高速主轴动力学建模及速度效应分析

考虑高速旋转部件的离心力和陀螺力矩效应,利用Timoshenko梁单元和转盘单元建立主轴转子、转盘、主轴箱等部件有限元模型,并对Jones轴承模型进行扩展建立高速滚动轴承非线性模型。将各子部件模型进行集成,得到整个高速主轴系统的非线性动力学方程,并进行试验验证。分别从转子陀螺力矩、转子离心力和轴承软化这三个角度,系统地研究高速旋转状态下主轴-轴承系统内部的速度效应及其对整个系统动态特性的影响规律。结果表明:当系统存在较大的阻尼比(1%~5%)时,陀螺力矩对系统的直接频率响应函数影响不明显,但是对交叉传递函数的影响显著;随着主轴转速的升高,主轴转子的离心力效应会逐渐削弱主轴系统的刚度,最终使整个高速主轴系统的固有频率降低;必须综合考虑主轴转子的离心力效应和轴承的软化效应,才能比较准确地仿真高速主轴系统的动力学特性。

Dynamic modeling of high-speed spindles and analysis of speed effects

With consideration of the centrifugal force and the gyroscopic moments for the rotating components with high speed,the Timoshenko beam element and disk element are used to model the spindle rotor,disk and the spindle housing.The Jones’ bearing model is extended and a nonlinear model for high-speed bearings is obtained.By assembling the model of each component,the nonlinear dynamic equation of the whole spindle system is given with experimental validation.The speed effects within the spindle-bearing system and their influences on the dynamic properties of the whole system are studied systematically from three aspects,i.e.,gyroscopic moment of the rotor,centrifugal force of the rotor,and bearing softening.The results show that,when the damping ratio is relatively large(1%～5%),the gyroscopic moment can hardly affect the direct transfer function,but can change the cross transfer function obviously;with the rise of the spindle speed,the centrifugal effect of the spindle rotor decreases the stiffness of the spindle system gradually,which causes the drop of the natural frequencies of the high-speed spindle system;the centrifugal force’s effect of the spindle rotor and bearings’ softening effect need to be included synthetically so as to accurately simulate the dynamic properties of the high-speed spindle system.