大模数蜗杆铣刀专用机床设计计量器具的选择(任务书+CAD图纸+外文文献翻译) 第4页
effect, the Reynolds equation is expressed as Eq. (17).
In Eq. (17),. The normal velocity of the lubricant is expressed as Eq. (18).
With Eq. (18) and Eq. (17), the equation used for numerical calculation is shown as Eq. (19).
The first item on the right of Eq. (19) represents the effect of the geometry, the second item represents the extrusion effect, the third item represents the effect of the first normal stress difference. When , the pressure profiles are shown in Fig. 6 considering different effects.
Figure 6. Pressure profiles under different effects
In Fig. 6, 0p represents the pressure profile under the only effect of lubricant geometry. 1p represents the pressure profile under the effect of the geometry and the extrusion effect. 2p represents the pressure profile under the effect of the geometry and the first normal stress difference. And as the normal velocity of
the lubricant increases, the effect of the first normal stress difference is enlarged, the first normal stress difference should not be omitted according to the results shown in Fig. 6.
From the results, we may also find that the extrusion effect is more important than the first normal stress difference. Shown in Fig. 6, the increment of the pressure peak caused by the extrusion effect is far more than the increment caused by the first normal stress difference. So, in head-disk interface lubrication, the effect of the lubricant extrusion and the first normal stress difference should both be considered.
5. Conclusions
When a non-Newtonian lubricant is used in the magnetic head-disk interface lubrication, its normal stress effect can be calculated by a modified Reynolds equation which includes a function of first normal stress difference. The expression of the first normal stress difference is derived from the Rivlin-Ericksen equation and the momentum equation, together with the coordinates conversion. The effect of the normal stress in the head-disk interface lubrication is not only affected by the non-Newtonian fluid material parameters, but also is affected by the normal velocity.
Under the steady laminar flow, the pressure and the load capacity are increased by the effect of the first normal stress difference. But the effect is not significant because of the small normal velocity. Considering both from the theoretical analysis and from the true lubrication calculation, the first normal stress difference can be omitted while the differential viscosity is the principal factor that determines the lubrication effect.
When the normal velocity of the lubricant increases because of the movement of the slider, the Reynolds equation is modified again to include the effect of the normal velocity. The numerical result shows that the effect of the first normal stress difference is enlarged and needs to be calculated in lubrication.
Acknowledgment
This work is supported by the Research Fund for the Doctoral Program of Higher Education，No. 20030003026.
References：
[1] De Bruvne F.A., Bogy D.B., Numerical simulation of the lubrication of the head-disk interface using a non-Newtonian fluid. ASME Journal of Tribology. 116, 1994, pp: 541-548.
[2] Wang L.L., Cheng I. W., An average Reynolds equation for non-Newtonian fluid with application to the lubrication of the magnetic head-disk interface. Tribology transaction, 1997(1), pp: 111-119.
[3] Swamy, S.T. Caculated load capacity of non-newtonian lubricants in finite width journal bearings. Wear, 1975, 31:.277-285.
[4] Christensen R.M., Saibel E.A. Normal stress effects in viscoelastic fluid lubrication. Journal of Non-Newtonian fluid mech. 1980, 7, pp: 63-75.
[5] Harnoy A. Analysis of stress relaxation in elasitco-viscous fluid lubrication of journal bearing. J. of Lubr. Tech. 1978, 100, pp: 287-291.
[6] Rivlin R.S. The hydrodynamics of non-newtonian fluids. Proc. Roy. Soc. A, 1948, 193, pp: 261-280
[7] Becker E. Simple non-Newtonian fluid flows. Advances in Applied Mech. 1980, 20, pp 212-226.
[8] Khurshudov, Andrei; Ivett, Peter，Head–disk contact detection in the hard-disk drives，Wear 255, 2003(8-9), pp. 1314-1322
[9] Kawakubo, Y.; Ishii, M.; Sasaki, N，Sliding-pin shapes and lubricant thickness change on a thin-film magnetic disk，Tribology International 2003(8), Vol 36, pp. 593-598
[10] Novotny VJ, Baldwinson MA. Lubricant dynamics in sliding and flying. J Appl Phys 1991, Vol 70, pp:5647–52.
[11] Pinkus O. Theory of hydrodynamic lubrication, New York : McGraw-Hill Book Co., Inc., 1961.
上一页 [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] ... 下一页 >>
大模数蜗杆铣刀专用机床设计计量器具的选择(任务书+CAD图纸+外文文献翻译) 第4页下载如图片无法显示或论文不完整，请联系qq752018766
