• Tribology and Lubricants
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• 제27권5호
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• pp.240-248
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• 2011

Mechanical face seal installed in primary heat transport pump used for heavy water reactor prevents leakage of working fluid using thin working fluid film between primary seal ring and mating ring. If the leakage of working fluid exceeds the allowable volume, serious accident can be happened by the trouble of primary heat transport pump. The thinner fluid film exists between primary seal ring and mating ring, the less working fluid leaks out. On the other hand, if the thickness of fluid film is not enough, the life of mechanical face seal will be reduced by friction and wear. Therefore appropriate design is necessary to maximize the performance and life of mechanical face seal. In this study, numerical analysis using finite volume method was conducted to investigate the performance of mechanical face seals which have same deep straight groove and 11 different net coning values. As results, equilibrium clearance between primary seal ring and mating ring, leakage volume of working fluid, friction torque on sealing surface and stiffness of working fluid film were obtained. With increasing net coning value, equilibrium clearance and leakage volume increase, and friction torque and stiffness of fluid film decrease.

• Journal of Mechanical Science and Technology
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• 제15권6호
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• pp.685-692
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• 2001

This paper reports on the mixed lubrication characteristics between the cam and the tappet contact surface of direct acting type valve train systems. First, the dynamic characteristics are solved by using the lumped mass method to determine the load conditions at the contact point. Then, the minimum oil film thickness is calculated with consideration of elastohydrodynamic line contact theory and the friction force is obtained by using the mixed lubrication model which separates the hydrodynamic and the boundary friction. Finally, the average surface temperatures are calculated by using the flash temperature theory. The results show that, there are some peaks in the friction force due to the asperity contact friction, and flash temperature at the position of minimum oil film thickness. It is thought that there is a relationship between the surface temperature and cam surface wear, and therefore, the analysis on the worn cam profile has been performed.

• Transactions of the Korean Society of Mechanical Engineers
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• 제19권6호
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• pp.1479-1489
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• 1995

In this study, tensile strength and modulus were evaluated for a filament wound ring specimen by split disk test and compared with the theoretical values obtained by the rule of mixtures. The circumferentially wound ring specimens were prepared from 4 types of material systems. The results showed that the measured strengths of the composite systems were considerably lower than the theoretical values due to the local bending stresses around the split disk edges. for the measurement of elastic moduli of the filament wound ring specimens, the effect of friction on the strain of the ring must be taken into account. But the effect of friction between the split disk fixture and the ring specimen can be eliminated by averaging the moduli for loading and unloading state with maintaining the same crosshead rates. The measured elastic moduli of ring specimens showed very good agreement with the theoretical values.

• Journal of Institute of Control, Robotics and Systems
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• 제17권9호
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• pp.863-868
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• 2011

This paper presents a method to achieve a synchronous positioning objective for a dual-cylinder electro-hydraulic system with friction characteristics. The control system consists of a VSC (Variable Structure Controller) for each of the hydraulic cylinders and a PID (Proportional-Integral-Derivative) feedback controller. The PID controller is used for controlling the non-synchronous error generated by both cylinders when motion synchronization is carried out. To enhance the position-tracking performance of the individual cylinders friction characteristics is modeled in model, based on the estimated friction force. The simulation and experimental results show that the proposed method can effectively achieve the objective of position synchronization in the dualcylinder electro-hydraulic system, with maximum synchronization error with ${\pm}2\;mm$.

• Tribology and Lubricants
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• 제33권3호
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• pp.92-97
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• 2017

The understanding of the friction characteristics of micro-textured surface is of great importance to enhance the tribological properties of nano- and micro-devices. We fabricate rectangular patterns with submicron-scale structures on a Si wafer surface with various pitches and heights by using a focused ion beam (FIB). In addition, we fabricate tilted rectangular patterns to identify the influence of the tilt angle ($45^{\circ}$ and $135^{\circ}$) on friction behaviour. We perform the friction test using lateral force microscopy (LFM) employing a colloidal probe. We fabricate the colloidal probe by attaching a $10{\pm}1-{\mu}m$-diameter borosilicate glass sphere to a tipless silicon cantilever by using a ultraviolet cure adhesive. The applied normal loads range between 200 nN and 1100 nN and the sliding speed was set to $12{\mu}m/s$. The test results show that the friction behavior varied depending on the pitch, height, and tilt angle of the microstructure. The friction forces were relatively lower for narrower and deeper pitches. The comparison of friction force between the sub-micro-structured surfaces and the original Si surface indicate an improvement of the friction property at a low load range. The current study provides a better understanding of the influence of pitch, height, and tilt angle of the microstructure on their tribological properties, enabling the design of sub-micro- and micro-structured Si surfaces to improve their mechanical durability.

• Journal of Mechanical Science and Technology
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• 제19권spc1호
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• pp.403-410
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• 2005

Many daily appliances for examples copiers, printers and ATMs contain the media transport system (MTS) and the slippage between the medium in the MTS deteriorates the performance quality of the whole system. The slippage of the medium in the MTS is affected by many parameters including the friction coefficient between the feeding rollers and the medium, the velocity of the feeding rollers, and the normal force exerted on the medium by feeding rollers. This paper focuses on the effect of the normal force on the slippage while the medium is being fed. For this purpose, we developed a two-dimensional simulation model for a paper feeding system. Using the simulation model, we calculated the slippage of the paper for different normal forces. We have also constructed a testbed of the paper feeding system to verify the simulation results. Experimental results are compared with the simulation results.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.205-211
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• 2000

Friction control is highly desirable for optimization of tribological systems. In this work, the effect of geometric structure of the solid surface on friction is investigated using a Scanning Electron Microscope equipped with a tribotester. Silicon and silicon oxide specimens were used and undulations on the surface were fabricated by mechanical and chemical methods. It is shown that the friction coefficient depends on the relative dimensions of the ball and the width of undualation. By optimizing the geometry of the undulation, friction reduction may be achieved.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제21권3호
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• pp.140-148
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• 2009

Capillary tubes are widely used as expansion device in small refrigeration systems. The refrigerant flowing in the capillary tube experiences frictional and accelerational head losses and flashing simultaneously. In this paper flow characteristics of adiabatic capillary tubes were simulated with various friction factor models, two-phase viscosity models, and two-phase frictional multiplier models. The predicted pressure distribution and mass flow rate are compared with experimental data reported in literature. It is confirmed that the predicting accuracy with homogeneous model can be improved by employing suitable correlations of friction factor, two-phase viscosity and two-phase frictional multiplier.

• Tribology and Lubricants
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• 제35권1호
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• pp.30-36
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• 2019

The tribological properties of paper-based friction materials are crucial to the performance of a wet clutch system. In this work, the friction and wear characteristics of a paper-based friction material in boundary lubrication state was experimentally investigated using a pin-on-reciprocating tribotester under various normal forces and temperatures. It was found that the wear rate of the friction material increased from $5.8{\times}10^{-6}mm^3/N/cycle$ to $5.5{\times}10^{-5}mm^3/N/cycle$ after 1,700 cycles of testing at $80^{\circ}C$ as normal force increased from 2 N to 7 N. The friction coefficient was also found to increase from 0.135 to 0.155 with increasing normal force from 2 N to 7 N. The increase in contact pressure with increasing normal force may be responsible for these results. In addition, as temperature increased from $20^{\circ}C$ to $80^{\circ}C$, the wear rate of the friction materials increased from $2.0{\times}10^{-5}mm^3/N/cycle$ to $3.6{\times}10^{-5}mm^3/N/cycle$ while the friction coefficient decreased from 0.163 to 0.146. This result may be associated with the decrease in the hardness of friction materials with increasing temperature. Furthermore, plastic deformation on the friction materials was mainly observed after the test. The outcome of this work may be useful to gain a better understanding of the tribological properties of friction materials, and therefore can contribute to the development of friction materials with enhanced performance for wet clutch systems.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.439-443
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• 2004

In this research, we describe the sorting conditions modeling by friction force. As in any mechanism which is required to provide good dynamic performance and high accuracy, performance evaluation of optimal control. To understand friction it is necessary to investigate the topography of the sliding surfaces in contact. Any surfaces, even apparently smooth surfaces, are microscopically rough. When two surfaces come into contact, the true contact takes place only at point where asperities come together. The sorting conditions of sorting mechanism with friction force is sorting force must be equal with force can sorting one highest veneer among loaded veneer. This is just a thing being sorted veneer have friction with under veneer and this friction disturb sorting at the same time. Hence, the sorting conditions evaluation is important to sorting one veneer must get under control friction with veneer.