Modal contribution analysis of an operating complete flexible HDD affecting the head-disk motion due to shock

Abstract

This paper proposes a finite element modal and shock analysis of an operating complete flexible hard disk drive (HDD). It develops a finite element model of a complete flexible HDD including the spinning disk-spindle system with fluid dynamic bearings, the head-suspension-actuator with pivot bearings and air bearings, the base plate and cover with complicated geometry. The finite element model also includes a mounting table, which is a tetrahedron element with big mass, to simulate the shock to the HDD from the exciter. It performs the modal analysis to calculate the natural frequencies and mode shapes as well as the mode superposition to calculate the motion between head and disk. It proposes a method to determine the contribution of each superposed vibration mode to the head-disk motion of an operating complete flexible HDD due to shock. It also proposes the numerical criterion to determine the head crash due to shock, and it is applied to investigate the contribution of each vibration mode to the head-disk motion when the head-crash occurs. It shows that the coupled (0,0) disk modes play the dominant role on the head-disk motion and that the pure disk modes have no effect on the head-disk motion under the axial shock. The proposed method can be effectively applied to investigate the dynamics of a HDD and to design a robust HDD against shock to prevent the head-crash.