• Title/Summary/Keyword: Sliding friction

Search Result 836, Processing Time 0.025 seconds

Load and Stiffness Dependence of Atomistic Sliding Friction (원자스케일 마찰의 하중 및 강성 의존성)

  • Sung, In-Ha
    • Tribology and Lubricants
    • /
    • v.23 no.1
    • /
    • pp.9-13
    • /
    • 2007
  • Despite numerous researches on atomic-scale friction have been carried out for understanding the origin of friction, lots of questions about sliding friction still remain. It is known that friction at atomic-scale always shows unique phenomena called 'stick-slips' which reflect atomic lattice of a scanned surface. In this work, experimental study on the effects of system stiffnesses and load on the atomic-scale stick-slip friction of graphite was performed by using an Atomic Force Microscope and various cantilevers/tips. The objective of this research is to figure out the dependency of atomic-scale friction on the nanomechanical properties in sliding contact such as load, stiffness and contact materials systematically. From this work, the experimental observation of transitions in atomic-scale friction from smooth sliding to multiple stick-slips in air was first made, according to the lateral cantilever stiffness and applied normal load. The superlubricity of graphite could be verified from friction vs. load experiments. Based on the results, the relationship between the stickslip behaviors and contact stiffness was carefully discussed in this work. The results or this work indicate that the atomic-scale stick-slip behaviors can be controlled by adjusting the system stiffnesses and contact materials.

Position Control of Ball-Screw Systems with Compensation of Estimated Coulomb Friction (추정된 쿨롱 마찰을 보상한 볼-스크류 시스템의 위치제어)

  • Kim, Han-Me;Choi, Jeong-Ju;Lee, Young-Jin;Kim, Jong-Shik
    • Proceedings of the KSME Conference
    • /
    • 2003.04a
    • /
    • pp.893-898
    • /
    • 2003
  • Coulomb friction is an important factor for precise position tracking control systems. The control systems with friction causes the steady state error because of being sensitive to the change of system condition and highly nonlinear characteristics. To overcome these problems, we use an estimation scheme of Coulomb friction to experiment for it's compensating. The estimated factor for Coulomb friction is used as a feed-forward compensator to improve the tracking performance of ball-screw systems. The tracking performance was improved by compensating the estimated friction torque in the feed-forward term. And, the sliding mode control which is derived from the Lyapunov stability theorem is applied for robust stability and reducing chattering. The experimental results show that the sliding mode controller with adaptive friction compensator has a good tracking performance compared with the friction uncompensated controller.

  • PDF

Study on Tribology Characteristics of Friction Material Based on Tribo-Systems

  • Yang, Zhao-Jian;Fang Ren;Kim, Seock-Sam
    • KSTLE International Journal
    • /
    • v.4 no.1
    • /
    • pp.27-30
    • /
    • 2003
  • The basic principles of tribo-systems and study method based on tribe-systems are introduced in the paper, Based on the viewpoint of tribe-systems, the experiment on tribology characteristics of friction lining material in multi-rope friction hoist is carried out. The research result shows: tribology characteristics of friction material are not its inherent characteristic but system characteristics of the tribo-systems, the“sliding-rope”of multi-rope friction hoist can be divided into“safety sliding-rope”and“fault sliding-rope”, study on friction material only based on characteristic of system where friction material exists possesses practical significance.

Friction and Wear Behavior of Carbon/carbon Composite Materials and its Application to a Neural Network (탄소/탄소 복합재료의 마찰 및 마모 거동과 신경회로망에의 적용에 관한 연구)

  • 류병진;윤재륜;권익환
    • Tribology and Lubricants
    • /
    • v.10 no.4
    • /
    • pp.13-26
    • /
    • 1994
  • Effects of resin contents, number of carbonization, graphitization, sliding speed, and oxidation on friction and wear behavior of carbon/carbon composite materials were investigated. Friction and wear tests were carried out under various sliding conditions. An experimental setup was designed and built in the laboratory. Stainless steel disks were used as the counterface material. Friction coefficient, emperature, and wear factor were measured with a data acquisition system. Wear surfaces were observed by the scanning electron microscope. It has been shown that the average friction coefficient was increased with the sliding speed in the range of 1.43~6.10 m/s, but it as decreased in the range of 6.10~17.35 m/s. Specimens prepared by different numbers of carbonization. showed variations in friction coefficient and friction coefficient of the graphitized specimen was the highest. Friction coefficients depended on contribution of the plowing and adhesive components. As the number of carbonization was increased, wear factor was reduced. Wear factor of the graphitized specimens dropped further. In the case of graphitized specimens, sliding speed had a large influence on wear behavior. When the tribological experiments were conducted in nitrogen atmosphere, the wear factor was decreased to two thirds of the wear factor obtained in air. It is obvious that the difference was affected by oxidation. Results of friction and wear tests were applied to a neural network system based on the backpropagation algorithm. A neural network may be a valuable tool for prediction of tribological behavior of the carbon/carbon composite material if ample data are present.

The Analysis for Surface Hardening by Repeated Sliding Contact (반복 미끄럼 접촉에 의한 표면층의 경화에 대한 해석)

  • 박준목;김석삼
    • Tribology and Lubricants
    • /
    • v.13 no.4
    • /
    • pp.71-78
    • /
    • 1997
  • Wear is affected by numerous factors-contact load, sliding velocity and distance, friction coefficient, material properties and environmental conditions. Among these wear factors, surface hardness is one of very important factors to determine wear. But surface hardness is varied by work hardening during repeated sliding contact. In this reason wear rate is increased or decreased with varying surface hardness, and transition of wear mechanism is happened. In this study, the surface hardening by accumulating residual stress was analyzed by considering the repeated sliding Hertzian contact model. The results showed that surface hardness was increased with increasing contact load, friction coefficient and contact number. And the depth of hardening layer, plastic layer and elastic layer depended upon contact load and number, but they didn't depend upon friction coefficient. The predicted surface hardness was about 1.5-1.8 times as hard as the material.

Fabrication of Embedded Thermocouple Sensor and Experimental Study on Measurement of Interface Temperature for Dry Friction (임베디드 서모커플 센서 제조 및 미끄럼 마찰 계면온도 측정에 관한 실험적 연구)

  • Jang, Beomtaek;Lim, Youngheon;Kim, Seocksam
    • Tribology and Lubricants
    • /
    • v.29 no.6
    • /
    • pp.372-377
    • /
    • 2013
  • This study investigated the interface temperatures for the sliding friction of three types of pins fabricated with thermocouple wires by the suction casting method. Optical microscopy was used to examine the surrounding material state at the bonding interface with the thermocouple wires. Friction tests were performed under dry sliding conditions against stainless steel 304 at nominal stresses of 1.42-4.25 MPa and sliding speeds of 0.5-1.25 m/s. Tribological data were collected using a custom-made pin-on-disk apparatus that measured the interface temperature and corresponding friction coefficient. Static tests were performed to demonstrate the functionality and reliability of the thermocouple wires-combined temperature sensor (TCTS). Each TCTS showed good linearity and sensitivity and very similar response times for the thermocouple and critical temperature during sliding friction.

Friction Behavior of DLC Coating Slid Against AZ31 Magnesium Alloy at Various Temperatures (마그네슘 합금에 대한 DLC 코팅의 온도에 따른 마찰기구 해석)

  • Gwon, H.;Kim, M. G.;Hur, H. L.;Kim, Y.-S.
    • Transactions of Materials Processing
    • /
    • v.24 no.6
    • /
    • pp.405-410
    • /
    • 2015
  • Sheet-forming of Mg alloys is conducted at elevated temperatures (250℃) due to the low formability at room temperature. The high-temperature process often gives rise to surface damage on the alloy (i.e. galling.) In the current study, the frictional characteristics of DLC coating slid against an AZ31 Mg alloy at various temperatures were investigated. The coating has been used widely for low-friction processes. Dry-sliding friction and galling characteristics of an AZ31 Mg alloy (disk), which slid against uncoated and a DLC-coated STD-61 steel (pin), were investigated using a reciprocating-sliding tribometer at room temperature and 250℃. To represent the real sliding phenomena during a sheet metal forming process, single-stroke tests were used (10mm stroke length) rather than a reciprocating long sliding-distance test. The DLC coating suppressed adhesion between the alloy and the tool steel at room temperature, and exhibited a low friction coefficient. However, during sliding at 250℃, severe adhesion occurred between the two surfaces, which resulted in a high friction coefficient and galling.

EFFECT OF SURFACE ROUGHNESS OF MATING SURFACE AND TRANSFER LAYER ON FRICTION BETWEEN a-CNx AND $Si_3N_4$ IN NITROGEN

  • Umehara, N.;Tokoroyama, T.;Tomita, H.;Takenoshita, Y.
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
    • /
    • 2002.10b
    • /
    • pp.155-156
    • /
    • 2002
  • During the sliding between a-CNx and $Si_3N_4$, applying nitrogen as environmental gas provided very low friction as the level of 0.01 in friction coefficient. In order to know the effect of the running-in process on the reduction of the friction, the effect of surface roughness of mating surface on friction was investigated. It was shown that smooth surface in wear scar of ball provided low friction coefficient. Friction coefficient after running-in was proportional to the Ry value of wear scar of ball. Also smooth thin transferred layer was observed on the wear scar of balls with an AFM after sliding test. Those results showed the smoothing of wear scar of ball, the generating of the transferred layer from CNx was necessary for low friction.

  • PDF

A study on abrasive wear characteristics of side plate of FRP ship (FRP 선박 외판재의 연삭마모 특성에 관한 연구)

  • Kim, Byung-Tak;Koh, Sung-Wi
    • Journal of the Korean Society of Fisheries and Ocean Technology
    • /
    • v.44 no.3
    • /
    • pp.250-256
    • /
    • 2008
  • Generally the side plate materials of FRP ship are composed of glass fiber and unsaturated polyester resin composites(GFRP composites). In this study, the effect of applied load and sliding speed on friction and wear characteristics of these materials were investigated at ambient temperature by pin-on-disc friction test. The cumulative wear volume, friction coefficient and wear rate of these materials for SiC abrasive paper were determined experimentally. The cumulative wear volume showed a tendency to increase nonlinearly with increase of sliding distance and was dependent on applied load and sliding speed for these composites. The friction coefficient of GFRP composites was increased as applied load increased at same sliding speed in wear test. It was verified by SEM photograph of worn surface that major failure mechanisms were microfracture, deformation of resin, cutting and cracking.

A Study on the Friction and Wear Characteristics of $Al_2O_3-TiC$ ($Al_2O_3-TiC$의 마찰 및 마모특성에 관한 연구)

  • 조구환;이기현;김경웅
    • Tribology and Lubricants
    • /
    • v.8 no.2
    • /
    • pp.20-25
    • /
    • 1992
  • Friction and wear behavior of hot isostatic pressed $Al_2O_3-TiC$ was experimentally examined. Pin-on-disk type friction and wear apparatus was designed and manufactured for the experiment. The experiments were conducted under unlubricated sliding motion in both low and high humidity for three kinds of sliding speed. $Al_2O_3-TiC$ and bearing steel were used as counterface materials. Friction coefficient, wear rate, and surface roughness were measured. Wear surface and wear debris were observed through optical microscope and SEM and analyzed by EDAX. The results showed that the counterface materials, the sliding speed, and the moisture at the sliding surface have significant influence on the friction coefficient and wear rate of $Al_2O_3-TiC$.