• 소성∙가공
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• 제8권6호
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• pp.583-590
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• 1999

New forward slip model has been developed for the precise prediction of rolling speed in the hot strip finishing mill. Besides those influential factors such as neutral point, work roll diameter, friction coefficient, bite angle and the thickness at each side of entry and delivery of the rolls, roll torque was specifically taken into account in this study. To consider the effect of width change on forward slip, calibration factors obtained from rolling torque has been added to new prediction model and refining method has also been developed to reduce the speed unbalance between adjacent stands. The application of the new model showed a good agreement in rolling speeds between the predictions and the actual measurements, and the standard deviation of prediction error has also been significantly reduced.

• 한국정밀공학회지
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• 제13권8호
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• pp.139-145
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• 1996

Tapping is one of the most widely used machining operations. There are several methodes of producing external screw threads, e.g. turning, milling with single or multiple cutter, rolling, and grinding, but the methods available for cutting enternal threads are less numerous, and for threads in small holes, tapping is employed almost exclusively. In this study, the tap with the various geometry has been developed in order to tap special workmaterial at considerably higher cutting speed than that of the conventional HSS tap. The experimental tests are run with various cutting speed by using a piezo type tool dynamometer to measure tapping torque. Tapping torque is affected by the design of the tap, which seems to be due to internal friction and shearing of the metal. It is clarified that the process of chip formation strongly depends on rake angle, relief angle, angle of twist.

• The Korean Journal of Ceramics
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• 제2권4호
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• pp.226-230
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• 1996

A small amount of fine particle graphite was added to $\alpha$-SiC and $\beta$-SiC having certain particle distributions, and they were mixed clay and frit. After forming, they were sintered at 140$0^{\circ}C$ for 3 hours. Tribological properties of sintered $\alpha$-SiC-$\beta$-SiC-graphite-clay (frit) system showed that kinetic friction coefficient was 0.108, specific wear rate was 1.3${\times}10^-8\;mm^2$.$kgf^1$, and torque was 0.01kgf.cm at the wrench torque of 100 kgf.cm.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.90.6-90
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• 2002

An active stick which has the variable force-feel characteristics is developed. A combined position and force control strategy is mechanized using a 2-axis built-in force sensor and LVDT. The 2-axis force sensor which measures the stick force felt by the operator is developed by using strain gages and appropriate instrumental amplifiers. A mathematical model of the active stick dynamics is derived, and compared with the experimental results. The frictional torque of the stick due to the mechanical contacts of several parts makes the experimental frequency responses to be dependent on the magnitude of excitation signal, and the precision closed loop control to be difficult. A friction observe...

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 전력전자학술대회 논문집
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• pp.123-128
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• 1998

This paper describes the evaluation of a force-reflecting interface with ultrasonic motors(USMs). The force-reflecting interface allows a human to feel object within virtual environment. To effectively display the mechanical impedance of the human hand we need a haptic device with specific characteristics, such as low inertia, almost zero friction and very high stiffness. USMs have attracted considerable attention as the actuator satisfied these conditions. USMs combine features such as high driving torque at low rotational speed, high holding torque and fast response therefore we studied two degree of freedom force-reflecting haptic system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1989년도 한국자동제어학술회의논문집; Seoul, Korea; 27-28 Oct. 1989
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• pp.776-780
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• 1989

A constant torque dynamometer with associated instrumentation and control functions for the development of friction materials for automotive-type disc brakes, has been developed. Full scale disc pads are subject to a series of intermittent brake applications at a constant rotational speed of the brake disc and constant braking power. This paper gives a description of the dynamometer and an example of results obtained.

• 소음진동
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• 제9권5호
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• pp.936-942
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• 1999

Unstable torsional vibration on the marine ship's propulsion shafting system with diesel engine occurred due to a slippage of multi-friction clutch which was installed between increasing gear and shaft generator. In this paper, the mechanism of this vibration was verified via torsional, whirling, axial and structural vibration measurements of shafting system and noise measurement of gear box. And it was also identified by the theoretical analysis method.

• 제어로봇시스템학회논문지
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• 제7권1호
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• pp.1155-1161
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• 2001

We propose an adaptive nonlinear control algorithm for high precision tracking and stabilization of LOS(Line-of-Sight). The friction parameters of the LOS gimbal are estimated by off-line evolutionary strategy and the friction is compensated by estimated friction compensator. Especially, as the nonlinear control input in a small tracking error zone is enlarged by the nonlinear function, the steady state error is significantly reduced. The proposed algorithm is a direct adaptive control method based on the Lyapunov stability theory, and its convergence is guaranteed under the limited modeling error or torque disturbance. The performance of the pro-posed algorithm is verified by computer simulation on the LOS gimbal model of a moving vehicle.

• Tribology and Lubricants
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• 제23권3호
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• pp.95-102
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• 2007

In recently designed diesel engines, the running conditions for piston pin bearings have become very severe due to combustion pressure and temperature increase. Moreover, the lead removal from the bush material has strongly reduced the capability of the anti friction material to accept asperity contacts. In this paper, before trying to find the pressure distributions on the oil film of piston pin bearings by the unsteady two dimensional thermohydrodynamic lubrication analysis in order to do the optimum design of the bearings of piston pin, it will be investigated the tendancy of piston pin rotating motion by calculating the friction coefficient at piston pin bearings, the oil film thickness and the frictional torques induced by hydrodynamic shear stress.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제27회 춘계학술대회
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• pp.307-313
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• 1998

This paper presents the experimental results of the friction characteristics of double lip-type oil seals which show an improvement in sealing performance over single lip-type oil seals. The major differences between two oil seals are the number of contact lip and seal materials; Nitrile Butadine Rubber(NBR) and urethane rubber. The measured results show that the friction torque of double lip seals shows 12-17% increases compared with those of single lip-type seals. But the sealing performance and service life of double tip oil seals have been increased and stabilized due to an optimized design of the seal lip and material properties.