Nonlinear Dynamics of Thermal Flying Height Control Sliders at Touch-Down

The touch-down test is widely used to calibrate the flying-height (FH) of sliders by gently contacting the disk with the thermal protrusion of thermal FH control (TFC) sliders. However, the dynamic instability of TFC slider during the touch-down process may significantly affect the contact detection and the FH calibration, and therefore, hinders further reduction of the FH of TFC sliders. This paper highlights the nonlinear dynamics perspectives on the instability of TFC sliders during the touch-down process. A single-DOF (degree-of-freedom) and a 2-DOF nonlinear dynamics models were developed respectively to quantitatively study instability of TFC sliders at the near contact regime and to explain the nonlinear dynamic behaviors of TFC sliders at touch-down. The simulation results from the nonlinear analytical models reveal that the existence of multiple equilibriums and the self-excited vibrations of the slider-air bearing system are the main reasons for the instability and bouncing of TFC sliders during touch-down process.