机械端面密封主要参数的计算（三）：性能参数（续）与计算示例

机械端面密封主要参数的计算（三）──性能参数（续）与计算示例石油大学（华东）顾永泉２．２摩擦系数─—流体摩擦系数人与接触摩擦系数人机械密封热量、传热、热变形、功耗和冲洗量的计算均需知道摩擦系数。要正确选用摩擦副的摩擦系数，除了模拟试验和材料试验外，还...     

基于Visual C^＋＋的机械密封计算分析系统

把面向对象的思想和有限元法相结合,编写了机械密封计算分析软件系统（MFSCAD）。该软件系统采用图形交互式数据输入,可对机械密封环温度场,密封环变形和接触端面摩擦系数进行计算分析,并将计算分析结果以图形和数据形式输出,为机械密封机理研究和工程设计提供技术支持。     

基于VisualC~(++)的机械密封计算分析系统

把面向对象的思想和有限元法相结合 ,编写了机械密封计算分析软件系统 (MFSCAD)。该软件系统采用图形交互式数据输入 ,可对机械密封环温度场、密封环变形和接触端面摩擦系数进行计算分析 ,并将计算分析结果以图形和数据形式输出 ,为机械密封机理研究和工程设计提供技术支持     

大直径直孔套管起拔力仿真计算

目前套管起拔力分析均是针对于岩土中简化计算,得出的起拔力与真实情况有很大差别。基于此,应用非线性有限元软件,分析计算真实复杂工程状况下即边注浆加固边起拔套管的拉拔力,得出桩浆间摩擦系数对套管起拔力影响最大,摩擦系数为0.2与摩擦系数为0.6对应的套管起拔力峰值相差高达70000N;摩擦系数越小,套管起拔过程越平稳;套管壁厚一般选取10mm对应较小的套管起拔力;仿真计算为工程上大直径套管起拔力的确定、动力选取提供了一定理论指导。     

管状机织物与管子之间的摩擦系数测量系统

为了实现管状机织物与管子之间摩擦系数的测量,设计了一套管状机织物在管子上抽拔过程的摩擦系数测量系统。首先通过施加弹性元件的方法,在实际使用工况下测试出附加摩擦力,再测试计算出弹性元件在圆管上产生的正压力,根据计算公式μ(摩擦系数)=F(摩擦力)/N(正压力)直接计算出摩擦系数;同理,通过弹性气压法测出管织物与管内壁的摩擦系数。然后使用所测量的摩擦系数在LS-DYNA分析软件中建立有限元模型进行计算,并与试验数据进行对比分析。最后,针对该摩擦系数测量系统在探月三期工程中月壤钻进取芯组件上的应用效果进行了实验检测与仿真计算对比。结果表明该系统测得的管状机织物在管子上抽拔过程的摩擦系数准确可靠,为有限元分析模型中摩擦系数的确定提供了一种有效的测量方法,满足月壤取芯组件的应用要求。     

一种V带传动当量摩擦系数计算的修正方法

V带传动的当量摩擦系数体现了V带传动比平带传动具有更高的承载能力。文中对教材上关于V带传动当量摩擦系数的计算公式进行了修正,推导出了当量摩擦系数计算的通用公式。根据侧面摩擦力方向角的大小,V带在主、从动轮滑动弧和静弧上的当量摩擦系数均可通过该公式计算,为带传动的工作原理提供了有益补充。     

考虑表面粗糙度和径向锥度的机械密封混合摩擦计算模型

本根据雷诺方程和弹性固体接触模型,提出了一个简单实用的机械密封混合摩擦计算模型,并给出了该模型的计算流程和计算实例,计算结果表明,机械密封端面压力分布呈凸抛物线状,增加密封端面锥度可降低摩擦系数。     

摩擦系数—运动粘度的多层神经网络计算模型研究

建立了预测磨损自补偿状态下润滑剂运动粘度对４５钢／锡青铜副摩擦特性的影响规律的ＢＰ神经网络模型,该网络可较准确地预测润滑剂粘度对摩擦副摩擦系数的影响规律,为摩擦学设计的程序化计算和分析提供方便且有效的工具。     

无叶扩压器壁面摩擦系数的计算和讨论

本文通过离心压缩机无叶扩压器内三元边界层流动的分析、计算和实验对比,对几种壁面摩擦系数的计算方法进行了讨论,同时研究了平行壁及非平行壁径向无叶扩压器中摩擦系数的变化规律,及其对扩压器性能的影响。     

双圆弧槽摩擦片摩擦系数影响因素分析及实验测试

湿式换挡离合器摩擦片摩擦系数受压力、转速和润滑流量等多种工况参数影响,研究摩擦系数随工况参数的变化规律对于离合器设计具有重要意义。以铜基粉末冶金双圆弧摩擦片为研究对象,对摩擦系数的影响因素进行了分析,利用Simulink搭建了油膜厚度仿真模型,计算了摩擦副实际接触面积的大小,并讨论了实际接触面积对摩擦系数的影响;通过实验采集转矩值,计算得到了平均摩擦系数;选择研究较少的双圆弧摩擦片进行分析和实验研究。结果表明:控制油压在(0.3~0.7)MPa范围内,稳定磨损期的动摩擦系数随压力增加而减小,控制油压低于0.4MPa时摩擦系数随转速差和润滑流量单调递增,反之单调递减;台架试验测试的静摩擦系数与厂家给定值略有差别,论文研究结果对湿式离合器工程设计具有一定参考意义。     

Effect of variable friction coefficient on contact tractions

Friction coefficient plays an important role in determining the contact tractions and consequently the stresses that drive damage mechanisms in components subjected to fretting fatigue. Friction coefficient evolves to different magnitudes at different points in the contact interface. Effect of this spatial variation in friction coefficient on the shear distribution for contacts involving similar isotropic materials has been presented in this paper. Full sliding tests have been conducted to obtain friction coefficient as a function of sliding distance. Well characterized set of experiments to determine the average friction coefficient in fretted specimens is briefly discussed. Existing analysis for obtaining the shear traction for arbitrary smooth profiles has been modified to take the variation of friction coefficient from one point to another into account. Using this analysis, spatial variation of friction coefficient in fretted specimens has been obtained. It has been found that using a constant friction coefficient (equal to the slip zone friction coefficient) throughout the contact zone is a good enough approximation in most of the cases. However, in some cases, when the slip zones extend into regions where the friction coefficient has not reached the asymptotic value, actual distribution of friction coefficient gives a different shear stress distribution as compared to a constant slip zone friction coefficient.     

球轴承滑动摩擦系数的研究

在简述球轴承摩擦的基础上，对钢球与沟道接触的滑动摩擦进行了研究，推导出了其滑动摩擦系数的计算公式，指出了阿蒙顿-库仑(Amontons-Coulomb)摩擦定理的缺陷，否定人们通常认为给定材料的两接触物体滑动摩擦系数是一常量的观点，证明了钢球-沟道接触的滑动摩擦系数是一个变量，为科学地确定球轴承现代设计中钢球与沟道接触的滑动摩擦系数，使人们对普遍物理意义上的滑动摩擦更深入地进行认识，提供了科学的依据。     

润滑条件下铝合金板成形模拟中摩擦模型的研究

对润滑条件下铝合金薄板筒形件拉深成形过程进行了工艺分析，在作出一些简化和假设的基础上，建立了基于流体润滑的筒形件拉深成形过程摩擦模型；将该模型运用到板料成形过程有限元分析中，计算出筒形件成形时摩擦系数动态变化的数值；开发出基于探针测试的铝合金板温成形动态过程摩擦测试系统，并对筒形件成形时的摩擦系数进行了测试实验。计算结果与实验数据表明，板料成形过程中的摩擦系数不是一个常数，随着凸模行程的增加，摩擦系数具有增加的趋势。     

Effects of friction conditions on the formation of dead metal zone in orthogonal cutting – a finite element study

Abstract

A numerical study of the effects of friction conditions on the formation of dead metal zone (DMZ) is presented. The friction conditions are classified as three different cases in the form of coefficient: (1) constant coefficient of friction, (2) “smooth” and “sharp” change of the friction coefficient and (3) time-dependent friction coefficient. These friction cases are numerically investigated using the finite element (FE) code ABAQUS/Explicit. A FE model based on the arbitrary-Lagrangian–Eulerian approach is developed to simulate the cutting process and investigate the influences of the friction conditions. The simulated results, for a wide range of friction conditions, are obtained, analyzed and compared with previously published experimental/numerical data. It has been found that the friction coefficient has a direct effect on the amount and shape of DMZ, the sharp change of coefficient has a larger effect on the DMZ formation than the smooth one and the formation of DMZ is more determined by the value of the friction coefficient than its duration.     

Identification of a friction model—Application to the context of dry cutting of an AISI 1045 annealed steel with a TiN-coated carbide tool

The characterization of friction coefficients at the tool-chip-workpiece interface remains an issue. This paper aims to identify a friction model able to describe the friction coefficient at this interface during the dry cutting of an AISI1045 with TiN coated carbide tools. A new tribometer has been designed in order to reach relevant values of pressures and sliding velocities. This set-up is based on a modified pin-on-ring system. Additionally a numerical model simulating the frictional test has been associated in order to quantify average friction coefficients around the spherical pin, from the standard macroscopic data provided by the experimental system. A range of cutting speeds has been investigated. It has been shown that the friction coefficient is very much dependant on the sliding velocity. A new friction model has been identified based on the average local sliding velocity.     

Friction of ultrathin Si,F-containing coatings

The friction of an ultrathin coating (~5 nm) formed as a result of the modifier segregation towards the surface of modified epoxy polymer in the form of multiple short chains of Si, F modifier has been investigated in a range of loads from 0.1000 to 0.0005 N. During the investigation of the reverse friction of ceramic (Al₂O₃) ball on the coating, the sharp decrease in coefficient of friction at a load of less than 0.002 N has been shown, which is probably caused by the change in the mechanism of friction during the transition of friction to the zone of a self-lubricating coating. Under these conditions, the difference between the static coefficient of friction (stop effect) and dynamic coefficient of friction increases.     

The Frictional Properties of Newtonian Fluids in Rolling–Sliding soft-EHL Contact

A combined experimental and numerical study has been carried out to explore friction in rolling–sliding, soft-EHL contact. Experimental work has employed corn syrup solutions of different concentrations in water to provide a range of lubricant viscosities and has measured Couette friction in mixed rolling–sliding conditions over a wide range of entrainment speeds. A Stribeck curve has been generated, ranging from the boundary to full film, isoviscous-elastic lubrication regime. In the latter regime, friction coefficient is approximately proportional to the product of (entrainment speed × viscosity) raised to the power 0.55. Numerical solution of the isoviscous-elastic lubrication regime has been used to derive predictive equations for both Couette and Poiseuille friction in circular, soft-EHL contacts. This shows that in soft-EHL the Poiseuille or “rolling” friction can have magnitude comparable to the Couette friction. The calculated Poiseuille friction coefficient can be predicted from non-dimensional load and speed using a simple power law expression similar to that used for film thickness. However accurate prediction of calculated Couette friction coefficient requires a two-term power law expression. Comparison of experimental and numerical Couette friction coefficients shows quite good agreement between the two, with a similar non-dimensional speed dependence, but slightly lower predicted than measured values.     

Measurement of the friction of paper by the strip-on-drum method

The friction between paper surfaces has been studied in a strip-on-drum geometry, under quasistatic and slow sliding conditions. The method provides a better simulation of some practical applications than other more widely used tests. The mechanics of the test have been analysed for two cases: with constant coefficient of friction; and with the friction force related to normal pressure by a power law. The behaviour of four different types of paper was examined. In all cases, the coefficient of friction of the sample fell with repeated sliding; this was associated with progressive damage to the paper surface, and has implications for the design of standard friction test methods for paper. The coefficient of friction (COF) also depended significantly on the contact pressure, in a way that can be correlated with the relative compressibilities of the different paper structures. The pressure dependence of friction, at low pressures, was accurately modelled by a power-law relationship.     

Effect of treads pattern of rubber floor mat on the friction coefficient

Millions of workers all over the world spend most of the working time on their feet, walking and standing rather than sitting. Slips and falls are the cause of major accidents and loss of the time at work. The Health and Safety Executive continually prompts on the need to avoid potential risks, especially where the floor surface is slippery or hazardous. In the present study, the effect of topographic orientation and tread pattern of the tested rubber specimens on the friction coefficient has been investigated. Experiments have been carried out using a test rig designed and manufactured to measure the friction coefficient between the footwear sliding against eight types of commercial rubber mat products (floors). Finite element simulations have been conducted using SIMULIA ABAQUS FEA to study the effect of grooves orientation of specimens sliding against rubber sheet on the friction coefficient. The results showed that tread pattern and grooves orientation significantly affect the friction coefficient. The effect of groove width on friction was observed, where the surface of wider groove obtained lower friction coefficient values than those of narrower one in the same sliding direction (parallel direction). The friction coefficient in the parallel direction obtained higher values than that observed for those in the transverse direction for surfaces with narrower groove patterns. Finite element simulations showed anisotropic friction properties depending on the contact pressure.