点接触润滑状态转化的实验观察

利用球-盘接触润滑油膜厚度的光干涉测量法,通过卷吸速度或载荷的改变实验研究了弹性流体动力润滑与流体动力润滑转化过程中油膜厚度的变化规律。实验结果显示这2种润滑状态之间存在明显的过渡区。与已有的理论一致,在弹性流体动力润滑区和流体动力润滑区,油膜厚度与卷吸速度或载荷在对数坐标中呈直线关系。在两者的过渡区,固体表面的弹性变形量随卷吸速度或载荷的变化发生明显的变化,油膜厚度与速度或载荷的关系不再为对数坐标中简单的线性关系。使用已有的润滑状态区理论不能得到实验观测到的润滑状态的转化过渡区。

考虑润滑和波纹度影响的球轴承径向刚度

建立了考虑波纹度影响的球轴承非线性振动模型,该模型可以用来仿真球轴承的径向刚度。该模型考虑了外圈的五个自由度,并且还同时考虑了流体弹性动力润滑(EHD)油膜的影响。仿真结果表明球轴承表面的波纹度使得球轴承的刚度发生周期性的改变,油膜虽然增大了刚度,但也只是增加了不到1%。最后还通过实验验证了润滑对轴承径向刚度的影响。

表面研磨对点接触弹流润滑的影响

利用计算机模拟获得磨削加工表面及其研磨后表面，完全数值求解磨削表面及研磨表面点接触弹流润滑，就研磨对润滑的影响进行分析与研究。结果得出，表面形貌的微观弹流效应导致局部油膜压力增大，研磨能有效减缓油膜压力波动，改善表面润滑性能。

高黏度齿轮油润滑状态转变的试验观察

利用双色光干涉润滑油膜测量技术,观察球-盘接触副内大黏度齿轮油润滑状态的转变过程,并对不同速度和载荷条件下润滑状态在不同区间内的转化进行定量分析。结果表明:在充分供油条件下,随卷吸速度增加,润滑油膜从弹流润滑状态向动压润滑状态转化,且2种润滑状态之间存在着明显过渡区间;而随着载荷的增加,润滑油膜从动压润滑向弹流润滑状态转化;在定量供油条件下,润滑油膜在弹流润滑区间内从富油润滑状态向乏油润滑状态转化。

考虑压粘刚润滑及弹流润滑的圆柱滚子轴承疲劳寿命分析

由于轴承的疲劳寿命对整个设备的正常运行和安全服役有重大影响,对此提出了一种能够综合考虑压粘刚润滑及弹流润滑的圆柱滚子轴承疲劳寿命计算模型。通过建立滚动体和套圈之间的油膜厚度、几何趋近量与弹性变形量之间的平衡方程,滚动体受力平衡方程以及套圈受力平衡方程,构建了轴承的拟静力学模型,在所建立的拟静力学模型中,根据相应的润滑状态(PVR润滑和EHD润滑)进行了油膜厚度的计算;基于所建立的拟静力学模型以及Lunderg-Palmgren理论,对轴承的疲劳寿命进行了分析。研究结果表明:疲劳寿命随径向载荷的增大而增大,而转速和润滑油初始粘度对轴承疲劳寿命的影响具有一定的非线性;当载荷较小、转速较大、润滑油的初始粘度较大或较小时,应着重考虑PVR和EHD润滑状态对轴承疲劳寿命的影响。

HYDRODYNAMIC AND ELASTOHYDRODYNAMIC STUDIES OF A CYLINDRICAL JOURNAL BEARING

In this article,the effect of the bearing elastic deformation on the performance characteristics of a cylindrical journal bearing is analyzed.The variety of simulation models covers hydrodynamic（HD） and elastohydrodynamic（EHD） lubrication theories.The Reynolds equations governing the flow in the clearance space of the journal bearing are obtained by considering the effect of mass transfer across the fluid film.The finite element method with an iteration scheme was employed to solve both the Reynolds equation and the three-dimensional elasticity equation representing the displacement field in the bearing shell.The converged solutions for the lubricant flow and elastic deformation vector are obtained.Dynamic characteristics of the journal bearing are computed for HD and EHD theories.Numerical simulation results show that the flexibility of bearing liner has a significant influence on the performance of a cylindrical journal bearing.Indeed,the elastic deformations of the bearing liner extend the pressure area in the bearing and increase the minimum film thickness.Although,dynamic coefficient,load capacity and attitude angle decrease.

On the relevance of analytical film thickness EHD equations for isothermal point contacts: Qualitative or quantitative predictions?

Thin film and elastohydrodynamic lubrication regimes are rather young domains of tribology and they are still facing unresolved issues.As they rely upon a full separation of the moving surfaces by a thin (or very thin) fluid film,the knowledge of its thickness is of paramount importance,as for instance to developing lubricated mechanisms with long lasting and efficient designs.As a consequence,a large collection of formulae for point contacts have been proposed in the last 40 years.However,their accuracy and validity have rarely been investigated.The purpose of this paper is to offer an evaluation of the most widespread analytical formulae and to define whether they can be used as qualitative or quantitative predictions.The methodology is based on comparisons with a numerical model for two configurations,circular and elliptical,considering both central and minimum film thicknesses.

Wear protection assessment of ultralow viscosity lubricants in high-power-density engines:A novel wear prediction algorithm

Durability and reliability have been studied for decades through intensive trial-error experimentation.However,there are numerous fields of application where the costs associated with this approach are not acceptable.In lubricated machines with severe dynamic loads,such as high-power-density engines,simulation tools offer clear advantages over intensive testing.Prototypes and multiple scenarios can be cost-effectively simulated to assess different lubricants and engine configurations.The work presented here details the study of wear based on a validated elastohydrodynamic(EHD)simulation model of the connecting rod journal bearing.This model accounts for elastic deformation through a connecting rod finite element model(FEM).In addition,multiple lubricant rheological and tribological dependences,determined by specific experimental tests,are applied in the model through their interaction with the simulation software.Correspondingly,a novel wear algorithm is proposed to predict wear depth over time evolution along a proposed wear cycle based on the typical working ranges of high-performance engines.A final assessment is presented to compare 4 different ultralow-viscosity lubricants in their protective performance under severe conditions.The results show the evolution of the wear load and wear depth over the wear cycle.This evaluation is key to describing a lubricant selection procedure for high-power-density engines.

二冲程船舶柴油机主轴承润滑数值分析

为准确分析某大型二冲程6缸船舶柴油机主轴承润滑状况,将有限元法与非线性多体动力学相结合,对主轴承润滑状况进行弹性流体动力润滑(EHD)分析.计算整个工作循环下的各主轴承载荷、轴心轨迹、偏心距和最小油膜厚度及油膜压力分布等参数.结果表明,2#、3#、5#和6#主轴承在一个周期内出现3次载荷峰值,最大载荷约1500 kN;6#主轴承载荷最大,为1575 kN,其轴承偏心距也较大;2#轴承油膜厚度最小,为4.75μm,此时油膜压力较大,偏布于轴瓦边缘;2#主轴承润滑状况相对较差.