• Title, Summary, Keyword: Sliding velocity

Search Result 354, Processing Time 0.045 seconds

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
    • /
    • v.17 no.1
    • /
    • pp.55-60
    • /
    • 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
    • /
    • /
    • pp.379-384
    • /
    • 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.

  • PDF

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
    • /
    • /
    • pp.80-88
    • /
    • 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.

  • PDF

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
    • /
    • v.15 no.2
    • /
    • pp.82-92
    • /
    • 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.

Sliding Mode Control with Velocity Feedforward Gain of a Pneumatic Motor (공압모터의 속도 전향이득을 갖는 슬라이딩 모드 제어)

  • Kim, Geun-Mook;Kang, E-Sok
    • Journal of Institute of Control, Robotics and Systems
    • /
    • v.12 no.11
    • /
    • pp.1061-1064
    • /
    • 2006
  • In this study, the performance of the tracking control of a pneumatic servo motor driven position control system using sliding mode is investigated. It is usually quite difficult to obtain precise tracking control of a pneumatic servo motor driven position control system because of the nonlinear deadband and stick-slip friction of the proportional valve. Therefore, a continuous sliding mode controller with velocity feedforward gain is proposed. Experimental results show that the tracking accurracy can be remarkably improved by adding a proper velocity feedforward term to continuous sliding mode controller.

Velocity Control of Permanent Magnet Synchronous Motors Using Nonlinear Sliding Manifold (영구 자석형 동기모터 속도제어를 위한 비선형 슬라이딩 매니폴드 설계)

  • Gil, Jeonghwan;Shin, Donghoon;Lee, Youngwoo;Chung, Chung Choo
    • Journal of Institute of Control, Robotics and Systems
    • /
    • v.21 no.12
    • /
    • pp.1136-1141
    • /
    • 2015
  • In this paper, we develop a sliding mode controller that uses a nonlinear sliding manifold for the permanent magnet synchronous motor. The proposed controller makes sure that both currents and velocity tracking error converge into equilibria. Nonlinear sliding manifold consists of current dynamics and nonlinear functions which are designed with velocity tracking error and its integrated term. The nonlinear functions are designed to guarantee that velocity tracking error converge into zero. The closed-loop stability is proven by Lyapunov theory. The effectiveness of proposed method is demonstrated by numerical simulation results.

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
    • /
    • v.14 no.2
    • /
    • pp.358-366
    • /
    • 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 study on the Stick-slip Characteristic of Machine Tool Feeding System. (공작기계 이송계의 Stick-Slip 특성에 관한 연구)

  • Park, Jong-Gwon;Lee, Hu-Sang
    • 한국기계연구소 소보
    • /
    • /
    • pp.29-35
    • /
    • 1988
  • When low sliding velocities in the boundary lubrication range are operating, irregular movements frequently occur which are a result of the stick-slip phenomenon. Such slide motions are undesirable in precision machine tools, particularly with feed back systems used in numerical and adaptive control machine tools. Accordingly, this paper reports analytical and experimental studies in the stick-slip characteristic of machine tool feeding system. The main conclusions of this study are as follows; The tendency towards stick-slip effects may be reduced by; 1). Reducing the drop in friction coefficient in the Stribeck curve(on the rising part of the friction characteristic at higher sliding speeds, the system is stable all the time) 2). Reducing the transition velocity by the use of a higher viscosity lubricating oil. 3). Increasing the stiffness(Damping)and reducing normal load(Sliding mass) Therefore, the Critical velocity is decided from the above conclusions and in designing of machine tool, feed rates(sliding velocity)must be design the more than critical velocity.

  • PDF

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

  • 장복기;김윤주
    • Journal of the Korean Ceramic Society
    • /
    • v.34 no.1
    • /
    • pp.7-12
    • /
    • 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.

  • PDF

The characteristics and compensation of friction of X-Y table (X-Y 테이블의 마찰력 특성 및 보상)

  • Park, Eun-Chan;Im, Hyuk;Choi, Jong-Ho
    • 제어로봇시스템학회:학술대회논문집
    • /
    • /
    • pp.261-261
    • /
    • 2000
  • This paper analyzes the characteristics of pre-sliding friction of an X-Y table of CNC machining center at velocity reversal, and presents a simple and effective method of friction compensation based on this characteristics. At velocity reversal, a large position tracking error occurs because of the discontinuous change of friction. The relationship between the occurrence time of maximum position tracking error and the acceleration at zero velocity is analyzed by using the spring-like friction model. Furthermore, the experimental observation verifies this relation. From this, the state transition tine from pre-sliding regime into sliding regime can be predicted. Using the predicted transition time, the friction can be effectively compensated and table experimental results show its effectiveness.

  • PDF