Mechanism of Thin Film Lubrication

研究了薄膜润滑的机理和固化润滑膜的剪切特性。1.润滑剂的低温剪切特性：润滑油中的剪切或滑动发生在薄剪切层内，润滑油表现为粘弹性或弹塑性材料。剪切应力τ用τ = aexp（E/RT）表示。这里，a、E、R和T分别是常数、活化能、气体常数和绝对温度。2.集中接触中的牵引性能：牵引系数主要由α乘以p的乘积α p确定。α p是经受剪切的油的填充状态的量度。3.油建立流体动力润滑膜的限制能力：存在一个临界滑动速度，当滑动速度超过该临界滑动速度时，油膜厚度随滑动速度或轴承模量的增大而减小。摩擦力也随着滑动速度的增加而减小。这主要归因于供油中只有低粘度组分容易进入结合区。4.加减速运动中的超薄油膜行为：变滑动速度试验中的油膜厚度与相应的恒滑动速度试验中的油膜厚度不相等。油膜厚度的差异主要是由挤压作用引起的。

Mechanism and of thin film lubrication and shear characteristics of solidified lubrication film were studied.1.Shear properties of lubricant at low temperature : The shearing or sliding occurred within a thin shear layr in an oil and the oil behaved as a viscoelastic or elastoplastic material. Shear stress tau was expressed by tau=a exp (E/RT). Here, a, E,R,and T are an constant, activation energy, gas constant and absolute temperature, reapectively.2.Traction properties in concentrated contact : The coefficient of traction was mainly determined by alphap of a product alpha multiplied by p. alphap is a measure of the packing state of oils subjected to shearing.3.Limiting ability of oils to built up a hydrodynamic lubrication film : There is a critical sliding speed above which the oil film thickness inversely decreased in spite of increasing the sliding speed or the value of bearing modulus. The friction force also decreased with increasing the sliding speed above the critical one. Therse phenomena were mainly ascribed to that only the lower viscosity components of the supplied oil were prone to be introduced to the conjunction zone.4.Ultra thin film behavior in accelerating and decelerating motion : The oil film thickness in changing sliding speed tests was not equal to that in the corresponding constant sliding apeed. The difference in oil film thickness was brought mainly about squeeze action.