No abstract

Thermal errors of motorized spindle are of great importance to affect final machining precision of CNC machine tool. Thermal characteristics simulation analysis of motorized spindle is realized by ANSYS; thermal errors test measurement is completed based on 5-point method; and prediction models of thermal errors are constructed by multiple linear regression (MLR) method, Back Propagation (BP) neural network method and Radial Basis Function (RBF) neural network method respectively. The results of simulation and experiments illustrate that simulation results can represent thermal characteristics of motorized spindle, whose degree of confidence mainly depending on setting of thermal load and boundary conditions properly or not; RBF neural network model has highest prediction precision for thermal errors of motorized spindle based on test data.

Based on RANS method, this paper studied leading-edge tubercle three-dimensional airfoil, which had effect on hydrodynamic performance of three-dimensional airfoil. Both section configurations of the two three-dimensional airfoil models were NACA0020 airfoil. The research method was numerical simulation. First, the leading-edge profile of the first airfoil model was normal. To get stalling angle of the first model, it analyzed hydrodynamic performance of the first model under different angle of attacks at Re=1.35*105. Then, the second model had a sinusoidal leading-edge profile. The second model chose the same Reynolds number. By comparison the numerical calculation results between the first and the second model, the stalling angle of second model delays 3°than the normal airfoil, and the lift coefficient of the second model increases 11.92% than the normal model. The results have laid the foundation for optimization design of leading-edge tubercle three-dimensional airfoil.

In the high speed precision machine tools, the thermal deformation of spindle had an important influence in machining accuracy. The data of thermal deformation of spindle was got through measuring test rod in the experiment. However, the system error existing of test rod in running and heat imported led to the difference between the measured values and the actual values. The paper has discussed the deformation of test rod caused by centrifugal force in high speed, Non-uniform thermal field in a stable state, and gravity and the variational elastic modulus. Through analyzing those factors, the main ones and neglectable ones could be confirmed, which laid the theoretical foundation in order to eliminate the interference factors in the measurement values.

The flow-induced vibration of a two-degree-of-freedom cylinder near a free surface at low Reynolds number (Re = 200) is numerically investigated using the lattice Boltzmann method and a free-surface model. The effects of the Froude number and submergence depth on the characteristics of the flow field and cylinder vibration are discussed. With the approach of the free surface, the wake behind the cylinder interacts with the free surface, resulting in a switch in the vortex shedding mode and the fluctuation of the free surface, which in turn affects the vibration of the cylinder. Additionally, a decrease in the normalized submergence depth h ∗ results in a decrease in the transverse amplitude of vibration and an increase in the streamwise amplitude. The topology of the cylinder vibration trajectory changes from a curve of eight to a teardrop, half-moon, or ellipse shape and gradually loses symmetry. Seven characteristic parameters are extracted from the trajectory of the cylinder, among which the amplitude of the vibration frequency and the phase difference of the vibration in different directions mainly affect the symmetry and topological structure of the trajectory.