• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.2026-2038
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• 1994

A numerical scheme is developed for the analysis of incipient sliding contact with orthotropic friction condition subjected to tangential load and twisting moment. The inherent nonlinearity in the orthotropic friction law has been treated by a polyhedral friction law. Then, a three-dimensional linear complementarity problem(LCP) formulation in an incremental form is obtained, and the existence of a solution is investigated. A Lemke's complementary pivoting algorithm is used for solving the LCP. The scheme is illustrated by spherical contact problems, and the effects of eccentricity of elliptical friction domain on the traction and stick region are discussed.

• KSTLE International Journal
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• v.2 no.1
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• pp.22-28
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• 2001

A resin bonded copper-graphite brush was investigated to evaluate the characteristics electrical signal transmission through a sliding contact as a function of the relative amount of graphite and copper in the brush. Particular attention was given to the correlation between electrical signal fluctuation and tribological properties in an electrical sliding contact system. A ring-on-block type tribotester was used for this experiment and the ring was made from pure copper. Results showed that a copper-graphite brush at a particular composition range exhibited the most stable frictional behavior with a minimum voltage drop. The amount of voltage drop at the friction interface was affected by the surface roughness, transfer film formation at the friction interface, and the real area of contact. Microscopic observations and the surface analysis showed a good agreement with the results from this experiment. The results also indicated that the electrical signal flunctuation was directly associated with the oscillation of the coefficient of friction during sliding by nanoscale variation of contacts at the friction interface.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.515-518
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• 2006

This paper presents the friction and wear characteristics of contact type sealing unit for a water turbine of a small hydro-power generation, which Is to stop a leakage of a circulating water from a outside of an impeller to an inside of a rolling bearing. The surface wear strongly affect to the seal life of a mechanical face seal. In this study, the hardness of a stainless steel in which is a heat-treated is 892.8 in Vickers hardness and the hardness of silicone carbide of SiC is 714.1 in Vickers hardness. The surface hardness of a heat-treated stainless steel is 25% high compared with that of a ceramic material of SiC. The contact modes of rubbing surfaces aye a dry friction a water film friction and a mixed friction that is contaminated by a dust, silt and moistures, etc. These two factors of a contact rubbing modes and a material property are very important parameters on the tribological performance such as a friction and wear between a seal ring and a seal seat. The experimental result shows that the surface hardness of a seal material is very important on the friction coefficient and a wear volume. Thus, the results recommend higher hardness of a seal material, which may reduce a friction loss and increase a wear life of primary seal components

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.2
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• pp.110-116
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• 2011

The current study investigated the friction property of angle and width effect for micro-scale grooved crosshatch pattern on SKD11 steel surface against bearing steel using pin-on-disk type. The samples fabricated by photolithography process and then these are carry out the electrochemical etching process. We discuss the friction property due to the influence of a hatched-angle and a width of groove on contact surface. We could be explained the lubrication mechanism for a Stribeck curve. So It was found that the friction coefficient depend on an angle of the crosshatch on contact surface. It was thus verified that micro-scale crosshatch grooved pattern could affect the friction reduction. Also, it is play an important a width of groove to be improved the friction property. I was found that friction property has a relationship between a width and an angle for micro-grooved pattern.

• Structural Engineering and Mechanics
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• v.23 no.4
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• pp.431-447
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• 2006

A new incremental finite element model is developed to simulate the frictional contact of elastic bodies. The incremental convex programming method is exploited, in the framework of finite element approach, to recast the variational inequality principle of contact problem in a discretized form. The non-classical friction model of Oden and Pires is adopted, however, the friction effect is represented by an equivalent non-linear stiffness rather than additional constraints. Different parametric studies are worked out to address the versatility of the proposed model.

• Journal of Adhesion and Interface
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• v.5 no.2
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• pp.31-42
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• 2004

Many animals possess on their legs adhesive pads, which have undergone evolutionary optimization to be able to attach to variable substrates and to control adhesive forces during locomotion. Insect adhesive pads are either relatively smooth or densely covered with specialized adhesive hairs. Theoretical models predict that adhesion can be increased by splitting the contact zone into many microscopic, elastic subunits, which provides a functional explanation for the widespread 'hairy' design. In many hairy and all smooth attachment systems, the adhesive contact is mediated by a thin film of liquid secretion between the cuticle and the substrate. By using interference reflection microscopy (IRM), the thickness and viscosity of the secretion film was estimated in Weaver ants (Oecophylla smaragdina). 'Footprint' droplets deposited on glass are hydrophobic and form low contact angles. IRM of insect pads in contact showed that the adhesive liquid is an emulsion consisting of hydrophilic, volatile droplets dispersed in a persistent, hydrophobic phase. I tested predictions derived from film thickness and viscosity by measuring friction forces of Weaver ants on a smooth substrate. The measured friction forces were much greater than expected assuming a homogenous film between the pad and the surface. The findings indicate that the rubbery pad cuticle directly interacts with the substrate. To achieve intimate contact between the cuticle and the surface, secretion must drain away, which may be facilitated by microfolds on the surface of smooth insect pads. I propose a combined wet adhesion/rubber friction model of insect surface attachment that explains both the presence of a significant static friction component and the velocity-dependence of sliding friction.

• Transactions of the Society of Information Storage Systems
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• v.11 no.1
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• pp.11-15
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• 2015

In HDD industry, many technologies have been developed and investigated as means to increase the areal density of drives. Thermal flying-height control has been considered and widely applied in current HDD. When contact occur between TFC slider and disk, the slider has a friction heating induced by highly rotated disk. Moreover, because of the friction heating, additional protrusion of slider can occur. The additional protrusion in contact situation can be a severe effect on head part of slider and disk. Therefore, in this paper, we analyze the friction heating and additional protrusion in contact situation.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.439-443
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• 2004

In this research, we describe the sorting conditions modeling by friction force. As in any mechanism which is required to provide good dynamic performance and high accuracy, performance evaluation of optimal control. To understand friction it is necessary to investigate the topography of the sliding surfaces in contact. Any surfaces, even apparently smooth surfaces, are microscopically rough. When two surfaces come into contact, the true contact takes place only at point where asperities come together. The sorting conditions of sorting mechanism with friction force is sorting force must be equal with force can sorting one highest veneer among loaded veneer. This is just a thing being sorted veneer have friction with under veneer and this friction disturb sorting at the same time. Hence, the sorting conditions evaluation is important to sorting one veneer must get under control friction with veneer.

• Tribology and Lubricants
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• v.17 no.6
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• pp.459-466
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• 2001

In this study, the effects of oxide layer formed on the contact parts of TiN coated ball and steel disk on friction characteristics in various sliding conditions were investigated. AISI52100 steel ball was used for the substrate of coated ball specimens, which were prepared by depositing TiN coating with 1(m in coating thickness. AISI1045 steel was used for the disk type counter-body. To investigate the effect of oxide layer on the contact parts of two materials, the tests were performed both in air for forming oxide layer on the contact parts and in nitrogen environment to avoid oxidation. From the test results, the frictional characteristic between the two materials was predominated by iron oxide layer that formed on wear tract of counter-body and this layer caused friction transition and high friction. And the adhesive wear occurred from steel disk to TiN coated ball caused the formation of oxide layer on counter parts between the two materials.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.133-134
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• 2002

The use of low friction wear resistant coatings for machine components is rapidly increasing. These components may operate in any lubrication regime, and less frequently even unlubricated. When run unlubricated it is easy to see the beneficial effect of a low friction coating. However, it has frequently been shown that the coating may also be very beneficial under boundary and mixed lubrication conditions. The present digest briefly presents a few interesting aspects of the use of low friction coatings in lubricated contact illustrated by selected experimental results.