Measurements of transient thermal strains in a disk-drive actuator

An optical apparatus was built to measure the thermal strain which manifests itself in the tilt of the actuator. Undergoing a heating-cooling, the actuator exhibits a hysteresis in the thermally-induced tilt. There are four regimes in the evolution of the thermal field in either the heating or the cooling phases. Hysteresis in tilt is caused by a reversal of the tilt direction as the actuator changes its thermal regimes. Analyses of a thermal model for actuator find that the first two regimes are dominated by heat transmission from coil to its immediate, contacting components. In contrast, it is the air conduction from coil to its adjacent components that plays a major role in the latter two regimes.