流变模型对剪切稀化流体弹流油膜厚度影响的研究

基于Carreau流变模型和Ree—Eyring流变模型,对剪切稀化流体线接触弹流润滑进行了完全数值分析,得到了同一种润滑油在不同流变模型下的弹流油膜厚度。将理论分析得到的油膜厚度、经典弹流膜厚公式计算的油膜厚度以及实测的油膜厚度进行了对比,结果表明：基于Carreau流变模型的理论分析结果更能反映剪切稀化流体的实际弹流油膜厚度;在相同工况下,基于Ree—Eyring流变模型的理论分析结果低估了剪切稀化流体的油膜厚度,经典弹流膜厚公式过高地估计了剪切稀化流体的油膜厚度。研究结果表明：幂函数形式的流变模型更能反映剪切稀化流体的流变特性。     

基于不同黏压模型的空间液体润滑剂弹流油膜厚度的研究

基于牛顿流变模型针对空间液体润滑剂进行等温线接触弹流润滑数值分析。在相同工况下,采用Barus模型、Roelands模型和Yasutomi自由体积黏度模型分别计算空间液体润滑剂的弹流油膜厚度,并与实验结果进行比较。结果表明:Yasutomi自由体积黏度模型更能真实地反应空间液体润滑剂的黏压关系;与其他黏压方程相比,由于Yasutomi自由体积黏度模型在低压区域产生较高的黏度,因而得到较高的油膜厚度。     

空间液体润滑剂弹流牵曳特性的研究

基于Johnson-Tevarrwerk模型对空间液体润滑剂的弹流牵曳特性进行理论研究,并采用高速球-盘式弹流牵曳力试验装置进行相同工况下的试验研究,证明Johnson-Tevarrwerk模型的理论分析很好地反映了空间液体润滑剂的弹流牵曳特性。研究结果表明:入口区的热效应不能忽略,等温牛顿模型不能用于空间液体润滑剂的弹流牵曳特性理论分析;在高滑滚比工况下,空间液体润滑剂弹流牵曳系数的非线性行为非常明显,高黏度空间液体润滑剂的流变行为必须由非牛顿流变模型描述。     

点接触全膜弹流最小油膜厚度的模糊评价

本文通过对点接触全膜弹流最小油膜厚度的分析，并引入了现代机械设计方法中的模糊综合评价方法，对影响点接触全膜弹流最小油膜厚度的各个因素进行了综合分析。     

斜齿圆柱齿轮的弹流润滑模型及油膜厚度研究

本文研究了斜齿圆柱齿轮的弹流润滑问题。通过分析斜齿圆柱齿轮的啮合原理及特点,提出以有限宽线接触正反圆锥滚子作为其物理模型,导出了正反圆锥滚子线接触下的油膜间隙方程,这一结论已在该问题的弹流润滑数值计算中得到了令人满意的应用。本文开展的工作对斜齿圆柱齿轮的弹流研究提供了一种有效的理论分析方法。     

斜齿圆柱齿轮的弹流润滑模型及油膜厚度研究

本文研究了斜齿圆柱齿轮的弹流润滑问题，通过分析斜齿圆柱齿轮的啮合原理及特点，提出以有限宽线接触正反圆锥滚子作为其特点模型，导出了正反圆锥滚子线接触下的油膜间隙方程，这一结论已在该问题的弹流润滑数值计算中得到了令人满意的应用，本文开展的工作对斜齿圆柱齿轮的弹流研究提供了一种有效的理论分析方法。     

流变模型对弹流润滑数值解的影响

采用Carreau流变模型和Ree-Eyring流变模型,研究不同流变模型对黏度较低的Squalane润滑油弹流润滑数值解的影响。分别计算不同卷吸速度、不同滑滚比下Eyring流变模型、Carreau流变模型的摩擦因数,并与试验值进行比较,同时比较Eyring流变模型与Carreau流变模型的摩擦因数、油膜最高温度、中心膜厚及最小膜厚随滑滚比、卷吸速度和最大赫兹压力变化的数值解。结果表明:在滑滚比较小时Eyring流变模型的摩擦因数更加接近试验值,在滑滚比较大时Carreau流变模型的摩擦因数更接近试验值;滑滚比对不同流变模型之间数值解的差别没有影响;随着卷吸速度的增大,Eyring流变模型所对应的膜厚值逐渐高于Carreau流变模型,而油膜最高温度逐渐小于Carreau流变模型;随着最大赫兹压力的增大,Carreau流变模型的油膜最高温度及摩擦因数逐渐大于Eyring流变模型。研究表明,在温和工况下Eyring流变模型更适合Squalane润滑油的弹流分析。     

油膜厚度和变位系数对齿轮啮合刚度的影响研究

采用Грубин提出的弹流润滑入口区分析方法,计算得到渐开线齿轮的整个啮合过程中心油膜厚度的变化趋势。轮齿的啮合变形量的求解基于Weber能量法的理论,给出了详细的计算公式;由于中心油膜厚度的计算基于Грубин的入口区分析方法,Hertz理论在接触变形的求解中仍然成立,且采用Weber推导的近似公式计算。求出中心油膜厚度和啮合变形量后,根据刚度的定义式得到等效啮合刚度。同时进一步分析了不同转速和不同变位系数下的啮合刚度的变化,根据它们的变化趋势,可以更好的为传动系统的平稳提供理论依据。     

滚子修形及凸度量对弹流油膜的影响

本文通过了不同修形和凸度量滚子的静态和动态光干涉图片,分析了修形和凸度量对滚子弹同膜形态和接触压力分布的影响,指出滚子表面和加工精度对滚子的使用寿命有限大影响;对数修形滚子接触副间的压力分布要优于其他两种滚子;对数母线子在给定的工况条件下,存在一个使滚子轴向油膜厚度和接触压力分布最为均匀的量佳凸度量。     

用多重网格法准确计算弹流润滑膜厚度的方法

应用多重网格法求解稳态等温线接触弹性流体动力润滑(EHL)问题,得到了不同工况下使用不同的差分格式并采用不同的网格时的数值解。分析了对Reynolds方程的楔形项使用不同的差分格式时,数值解随着网格层数增加的变化趋势。结果表明:各种常见工况下,对楔形项无论是采用两点差分还是三点差分,随着网格层数的增加,得到的最小膜厚、中心膜厚、第二压力峰值及其出现的位置都会趋于稳定。由数值解归纳出了准确计算中心膜厚与最小膜厚的经验公式。网格层数较少时,将对楔形项分别采用两点差分和三点差分而得到的膜厚代入该公式,即可求出与网格层数较多时的结果非常接近的膜厚值。     

弹流膜厚的测试方法述评

论述了弹性流体动力润滑油膜工测试方法的进展，分析了各种膜厚测试方法的特点及应用范围。     

液体空间润滑剂的现状与发展

空间润滑剂对于宇航飞行器的安全性,可靠性至关重要。综述了液体空间润滑剂的现状及发展,介绍了几种新型液体空间润滑剂的性能、合成方法。     

Effect of Starvation on Traction and Film Thickness in Thermo-EHL Line Contacts with Shear-Thinning Lubricants

The effect of starvation on traction and film thickness behavior in thermo-EHL rolling/sliding line contacts has been studied using full EHL simulations. The simulations employed the free volume equation for viscosity–pressure–temperature relationship and Carreau viscosity model to describe the shear-thinning behavior of the EHL lubricant. The simulation results were used to develop equations for estimating the factors by which the traction coefficient increases and film thickness decreases as a function of the degree of starvation. For the situations involving inadequate lubricant supply at the inlet, these factors can be used to correct the traction coefficient and central film thickness predicted with the assumption of fully flooded condition.     

Elastohydrodynamic lubrication of circular contacts at pure squeeze motion with non-Newtonian lubricants

In this study a numerical method for general applications with non-Newtonian fluids is developed to investigate the pure squeeze motion in an isothermal elastohydrodynamic lubricated spherical conjunction under constant load conditions. The coupled transient modified Reynolds, the elasticity deformation, and the load equilibrium equations are solved simultaneously. Computer simulation is carried out to investigate the effects of flow rheology and operations on the relationship between the pressure and film thickness distributions. The simulation results reveal that the larger the flow index (n), the larger the film thickness and the smaller the maximum central pressure. This results in larger time needed to obtain maximum central pressure. In addition, the elastic deformation is more significant for the lower flow index. Therefore, the smaller the flow index becomes, the greater the difference between the hydrodynamic lubrication (HL) solution and elastohydrodynamic lubrication (EHL) solution becomes.     

The Effect of Shear-Thinning on Film Thickness for Space Lubricants

The authors show that the difference between effective pressure-viscosity coefficients, obtained from film thickness, and coefficients obtained from viscometers for a PFPE space lubricant is substantially the result of shear thinning in the inlet zone of concentrated contact. Flow curves for the PFPE and a multialkylated cyclopentane are presented along with film calculations based on the Carreau model.     

Elastohydrodynamic Lubrication of Circular Contacts at Impact Loading with Generalized Newtonian Lubricants

In this article, pure squeeze elastohydrodynamic lubrication (EHL) motion of circular contacts with power law model lubricant is explored at impact loading. The coupled transient modified Reynolds, the elasticity deformation, and the ball motion equations are solved simultaneously, thus obtaining the transient pressure profiles, film shapes, normal squeeze velocities, and accelerations. The simulation results reveal that the greater the flow index (n), the earlier the pressure spike and the dimple form, while the maximum pressure and the film thickness increase, and the diameter of the dimple, the maximum value of the impact force, the rebounding velocity, and the acceleration decrease. Further, this analysis numerically demonstrates that the contact central pressure for a ball impacting and rebounding from a lubricated surface reached two peaks during the total impact period. As the flow index increases, the primary and the secondary peak increase, and the first and second peaks form earlier; as the total impact time decreases. Moreover, the phase shift between the time of the peak value of the squeeze acceleration and the zero value of the squeeze velocity increase with increasing flow index.     

Experimental Investigation of Elastohydrodynamic (EHD) Film Thickness Behavior at High Speeds

At very high speeds, elastohydrodynamic (EHD) films may be considerably thinner than is predicted by classical isothermal regression equations such as that due to Dowson and Hamrock. This may arise because of viscous dissipation, shear thinning, frictional heating or starvation.

In this article, the contact between a steel ball and a glass disc over an entrainment speed ranging from 0.05 m s^?1 to 20 m s^?1 was studied. Two sets of tests were performed. In the preliminary testing, the disc was driven at speeds of up to 20 m s^?1 and the ball was driven by tractive rolling against the disc, its speed being determined using a magnetic method. After all possible explanations for the reduction in film thickness at high speeds were considered, it was shown that the results, which fall well below classical predictions, are consistent with inlet shear heating at the observed sliding speeds.

Another set of tests was then performed, with both disc and ball driven separately, so that the accuracy of the shear heating theory for different types of oils and at different sliding conditions could be assessed. It was found that the thermal correction factor predicts the trend of film thickness behavior well for the oils tested and is particularly accurate at certain slide–roll ratios (depending on the type of oil). Experimental data were also used to obtain improved coefficients for the correction factor for different types of oil to achieve better prediction of film thickness at high speed throughout the whole range of slide–roll ratios.