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This paper takes the ball diameter difference into consideration in the nonlinear dynamic model of the full ceramic bearing. The interactions between the elements of the bearing are derived based on the dynamic theory of the rolling bearing. The sound radiation is obtained using the sub-source decomposition method, and a verification experiment is carried out on the motorized spindle test rig to assess the precision of the model. The rotation speed, axial preload and radial loads are selected as influence factors, and parametric investigations are conducted to study the impact of the factors on the interactions between the elements. The circumferential distributions of the sound radiation are investigated, and parameters including sound pressure level and peak directivity angle are taken as evaluation indexes. Results show that the ball diameter difference has significant impact on the sound radiation of full ceramic bearings, and the impact grows with rotation speed. The sound directivity is closely related to the forces acting on the inner ring, and is affected by the axial and radial loads in different ways. This study provides information for the bearing acoustic characteristics, and is relevant for the design and operation of ceramic bearings.

In this paper, a method for recognizing the crack location on the outer ring of the full ceramic bearing is proposed, which considers the transmission of the vibration signal on the outer ring when a crack occurs. A two-degree-of-freedom nonlinear dynamic model of the full ceramic bearing with a crack is established, and the impact of the crack is evaluated through the change of the strain energy. Then, considering the attenuation of the vibration signal along the outer ring, the dynamic model is improved with a time-varying stiffness related with the crack position. By analyzing the ratio of the synchronous root mean square difference of the vibration signal, the position of the outer ring crack is recognized. The simulation results are compared with the experimental results to verify the accuracy and feasibility of the position recognition method. The research provides a new recognition method for bearing fault location, and helps with the fault diagnosis and status monitoring of bearing systems.

This paper mainly focuses on the calculation and analysis on the radiation noise of the angular contact ball bearing applied to the ceramic motorized spindle. The dynamic model containing the main working conditions and structural parameters is established based on dynamic theory of rolling bearing. The sub-source decomposition method is introduced in for the calculation of the radiation noise of the bearing, and a comparative experiment is adopted to check the precision of the method. Then the comparison between the contribution of different components is carried out in frequency domain based on the sub-source decomposition method. The spectrum of radiation noise of different components under various rotation speeds are used as the basis of assessing the contribution of different eigenfrequencies on the radiation noise of the components, and the proportion of friction noise and impact noise is evaluated as well. The results of the research provide the theoretical basis for the calculation of bearing noise, and offers reference to the impact of different components on the radiation noise of the bearing under different rotation speed.

Radiation noise (RN) is an important parameter for representing the characteristics of a bearing. By simplifying a ball bearing as a mass–spring–damping system, the differential equations for the vibration of an angular contact ceramic ball bearing (ACCBB) are established from the view of energy conservation considering nonlinear contact stiffness and damping. Then, the RN model of the bearing is constructed by Helmholtz's acoustic theory. The bearing noise is calculated using the proposed model, and the corresponding experiments are performed to confirm the model precision. The bearing noise consists of the noise at the characteristic frequency of each component; the rotational frequency is the primary contributor to the bearing noise. The radiation noise first increases with increasing rotational speed and the sound pressure level (SPL) has a high peak value at a critical speed of 28,000 r·min−1. Then, the noise decreases with increasing rotational speed. The directivity of sound field is discussed at different rotational speed. With increasing the rotational speed, the directivity level (DL) increases and the directivity angle (DA) skews towards the rotation direction. The research provides a theoretical basis to analyze the RN generated by ACCBBs at different rotational speeds.

The effect of ball diameter difference is quite obvious in full ceramic bearings due to the great stiffness, and leads to the problem of uneven loading in starved lubricated conditions. This paper takes the uneven loading condition into consideration in the dynamic model, and a verification experiment is carried out for the assessment of calculation accuracy. The factors of ball diameter tolerance, the arrangements of balls and the number of balls have impact on the interactions between the inner ring and the loaded balls, and the trends of sound radiation are studied in depth. The amplitude of sound radiation is used to show the interaction between the elements, and uneven loading conditions can be evaluated by the sound directivity. Results show that the tolerance is a key factor that has impact on the sound radiation, and the sound radiation and directivity have obvious change with the ball diameter tolerance. The arrangements of balls have impact on the sound radiation by changing the diameter difference between adjacent balls, and the loaded area of each loaded ball varies with the number of balls. The cases with different numbers of loaded balls are discussed, and the relations between the uneven loading conditions and sound radiation are investigated. This study proposes a method for the study of uneven loading conditions, and provides theoretical basis for the optimal design of full ceramic bearings.