Pressure-sensitive paint measurement on co-rotating disks in a hard disk drive

There is much demand for improvement in the performance of a hard disk drive (HDD) along with recent rapid developments of information technology. While high-speed disk rotation of a HDD is necessary to accommodate such needs, it causes disk flutter induced by pressure fluctuation on disks and degrades reliability of a HDD. In order to understand the mechanism of the fluttering phenomenon, it is important to know pressure field on the rotating disk. However, it is impossible to measure the pressure by ordinary methods such as pressure taps. Pressure-sensitive paint (PSP) is a pressure measurement technique based on the oxygen quenching of luminescence and enables us to measure the pressure non-invasively. In general, however, the temperature sensitivity of PSP makes it difficult to measure the precise pressure on the surface with temperature distribution. We measured the time-averaged pressure on the disk rotating at 10 000–20 000 rpm for the first time by adopting a temperature-insensitive PSP composed of pyrene sulfonic acid (PySO3H) as a luminophore. It was found that the pressure forms a concentric circular distribution and decreases toward the center of the disk. Additionally, we elucidate how disk rotational speed and spacing between co-rotating disks influence on the pressure field.

► The pressure distributions on a rotating disk in a HDD were measured by pressure-sensitive paint (PSP). ► The pressure distributions were successfully obtained by temperature-insensitive PSP. ► The pressure formed a concentric circular distribution and decreased toward the center of the disk. ► The pressure difference between the inner and outer regions of the disk increased as a square of the disk rotational speed. ► The pressure difference increased with a decrease in a disk spacing.