• Tribology and Lubricants
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• 제23권4호
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• pp.156-161
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• 2007

The friction test using disk-on-pad type was carried out and regression analysis with friction parameters was applied fur wear loss presumption of motorcycle break disk. The wear loss has an effect on the frictional factor such as applied load, sliding speed, and number of ventilated disk hole. However, it is difficult to know the mutual relation of these factors on wear loss of motorcycle break disk. From this study, the result was shown that the regression analysis equation containing 4 elements were constructed and this equation had a trust of 95% in wear loss presumption of motorcycle break disk. It is possible to apply for another automobile parts.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.89-96
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• 2002

A two-degree of freedom model is suggested to understand the basic dynamical behaviors of the interaction between two masses of the friction induced vibration system. The two masses may be considered as the pad and the disk of the brake, The phase space analysis is performed to understand complicated dynamics of the non-linear model. Attractors in the phase space are examined for various conditions of the parameters of the model especially by emphasizing on the damping parameters. In certain conditions, the attractor becomes a limit cycle showing the stick-slip phenomena. In this paper, not only the existence of the limit cycle but also the size of the limit cycle is examined to demonstrate the non-linear dynamics that leads the unstable state. For the two different cases of the system frequency ((1)two masses with same natural frequencies, (2) with different natural frequencies), the propensity of limit cycle is discussed in detail. The results show an important fact that it may make the system worse when too much damping is present in the only one part of the masses.

• 오토저널
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• 제10권6호
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• pp.72-84
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• 1988

Engine performance is one of the main objectives specified at the beginning of a new engine design project. The cycle simulation for SI engine is based on the zero-dimensional gas exchange model and a heat release expression by Viebe. This program also requires minimum input data and takes only a short time to run. Heat transfer from cylinder transfer formula. The flow coefficient (effective area) is calculated from valve lift using the standard flow coefficient curve and engine friction is calculated from the Millington and Hartles' engine friction formula. The chemical species considered in burned gas are 6 species CO, CO, H$_{2}$, H$_{2}$O, $O_{2}$, N$_{2}$ and the cylinder pressure, homogeneous cylinder temperature, gas composition and burned fraction are calculated at each crank angle through the cycle. To check the validity and accuracy, experimental study was done with 3 engines for measuring cylinder pressure, indicated mean effective pressure, brake mean effective pressure and air flow rate, etc. Despite its simple assumptions, cycle simulation showes excellent breathing and performance correlation when compared with data of tested engines, and have been proved useful in engine design.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.405-410
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• 2004

There are two types of noises in running the rail vehicle. The one is periodic by electric motors, dehumidifiers, and dusting machines. And the other is aperiodic squeal noise by the frictions between the wheels and the rail or the disks and pads. The periodic noises in rail vehicle have been reduced by changing DC motors to AC motors with silencers, and by improving the lubricants. However, almost nothing relating a periodic noise has been studied. In this paper, the experimental methods were applied to understand phenomena of the squeal noise, which was occurred by the friction variation due to aperiodic stick and slip with low repeatability in the process of dry friction of the disk and the pad when a rail vehicle was being braked. By the experimental acoustic test, it was found the specific frequencies relating the squeal noise. And by modal testing, it was measured the resonant frequencies in the disk and the pad-plate which were the components of the braking system, and in the whole braking system, and it was found the specific frequencies having the effects on the squeal noise.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.676-681
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• 2001

ABS is a safety device, which adds hydraulic system to the existing brake system to prevent wheel from locking, so we can obtain maximum braking force on driving. The hydraulic system to control braking pressure consists of sol-flow type using solenoid valve, flow control valve or consists of sol-sol type using two solenoid valve. In this paper, the hydraulic system in ABS is composed of sol type using a 3port-2position solenoid valve, and vehicle system is composed of 1/4 vehicle model. And slip ratio is controlled using PWM (Pulse-Width-Modulation) control algorithm. Braking friction coefficient and tracking friction coefficient which are described by slip ratio's function have maximum value when slip ratio has its value from 0.1 to 0.3. And slip ratio is controlled constantly in this boundary value even in the variation of road's condition in some boundary.

• 한국소음진동공학회논문집
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• 제12권7호
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• pp.502-509
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• 2002

A two-degree of freedom model Is suggested to understand the basic dynamical behaviors of the interaction between two masses of the friction induced vibration system. The two masses may be considered as the pad and the dusk of the brake. The phase space analysis is performed to understand complicated dynamics of the non-linear model. Attractors in the phase space are examined for various conditions of the parameters of the model especially by emphasizing on the damping parameters. In certain conditions, the attractor becomes a limit cycle showing the stick-slip phenomena. In this Paper, not only titre existence of the limit cycle but also the sloe of the limit cycle is examined to demonstrate the non-linear dynamics that leads the unstable state. For the two different cases of the system frequency[(1) Two masses with same natural frequencies, (2) with different natural frequencies] . the propensity of limit cycle Is discussed In detail. The results show an important fact that it may make the system worse when too much damping Is present in the only one part of the masses.

• 한국산학기술학회논문지
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• 제11권4호
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• pp.1178-1185
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• 2010

철도차량의 고속화가 가속화되면서 화물을 운송하던 컨테이너 차량이 차륜의 파손에 의하여 탈선하는 사고가 발생하여 많은 물적 피해가 발생하고 있으며, 이러한 철도차량의 사고는 많은 인명 피해와 물적 피해를 가져오는 대형 사고로 발전할 수 있다. 따라서 이에 대한 재발 방지를 위한 차륜의 파손 해석에 대한 연구가 필요한 실정이다. 철도차량의 차륜은 기계적 하중과 열하중를 동시에 받으며, 기계적 하중으로는 철도차량의 무게에 의한 수직하중과 곡선 구간을 운행할 때 차륜과 레일의 접촉부에 수평하중이 발생하며, 철도차량의 제동시 답면제동에 의한 반복적인 열하중을 받는다. 이러한 차륜에 발생하는 기계적 하중과 열하중은 차륜의 균열과 잔류응력 등을 발생시키는 것으로 알려져 있다. 따라서, 본 연구에서는 차량 주행 시의 브레이크 이력과 하중 조건을 고려한 열 구조 연성해석을 수행하여 차륜에 부하되는 최대응력을 추정하였으며, 이 값을 파괴역학 파라미터인 응력확대계수에 적용하여 차륜의 안전성을 평가하였다.

• Tribology and Lubricants
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• 제21권5호
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• pp.227-235
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• 2005

This paper presents a tribological study on the failure cases of automatic transmission components in a passenger car. The automatic transmission system is composed of torque converter, clutch, brake, planetary gear, and valve body controlling oil pressure of an automatic transmission fluid. The most largest influence components in an automatic transmission are a torque converter and clutch plate in which are influenced by a wear and torque converting energy loss. The failure case study of an automatic transmission indicates that the tribological design and maintenance technologies should be considered as a key design concept. This means that the failure and power energy loss come from the friction, wear and a oil leakage of an automatic transmission, which is related to the oil seal and O-ring seal failures.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제29회 춘계학술대회
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• pp.332-338
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• 1999

A coupled thermal-mechanical analysis has been presented for the thermal distortions of the ventilated disk brakes during IS braking operations. The FEM results show that the bendings and distortions of the disk toward the left side are decreased, but the sinusoidal distortion of the disk rubbing surface along the arc length of the vent hole is highly increased by increasing the convective air cooling effects, which is heavily related to the squeal, wear and micro-thermal crackings at the rubbing surfaces due to uneven dissipation rates of friction heatings.

• 항공우주시스템공학회지
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• 제4권2호
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• pp.16-20
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• 2010

In General, the hydraulic system of T-50 Advanced Trainer is applied to flight control system, wheel & Brake system and fuel system for aircraft operation. The hydraulic system is operation with pressure of 3000psi. and many mechanical parts which is operated by hydraulic system has been stressed in incomplete environment same as heat and friction. for example, Oil leakage had occurred in the shutoff valve of FFP used in a certain period of time. After study, The crack progressed by fatigue due to the irregular hydraulic pressure and vibration has been identified as the reason of oil leakage. This paper presents life cycle extension plans of FFP shutoff valve by configuration improvements of shutoff valve and FFP hydraulic motor.