Numerical and experimental investigation of the load/unload behavior of subambient pressure hard disk drive sliders

In this dissertation, a numerical and experimental investigation of the load/unload (L/UL) behavior of two different subambient pressure type sliders used in magnetic hard disk drives is presented. Load/unload is a technique used in hard disk drives where the suspension that carries the slider moves onto a ramp located at the outer disk diameter before the disk drive is turned off, thereby “unloading” the slider from the disk surface. In the ideal case, contact between slider and disk is completely prevented.; In order to simulate load/unload numerically, a dynamic air bearing simulator based on the Finite Element Method (FEM) is developed. The simulator is capable of solving the Reynolds equation for bearing numbers on the order of 10 6 and for arbitrary slider geometry. The air bearing simulator employs the implicit trapezoidal rule for time-stepping and is coupled with a new suspension beam model that simulates the motion of the suspension on the ramp. Different suspension states are included in the model using additional rod elements. The suspension beam model is an improvement over previously proposed approaches to model the slider/suspension dynamics, since it automatically includes suspension inertia effects and also provides coupling between the vertical motion and the pitch motion of the slider. Using the coupled air bearing/suspension simulator, the load/unload behavior of two different slider types is investigated as a function of vertical speed, slider static attitude, and dimple preload.; For the experimental investigations, Laser Doppler vibrometry (LDV) is used together with Acoustic Emission (AE) measurements. A periscope is designed that enables the positioning of the laser spot of the LDV on the slider air bearing surface during the load/unload process. A new approach is used where the slider flies under a glass disk so that the entire air bearing surface can be accessed with the LDV laser spot. Load and unload LDV and AE traces are obtained for different vertical speeds for the two slider types.