Stiffness Modelling and Performance Analysis of Ball Bearing Groups with Varied Configurations

Aiming at preload transfer, spatial deviation and non-uniform load distribution in multi-bearing groups of spindles, the conventional superposition of single-bearing stiffness cannot accurately reflect mechanical behaviours. Taking ball bearing groups as the research object, this paper established a preload model for back-to-back duplex bearings. The local–global displacement mapping and stiffness assembly relation between spindle and bearings are constructed. A local–global nested iterative algorithm is adopted with consideration of clearance and nonlinear ball–raceway contact-loss. Test stiffness is obtained by differentiating measured load-displacement data for model validation. Comparative analyses are conducted on stiffness, contact angle and contact load of duplex, triplex and quadruplex bearings under different configurations. The findings demonstrate that the overall stiffness of a bearing group depends on the number of bearings, their arrangement within the assembly, and the direction of the applied load. Furthermore, individual bearings do not share the load equally, and contact conditions deteriorate progressively as bearing contacts are lost in succession.