Detecting oscillation amplitude and defects of hard disk rotating in high speed by laser Doppler technique

Laser Doppler technique is widely used in industry for the purpose of detecting vibration and oscillation. Many researchers have found that using non-contact laser vibrometry to measure surface roughness of disk under dynamic status is more difficult than that of the static condition. In this paper, we proposed a laser Doppler technique for the purpose of measuring the oscillation amplitude and defects of hard disk rotating in high speed. Laser light source, optical Doppler system, detector and data process system were integrated in our experimental system. The whole system was calibrated using a sinusoid generator. The method for converting the measured voltage signals into the corresponding size data was described in detail. It was found that the average size of defects of the hard disk in our experiment is from 1 μm to 5 μm. The developed technique may be useful for quality control in real time in mass production processes.     

A study on the stress and nonuniformity of the wafer surface for the chemical-mechanical polishing process

In this paper, a two-dimensional axisymmetric quasic-static model for the chemical-mechanical polishing process (CMP) was established. Based on the principle of minimum total potential energy, a finite element model for CMP was thus established. In this model, the four-layer structures including the wafer carrier, the carrier film, the wafer and the pad are involved. The von Mises stress distributions on the wafer surface were analysed, and the effects of characteristics of the pad and the carrier film and the load of the carrier on the von Mises stress and nonuniformity on the wafer surface were investigated. The findings indicate that the profile of the von Mises stress distributions correlates with the removal rate profile. The elastic modulus and thickness of pad and carrier load would significantly affect the von Mises stress and nonuniformity, but those of the film did not affect very much.     

The whole-beat correlation method for the identification of an unbalance response of a dual-rotor system with a slight rotating speed difference

Identification of the unbalance mass is pivotal in the balancing of a dual-rotor system with a slight speed difference. In the first part, this paper presents the whole-beat correlation method for the whole-machine balancing of the dual-rotor system based on correlation theory. In the second part, an optimized whole-beat correlation method is proposed based on error analysis. In the last part, a balancing experiment is conducted on the horizontal decanter centrifuge, validating the precision, efficiency, and applicability of the recommended method.