• 한국전산구조공학회논문집
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• 제34권4호
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• pp.213-219
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• 2021

구조물을 지진 위험으로부터 완화시키기 위한 마찰면진장치의 상용화된 마찰재료 중 폴리테트라플루오로에틸렌(polytetrafluoroethylene, PTFE)은 내화학성과 마찰성능이 우수하다. 그러나 PTFE는 상대적으로 낮은 내마모성을 가지므로 경제적인 마찰재료이며 산화마그네슘(oxide magnesium, MgO)으로 내마모성을 증가시킨 개선된 폴리비닐리덴 플루오라이드(polyvinylidene fluoride, PVDF)를 PTFE의 대안으로 제안하였다. 개발된 PVDF/MgO 마찰재를 이용하여 실험을 통해 마찰성능을 측정하였으며 PTFE의 마찰성능과 비교하였다. 그리고 측정된 마찰계수를 이용하여 마찰면진장치를 설계하였다. 마찰면진장치의 성능은 교량의 비선형 시간이력 해석을 통해 확인하였고, 이를 통해 마찰면진장치의 마찰재료로 PTFE를 대체하여 PVDF/MgO를 사용하는 것에 대한 타당성을 평가하였다.

• 한국수소및신에너지학회논문집
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• 제26권6호
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• pp.659-665
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• 2015

In this study, an experimental investigation is performed for evaluation of a liquid pool spreading model with continuous release. The model considered in this study was developed based on a concept which means that the liquid pool spreading is governed by a balance between an inertia force from gravity and a frictional force from friction with the ground under the whole base of the liquid pool. For evaluation of the model, experimental study is performed. Experimental apparatus is setup for measuring release rate, spreading velocity, and evaporation rate from a liquid pool. The experimental results are compared with results from the model. By applying release and evaporation rates obtained from experiments to solving the model, liquid pool radius variation according to time can be obtained. For evaluation of an effect of friction force in the spreading model, results obtained from the models with and without the friction force are compared with those obtained from the experiments. As a result, it is shown that there exists a large deviation between the results obtained from the model without the friction force and the experimental results. On the other hand, the tendency of liquid pool radius variation according to time is similar between the results obtained from the model without the friction force and the experimental results.

• 소성∙가공
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• 제21권1호
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• pp.13-18
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• 2012

During warm forging, materials are formed in the temperature range of $300^{\circ}C\sim900^{\circ}C$. In this temperature range, the friction between the forging die and the material is very high and has a negative effect on the forming process causing severe die wear and possible defects in the component because of stick-slip. Thus, lubrication characteristics are a very important factor for productivity during warm forging. In this paper, ring compression experiments were conducted to estimate the friction factor between the die and the materials as the main factor in characterizing the lubricant. Also, ring tests using normal graphite power as a lubricant coating system were compared with tests using nano graphite powder. The results confirm that the nano graphite is superior to the normal graphite in view of its lubricating effect. In addition, the friction factor (m) was estimated with respect to the amount of the nano graphite content in the lubricant. With 10 % nano graphite the friction factor had the lowest value as compared to other amounts. It can be concluded that the amount of the nano graphite in the coating system can be optimized to obtain the best lubrication condition between the die and the material using ring test experiments.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.492-495
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• 1997

Integral type system is that a system is represented by a proper rational function. In this paper, novel control scheme based on model reference approach is proposed for integral type system. The proposed scheme compensates various undesirable effects of the system. In especially, the proposed scheme applied to DC servo control system, analyzed its control characteristic. Performances of the proposed system show excellent control characteristics; complete compensation of the undesirable nonlinear friction and load viscous, For proving realistic validities, LOS(Line Of Sight) stabilization system which has typically many nonlinear effects is experimented. After executing the computer simulation in "MATLAB", then the results are compared with the experiments. The results are very similar in theoretical study and the proposed control scheme is successfully verified. verified.

• 한국정밀공학회지
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• 제18권6호
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• pp.148-158
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• 2001

In this paper, Automatic Dynamic Balancer(ADB) was simulated and investigated to use at the high speed rotating chuck for the friction welding. In the limited computer simulations and experiments that have been presently carried out, several conclusions have been found. Above critical speed of the rotating system, ADB can balance the rotating disk. Therefore, it can be predicted that ADB can make an uniform flash during the friction welding.

• Tribology and Lubricants
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• 제26권4호
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• pp.224-229
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• 2010

A new test rig is presented to measure friction losses at journal bearings in a reciprocating compressor. This rig consists of a test bearing, torque sensor, driving motor and loading parts especially for vertical shaft. Friction losses are obtained by measuring torque between motor and test bearing. The experiments are carried out at several rotational speeds and temperatures. The test results are presented and discussed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.807-810
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• 1995

The effects of weae particles on the friiction and wear behavior of metals in dry sliding conditions are presented. The tribological test were performed using pure metal specimens which were selected based on their degrees of compatibility and hardness ratio. Friction and wear experiments were conducted using both pin-on-disk and reciprocating pin-on-plate type tribotesters to investigate the effect of motion history. Experimental results show that in the case of dry sliding the frictional behavior observed during pin-on-disk test differed form that of pin-on-reciprocator test for the given set of material pairs. The friction coefficient and wear rate were found to be higher for the pin-on-disk tests. It is suspected that the sliding motion of the pin affects the wear particle dynamics, which in turn influences the frictional behavior. The effect of material pair properties seemed to be relatively smaller than that of wear particles. The results of this paper is expected to aid in the design of mechanical systems for best tribological performance.

• 전기학회논문지
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• 제56권4호
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• pp.777-783
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• 2007

In this paper, we present a novel control approach for linear motor-based transfer systems in which friction reduction and enhancement of control performance are considered. In general, in such systems friction effects from rails and wheels, and internal bearings complicate control scheme since in particularly its dynamics are arbitrarily changed due to mass variation, detent force of motor systems, and gaps among stators. Our control approach is achieved to reduce this undesired friction dynamics using fuzzy system. We construct hybrid control approach for this control system which Is composed of a nominal control and a vertical control against friction. Fuzzy parameter vector is optimally determined from iterative simulation experiments. We demonstrate its superiority via numerical simulations comparing with a traditional control method.

• 한국자동차공학회논문집
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• 제2권2호
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• pp.1-11
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• 1994

The most commonplace of collisions that directly affect people is that of vehicles. Safety studies have noted a correlation between vehicle occupant injury severity and velocity changes. Methods for estimating collision velocity changes are discussed here. This topic is part of what is referred to as accident reconstruction. Only planar collisions are considered. When a vehicle collides with another, impact dynamics with friction should be considered. This paper presents a general analysis methodology of impact. must dynamics incorporating friction. The presence of friction between sliding contacts during the impact makes the problem difficult since the events such as reverse sliding or sticking, which may occur at different times throughout the impact, must be determined. This paper uses the results of RICSAC experiments for verifying the developed methodology. The analysis and experimental results agree well.

• 한국정밀공학회지
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• 제19권10호
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• pp.163-170
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• 2002

The dynamic model of a high-speed vacuum circuit breaker mechanism with spring-actuated cam and linkage is derived to simulate the high-speed closing and opening operations. Its validation for an analysis of high-speed motion behavior is checked through experiments. The characteristics of the friction on the camshaft are investigated using the nonlinear pendulum experiment. The parameters of the friction model are estimated using the optimization technique. The analysis exhibits that the friction of the pendulum depends on stick-slip, Stribeck effect and viscous damping. Comparing simulation results with actual responses using a high-speed camera, the appropriateness of derived dynamic models for the rapid closing and opening operations is shown. The spring motion, which has much influence on the closing responses, is observed.