• 한국공작기계학회논문집
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• 제16권6호
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• pp.133-139
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• 2007

In this paper, optics polishing technology using adaptive tool and eccentric motion mechanism was suggested. Optics polishing can make high reflective and accurate surface. The optics polishing process based on the eccentric motion mechanism has been used to manufacture the ophthalmic lens mold. Also ophthalmic lens mold factory hold conventionally a lot of the curved polishing tools for the versatile mold curves of eye diopters and want to reduce tool numbers. Therefore, a polishing machine with adaptive airbag tool was developed and experimentally verified in view of surface roughness and form accuracy.

• 소성∙가공
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• 제18권2호
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• pp.172-176
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• 2009

In this paper, new aspherical surface polishing mechanism is suggested to polish aspherical glass lens mold by both airbag polishing tool and reverse-rotational eccentric motion. Up to now, conventional aspherical lens polishing method by the small tool polishing uses the aspherical surface profile and the trajectory of the polishing tool is also controlled. However, full contact concept by airbag polishing tool and no position control make the easy polishing setup and does not need aspherical design profile. An aspherical lens polishing machine was made for this study and a tool mark removal experiment fur the fine-grounded lens mold was successfully performed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1660-1663
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• 2005

Unwanted vibrations are inevitably induced in other directions when pure unidirectional vibration motion is desired for the vertical scratching mechanism. Pure vertical vibration motion of the scratching machine can be obtained by driving identical two motors with symmetrically positioned eccentric unbalance masses. The desired optimal condition for driving pure vertical vibration for the scratching machine is assumed to be the resonance condition in that direction. Imposing the flexibility of the scratching machine in the horizontal direction, we can find out the amount of horizontal vibration component while maintaining the resonance in vertical direction. The desired stiffness in horizontal direction which produces the minimum vibration in horizontal direction are defined which can be used as a guide line to design the supporting structure of the scratching machine.

• 한국운동역학회지
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• 제18권4호
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• pp.21-30
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• 2008

본 연구에서는 신장성 수축운동에 의한 미세 근수축 요소 손강 이론(Morgan & Allen, 1999)을 검증하고자 신장성 수축운동의 범위에 따른 골격근의 기계학적 특성 변화에 주안점을 두어 실험 연구를 수행 하였다. 12명의 건강한 피험자가 최대 발목 족배굴곡근의 신장성 수축운동을 수행하였고, 운동수행 전에 최대 등척성 발목 족배굴곡 모멘트-각도 관계로부터 최적 발목 각도의 변화를 측정하였다. 신장성 수축운동 추 최적 발목 각도 변화는 신장성 수축운동의 범위와 상관없이 근육의 길이가 긴 쪽으로 변화를 가져왔다(4도, p<.05). 따라서 본 연구의 결과는 현재 많은 연구에서 거론되고 있는 신장성 수축에 의한 근력 저하 및 지연성 근육통의 촉발 기전인 신장성 수축에 의한 미세 근수축 요소 손강 이론의 부합하지 않으며, 이 현상을 설명할 새로운 이론 개발을 위한 후속연구의 필요성을 제기한다.

• 한국운동역학회지
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• 제24권2호
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• pp.131-138
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• 2014

The purpose of this study was to analyse the effect of the drop height on lower extremity and lower back kinematics and kinetics during drop landing with the use of raised heel insole. Furthermore we investigated the change that occurred in our body. Joint ROM, eccentric work and contribution to total work were calculated in 11 male college students performing drop landing with 8 motion analysis cameras and 1 forceplate. The result were as follows. First, the ROM and eccentric work were increased in all joints with the increase of the drop height. Second, the ankle ROM and eccentric work were decreased with the use of the insole. Third, the use of the lower back was increased as the use of the ankle decreased with the insole. Based on these results, we can infer that putting on the insole may contribute to chronic injury. We recommend not to use the insole during physical activity.

• Tribology and Lubricants
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• 제17권6호
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• pp.435-440
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• 2001

A numerical analysis between the piston and cylinder in hydraulic piston pumps under reciprocating motion is presented. A finite difference method and the Newton-Raphson method are used simultaneously to solve the Reynolds equation in the clearance and the equation of motion for the piston. The tapered piston showed stable behaviors regardless of their initial eccentric positions in the clearance, and the reciprocating speed affect highly on the piston end trajectories. Therefore, the numerical methods and results of present study can be used in the lubrication study of other piston-cylinder type fluid machineries.

• 설비공학논문집
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• 제10권1호
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• pp.33-43
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• 1998

Dynamic behavior of a scroll compressor has been investigated analytically. The equations of motion of moving elements of the scroll compressor such as the orbiting scroll, anti-rotation device, slider bush, and the crank shaft with eccentric crank pin have been set up. As the solutions of these equations, reaction forces between the moving elements, and also between the moving elements and the compressor frame have been calculated. The reaction forces from the moving elements to the frame are the unbalanced forces, which produce accelerations of the compressor body. These accelerations can be used as a measure of the compressor vibration. The major contributions to the unbalanced forces come from the orbiting movement of the orbiting scroll.

• 한국공작기계학회논문집
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• 제17권5호
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• pp.82-88
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• 2008

Conventional aspherical lens polishing methods by the small tool polishing use aspherical profile and the trajectory of the polishing tool is also controlled. In this paper, new full contact polishing mechanism is suggested to polish aspherical glass lens mold by both airbag polishing tool and eccentric motion. Full contact concept by airbag polishing tool and no position control make the easy polishing setup and do not need aspherical design profile. An aspherical lens polishing machine was made for this study and a verification experiment was performed for surface roughness improvements.

• 대한기계학회논문집A
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• 제41권10호
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• pp.991-996
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• 2017

인간의 보행에서 안정적인 디딤을 가능하게 하는 동작특성은 보행 일주기의 60%를 차지하는 긴 디딤국면이다. 본 연구에서는 이러한 보행패턴을 자전거의 크랭크 구동장치에 반영하여 직립자세에서 안정적으로 구동할 수 있는 자전거를 설계하고자 한다. 크랭크의 회전속도를 디딤국면에서는 느리게 되돌림국면에서는 빠르게 움직이도록 급속귀환 기구를 크랭크 구동시스템에 적용하였다. 이 급속귀환 크랭크기구의 설계변수를 정의하고 설계변수의 변화가 크랭크의 거동에 미치는 영향을 시뮬레이션 하였다. 또한 실험장치를 제작한 후 탑승자의 구동동작을 분석한 결과 보행패턴을 접목한 크랭크는 사용자 무게중심 안정화에 기여하는 것으로 나타났다. 향후 보행패턴을 접목한 크랭크는 서서 타는 자전거의 구동시스템에 접목 가능할 것으로 보인다.

• 소성∙가공
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• 제17권8호
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• pp.643-648
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• 2008

Ultra-thin sheet metal forming techniques are required in precision forming of miniaturized and integrated products. In order to manufacture a good quality and low cost ultra-thin sheet metal products, a highly precise high-speed press is needed. The precision of a press is related with its vibration characteristics during pressing operation. This study evaluated the vibration characteristics of a proposed press design using computer simulation. The analysis compares the static deformation characteristics of the slide and the slide motion for the metal forming of an ultra-thin sheet of thickness less than 0.1mm. Further, in order to minimize the vibrations during high speed pressing operation, revolution balances of the eccentric shaft and the balance weight device is also considered. Finally, modal analysis is used to characterize the natural frequency of vibration of the press.