• Title/Summary/Keyword: Sliding velocity

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Wear Characteristics of Particulate Reinforced Metal Matrix Composites Fabricated by a Pressureless Metal Infiltration Process (무가압함침법으로 제조된 입자강화 금속복합재료의 마모특성)

  • 김재동;정순억;김형진
    • Journal of Ocean Engineering and Technology
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    • v.17 no.1
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    • pp.55-60
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    • 2003
  • The effect of size and volume fraction of ceramic particles, with sliding velocity on the wear properties were investigated for the metal matrix composites fabricated by the pressureless infiltration process. The metal matrix composites exhibited about 5.5 - 6 times the wear resistance compared with AC8A alloy at high sliding velocity, and by increasing the particle size and decreasing the volume fraction, the wear resistance was improved. The wear resistance of metal matrix composites and AC8A alloy exhibited different aspects. Wear loss of AC8A alloy increased with sliding velocity, linearly : whereas, metal matrix composites indicated more wear loss than AC8A alloy at the slow velocity region. However, a transition point of wear loss was found at the middle velocity region, which shows the minimum wear loss. Further, wear loss at the high velocity region exhibited nearly the same value as the slow velocity region. In terms of wear mechanism, the metal matrix composites generally exhibited abrasive wear at slow to high sliding velocity; however, AC8A alloy showed abrasive wear at low sliding velocity and adhesive and melt wear at high sliding velocity.

Wear Characteristics of Particulate Reinforced Metal Matrix Composites Fabricated by Pressureless Metal Infiltration Process (무가압함침법으로 제조된 입자강화 금속복합재료의 마모특성)

  • Kim, Jae-Dong;Jung, Sun-Uk;Kim, Hyung-Jin
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • pp.379-384
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    • 2002
  • The effect of size and volume fraction of ceramic particles with sliding velocity on the wear properties were investigated for the metal matrix composites fabricated by pressureless infiltration process. The particulate metal matrix composites exhibited about 5.5 - 6 times of excellent wear resistance compared with AC8A alloy at high sliding velocity, and as increasing the particle size and decreasing the volume fraction the wear resistance was improved. The wear resistance of metal matrix composites and AC8A alloy exhibited different aspects. Wear loss of AC8A alloy increased with sliding velocity linearly. whereas metal matrix composites indicated more wear loss than AC8A alloy at slow velocity region, however a transition point of wear loss was found at middle velocity region which show the minimum wear loss, and wear loss at high velocity region exhibited nearly same value with slow velocity region. In terms of wear mechanism, the metal matrix composites exhibited the abrasive wear at slow to high sliding velocity generally, however AC8A alloy showed abrasive wear at low sliding velocity and adhesive and melt wear at high sliding velocity.

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A Study on the surface hardening by repeated sliding contact (반복 미끄럼 접촉에 의한 표면층의 경화에 대한 연구)

  • 박준목;김석삼
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.80-88
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    • 1997
  • Repeated sliding contact wear test was performed with copper specimens to obtain the relationship between wear and surface hardening. Wear surface and wear track section were observed by optical microscopy. Wear volume and micro-vikers hardness of sublayer below wear surface were obtained. These results suggested that wear mechanism depended on contact load than sliding velocity. Therefore wear mechanism was abrasive wear within critical contact load and adhesive wear over critical contact load. Wear rate increased with contact load, sliding distance but decreased with sliding velocity. Surface hardening increased with sliding velocity and sliding distance but decreased with contact load.

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Effect of Volume fraction of SiC Particle Reinforcement on the Wear Properties of 6061AI Composites (6061AI 복합재료 마모특성에 미치는 SiC입자 강화재 체적분율의 영향)

  • Kim, Heon-Joo
    • Journal of the Korean Society for Heat Treatment
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    • v.15 no.2
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    • pp.82-92
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    • 2002
  • In the present investigation wear behavior of the 6061AI composites reinforced with 5, 10, 20% SiC particles for dry sliding against a SM45C counterface was studied as a function of load and sliding velocity. Sliding wear tests were conducted at two loads(19.6 and 49N) and three sliding velocities(0.2, 1 and 2 m/sec) at constant sliding distance of 4000 m using pin-on-disk machine under room temperature. Presence of SiC reinforcement particles in the composites has displayed a transition from mild to severe wear at relatively higher applied load and sliding velocity compare to that of the matrix metal. As the volume fraction of SiC particles increased, the transition moved to a more severe wear conditions. Eventually, mild wear prevailed at a most severe wear conditions in this study, that was 49N load and 2 m/sec sliding velocity in 20% SiC particle/6061AI composite.

A Study on Wear Properties of Plasma Sprayed $Cr_3C_2$-NiCr Coating at High Temperature (크롬탄화물 용사피막의 고온마모 특성연구)

  • 김의현;권숙인
    • 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.

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Wear Properties of Epoxy Matrix Nanocomposites (에폭시 기지 나노복합재료의 마모 특성)

  • Kim, J.D.;Kim, H.J.;Koh, S.W.;Kim, Y.S.
    • Journal of Power System Engineering
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    • v.14 no.6
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    • pp.83-88
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    • 2010
  • The wear behavior of epoxy matrix composites filled with nano sized silica particles is discussed in this paper. Especially, the variation of the coefficient of friction and the wear resistance according to the change of apply load and sliding velocity were investigated for these materials. Wear tests of pin-on-disc mode were carried out and the wear test results exhibited as following ; The epoxy matrix composites showed lower coefficient of friction compared to the neat epoxy through the whole sliding distance. As increasing the sliding velocity the epoxy matrix composites indicated lower coefficient of friction, whereas the neat epoxy showed higher coefficient of friction as increasing the sliding velocity. The specific friction work of both materials were increased with apply load. In case of the epoxy matrix composites, the running in periods of friction were reduced as increase in apply load. The epoxy matrix composites were improved the wear resistance by adding the nano silica particles remarkably. It is expected that the load carrying capacity of the epoxy matrix composites will be improved by increase of Pv factor.

Seismic Performance Evaluation of Seismically Isolated Nuclear Power Plants Considering Various Velocity-Dependent Friction Coefficient of Friction Pendulum System (마찰진자시스템의 마찰계수 변화에 따른 면진된 원전구조물의 거동특성 비교)

  • Seok, Cheol-Geun;Song, Jong-Keol
    • Journal of the Earthquake Engineering Society of Korea
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    • v.20 no.2
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    • pp.125-134
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    • 2016
  • In order to improve seismic safety of nuclear power plant (NPP) structures in high seismicity area, seismic isolation system can be adapted. In this study, friction pendulum system (FPS) is used as the seismic isolation system. According to Coulomb's friction theory, friction coefficient is constant regardless of bearing pressure and sliding velocity. However, friction coefficient under actual situation can be changed according to bearing pressure, sliding velocity and temperature. Seismic responses of friction pendulum system with constant friction and various velocity-dependent friction are compared. The velocity-dependent friction coefficients of FPS are varied between low-and fast-velocity friction coefficients according to sliding velocity. From the results of seismic analysis of FPS with various cases of friction coefficient, it can be observed that the yield force of FPS becomes larger as the fast-velocity friction coefficient becomes larger. Also, the displacement response of FPS becomes smaller as the fast-velocity coefficient becomes larger.

Properties of the Gold and Palladium-Nickel Alloy Plated Layers on Electrical Contact Materials (접점상에 입힌 Au 및 Pd-Ni 합금도금층의 특성)

  • 백철승;장현구;김회정
    • Journal of the Korean institute of surface engineering
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    • v.25 no.3
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    • pp.107-116
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    • 1992
  • The optimum thickness of Pd-Ni plated layers used as an electrical contact film was investigated by evaluating mechanical, thermal and environmental characteristics. The variations of morphologies and chemical compositions were studied by using SEM, EDS and ESCA. As a result of wear test, the wear resistance behavior of the gold plated layers was not changed with the sliding velocity changes. The palladium-nickel plated layer showed better wear resistance than the gold plated layer at low sliding velocity, but it showed poor wear resistance at high sliding velocity. Under the thermal condition of $400^{\circ}C$ in air, the gold thickness of $2\mu\textrm{m}$ without underplate on phosphorous bronze formed copper oxide on the surface layer by rapid diffusion of copper whereas the gold thickness of $0.8\mu\textrm{m}$ deposited on nickel and palladium-nickel underplate was stable at $400^{\circ}C$. Under the sulfur dioxide environments, the gold thickness of $0.3\mu\textrm{m}$ deposited on the nickel thickness of$ 3\mu\textrm{m}$ and the palladium-nickel thickness of $2\mu\textrm{m}$ underplate was more corrosion-resistant than the gold thickness of $2\mu\textrm{m}$ without underplate on phosphorous bronze. Under the nitric acid vapor environment, corrosion resistance of the gold film was superior to an equivalent thickness of the palladium-nickel film.

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A Study on Scoring Resistance In Lubricated Sliding Contact (윤활 마찰면의 스코링 저항성에 관한 연구)

  • 김해원;홍재학;허준영
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.2
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    • pp.358-366
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    • 1990
  • As a basic study to clarify the scoring resistance in lubricated sliding contact, the temperature rise on frictional surface was analyzed by theoretical method and the effects of various factors on the temperature rise were examined. On the basic of the results obtained theoretically, the practical equations to calculate the maximum average temperature of the contact surface were proposed which are applicable to sliding contact. Then, the effects of sliding velocity and oil temperature on the seizure behavior, and the relation between seizure and temperature rise were investigated. The following conclusions are deduced : The maximum average temperature rise and the other bulk temperature. The former is affected by the size of heat supply region and the sliding velocity, the latter is affected by heat transfer coefficient. Without regard to the operating condition such as sliding velocity, oil temperature and operating time at each load-step, the maximum average temperature just before seizure is nearly constant except in the region of lower velocity. Consequently, the maximum average temperature of the contact surface in boundary lubrication is a useful criterion to predict the scoring of sliding contact.

A Tribological Study of SiC-Steel Couples (탄화규소-강 미끄럼에서의 마모특성)

  • 장복기;김윤주
    • Journal of the Korean Ceramic Society
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    • v.34 no.1
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    • pp.7-12
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    • 1997
  • The wear behavior of SiC in SiC-steel sliding couple was investigated under various wear test conditions, such as solid state sliding - dry and wet air atmosphere - or lubricated sliding, sliding velocity and at-mosphere temperature. The effect of SiC fabrication process on the SiC wear rate was also studied under varying sliding velocities. Humidity of air plays a lubricating role in the solid state sliding, while the wear behavior is largely influenced by the sliding velocity, especially if the atmosphere is extremely dry. The fa-brication process of SiC and the surface roughness result in different wear rate depending on the magnitude of sliding velocity. High temperature is, among others, the most deteriorating factor of wear, thus being strongly wear-accelerating even under boundary lubrication.

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