• Tribology and Lubricants
• /
• v.14 no.3
• /
• pp.65-73
• /
• 1998

A dynamic analysis and friction loss of non-variable swash plate compressor are studied theoretically. Rotating swash plate and reciprocating pistons are modelled kinematically, and forces and torques acting on rotor-bearing system are analyzed. Then, friction losses on 4 roller bearings, 10 sliding parts between swash plate and shoes, and 10 lubricating surfaces between cylinders and pistons are calculated. On each frictional element of sliding surfaces and roller bearings, the same friction loss is obtained, respectively.

• Earthquakes and Structures
• /
• v.16 no.6
• /
• pp.641-654
• /
• 2019

This paper investigates the seismic response of a typical non-navigable continuous girder bridge isolated with friction sliding bearings of the Hong Kong-Zhuhai-Macao link projects in China. The effectiveness of the friction pendulum system (FPS) and accuracy of the numerical model were evaluated by a 1/20 scaled bridge model using shaking table tests. Based on the hysteretic properties of friction pendulum system (FPS), double concave friction pendulum (DCFP), and triple friction pendulum system (TFPS), seismic response analyses of isolated bridges with the three sliding-type bearings are systematically carried out considering soil-pile interaction under offshore soft clay conditions. The fast nonlinear analysis (FNA) method and response spectrum are employed to investigate the seismic response of isolated offshore bridge structures. The numerical results show that the implementation of the three sliding-type bearings effectively reduce the base shear and bending moment of the reinforced concrete pier, at the cost of increasing the absolute displacement of the bridge superstructure. Furthermore, the TFPS and DCFP bearings show better isolation effect than FPS bearing for the example continuous girder bridge.

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.1016-1021
• /
• 2004

The need for developing a mathematical model for pad-pivot friction in tilting pad proceeding bearings has been well-recognized, since previous experimental work about the performances of the bearings hypothesized that the friction in the bearings is closely related to their performances. Especially, the sliding friction between pad and pivot in the ball and socket type of the bearings can influence the performance of the bearing. We propose a mathematical model for pad-pivot friction in the ball and socket type, which considers the geometrics of the pad and pivot of the bearings, by assuming the sliding friction in the ball and socket bearing as Coulomb friction. By utilizing the proposed model for pad-pivot friction, we show the analysis of Reynolds equation and energy equation, which explain the thermo-hydrodynamic characteristics of tilting pad proceeding bearings, by taking into account the turbulence and inlet pressure building as well. The results of the study show that the performance of titling-pad proceeding bearings can be greatly influenced by the pad-pivot friction. In particular, we have shown that the analysis of the pad-pivot friction is useful to explain the static proceeding loci and the dynamic characteristics of the ball and socket type of the bearings. Furthermore, for a given operating condition, we can obtain various equilibrium states which satisfy the static equilibrium conditions, by considering the pad-pivot friction.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.20 no.2
• /
• pp.125-134
• /
• 2016

In order to improve seismic safety of nuclear power plant (NPP) structures in high seismicity area, seismic isolation system can be adapted. In this study, friction pendulum system (FPS) is used as the seismic isolation system. According to Coulomb's friction theory, friction coefficient is constant regardless of bearing pressure and sliding velocity. However, friction coefficient under actual situation can be changed according to bearing pressure, sliding velocity and temperature. Seismic responses of friction pendulum system with constant friction and various velocity-dependent friction are compared. The velocity-dependent friction coefficients of FPS are varied between low-and fast-velocity friction coefficients according to sliding velocity. From the results of seismic analysis of FPS with various cases of friction coefficient, it can be observed that the yield force of FPS becomes larger as the fast-velocity friction coefficient becomes larger. Also, the displacement response of FPS becomes smaller as the fast-velocity coefficient becomes larger.

• KSTLE International Journal
• /
• v.6 no.2
• /
• pp.51-57
• /
• 2005

Surface texturing of tribological applications is an attractive technology of engineered surface. Therefore, reduction of friction is considered to be necessary for improved efficiency of machines. The current study investigated the potential of textured micro-scale grooves on bearing steel flat mated with pin-on-disk. We discuss reducing friction due to the influence of sliding direction at surface pattern. We can indicate lubrication mechanism as a Stribeck curve, which has a relationship between the friction coefficient and a dimensionless parameter for the lubrication condition. It was found that the friction coefficient was changed by the surface pattern and sliding direction, even when surface pattern was the same. It was thus verified that micro-scale grooves could affect the friction reduction considerably under mixed and hydrodynamic lubrication conditions. The lubrication regime influences the friction coefficient induced by the sliding direction of groove pattern. The friction coefficient depends on a combination of resistance force and hydrodynamic.

• International Journal of Precision Engineering and Manufacturing
• /
• v.9 no.1
• /
• pp.47-50
• /
• 2008

This paper presents a new water-lubricated hybrid sliding bearing for a high speed and high accuracy main shaft system, along with the numerical method used for its design. The porous material for the restrictor and the restriction parameter were chosen based on the special requirements of the water-lubricated bearing. Subsequent numerical calculations give the load capacity, stiffness, and friction power of different forms of water-lubricated bearings. The pressure distribution of the water film in a 6-cavity bearing is shown, based on the results of the numerical calculations. A comparison of oil-lubricated and water-lubricated bearings shows that the latter benefits more from improved processing precision and efficiency. An analysis of the stiffness and friction power results shows that 6-cavity bearings are the preferred type, due their greater stiffness and lower friction power. The average elevated temperature was calculated and found to be satisfactory. The relevant parameters of the porous restrictor were determined by calculating the restriction rate. All these results indicate that this design for a water-lubricated bearing meets specifications for high speed and high accuracy.

• Journal of Drive and Control
• /
• v.9 no.4
• /
• pp.26-31
• /
• 2012

Friction reduction between sliding hydraulic machine components is required to improve efficiency and reliability of hydraulic machineries. It is recently reported that surface texturing on sliding bearing surfaces can reduce the friction force highly. In this paper, numerical analysis is carried out to investigate the effect of dimple numbers and inlet boundary pressures on the lubrication characteristics of a parallel sliding bearing using a commercial computational fluid dynamics (CFD) code, FLUENT. The results show that the pressure distribution, load capacity, dimensionless friction force and leakage with dimple number and their locations, and inlet pressures. The overall lubrication characteristics are highly affected by dimple numbers and boundary pressure. The numerical method adopted and results can be used in design of efficient hydraulic machine components.

• Tribology and Lubricants
• /
• v.17 no.3
• /
• pp.221-227
• /
• 2001

The effect of silver particles on the sliding behavior of bearing steels was studied experimentally by using a ball-on-disk tribometer. Tests were performed in ambient air, dry air and vacuum. Disks of AISI 52100 were silver-coated by a thermal evaporation method, and the effects of silver particle transfer on friction were analyzed. In order to understand further the mechanism of silver particle transfer and its effect on friction and wear, pre-compressed silver particles were artificially introduced into the friction interface and the results were compared to those of silver-coated specimens. Results showed that the introduced silver particles produced transfer layers and resulted in low friction. It also showed that this low friction is closely related to the characteristic behavior of transfer layers. Shakedown occurred at the friction interface affected the friction and wear.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2000.11a
• /
• pp.59-66
• /
• 2000

An experimental study on the effect of silver particles on the sliding behavior of bearing steels was performed by using a ball-on-disk tribometer. Tests were carried out in ambient air, dry and vacuum. Disks of AISI 52100 were silver-coaled by a thermal evaporation method, and the effects of silver particle transfer on friction were firstly analyzed. In order to understand further the mechanism of silver particles transfer and its effect on friction and wear, pre-compressed silver particles were artificially introduced into the friction interface and the results were compared to those of silver-coated specimens. Results showed that the introduced silver particles produced transfer layers and resulted in low friction. It also showed that this low friction is closely related to the characteristic behavior of transfer layers. Shakedown and rachetting occurred at the friction interface and affected the friction and wear.

• International Journal of Precision Engineering and Manufacturing
• /
• v.1 no.1
• /
• pp.42-48
• /
• 2000

Friction in bearing exerts an important effect upon power dissipation and heat generation of spindle system. This paper presents frictional moments derived from rotational axis coordinate system of spindle and frictional characteristics to spindle speed A frictional moment of spindle bearings is derived by work-energy method. Differential sliding moments in outer raceway has a major effect upon frictional resistance; spin sliding moments in inner raceway has a secondary effect. As spindle speed increases, also the frictional moments increase. In high-speed region, ceramic ball bearing 몬 smaller frictional moment than steel ball bearing.