表面粗糙峰之紋理方向性於混合油膜潤滑中的影響

The Effect of the Orientation of Surface Roughness in the Mixed Lubrication Regime

黃建興(Huang Chien-Hsing)

指導教授 ： 徐澤志

元智大學/工程學院/機械工程學系/碩士(2001年)

摘要

輥軋是塑性加工中的一個重要的金屬成形加工，經由漸進的減壓過程完成所需的鈑厚。輥軋過程中潤滑油的使用，除了有冷卻的效果外，更有保護壓輥及鈑材表面的功能。我們在考慮輥軋過程中潤滑油在液動潤滑時的行為，了解到太厚的潤滑油油膜將造成太低的摩擦，而使壓輥無法有效的輥軋鈑材，然而，太薄的油膜厚度將造成模具及工件直接的接觸形成了磨損的缺陷；太厚或太薄的油膜厚度會造成不理想的工件表面粗糙度，增加製程上的困擾。所以要使鈑材的表面品質優良，其成形潤滑型態必須為混合潤滑。
為了模擬混合潤滑機制，我們結合雷諾方程式及剛塑性有限元素法去模擬。而一般的接觸模式係指在考慮不同狀況下的摩潤行為後，基於該界面狀況所發展出的界面應力計算方式，此應力計算方式將取代傳統界面摩擦方式，而真實的考慮界面的各種變數，包含粗糙度、潤滑油的性質……等，然所計算出的應力分佈、油膜厚度和真實的情況仍有一些差距。此研究的目的在於除了上述的變數外，加入表面峰的方向性參數，將粗糙峰對潤滑油流動的影響加入考慮，及採用了較符合真實情況的新表面峰模型，將可準確的預測出塑性加工時所產生的界面摩擦力、油膜厚度及表面粗糙度。
另外，經由量測軋輥前、後的工件油膜厚度和表面粗糙度及表面峰的方向性，預測出在某一加工條件之下，表面峰的方向性、油膜厚度與表面粗糙度的關係或趨勢，使往後的加工過程中可預先判斷出，需要多少的軋輥速度或潤滑油黏度及減壓率等因素，才能配合出某種加工條件下的油膜厚度，使得工件達到我們想要的表面粗糙度，進而讓加工所需的成本、資源更低廉、節省，使成品品質更加完善。而這部份將利用不同條件下實驗得來的數據，再利用其數據建立其關係。

關鍵字

有限元素法 ； 混合潤滑 ； 表面粗糙度

並列摘要

The rolling is the most important metal forming processes. In most rolling processes, the billet is passed through the roll gap. By reducing the roll gap, the thickness of the billet is decreasing with each pass. The lubricant is used as a coolant, and it protects the roll and billet surfaces, and reduces the friction in the rolling processes, because if the film is too thick, it will make the surface constraint low, a slippery condition and a rough surface will occur. If the film is too thin, it will allow direct contact between roll and billet, which will result in roll wear. So a lubrication regime named mixed lubrication is necessary to get good quality.
In the mixed lubrication regime, part of the load is carried by the contact of the asperity peaks and another part by the pressurized lubricant in the surface valleys. To be able to model the mixed lubrication regime, the pressure generated by the plastic deformation of asperity peaks and the pressure generated in the lubricant film in surface valleys are necessary to be calculated. So we combines Wilson and Marsault’s average Reynolds equation with the rigid-plastic Finite Element Method to determine the hydrodynamic pressure, interface pressure and the film thickness in the interface. A Christensen height distribution and an arbitrary Peklenik surface pattern parameter are adopted, rather than the simple saw-tooth surfaces with longitudinal lay.
The simulation of the film thickness is compared with experimental measurements of surface roughness in rolling aluminum AL1100 billet with different lubricants, reductions, rolling speed and the orientation of roughness. The most important thing is to investigate the relationship between surface roughness, and film thickness in the regime of mixed film lubrication.

並列關鍵字

finite element method ； mixed lubrication ； surface roughness

參考文獻

1. G. J. Li and S. Kobayashi, “Rigid-Plastic Finite-Element Analysis of Plane Strain Rolling.” J. Eng. For Industry, ASME, Vol. 104, pp.55-64, February 1982.

2. F.A.R. AL-Salehi, T. C. Firbank and P.R. Lancaster, “An Experimental Determination of the Roll Pressure Distribution in Cold Rolling.” International Journal of Mech. Sci., Vol.15, pp.693-710, 1973.

3. S. Kobayashi, S. I. Oh and T. Altan, “Metal Forming and the Finite Element Method.” Oxford University Press, Oxford, 1989.

4. W.R.D. Wilson, “Friction and Lubrication in Sheet Metal Forming.” D. P. Koistinen and N. M. Wang, eds, lenum Press, pp.157-177, 1978.

5. W.R.D. Wilson and J. A. Walowit, 1971, “An Isothermal Hydrodynamic Lubrication Theory for Strip Rolling with Front and Back Tension,” Tribology Convention, I. Mech. E., London, pp.169-172, 1971.