1998 Fiscal Year Final Research Report Summary
Integrated Thermal Analysis of Aerostatic Bearing System
| Project/Area Number |
09650146
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
機械工作・生産工学
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| Research Institution | Aoyama Gakuin University |
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Principal Investigator |
OHISHI Susumu Aoyama Gakuin University Professor, 理工学部, 教授 (70094258)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Aerostatic bearing / Temperature distribution / Finite element method / Compressive Reynolds Equation / Energy equation / Heat conduction equation |
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| Research Abstract |
Air bearings have been considered to have little or no heat generation due to the low viscosity of air, and have been applied mainly to ultra precision machine tools with paying a little attention to the thermal effects. With increasing demand for high speed machining, however, the effect of heat generation in the air-film has become not negligible, because the bearing characteristics are very sensitive to the bearing clearance and it changes due to the thermal deformations of the spindle and housing. The spindle expansion by the centrifugal force also affects it. A final goal of the study is to evaluate aerostatic bearing performances under actual operating conditions, and this project has been undertaken to develop finite element programs to calculate pressure distribution in the air-film (incompressive Reynolds equation) and the air-film and housing temperature distributions (the Energy equation). An aerostatic bearing system has been built to measure temperature distributions, pressures and the spindle deflections experimentally. The air flow in the clearance of the bearing can be considered as the combination of Couette flow caused by the moving part (the rotation of the spindle) and Poiseuille flow caused by the pressure, and the calculations show very interesting results regarding to the effects of these flows. In compressive fluid like air, the temperature distributions are different from those in incompressive fluid. Generally, Couette flow always induces temperature rise regardless of incompressive and compressive fluid. On the other hand, Poiseuille flow induces temperature rise in incompressive fluid, but not in compressive fluid. Whenever the pressure gradient is positive, the temperatures always increase. However, the temperatures could decrease in case the pressure gradient is negative. These calculation results suggest that, in aerostatic bearings, there is a possibility of the temperature decrease if the pressure gradient is large and negative.
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