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RESEARCH PAPERS

# Finite Element Analysis of the Coupled Journal and Thrust Bearing in a Computer Hard Disk Drive

[+] Author and Article Information
G. H. Jang

PREM, Department of Mechanical Engineering,  Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul, 133-791, Republic of Koreaghjang@hanyang.ac.kr

S. H. Lee, H. W. Kim

PREM, Department of Mechanical Engineering,  Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul, 133-791, Republic of Korea

J. Tribol 128(2), 335-340 (Oct 17, 2005) (6 pages) doi:10.1115/1.2162918 History: Received July 11, 2005; Revised October 17, 2005

## Abstract

This paper proposes a method to calculate the characteristics of a coupled fluid dynamic journal and thrust bearing of a hard disk drive (HDD) spindle motor. The governing equations for the journal and thrust bearings are the two-dimensional Reynolds equations in the $θz$ and $rθ$ planes, respectively. The finite element method is appropriately applied to analyze the coupled bearing under the conditions of the continuity of mass and pressure at the interface between the journal and thrust bearings. The pressure in the coupled bearing was calculated by applying the Reynolds boundary condition. The validity of this application was verified by comparing the analytical results of the flying height at various rotating speeds with experimental results. The characteristics of the coupled journal and thrust bearing were also investigated due to the Reynolds and Half-Sommerfeld boundary conditions and the coupled and separate analysis. This research demonstrates that the proposed method can accurately and realistically describe the coupled fluid dynamic bearing in a HDD system.

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## Figures

Figure 4

Finite element model and pressure distribution of the FDBs

Figure 5

Simulated results of flying height at various rotating speeds

Figure 6

Experimental results of flying height at various rotating speeds

Figure 7

Comparison of the cavitation region of the journal bearing due to the internal boundary conditions: (a) Half-Sommerfeld BC and (b) Reynolds BC

Figure 8

Cavitation region of the upper and the lower journal bearing in separate analysis: (a) upper journal bearing and (b) lower journal bearing

Figure 3

Boundary condition of the coupled journal and thrust bearing

Figure 2

Coordinate system of the coupled journal and thrust bearing in a HDD

Figure 1

Structure of a 3.5in. HDD spindle motor with the FDBs

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