Abstract:  The rolling bearing is an important supporting part of the spindle drive system of the computer numerical control machine tool. The defects of the bearing assembly affect the performance and work efficiency of the whole computer numerical control machine tool drive system. To investigate the difference in internal dynamic characteristics of bearings under the condition of defects, the dynamic characteristics of the defective bearings were investigated with 7002C angular contact ball bearings as the research object. Firstly, the dynamic model of bearing assembly with pitting defects was constructed by using finite element simulation software. Then, the simulation results and theoretical calculation results of the ball rotation speed of the bearing at different speeds were compared. Finally, the dynamic characteristics of the defects of the outer ring, the ball, and their compound defects were comprehensively analyzed. The research results show that the shear stress of composite defects is higher than that of the single defects, and the shear stress fluctuates sharply. Different fault states show the difference in vibration signals. Ball defects show little fluctuation, outer ring defects are stable, and compound defects are the most unstable and have the largest vibration amplitude. The ball's rotational velocity exhibits irregular and inconsistent variations, and the ball defects, outer ring defects, and compound defects exhibit similar but slightly different periodicity and peak-valley delay on the velocity curve. The constructed finite element model can be used to study the dynamic characteristics of rolling bearings under different fault states and can provide some important references for the optimization design of bearings.
Key words:  rolling bearing; compound defect bearing; display dynamics algorithm; internal dynamic characteristics; shear stress characteristics; vibration characteristics; motion characteristic