• 제목/요약/키워드: Sliding Coefficient

Search Result 436, Processing Time 0.022 seconds

Development of a Wheel Slip Control System for Vehicle Cornering Stability (차량 선회 안정성을 위한 휠 슬립 제어시스템 개발)

  • Hong, Dae-Gun;Huh, Kun-Soo;Hwang, In-Yong;SunWoo, Myoung-Ho
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.14 no.4
    • /
    • pp.174-180
    • /
    • 2006
  • The wheel slip control systems are able to control the braking force more accurately and can be adapted to different vehicles more easily than conventional braking control systems. In order to achieve the superior braking performance through the wheel slip control, real-time information such as the tire braking force at each wheel is required. In addition, the optimal target slip values need to be determined depending on the braking objectives such as minimum braking distance, stability enhancement, etc. In this paper, a wheel slip control system is developed for maintaining the vehicle stability based on the braking monitor, wheel slip controller and optimal target slip assignment algorithm. The braking monitor estimates the tire braking force, lateral tire force and brake disk-pad friction coefficient utilizing the extended Kalman filter. The wheel slip controller is designed based on the sliding mode control method. The target slip assignment algorithm is proposed to maintain the vehicle stability based on the direct yaw moment controller and fuzzy logic. The performance of the proposed wheel slip control system is verified in simulations and demonstrates the effectiveness of the wheel slip control in various road conditions.

Friction Behavior of Oil-enriched Nanoporous Anodic Aluminum Oxide Film (오일 함침된 나노 기공 산화알루미늄 필름의 마찰 거동)

  • Kim, Hyo-Sang;Kim, Dae-Hyun;Hahn, Jun-Hee;Ahn, Hyo-Sok
    • Tribology and Lubricants
    • /
    • v.27 no.4
    • /
    • pp.193-197
    • /
    • 2011
  • Friction behavior of nanoporous anodic aluminum oxide(AAO) film was investigated. A 60 ${\mu}m$ thick AAO film having nanopores of 45 nm diameter with 105 nm interpore-diatance was fabricated by mild anodization process. The AAO film was then saturated with paraffinic oil. Reciprocating ball-on-flat sliding friction tests using 1 mm diameter steel ball as the counterpart were carried out with normal load ranging from 0.1 N to 1 N in an ambient environment. The morphology of worn surfaces were analyzed using scanning electron microscopy. The friction coefficient significantly increased with the increase of load. The boundary lubrication layer of paraffinic oil contributed to the lower friction at relatively low load (0.1 N), but it is less effective at high load (1 N). Plastic deformed layer patches were formed on the worn surface of oil-enriched AAO at relatively low load (0.1 N) without evidence of tribochemical reaction. On the other hand, thick tribolayers were formed on the worn surface of both oil-enriched and as-prepared AAO at relatively high load (1 N) due to tribochemical reaction and material transfer.

Deformation Behaviors around Tunnel in Anisotropic Rocks Considering Joint Orientation and Rock Pressure Condition Using Scaled Model Tests (이방성 암반의 방향성과 측압조건을 고려한 터널 모형실험 연구)

  • Jung, Hyung-Rae;Kim, Jong-Woo
    • Tunnel and Underground Space
    • /
    • v.16 no.4 s.63
    • /
    • pp.313-325
    • /
    • 2006
  • In this study, scaled model tests were performed to investigate the deformation behaviors around tunnels located in anisotropic rocks. Fifteen types of test models which had respectively different joint angles and rock pressure conditions were made, where the modelling materials were the mixture of sand, plaster and water. All of the tested models showed the shear failure mechanism at the stress-concentrated regions and sliding phenomena according to the joint planes. The direction of joint inclination turned out to have great effect on the tunnel deformation behaviors. The models of joint inclination less than $30^{\circ}$ showed considerable floor heavings. The model of $50^{\circ}$ joint inclination showed the least tunnel convergence among the tested models regardless of rock pressure condition, so that it was thought as the most stable model. Furthermore, the failure mechanisms and deformation behaviors of tunnel models were strongly dependent on the coefficient of rock pressure.

Improvement of Tribological Characteristics of Multi-Scale Laser-Textured Surface in terms of Lubrication Regime (윤활영역에서 멀티크기 Laser Surface Texturing 효과)

  • Kim, Jong-Hyoung;Choi, Si Geun;Segu, Dawit Zenebe;Jung, Yong-Sub;Kim, Seock-Sam
    • Tribology and Lubricants
    • /
    • v.30 no.1
    • /
    • pp.59-63
    • /
    • 2014
  • Laser Surface Texturing(LST) is a surface engineering process used to improve tribological characteristics of materials by creating patterned microstructures on the mechanical contact surface. In LST technology, a pulsated laser beam is used to create arranged dimples on a surface by a material ablation process, which can improve such as load capacity, wear resistances, lubrication lifetime, and reduce friction coefficients. In the present study, the effect of multi-scale LST on lubricant regime was investigated. A pulsed Nd:YAG laser was applied on the bearing steel(AISI 52100) to create arranged dimples. To optimize the surface texturing effect on friction, multi-scale texture dimples with some specific formula arrays were fabricated by combining circles, ellipses and the laser ablation process. The tribological testing of multi-scale textured surface was performed by a flat-on-flat unidirectional tribometer under lubrication and the results compared with that of the non-textured surface. Through an increase in sliding speed, the beneficial effect of multi-scale LST performance was achieved. The multi-scale textured surface had lower friction coefficient performances than the non-textured surface due to the hydrodynamic lubrication effect.

Study of Inhibition Characteristics of Slurry Additives in Copper CMP using Force Spectroscopy

  • Lee, Hyo-Sang;Philipossian Ara;Babu Suryadevara V.;Patri Udaya B.;Hong, Young-Ki;Economikos Laertis;Goldstein Michael
    • Transactions on Electrical and Electronic Materials
    • /
    • v.8 no.1
    • /
    • pp.5-10
    • /
    • 2007
  • Using a reference slurry, ammonium dodecyl sulfate (ADS), an anionic and environmentally friendly surfactant, was investigated as an alternative to BTA for its inhibition and lubrication characteristics. Results demonstrated that the inhibition efficiency of ADS was superior to that of BTA. Coefficient of friction (COF) was the lowest when the slurry contained ADS. This suggested that adsorbed ADS on the surface provided lubricating action thereby reducing the wear between the contacting surfaces. Temperature results were consistent with the COF and removal rate data. ADS showed the lowest temperature rise again confirming the softening effect of the adsorbed surfactant layer and less energy dissipation due to friction. Spectral analysis of shear force showed that increasing the pad-wafer sliding velocity at constant wafer pressure shifted the high frequency spectral peaks to lower frequencies while increasing the variance of the frictional force. Addition of ADS reduced the fluctuating component of the shear force and the extent of the pre-existing stick-slip phenomena caused by the kinematics of the process and collision event between pad asperities with the wafer. By contrast, in the case of BTA, there were no such observed benefits but instead undesirable effects were seen at some polishing conditions. This work underscored the importance of real-time force spectroscopy in elucidating the adsorption, lubrication and inhibition of additives in slurries in CMP.

Observation of Tribologically Transformed Structures and fretting Wear Characteristics of Nuclear Fuel Cladding (핵연료 봉의 마찰변태구조 관찰과 프레팅 마멸 특성)

  • Kim, Kyeong-Ho;Lee, Min-Ku;Rhee, Chang-Kyu;Wey, Myeong-Yong;Kim, Whung-Whoe
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.26 no.12
    • /
    • pp.2581-2589
    • /
    • 2002
  • In this research, fretting tests were conducted in air to investigate the wear characteristics of fuel cladding materials with the fretting parameters such as normal load, slip amplitude, frequency and the number of cycles. A high frequency fretting wear tester was designed for this experiment by KAERI. After the experiments, the wear volume and the shape of wear contour were measured by the surface roughness tester. Tribologically transformed structures(TTS) were analysed by means of optical and scanning electron microscopes to identify the main wear mechanisms. The results of this study showed that the wear volume were increased with increasing slip amplitude, and the shape of wear contour was transformed V-type to W-type. Also, it was found that the critical slip amplitude was 168${\mu}{\textrm}{m}$. These phenomena mean that wear mechanism transformed partial slip to gross slip to accelerate wear volume. The wear depth increased with an increase of friction coefficient due to increase of normal load and frequency. The fretting wear mechanisms were believed that, after adhesion and surface plastic deformation occurred by relative sliding motion on the contact between two specimens, TTS creation was induced by surface strain hardening and wear debris were detached from the contact surface which were produced by the micro crack propagation and creation.

Friction and Wear Characteristics of Plasma Coated Surface of Casting Aluminum Alloy (플라즈마 코팅한 주조용 알루미늄합금의 마찰 및 마멸특성)

  • Chae, Young-Hun;Ren, Jing-Ri;Park, Jun-Mock;Kim, Seock-Sam
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.21 no.5
    • /
    • pp.791-799
    • /
    • 1997
  • The wear characteristics and wear mechanisms of plasma sprayed Al/sub 2/ O/sub 3/-40%TiO/sub 2/ and Cr/sub 2/O/sub 3/ deposited on casting aluminum alloy(AC4C) were investigated. Specimens were processed for various coating thicknesses. Ball on disk type wear tester was used for wear test. The scratch test on plasma sprayed coating surface showed that critical load to break the coating layer was greater than 40 N. The critical load increase with the increase of coating thickness of specimens. The friction coefficient of Cr/sub 2/O/sub 3/ coating layer was less than that of Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer. The wear resistance of Cr/sub 2/O/sub 3/ coating layer was greater than that of Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer. Microscopic observation of worn surfaces was made by SEM. SEM observation showed that the main mechanism of wear for Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer was abrasive wear under 50 N. For the case of Al/sub 2/O/sub 3/-40%TiO/sub 2/ coating layer, as the surface cracks perpendicular to sliding direction propagated, the wear debris was generated in wear track. However, the main mechanism of wear for Cr/sub 2/O/sub 3/ coating layer was brittle fracture under 150 N.

Tribological Influence of Kinematic Oil Viscosity Impregnated in Nanopores of Anodic Aluminum Oxide Film (함침 오일 점도에 따른 나노동공 구조의 산화알루미늄 박막의 마찰 및 마멸 거동)

  • Kim, Dae-Hyun;Ahn, Hyo-Sok
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.37 no.5
    • /
    • pp.625-630
    • /
    • 2013
  • The friction behavior of a 60-${\mu}m$-thick anodic aluminum oxide (AAO) film having cylindrical nanopores of 45-nm diameter was investigated as a function of impregnated oil viscosity ranging from 3.4 to 392.6 cSt. Reciprocating ball-on-flat sliding friction tests using a 1-mm-diameter steel ball as the counterpart were carried out with normal load ranging from 0.1 to 1 N in an ambient environment. The friction coefficient significantly decreased with an increase in the oil viscosity. The boundary lubrication film remained effectively under all test conditions when high-viscosity oil was impregnated, whereas it was easily destroyed when low-viscosity oil was impregnated. Thin plastic deformed layer patches were formed on the worn surface with high-viscosity oil without evidence of tribochemical reaction and transfer of counterpart material.

Wear Properties of Nuclear Graphite IG-110 at Elevated Temperature (원자력용 흑연 IG-110 에 대한 고온 마모 특성 평가)

  • Wei, Dunkun;Kim, Jaehoon;Kim, Yeonwook
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.38 no.5
    • /
    • pp.469-474
    • /
    • 2014
  • The high temperature gas-cooled reactor (HTR-10) is designed to produce electricity and hydrogen. Graphite is used as reflector, support structures, and a moderator in reactor core; it has good resistance to neutron and is a suitable material at high temperatures. Friction is generated in the graphite structures for the core reflector, support structures, and moderator because of vibration from the HTR-10 fuel cycle flow. In this study, the wear characteristics of the isotropic graphite IG-110 used in HTR-10 were evaluated. The reciprocating wear test was carried out for graphite against graphite. The effects of changes in the contact load and sliding speeds at room temperature and $400^{\circ}C$ on the coefficient of friction and specific wear rate were evaluated. The wear behavior of graphite IG-110 was evaluated based on the wear surfaces.

Thermal, Tribological, and Removal Rate Characteristics of Pad Conditioning in Copper CMP

  • Lee, Hyo-Sang;DeNardis, Darren;Philipossian, Ara;Seike, Yoshiyuki;Takaoka, Mineo;Miyachi, Keiji;Furukawa, Shoichi;Terada, Akio;Zhuang, Yun;Borucki, Len
    • Transactions on Electrical and Electronic Materials
    • /
    • v.8 no.2
    • /
    • pp.67-72
    • /
    • 2007
  • High Pressure Micro Jet (HPMJ) pad conditioning system was investigated as an alternative to diamond disc conditioning in copper CMP. A series of comparative 50-wafer marathon runs were conducted at constant wafer pressure and sliding velocity using Rohm & Haas IC1000 and Asahi-Kasei EMD Corporation (UNIPAD) concentrically grooved pads under ex-situ diamond conditioning or HPMJ conditioning. SEM images indicated that fibrous surface was restored using UNIPAD pads under both diamond and HPMJ conditioning. With IC1000 pads, asperities on the surface were significantly collapsed. This was believed to be due to differences in pad wear rates for the two conditioning methods. COF and removal rate were stable from wafer to wafer using both diamond and HPMJ conditioning when UNIPAD pads were used. Also, HPMJ conditioning showed higher COF and removal rate when compared to diamond conditioning for UNIPAD. On the other hand, COF and removal rates for IC1000 pads decreased significantly under HPMJ conditioning. Regardless of pad conditioning method adopted and the type of pad used, linear correlation was observed between temperature and COF, and removal rate and COF.