• Tribology and Lubricants
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• 제9권2호
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• pp.70-78
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• 1993

Using the finite element method, the film pressure, the transverse force and the firction torque which are distributed over the pad surface of low-friction piston skirt are calculated in order to investigate the dynamic characteristics of the piston. The results indicate that the frictional torque for the low-friction piston pad may increase 3% efficiency in comparison th the conventional one.

• Tribology and Lubricants
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• 제30권6호
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• pp.337-342
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• 2014

The reduction of drag torque is an important research issue in terms of improving transmission efficiency. Drag torque in a wet clutch occurs because of the viscous drag generated by the transmission fluid in a narrow gap (clearance) between the friction plate and a separate plate. The objective of this paper is to observe the effects of the friction plate area and the clearance on the drag torque using finite element simulation. The two-phase flow of air and oil fluid is considered and modeled for the simulation. The simulation analysis reveals that as the rotational speed increases, the drag torque generally increases to a critical point and then decreases sharply at a high speed regime. The clearance between the two plates plays an important role in controlling drag torque peak. An increase in the clearance causes a decrease in shear stress; thus, the drag torque also decreases according to Newton's law of viscosity. An observation of the effect of the area of contact between transmission fluid and friction plate shows that the drag torque increases with the contact area. The flow vectors inside the flow channel present clear evidence that the velocity of the fluid flows is faster with a larger friction plate, that is, in the case of a larger contact area. Therefore, the optimum size of the friction plate should be determined carefully, considering both the clutch performance and drag reduction. It is expected that the results from this study can be very useful as a database for clutch design and to predict the drag torque for the initial design with respect to various clutch parameters.

• 한국소음진동공학회논문집
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• 제17권7호
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• pp.649-661
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• 2007

Friction-type reinforcing members(FRM) to enhance the resistance to wind loads of a transmission tower through both stiffness strengthening and damping increase are energy dissipation devices that utilize bending deflection of a tower leg. In this paper, the hysteretic behavior of the transmission tower structure with FRMs was experimentally investigated through cyclic loading tests on a half scale substructure model. Firstly, the variation of friction forces and durability of the FRM depending on the type of friction-inducing materials used in the FRM were examined by performing the cyclic loading tests on the FRM. Secondly, cyclic loading tests of a half-scale two-dimensional substructure model of a transmission tower with FRMs were conducted. Test results show that the FRM, of which desired maximum friction force is easily regulated by adjusting the amplitude of the torque applied to the bolts, have stable hysteretic behaviors and it is found that there exists the optimum torque depending on a design load by investigating the amount of energy dissipation of the FRMs according to the increase of torque.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.568-577
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• 2007

Friction-type reinforcing members (FRM) to enhance the resistance to wind loads of a transmission tower through both stiffness strengthening and damping increase are energy dissipation devices that utilize bending deflection of a tower leg. In this paper, the hysteretic behavior of the transmission tower structure with FRMs was experimentally investigated through cyclic loading tests on a half scale substructure model. Firstly, the variation of friction forces and durability of the FRM depending on the type of Friction-inducing materials used in the FRM were examined by performing the cyclic loading tests on the FRM. Secondly, Cyclic loading tests of a half-scale two-dimensional substructure model of a transmission tower with FRMs were conducted. Test results show that the FRM, of which desired maximum friction force is easily regulated by adjusting the amplitude of the torque applied to the bolts, have stable hysteretic behaviors and it is found that there exists the optimum torque depending on a design load by investigating the amount of energy dissipation of the FRMs according to the increase of torque.

• 대한치과교정학회지
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• 제21권3호
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• pp.543-560
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• 1991

Practitioners are aware of the presence of friction between bracket system and archwire during sliding movement of teeth. Clinically a mesiodistally applied force must exceed the frictional force to produce a tooth movement. The objective of this study were to determine, on a dry condition, changes in magnitude of friction with respect to load, 3rd order inclination (Torque), archwire materials and ligature type. Three wire alloys (Stainless Steel, TMA, NiTi) in two wire sizes (.016, .016x, .022 inch) were examined respect to two bracket system (Straight, Standard), and two ligature type (Metal, Plastic ligature) at three levels of load (100g, 150g, 200g). The results were as follows; 1. Frictional resistance was found to increase with increasing load for S.S., TMA, NiTi. 2. The straight bracket system was exhibited more frictional force than standard bracket system for .016x, .022 S.S. tightly ligated metal ligature. But, torque difference did not increase friction for loose metal ligature & plastic ligature. 3. Regardless of the ligature type, torque and load, stainless steel wire sliding against stainless steel exhibited the lowest friction, and TMA sliding against stainless steel exhibited the highest friction. 4. The loose stainless steel ligature generated lower frictional resistance than plastic ligature in all experimental groups. 5. The following factors affected friction in decreasing order; wire material ligature type, and load.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.986-992
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• 2014

This research investigates experimentally and numerically the tilting angle, eccentricity ratio, flying height of axial direction, friction torque, and critical mass of the HDD disk-spindle system due to HDD positioning angle. The tilting angle and the eccentricity ratio are the maximum when the HDD positioning angle is $90^{\circ}$ respect to horizontal position because the external force in radial direction and the torque applied to the rotating part are the maximum when the HDD positioning angle is $90^{\circ}$. The flying height increases with the increase of the HDD positioning angle because the direction of gravity applied to the rotating part changes. The friction torque increases with the increase of the HDD positioning angle until it becomes $60^{\circ}$, and decreases with the increase of the HDD positioning angle after it becomes $60^{\circ}$. The stability is the maximum when the HDD positioning angle is $90^{\circ}$.

• Tribology and Lubricants
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• 제33권2호
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• pp.71-78
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• 2017

The drag torque in the wet clutch system of a dual clutch transmission system is investigated because it is relatively high, up to 10 of the total output torque of the engine, even when the clutch is in the disengagement state with zero torque transfer. Drag torque results from the shear resistance of the DCTF between the friction pad and separator plate. To reduce the drag torque for ensuring fuel economy, the groove pattern of the wet clutch friction pad is designed to have a high flow rate through the pattern groove. In this study, four types of groove patterns on the friction pad are designed. The volume fraction of the DCTF (VOF) and hydrodynamic pressure developments in the gap between the friction pad and separator plate are computed to correlate with the computation of the drag torque. From the computational results, it is found that a high VOF and hydrodynamics increase the drag torque resulting from the shear resistance of the DCTF. Therefore, a patterned groove design should be used for increasing the flow rate to have more air parts in the gap to reduce the drag torque. In this study, ANSYS FLUENT is used to solve the flow analysis.

• 대한치과보철학회지
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• 제54권1호
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• pp.8-13
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• 2016

목적: 본 연구의 목적은 두 가지(스프링형, 마찰형) 종류의 기계식 임플란트 토크 렌치를 2000회의 반복 사용과 100회의 멸균과정 후 그들의 정확도를 평가하는 것이다. 재료 및 방법: 각기 다른 5개 제조사의 스프링형, 마찰형 기계식 임플란트 토크 렌치가 각 15개씩, 총 30개 사용되었다. 디지털 토크 측정기(MGT-12, Mark-10 Corp, USA)를 이용하여 토크값을 실험 전 최초 측정 후 각 토크 렌치를 같은 조건(목표 토크 값까지 20회씩 반복 사용 후 멸균봉투에 포장하여 고압증기 멸균 시행)으로 100회 반복 시행하였다. 그 후 다시 토크값을 측정하여 비교하였다. 수집된 자료는 SPSS 통계분석 프로그램을 이용하여 분석하였고 오차율을 계산하였다. Mann-Whitney-U test를 이용하여 실험군 사이의 유의성을 분석하였다(P<.05). 결과: 스프링형 토크 렌치는 실험 전후로 토크값의 유의할만한 차이를 보이지 않았다(P>.05). 반면에 마찰형 토크 렌치는 실험 전후로 토크값의 유의할만한 차이를 나타내었으며(P<.05), 10% 이상의 오차율이 모두 마찰형 토크 렌치에서 나타났다. 결론: 본 연구의 제한된 실험 조건하에서 스프링형 토크 렌치가 마찰형 토크 렌치보다 사용횟수와 멸균과정을 고려했을 때 더욱 신뢰성이 높은 정확도를 보였다.

• 한국산학기술학회논문지
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• 제17권6호
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• pp.687-692
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• 2016

엔진에 터보차져를 사용하게 되면 엔진의 출력도 향상되지만 동시에 엔진의 온도도 높아지게 된다. 특히 피스톤의 경우는 냉각이 문제가 된다. 이러한 문제를 해결하기 위하여 오일 젯을 사용하는데, 오일 젯은 오일을 피스톤의 밑 부분에 분사하여 피스톤을 냉각시키는 것이다. 오일 젯이 사용된다면, 오일의 분사로 인하여 오일 유량의 증가및 피스톤으로부터의 열전달에 의하여 높아진 오일 온도 문제를 해결하기 위하여 오일 펌프 용량 증대와 오일 쿨러의 사용이 필요하다. 그러나 용량 증대 오일 펌프와 오일 쿨러를 사용하면 엔진의 마찰 토크가 증가하는 원인이 된다. 본 연구에서는 오일 젯, 오일 쿨러 및 오일 펌프의 용량 증대로 인하여 엔진의 마찰 토크가 증가하는 정도에 대하여 연구하였다. 또한 각 부품의 사양을 변경함에 따라 마찰 토크가 얼마나 영향을 받는가도 측정되었다. 저속에서는 오일 펌프와 오일 쿨러에 의한 영향이 크고 고속에서는 오일 쿨러에 의한 영향이 큼을 알 수 있었다.

• 한국정밀공학회지
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• 제2권3호
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• pp.28-40
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• 1985

In this study, to check up on the effect of the components of cutting resistance upon friction between drill and inside wall of hole in drilling, the experiment was performed with individual specimen of carbon steel, cast iron, aluminium alloy under various cutting conditions: depth of hole, cutting speed, feed rate, shape and material of specimen. On the basis of the experimental results, the following conclusions are drawn; 1. The components of cutting resis- tance were increased in proportion to the increase of depth of hole owing to frictional resistance of drill margin and chip-jamming. 2. As feed rates increase, torque and thrust were increased. When comparing to the increasing rate for these components respecitively, thrust is higher tendency than torque. 3. As drill diameter increase, torque and thrust were increased. When comparing to the increasing rate for these components respectively, torque is higher tendency than thrust. 4. In the case of torque, the frictional resistance between drill margin and inside wall of drilled hole accounts for about 20 percent of carbon steel, 14 of cast iron, 10 aluminium alloy in drilling. But the effect of thrust force could be negligible. 5. Comparison between the theoretical and experimental results showed a close agreement so far as depth of hole is about three times of drill diameter. But there was a wide difference between them beyond the rane of three times, because of characteristics of the drilling process.