主轴转子系统动力学解析建模方法

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Traditionally, the contact stiffness and damping of the spindle rotor system dynamics model are often identified by modal test, but the experimental recognition method is not universal. So, a new analytical modeling method for system dynamics is proposed, which can consider the real contact characteristics of joints such as tool-tong hold, tong hold-holder and holder-spindle. The relationships between contact stiffness and clamping force, structure parameters of contact surfaces are established by calculating the forces of each substructure. Due to the axial, radial and bending deformation of the rotor system, equispaced spring-damper units with two nodes and six degrees of freedom are put forward to simulate the dynamics of joints. Then the dynamic model of tool-holder-spindle rotor system is developed by integrating dynamics equation parameters of components and joints. The impact tests are also performed on the tool-BT40 tool holder-spindle assembly. The experimental results showed that the maximal error of the first three natural frequencies of the system between simulation and test is 21.7% when taking joints as rigid constraint, while the maximal error is only 4.8% when treating joints as flexible constraint. In addition, the predicted frequency response function of tool tip can reach a more acceptable accuracy with measurement using the flexible contact model, which also validates the presented analytical modeling method.传统上主轴转子系统动力学模型中的结合部接触刚度和阻尼系数常通过试验识别的方法来获取,针时该方法通用性差的特点,提出一种可以考虑刀具-夹套、夹套-刀柄以及刀柄-主轴结合部接触特性的主轴转子系统动力学解析建模方法。通过对各联接部件的受力分析,建立结合面接触刚度与各结合部夹紧力和几何参数间的影响关系;考虑到转子系统的轴向、径向和弯曲变形,采用均布2节点6自由度的弹簧-阻尼单元来建立结合部动力学模型;通过综合系统各部件和结合部的动力学方程参数,建立起主轴转子系统的动力学模型。以刀具-BT40刀柄-主轴为对象,进行模态测试。试验结果表明,结合部刚性处理时,系统的前三阶固有频率与试验值最大误差为21.7;而结合部柔性处理时,系统前三阶固有频率与试验值最大误差降为4.8,并且根据模型计算得出的刀尖点频响函数与试验测试能更好地吻合,验证了该建模方法的准确性。