發(fā)布時間：2018-06-10 19:06

  本文選題：表面紋理 + 流體動壓潤滑��； 參考：《中國礦業(yè)大學》2013年博士論文

【摘要】：近年來，表面紋理作為一種可以顯著改善表面摩擦學性能的方法得到國內(nèi)外學者的廣泛關注，成為當前摩擦學領域熱點研究方向之一。為了尋找具有優(yōu)異潤滑性能的紋理幾何形貌和參數(shù)組合，最大可能的改善摩擦性能，申請人利用理論分析和數(shù)值模擬的方法，針對宏觀紋理表面動壓潤滑問題，圍繞Reynolds方程的有效性評價、紋理表面動壓潤滑形成機理、幾何形貌和參數(shù)對紋理表面動壓潤滑性能的影響規(guī)律、紋理表面的優(yōu)化設計四個方面展開了系統(tǒng)討論。 首先基于Reynolds方程和Navier-Stokes方程在流體動壓潤滑條件下建立了紋理表面的潤滑模型。通過理論分析和數(shù)值模擬發(fā)現(xiàn)Reynolds方程有效性的兩個決定性因素是縮減的雷諾數(shù)和油膜厚度與紋理特征長度比。只有當這兩個因素同時趨近于零時，Reynolds方程才不至于造成不可接受的誤差；對于矩形微坑紋理表面，Reynolds方程有效性的評價準則為：油膜厚度與紋理特征長度的比值小于0.015，并且縮減的雷諾數(shù)小于0.20。 推導出了基于Reynolds方程的矩形紋理表面動壓潤滑的解析解；得到了使?jié)櫥阅苋肿顑?yōu)的無量綱微坑深度和寬度的解析表達，最優(yōu)的無量綱深度和寬度組合為~0.87和~0.72。數(shù)值模擬驗證了這一結果。進一步研究表明，即使在Reynolds方程不能有效使用的情況下，理論預測的最優(yōu)微坑深度也能與數(shù)值計算結果相一致；這為工程應用中矩形紋理的優(yōu)化設計提供了可靠、高效的理論依據(jù)。 其次，提出和論證了單個微坑和整體軸承兩個層面的紋理表面動壓潤滑形成機理，分析了紋理參數(shù)和工況條件對潤滑形成機理的影響規(guī)律。并繪制了矩形溝槽紋理表面潤滑機理“相圖”。基于動壓潤滑形成機理和參數(shù)的影響規(guī)律，分析了潤滑性能的提高對紋理形狀的需求，由此設計了具有優(yōu)異潤滑性能的楔形紋理表面。通過與矩形、三角形、圓弧形、橢圓形紋理的對比發(fā)現(xiàn)楔形紋理在低雷諾數(shù)下具有最優(yōu)的動壓潤滑性能；在此基礎上，構建了楔形微坑的多紋理軸承，并分析了幾何參數(shù)對其動壓潤滑性能的影響規(guī)律。 壓印方法在45#鋼表面制備了陣列排布的球冠狀微坑紋理表面，并采用銷-盤實驗和數(shù)值模擬方法評價了其摩擦性能。實驗表明，只有合適的紋理尺寸才能夠在特定的載荷下起到降低摩擦的作用，不適當?shù)募y理尺寸不但起不到減摩的作用，，甚至會起到反作用。數(shù)值模擬與該實驗結果基本保持一致。 最后，建立了具有紋理表面和光滑表面的單晶硅納米薄膜的分子動力學模型，研究了單晶硅納米薄膜紋理表面和光滑表面納米力學性能和摩擦行為。結果表明納米紋理的引入增加了摩擦力，降低了薄膜硬度，改變了摩擦法則，即：摩擦力與載荷的關系將從光滑表面的超線性關系轉變?yōu)榧y理表面的線性關系；紋理表面的摩擦力與載荷隨紋理做周期性的振蕩；摩擦力頻譜包含了豐富的結構信息。納米壓痕中，相變是單晶硅納米薄膜塑性變形唯一的機理；金剛石結構的Si-I轉變?yōu)轶w心結構的Si-II和BCT5相是單晶硅納米薄膜納米壓痕加載過程主要的相變機制；BCT5相的出現(xiàn)領先于Si-II相；卸載過程中高壓Si-II和BCT5相全部轉變?yōu)榉蔷唷?br/>[Abstract]:In recent years, surface texture has been widely concerned by scholars both at home and abroad as a method to improve the tribological properties of the surface. It has become one of the hot research fields in the field of tribology. In order to find the best possible lubricating properties, the most likely to improve the friction performance is to use the theory. In view of the dynamic lubrication problem of the macroscopic texture surface, the method of analysis and numerical simulation is focused on the effectiveness evaluation of the Reynolds equation, the formation mechanism of the dynamic pressure lubrication of the texture surface, the influence of the geometric morphology and parameters on the dynamic lubrication performance of the texture surface, and the four aspects of the optimization of the texture surface.
Based on the Reynolds equation and the Navier-Stokes equation, the lubrication model of the texture surface is established under the hydrodynamic lubrication condition. Through theoretical analysis and numerical simulation, it is found that the two decisive factors of the validity of the Reynolds equation are the reduced Reynolds number and the oil film thickness and the texture feature length ratio. Only when these two factors are approaching at the same time At zero, the Reynolds equation does not cause unacceptable error. For the rectangular micropits texture surface, the evaluation criterion for the effectiveness of the Reynolds equation is that the ratio of the oil film thickness to the texture feature length is less than 0.015, and the reduced Reynolds number is less than 0.20..
The analytical solution of the dynamic pressure lubrication of the rectangular texture surface based on the Reynolds equation is derived. The analytical expression of the depth and width of the dimensionless pit for the global optimum lubrication performance is obtained. The optimal dimensionless depth and width combination is verified by the numerical simulation of ~0.87 and ~0.72.. Further research shows that even in the Reynolds square The optimal micro pit depth predicted by theory can also be consistent with the numerical results, which provides a reliable and efficient theoretical basis for the optimization design of rectangular texture in engineering applications.
Secondly, the formation mechanism of the dynamic lubrication of the texture surface on two layers of a single micro pit and a whole bearing is presented and demonstrated. The influence of the texture parameters and working conditions on the lubrication mechanism is analyzed. The phase diagram of the lubrication mechanism of the rectangular groove texture surface is drawn. Based on the mechanism of the dynamic lubrication and the influence of the parameters, the mechanism of the dynamic lubrication and the parameters are analyzed. A wedge texture surface with excellent lubrication performance is designed to improve the texture shape. By comparing with the rectangle, triangle, arc and ellipse texture, it is found that the wedge texture has the best dynamic lubrication performance at low Reynolds number, and on this basis, the multi texture bearing of the wedge micro pit is constructed. The influence of geometric parameters on hydrodynamic lubrication performance is also analyzed.
The texture surface of the ball coronal micro pits was prepared on the surface of 45# steel on the surface of the array, and the friction performance was evaluated by the pin disk experiment and the numerical simulation method. The experiment shows that only the suitable texture size can reduce the friction under the specific load, and the inappropriate texture size can not reduce the friction effect. It may even be counterproductive. Numerical simulation is basically consistent with the experimental results.
Finally, the molecular dynamics model of monocrystalline silicon Nanothin films with texture surface and smooth surface was established. The nanomechanical properties and friction behavior of the smooth surface were studied. The results showed that the introduction of the nano texture increased the friction force, reduced the hardness of the film, and changed the friction rule, that is, friction. The relationship between force and load changes from the superlinear relationship of the smooth surface to the linear relationship of the texture surface; the frictional force and load of the texture surface oscillate with the texture, and the friction spectrum contains rich structural information. In the nano indentation, the phase transition is the only mechanism of the plastic deformation of the monocrystalline silicon thin film; the diamond structure is the only mechanism. The transformation of Si-I into the Si-II and BCT5 phase of the body core structure is the main phase transition mechanism in the nano indentation loading process of monocrystalline silicon Nanothin films, and the appearance of the BCT5 phase is leading to the Si-II phase, and the high pressure Si-II and the BCT5 phase are all transformed into amorphous phase during the unloading process.
【學位授予單位】：中國礦業(yè)大學
【學位級別】：博士
【學位授予年份】：2013
【分類號】：TH117

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本文編號：2004283