http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2013 , Hindawi Publishing Corporation . All rights reserved. Thu, 18 Apr 2013 09:42:09 +0000 http://www.hindawi.com/journals/at/2013/574158/ Bruno Marchon, Norio Tagawa, Bo Liu, Tom Karis, and Jia-Yang Juang Copyright © 2013 Bruno Marchon et al. All rights reserved. Wed, 10 Apr 2013 08:57:12 +0000 http://www.hindawi.com/journals/at/2013/794151/ The challenges in designing future head disk interface (HDI) demand efficient theoretical modeling tools with flexibility in investigating various combinations of perfluoropolyether (PFPE) and carbon overcoat (COC) materials. For broad range of time and length scales, we developed multiscale/multiphysical modeling approach, which can bring paradigm-shifting improvements in advanced HDI design. In this paper, we introduce our multiscale modeling methodology with an effective strategic framework for the HDI system. Our multiscale methodology in this paper adopts a bottom to top approach beginning with the high-resolution modeling, which describes the intramolecular/intermolecular PFPE-COC degrees of freedom governing the functional oligomeric molecular conformations on the carbon surfaces. By introducing methodology for integrating atomistic/molecular/mesoscale levels via coarse-graining procedures, we investigated static and dynamic properties of PFPE-COC combinations with various molecular architectures. By bridging the atomistic and molecular scales, we are able to systematically incorporate first-principle physics into molecular models, thereby demonstrating a pathway for designing materials based on molecular architecture. We also discussed future materials (e.g., graphene for COC, star-like PFPEs) and systems (e.g., heat-assisted magnetic recording (HAMR)) with higher scale modeling methodology, which enables the incorporation of molecular/mesoscale information into the continuum scale models. Myung S. Jhon, Pil Seung Chung, Robert L. Smith, and Lorenz T. Biegler Copyright © 2013 Myung S. Jhon et al. All rights reserved. Mon, 25 Mar 2013 16:59:37 +0000 http://www.hindawi.com/journals/at/2013/918387/ We analyse in terms of efficiency and traction capabilities a recently patented traction drive, referred to as the double roller full-toroidal variator (DFTV). We compare its performance with the single roller full-toroidal variator (SFTV) and the single roller half-toroidal variator (SHTV). Modeling of these variators involves challenging tribological issues; the traction and efficiency performances depend on tribological phenomena occurring at the interface between rollers and disks, where the lubricant undergoes very severe elastohydrodynamic lubrication regimes. Interestingly, the DFTV shows an improvement of the mechanical efficiency over a wide range of transmission ratios and in particular at the unit speed ratio as in such conditions in which the DFTV allows for zero-spin, thus strongly enhancing its traction capabilities. The very high mechanical efficiency and traction performances of the DFTV are exploited to investigate the performance of a flywheel-based Kinetic Energy Recovery System (KERS), where the efficiency of the variator plays an important role in determining the overall energy recovery performance. The energy boost capabilities and the round-trip efficiency are calculated for the three different variators considered in this study. The results suggest that the energy recovery potential of the mechanical KERS can be improved with a proper choice of the variator. Francesco Bottiglione, Giuseppe Carbone, Leonardo De Novellis, Luigi Mangialardi, and Giacomo Mantriota Copyright © 2013 Francesco Bottiglione et al. All rights reserved. Thu, 21 Mar 2013 18:01:18 +0000 http://www.hindawi.com/journals/at/2013/492858/ Nitrogen implantation in Interstitial-Free steel was evaluated for its impact on metal transfer and 1100 Al rider wear. It was determined that nitrogen implantation reduced metal transfer in a trend that increased with dose; the Archard wear coefficient reductions of two orders of magnitude were achieved using a dose of 2e17 ions/cm2, 100 kV. Cold-rolling the steel and making volumetric wear measurements of the Al-rider determined that the hardness of the harder material had little impact on volumetric wear or friction. Nitrogen implantation had chemically affected the tribological process studied in two ways: directly reducing the rider wear and reducing the fraction of rider wear that ended up sticking to the ISF steel surface. The structure of the nitrogen in the ISF steel did not affect the tribological behavior because no differences in friction/wear measurements were detected after postimplantation heat treating to decompose the as-implanted ε-Fe3N to γ-Fe4N. The fraction of rider-wear sticking to the steel depended primarily on the near-surface nitrogen content. Covariance analysis of the debris oxygen and nitrogen contents indicated that nitrogen implantation enhanced the tribo-oxidation process with reference to the unimplanted material. As a result, the reduction in metal transfer was likely related to the observed tribo-oxidation in addition to the introduction of nitride wear elements into the debris. The primary Al rider wear mechanism was stick-slip, and implantation reduced the friction and friction noise associated with that wear mechanism. Calculations based on the Tabor junction growth formula indicate that the mitigation of the stick-slip mechanism resulted from a reduced adhesive strength at the interface during the sticking phase. Luke Autry and Harris Marcus Copyright © 2013 Luke Autry and Harris Marcus. All rights reserved. Wed, 20 Mar 2013 11:05:55 +0000 http://www.hindawi.com/journals/at/2013/521086/ This paper reviews the state of the head-disk interface (HDI) technology, and more particularly the head-medium spacing (HMS), for today’s and future hard-disk drives. Current storage areal density on a disk surface is fast approaching the one terabit per square inch mark, although the compound annual growth rate has reduced considerably from ~100%/annum in the late 1990s to 20–30% today. This rate is now lower than the historical, Moore’s law equivalent of ~40%/annum. A necessary enabler to a high areal density is the HMS, or the distance from the bottom of the read sensor on the flying head to the top of the magnetic medium on the rotating disk. This paper describes the various components of the HMS and various scenarios and challenges on how to achieve a goal of 4.0–4.5 nm for the 4 Tbit/in2 density point. Special considerations will also be given to the implication of disruptive technologies such as sealing the drive in an inert atmosphere and novel recording schemes such as bit patterned media and heat assisted magnetic recording. Bruno Marchon, Thomas Pitchford, Yiao-Tee Hsia, and Sunita Gangopadhyay Copyright © 2013 Bruno Marchon et al. All rights reserved. Tue, 19 Mar 2013 11:02:40 +0000 http://www.hindawi.com/journals/at/2013/657363/ We have developed a novel instrument combining a glide tester with an Atomic Force Microscope (AFM) for hard disk drive (HDD) media defect test and analysis. The sample stays on the same test spindle during both glide test and AFM imaging without losing the relevant coordinates. This enables an in situ evaluation with the high-resolution AFM of the defects detected by the glide test. The ability for the immediate follow-on AFM analysis solves the problem of relocating the defects quickly and accurately in the current workflow. The tool is furnished with other functions such as scribing, optical imaging, and head burnishing. Typical data generated from the tool are shown at the end of the paper. It is further demonstrated that novel experiments can be carried out on the platform by taking advantage of the correlative capabilities of the tool. Jizhong He Copyright © 2013 Jizhong He. All rights reserved. Mon, 04 Mar 2013 15:09:46 +0000 http://www.hindawi.com/journals/at/2013/352387/ The wear and friction of diamond-like nanocomposite (DLN) film have been investigated in air with different relative humidity (RH), under deionized (DI) water and saline solution. The structure of the film has been characterized by Fourier transform infrared (FTIR), Raman spectroscopy, and scanning electron microscope (SEM). The result shows two interpenetrating network structure: a–C:H and a–Si:O, and they are interpenetrated by Si–C bonding. The tribological performance has been measured using ball-on-disc tribometer with tungsten carbide ball as counterbody at 10 N normal load. Results show that with increasing relative humidity (RH) from 35% to 80%, the coefficient of friction (COF) increases gradually from 0.005 to 0.074, whereas with increasing RH the wear factor decreases from  mm3/Nm and attains a minimum value of  mm3/Nm at 50% RH. With further increase of RH the wear factor increases again. Moreover, in DI water and especially in saline solution, both the COF and wear factor have been found to be significantly low. A clue has been interpreted to understand environmental dependency, considering the effect of surface dangling bonds, charge transfer, and chemical interactions. Sukhendu Jana, Sayan Das, Utpal Gangopadhyay, Anup Mondal, and Prajit Ghosh Copyright © 2013 Sukhendu Jana et al. All rights reserved. Wed, 27 Feb 2013 10:04:26 +0000 http://www.hindawi.com/journals/at/2013/878274/ The present paper describes an experimental test and a coupled contact-thermal-wear analysis of a railway wheel/brake block system through the braking process. During the test, the friction, the generated heat, and the wear were evaluated. It was found that the contact between the brake block and the wheel occurs in relatively small and slowly moving hot spots, caused by the wear and the thermal effects. A coupled simulation method was developed including numerical frictional contact, transient thermal and incremental wear calculations. In the 3D simulation, the effects of the friction, the thermal expansion, the wear, and the temperature-dependent material properties were also considered. A good agreement was found between the results of the test and the calculations, both for the thermal and wear results. The proposed method is suitable for modelling the slowly oscillating wear caused by the thermal expansions in the contact area. Nándor Békési and Károly Váradi Copyright © 2013 Nándor Békési and Károly Váradi. All rights reserved. Sun, 24 Feb 2013 08:44:29 +0000 http://www.hindawi.com/journals/at/2013/519686/ Analyzing wear mechanisms and developments of surface layers in WC/Co-cemented carbide cutting inserts is of great importance for metal-cutting manufacturing. By knowing relevant processes within the surface layers of cutting tools during machining the choice of machining parameters can be influenced to get less wear and high tool life of the cutting tool. Tool wear obviously influences tool life and surface integrity of the workpiece (residual stresses, surface quality, work hardening, etc.), so the choice of optimised process parameters is of great relevance. Vapour-deposited coatings on WC/Co-cemented carbide cutting inserts are known to improve machining performance and tool life, but the mechanisms behind these improvements are not fully understood. The interaction between commercial TiN-coated and uncoated WC/Co-cemented carbide cutting inserts and a normalised SAE 1045 steel workpiece was investigated during a dry plain turning operation with constant material removal under varied machining parameters. Tool wear was assessed by light-optical microscopy, scanning electron microscopy (SEM), and EDX analysis. The state of surface layer was investigated by metallographic sectioning. Microstructural changes and material transfer due to tribological processes in the cutting zone were examined by SEM and EDX analyses. Johannes Kümmel, Katja Poser, Frederik Zanger, Jürgen Michna, and Volker Schulze Copyright © 2013 Johannes Kümmel et al. All rights reserved. Mon, 04 Feb 2013 14:47:50 +0000 http://www.hindawi.com/journals/at/2013/212568/ The aim of this work is related to an analysis of journal bearings lubrication using non-Newtonian fluids which are described by a power-law model. The performance characteristics of the journal bearings are determined for various values of the non-Newtonian power-law index “” which is equal to: 0.9, 1, and 1.1. Obtained numerical results show that for the dilatant fluids (), the load-carrying capacity, the pressure, the temperature, and the frictional force increased while for the pseudo-plastic fluids () they decreased. The influence of the thermal effects on these characteristics is important at higher values of the flow behavior index “.” Obtained results are compared to those obtained by others. Good agreement is observed between the different results. Abdessamed Nessil, Salah Larbi, Hacene Belhaneche, and Maamar Malki Copyright © 2013 Abdessamed Nessil et al. All rights reserved. Sun, 03 Feb 2013 14:57:10 +0000 http://www.hindawi.com/journals/at/2013/850473/ Density functional theory- (DFT-) based ab initio calculations were used to investigate the surface-to-surface interaction and frictional behavior of two hydrogenated C(100) dimer surfaces. A monolayer of hydrogen atoms was applied to the fully relaxed C(100)2x1 surface having rows of C=C dimers with a bond length of 1.39 Å. The obtained C(100)2x1-H surfaces (C–H bond length 1.15 Å) were placed in a large vacuum space and translated toward each other. A cohesive state at a surface separation of 4.32 Å that is stabilized by approximately 0.42 eV was observed. An increase in the charge separation in the surface dimer was calculated at this separation having a 0.04 e transfer from the hydrogen atom to the carbon atom. The Mayer bond orders were calculated for the C–C and C–H bonds and were found to be 0.962 and 0.947, respectively. σ C–H bonds did not change substantially from the fully separated state. A significant decrease in the electron density difference between the hydrogen atoms on opposite surfaces was seen and assigned to the effects of Pauli repulsion. The surfaces were translated relative to each other in the (100) plane, and the friction force was obtained as a function of slab spacing, which yielded a 0.157 coefficient of friction. Paul M. Jones, Huan Tang, Yiao-Tee Hsia, Xiaoping Yan, James D. Kiely, Junwei Huang, Christopher Platt, Xiaoding Ma, Michael Stirniman, and Lang Dinh Copyright © 2013 Paul M. Jones et al. All rights reserved. Mon, 21 Jan 2013 11:35:13 +0000 http://www.hindawi.com/journals/at/2013/365602/ Fly ash particles are potentially used in metal matrix composites due to their low cost, low density, and availability in large quantities as waste by-products in thermal power plants. This study describes multifactor-based experiments that were applied to research and investigation on dry sliding wear system of stir-cast aluminum alloy 6351 with 5, 10, and 15 wt.% fly ash reinforced metal matrix composites (MMCs). The effects of parameters such as load, sliding speed, and percentage of fly ash on the sliding wear, specific wear rate, and friction coefficient were analyzed using Grey relational analysis on a pin-on-disc machine. Analysis of variance (ANOVA) was also employed to investigate which design parameters significantly affect the wear behavior of the composite. The results showed that the applied load exerted the greatest effect on the dry sliding wear followed by the sliding velocity. M. Uthayakumar, S. Thirumalai Kumaran, and S. Aravindan Copyright © 2013 M. Uthayakumar et al. All rights reserved. Mon, 21 Jan 2013 11:29:54 +0000 http://www.hindawi.com/journals/at/2013/362931/ The raw and modified versions of two nonedible vegetable oils, Pongam (Pogammia pinnata) and Jatropha (Jatropha curcas), and a commercially available branded mineral oil are used as straight cutting fluids for turning AA 6061 to assess cutting forces. Minimum quantity lubrication is utilized for the supply of cutting fluids. Cutting and thrust forces are measured. Cutting power is determined for various cutting speeds, depths of cut, and feed rates. Also, drilling is performed on the material to understand the material removal rate (MRR) under these oils. The performances of vegetable oils are compared to mineral oil. A noticeable reduction in cutting forces is observed under the Jatropha family of oils compared to mineral oil. Further, better material removal rate is seen under both the vegetable oils and their versions compared to under petroleum oil for the range of thrust forces. Y. M. Shashidhara and S. R. Jayaram Copyright © 2013 Y. M. Shashidhara and S. R. Jayaram. All rights reserved. Wed, 16 Jan 2013 11:01:45 +0000 http://www.hindawi.com/journals/at/2013/987251/ Little has been published on the behaviour of polymer gears operating under lubricated conditions. An experimental and analytical programme was undertaken to classify the regimes of EHL under which polymer spur gears operate. In doing so theoretical film thicknesses were calculated and then used to classify the regime according to Johnson's Map. The effects of lubrication on the operating efficiencies of high-performance polymer gears were interpreted and from these results coefficients of friction were derived. In addition to this the effect of tooth geometry was investigated and the beneficial influence of high-pressure angle tooth geometry is demonstrated. At loads typically associated with polymer gears the operating regime is shown to be mixed film lubrication. When high-pressure angle gears were tested at high loads the operating regime became full film lubrication and relatively little tooth flank damage occurred. K. D. Dearn, T. J. Hoskins, L. Andrei, and D. Walton Copyright © 2013 K. D. Dearn et al. All rights reserved. Sun, 30 Dec 2012 09:42:29 +0000 http://www.hindawi.com/journals/at/2012/209630/ Molecularly thin lubricant films are used for the lubrication of head disk interfaces in hard disk drives. The film thickness is reduced to 1-2 nm to minimize the magnetic spacing, and optimal, precise design is required to obtain sufficient lubrication. However, until now, there was no generally applicable method for investigating such thin films. Therefore, we developed a highly sensitive shear force measuring method and have applied it to the viscoelastic measurement of lubricant films coated on magnetic disk surfaces. In this paper, we review the method and summarize the useful findings we have demonstrated so far. Shintaro Itoh, Yuya Hamamoto, Koki Ishii, Kenji Fukuzawa, and Hedong Zhang Copyright © 2012 Shintaro Itoh et al. All rights reserved. Wed, 26 Dec 2012 07:40:34 +0000 http://www.hindawi.com/journals/at/2012/923818/ We fabricated supersmooth probes for use in pin-on-disk sliding tests by applying gas cluster ion beam irradiation to glass convex lenses. In the fabrication process, various changes were made to the irradiation conditions; these included one-step irradiation of Ar clusters or two-step irradiation of Ar and N2 clusters, with or without Ar cluster-assisted tough carbon deposition prior to N2 irradiation, and the application of various ion doses onto the surface. We successfully obtained probes with a centerline averaged surface roughness that ranged widely from 1.08 to 4.30 nm. Using these probes, we measured the friction forces exerted on magnetic disks coated with a molecularly thin lubricant film. Perfluoropolyether lubricant films with different numbers of hydroxyl end groups were compared, and our results indicated that the friction force increases as the surface roughness of the pin decreases and that increases as the number of hydroxyl end groups increases. H. Tani, Y. Mitsuya, T. Kitagawa, and N. Tagawa Copyright © 2012 H. Tani et al. All rights reserved. Wed, 19 Dec 2012 13:28:24 +0000 http://www.hindawi.com/journals/at/2012/305209/ A new test method based on multipass scratch testing has been developed for evaluating the mechanical and tribological properties of thin, hard coatings. The proposed test method uses a pin-on-disc tribometer and during testing a Rockwell C diamond stylus is used as the “pin” and loaded against the rotating coated sample. The influence of normal load on the number of cycles to coating damage is investigated and the resulting coating damage mechanisms are evaluated by posttest scanning electron microscopy. The present study presents the test method by evaluating the performance of Ti0.86Si0.14N, Ti0.34Al0.66N, and (Al0.7Cr0.3)2O3 coatings deposited by cathodic arc evaporation on cemented carbide inserts. The results show that the test method is quick, simple, and reproducible and can preferably be used to obtain relevant data concerning the fatigue, wear, chipping, and spalling characteristics of different coating-substrate composites. The test method can be used as a virtually nondestructive test and, for example, be used to evaluate the fatigue and wear resistance as well as the cohesive and adhesive interfacial strength of coated cemented carbide inserts prior to cutting tests. M. Fallqvist, R. M'Saoubi, J. M. Andersson, and M. Olsson Copyright © 2012 M. Fallqvist et al. All rights reserved. Tue, 18 Dec 2012 17:53:52 +0000 http://www.hindawi.com/journals/at/2012/571036/ The use of additives (polyisobutylene, ethylene-propylene, lithium hydroxy stearate, hydrophobic silica, etc.) changes lubricants’ rheology due to which they show pseudoplastic and dilatant nature, which can be modelled as cubic stress fluid model (Rabinowitsch fluid model). The present theoretical analysis investigates the effects of non-Newtonian pseudoplastic and dilatant lubricants on the squeezing characteristics of a sphere and a flat plate. The modified Reynolds equation has been derived and an asymptotic solution for film pressure is obtained. The results for the film pressure distribution, load carrying capacity, and squeezing time characteristics have been calculated for various values of pseudoplastic parameter and compared with the Newtonian results. These characteristics show a significant variation with the non-Newtonian pseudoplastic and dilatant behavior of the fluids. Udaya P. Singh and Ram S. Gupta Copyright © 2012 Udaya P. Singh and Ram S. Gupta. All rights reserved. Mon, 17 Dec 2012 14:17:53 +0000 http://www.hindawi.com/journals/at/2012/935690/ The combined effects of couple stress and surface roughness on the MHD squeeze-film lubrication between a sphere and a porous plane surface are analyzed, based upon the thin-film magnetohydrodynamic (MHD) theory. Using Stoke’s theory to account for the couple stresses due to the microstructure additives and the Christensen’s stochastic method developed for hydrodynamic lubrication of rough surfaces derives the stochastic MHD Reynolds-type equation. The expressions for the mean MHD squeeze-film pressure, mean load-carrying capacity, and mean squeeze-film time are obtained. The results indicate that the couple stress fluid in the film region enhances the mean MHD squeeze-film pressure, load-carrying capacity, and squeeze-film time. The effect of roughness parameter is to increase (decrease) the load-carrying capacity and lengthen the response time for azimuthal (radial) roughness patterns as compared to the smooth case. Also, the effect of porous parameter is to decrease the load-carrying capacity and increase the squeeze-film time as compared to the solid case. M. Rajashekar and Biradar Kashinath Copyright © 2012 M. Rajashekar and Biradar Kashinath. All rights reserved. Thu, 13 Dec 2012 18:44:51 +0000 http://www.hindawi.com/journals/at/2012/170189/ The influence of organic compounds (OCs) on the head-disk interface (HDI) was investigated in hard disk drives. The drives were tested at high temperature to investigate the influence of gaseous OC and to confirm if the gaseous OC forms droplets on head or disk. In the experiment, errors occurred by readback signal jump and we observed the droplets on the disk after full stroke seek operation of the drive. Our results indicate that the gaseous OC condensed on the slider and caused flying instability resulting in drive failure due to slider contact with a droplet of liquid OC. Furthermore, this study shows that kinetic viscosity of OC is an important factor to cause drive failure using alkane reagents. Koji Sonoda Copyright © 2012 Koji Sonoda. All rights reserved. Wed, 12 Dec 2012 16:57:41 +0000 http://www.hindawi.com/journals/at/2012/303071/ Accurate touchdown power detection is a prerequisite for read-write head-to-disk spacing calibration and control in current hard disk drives, which use the thermal fly-height control slider technology. The slider air bearing surface and head gimbal assembly design have a significant influence on the touchdown behavior, and this paper reports experimental findings to help understand the touchdown process. The dominant modes/frequencies of excitation at touchdown can be significantly different leading to very different touchdown signatures. The pressure under the slider at touchdown and hence the thermal fly-height control efficiency as well as the propensity for lubricant pickup show correlation with touchdown behavior which may be used as metrics for designing sliders with good touchdown behavior. Experiments are devised to measure friction at the head-disk interface of a thermal fly-height control slider actuated into contact. Parametric investigations on the effect of disk roughness, disk lubricant parameters, and air bearing surface design on the friction at the head-disk interface and slider burnishing/wear are conducted and reported. Sripathi V. Canchi, David B. Bogy, Run-Han Wang, and Aravind N. Murthy Copyright © 2012 Sripathi V. Canchi et al. All rights reserved. Wed, 12 Dec 2012 09:52:58 +0000 http://www.hindawi.com/journals/at/2012/163575/ Some interactions between the dynamic and tribological behaviour of geared transmissions are examined, and a number of experimental and simulation results are compared. A model is introduced which incorporates most of the possible interactions between gears, shafts and hydrodynamic journal bearings. It combines (i) a specific element for wide-faced gears that includes the normal contact conditions between actual mating teeth, that is, with tooth shape deviations and mounting errors, (ii) shaft finite elements, and (iii) the external forces generated by journal bearings determined by directly solving Reynolds' equation. The simulation results are compared with the measurement obtained on a high-precision test rig with single-stage spur and helical gears supported by hydrodynamic journal bearings. The experimental and simulation results compare well thus validating the simulation strategy both at the global and local scales. R. Fargère and P. Velex Copyright © 2012 R. Fargère and P. Velex. All rights reserved. Mon, 03 Dec 2012 19:02:01 +0000 http://www.hindawi.com/journals/at/2012/964089/ Lower molecular weight Z-Tetraol films exhibit increased mechanical spacing in the slider-disk interface due to a lower z-profile. An increased resistance to lubricant disturbance on the disk surface (e.g., lube moguls) with decreasing film thickness is attributed to an increasing contribution from the polar component of the disjoining pressure. Evaporative loss at temperatures typically encountered in a hard-disk drive also increases with decreasing molecular weight but is strongly dependent on the initial bonded fraction. R. J. Waltman and H. Deng Copyright © 2012 R. J. Waltman and H. Deng. All rights reserved. Mon, 19 Nov 2012 16:26:14 +0000 http://www.hindawi.com/journals/at/2012/412190/ We consider the case of soft contacts in mixed lubrication conditions. We develop a novel, two scales contact algorithm in which the fluid- and asperity-asperity interactions are modeled within a deterministic or statistic scheme depending on the length scale at which those interactions are observed. In particular, the effects of large-scale roughness are deterministically calculated, whereas those of small-scale roughness are included by solving the corresponding homogenized problem. The contact scheme is then applied to the modeling of dynamic seals. The main advantage of the approach is the tunable compromise between the high-computing demanding characteristics of deterministic calculations and the much lower computing requirements of the homogenized solutions. Michele Scaraggi and Giuseppe Carbone Copyright © 2012 Michele Scaraggi and Giuseppe Carbone. All rights reserved. Sun, 11 Nov 2012 08:46:14 +0000 http://www.hindawi.com/journals/at/2012/365414/ In order to investigate the oil projected by gears rotating in an oil bath, a test rig has been set up in which the quantity of lubricant splashed at several locations on the casing walls can be measured. An oblong-shaped window of variable size is connected to a tank for flow measurements, and the system can be placed at several locations. A series of formulae have been deduced using dimensional analysis which can predict the lubricant flow rate generated by one spur gear or one disk at various places on the casing. These results have been experimentally validated over a wide range of operating conditions (rotational speed, geometry, immersion depth, etc.). G. Leprince, C. Changenet, F. Ville, and P. Velex Copyright © 2012 G. Leprince et al. All rights reserved. Sun, 21 Oct 2012 10:37:33 +0000 http://www.hindawi.com/journals/at/2012/169207/ This paper reports the effects of slider posture on the slider bearing in a heat-assisted magnetic recording (HAMR) system with the direct simulation Monte Carlo (DSMC) method. In this HAMR system, the heat issues on the slider bearings are assumed to be caused by a heated spot on the disk and/or slider body itself at various pitch angles. The simulation results show that with a heated spot on the disk, the air bearing pressure and air bearing force that acted on the slider surface will increase when the pitch angle becomes larger. It is also found that the bearing force increases with the heated spot size and the effects of a heated spot become more obvious at a larger pitch angle. On the other hand, the slider body temperature is observed to have a noticeable effect on air bearing pressure and force. The smaller pitch angle enlarges the tendency of bearing force variations with the slider temperature and makes the slider more sensitive to its temperature changes. Kyaw Sett Myo, Weidong Zhou, Xiaoyang Huang, Shengkai Yu, and Wei Hua Copyright © 2012 Kyaw Sett Myo et al. All rights reserved. Tue, 16 Oct 2012 16:24:21 +0000 http://www.hindawi.com/journals/at/2012/476028/ The priority for lubricant performance for metal V-belt-type CVT (B-CVTFs) should be the improvement of transmittable torque capacity between the belt and pulley plus excellent antishudder properties for lockup clutch used in B-CVTs. This study intends to investigate the effect of lubricant additives for improving these performances of B-CVTs. In addition, surface analysis techniques were utilized to gain a novel insight into the chemical composites and morphology of the tribofilms. As a result, it is vital for greater torque capacity to give higher boundary friction coefficient between the metal contacting interfaces, and the process of boundary lubricant film formation derived from antiwear additives used in B-CVTFs strongly impacts on the torque capacity. Moreover, it is found that a sort of lubricant formulation gave an excellent antishudder performance for wet clutch with keeping higher friction coefficient between the metals, which would result in improving the performance of B-CVTs. Keiichi Narita Copyright © 2012 Keiichi Narita. All rights reserved. Wed, 10 Oct 2012 10:24:53 +0000 http://www.hindawi.com/journals/at/2012/502714/ Features of phase-structure formation and abrasive wear resistance of composite coatings “WC-M2 steel” worn against tungsten monocarbide have been investigated. It was established that adding 20 wt.% WC to the deposited powder mixture leads to the increase in M6C carbide content. These carbides show a multimodal size distribution consisting of ~5.9 μm eutectic carbides along the grain boundaries, ~0.25 μm carbides dispersed inside the grains. Also a greater amount of metastable austenite (~88 vol.%) is found. The high abrasive wear resistance of these coatings is provided by -martensitic transformation and multimodal size distribution of reinforcing particles. S. F. Gnyusov, V. G. Durakov, and S. Yu. Tarasov Copyright © 2012 S. F. Gnyusov et al. All rights reserved. Wed, 03 Oct 2012 07:59:15 +0000 http://www.hindawi.com/journals/at/2012/898252/ The present paper deals with a theoretical analysis of 4-pocket capillary compensated conical hybrid journal bearing system operating with micropolar lubricant. The modified Reynolds equation for a conical journal bearing system operating with micropolar lubricant has been derived. In the present study, Eringen's micropolar theory has been used to model micropolar lubrication in cylindrical coordinate system. The study has been carried out for the different values of micropolar parameters, that is, characteristic length () and coupling number (). The conical bearing configurations having semicone angle 10∘, 20∘, 30∘, and 40∘ have been studied. The study suggests that micropolar lubricant offers better performance vis- á-vis Newtonian lubricant for bearing configurations having values of semicone angle 10∘and 20∘. Satish C. Sharma and Arvind K. Rajput Copyright © 2012 Satish C. Sharma and Arvind K. Rajput. All rights reserved. Tue, 02 Oct 2012 10:06:27 +0000 http://www.hindawi.com/journals/at/2012/431903/ This study evaluates the influence of independent parameters such as sliding velocity (A), normal load (B), filler content (C), and sliding distance (D) on wear performance of potassium-titanate-whiskers (PTW) reinforced epoxy composites using a statistical approach. The PTW were reinforced in epoxy resin to prepare whisker reinforced composites of different compositions using vacuum-assisted casting technique. Dry sliding wear tests were conducted using a standard pin on disc test setup following a well planned experimental schedule based on Taguchi’s orthogonal arrays. With the signal-to-noise (S/N) ratio and analysis of variance (ANOVA) optimal combination of parameters to minimize the wear rate was determined. It was found that inclusion of PTW has greatly improved the wear resistance property of the composites. Normal load was found to be the most significant factor affecting the wear rate followed by (C), (D), and (A). Interaction effects of various control parameters were less significant on wear rate of composites. M. Sudheer, Ravikantha Prabhu, K. Raju, and Thirumaleshwara Bhat Copyright © 2012 M. Sudheer et al. All rights reserved.