• Tribology and Lubricants
• /
• 제29권6호
• /
• pp.397-402
• /
• 2013

This study examined the tribological characteristics of the drive shaft and axle system in vehicles. The first drive shaft example contained end play for a CV joint that transferred part of the transmission power to the wheel. The joint part of the drive shaft was deformed because of reduced durability due to wear. Thus, vibrations caused the body to shake and become unbalanced when the drive shaft transferred the power. The second example was the cross-section of a shaft that connected the slip-connection of the propeller shaft on the input side to the yoke flange of the output side; the durability was reduced because of corrosion. End play caused by wear between the bearing and cross-section shaft appeared to cause shaking. In the third example, a grease leak reduced lubrication and thus caused damage to the hub bearing and inside the knuckle. The failure was produced by sticking. The fourth example had noise produced by the gear and gear transfer. This was due to the backlash of the pinion and few ring gears for the differential gear. Therefore, drive shaft and axle systems must be thoroughly checked and managed to minimize and reduce failure phenomena.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2008년도 춘계학술대회논문집
• /
• pp.132-139
• /
• 2008

The blade vibration problem of bladed disk is the most critical subject to consider since it directly affects the stable performance of the engine as well as life of the engine. Especially, due to complicated vibration pattern of the bladed disk, more effort was required for vibration analysis and test. The research of measuring the vibration of the bladed disk, using NSMS(Non-intrusive stress measurement) instead of Aeromechanics testing method requiring slip ring or telemetry system with strain gauge, was successful. These testing can report the actual stresses seen on the blades; detect synchronous resonances that are the source of high cycle fatigue (HCF) in blades; measure individual blade mis-tuning and coupled resonances in bladed disks. In order to minimize the error being created due to heat expansion, the tip timing sensor is installed parallel to the blade trailing edge, yielding optimal result. Also, when working on finite element analysis, the whole bladed disk has gone through three-dimensional analysis, evaluating the family mode. The result of the analysis matched well with the test result.

• Journal of Mechanical Science and Technology
• /
• 제19권2호
• /
• pp.655-663
• /
• 2005

Tribological characteristics in the sliding parts of oil hydraulic piston pumps are very important in increasing overall efficiency. In this study, the fluid film between the valve plate and the cylinder block was measured by using a gap sensor and the mercury-cell slip ring unit under real working conditions. To investigate the effect of the valve shape, we designed three valve plates each having a different shape. One of the valve plates was without bearing pad, another valve plate had bearing pad and the last valve plate was a spherical valve plate. It was noted that these three valve plates observed different aspects of the fluid film characteristics between the cylinder block and the valve plate. The leakage flow rates and the shaft torque were also investigated in order to clarify the performance difference between these three types of valve plates. From the results of this study, we found that the spherical valve plate estimated good fluid film patterns and good performance more than the other valve plates in oil hydraulic axial piston pumps.

• Journal of Mechanical Science and Technology
• /
• 제17권2호
• /
• pp.181-186
• /
• 2003

In order to assure the quality of the bent axis design axial piston pumps driven by tapered pistons, it is necessary to know the characteristics of force applied to tapered pistons and the mechanism for driving the tapered pistons. Since they are able to perform both reciprocating and spinning motions in cylinder block, it is difficult to understand the driving mechanismand-tomeasure the forces applied to tapered pistons experimentally In the present study, the theoretical mechanism for driving the tapered pistons is studied by use of the geometric method. The driving area of the tapered pistons is measured by measuring the strain of a cylinder forced against a tapered piston using an electric strain gauge and a slip ring. The forces applied to tapered pistons is also investigated with the change of discharge pressure and the rotational speed. As a results of this investigation, it is concluded that the cylinder block is driven by one tapered piston in a limited area and the driving area is changed due to space angle of the tapered pistons and the swivel angle of the cylinder block. It is also observed that the force applied to tapered pistons increases as the discharge pressure and the rotational speed increase.

• Journal of Mechanical Science and Technology
• /
• 제17권2호
• /
• pp.246-253
• /
• 2003

The tribological mechanism between the valve plate and the cylinder block in oil hydraulic axial piston pumps plays an important role on high power density. In this study, the fluid film thickness between the valve plate and the cylinder block was measured with discharge pressure and rotational speed by use of a gap sensor, and a slip ring system in the operating period. To investigate the effect of the valve plate shapes, we designed two valve plates with different shapes . the first valve plate was without a bearing pad, while the second valve plate had a bearing pad. It was found that both valve plates behaved differently with respect to the fluid film thickness characteristics. The leakage flow rates and the shaft torque were also experimented in order to clarify the performance difference between the valve plate without a bearing pad and the valve plate with a bearing pad. From the results of this study, we found out that in the oil hydraulic axial piston pumps, the valve plate with a bearing pad showed better film thickness contours than the valve plate without a bearing pad.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2015년도 제46회 하계학술대회
• /
• pp.1106-1107
• /
• 2015

A flux pump (FP) can inject the DC current into high temperature superconducting (HTS) field coils of a HTS rotating machine without slip ring and current lead. However, it has limits to improve the value of DC current, and has time constants of DC current according to inductances of the HTS field coils. When a large-scale HTS generator with the FP is designed, a proper point about the inductance, field current, and time constant is demanded to decide parameters of the generator. In this paper, a parameter tuning skill of a large-scale superconducting wind power generator for applying a FP has been proposed. The design of the FP has been fixed, and 12 MW HTS generators have been variously designed by adjusting parameters related with the inductance of the HTS field coil. The induced current values have been calculated based on the FP design. The time constants of the induced currents depending on the DC current values and inductances of the generator have been represented. The results of the parameter tuning of the HTS generator have been discussed in detail.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집B
• /
• pp.765-770
• /
• 2000

Hot-wire measurements are reported on the developing turbulent flows subject to plane rate of strain in a rotating $90^{\circ}$ dog bend. The cross-section of the bend varies from $100mm{\times}50mm$ rectangular shape at the bend inlet gradually to the $50mm{\times}100mm$ shape at the bend outlet with remaining a constant area. Data signals from the rotating test section are transmitted through a slip ring to the personal computer which is located at the outside of the rotating disc. 3-dimensional velocity and 6 Reynolds stress components were calculated from the equations which correlate the fluctuating and mean voltage values measured with rotating a slant type hot-wire into 6 orientations. The effects of Coriolis and centrifugal forces on the mean motions and turbulence structures are investigated with respect to rotational speed.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
• /
• pp.220.2-220.2
• /
• 2014

플라즈마 질화 기술은 기존의 침탄 혹은 고주파 표면 경화 기술 대비 낮은 온도에서 열처리 공정이 진행됨에 따라 열 변형을 최소화 시킬 수 있으며, 후 가공을 간소화 시킬 수 있다는 장점으로 인해 자동차 부품 및 기타 응용 산업 분야에 있어 큰 관심을 받고 있다. 그러나 공정 진행에 장시간이 소요되고 복잡한 형상 및 홀 가공에 의한 기능부, 특히 내경부에 대한 균일 질화 처리가 어려워 실제 응용분야 확장에 큰 제약이 따르고 있다. 이를 해결하기 위해 본 연구에서는 일반 글로우 방전 대비 플라즈마 밀도가 10배 이상 높은 공공 음극 방전(Hollow Cathode Discharge, 이하 HCD) 현상을 이용하여 고속 고균일 질화공정을 개발하고자 하였으며, 상용화 적용을 위한 연구를 함께 진행하였다. 사용된 시료로는 실제 자동차 부품으로 사용되는 SCM415 소재의 ring gear와 slip yoke pipe를 사용하였으며, HCD 형성을 위해 특화된 플라즈마 질화장비를 활용, 공정 압력 및 인가 전력 등을 변수로 실험을 진행 하였다. 그 결과 질화 처리 속도에 있어 기존 글로우 방전 플라즈마 질화 대비 1/4 이하 수준으로 그 소요 시간을 단축시킬 수 있었으며, 다량 장입된 시료의 내경 기능부에 있어서도 높은 균일도를 갖는 질화표면이 형성됨을 확인할 수 있었다. 또한 기능부 표면에 형성된 HCD 현상을 열원으로 사용함으로써 외부가열 장치를 사용하지 않으면서도 기존의 hot wall 방식보다 높은 질화 균일도 구현이 가능하였으며, 소요 자원 및 전력 사용 측면에 있어서도 공정 시간 단축 및 외부 가열 공정 제거에 의한 높은 수준의 에너지 절약이 가능하였다.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2005년도 연구개발 발표회 논문집
• /
• pp.448-453
• /
• 2005

Temperature Control Valve (TCV) is one of the useful temperature control devices, which is used to control constant temperature of working fluid in power and chemical plants and domestic water supply systems. TCV is composed of body, cylinder and piston, and the body shape has a symmetrical H-type. In general, it has several inlet and outlet holes, and its shape is like as tubular sleeve. The piston has three rings two rings of the end of piston have the function of controlling inlet flow rate with hot and cold working fluids, the center ring has the function of preventing hot and cold water from intermixing. Consequently, the shapes of piston and cylinder are the main design parameters in the performance of TCV. In this study, numerical analyses were carried out with two different piston and cylinder shapes to investigate the functions as a temperature control valve and the flow characteristics according to piston opening grade in TCV. Using a commercial code, FLUENT, velocity and pressure fields in TCV are obtained under steady, standard $k -{\epsilon}$ turbulence model and no-slip condition.

• Tribology and Lubricants
• /
• 제10권1호
• /
• pp.14-26
• /
• 1994

The minimum oil film thickness(MOFT) in the connecting-rod bearing of a 1.5 liter, L-4, gasoline engine is measured up to 5500 rpm and calculated to study the dynamically loaded engine bearing. Short bearing approximation and Mobility method are used for theoretical analysis of oil film characteristics. And cylinder pressure, crank-pin surface temperature and bearing temperature are measured as the input data of theoretical analysis. The MOFT are measured by the total capacitance method(TCM). To improve the reliability of the test results, a reasonable determination method of bearing clearance is introduced and used, and the effects of cavitation and aeration on the test results are neglected. The crankshaft is grounded by means of a slip ring. A scissor type linkage system was developed to measure the MOFT and bearing temperature. The effects of engine speed, load and oil viscosity on the measured and calculated minimum oil film thicknesses are investigated at 1500 to 5500 rpm. From the comparison between the measured and calculated MOFT, it is found that a qualitative similarity exists between them, but in all cases, the measured MOFT are smaller than those calculated.