圆柱滚子轴承最小油膜厚度计算公式的推导及应用

文中依据道森和希金森线接触等温全膜弹流最小油膜厚度计算公式,推导出圆柱滚子轴承最小油膜厚度计算公式,并将其应用于生产实践中。

油膜比厚对齿轮接触疲劳寿命的影响

通过热弹流润滑数值计算和滚子疲劳实验 ,分析了油膜比厚对齿轮接触疲劳寿命的影响。文中指出增加油膜比厚是提高齿轮接触疲劳寿命的有效手段 ,但并非油膜比厚越大 ,疲劳寿命就越长。当油膜比厚超过某一临界值时 ,疲劳寿命随油膜比厚的增加反而降低。

重型机床的油膜测厚与调整

针对机床静压油膜调整问题进行了论述,重点介绍了其测量调整过程的方法及注意事项。

凹圆弧底从动件圆盘形凸轮机构的设计

从现代机构发展的趋势出发 ,根据赫芝应力理论和弹性流体动压理论 ,提出了在仅要求从动件位移时的凹圆弧底从动件圆盘形凸轮机构。对其理论基础进行了论述 ,建立了该凸轮机构的运动方程 ,分析和讨论了该机构的有关设计参数 ,总结出了该机构的主要工作特点。

考虑粗糙度的直齿圆柱齿轮热混合润滑分析

以渐开线直齿圆柱齿轮为对象,建立了其线接触混合润滑模型,应用多重网格法求解压力、多重网格积分法计算弹性变形、逐列扫描法求解温度以及通过剪应力分析计算非牛顿流体等效粘度等数值技术,求得了几组参数下渐开线直齿圆柱齿轮的热瞬态混合润滑完全数值解,分析了齿轮转速、传递功率、油膜比厚等参数对润滑膜压力和厚度的影响。结果表明随齿轮转速和油膜比厚的增大,中心压力减小,膜厚增大。随传递功率增大,中心压力增大,膜厚减小。

Film thickness effect on the performance of small molecular solar cell

An efficient organic photovoltaic （OPV） cell with an indium-tin-oxide/CuPc/C60/Ag structure has been investigated by changing the film thickness of organic layers. A high olin-circuit voltage （Yoc） of 0.5 V, a short-circuit current density （Jsc） of 5.81 mA/cm^2, and a high power conversion efficiency （ηp） of 1.2% were achieved at an optimum film thickness. The results demonstrate that material thickness is an important factor to cell optimization, especially for maximizing the absorption rate as will as reducing the cell resistance. Experimental results also indicate that the power conversion efficiency increases from 1.2% to 1.54% as a BCP exciton blocking layer of 10 nm is introduced.

模型位姿变化对荧光油膜测厚精度的影响

基于紫外诱导荧光的油膜厚度测量方法已被广泛应用于风洞油流实验,但在动态风洞实验中,承载荧光油膜的模型的位姿变化将会影响油膜厚度测量的精度。在紫外激发光源一次照明与油膜直接成像场景中,对模型位姿变化带来的成像荧光强度误差进行了理论及实验分析。研究了当被测模型发生平移和倾斜时,模型表面的辐照特性、接收荧光强度及成像接收荧光强度的变化,并利用成像荧光强度误差来表征油膜厚度测量精度。分析结果表明,当模型平移时,油膜厚度测量误差与平移距离有关,平移距离越大,误差越大。当模型小角度(-4°~4°)倾斜时,油膜厚度测量的相对误差小于1%。

Simulation and experimental study on lubrication characteristics of vertical hydrostatic guide rails

In order to improve the cutting stiffness,the paper studies the vertical hydrostatic bearing in the slide when a ram is in feed process.The change of the oil film thickness on hydrostatic guide rail and the curve of the oil film thickness in various cutting forces are calculated and a relation model through theoretical analysis method is derived.The pressure field of the guide rail recess is simulated based on the finite volume method and demonstrated through experiments.The study is of vital theoretical significance for the improvement of machining accuracy of numerical control machines and the entire computer numerical control(CNC) equipment and provides valuable theoretical basis for the design of hydrostatic guide rail in engineering practice.

Mixed Lubrication Analysis and Experiment Validation of Internal Combustion Piston Skirt

A mixed lubrication model was established for piston skirt lubrication. The mathematical model developed in this paper incorporates governing equations of motion with average Reynolds equation. This model considers the surfaceroughness and profile. The corresponding computer program can be used to calculate oscillatory motion of piston during the entire trajectory, which has the excellent convergence.In addition, a set of equipment, which adopt the laser induced fluorescent method, was developed to measure the oil film thickness between the piston and the bore.

Simulation and experiment of starting transient flow field of the hydrostatic bearing based on dynamic mesh method

A new method is developed to assess and analyze the dynamic performance of hydrostatic bearing oil film by using an amulets-layer dynamic mesh technique. It is implemented using C Language to compile the UDF program of a single oil film of the hydrostatic bearing. The effects of key lubrication parameters of the hydrostatic bearing are evaluated and analyzed under various working conditions,i.e. under no-load,a load of 40 t,a full load of 160 t,and the rotation speed of 1r/min,2r/min,4r/min,8r/min,16r/min,32r/min. The transient data of oil film bearing capacity under different load and rotation speed are acquired for a total of 18 working conditions during the oil film thickness changing. It allows the effective prediction of dynamic performance of large size hydrostatic bearing. Experiments on hydrostatic bearing oil film have been performed and the results were used to define the boundary conditions for the numerical simulations and validate the developed numerical model. The results showed that the oil film thickness became thinner with the increase of the operating time of the hydrostatic bearing,both the oil film rigidity and the oil cavity pressure increased significantly,and the increase of the bearing capacity was inversely proportional to the cube of the change of the film thickness. Meanwhile,the effect of the load condition on carrying capacity of large size static bearing was more important than the speed condition. The error between the simulation value and the experimental value was 4.25%.

探析粗糙齿面纹理方向对齿轮弹流润滑的影响

首先采用粗糙度轮廓测量分析仪测得了试件表面粗糙度,接着用傅立叶变换非线性逼近法建立了齿面粗糙度函数,然后将此函数叠加到油膜厚度方程中建立了齿轮传动混合弹流润滑模型。基于此模型,在齿轮传动参数固定不变的条件下,通过改变横、纵纹理方向的粗糙度值共进行了46组混合弹流润滑数值计算。结果表明,随着油膜比厚K的增大,纵向条纹下粗糙齿面平均膜厚与光滑齿面平均膜厚比值hav/has逐渐增大最后趋近于1,而横向条纹与之相反逐渐减小最后也趋近与1。最后,借助回归分析理论,建立了hav/has与油膜比厚K之间的定量关系。

The remote sensing inversion theory of offshore oil slick thickness based on a two-beam interference model

Offshore oil slicks are significant for both the monitoring of marine spill accidents and the detection of marine oil resources.The use of remote sensing technology to detect the thickness of oil slicks is a major area of research.The reflected light from oil slicks changes with the thickness of the oil.This is the theoretical basis of research on optical remote sensing of offshore oil slicks.A two-beam interference model that considers the offshore oil slick as a flat plate has been developed in this study.A quantitative remote sensing model which describes a series of processes that use oil slick thickness and reflectance as variables is established.The use of the Fresnel equation to analyze parameters in the model indicated that the key property of the quantitative relationship between the oil slick thickness and reflectance was ultimately the disappearance or extinction of the oil slick.This model has been tested and verified by data from offshore oil slick spectral response experiments.Results showed that the oil slick thickness remote sensing model can be theoretically analyzed and is efficient.The research indicated that the major cause of variations in the spectral response as a function of oil slick thickness was the different light-scattering characteristics.These characteristics can be used in remote sensing applications to identify the different types of offshore oil slicks.The theoretical interpretation of each parameter in this model led to the development of a look-up table of the model parameters which will improve the efficiency of future offshore oil slick remote sensing.

Experimental research on reasonable lubricant quantity for transmission gears used in high-speed train

The transmission efficiency, bulk temperature, integrate temperature, and scuffing load of test gears were investigated by a modified FZG rig. These values were measured in four different oil immersion depths with one kind of potential oil that may be used to replace the current synthetic oil in order to find the reasonable lubricant quantity that meets not only the need of transmission performance but also the need of scuffing resistance for high-speed train gears. For the purpose of evaluating the efficiency of the test gears, there were two sensors added to measure the output torque of testing gears and the compensation torque of motor. The minimum lubrication film thickness at the pitch point was gained through an EHL model. The ratio of the film thickness A was used to identify the friction status when scuffing occurred at different oil levels. The results demonstrated that no matter what kind of the immersion depth was, the minimum film thickness on the pitch point was about 0.1 ~m and the ratio of film thickness was about 1.5 when scuffing occurred. According to the relationship of contact pressure and ratio of film thickness at the pitch point, it was found that the immersion depth of pinion should not be less than one module of the gear when the contact pressure of high-speed train gear at pitch point was about 580 MPa, which was the actual pressure at start-up stage.

直齿圆柱齿轮齿面接触特性分析及齿向修形研究

采用齿向两端梯形修薄和鼓形修形的方式,对某运输机减速器输出端直齿圆柱齿轮齿面进行修形。对修形前后齿轮的接触应力分布、瞬时接触温度和润滑油的油膜比厚进行比较分析,得到了两端梯形修薄和鼓形修形对齿面接触的影响规律,实现了运输机减速器齿轮接触设计优化。结果表明:适当的齿面修形可以减小齿向载荷分布系数,降低齿面接触应力,并能使齿轮瞬时接触温度降低,润滑油的油膜比厚增大,提高齿轮的承载能力。

Blow-by and tribological performance of piston ring pack during cold start and warm idle operations

To reduce the fuel consumption of internal combustion engines, more attention has been paid to the tribological performance of the piston ring pack during the cold start and idle operations. In this research, a numerical model considering the cylinder liner deformation and the piston ring conformability is developed to predict the blow-by, lubrication, friction and wear of the piston ring pack under different operating conditions. The gas flow rate, inter-ring gas pressures, minimum oil film thickness, frictional force and wear load during cold start are calculated and compared with those during warm idle operating conditions. The results show that cylinder liner deformation and piston ring conformability together obviously affect blow-by and other tribological performance. Meanwhile, it is found that friction loss is larger during cold start than during warm idle operating conditions. However, the wear process is more severe during warm idle operation than during cold start. From this research, the blow-by and tribological performance of the piston ring pack during cold start and warm idle operations are understood more deeply.