• Title/Summary/Keyword: Dry Friction

Search Result 354, Processing Time 0.025 seconds

Robust Nonlinear $H_2$/$H_{\infty}$Control for a Parallel Inverted Pendulum (병렬형 역진자와 비선형 $H_2$/H_{\infty}강인제어)

  • Han, Seong-Ik;Kim, Jong-Sik
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.24 no.4 s.175
    • /
    • pp.1065-1074
    • /
    • 2000
  • A robust nonlinear $H_2$/$H_{\infty}$ control method for a parallel inverted pendulum with structured perturbation and dry friction is proposed. By the random input describing function techniques, the nonlinear dry friction is approximated into the quasi-linear system. Introducing the quadratic robustness theorem, the robust $H_2$/$H_{\infty}$ control system is constructed for the quasi-linear perturbed system. But it is difficult to design a controller due to the nonlinear correction term in Riccati equation. With some transformations on the Riccati equation containing nonlinear correction term, the design of the robust nonlinear controller can be done easily. Hence when the stiffness and mass of the parallel inverted pendulum vary in certain ranges, the proposed control scheme has the robustness for both the structured perturbation and dry friction. The results of computer simulation show the effectiveness of our proposed control method.

Friction and Wear at Dry Sliding Low Carbon Steel Surfaces Under Vacuum Conditions (진공분위기 내에서 건조마찰 미끄럼운동을 하는 저탄소강 표면의 마찰마모 특성)

  • 공호성;윤의성;권오관
    • Tribology and Lubricants
    • /
    • v.10 no.3
    • /
    • pp.29-38
    • /
    • 1994
  • The friction and wear of mild steel at dry sliding surfaces under different vacuum conditions have been investigated to understand the wear mechanisms. For the test, a ball-ondisk typed wear-rig has been built and implemented, allowing control of sliding speed, load and vacuum. Results show that, at a high sliding velocity, friction of low carbon steel (SS41) under a high vacuum is much higher than that of ambient condition and wear is much severer. It is due to lack of effective oxidation film formation on which steel surfaces could protect themselves against the severe wear. It has been shown, however, that there is a critical regime with contact conditions (at a low sliding velocity, a low load, and under a medium vacuum) at which effective, protective films of low carbon steel have been built on the surfaces in a friction process with a self-regulating way, resulting in both very low coefficients of friction (about 0.3) and mild wear. In order to investigate the protective films on steel surfaces, the worn surfaces and the wear debris have been experimentally analyzed with SEM, AES/SAM and XRD. A theoretical analysis of frictional heating at sliding surfaces, and an experimental analysis of the influence of oxidation wear under various vacuum conditions are described. The important variables on which self-formations of protective films at dry sliding surfaces depend, and the wear mechanisms are also investigated.

Wear and Friction Behavior on the Surface of Swash Plate of Compressor for Air Condition System of Automobile (자동차 에어컨용 압축기 사판의 표면 형태에 따른 마찰 마모 거동)

  • Kwon, Yun-Ki;Lee, Geon-Ho;Lee, Ki-Chun
    • Tribology and Lubricants
    • /
    • v.27 no.2
    • /
    • pp.88-94
    • /
    • 2011
  • The tribological characteristics of the swash plate surface of a compressor which is for automobile were investigated. For surface treatments, PTFE and $MoS_2$ are used as a solid lubricant, together with copper alloy. Test condition is set considering actual driving condition. Wear testing is conducted using pin on disk type tester, and the coefficient of friction and the temperature on friction surface are measured. Also, to determine the wear patterns, cross-section of friction surface is analyzed by SEM(scanning electrode microscope). The $MoS_2$, both at dry and lubricated conditions, friction surface and the coefficient of friction maintained rather stable results. But, the PTFE, at oil less condition, sample resulted in rather unstable condition. In case of copper alloy, quite higher friction coefficients(higher than 0.1) were obtained at dry condition. At the temperature of $125^{\circ}C$, seizure has occurred.

Experimental Study on the Friction Characteristics of Pin-Bush Bearing Metals for Diesel Engine (디젤엔진용 핀부시 베어링 소재의 마찰특성에 관한 실험적 연구)

  • Kim, Chung-Kyun;Kim, Kyung-Seob
    • Tribology and Lubricants
    • /
    • v.25 no.6
    • /
    • pp.409-413
    • /
    • 2009
  • This paper presents the hardness and friction characteristics of pb-free pin-bush bearing metal, which is manufactured by a centrifugal casting technology. A bronze metal with a high hardness and low friction properties is usually used for Diesel engine pin-bush bearing and high pressure cylinder. Pb-free metal for pin-bush bearings shows a little high hardness of 120 Hv compared with that of a conventional Pb bearing metal of 100~110 Hv. In general, the friction coefficient of pin-bush bearings is affected by a rotating speed and a load for various rubbing contact modes. But a contact load is more influential parameter when the contact rubbing mode transits from a mixed lubrication to a dry friction contact. The experimental result shows that the friction coefficient is more unstable at the dry contact mode compared with that of other two rubbing modes such as oil film contact and mixed friction conditions.

Effect of Stress History on Friction and Wear of Metals in Dry and Boundary Lubricated Conditions (건조 및 경계윤활 조건에서 응력이력에 따른 금속재료의 마찰 마멸 특성)

  • 황동환;김대은
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
    • /
    • 1996.04a
    • /
    • pp.93-98
    • /
    • 1996
  • Friction and wear characteristics of metals in dry and boundary lubricated sliding conditions are observed experimentally using pin-on-disk and pin-on-plate type tribotesters. The motivation of this research is to investigate the effect of sliding history on the tribological behavior of metals. Cu and SM45C steel materials were used for the experiment. The results show that in dry condition the fictional behavior as well as wear of the specimens differed between uni-directional and bi-directional sliding conditions. The friction coefficient values, wear profile and optical micrograph of the wear track are presented.

  • PDF

FUNDAMENTAL STUDY OF SEMI-DRY FORGING WITH MIST LUBRICATION

  • Matsumoto Ryo;Osakada Kozo
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 2003.10b
    • /
    • pp.31-35
    • /
    • 2003
  • Friction in cold forging with mist lubrication is measured with the ring compression test. Small quantity of mist lubricant is sprayed onto the surfaces of cemented tungsten carbide (WC) tools polished to mirror surfaces, and the specimens of pure aluminum are compressed. It is found that spraying small quantity of lubricant $(0.5\;g/m^2)$ is effective to reduce the friction in comparison with the dry condition. The mist particles stick to the tool surface as separated dots, and the behavior of the trapped mist lubricant between the tool and specimen during upsetting is discussed.

  • PDF

An Analysis of Forced Vibration Response of a Cantilever Beam with a Dry Friction Damper (건마찰 감쇠기가 부착된 외팔보의 강제진동 응답 해석)

  • Go, Young-Jun;Kang, Byoung-Yong;Chang, Ho-Gyeong;Kim, Ye-Hyun
    • The Journal of the Acoustical Society of Korea
    • /
    • v.15 no.2
    • /
    • pp.33-39
    • /
    • 1996
  • A theoretical study of the forced vibration response of a cantilevered beam with non-linear dry friction damping is analyzed by various slip displacements and force levels for the position coordinates of spring-mass-damper and external exciting force. A component mode analysis is carried out based on the constraint conditions and Lagrange multipliers to treat physical systems with non-linear damping. The analysis has shown that the basic phenomena observed for a simply supported beam with a dry friction damper attached are also observed for cantilevered beam.

  • PDF

Mathematical Friction Model for Sheet Metal Forming Analysis (박판성형 해석용 수학적 마찰 모델)

  • Keum Y. T.;Song M. J.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 2004.05a
    • /
    • pp.182-185
    • /
    • 2004
  • Based on the experimental observation, the mathematical friction model, which is an essential information for analyzing the forming process of sheet metal, is developed considering lubricant viscosity, surface roughness and hardness, punch corner radius, and punch speed. By comparing the punch load found by FEM with a proposed friction model with experimental measurement when the coated and uncoated steel sheets are formed in 2-D geometry in dry and lubricant conditions, the validity and accuracy of the developed friction model are demonstrated.

  • PDF

Friction Model for Sheet Metal Forming Analysis(Part 2 :Mathematical Model) (박판성형 해석용 마찰 모델(2부:수학적 모델))

  • 금영탁;이봉현
    • Transactions of Materials Processing
    • /
    • v.13 no.5
    • /
    • pp.461-465
    • /
    • 2004
  • Based on the experimental observation, the mathematical friction model, which is an essential information for analyzing the forming process of sheet metal, is developed considering lubricant viscosity, surface roughness and hardness, punch comer radius, and punch speed. By comparing the punch load found by FEM with a proposed friction model with experimental measurement when the coated and uncoated steel sheets are formed in 2-D geometry in dry and lubricant conditions, the validity and accuracy of the developed friction model are demonstrated.

Wear and friction characteristics of a carbon fiber composite against specular counterpart (탄소 섬유 복합재의 경면 상대재에 대한 마찰 및 마모 특성)

  • YANG BYEONG-CHUN;KOH SUNG-WI
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
    • /
    • 2004.05a
    • /
    • pp.390-394
    • /
    • 2004
  • This is the study on dry sliding wear behavior of unidirectional carbon fiber reinforced epoxy matrix composite at ambient temperature. The wear rates and friction coefficients against the stainless steel counterpart specularly processed were experimentally determined and the resulting wear mechanisms were microscopically observed. Three principal sliding directions relative to the dominant fiber orientation in the composite were selected. Wren sliding took place against smooth and hard counterpart, the highest wear resistance and the lowest friction coefficient were observed in the antiparallel direction. When the velocity between the composite and the counterpart went up, the wear rate increased. The fiber destruction and cracking caused fiber bending on the contact surface, which was discovered to be dominant wear mechanism.

  • PDF