Multi-objective optimization design algorithm of dynamic and thermal performances of high speed spindle bearing
A multi-objective optimization design algorithm model for dynamic and thermal properties analysis of high speed spindle bearing is constructed. Stiffness of bearing can be obtained by solving equilibrium equations of inner ring of bearing. Heat generation of the high speed ball bearing is studied by analyzing the local friction in the bearing considering coupling of dynamic properties, a new model for evaluating bearing temperature is set up treating the contact surfaces between rolling elements and raceways as moving heat sources. Based on this model, multi-objective optimization of stiffness and temperature rising of high speed spindle bearings are studied. Pareto-optimal solution of high speed spindle bearing are given.
Nonlinear vibration and stability analysis of a flexible rotor supported on angular contact ball bearings
Flexible rotor systems supported by angular contact ball bearings display very complicated nonlinear behavior due to clearance and nonlinear Hertzian contact force. In this paper, a nonlinear vibration theoretical model for a flexible rotor-bearing system is derived in which the dynamic model of the shaft element, disk, coupling, nonlinear contact deformations and forces of the ball bearing are established. Nonlinear responses and orbits analysis of a flexible rotor angular contact ball bearing system are studied using the numerical integration method and maximal Lyapunov exponent. Bifurcation and stability of periodic motion of the flexible rotor-bearing system are studied using the continuation-shooting method and Floquet multipliers. Influences of initial contact angles, unbalance, damping factor, axial preloads, bending moments, stiffness ratio and rotating speed on stability and the bifurcation of periodic motion of the rotor-bearing system are analyzed. Finally, the theoretical model for a flexible rotor-bearing system is experimentally verified.
Experimental study on bond behavior between high-strength grout and deformed steel bars
Abstract Engineers use high-strength grout to connect precast concrete members for its low shrinkage and good fluidity. This paper designed 87 central pull-out specimens using the control variable method to investigate the influence of factors on the rebar-grout bond property such as compressive strength, steel grade, bar diameter, transverse stirrups, and bond length. The test result showed that improving grout compressive strength (85.8 MPa–122.7 MPa) cannot improve the bond strength, which was different from the previous conclusions of concrete pull-out tests. Simplified formulas were presented for calculating the characteristic values of bond strength, residual strength, peak slip, and relative slip of load-holding platform based on parameter analysis. Then, a constitutive model was proposed to predict the full-range bond stress-slip curve of high-strength grout and steel bar specimens from bearing to failure. Finally, FEA models were established to evaluate the applicability and accuracy of the constitutive model.