Quantification of Amplitude- and Rotation Speed-Dependent Nonlinearity of Machine Tool Spindles

Stiffness of spindles, which are high-speed rotors, has to be determined accurately for precision metal cutting. Dependence of rotor natural frequencies and damping on both amplitude and rotation speed is studied experimentally. The spindle shaft is excited using a noncontact electromagnetic exciter: the excitation suddenly stops for free vibration after the response reaches steady state. The peak finding and picking (PFF) method is used to determine the amplitude-dependent natural frequency and damping. It is found that the nonlinearity trends obtained from different excitation methods are similar.