HKD型航空润滑油本构方程的建立

在自制的试验装置上测量了HKD型航空润滑油油膜拖动力，给出了高剪切率弹流润滑下的Erying特征应力、极限剪切应力、剪切弹性模量的新型航空油流变参数拟合计算式，确定了该油本构方程．并进行了试验验证。试验结果表明：该油在试验条件下表现为粘弹性，理论计算值与试验测量值相当吻合。     

4109航空润滑油流变特性的分析及计算

在改进的拖动力试验装置上，对4109国产航空润滑油进行了不同条件下的拖动系数的测量；通过对试验数据进行回归分析求得了平均极限剪切应力与剪切弹性模址的值并拟合出了经验计算公式。基于TJ弹塑性流变模型对该油的拖动力进行了计算。结果表明拖动力的计算值与试验测量值非常接近，从而证明了对该油流变特性分析的合理性。上述拖动力计算的公式可用于滚动轴承动态设计的软件中。     

含增粘剂润滑油粘弹性的实验研究

本文将系统分析原理引入到对润滑剂本构方程的研究中来,进而提出了一种对本构方程研究的新的实验方法。通过实验得到了含增粘剂润滑油的本构方程的频谱特征图,从而证实了该方法的可行性。将四种增粘剂润滑油在不同增粘剂含量不同温度下的实验数据按照Maxwell流变模型进行回归,得到流变参数(剪切弹性模量)与增粘剂含量、温度之间的关系,给出了回归公式。该公式在一定范围内反映了流变参数的变化规律。     

60钢热压缩变形行为及其变参数Arrhenius本构方程

采用Gleeble-1500型热模拟试验机对60钢进行不同温度(730,750,800,850,900,1 000℃)和不同应变速率(0.01,0.1,1,5,10 s^-1)的热压缩试验,总真应变为0.8,分析了60钢在热压缩过程中的变形行为;引入变参数Arrhenius模型,采用五阶多项式对模型中各参数随应变的变化关系进行拟合,构建出60钢高温变形本构方程,并对方程的精确性进行了评估。结果表明：变形温度越高,应变速率越低,60钢的流变应力越小;在较低温度和较高应变速率下,60钢热压缩变形的软化机制主要为动态回复,在较高温度和较低应变速率下则主要为动态再结晶;建立的变参数Arrhenius本构方程对流变应力的预测值与试验值的拟合相关系数达到0.994 597,说明该本构方程可以较好地描述60钢的高温变形行为。     

2219铝合金热压缩时的流变应力本构方程

采用Gleeble-3180型热模拟试验机对2219铝合金进行单道次热压缩试验,研究了该铝合金在温度为200~350℃、应变速率为0.1~10.0s-1条件下的流变行为,建立了2219铝合金热压缩时的流变应力本构方程,并进行了试验验证。结果表明:2219铝合金的流变应力随应变速率的增大或变形温度的降低而增加;由Fields-Backofen本构方程计算得到的2219铝合金应力的变化规律与试验得到的相同,且应力计算值与试验值的相对误差小于5%,该本构方程可以较准确地描述2219铝合金的高温流变行为。     

基于变形特征值及特征状态参数的金属材料高温变形本构方程

基于变形特征值(σss,σp,εp,εr)及特征状态参数(LM,Z,erf,MTS参数),建立了一个描述金属材料高温变形的本构方程,包括高温变形过程方程和特征参数方程,并通过商业纯铝、无氧铜、超低碳钢的高温压缩试验,对该本构方程的计算准确度进行了验证。结果表明:使用该本构方程计算得到的纯铝和超低碳钢的高温变形结果与试验结果吻合性较好,其峰值应力计算值与试验值的相对误差均小于10%,但无氧铜的却达到了15%,模拟计算精度略低;该本构方程可用于预测纯铝和超低碳钢在热加工变形条件下的流变应力。     

低温工况润滑脂流变特性及本构方程研究

润滑脂流变学行为与温度紧密相关,而流变行为决定润滑脂的本构方程。首先分别在不同温度工况下进行流变试验获得润滑脂流变学特性,并对低温工况进行研究;其次,基于Herschel-Bulkley、Power Law与Bingham本构方程对流变数据进行回归分析;最后,基于三种本构方程采用CFD方法深入分析润滑脂在管内的压力损失、粘度分布及速度分布规律。结果表明:在低剪切速率下,低温工况的剪切应力出现峰值,且润滑脂承受的最大剪切速率减小;不同工作温度下,三种本构方程回归精度均大于92%;Herschel-Bulkley本构方程粘度与速度计算结果均小于Power Law与Bingham本构方程;基于三种本构方程计算的速度在管道中心均出现明显的核流区域;Herschel-Bulkley本构方程压降计算结果最小。     

FV520B马氏体不锈钢的热变形行为和本构关系

采用Gleeble-3500型热模拟试验机对FV520B马氏体不锈钢进行了单道次等温热压缩试验,研究了该不锈钢在变形温度为850~1 150℃和应变速率为0.005~5.000s~(-1)条件下的热变形行为,根据应力-应变曲线并基于Zener-Hollomon参数和Arrhenius双曲正弦方程,建立了该不锈钢在高温压缩时的本构方程,并对该本构方程进行了修正和试验验证。结果表明:FV520B马氏体不锈钢的流变应力随着变形温度的升高或应变速率的减小而降低;在0.005s~(-1)、1 000~1 150℃或0.050~5.000s~(-1)、1 075~1 150℃条件下,该不锈钢发生了较明显的动态再结晶;在0.005s~(-1)、850℃,5.000s~(-1)、850℃和5.000s~(-1)、925℃条件下,由建立的本构方程计算得到的流变应力与试验值存在较大的误差;对本构方程进行修正之后,流变应力的预测值与试验值的相关系数为0.997 88,平均相对误差为2.225%,修正后的本构方程可以准确地预测该不锈钢的热变形流变应力。     

Fe-3.0%Si-0.09%Nb取向硅钢的高温流变应力

通过热模拟试验机测定了Fe-3.0%Si-0.09%Nb取向硅钢在不同变形温度和应变速率下的真应力-真应变曲线,分析了变形参数对流变应力的影响规律,通过线性回归分析计算出该取向硅钢的热变形应力指数n以及变形激活能Q,并构建了流变应力本构方程。结果表明:该取向硅钢的真应力-真应变曲线为动态回复型,其变形时的流变应力主要取决于变形温度和应变速率;当应变速率一定时,流变应力随着变形温度的升高而减小;变形温度一定时,流变应力随着应变速率的增大而增大;用构建的Fe-3.0%Si-0.09%Nb取向硅钢流变应力本构方程计算得到的流变应力与通过试验测得的结果相吻合。     

基于Johnson-Cook模型构建M50NiL齿轮钢的流变应力本构方程

利用Gleeble-3500型热模拟试验机,研究了M50NiL齿轮钢在变形温度为1 123.15~1 423.15K、应变速率为0.005~10s-1条件下的变形行为,并对实测流变曲线进行了摩擦修正;基于应变速率和变形温度对金属高温变形的耦合效应,建立了基于Johnson-Cook(J-C)模型的耦合流变应力本构方程并进行了验证。结果表明:对试验钢流变曲线摩擦修正后,得到的流变应力比实测值小;经变形参数耦合修正后的J-C耦合本构方程计算得到的流变应力与摩擦修正后流变应力的平均相对误差为3.08%,其预测精度高于传统J-C本构方程(平均相对误差为14.31%)的。     

CONSTITUTIVE EQUATION OF A NEW AVIATION LUBRICATING OIL

The traction of a new aviation lubricating oil was measured on a self-made test rig. The calculating formulae of the rheological parameters of the oil such as Erying stress, limiting shear stress and shear elastic modulus were obtained under the condition of the high shear strain rate in elastohydrodynamic lubrication(EHL). The constitutive equation of this oil was determined and verified by test The results of experiments show that the behavior of the new aviation lubricating oil behaves as visco-elastic fluid and the theoretical value agrees fairly well with the measured data, which implies that the constitutive equation of this oil is correct and feasible.     

Lubricant oils additivated with polymers in EHD contacts: Part 1. Rheological behaviour

This paper reports on the influence of a polymer additive on the traction behaviour of a mineral oil investigated using a two‐disc machine at different temperatures and contact pressures. A semi‐empirical approach was used for determining the effective lubricant rheological parameters ‐ the elastic shear modulus, the viscosity of the lubricant, and the limiting and Eyring stresses ‐ in elastohydrodynamic contacts. Using this approach, the effect of polymer concentration on the rheological parameters that appear in both the Johnson‐Tevaarwerk and Bair‐Winer models was quantified. The influence of operating conditions, such as pressure, oil temperature, and polymer concentration, on the traction coefficient, limiting shear stress (from the Bair‐Winer model), Eyring stress (from the Johnson‐Tevaarwerk model), shear modulus, and apparent viscosity was also investigated.     

ON THE TRACTION BEHAVIOR OF 4109 CHINESE AVIATION LUBRICANT

0INTRODUCTIONElastohydrodynamic lubrication(EHD), which mainly studies film thickness, pressure distribution, and lubrication traction of tribopairs through nominal point or line contacts, is one of the important research fields of tribology near upon forty years. The traction behavior of lubricants that has great influence upon dynamic properties of rolling bodies plays a dominant role in the overall performance and life of rolling bearings in which the traction forces at the rolling e…     

A non-averaging method of determining the rheological properties of traction fluids

Traction machines have been frequently used to study the rheological responses of lubricants in elastohydrodynamic lubrication (EHL) contacts. Fundamental properties are inferred from EHL traction measurements based on the average pressures and temperatures in the contact. This average approach leads to uncertainty in the accuracy of the results due to the highly nonlinear resonse of the fluid such as viscosity to both pressure and temperature. A non-averaging method is developed in this paper to study the elastic and plastic properties of traction fluids operating in EHL contacts at small slide-to-roll ratios. A precision line-contact traction rig is used to measure the EHL traction at a given oil temperature and Hertz pressure. By choosing a sensible pressure-property expression, the parameters of the expression can be determined through the initial slope and peak traction coefficient of the traction measurements. The elastic shear modulus and the limiting shear stress of the lubricant corresponding to a single pressure can then be calculated for a range of pressures and temperatures of practical interest. Two high-traction fluids are studied, and their elastic moduli and limiting shear stresses presented.     

Experimental and computational investigation of the traction coefficient of a ball traction drive device

Traction drive is a new kind of drive manner in which the power is transmitted by a thin oil film between transmission elements. This paper describes a ball traction drive device. The quasi-dynamics analysis was carried out for the transmission components of the ball traction drive device. The traction coefficients of oils Ub2 and HH-20 were calculated respectively with different rheological models. The elastohydrodynamic lubrication (EHL) film thickness and the traction coefficient between traction drive elements were measured. The results of the calculations are consistent with experiments.     

A fast method for the numerical solution of thermal-elastohydrodynamic lubrication problems

The paper presents a method for the numerical solution of the elastohydrodynamic lubrication problem in line contacts, which includes thermal and rheological effects. The method consists in alternating repeatedly the solution of a generalised Reynolds equation and of the energy equation. In both cases use is made of a finite-element technique. Since the method proves to be very fast, a computer program has been developed which runs on common personal computers. Results (presented for two values of load parameter and for a range of values of slip/roll ratio up to 50%) show that thermal and non-Newtonian effects can strongly influence the film thickness and are essential for a reasonable evaluation of traction force. In this connection, the dimensionless parameter K (which depends on the equivalent curvature radius as well as on thermal conductivity and other material parameters) appears to be determinant.     

基于有限差分法的径向滑动轴承油膜压力分布计算

滑动轴承广泛应用于旋转机械中,其静动态参数对旋转机械的运转有很大影响。确定滑动轴承的静动态参数依赖于轴承的油膜压力分布,Reynolds方程是油膜压力计算的基础。对于具体轴承参数计算,传统方法是利用已知的给定偏心率和宽径比下的轴承静动态参数进行曲线拟合,通过反推实际轴承的偏心率和偏位角,然后进行压力分布计算。这种逆运算不太方便。基于有限差分法,采用MATLAB软件编程计算,利用实际轴承已知外力和宽径比直接求解完整二维流动Reynolds方程得到油膜压力分布曲线,进一步利用改进方法设计计算实际轴承参数,取得较好的计算精度,使圆瓦轴承参数计算更为简便。     

The non-Newtonian effect of temperature on hydrodynamic lubrication failure

The influence of temperature on the rheological characteristics of lubricants has been investigated by analysing the viscosity-temperature relationship and energy equation of lubricants. The constitutive equation, which describes the non-Newtonian properties of lubricants caused by thermal effects, is founded and coupled with equations of continuity and momentum of the fluid to calculate the load-carrying capacity in hydrodynamic lubrication. The numerical solutions show that lubricants have ultimate shear strength as a result of the non-Newtonian effect of temperature, which leads to the oil film having limiting load-carrying capacity. The mechanism of film failure in hydro-dynamic lubrication is also studied preliminarily in this paper.