• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.1
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• pp.130-137
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• 2018

In long freight trains, there is a brake time delay in the neighboring freight cars that causes damage and fractures of couplers, especially the knuckle of them. If there is a problem for couplers in the cars, this could cause a derailment and lead to damage of human life and property damage. In this study, maximum forces on the couplers are studied when a long freight car brakes, with brake delay time and coupler gap. We have made a dynamic model of 50 freight cars and couplers, applying contact between couplers and a characteristic curve for expressing force and displacement of buffers with SIMPACK, a multi-body dynamics program. We use EN 14531-2 from the British Standards Institution, a standard of freight car brakes for the verification of the dynamic model. We also use a simplified method to analyze the dynamic model of 50 freight cars. With changing coupler gap and brake delay time, we do comparative analysis with AAR M-201 from the Association of American Railroads, a standard of AAR couplers. From this result, we find that the standard on fatigue limit is satisfied, such that the brake delay time is within 0.06 second if the coupler gap of the AAR coupler is within 20 millimeters.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.316-316
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• 2000

SPM dynamic model was developed by using Bland & Ford formulas considered elastic zone in roll gap, gauge meter equation, tension equation, speed equation and actuator models. And SPM controllers of the field were done model ing. It was shown the efficiency of constant tension, rol1ing force and elongation controllers by the simulation program and it was recommended the proper gain to the controllers of the field.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.3
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• pp.99-106
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• 2001

Model trains should have very similar motion characteristics to real trains in order to provide realistic feeling to their operators. Main purpose of dynamic analysis of model trains is to predict velocities in straight and circular tracks and estimate stopping distance after power shut off. Equations of motion for a model train are derived that relates velocity, traction, rolling resistance, and pulling force. Also, energy equations for calculating stopping distance after power shut off are derived. Experiments with model trains are preformed to measure velocity, rolling resistance, slip, and stopping distance. The results are compared with the prediction based on the equations of motion, and they showed good agreement. It can be concluded that the prediction is more accurate when the slip between wheel and rail is accounted for. The analysis procedures can be applied to determining various design factors in model trains.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.142-146
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• 2001

In this study, it was investigated the influence of cold rolling factors on the edge drop. Edge drop was highly affected by the shape of work roll, the amount of work roll shift and the crown of hot strip, but the effect of bending force at the front stand was relatively small. The used numerical model was examined by comparing to the result of measured field data, and it showed a qualitative agreement with each other.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.366-372
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• 1999

The deformation behavior of commercial stainless steels under hot rolling conditions was investigated by means of hot compression tests performed in the temperature range 800$^{\circ}C$ to 1200$^{\circ}C$. The measured flow stress-strain curves were analyzed by using a simple flow stress model. It was found that the reference strength of stainless steels are much higher than that of carbon steel and that nitrogen and molybdenum alloying greatly increases flow stress of austenitic stainless steel. Ferritic and duplex stainless steel showed comparatively low flow stresses. The flow stress model, which correlates the flow stress with temperature and strain rate, was applied to predict roll forces during hot-plate rolling of stainless steels.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.306-312
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• 1992

The prevention of roll breakage in hot rolling process is improtant to reduce maintenance cost and production loss. Rolling conditions such as the roll force and torque have been intensively studied to overcome the roll breakage. in the present work, a model for life prediction of work rolls under working condition was developed and discussed. The model consists of stress analysis, crack propagation, wear and fatigue calculation model. Roll life can be predicted by stress, crack depth and fatigue damage calculated from this model. The reliability of stress analysis is backed up by the FEM analysis. From the result of simulation using by pressent model, although the fatigue damage of back up roll reachs 80% of practical limit, that of workroll was less than 40%. In edge section of workroll stress amplification is found by wear and bender effect. We can judge that workroll failures are not due to fatigue damage, crack propagation by bending stress but stress amplification by wear and bender in present working condition.

• Transactions of Materials Processing
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• v.22 no.7
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• pp.371-376
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• 2013

The shape defects such as edge waves and center buckles may be formed in the rolled strip because rolling can easily produce non-homogenous elongation across the strip width. The main purpose of tension leveling is to remove such defects by eliminating the differences in elongation. In this paper, a new approach for the optimization of the process conditions in tension leveling is presented. The approach consists of an analytic model for the prediction of the strip curvature and the force at each roll. The accuracy of the proposed model is examined through comparison with the predictions from a finite element model.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.319-323
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• 1996

A new steel-making process, strip-casting, is introduced. The strip-casting is a new technique making the thin steel strip from the molten steel directly without resorting to repetitive reheating and hot-rolling required in a conventional steel-making method. This paper derives the mathematical model of strip caster, proposes a control strategy for stable startup operation and a fuzzy decision making rule for automatic control mode change in strip-casting process.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.143-148
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• 2004

The numerical analysis of the hard disk drive slider is presented. The pressure distribution was calculated using the finite element method. The generalized Reynolds equation was applied in order to include the gas rarefaction effect. The balance of the air bearing force and preload force was considered. The characteristics of the small vibrations near the equilibrium were studied using the perturbation method. Triangular mesh with variable element size was employed to model the two-rail slider. The flying height, pitching angle, rolling angle, stiffness and damping of the two-rail slider were calculated for radial position changing from the inner radius to the outer radius and for a wide range of the slider crown values. It was found that the flying height, pitching angle and rolling angle were increased with radial position while the stiffness and damping coefficients were decreased. The higher values of crown resulted in increased flying height, pitching angle and damping and decreased stiffness.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.265-268
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• 1999

열간 박판 압연공정에서의 압연하중 압연동력을 실시간으로 계산할 수 있는 모델식을 유한요소 해석결과들을 이용하여 개발하였다 압연하중 압연동력값 결정에 비교적 큰 영향을 주는 인자들로는 형상계수 압하률, 률직경 률속도 스트립 입측온도, 탄소함량, 마찰계수들은 이론적으로 계산이 가능한 무마찰의 균일 평면 변형유 압축공정의 금형하중(F、) 동력 (P、)식을 도입함으로써 내삽모델식에서 제외시킬수 있었다 쿨롱마찰계수($\mu$) 0.3 일 경우의 유한요소해석 결과 데이터들을 내삽법(interpolation)을 통해서 다항식 형태로 {{{{ {F } over {F、 } }}}}, {{{{ { {P }_{f } } over { {P }_{d } } }}}}, {{{{ { {P }_{d } } over { {P }^{、 } } }}}} 식들을 구하였다 마찰계수에 따른{{{{ {F } over {F、 } }}}} {{{{ {P } over { {P }^{、 } } }}}}값의 변화는 형상계수에 따라 기울기가 결정되는 직선 형태로 나타내어짐을 유한요소해석 결과로부터 관찰 할 수 있었다. 이와같이 구한 압연하중 압연동력 모델식의 유효성을 검증하기 위해 무작위로 추출한 실제공정들에서 모델식으로 계산한 압연하중 압연동력 값들을 유한요소해석결과와 서로 비교해 보았다.