• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.303-304
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• 2002

This paper presents theoretical analysis of the NRRO(the non-repeatable run-out) for a ball bearing with geometric imperfection. This imperfection contains ball size error, ball waviness, outer race waviness and inner race waviness. The 3D dynamic analysis of a ball bearing using the Newton-Raphson method is performed to calculate the displacement of shaft center. The radial and axial NRRO are simulated, and preload and clearance effects are investigated. Preload and clearance have significant effects on radial and axial NRRO of for miniature ball bearings.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.585-591
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• 2003

It has been widely known that geometrical or form errors of ball bearings such as ball size error, ball waviness, inner and outer race waviness due to inherent manufacturing imperfection are one of the major sources of uncontrollable non-repeatable run-out (NRRO) vibration in HDD spindle motor. NRRO in HDD is also known to be the primary cause of limiting the storage capacity of HDD. In this paper, We performed vibration analysis for NRRO a ball bearing being used in 3.5" HDD spindle motor. To theoretically estimate NRRO considering the geometrical errors of ball bearing components, a simple three degrees of freedom model was proposed and then vibration analysis for axial and radial NRRO was conducted utilizing the measured geometric imperfection of a bearing with both the waviness magnitude and phase taken into account. Effects of bearing preload and clearance on NRRO was also investigated as an effort to predict their optimum values minimizing bearing NRRO.

• Design & Manufacturing
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• 제6권1호
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• pp.45-51
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• 2012

The main goal of this paper is to establish an interference tolerance for determining optimal amount of clearance in the shaft-bearing system supported by radial ball bearings. The 2-D frictional contact model was employed for the FE analysis between the shaft and the inner raceway. Several examples were simulated using different material properties for the solid shaft. Efforts were focused on the deformation applied in the radial direction to select suitable bearings. The analysis results showed that the initial axial preload applied on the bearings plays a significant role to reduce bearing fatigue life. The proposed design parameters obtained by numerical simulations can approximately predict a rate of bearing life reduction as a function of shaft diameter ratio. This analysis can also be used to calculate the optimal initial radial clearance in order to obtain a shaft-bearing system design for high accuracy and long life.

• 대한기계학회논문집A
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• 제40권5호
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• pp.489-495
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• 2016

기어 맞물림 동적 힘은 축과 베어링을 통해 하우징에 전달되어 소음으로 발생하므로, 베어링 강성은 하우징의 최종 전달자로서 기어 소음을 제어하는데 중요한 역할을 한다. 이 논문은 스퍼기어를 위한 볼 베어링의 강성을 유도하고, 베어링 하중과 반경 방향 틈새를 고려하여 강성을 계산하였다. 그 강성을 이용하여 3 자유도 모델의 스퍼기어계의 운동방정식에 적용하여 모드 특성을 해석하였고, 유한요소법으로 검증하였다. 그 결과 베어링 하중이 클 때보다 작을 때는 틈새에 따라 베어링 강성의 변화가 많았다. 베어링 강성은 저주파 고유 진동수에 영향을 주었고 기어 맞물림 주파수는 고주파 고유진동수에 영향을 주었다.

• Tribology and Lubricants
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• 제35권3호
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• pp.158-168
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• 2019

This paper presents the investigation of two types of rotordynamic modeling issues for 2.2 kW-class, rated speed of 1,800 rpm, squirrel-cage type induction motors. These issues include the lamination structure of rotor cores, and the radial clearance of ball bearings that support the shaft of the motor. Firstly, we focus on identifying the effects of rotor core lamination on the rotordynamic analysis via a 2D prediction model. The influence of lamination is considered as the change in the elastic modulus of the rotor core, which is determined by a modification factor ranging from 0 to 1.0. The analysis results show that the unbalanced response of the rotor-bearing system significantly varies depending on the value of the modification factor. Through modal testing of the system, the modification factor of 0.079 is proven to be appropriate to consider the effects of lamination. Next, we investigate the influence of ball bearing clearance on the rotordynamic analysis by establishing a bearing analysis model based on Hertz's contact theory. The analysis results indicate that negative clearance greatly changes the bearing static behavior. Rotordynamic analysis using predicted bearing stiffness with various clearances from -0.005 mm to 0.010 mm reveals that variations in clearance result in a slight difference in the displacement of the system up to 18.18. Thus, considering lamination in rotordynamic analysis is necessary as it can cause serious analysis errors in unbalanced response. However, considering the effect of the bearing clearance is optional because of its relatively weak impact.

• 한국자동차공학회논문집
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• 제15권5호
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• pp.160-164
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• 2007

An automotive wheel bearing is one of the most important components to guarantee the service life of a passenger car. The endurance life of a bearing is affected by many parameters such as material properties, heat treatment, lubrication conditions, temperature, loading conditions, bearing geometry, internal clearance and so on. Generally, a tapered roller bearing gives longer endurance life than that of an equivalent size ball bearing. Consequently, the application of taper bearing units will be increased for more compact design and extended warranty. In this paper, we derive the relation between loads and deformations of a taper bearing unit. On the basis of that, we calculate the endurance life of the taper bearing unit considering initial axial clearance.

• 한국정밀공학회지
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• 제26권5호
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• pp.135-141
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• 2009

The bearing clearance is influenced by shrink fit and thermal expansion during operation. The designer must take into account the reduction of clearance after installation to the interference fits, and thermal expansion must be considered. The purpose of this study is to grasp the internal clearance variation and behavior of a bearing which is a deep connected with fatigue life of bearing and performance of spindle through FEM(Finite Element Method). Finite element analysis is performed by using commercial code ANSYS according to variation of thermal condition and rotational speeds. This paper presents correct negative internal clearance according to temperature during operation. Furthermore, interrelation between thermal expansion and contraction are presented to maintain adequate contact force for three type of spindle system (HSK-A60, HSK-40E, HSK-32E). The influence of the centrifugal force and Internal clearance variation of bearing is studied to operating rotational speed.

• 한국정밀공학회지
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• 제27권9호
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• pp.94-102
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• 2010

The spindle is the main component in machine tools. To develop high speed machine tools, a lot of studies have been carried out for high speed spindle. Bearing is very important part in spindle. The bearing clearance is influenced by shrink fit and thermal expansion during operation. The designer must take into account the reduction of shrink fits. The aims of this study are to grasp the shrink fits and behavior of a bearing which is a deeply connected with fatigue life of bearing and performance of spindle through FEM(Finite Element Method). This paper proposed optimum value of shrink fit considering deformation of spindle and stress of fitting area using design of experiments. Thus, the proposed formula can be used to obtain bearing internal clearance.

• Tribology and Lubricants
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• 제13권3호
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• pp.48-55
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• 1997

The ball bearing with thin-section raceways which is much lighter than other conventional bearings used in most modem passenger cars and small tracks. The important design parameters of this bearing is the groove radius of raceways, the diametral clearance, the free contact angle and so on. The optimal value of these parameters were determined by considering the dynamic load capacity, the contact angle and the calculated fatigue life. The contact angle between a ball and raceways was calculated by considering the local contact deformation and the structural deformation of thin-section raceways which was estimated by FEM. The raceways were made by means of the press-forming process. The fatigue life tester was designed and manufactured. The fatigue life test was executed and the reliability of this bearing was confirmed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 추계학술대회 논문집
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• pp.241-242
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• 2006