Abstract: 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.

Key words: Contact stiffness, Dynamics model, Joints, Spindle system