• Proceedings of the KSR Conference
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• 1998.11a
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• pp.512-521
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• 1998

The roll characteristic of railway vehicle is an important factor that affects the roll-over of vehicle and lateral ride comfort of passenger. Generally the roll characteristics of railway vehicle is defined by the term of roll-coefficient, s, which represents the ratio of incline or carbody to that of rail-cant. The limit values of roll coefficient recommended in UIC Bre 0.4 for coach without pantograph and 0.15 for vehicle with pantograph. The roll coefficient can be calculated by VAMPIRE that is the well-known commercial software for analysis of dynamic behavior of railway vehicle. The value of roll coefficient is effected by height of gravity center of carbody, stiffness of primary and secondary suspension and etc. The calculated roll-coefficient for electric locomotive and passenger coach is 0.12 and 0.77 respectively, The additional equipment such as anti-roll bar is considered in order to decrease roll-coefficient of passenger coach. In relation to roll characteristics, the analysis for roll-over due to wind is a1so performed. The results show that roll-characteristics affect the roll-over of vehicle.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.4
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• pp.247-253
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• 2005

This study investigated the effects on foot and ankle roll-over characteristics according to different heel heights during walking. Fifteen female volunteers who have neither musculoskeletal nor foot problems were participated in gait analyses, wearing four different pairs of shoes in different heel heights. To obtain roll-over shape of foot/ankle complex, we used trajectories of knee and ankle joints as well as the renter of pressure between initial contact and opposite initial contact. Results revealed that the entire roll-over shape moved distally as the heel height increased but roll-over characteristics showed uniformly with different heel heights. In addition, we found that nondisablea persons automatically adapted to their foot/ankle complex to varying heel heights within 6cm, by moving the origin of roll-over shape distally to maintain roll-over characteristics. However, since the balance of the gait only by the ankle joint could not be achieved beyond the heel height of 6cm, compensations at the knee and the hip joints occurred simultaneously. Roll-over characteristics in human walking would provide simpler and wider understanding of human walking, and furthermore could be applied to the wide understanding of prosthetics and orthotics of the lower extremity as well as orthopaedic shoes.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.308-312
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• 1999

Developed the model equations which calculate roll force, roll power during hot rolling in real time. The variables which mainly effect on the roll force, roll power are shape factor, reduction, roll diameter, roll velocity, strip inlet temperature, carbon content of strip and strip-roll contact friction coefficient. Among these variables roll diameter, roll velocity, inlet temperature, carbon content and friction coefficient can be excluded in interpolated model equation by introducing equation of die force(F'), power(p') of the frictionless uniform plane strain compression which can be calculated without iteration. At the case of coulomb friction coefficient of 0.3, we evaluated coefficient of polynomial equations of {{{{ { F} over {F' } }}}}, {{{{ { Pf} over {Pd }, { Pd} over {P' } }}}} from the result of finite element analysis using interpolation. It was found that the change of values of {{{{ { F} over {F' }, { P} over {P' } }}}} with the friction coefficient tend to straight line which slope depend only on shape factor. With these properties, developed model equations could be extended to other values of coulomb friction coefficient. To verify developed roll force, roll power model equation we compared the results from these model equation with the results from these model equation with the results from finite element analysis in factory process condition.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.6
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• pp.633-641
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• 2015

The ROM (roll over mitigation) system is a next-generation suspension system that can improve vehicle-driving stability and ride comfort. Currently, mass-produced safety systems, such as ESC (electronic stability control) and ECS (electronic control suspension), enable measurements of longitudinal and lateral acceleration as well as yaw rate through inertial sensor clusters, but they lack direct measurements of the roll angle. Therefore, in this paper, a roll angle estimation algorithm from ESC system sensors and tire normal force has been proposed. Furthermore, this study presents a method for roll over mitigation force distribution between the front and rear of a ROM system. Performance and reliability of the roll angle estimation and roll over mitigation force distribution were investigated through simulations. The simulation results showed that the proposed control algorithm and strategy are reliable during vehicle rollovers.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.12
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• pp.29-35
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• 2007

• 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.

• Journal of the Korean Society for Railway
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• v.14 no.3
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• pp.203-210
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• 2011

This study formulates the theoretical wheel-set model to evaluate wheel-climbing derailments of rolling stock due to collision, and verifies this theory with dynamic simulations. The impact forces occurring during collision are transmitted from a car body to axles through suspensions. As a result of combinations of horizontal and vertical forces applied to axles, rolling stock may lead to derailment. The derailment type will depend on the combinations of the horizontal and vertical forces, flange angle and friction coefficient. According to collision conditions, the wheel-lift, wheel-climbing or roll-over derailments can occur between wheel and rail. In this theoretical derailment model of wheelset, the wheel-climbing derailment types are classified into Climb-over, Climb/roll-over, and pure Roll-over according to derailment mechanism between wheel and rail, and we proposed the theoretical conditions to generate each derailment mechanism. The theoretical wheel-set model was verified by dynamic simulations.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.121-124
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• 2001

On-line prediction model which calculate roll force, roll power and forward slip of continuous hot strip rolling was built based on the results of plane strait rigid-viscoplastic finite element process model. Using the integrated FE process model, a series of finite element simulation was conducted over the process variables, and the influence of various process conditions on non-dimensional parameters was inspected. The prediction accuracy of the proposed on-line model under front and back tension is examined through comparison with predictions from a finite element process model over the various process conditions. In addition, we examined the validity of the on-line prediction model through comparison with roll force of experiment in hot rolling.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1868-1873
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• 2011

In this paper, a theoretical formulation of a simplified wheel-set model for collision-induced derailments was evaluated by numerical simulations for the wheel-climb derailment and wheel-lift derailment types. The derailment types were classified into the wheel-climb derailment and the wheel-lift derailment according to the friction force direction of the wheel-flange. The wheel-climb derailment type was classified into Climb-up, Climb/Roll-over, and Roll-over-C, and wheel-lift derailment type was classified into Slip-up, Slip/Roll-over and Roll-over-L. To verify the theoretical equations derived for the wheel-climb derailment and the wheel-lift derailment, dynamic simulations using RecurDyn of Functionbay and Ls-Dyna of LSTC were performed and compared for some examples. The derailment predictions of the suggested theoretical formulation were in good agreement with those of the numerical simulations. The direction of the frictional force between the wheel-flange and the rail can be well predicted using the suggested derailment formulation at a initial derailment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1623-1630
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• 2010

In this study, effective forming methods for reducing the roll-over of a sector tooth, which is a main component of an automotive seat recliner, are proposed. Due to the large amount of roll-over, accurate contact between the inner gear of a sector tooth and the outer gear of a pawl tooth cannot be normally achieved; thus sensitivity and safety for the passengers decrease. To overcome the aforementioned drawback, we investigated the effect of flowcontrol forming methods involving local embossing die, coining punch, and VIC (Variable Inverse Clearance) on the roll-over depth by FE-analysis and an experiment. The results of a fine-blanking experiment for verifying the proposed methods showed that VIC type is decidedly superior from the aspects of reduction of roll-over and tool strength of the sector tooth.