• Title, Summary, Keyword: Slip Velocity

Search Result 341, Processing Time 0.097 seconds

Numerical Analysis of the Slip Velocity and Temperature-Jump in Microchannel Using Langmuir Slip Boundary Condition (미소채널내의 Langmuir 미끄럼 경계조건을 통한 미끄럼 속도 및 급격한 온도변화에 관한 수치해석)

  • Kim, Sang-Woo;Kim, Hyun-Goo;Lee, Do-Hyung
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.33 no.3
    • /
    • pp.164-169
    • /
    • 2009
  • The slip velocity and the temperature jumps for low-speed flow in microchannels are investigated using Langmuir slip boundary condition. This slip boundary condition is suggested to simulate micro flow. The current study analyzes Langmuir slip boundary condition theoretically and it analyzed numerically micro-Couette flow, micro-Poiseuille flow and grooved microchannel flow. First, to prove validity for Langmuir slip condition, an analytical solution for micro-Couette flow is derived from Navier-Stokes equations with Langmuir slip conditions and is compared with DSMC and an analytical solution with Maxwell slip boundary condition. Second, the numerical analysis is performed for micro-Poiseuille flow and grooved microchannel flow. The slip velocity and temperature distribution are compared with results of DSMC or Maxwell slip condition and those are shown in good agreement.

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

Anti-Slip Control for Wheeled Robot Based on Disturbance Observer (외란 관측기를 이용한 이동 로봇의 슬립 제어)

  • Kwon, Sun-Ku;Huh, Uk-Youl;Kim, Jin-Whan;Kim, Hak-Il
    • Proceedings of the KIEE Conference
    • /
    • /
    • pp.50-52
    • /
    • 2004
  • Mobility of an indoor wheeled robot is affected by adhesion force that is related to various floor conditions. When the adhesion force between driving wheels and the floor decreases suddenly, the robot has slip state. First of all, this paper models adhesion characteristics and slip in wheeled robot. Secondly, the paper proposes estimation method of adhesion force coefficient according to slip velocity. In oder to overcome this slip problem, optimal slip velocity must be decided for stable movement of wheeled robot. The paper proposes an anti-slip control system based on an ordinary disturbance observer, that is, the anti-slip control is achieved by reducing the driving torque enough to give maximum adhesion force coefficient. These procedure is implemented using a Pioneer 2-DXE parameter.

  • PDF

A Study on the Determination of Slip-up Time for Slip-Form System using Surface Wave Velocity (표면파 속도를 이용한 슬립폼 시스템 상승 시기 결정에 관한 연구)

  • Kim, Heeseok;Kim, Young Jin;Chin, Won Jong;Yoon, Hyejin
    • Journal of The Korean Society of Civil Engineers
    • /
    • v.32 no.5D
    • /
    • pp.483-492
    • /
    • 2012
  • The early setting time of concrete is an important factor determining the slip up velocity of the slip-form system. Accordingly, need is for a technique evaluating the early setting time in order to secure the safety of the slip-form system and the construction quality of concrete. This paper intends to estimate the early setting time by evaluating the setting degree of concrete using surface wave velocity so as to determine the slip up time of the slip-form system. Penetration resistance test and compressive strength test are performed first to clarify the relationship between the early setting time of concrete and the compressive strength. Then, compressive strength test and ultrasonic wave test are conducted to examine the relation between the compressive strength and the surface wave velocity. Continuous wavelet transform is adopted to measure the surface wave velocity. Numerical analysis is carried out to demonstrate the appropriateness of the application of continuous wavelet transform. Based on these results, the propagation velocity of the surface wave required for the slip up of slip-form system is suggested. Finally, a reduced model test of the slip-form system is conducted to verify the feasibility of the proposed surface wave velocity for the determination of th slip up velocity.

Backward Slip as a Measure of Floor Slipperiness (미끄럼 측정치로서의 뒤로미끄러짐)

  • Myung, Rohae
    • Journal of the Ergonomics Society of Korea
    • /
    • v.20 no.2
    • /
    • pp.47-57
    • /
    • 2001
  • To simulate an actual slip to measure floor slipperiness, slip resistance testers simulate slip in only forward direction because forward slip in the landing phase was found to be the most important factor for loss of balance. Backward slip in the take off phase was possible but was excluded in the friction test protocol because it was not dangerous. However, backward slip was tested in the friction test protocol without any theoretical background of the significance in generating dangerous slips and falls and was proven to be as good as forward slip in measuring floor slipperiness. Therefore, this study was designed to investigate the significance of backward slip in generating dangerous slips and falls with different combinations of floor and shoe sole. The results showed different tendency of backward slip in take off phase being significant in generating dangerous slips and falls because backward slip in the takeoff phase affected gait pattern disturbances seriously. resulted in dangerous falls. Fast toe velocity increased the severity of backward slip and confirmed the significance of backward slip in generating dangerous slips and falls. As a result, this study recommends the utilization of backward slip in the measurement of floor slipperiness.

  • PDF

EFFECT OF ASPECT RATIO ON SLIP FLOW IN RECTANGULAR MICROCHANNELS

  • Islam, Md.Tajul;Lee, Yeon-Won
    • Proceedings of the KSME Conference
    • /
    • /
    • pp.2803-2810
    • /
    • 2007
  • Three dimensional numerical studies were carried out to investigate the effect of aspect ratio on gas slip flow in rectangular microchannels. We focused on aspect ratio effect on slip velocity, pressure distribution and mass flow rate. As aspect ratio decreases the wall slip velocity also decreases. As a result nonlinearity of pressure distribution increases. The slip velocities on sides and top/bottom walls are different and this difference decreases with increasing aspect ratio. These two velocities are equal when aspect ratio is 1. The ratios of slip mass flow rate over noslip mass flow rate increases with increasing aspect ratios.

  • PDF

Quadrant Protrusion error Modeling Through the Identification of Friction (마찰력 규명을 통한 상한절환 오차 모델링)

  • 김민석
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
    • /
    • /
    • pp.371-376
    • /
    • 1999
  • Stick-slip friction is present to some degree in almost all actuators and mechanisms and is often responsible for performance limitations. Simulation of stick-slip friction is difficult because of strongly nonlinear behavior in the vicinity of zero velocity. A straightforward method for representing and simulating friction effects is presented. True zero velocity sticking is represented without equation reformulation or the introduction of numerical stiffness problems. Stick-slip motion is investigated experimentally, and the fundamental characteristics of the stick-slip motion are clarified. Based on these experimental results, the characteristics of static in the period of stick and kinetic friction in the period of slip are studied concretely so as to clarify the stick-slip process.

  • PDF

Behavior of Slip Force in Continuous Flate Casting (평판 강혼 주조용 연주기의 Slip Force 거동에 대하여)

  • Si Young Kim
    • Journal of the Korean Society of Fisheries and Ocean Technology
    • /
    • v.17 no.2
    • /
    • pp.85-91
    • /
    • 1981
  • An equation was derived which describes the slip force that occurs at the casting of initial state due to unequilibrium with support bar weight, liquid metal, casting velocity, thickness, control roller, hydraulic motor and etc. The slip force equations are solved on the basis of velocity, gravity and thickness in casting ingot. In this paper the auther assumed that the other mechanisms are normal. The behaviour of slip force in many characteristics is calculated as a function of velocity, gravity and thickness with variation. The conclusion with this phenomena is reached that the present theory realistically predicts the growth of slip force in a flat plate ingot continuous casting machine.

  • PDF

Rotor Resistance Estimation Using Slip Angular Velocity In Vector-Controlled Induction Motor (벡터제어 유도전동기의 슬립 각속도를 이용한 회전자 저항 추정)

  • Park, Hyunsu;Jo, Gwon-Jae;Choi, Jong-Woo
    • The Transactions of The Korean Institute of Electrical Engineers
    • /
    • v.67 no.10
    • /
    • pp.1308-1316
    • /
    • 2018
  • Accurate tuning of parameter is very important in vector-controlled induction motor. Among the parameters of induction motor, detuning of rotor resistance used in controller design deteriorates drive performance. This paper presents a novel rotor resistance estimation strategy using slip angular velocity in vector-controlled induction motor drives. The slip angular velocity can be calculated by two methods. Firstly, it can be induced from the rotor voltage equation. Secondly, it can be induced from the difference between synchronous angular velocity and rotor angular velocity. The first method includes the rotor resistance, while the second method dose not include this parameter. From this fact, the rotor resistance can be identified by comparing the slip angular velocities in the two methods. In the tuned states of the rotor resistance, performances of flux estimator and speed drive are discussed. The simulation and experimental results are given to verify the validity of the proposed method in various situations.

Microflow of dilute colloidal suspension in narrow channel of microfluidic-chip under Newtonian fluid slip condition

  • Chun Myung-Suk;Lee Tae Seok;Lee Kangtaek
    • Korea-Australia Rheology Journal
    • /
    • v.17 no.4
    • /
    • pp.207-215
    • /
    • 2005
  • We present a finite difference solution for electrokinetic flow in rectangular microchannels encompassing Navier's fluid slip phenomena. The externally applied body force originated from between the nonlinear Poisson-Boltzmann field around the channel wall and the flow-induced electric field is employed in the equation of motion. The basic principle of net current conservation is applied in the ion transport. The effects of the slip length and the long-range repulsion upon the velocity profile are examined in conjunction with the friction factor. It is evident that the fluid slip counteracts the effect by the electric double layer and induces a larger flow rate. Particle streak imaging by fluorescent microscope and the data processing method developed ourselves are applied to straight channel designed to allow for flow visualization of dilute latex colloids underlying the condition of simple fluid. The reliability of the velocity profile determined by the flow imaging is justified by comparing with the finite difference solution. We recognized the behavior of fluid slip in velocity profiles at the hydrophobic surface of polydimethylsiloxane wall, from which the slip length was evaluated for different conditions.