• Transactions of Materials Processing
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• v.3 no.2
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• pp.215-228
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• 1994

The purpose of this paper is to pursue a general method to determine both the flow stress of a material and the friction factor by ring compression test. The materials are assumed to obey the expanded n-power hardening rule including the strain-rate effect. Ring compression is simulated by the rigid-plastic finite element method to obtain the database used in determining the flow stress and friction factor. The Simulation is conducted for various strain hardening exponent, strain-rate sensitivity, friction factor, and compressing speed, as variables. It is assumed that the friction factor is constant during the compression process. To evaluate the compatibility of the database, experiments are carried out at room and evaluated temperature using specimens of aluminum 6061-T6 under dry and grease lubrication condition. It is shown that the proposed test method is useful and easy to use in determining the flow stress and the friction factor.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.10a
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• pp.68-72
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• 1992

자동차 및 각종 판재 성형시 성형율을 향상시키는 방법에는 신소재 개발, 금형기술개발, 접촉부의 마찰을 줄여 주기 위한 윤활 등등이 있겠으나 손쉽게 공구다이 상하에 비드를 설치하여 판재를 성형할 경우 미끄럼 저항의 균형을 이루어 주름 억제와 두께분포가 보다 균일해지며 스프링백 현상 등으로 인한 성형 후 치수 불량 등을 주어 판재성형율을 향상시키는데 기여할 수 있다. 본 연구에서는 펀치가 판재를 성형하기 위해 진행됨에 따라 공구다이와 펀치간의 접촉각도가 변하게 되는 점을 고려하여 인출 각도변화에 따른 인출특성 및 마찰계수 변화등을 알아보고자 하며 원형 형태의 환저비드, 단일원형비드, 이중원형 비드의 종류와 크기변화 및 비드좌우 모서리 변화, 공구다이모서리변화, 블랭크가압력 변화, 비드 전진깊이 변화, 비드통 과 후 재료의 기계적 성질 변화등 인출 특성에 영향을 미치는 인자들을 변화시켜나가며 이에 따르는 인출특성을 Data Bank화 시켜 비드 종류나 형상에 따른 금형설계의 기초자료를 제공하고자 한다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1992.11a
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• pp.31-37
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• 1992

금형을 이용하는 소성가공에서는 형 사이에서 셩형되는 소재가 소성변형되지만 이때 소재는 형의 표면을 따라 미끄러지면서 유동하므로 형재료와 소재간에는 큰 마찰력이 작용하고, 형재료는 이 마찰력에 의하여 전단응력이 작용하게 된다. 따라서 이러한 전단응력이 반복하여 작용하는 프레스가공 등에서는 형의 수명이 항상 문제가 된다. 물론 형의 수명은 형재료가 프레스압력에 견디지 못하여 형이 균열되거나 펀치가 절단되는 것 같은 형재료의 강인성이 불충분하기 때문에 비교적 조기에 일어나는 파손에 의하여 수명의 대상으로 되는 경우도 있지만 무엇보다도 형의 수명을 죄우하는 가장 중요한 사항은 형재료의 내마멸성이다. 따라서 본 연구에서서는 이들 제인자를 고려하여 Die 및 Punch의 재료로 널리 사용되는 냉간성형용 Die강인 STD 11의 마멸특성을 알기 위하여 미끄럼 속도, 접촉압력 및 미끄럼 거리등을 변화시켜 내마멸성을 나타내는 최적사용조건을 찾고자 하는 것을 목적으로 하였다.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.142-148
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• 2005

In this paper, the stress singularity on interface of friction welded dissimilar materials was investigated by using 2-dimensional elastic boundary element method. It is required that stress distributions and stress singularities on an interface for friction welded dissimilar materials analize to establish strength evaluation. The stress singularity index ($\lambda$) and stress singularity factor ($\Gamma$) were calculated from the results of stress analysis. The stress singularities on variations for shapes and thickness of friction welded flashes were analized and discussed. This paper suggested that the strength evalution by using the stress singularity factors as fracture parameters, considering the stress singularity on an interface edge of friction welded dissimilar materials were very useful.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.6
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• pp.347-352
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• 2018

This study proposes seismic response analysis technique of a two-mass rack system which sustains heavy loads with frictional behavioral characteristics. In order to deal with the nonlinear frictional characteristics of the mass on the rack system, the equations of motion of the system has been derived and the appropriate numerical simulation technique has been developed. In order to examine the seismic performance of the proposed system, we consider two parameters that are expected to have great influence on the seismic performance of the system. One is the ratio of the two masses of the load and the rack structure, and the other is the friction coefficient between rack and loaded mass. A number of numerical simulations of the seismic response of structures with various natural frequencies for both parameters have been performed in order to investigate the seismic safety of the rack structures. From the simulated results. it is observed that the maximum displacement of the rack system tends to decrease drastically as the natural frequency of the structure increases regardless of the two parameters of mass ratio and friction coefficient. The proposed study provides important reference data to guarantee the seismic safety of the rack system by considering nonlinear frictional behavior of the loaded mass.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.5
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• pp.52-61
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• 2010

The use of the friction coefficient is known to provide good discrimination ability in the classification of human constitutions, which are used in alternative medicine. In this study, a system that uses a multi-axis load cell and a hemi-circular probe is designed. The equipment consists of a sensor (load cell type, manufactured by the authors), an x-axis linear-bush guide motorized mobile stage that supports the hand being analyzed, and a signal conditioner. Using the proposed system, the friction coefficients from different constitutions were compared, and the relative repeatability error for the friction coefficient measurement was determined to be less than 2 %. The direction along the ring finger line was determined to be the optimum measurement region for a constitutional diagnosis between Tae-eumin and Soyangin types using the proposed system. There were some differences in the friction coefficient between the two constitutions, as reported in ancient literature. The proposed system is applicable to a quantitative constitutional diagnosis between Tae-eumin and Soyangin types within an acceptable level of uncertainty.

• Journal of Aerospace System Engineering
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• v.17 no.1
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• pp.10-15
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• 2023

Wet multi-disk clutch, a power switching device of the ducted fan, was optimized and results were analyzed. The clutch was divided into two types depending on whether a mechanical lock-up was applied or not. It was optimized under each design condition. Transfer torque capacity, friction material surface pressure, friction surface temperature, and drag torque were calculated as factors to optimize the clutch. The volume of separator plate and drag torque were used as the objective function for optimization. In the case of Type 1, which did not include a mechanical lock-up, the clutch could be operated regardless of the pitch angle of the ducted fan. However, the outer diameter of the friction surface was doubled, the volume was increased by 5~7 times, and the drag torque was increased by 7~12 times compared to those of Type 2, which included a mechanical lock-up.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.04a
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• pp.401-405
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• 1994

위치작동기의 정밀도를 결정하는 중요한 인자인 마찰력을 없애기 위하여 자기부상을 이용한 초정밀 시스템을 설계한다. 자기부상시스템은 근본적으로 불안정한 성질을 갖고 있으므로 작동기의 안정성을 증가시킬수 있 는 자기회로설계가 종요하다. 제안된 자기부상 위치작동시스템은 전자석을 고정하고 영구자석을 움직일 수 있게하여, 간단하고 견고한 위치작동기가 설계되고록 상호간의 자기력을 이용한 Antagonistic 구조를 채택한다. 그리고 시스템의 동적모델을 구하여 안정성을 검토한다.

• Proceedings of the Korean Fiber Society Conference
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• 1998.04a
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• pp.249-252
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• 1998

니들펀칭 부직포는 구성 섬유소 집합체(web)를 바늘에 펀칭시켜 통과시킴으로써 섬유소간의 물리적인 결합력을 이용하여 제작한 섬유 구조물을 말한다. 니들펀칭 부직포의 물성에 미치는 인자는 크게 다음 세가지라고 볼 수 있다. 첫째, web을 구성하는 섬유의 물성이다.[1-4] 즉, 구성섬유의 인장성질이나 단면의 모양, 크림프의 존재유무, 섬도, 섬유길이, 마찰특성들이 부직포의 물성에 직접적인 영향을 준다.(중략)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1994.04a
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• pp.100-105
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• 1994

본 연구에서는 변속기 중립상태에서 클러치 설계 인자인 비틀림 스프링과 건마찰에 의해서 클러치에 나타나는 히스테리시스, 그리고 클러치 디스크의 정적처짐을 발생시키는 드래그토크(drag torque)가 클러치의 동적인 거동과 기어래틀에 미치는 영향을 분석하고자 한다.