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• An improved dynamic model of ball bearing is proposed. • This model considers bearing deformations and ball-inner raceway separation. • A prediction method for the initial values is applied to solve dynamic model. • The influence of deformations and ball-inner raceway separation is discussed. In actual operation conditions, the bearing deformations caused by the change of assembly state play a major role in bearing dynamic performance, and the ball-inner raceway separation due to the insufficient preload or excessive external loads is also a key issue that limits the bearing service. In this paper, an improved nonlinear dynamic model of ball bearing considering bearing deformations and ball-inner raceway separation is proposed. Firstly, the relationships between the bearing deformations and bearing-shaft assembly state are directly derived according to the deformation compatibility condition, and the interaction and relative motions among various bearing components under the ball-inner raceway separation conditions are analyzed. Then a prediction method for the initial iterative values is used to calculate the dynamic model, and the calculation results are compared with the experimental data for verification. Finally, the variations of bearing deformations, contact properties, and cage skid under different factors are investigated. It is found that the bearing deformations affect the contact properties of ball-raceway, and the appropriate preload effectively improves the bearing service characteristics, especially under the ball-inner raceway separation conditions. [ABSTRACT FROM AUTHOR]

A comprehensive dynamic model of ball bearing focusing on structure flexible deformations is developed in this paper. The cage is split into several discrete segments linked by nonlinear springs to indicate the cage flexibility. The effect of cage flexibility on cage clearance is further considered. The race flexibility generated by assembly status variation of the shaft-bearing-housing system are then deduced, and the interplay mechanism between the race and other bearing components is analyzed. Finally, the effect of structure flexible deformations on bearing dynamic properties is investigated. The results indicate that rational design for structure flexibility can optimize bearing rotary performance. • A dynamic model of ball bearing considering flexible deformations is proposed. • The effect of cage flexibility on pocket and guiding clearance is investigated. • Raceway flexible deformations due to the change of assembly state are analyzed. • The mechanism of flexible deformations on bearing dynamic performance is discussed. [ABSTRACT FROM AUTHOR]

• The dynamic transition of FCPBB's contact states was revealed under high-speed conditions. • Three-point contact state of FCPBB for specific conditions was optimized. • Eccentricity has a substantial effect on the FCPBB performance. • A smaller curvature coefficient or larger eccentricity can reduce bearing sliding. Three-point contact state is a common state for four-point contact ball bearings (FPCBB), significantly improving the performance in high-speed and light-load conditions. However, in this case, the internal contact state is in a dynamic transition between two-point and three-point contact, with substantial frictional losses. To this end, a nonlinear dynamic model of FPCBB, considering the lubrication traction and the bearing assemblies' dynamic features, is proposed to optimize the FPCBB's performance for three-point contact state. The dynamic changes of contact states under high-speed and light-load conditions are revealed, and four sets of conditions are picked as optimization conditions. Beside, groove curvature coefficient and curvature center eccentricity, depending on outer ring structure, are selected as optimized structural parameters. On this basis, the behavior performance in three-point contact state is optimized for specific operating conditions. The results show that with the gradual growth of eccentricity, the bearing fatigue life first extends slowly and then reduces rapidly, where an optimum value exists; for bearings possibly serving in skidding condition, it is better to prefer a larger eccentricity or a smaller curvature coefficient to reduce sliding damage. [Display omitted] [ABSTRACT FROM AUTHOR]

• A 5 DOFs nonlinear dynamics model of four-point contact ball bearing was proposed. • The dynamic contact feature of FCPBB with complex operating conditions were investigated. • The interaction between balls and raceway may changes from 2-point to 3-point contact with pure axial load. • The ball may experience 2-point contact, 3-point contact and 4-point contact in one revolution in case of combined loads. Four-contact-point ball bearing (FCPBB), with a special double half inner ring structure, presents dynamic multi-point contact characteristics in service. The dynamic contact feature, such as 2-point, 3-point or even 4-point contact phenomena between balls and bearing raceway, lead to completely different bearing friction, heat generation and wear rates. Considering the oil film traction effect, the traction and contact equations for ball and four raceways were proposed, and the changes of bearing dynamic contact feature with complex operating conditions, such as high speed-slight load, combined axial-radial load, were investigated. As bearing preload increases, the interaction between the ball and raceway gradually changes from 3-point to 2-point contact. In this process, the PV factor in outer sub-contact area first increases and then decreases, which is the key factor in bearing friction loss. In case of combined load, the ball may experience 2-point contact, 3-point contact and 4-point contact in one revolution. Besides, when two-point contact occurs, the main-contact area has the largest PV value; when four-point contact occurs, the sub-contact area has the largest PV value. [ABSTRACT FROM AUTHOR]