Analysis of a Hydrodynamic Bearing of a HDD Spindle Motor at Elevated Temperature

2004 ◽  
Vol 126 (2) ◽  
pp. 353-359 ◽  
Author(s):  
G. H. Jang ◽  
K. S. Kim ◽  
H. S. Lee ◽  
C. S. Kim
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Elevated Temperature ◽  
Dynamic Characteristics ◽  
Spindle Motor ◽  
Element Analysis ◽  
Hydrodynamic Bearings ◽  
Static And Dynamic Characteristics ◽  
Hydrodynamic Bearing ◽  
Lubricant Viscosity

This paper presents a method to investigate the characteristics of hydrodynamic bearings of a HDD spindle motor considering the variation of the clearance as well as the lubricant viscosity due to elevated temperature. Iterative finite element analysis of heat conduction and thermal deformation is performed to determine the viscosity and clearance of hydrodynamic bearings at elevated temperature until the temperature in the bearing area converges. The proposed method is verified by comparing the calculated temperature with the measured one at elevated surrounding temperature as well as in room temperature. This research shows that elevated temperature changes the clearance as well as the lubricant viscosity of the hydrodynamic bearings of a HDD spindle motor. Once the viscosity and clearance of hydrodynamic bearings of a HDD spindle motor are determined, finite element analysis of the Reynolds equation is performed to investigate the static and dynamic characteristics of hydrodynamic bearings of a HDD spindle motor at elevated temperature. It also shows that the variation of clearance due to elevated temperature is another important design consideration which affects the static and dynamic characteristics of the hydrodynamic bearings of a HDD spindle motor.

Structural investigation of steel-reinforced epoxy granite machine tool column by finite element analysis

2019 ◽  
Vol 233 (11) ◽  
pp. 2267-2279 ◽  
Author(s):  
Prabhu Raja Venugopal ◽  
M Kalayarasan ◽  
PR Thyla ◽  
PV Mohanram ◽  
Mahendrakumar Nataraj ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cast Iron ◽  
Machine Tool ◽  
Dynamic Characteristics ◽  
Element Model ◽  
Static Stiffness ◽  
Element Analysis ◽  
Static And Dynamic Characteristics ◽  
Machining Center

Higher damping with higher static stiffness is essential for improving the static and dynamic characteristics of machine tool structures. The structural vibration in conventional machine tools, which are generally made up of cast iron and cast steel, may lead to poor surface finish and the dimensional inaccuracy in the machined products. It leads to the investigation of alternative machine tool structural materials such as concrete, polymer concrete, and epoxy granite. Although epoxy granite has a better damping capacity, its structural stiffness (Young's modulus) is one-third as compared to cast iron. Therefore, the present work represents optimization of the structural design of the vertical machining center column by introducing various designs of steel reinforcement in the epoxy granite structure to improve its static and dynamic characteristics using experimental and numerical approaches. A finite element model of the existing cast iron vertical machining center column has been developed and validated against the experimental data obtained using modal analysis. Furthermore, finite element models for various epoxy granite column designs have been developed and compared with the static and dynamic characteristics of cast iron column. A total of nine design configurations for epoxy granite column with steel reinforcement are evolved and numerical investigations are carried out by finite element analysis. The proposed final configuration with standard steel sections has been modeled using finite element analysis for an equivalent static stiffness and natural frequencies of about 12–20% higher than cast iron structure. Therefore, the proposed finite element model of epoxy-granite-made vertical machining center column can be used as a viable alternative for the existing column in order to achieve higher structural damping, equivalent or higher static stiffness and, easy and environmental-friendly manufacturing process.

Study on static and dynamic characteristics of nettle–polyester composite micro lathe bed

2016 ◽  
Vol 233 (2) ◽  
pp. 141-155 ◽  
Author(s):  
N Mahendrakumar ◽  
PR Thyla ◽  
PV Mohanram ◽  
C Raja Kumaran ◽  
J Jayachandresh
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Cast Iron ◽  
Dynamic Characteristics ◽  
Torsional Stiffness ◽  
Element Analysis ◽  
Worst Case ◽  
Design Modification ◽  
Static And Dynamic Characteristics ◽  
Polyester Composite

Nowadays, natural fibre-reinforced composites find applications in almost all engineering fields. This work is an attempt to realise improvement in dynamic characteristics of micro lathe bed using Himalayan nettle (Girardinia heterophylla) polyester (NP) composite as an alternate material. In order to study and validate the improvements envisaged, a cast iron micro lathe bed is considered as reference. Numerical (FE) model of the cast iron micro lathe bed was developed and validated through experimental static and modal analysis. Finite element analysis of the micro lathe bed with the existing cast iron material as well as with nettle–polyester composite as alternate material was also carried out using worst case cutting forces, and based on the relative performances, the need for form design modification for the proposed material was identified. To enhance the bending and torsional stiffness of the nettle–polyester composite lathe bed, various cross sections and rib configurations were studied and the best among them was identified and the same was implemented in the nettle–polyester composite micro lathe bed design. Finite element analysis of the newly designed nettle–polyester composite micro lathe bed was performed and the improvements in dynamic characteristics were evaluated. The newly designed nettle–polyester composite micro lathe bed was fabricated and the predicted enhancement in static and dynamic characteristics was verified experimentally. The studies indicated that nettle–polyester composite could be considered as a suitable alternate to cast iron structures in machine tools.

scholarly journals Dynamic characteristics of triaxial active control magnetic bearing with asymmetric structure

Open Physics ◽  
2018 ◽  
Vol 16 (1) ◽  
pp. 9-13 ◽  
Author(s):  
Atsushi Nakajima ◽  
Katsuhiro Hirata ◽  
Noboru Niguchi ◽  
Masayuki Kato
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Active Control ◽  
Dynamic Characteristics ◽  
Negative Pressure ◽  
Axial Direction ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Asymmetric Structure ◽  
Element Analysis

Abstract Supporting forces of magnetic bearings are lower than those of mechanical bearings. In order to solve these problems, this paper proposes a new three-axis active control magnetic bearing (3-axis AMB) with an asymmetric structure where its rotor is attracted only in one axial direction due to a negative pressure of fluid. Our proposed 3-axis AMB can generate a large suspension force in one axial direction due to the asymmetric structure. The performances of our proposed 3-axis AMB are computed through 3-D finite element analysis.

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