• Tribology and Lubricants
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• v.8 no.2
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• pp.64-72
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• 1992

The recent trends of rotating machinery demand high speed and high temperature operation, and the bearing with new material is required to be developed. Ceramic, especially silicon nitride, have been receiving attention as alternative material to conventional bearing steel. Ceramic ball bearing offers major performance advantages over steel bearing, for instance, high speed, maginal lubrication, high temperature, improved corrosion resistance and nonmagnetic capabilities etc.. In this paper, the mechanical characteristics of ceramic ball bearing (hybrid ceramic bearing and all ceramic bearing) were investigated, and the characteristics of ceramic bearing were compared with that of steel bearing. Deep groove ball bearing 6208 was taken the object of analysis. The main results of analysis were followings: the radial stiffness of hybrid and all ceramic bearing were 112% and 130% that of steel bearing, and the axial stiffness of all ceramic bearing was 110% that of steel bearing. According as rotating speed was up, the ball load, the contact angle, the contact stress and the spin-to-roll ratio between ball and raceway of ceramic bearing were far smaller than these of steel bearing. And there was not a significant difference between the minimum film thickness of ceramic bearing and steel bearing. It is expected that this research is contributed to enhanced fundamental technology for the practical applications of ceramic ball bearing.

• Tribology and Lubricants
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• v.14 no.2
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• pp.26-34
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• 1998

This paper presents a high-speed performance analysis of ball bearings with ceramic balls under thrust loads. The sliding velocity profiles between a ball and raceways were obtained by the 3-D quasi-dynamic equations of motion including both centrifugal force and gyroscopic moment derived by vector matrix algebra. The friction at the contact areas was obtained by the Bair-Winer's non-Newtonian rheological model and the Hamrock-Dowson's central film thickness in EHL analysis. The nonlinear equations were solved by the Newton-Raphson method and the underrelaxation iterative method. The friction torques and ball behaviors with various loads, ball materials, and contact angles were predicted by this model. It was shown that the friction torque was sensitive to thrust load and contact angle, and that the friction torque and the pitch angle of the bearing with ceramic balls are smaller than those of the bearing with steel balls.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.2
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• pp.96-101
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• 2001

This paper shows the temperature characteristics of a high speed angular contact ball gearing which is 7004C type with ISO P2 tolerance class. A built-in motor type high speed spindle which adopts an oil-air lubrication system was used to measure the temperature rise up to 60,000rpm. The gearing temperature was measured using thermocouples that were attached to the outside surfaces of the outer rings. The result showed that the continuous test method which was suggested in this paper is more effective than on and off method and the lubrication oil supply rate should be reduced in high speed rolling bearings as long as the seizure does not occur. And the result were confirmed that the bearings packed with ceramic balls are superior to those with steel balls in temperature characteristics.

• Journal of the Korean Ceramic Society
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• v.45 no.9
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• pp.507-511
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• 2008

A "C-sphere" specimen geometry was used to determine the failure strength distributions of a commercially-available bearing-grade silicon nitride ($Si_3N_4$) with ball diameters of 12.7 and 25.4 mm. Strengths for both diameters were determined using the combination of failure load, C-sphere geometry, and finite element analysis and fitted using two-parameter Weibull distributions. Effective areas of both diameters were estimated as a function of Weibull modulus and used to explore whether the strength distributions predictably scaled between each size. They did not. That statistical observation suggested that the same flaw type did not limit the strength of both ball diameters indicating a lack of material homogeneity between the two sizes. Optical fractography confirmed that. It showed there were two distinct strength-limiting flaw types common to both ball diameters, that one flaw type was always associated with lower strength specimens, and that a significantly higher fraction of the 25.4-mm-diameter C-sphere specimens failed from it. Predictable strength-size-scaling would therefore not result as a consequence of this because these flaw types were not homogenously distributed and sampled in both C-sphere geometries.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.545-553
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• 1998

Recently a new process known as the magnetic fluid grinding has been developed, which can remove material from the surface of ceramic balls by fifty to one hundred times more rapidly than the conventional lapping process. In this study, the ceramic balls with various compositions are made and ground by using the magnetic fluid grinding technique with various machining parameters. In order to make well-round shaped balls by using the magnetic fluid grinding technique, the fundamental research to find out the machining factors has been carried out. Developing an equipment with higher efficiency and reliability in the machining could certainly lead to the higher productivity with excellent quality of ceramic balls.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.567-570
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• 2003

In recent years, the demand of mobile device, such as digital camera, camcorder and PDA, increases remarkably. So, requirements of the mobile information data storage used in the mobile devices increase noticeably also. 1" micro data storage is a kind of mobile storage. which has a CF type II form factor, and the similar structure of the general 3.5" HDD. In this paper, we developed the self acting air-lubricated ceramic bearing for the 1" micro data storage. The self acting air-lubricated ceramic bearing Is superior to the fluid bearing and the ball bearing on power consumption.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.841-845
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• 1995

In this study, a motor-integrated high-speed spindle system with .psi. 65mm*25,000rpm is developed by introducing the oil-jet lubrication method,ceramic angular contact ball bearing, a built-in motor and so on. And oil-jet lubrication experiments for evaluating the system performance are performed under various operation conditions. Especially, in order to establish the oil-jet lubrication conditions related to the development of a high-speed spindle system, the effects of oil supply rate and rotational spindle speed are investigated on the temperature rise, temperature distribution,motor current and so on.

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

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.326-333
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• 2004

This paper presents the structural characteristics analysis of a high-speed horizontal machining center with spindle speed of 50, 000rpm and feedrate of 120m/min. The spindle system is designed based on the built-in motor, angular contact ceramic ball bearings, oil-air lubrication and oil-jacket cooling method. The X-axis and Y-axis feeding systems are composed of the linear motor and linear motion guides, and the Z-axis feeding system is composed of the servo-motor, ball screw and linear motion guide. The structural analysis model of the high-speed horizontal machining center is constructed by the finite element method, and the validity of structural design is estimated based on the structural deformation of the high-speed horizontal machining center and spindle nose caused by the gravity and inertia forces.

• Tribology and Lubricants
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• v.34 no.1
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• pp.9-15
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• 2018

Modern high-performance automotive turbochargers (TCs) implement ceramic hybrid angular contact ball bearings in series with squeeze film dampers (SFDs) to enhance transient responses, thereby reducing the overall emission levels. The current study predicts the rotordynamic responses of the commercial automotive TCs (compressor wheel diameter = ~53 mm, turbine wheel diameter = ~43 mm, and shaft diameter at the bearing locations = ~7 mm) supported on ball bearings and SFDs for various design parameters of SFDs, including radial clearance, axial length, lubricant viscosity, and rotor imbalance conditions (i.e., amplitudes and phase angles) while increasing rotor speed up to 150 krpm. This study validates the predictive rotor finite element model against measurements of mass, polar and transverse moments of inertia, and free-free mode natural frequencies and mode shapes. A nonlinear rotordynamic model integrates nonlinear force coefficients of SFDs to calculate the transient responses of the TC rotor-bearing system. The predicted results show that SFD radial clearances, as well as phase angles of rotor imbalances, have the paramount effect on the dynamic responses of TC shaft motions.