• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.5
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• pp.95-100
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• 2013

The important design factors for designing solid lubricating of dynamic seal are tightness, wear resistance and lubricant films. In this study, the effect factors influenced solid lubricating properties of the graphite were analyzed and wear behaviour caused for various test conditions was compared with results obtained from reciprocating wear tests. Also the optimal conditions for formation of lubricant films were investigate to evaluate wear properties of graphite materials. The repeated procedure for the formation of wear particles and lubricant films, and the dissipation of lubricant films was estimated the wear mechanisms with changes of wear depth. Therefore the lubricant film of graphite seal was generated by adhesion of wear particles on the worn surface and it was very useful in wear characteristics.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.11
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• pp.131-137
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• 2009

A pair of connectors for transferring torque is widely used in various types of a mechanical system. By the repetition of mechanical contact between a pair of connector, wear occurs easily. This kind of defect sometimes can cause a serious problem of health in case of the connector is used in a refrigerator. In this work, the material combination of connectors was experimentally studied to reduce the amount of wear; for the combination of connectors, various types of engineering materials including polyacetal, polycabonate, stainless steel (STS-304), NiP coated STS-304, and STS-310 were evaluated to check each wear behavior. Also an effective method of wear test was suggested for precise controlling of wear conditions such as contact area, contact force, and relative motion speed. From the test results, it was found out that a pair of polyacetal to STS-304 and STS-310 showed the lowest specific wear rates among other pairs.

• Composites Research
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• v.15 no.3
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• pp.1-10
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• 2002

The effect of size of SiC particles and additive Mg content on the mechanical properties and wear characteristics were investigated for the SiCp/AC8A composites fabricated by pressureless infiltration process. Results showed that the hardness and the bending strength increased with decreasing the size of SiC particle. By increasing the Mg content the hardness of SiCp/AC8A composites increased due to the hard reaction products, however the bending strength decreased by formation of coarse precipitates and high porosity level. The SiCp/AC8A composites exhibited about 6 times higher wear resistance compared with AC8A alloy at high sliding velocity and as increasing the particle size, wear resistance was improved. The major wear mechanical of SiCp/AC8A composites exhibited the abrasive wear at low to high sliding velocity whereas AC8A alloy showed adhesive and melt wear at high sliding velocity.

• Journal of Welding and Joining
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• v.11 no.4
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• pp.91-102
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• 1993

The plasma sprayed $Cr_3C_2$-NiCr coatings are widely used as wear-resistant and corrosion-resistant materials. The mechanical and wear properties of the plasma sprayed $Cr_3C_2$-NiCr coating on steel plate were examined in this study. The pore in the coatings could be classified into two types, the one is the intrinsic pore originated from the spraying powder, the other is the extrinsic pore formed during spraying. During the tensile adhesion test, the fracture occured at the interface of top coating and bond coating. It is though that the compressive residual stress increases with the increase of the top coating thickness. From the wear test, it was found that the wear rate increased with the increase of the sliding velocity regardless of the temperature. It is thought that the fracture toughness reduces with the increase of the sliding velocity at $30^{\circ}C$ and that the adhesion amount increases with the increase of the sliding velocity at $400^{\circ}C$ It is concluded that the wear mechanism at $30^{\circ}C$ is the fracture and pull-out of the carbide particles due to the fatigue on sliding surface, while the wear mechanism at $400^{\circ}C$ is the adhesion of the smeared layer formed during wear process.

• Journal of the Korean Ceramic Society
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• v.42 no.2 s.273
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• pp.88-93
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• 2005

Ti-AI-Si-N coating layers were deposited on WC-Co substrates by a hybrid system of arc ion plating and sputtering techniques. The coatings were prepared with different Si contents to investigate the effect of Si content on their mechanical properties and microstructures. The dry sliding wear experiments were conducted on Ti-AI-Si-N coated WC-Co discs at constant load, 3N, and sliding speed, 0.1 m/s with two different counterpart materials such as steel ball and zirconia ball using a conventional ball-on-disc sliding wear apparatus. In the case of steel ball, the friction coefficient of Ti-AI-Si-N coating layers became lower than that of Ti-AI­N coating layers. The friction coefficient decreased with increasing of Si content due to adhesive wear behavior between coating layer and steel ball. On the contrary, in the case of zirconia ball, the friction coefficient increased with increasing of Si content, indicating that abrasive wear behavior was more dominant when the coating layers slid against zirconia ball.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.89-94
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• 1993

최근들어 공작기계의 급속한 발전은 절삭작업의 자동화와 무인화를 가능하게 만들었으며 이에따라 절삭가공의 완전한 무인화를 실현하기 이해서는 절삭가공중 발생하는 각종 이상 상태를 in-process로 감시하고 검출하는것이 매우 중요하게 되었다. 이상상태는 절삭공구의 마모나 파손, 채터진동의 발생, 절삭가공에 방해를 주는 절삭칩등을 들수 있으며 이 같은 현상을 검출하기 위한 많은 연구가 활발히 진행되고 있다. 본 연구에서는 내식성,내마모성,내열성 및 기계적 성질이 우수하거나 절삭시 가공 경화성이 크고, 열 전도성이 불량하며, 공구재료와 응착이 쉬어 난색재로 알려지고 톱니형 연속칩이 주로 발생하는 STS304를 선택하여 절삭실험을 하였다. 절삭 조건에 따른 칩 형태를 관찰하여, 절삭조건과 절삭력을 이용하여 칩의 형태를 분류하였으며, 절삭가공중에 칩형태를 검출 할수 있는 가능성에 대하여 연구 하였다.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.1
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• pp.61-68
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• 2010

Purpose: This article attempted to determine the factors affecting the preload and screw loosening. Methods: Available clinical studies from 1981 to 2008 from the PUBMED that presented screw loosening data and review articles regarding screw joint stability were evaluated. Eleven studies dealing the biomechanical principles of the screw mechanics were reviewed. Moreover, the results of our data were included. Results: The frequency of screw loosening was consequently reduced due to the advancement in torque tightening with torque wrench, screw material, coating technique for reducing the frictional force, and thread design, etc. If preload in the screw falls below a critical level, joint stability may be compromised, and the screw joint may fail clinically. The types of fatigue failure of screw were divided to adhesive wear, plastic deformation, and screw fracture. Conclusion: An optimum preload is essential to the success of the implant-abutment complex. To maintain optimum preload, using a torque wrench and re-tightening at recall time were needed.