The motorized spindle is the core component of CNC machine tools. In order to ensure its processing performance and processing safety, the temperature field of motorized spindle is studied. The three-dimensional model of the motorized spindle is established, and the convective heat transfer coefficient of the internal heat load and the simulation boundary condition are calculated by combining the heat transfer theory. The simulation is carried out by the finite element analysis software, and the internal temperature distribution of the motorized spindle under thermal steady state is calculated. Based on the numerical simulation analysis method and the thermal balance test method, the data basis for the prediction model of the motorized spindle temperature field is provided. The traditional BP neural network algorithm and PSO-BP neural network algorithm are used to predict the temperature of the motorized spindle measuring point under specific working conditions, and the temperature field prediction results are compared and analyzed. The results show that the PSO-BP neural network prediction model has good compatibility for variable data input, and the prediction results show little difference, which has high prediction accuracy and robustness.
Bearings with partial function grooves as cageless bearings related to magnetic floating bearing protection have characteristics, such as fast offsetting of the impact force caused by rotor fall, and they gradually become important parts of ultra clean and cryogenic transportation systems. However, the functional failure mechanism of the bearing, which is caused by functional groove wear, is not clear. Therefore, this paper establishes a force–motion intrinsic model of particles inside the functional groove, which is based on the discrete element method, which it itself combined with the functional groove damage evolution trend analysis. Then, a hyper-quadratic surface model of inter-particle contact is established to simulate the time-varying friction coefficient of the functional groove by combining particles of different sizes to form particle clusters. Additionally, as the boundary condition, EDEM is used to solve the contact motion state of rolling element rolling through the functional groove for one week to obtain the overlap between particles and contact force change law. The results show that the wide side of the functional groove wears more seriously than the narrow side, and the rolling element leaves the functional groove with more impact than when it enters the functional groove, and the functional groove wears more seriously. In this paper, through the study of local functional groove wear of cageless ball bearing, we propose to characterize the damage extension of functional groove by using the number of particle fracture and motion trend in discrete element method, and this study provides theoretical guidance for the design of cageless bearings.
This article presents an analysis of vibration evolution of a ball bearing without the cage. A vibration model in which time-varying displacement, time-varying stiffness, contact force and collision force are comprehensively considered, is proposed. On this basis, the law of motion of the bearing is studied. It is shown that a variable-diameter raceway affects the radius of curvature, which effects the dispersion of rolling elements. The damaged variable--diameter raceway leads to discrete failure, contact force and collision force of rolling elements, which are main reasons that cause vibration mutation. The bearing motion changes from quasi-periodic to chaotic motion.
The design and analysis of a new type of three-jaw docking mechanism capable of space rendezvous and docking are presented. In addition, a composite docking test platform capable of both vertical and horizontal docking is created. On the basis of kinematics theory, a global coordinate system is built, and the attitude error is assessed based on the error angle. On the basis of dynamic theory, the multi-body dynamic differential equation of the composite docking platform is derived, and the impact-induced interaction state of the locking pawls is studied. The simulation software is then used to jointly simulate the test platform and the docking mechanism under the two conditions of frontal and oblique docking, and to analyze the attitude law caused by the change of docking impact force. This provides a solid foundation for future research into the application of space rendezvous theory to small spacecraft.
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