• Tribology and Lubricants
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• 제35권3호
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• pp.183-189
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• 2019

The driver seat of an automobile is in direct contact with the driver and provides the driver with a safe and comfortable ride. The seat consists of a frame, a rail, and many recliners. In recent years, strength and operating force measurement testing of the recliner have become vital for designing car seats. However, performance evaluation requires expensive testing equipment, numerous seat products, and considerable time. Therefore, the trend is to reduce experimentation through interpretation. This study examines the lubrication of solid lubricant for automotive seat recliners and confirms the friction and wear performance. In this study, the lubrication behavior of solid lubricants for car seat recliners is investigated to ascertain the friction and wear performance and to provide accurate values for the strength analysis. The friction material consists of a pin and a plate made from steel, which is widely used in recliners. The friction and wear under lubrication conditions are measured by a reciprocating friction wear tester. The friction coefficient is obtained according to the load and speed. Based on the obtained results, it is possible to achieve a reduction in the error of the test value and the analysis by providing the friction coefficient and wear of the lubricant. The results can be applied to the analysis of automobile seat design.

• 구강회복응용과학지
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• 제33권4호
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• pp.284-290
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• 2017

구순구개열 환자에게 가철성 보철치료는 중요한 치료 선택 중 하나이다. 구순구개열 환자에서 만족스러운 기능적 및 심미적 결과를 얻기 위해서는 전통적인 보철 치료법에서 약간의 수정이 필요할 수 있는데, 치주 질환에 이환되어 있으며 소수의 구치만 잔존해 있는 구개열 환자의 경우 이중관에 연결된 가철성 보철이 치료 선택의 대안이 될 수 있다. 이중관이 가철성 국소의치에 연결되면 보철적 안정성과 유지를 증가시키고 치아 장축에 유리한 힘 전달을 최적화하며 심미성도 향상시킨다. 그리고 이중관 의치의 횡단치열궁안정(cross arch stabilization)은 구순구개열 환자의 갈라진 치조제의 안정화에도 도움을 준다. 본 증례는 성인 구순구개열 환자에서 마찰핀(friction pin)을 사용한 혼성 이중관 가철성 국소의치를 제작하여 유지 및 안정성과 함께 심미성도 향상시켜 만족할 만한 결과를 나타낸다.

• 한국산학기술학회논문지
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• 제12권5호
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• pp.2061-2066
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• 2011

사이클로이드 감속기는 기계의 회전수를 조절하기위한 장치이다. 사이클로이드 감속기는 큰 토크로 변환시킬 수 있는 장점이 있지만 높은 회전수 에는 적합하지 않다. 한편 200톤 하중이 가해지는 수송기기에 있어서 감속기의 사용한계속도를 찾아내기는 불가능하다. 본 연구에서는 LS-DYNA를 이용하여 마찰손실동력을 수치 해석적으로 검토하였다. 최대토크3.5ton-m에 있어서 회전수 60rpm 그리고 162rpm으로 구동하여 해석을 수행한 결과 다음과 같은 결과를 얻었다. 60rpm회전의 경우 최대응력은 RV gear의 경우 463MPa 핀기어의 경우 507MPa이 발생하였다. 마찰손실동력은 50kW이며, 162rpm의 경우 최대응력값은 RV gear와 핀기어 각각 550MPa, 538MPa이 발생하였다. 손실동력은 175kW이 발생하여 사용이 불가능하다는 것을 알 수 있었다.

• 열처리공학회지
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• 제12권2호
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• pp.136-144
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• 1999

The study on the wear characteristics of compound layers formed during gaseous nitrocarburising in the medium carbon boron steels and the plain carbon steel has been carried out by using a pin-on-disc type wear test machine under the oil lubricating condition at room temperature and by varying applied loads, sliding speeds and wear distances. Values of friction coefficient measured at the sliding speed of 0.4m/sec under the oil lubricating condition have been shown to decrease considerably with increasing applied load and become gradually a constant value as load is increased to a higher value, showing that the transition load for friction coefficient appears at an applied load of 247.2N. The length and volume wear rates of compound layer have been revealed to relatively constantly increase, also showing that the wear life per unit thickness of compound layer turns out to be superior as porous layer has a denser and thinner appearance. As the sliding speed increases during wear test performed by varying sliding speed at a load of 63.2N under the oil lubricating condition for medium carbon boron steel nitrocarburised in gas atmosphere, the wear rate has been found to increase, the friction coefficient to decrease and the wear life per unit thickness of compound layer to decrease considerably.

• Tribology and Lubricants
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• 제35권6호
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• pp.396-402
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• 2019

Materials made from plastics are increasingly utilized in constructing greenhouses and setting up shield structures. Polyester fabrics have a wide range of use in horticulture and other fields of agriculture. They are utilized as a greenhouse cover and also help in combating intense climate variation in the field. Over time, these fabrics may experience friction against other surfaces. Owing to this, the surface framework of the material degenerates. This study examines the frictional characteristics of aluminized polyester fabric in both dry- and water-lubricated environments under changing applied loads and sliding speeds. Friction experiments are performed at room temperature by employing a pin on a disk. The experiments reveal that the friction coefficient decreases with increase in applied load in both dry sliding and water-lubricated environment. However, the friction coefficient decreases more under the water-lubricated setting than in the dry state. At the maximum applied load, the highest friction coefficient is discovered in the dry state with a range of 0.282 to 0.237, whereas a friction coefficient of 0.229 to 0.189 is observed in the water-lubricated state. Additionally, it is observed that the friction coefficient increases with an increase in sliding speed under both experimental environments. The examination of specimen surfaces reveals that the abrasion is minor in the water-lubricated setting compared with that in the dry state.

• Tribology and Lubricants
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• 제35권6호
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• pp.356-361
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• 2019

The friction and wear between machine components directly influence the energy loss and failure in various machines. Therefore, there is always a demand for finding methods to reduce friction and wear. Of the possible methods, lubrication is a widely used method for reducing friction and wear. In the case of lubrication, it is important to analyze the tribological behavior in the boundary lubrication because most of friction and wear occurs in the boundary lubrication regime. Cast iron has been regarded as a good material for industrial applications due to the excellent mechanical properties and high productivity. Especially, nodular cast iron is a material that shows better mechanical properties and wear-resistance compared with cast iron due to inclusion of spheroidal graphite. In this work, we investigated the tribological characteristics of nodular cast iron with respect to different counter parts in boundary lubrication regime. Sliding tests were conducted with SUJ2, ZrO₂, Si₃N₄ balls as counter parts using a pin-on-disk type tribotester. The results showed different friction and wear behaviors with different counter parts. The case of ZrO₂ showed the lowest wear rate in specimen and no significant ball wear. In case of SUJ2, it showed similar wear rate with ZrO₂ case in specimen and the highest friction coefficient. The case of Si₃N₄ showed the lowest friction coefficient, 33% lower than the case of SUJ2. It showed 16.9 times larger wear rate in specimen and 43% larger wear rate in ball compared to that of the SUJ2 case.

• Tribology and Lubricants
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• 제36권1호
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• pp.11-17
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• 2020

In manufacturing operations, oil plays a crucial role in reducing friction and wear among interacting surfaces at varying velocities, loads, and temperature. Hydrocarbon oil is considered the origin of lubrication oils. However, this base oil has been limited in its use as it is a principal cause of pollution. This research focuses on identifying a biodegradable base oil lubricant that possesses a stable coefficient of friction and viscosity with temperature. Friction analysis is conducted by employing a pin on a disk tribotester with a fixed load of 10 N at varying sliding speeds ranging from 0.06 m/s to 0.34 m/s. Oil viscosity analysis is perfomed at room temperature by using a rotary viscometer. Tests are performed using canola oil and paraffin oil as lubricants. The results indicate that the viscosity of canola oil is more efficient than paraffin oil. The non-dimensional characteristic number according to the Stribeck curve reveals an elastohydrodynamic lubrication regime with canola oil lubrication. A comparison of both lubricants reveals that, the friction efficiency of canola oil and paraffin oil does not differ considerably. However, the friction in canola oil is observed to decrease more than that in paraffin oil at an elevated sliding speed. The tests confirm that canola oil is potent in minimizing the friction coefficient of SCM440 bodies interacting with one another as well as acted upon by load.

• Tribology and Lubricants
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• 제34권6호
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• pp.254-261
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• 2018

In order to reduce resistance torque and energy loss, minimizing friction between race surface and rolling elements of a bearing is necessary. Recently, to reduce friction in bearing element, solid lubricant coating for the bearing raceway surface has been receiving much attention. Considering the operating conditions of real bearings, verifying the effect of solid lubricant coatings under extreme conditions of high load that is more than 1 GPa is necessary. In this study, we evaluated the friction and wear characteristics of SUJ2 bearing steels deposited by carbon-based coatings (Si-DLC, ta-C), $MoS_2$ and graphite. In case of $MoS_2$ and graphite coatings, different surface treatments were applied to the coatings to verify the effect of surface treatment. A pin-on-disc type tribotester was used to evaluate the tribological characteristics of the coatings. It was possible to quantitatively estimate the friction and wear characteristics of solid lubricant under dry and lubrication conditions. The carbon-based coatings improved the friction and wear properties of SUJ2 bearing steels under the high load condition, but $MoS_2$ and graphite coatings were not suitable for high load conditions due to its low hardness. Different friction and wear behaviors were found for different substrate surface treatment method. Also, it was confirmed that solid lubricant coatings had a more positive effect than just applying the lubricant for improving the tribological characteristics.

• 한국항공우주학회지
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• 제41권8호
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• pp.625-631
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• 2013

핀풀러의 신뢰도를 몬테카를로 시뮬레이션을 통해서 예측하였다. 예측방법은 응력-강도 간섭 모델에 근거한다. 이 모델은 강도가 응력보다 작을 경우를 고장으로 간주한다. 본 연구에서 강도는 핀을 예정된 거리까지 후퇴시키는데 필요한 에너지로, 응력은 이 핀의 운동을 방해하는데 소요되는 에너지로 간주하였다. 전자는 주로 화약량에 의해 결정되고 후자는 여러 가지 마찰력과 반발방지장치에서 소모되는 에너지에 의존한다. 응력과 강도 변수들은 해석적 성능 모델로부터 계산하였다. 본 연구에서 제시된 방법은 많은 시료가 필요하지 않기 때문에 유사한 종류의 파이로 장치 신뢰도 계산에도 적용될 수 있다.

• 한국자동차공학회논문집
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• 제21권4호
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• pp.77-82
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• 2013

In this paper, the design of experiment with two-way factorial design was adopted and from that, optimum values of welding variables including the welding speed and rotation speed were found to improve the strength of AZ31 magnesium alloy sheets joined by the friction stir technique. Tool with shoulder diameter of 12 mm and pin diameter of 3.5 mm was used. Also the welding direction was aligned with the material rolling direction, and dimensions of the AZ31 magnesium alloy sheets were $100{\times}100{\times}2mm$. Conditions of rotation speed were 1000, 1100 and 1200 rpm and those of welding speed were 200, 300 and 400 mm/min. As far as this work is concerned, the optimal conditions for friction stir joint were predicted as the rotation speed of 1200 rpm and welding speed of 200 mm/min.