear traces in three‐body abrasion
Authors: Fang Liang , Zhou Qingde
Published: July 2006

Cutting wear is a mechanism by which material is removed through three‐body abrasion. In the present paper, a statistical model describing the wear traces on a worn surface is proposed for three‐body abrasion, to estimate cutting wear as a proportion of the total wear of the test materials. Using this model, a statistical analysis of the traces on the worn surface was made after short‐travel, three‐body abrasion tests. The results showed that cutting was not a great proportion of the total wear of the test materials under the conditions of three‐body abrasion.
Development of laboratory tests to predict the lubricity properties of diesel fuels and their application to the development of highly refined diesel fuels
Authors: Bovington C. , Caprotti R. , Meyer K. , Spikes H. A.
Published: July 2006

In the last few years there has been an increasing requirement for the provision of environmentally benign diesel fuels. However, the introduction of such fuels into service has been associated with high levels of field failure of rotary distribution fuel pumps due to wear. This is because the refining processes necessary to produce ecologically acceptable fuels result in greatly reduced levels of sulphur compounds, aromatics, and polar material, many of which are potential lubricity agents.

This paper describes the development of bench test methods to evaluate diesel fuel lubricity and thus enable the identification of appropriate ‘solutions’.

It has been found that the key to obtaining good correlation between field experience and bench tests is (1) to reproduce the thermal conditions present in operating pump contacts and (2) to ensure that the same mechanisms of wear operate in the bench test as in the pump environment. The physical and chemical processes involved in the lubrication of fuel pumps and the influence of temperature on these processes are outlined.

As a result of the work described in this paper, effective additive solutions have been discovered for controlling the failure of diesel fuel pumps in the field and a provisional ISO (ISO/TC 22 / SC 7 M595: ‘Diesel engines ‐ diesel fuel ‐ performance requirement and test method for assessing fuel lubricity’) and CEC test method for assessing diesel fuel lubricity has also been developed.
The effect of surface chemistry in lubrication on the tribological behaviour of steel rollers under rolling‐sliding contacts
Authors: Lin Jen Fin , Chou Chau Chang , Chen San Tong
Published: July 2006

Experiments were carried out on a wear test machine utilising a gearcam adapter to simulate line‐contact lubrication. Due to the formation of a surface adsorption layer on the steel substrate, the tribological performance was detected by measuring the voltage for a lubricant with various additive concentrations. The roller wear rate was found to be strongly dependent upon both the rising rate of voltage in the wear process and the time period needed to create a positive voltage. The antiwear effect of differing additive concentrations was evaluated using the measurements of voltage for various operating conditions. An increase in rotational speed, with a lubricating oil with a low additive concentration, decreases the wear rate. A lubricating oil with a high additive concentration does little to decrease the wear rate at low rotational speeds.
An experimental investigation into the wear of the cylinder liner‐piston ring in engines
Authors: Yingcai Zhang , Yun Lu , Houjun Zhang
Published: July 2006

In order to meet the demands of different engines, various kinds of material are used for the cylinder liners and piston rings. This paper describes a method and the results of wear tests for various liners and rings. These experiments were carried out on a FGM‐1 wear simulation testing machine. The results help contribute to the rational selection and pairing of the liners and the rings.
Condition monitoring of industrial machinery through lubricant oil analysis
Authors: de A. Leão V. M. , Jones M. H. , Roylance B. J.
Published: July 2006

A number of techniques exist that can be used to determine the condition of a machine by analysing a sample of the lubricant. However, there are only a few available techniques that can be used to determine the effect of more than one cause of deterioration with a single method of analysis.

By sensing changes in the dielectric of the lubricant, it is possible to obtain information relating to both the deterioration of the machine by means of wear products, and the influence of any solid and liquid contaminants present in the lubricant.

In this paper, the principle of operation for this method is described, and the results of some controlled tests are reported in which comparisons are made with results obtained using other types of ‘health’ monitor.
Erosive wear of selected metals in coal washing environments
Authors: Yinghuai Qiang , Renli Fu , Dunlun Zhu
Published: July 2006

A slurry erosive wear apparatus developed by the authors has been used to test the erosive wear behaviour of selected metals in coal washing environments.

The erosive wear test machine was employed to determine the effects of (1) carbon content in carbon steels, (2) chromium content in alloy steels, and (3) corrosion of aqueous solutions on the erosive wear behaviour of metals. The test results revealed that the carbon content in annealed carbon steels slightly affects the erosive wear resistance of metals, while the increase in chromium content of alloy steels apparently improves the erosive wear resistance of metals and, when a corrosion inhibitor is added to slurries, the erosive wear rates of metals reduces significantly.

Two types of micro‐mechanism were deduced from the observation of eroded surfaces by SEM: (1) local exfoliation, and (2) micro‐cutting. The corrosion inhibitor can alter the micro‐mechanism from local exfoliation to micro‐cutting. The analyses show that the erosive wear of selected metals in slurries results from the synergistic effects of wear by solid particles plus fluid corrosion.
Prediction of bearing corrosion and correlation with the petter W1 L engine test
Authors: Goujon G. , Abellaneda G. , Desvard A. , Hipeaux J. C.
Published: July 2006

Among the engine oil tests required by European and American specifications, is a test of copper‐lead piston rod bearing resistance to corrosion. This is carried out on a single‐cylinder Fetter W1 L or Labeco CLR engine.

Using the same oils, a GFC

French co‐ordinating group for the development of performance tests for fuels, engine oils, and other transportation lubricants.

working group responsible for developing laboratory test methods for screening lubricants, has devised a test for studying the corrosion behaviour of a lead sample. In the presence of copper, it is immersed in the test lubricant, which is subjected to severe oxidation conditions, in the presence of air, at high temperature. The results obtained from this test agreed perfectly with the engine test results. Furthermore, the laboratory test showed good repeatability and reproducibility.
Tribological behaviour of plasma sprayed Al2O3 and TiO2 ceramic hard coatings under dry contact
Authors: Krishna Kumar V. , Swarnamani S.
Published: July 2006

Plasma sprayed ceramic coatings are used in a number of industries in which surface modification of components to compare tribological properties is important: so hence, are evaluations of their tribological properties. This paper presents a study on the wear behaviour of three ceramic coatings — Al2O3, TiO2 and Al2O3‐TiO2combination — in the load and speed ranges of 5 to 50 N, and 0.3 to 10 m/s, respectively, on which few data are available in the literature. The tests were carried out using a standard dry sand rubber wheel abrasion test and a pin‐on‐disc machine under dry sliding conditions. It was found that a stick‐slip effect seems to occur at low sliding speeds, and transition takes place at a sliding speed of around 4 m/s. Of the three ceramic coatings, TiO2 was found to be the most wear resistant, with the least friction coefficient, although it is less hard than the Al2O3 coatings. Scanning electron microscopy of the surface shows evidence of wear mechanisms such as plastic deformation, transfer‐film formation, micro cracks, and grain pull‐out in the coatings.
A screening test for anti‐wear additives in a modified four‐ball test
Authors: Cazin J. , Téqui P. , Lesieur Y.
Published: July 2006

Modern engine tests that evaluate the anti‐wear properties of automotive engine oils are increasingly sophisticated and expensive, and often have relatively poor precision. The development of a simple, inexpensive, and reliable bench test to screen the anti‐wear properties of fully formulated engine oils prior to their testing in engines is therefore very attractive. Numerous methods already exist, but they typically measure wear only at the end of the test by measuring the consequences of wear. The present paper describes an alternative approach, its purpose being the comparative evaluation of the anti‐wear performance of lubricants throughout the test under variable load. A four‐ball machine was used as a test rig for this work, and was equipped with instruments allowing study of the oil bath temperature, load applied to the balls, and the displacement of the load lever arm.

The work presented focuses on a test procedure containing the following important elements: pre‐ageing of oils, test start‐up at very low load, incremental increases in load, stepwise increase in load, with each step sufficiently long to allow system equilibrium.

Recording and analysis of the temperature and arm displacement curves permit the recognition of two distinct forms of wear: slow and gradual abrasive wear, and sudden and intense adhesive wear (scuffing). The presence and the intensity of the latter were found to have a direct relation with the anti‐wear performance of candidate oils in the API Sequence VE engine test. The procedure ranked oils correctly in relation to their dithiophosphate concentration, correctly distinguished secondary and primary zinc dithiophosphates and, more interestingly, predicted the positive effects of some ashless anti‐wear additives in accordance with results obtained in the Sequence VE.
Examination of tribological properties of plasma surface layer using special test equipment
Authors: Škoriˇ B. , Kakaš D.
Published: July 2006

The hardness, adhesion, and tribological behaviour of magnetron‐deposited coatings (TiN and (Ti,Al)N) have been determined and related to microstructure composition. To enhance the adhesion of the coating, plasma nitriding of substrates was employed. Wear behaviour, coefficient of friction and contact temperature were measured using computerised data acquisition and processing. The bonding force between the coated samples and counter material was monitored and controlled by newly designed and constructed equipment, to keep a constant level of load during sliding. With the new hardware and software, it was possible to monitor on‐line the development of the wear process. The hardware consisted of PC computer, piezoelectric transducer, sensors with high sensitivity, microprocessor‐controlled measuring system, AD/DA transformer, and multichannel plotter. The wear zone morphology and characteristics of the surface layer structure and other important properties were investigated using scanning electron microscopy (SEM) and X‐ray diffraction analysis (XRD). Energy dispersive X‐ray analysis (EDAX) of the wear scars on pins provided essential information on the wear characteristics. Based on the results, the correlations between the mechanical properties, the surface structure, and tribological characteristics are explained.
Method for continuous detection of different friction and wear regimes and application to the behaviour of ceramics at high temperature
Authors: Dalverny Olivier , Denape Jean
Published: July 2006

This paper describes tests carried out on a tribometer functioning at high temperature and equipped to record continuously the various test parameters, namely, the normal applied load, the tangential friction force, the differential movement of the contact surfaces, and the temperature of the sample. Dry friction tests, conducted on two aluminas of different purities, showed different degradation regimes at both 20 and 800°C. Thus, three successive periods of functioning were identified and correlated with transitions in the mechanism of degradation of the surfaces or in the mechanism of interfacial adaptation in the contact. The first period corresponds basically to the adaptation mechanisms of the interfaces with no wear material generated. The two subsequent periods demonstrate the degradation mechanisms of the surfaces leading to the production of more or less wear material and resulting in different states of equilibrium between production, recirculation, and loss of wear debris through the contact.
Determination of Calcium, Zinc, and Phosphorus in multigrade crankcase oils by XRF, DRES, and ICP‐AES
Authors: Patel M. B. , Christopher J. , Jain S. K. , Srivastava S. P. , Bhatnagar A. K.
Published: July 2006

The effect of viscosity index improvers such as styrene‐isoprene copolymer (SICP), styrene‐butadiene copolymer (SBCP), ethylene‐propylene copolymer (OCP) and poly(alkyl) methacrylate (PMA), in multigrade oils on the determination of Ca, Zn and P in fresh and used lubricating oils was studied using XRF, DRES and ICP‐AES techniques. Crankcase lubricating oil blends containing known amounts of Ca (2900 ppm), Zn (1700 ppm) and P (1600 ppm) were further formulated with different concentrations of these VI improvers and analysed for their Ca, Zn, and P contents by XRF, DRES and ICP‐AES. Based on a comparison of the resulting analytical data, it was concluded that the VI improvers had no effect on the analysis results, and that the concentrations of Ca, Zn and P in the oil determined by these techniques correlate well with each other.
Determination of the Bingham parameters of an electrorheological fluid in an axial flow concentric‐cylinder rheometer
Authors: Kohl James G. , Tichy John A. , Craig Kevin C. , Malcolm Skye M.
Published: July 2006

Electrorheological (ER) fluids are fluids that undergo changes in their rheological properties in the presence of an applied electrical field. The change in the flow properties with an applied electrical field has led to their being investigated for use as ‘smart’ lubricants. The Bingham model is currently used to describe the behaviour of these fluids. In this work, the Bingham model parameters of a commercially available ER fluid are obtained using an axial flow concentric‐cylinder rheometer. Two methods are used to determine these parameters. One is the Weissenberg (—Rabinowitsch) method applied to thin annular slits, to obtain corrected stress—strain rate information. The other method involves directly fitting the velocity—pressure curve data to the axial flow rate equation of a Bingham fluid through concentric cylinders. The results obtained by these two methods differ by as much as 49.4 and 63.5% for the yield stress and viscosity, respectively.

It is observed for this ER fluid that the yield stress increases according to a power law relationship with the applied electrical field. The viscosity appears to decrease linearly with an increase in the applied electrical field.