• Tribology and Lubricants
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• v.29 no.1
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• pp.1-6
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• 2013

Hydraulic transmission is the main component delivering power to the drive wheels of an excavator during forward and backward movement, and it has low speed, high torque and high speed, low torque gear change ratios as a forward/backward two-speed main function. It also has additional function of ensuring that the excavator is stably fixed on the ground with the built-in parking brake during excavation operations. In this study, optimal design specifications are determined by modeling and simulating about the multi-disc-type friction clutch, which is the main component improving the reliability of the hydraulic transmission for a 14-ton wheel excavator, and the friction properties of the transmission clutch are analyzed by performing sample tests.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.54-63
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• 2022

This paper is a study on the friction damper, which is one of the seismic reinforcement devices for structures. This study developed a damper by replacing the internal friction material with ultra high molecular weight polyethylene (UHMWPE), a type of composite material. In addition, this study applied a multi-friction method in which the internal structure where frictional force is generated is laminated in several layers. To verify the performance of the developed multi-friction damper, this study performed a characteristic analysis test for the basic physical properties, wear characteristics, and disc springs of the material. As a result of the wear test, the mass reduction rate of UHMWPE was 0.003%, which showed the best performance among the friction materials based on composite materials. Regarding the disc spring, this study secured the design basic data from the finite element analysis and experimental test results. Moreover, to confirm the quality stability of the developed multi-friction damper, this study performed an seismic load test on the damping device and the friction force change according to the torque value. The quality performance test result showed a linear frictional force change according to the torque value adjustment. As a result of the seismic load test, the allowable error of the friction damper was less than 15%, which is the standard required by the design standards, so it satisfies the requirements for seismic reinforcement devices.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.511-512
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• 2011

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.4
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• pp.330-336
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• 2017

This study performs a root cause analysis of the sticking that occurs in the hydraulically actuated wet type multi-disc friction clutch in a ship's diesel engine propulsion system that uses rubber elastic coupling. The fishbone method was used to study the sticking through dismantling investigation of the reduction gear and clutch, investigation of the components, and onboard system tests including nondestructive testing. The friction plate sticking is caused by the slip due to friction heat resulting from the leakage of control oil through cracks in the assembled hollow shaft. The friction plate cooling oil also leaks simultaneously through the crack, and partial sticking occurs due to the hot spots in the friction plates. These are caused by insufficient amount of cooling oil due to oil leakage.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.546-552
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• 2012

This paper is a study on squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material. For this, data of pressure and temperature dependent material properties of lining is achieved by using lining data base and exponential curve fit. Complex eigenvalue analysis is performed for predicting squeal noise frequency and instability and chassis dynamo test is performed for achieving squeal noise frequency, sound pressure level, occurrence temperature & pressure. Initial multi models are composed for considering complex interface conditions such as pad ear-clip, piston-housing and guide pin-torque member. The simulation result of base models is compared with the test result. Squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material is performed and analyzed using multi models. And additional condition is disc material property variation. Entire simulation conditions are combined and analyzed. Finally, this paper proposes direction of the warm squeal noise model.

• Journal of Power System Engineering
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• v.16 no.6
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• pp.66-72
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• 2012

The parking brake embedded in track driving motor for driving an excavator is composed of wet type multi-friction discs. This type parking brake can be designed more compact because the combination of some sheets of friction discs generate great braking power, and also it has good braking characteristic and long life time because it works in the oil. In this study, we analyzed torque characteristic of the parking brake through simulations and performed experiments by use of 3-kinds of paper friction sheet manufactured by different pressing methods. And, we compared the maximum static friction coefficient and torque characteristic with the simulation results and confirmed the optimal manufacturing process through this result.

• Journal of the Korean Society of Safety
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• v.23 no.3
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• pp.25-29
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• 2008

In automotive disc brake system, friction heat is not uniformly distributed due to various reasons such as thermal expansion and imperfections in geometry. It is well known that thermoelastic distortion due to fictional heating affects the contact pressure distribution and can lead to thermoelastic instability, where the contact load is concentrated in one or more small regions on the brake disc surface. These regions then take very high temperatures and passage of hot spots moving under the brake pads can cause low frequency vibration called brake judder. This paper presents the FEM(finite element method) result for the temperature distribution of ventilated disc brake. A steady state two-dimensional model of disc brake system predicts the surface temperatures during a multi-stop driving schedule.

• Journal of the Korean Society of Industry Convergence
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• v.8 no.3
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• pp.135-141
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• 2005

The static friction coefficients of 4 samples against each different temperatures were similar values. Compared against RT, at $80^{\circ}C$ the static friction coefficients decreased from 0.130 to 0.116 that was equal from 88% to 90% of the static friction coefficients respectively. Otherwise the dynamic friction coefficients compared against RT, decreased from 0.138 to 0.088 which was from 71% to 77.5% respectively at $80^{\circ}C$. The noise characteristics were judged by s/d value. And when the s/d value was limited less than 0.8, noise concerns were released. At 3000 engaging cycles the static friction and the dynamic friction coefficient were 0.137 and 0.073 respectively. When plate pressure rose up to $195kg_f/cm^2$, the static friction coefficient decreased from 0.137 to 0.125 but this decreasing could be considered as stable. When speed rose up to 2200rpm, the static friction coefficient decrease from 0.14 to 0.13 but this decreasing could be considered as stable. At 3000 engaging cycles the amount of worn out was 0.04 : the thickness of disc was decrease from 4.72mm to 4.68mm. But regarding the normal operation condition, further more worn-out could not be expected. Therefore concerning worn-out, the basic oil could be considered as appropriate.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.11
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• pp.1157-1162
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• 2011

The parking brake is an essential unit embedded in the track-driving motor of an excavator. The parking brake plays an important role in keeping the excavator in place not only when it is parked, but also during the digging operation. In fact, the load placed on the parking brake during the digging operation is significantly higher than the parking load, because the impact and rating loads caused by the bucket digging force cycle frequently and have very high load ranges. Therefore, the load conditions during the digging operation should be taken into account in the parking brake certification test. In this study, a series of experiments was carried out in which various operating pressures were applied to the parking brake, where repeated loads were reciprocally placed on the brake by locking the multifriction disc and releasing the hydraulic cylinder. The characteristics of the parking brake were investigated by comparing the obtained experimental results and the theoretical design specifications.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.5
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• pp.9-19
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• 1997

In this paper, the modeling and analysis of dynamic characteristics has been carried out for friction clutches and brakes in an automatic transmission. From the operating oil pressure generated by the valve-body, time delay by check valve and the movement of piston has been examined. Also torque capacity and torque transferred at the clutch is studied. Heat capacity and temperature distribution at the reaction plate of clutch are codeled by time-dependent, nonhomogeneous partial differential equation, and brake torque, brake time, and the amount of heat generated are investigated. It is found that the time delay at the check valve is very short but dominant at the spool.