• Journal of Power System Engineering
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• v.9 no.2
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• pp.57-64
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• 2005

This paper is the study on dry sliding wear behavior of carbon fiber reinforced epoxy matrix composites against lay-up orientation. Tests were investigated on the effect of the lay-up orientation, fiber sliding direction, load and sliding velocity when circumstance keep continuously at $21^{\circ}C$, 60%RH. Pin-on-disk dry sliding wear tests for each experimental condition were carried out with a carbon fiber reinforced plastic pin on stainless steel disk in order to search the friction and wear characteristics. The wear rates and friction coefficients against the stainless steel counterpart were experimentally determined and the wear mechanisms were microscopically observed. The effect on friction and wear behavior are observed differently, according to various conditions. When sliding took place against counterpart, the highest wear resistance and the lowest friction coefficient were observed in the $[0]_{24s}$ lay-up orientation at anti-parallel direction.

• Tribology and Lubricants
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• v.38 no.4
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• pp.162-169
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• 2022

Cobalt-chromium (CoCr)-based alloys have been used for wear applications because of their excellent mechanical properties and wear resistance. With growing concern over environmental problems, CoCr alloys are expected to be used for various tribological applications in degraded lubrication states. To expand the applicability of the materials, data should be accumulated across a broad spectrum of experimental parameters. In this work, the friction and wear characteristics of cobalt-chromium-tungsten (CoCrW) and cobalt-chromium-molybdenum (CoCrMo) alloys are investigated experimentally. The tests are conducted using a pin-on-reciprocating-plate tribotester in dry lubrication. CoCrW and CoCrMo are used as pin and plate materials to investigate the effect of the counter material. The results show that the friction coefficients between CoCrW and CoCrMo generally range from 0.4 to 0.5. The friction coefficient between the CoCrW pin and plate is found to be slightly small. However, the total wear between the CoCrW pin and plate is found to be the largest. In contrast, the total wear between the CoCrW pin and plate is relatively small. Furthermore, CoCrW may cause a faster wear progression of CoCrMo, especially for the case in which CoCrMo is used as the pin material. The results of this work provide a better understanding of the tribological properties of CoCrW and CoCrMo alloys. In addition, this work provides a practical guideline for the use of CoCrW and CoCrMo from the tribological design viewpoint.

• Tribology and Lubricants
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• v.24 no.4
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• pp.196-204
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• 2008

In this study, the pressure distributions on the oil film of piston pin bearings are found by two-dimensional lubrication analysis in order to help the optimum design of the bearings of piston pin. The lubrication analysis is carried out together with an equation related with the oil pressure-viscosity index. The oil film pressure distribution is used as an input data for pressure boundary conditions at the piston pin-boss surface. Finally, the piston pin-boss stress distribution coupled with the thermal stress is calculated, and then compared with the results of the stress analysis which is not counted with the oil film pressure boundary condition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.7
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• pp.681-686
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• 2015

The onset characteristics of friction-induced noise for a steel plate and 4 metallic pins (Cu, Ni, Al, Mg) were studied through the pin-on-disk machine and the reciprocating testing machine. The results showed that the negative slope of the friction curve was related to the onset time of friction noise. Particularly, Cu was found to be the best metallic material for preventing squeak noise in terms of the onset time and the negative friction slope.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.3
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• pp.259-267
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• 1997

Average heat transfer coefficients and friction coefficients have been measured from staggered short pin-fin arrays to investigate the effect of fin shapes. Flow entering into the test section is a fully developed duct flow and the Reynolds number ranges from 5,000 to 25,000 based on fin diameter and average approaching velocity. The fin has three different shapes; uniform-diameter circular fin, two stepped-diameter circular fins. Average heat transfer rates change slightly with the fin shapes. However, friction loss(pressure loss) for the stepped-diameter fins is significantly less than that for the uniform-diameter fin. This results indicate that the stepped-diameter fin arrays in duct flow enhance heat transfer rates largely based on unit pumping power.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.5 s.98
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• pp.194-199
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• 1999

For the purpose of improving accuracy in friction and wear test, a hydraulic pin-on-disk type tribotester was developed and its performance was evaluated experimentally. The performance estimation of the tribotesrer was accomplished by comparing both the consistency of the applied normal load and the robustness of the control against the mechanical disturbances with those of the pneumatic and the dead weight loading method respectively. The developed hydraulic pin-on-disk type tribotester showed the better reliability in the performance and the hydraulic loading method provided the more accurate friction coefficient.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.458-461
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• 2009

Thermo-mechanical simulation of the Friction Stir Spot Welding (FSSW) processes was performed for the AA5083-H18 sheets, utilizing commercial Finite Element Method (FEM) and Finite Volume Method (FVM) which are based on Lagrangian and Eulerian formulations, respectively. The Lagrangian explicit dynamic FEM code, PAM-CRASH, and the Eulerian Computational Fluid Dynamics (CFD) FVM code, STAR-CD, were utilized to understand the effect of pin geometry on weld strength and material flow under the unsteady state condition. Using FVM code, material flow pattern near the tool boundary was analyzed to explain the weld strength difference between the weld by cylindrical pin and the weld by triangular pin, while the frictional energy concept using the FEM code had limitation to explain the weld strength difference.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.5
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• pp.449-455
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• 2016

This study provides the finite-element (FE) squeal-model predicting friction-induced noise with respect to several friction materials that have different friction characteristics. The friction curve and the corresponding friction noise were measured for four friction materials (Cu, Ni, Al, Mg) using the pin-on-disk and reciprocating friction system. The slope of the friction curve linearized at the sliding velocity was applied to the FE model. The unstable modes in the complex eigenvalue analysis were shown to correspond to the squeal frequencies that existed in the experiment.

• Tribology and Lubricants
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• v.15 no.2
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• pp.171-177
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• 1999

Many lubricated systems experience boundary lubrication condition during operation. However, the friction and wear characteristics of boundary lubrication are not clearly understood. In this work the factors which affect the friction and wear between boundary lubricated metallic surfaces are investigated. Experiments were performed using a pin-on-disk type tester with pure aluminum, pure copper, and SM45C steel as the disk material and steel, stainless steel and bearing ball as the ball. The experimental conditions were determined according to the Taguchi experimental method. From the experimental results, the major factors that influence the friction and wear characteristics of boundary lubrication could be identified.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.294-297
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• 2009

The frictional behaviors of Cermets/Cr-Ceramics and Cu-Al coatings of piston ring were investigated. Friction tests were carried out by pin-on-disk test and materials properties of coating layer were analyzed by nano indentation tester. Higher friction coefficient was obtained at harder coating with rougher surface. In case of hard-coating, the scratch depth, width and pile-up height had close relationship with indentation hardness. So the scratch width, depth and pile-up height increases with decreasing friction coefficient. But in case of soft-coating, the friction coefficients are strongly dependent on the morphological characteristics after nano scratching more than indentation hardness.