• 한국철도학회논문집
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• 제10권4호
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• pp.431-437
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• 2007

This paper describes the dynamic modeling of a railway vehicle when it is under braking force. It is important for the enhancement of braking performance to establish a proper dynamic model of a railway vehicle because the braking performance is affected by some dynamic forces generated by a railway vehicle when it undergoes braking. In this paper, a dynamic model for one vehicle is suggested to compute the dynamic behavior of a railway vehicle in the HILS(Hardware In-the-loop Simulation) system for the railway vehicle braking devices. To simplify the dynamic model, friction between a wheel and a rail is assumed that there exist only the static and the dynamic friction forces. Static friction coefficient is also assumed to be a function of the running speed. Some simulations are carried out with various braking forces, and the braking characteristics according to the change of the braking force are discussed. This study can provide some fundamental results to construct the HILS system for braking devices of a railway vehicle.

• Structural Engineering and Mechanics
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• 제23권5호
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• pp.505-523
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• 2006

An unrestrained plane rigid body resting on a horizontal surface which shakes horizontally and vertically may assume one of the five modes of response: rest, slide, slide-rock, rock, and free flight. The first four are nontrivial modes of motion. It is important to study which one of these responses is started from rest as in most studies it is often assumed that the initial mode is the particular mode of response. Criteria governing the initiation of modes are first briefly discussed. It is shown that the commencement of response modes depends on the aspect ratio of the body, coefficients of static and kinetic friction at the body-base interface, and the magnitude of maximum base accelerations. Considering the last two factors as random variables, the initiation of response modes is next studied from a probabilistic point of view. Type 1 extreme value and lognormal distributions are employed for maximum base excitations and coefficient of friction respectively. Analytical expressions for computing the probability values of each mode of response are derived. The effects of slenderness ratio, vertical acceleration, and statistical distributions of maximum acceleration and coefficient of friction are shown through numerical results and plots.

• 한국농공학회지
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• 제33권4호
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• pp.105-120
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• 1991

This study was performed to investigate the minimum safety factor of embankment in consideration of seismic coefficient by the psuedo-static analysis The variables were cohesion, the internal friction angle, angle of slope, height of seepage, height of embankment, depth of replacement The results obtained were compared with those by Fellenius method, simplified Bishop method and Janbu method. The results were summarized as follows: 1.The increasing rate of the minimum safety factor with the increasing of cohesion appeared larger in Fellenius method and Bishop method than in Janbu method. And that with the increasing of the internal friction angle appeared the lowest value in Janbu method. The minimum safety factor was influenced larger on the internal friction angle than on cohesion. 2.The variation of the minimum safety factor with the height of seepage at 0m and 5 m was nearly similar to Fellenius method, Bishop method and Janbu method. On the other hand, it was decreased suddenly at 25 m. 3.The minimum safety factor with the height of embankment was decreased remarkably under 10 m with the increasing of seismic coefficient. But, it was decreased slowly more than 10 m. As the height of embankment was low, the influence of cohesion appeared larger. 4.In heigher case of the depth of replacement, the phenomenon of reduction of the minimum safety factor appeared remarkably with seismic coefficient increased. And in lower case of the depth of replacement, the minimum safety factor was similar in Fellenius method and Bishop mehtod. But it appeared larger in Bishop method and Janbu method than in Fellenius method with the depth of replacement increased. 5.As the cohesion and the internal friction angle were large, the phenomenon of reduction of the minimum safety factor with the increasing of seismic coefficient appeared remarkably. Also, the influence of seismic coefficient in minimum safety factor appeared larger with the soil parameter increased. 6.When the seismic coefficient was considerated, investigation of the structural body on the slope stability appeared profitably in Fellenius method and Janbu method than in Bishop method.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.707-710
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• 2001

Brakes are one of the important safety parts in cars. The requirements of brakes in performance, in comfort, and working lifetime are high. This paper presents the static analysis on the stress and temperature of a automotive drum brake. The particular interest is the distribution of the contact pressure between brake lining and drum. The problems to be solved are the effects of friction coefficient, actuation force, temperature, and brake component's stiffness. The contact problem includes friction, and is solved using the ABAQUS.

• Geomechanics and Engineering
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• 제20권4호
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• pp.287-297
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• 2020

This paper investigates the stability of a three-dimensional (3D) wedge under the pseudo-static action of an earthquake based on the nonlinear Barton-Bandis (B-B) failure criterion. The influences of the mechanical parameters of the discontinuity surface, the geometric parameters of the wedge and the pseudo-static parameters of the earthquake on the stability of the wedge are analyzed, as well as the sensitivity of these parameters. Moreover, a stereographic projection is used to evaluate the influence of pseudo-static direction on instability mode. The parametric analyses show that the stability coefficient and the instability mode of the wedge depend on the mechanical parameter of the rock mass, the geometric form of the wedge and the pseudo-static state of the earthquake. The friction angle of the rock φ_b, the roughness coefficient of the structure surface JRC and the two angles related to strikes of the joints θ₁ and θ₂ are sensitive to stability. Furthermore, the sensitivity of wedge height h, the compressive strength of the rock at the fracture surface JCS and the slope angle α to the stability are insignificant.

• 한국산학기술학회논문지
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• 제10권8호
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• pp.2055-2061
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• 2009

고장력볼트 마찰이음에서 모재 및 덮개판을 과대공 제작하였을 경우 연결부의 내하력에 다소의 변화가 발생 될 수 있다. 본 논문에서는 고장력볼트 마찰이음에서 표준공과 과대공에 따라 미끄럼하중과 미끄럼계수의 변화를 파악하기 위하여 정적인장시험을 실시하였다. 정적인장시험결과 모재 및 덮개판의 과대공 제작에 따라 미끄럼계수의 변화가 다소 발생하였으나 이를 정형화시키기에는 다소 무리가 따랐으며, 미끄럼강도는 표준공 제작시의 값과 과대공제작시의 값이 최대 26%의 차이를 나타내었다. 그러나 이는 설계미끄럼강도를 초과하기 때문에 사용하중하에서 연결부의 사용성에 미치는 영향이 미약하므로 강부재 제작시 부득이하게 발생할 수 있는 과대공에 따른 규정을 보다 유연하게 적용시킨다면 구조물의 설계 및 시공시 효율성과 경제성 증대의 효과가 기대된다고 판단되었다.

• 한국안전학회지
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• 제27권5호
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• pp.185-189
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• 2012

While there is no standards on slip risk for contaminants on surface, glycerol is described in standard contaminant for measuring coefficient of friction(COF) and slip resistance such as ISO 13287. But that is just used to measure the slip resistance of surface materials and shoes not to evaluate the contaminant materials. Therefore the objective of this study was to find out the relationship between standard contaminant and the contaminants used usually at the workplaces. For this, some measurement criteria were acquired from the analysis based on biomechanics and kinetics of human gait during slips. The slip resistance according to viscosity of the contaminants was measured applying the criteria and slip probability was determined by the gait analysis. Some factors which should be considered when measuring the slip resistance were identified. The velocity, acceleration, contact time and contact pressure should be 1 m/sec, 10 $m/sec^2$, 350 kPa and less than 0.5sec respectively. The variation of viscosity according to temperature for working oils was different from that of standard contaminant. The static coefficient of friction (SCOF) of working oils was almost 0.5 times as large as the SCOF of standard contaminant. So it was assumed to be difficult to compare the contaminants at the workplaces with the glycerol as a standard contaminant for estimating the slip risk.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1989년도 제10회 학술강연회초록집
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• pp.94-99
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• 1989

This paper analyzes file stiffness, damping coefficient, friction force and flow coefficient of externally pressurized oil journal beating, including the effect of journal rotation according to the Sommerfeld number. This paper assumed that the oil in the whole pocket has constant pressure, and that the oil in the whole bearing region has constant viscosity, temperature and density. Reynolds equation is derived from Nuvier - Stokes equation and continuity equation. And solved bearing pressure by ADI method for whole bearing region and fitted with out flow rate of pocket region. The model for numerical simulation is hydro - static oil journal bearing for high-speed, high-accuracy lathe spindle.

• Tribology and Lubricants
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• 제23권4호
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• pp.162-169
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• 2007

This paper deals with friction effects on the performance of double-bumped AFBs. The stiffness and damping coefficients of the double bump vary depending on the external load and its friction coefficient. The double bump can be either in the single or double active region depending on vertical deflection. The equivalent stiffness and damping coefficients of the bump system are derived from the vertical and horizontal deflection of the bump, including the friction effect. A static and dynamic performance analysis is carried out by using the finite difference method and the perturbation technique. The results of the performance analysis for a double-bumped AFB are compared with those obtained for a single-bumped AFB. This paper successfully proves that a double bumped AFB has higher load capacity, stiffness, and damping than a single-bumped AFB in a heavily loaded condition.

• Structural Engineering and Mechanics
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• 제4권3호
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• pp.330-344
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• 1996

A model of a cable comprising interacting wires with dry friction forces at the interfaces is subjected to a quasi-static cyclic loading. The first cycle of this process, comprising of axial loading, unloading and reloading is investigated analytically. Explicit load-elongation relationships are obtained for all of the above phases of the cycle. An expression for the hysteretic losses is also obtained in an explicit form. It is shown that losses are proportional to the third power of the amplitude of the oscillating axial force, and are in inverse proportion to the interwire friction forces. The results obtained are used to introduce a model of a cable as a solid rod with an equivalent stiffness and damping properties of the rod material. It is shown that the stiffness of the equivalent rod is weakly nonlinear, whereas the viscous damping coefficient is proportional to the amplitude of the oscillation. Some numerical results illustrating the effect of cable parameters on the losses are given.