耦合因素对混合润滑滑动轴承特性的影响

Influence of Coupling Factors on Characteristics of Mixed Lubrication Sliding Bearings

低速工况下处于混合润滑状态的滑动轴承易因变形或倾斜而发生磨损。为分析轴颈倾斜和磨损对滑动轴承混合润滑特性的影响,建立了计入轴颈倾斜和弹性变形的平均流量方程、G-T接触方程和Archard磨损方程耦合模型,采用有限差分法及超松弛迭代法计算混合润滑状态下轴承特性参数和时变磨损参数,对比了轴颈倾斜前后或磨损前后轴承的润滑性能,并分析粗糙度和边界摩擦系数等因素对各性能参数的影响。搭建摩擦磨损试验台测试了倾斜状态下轴承的润滑特性,验证了理论模型的正确性。理论分析与试验结果表明:重载大偏心时轴承转变为混合润滑状态,轴颈倾斜程度越大,轴承越容易发生混合润滑;轴承倾斜后,压力峰值和接触区域形状发生改变,磨损量因而发生变化,并且磨损深度分布沿轴向或周向倾斜;磨损降低了油膜的动压效应,并且使膜厚比降低,导致油膜压力峰值下降约20%,接触压力峰值降低约90%,承载力最高下降约19.71%;对比磨损前后的轴承形貌发现,轴颈倾斜使得磨损集中于间隙减小的一端。该研究可为实际工程中轴承的设计提供理论依据。

Sliding bearings in mixed lubrication state are prone to wear due to deformation or misalignment under low-speed conditions.In order to analyze the influence of journal misalignment and wear on the mixed lubrication characteristics of sliding bearings,this study established a coupled model of average flow equation,G-T contact equation and Archard wear equation considering journal misalignment and elastic deformation.The bearing characteristic parameters and time-varying wear parameters under mixed lubrication were calculated by finite difference method and over-relaxation iteration method.The lubrication performance of bearings before and after journal misalignment or wear was compared,and the effect of roughness and boundary friction coefficient on various performance parameters was analyzed.A friction and wear test rig was built to test the lubrication characteristics of bearings in misaligned state,which verified the correctness of the theoretical model.The theoretical analysis and experimental results show that,when heavy load and large eccentricity occur,the bearing will change to mixed lubrication state.The greater the journal tilt,the more likely the bearing to have mixed lubrication.When the bearing is misaligned,the peak pressure and the shape of contact area will change,resulting in a difference in wear and the distribution of wear depth is tilted either axially or circumferential.The wear reduces the fluid hydrodynamic effect and decreases the film thickness ratio,leading to a decrease of about 20%in the hydrodynamic pressure peak,a decrease of about 90%in the contact pressure peak,and a maximum decrease of about 19.71%in bearing capacity.By comparing the bearing morphologies before and after wear,it finds that the journal tilts leads to that the wear concentrates on the end where the clearance reduces.This research provides theoretical basis for sliding bearing design in practical engineering.