润滑接触摩擦行为研究是润滑理论的重要组成部分，对由相对运动表面构成的机械零部件性能、效率和可靠性有直接影响。为系统研究接触表面摩擦行为在包括流体润滑、混合润滑和边界润滑的整个润滑区域内的变化规律，以及粗糙度幅值和纹理方向对润滑接触摩擦行为的影响，本文根据粘弹性润滑薄膜的微观结构特点，提出固、液分配系数的概念，基于统一Reynolds方程的确定性混合润滑模型，建立了润滑接触摩擦力的统一模型。在此基础上，采用多次重复实验与数值模拟相结合方法，研究了表面粗糙度幅值和纹理方向对润滑接触摩擦行为的影响以及随润滑状态改变的转换规律。对润滑接触中摩擦状态在整个润滑区域内转换的研究发现，无论粗糙表面还是光滑表面，接触从流体润滑经混合润滑到边界润滑状态，摩擦状态曲线连续光滑过渡。表面越光滑，摩擦力曲线越陡峭；反之，则越平坦。表面越光滑，从流体润滑到混合润滑过渡地临界速度越小，而粗糙度的横、纵纹理对临界速度没有影响；从混合润滑到边界润滑，摩擦状态平滑过渡，临界速度不明显。在流体润滑和混合润滑下，表面越粗糙，摩擦力越大；横纹表面摩擦力比纵向纹理表面的摩擦力低且平稳。边界润滑状态下，粗糙度对摩擦行为影响减弱。接触面积决定了粗糙度幅值对润滑接触摩擦行为的影响，使不同粗糙度幅值表面的摩擦曲线沿不同的路径在润滑区域内过渡。高速时，横、纵纹理的成膜能力决定了二者对润滑接触摩擦行为影响的差异；低速时磨损是导致这种差异的主要原因。横纹有较强的成膜能力，磨损较轻,润滑接触摩擦力低于纵纹。与粗糙表面的实验结果比较发现，本文提出的润滑接触摩擦力的统一模型准确模拟了润滑接触中从流体润滑到混合润滑的临界速度和混合润滑到边界润滑的过渡趋势。说明该模型能够有效模拟润滑接触摩擦行为在整个润滑域内的转化,为润滑接触摩擦力的预测提供了有力的模拟工具。对纳米级光滑表面的研究表明，在真实接触发生之前，接触进入薄膜润滑状态，摩擦力随速度降低逐渐增加。关键词：混合润滑与薄膜润滑；摩擦模型；摩擦状态转化；润滑剂流变特性；粗糙度影响

As one of important parts of lubrication theory, friction behaviors of machine elements, with surfaces in lubricated contacts and relative-motion, influence directly on their performances, efficient and reliability. To investigate systematically the tribological behaviors of the mating surfaces in overall lubrication regimes, including fluid, mixed and boundary lubrication, the partition coefficient used to describe the solid to liquid ratio in viscoelastic lubrication film is defined in this thesis. And based on a united Reynolds equation in mixed lubrication area for deterministic mixed lubrication model, a full friction model covering all lubrication regimes is also presented. On the basis of this model, the effects of roughness amplitude and orientation on friction behaviors are studied as well as the transition of lubrication states.Concerning the transition of frictional states in overall lubrication areas, the frictional curves follow different routes continuously and smoothly due to the difference in roughness amplitude. The smoother surface displays the sharper turning curves; conversely, the curve appears to be flatter for the rougher surface. The smoother surface will give rise to a smaller critical speed of the transition from full-film to mixed lubrication. But the roughness orientation has little effect on the speed. Meanwhile, gentle transitions of frictional states from mixed to boundary lubrication can be observed from the experiment and simulation results on all rough and smooth surfaces. In fluid and mixed lubrications, rougher surface will give larger friction. And the transverse roughness shows smaller friction and lower frictional fluctuation in comparison to longitudinal one. The roughness effects on friction behaviors get weak in boundary lubrication state. In lubricated contacts, the effect of roughness amplitude on frictional performances is determined by contact area, which results in frictional curves pass through different paths. In higher speed, the difference of the transverse and longitudinal roughness in friction performances is predominated by their capacity of film formation. In lower speed, the difference comes mainly from the wear of the mating surface. The result suggests that the surface with transverse roughness has stronger film-forming capacity in higher speed, less wear in lower speed. So the transverse roughness appears to better lubrication capability.By comparing simulation with the experiment results of different surfaces in roughness amplitude and material, the full friction model for lubricated-contact, presented in this dissertation, can predict friction performance and the critical transition speed between fluid and mixed lubrication. It is concluded that the model can simulate effectively the transition of frictional states, and is a powerful tool of predicting friction in lubricated contacts. For surface with nano-scale roughness amplitude, the contact is in thin film lubrication regime when the direct contact of the mating surfaces doesn’t occur. At this time, the rheological properties of thin lubrication film begin to change so that friction of the thin film increases with the diminishing film thickness.Key words: mixed and thin film lubrication; friction model; transition of friction states; lubricant rheology; roughness effects