电子设备结构内界面接触热阻的影响因素分析

针对电子设备内热传递过程中存在的接触热阻问题,充分考虑了结构件材料的热和力学性能参数、间隙介质的热参数、气压(环境压力)、接触表面特征参数、加载压力、材料微硬度等众多因素的影响,依据非完全贴合表面的接触热阻模型进行计算分析。并重点分析了外界加载压力和表面粗糙度对该接触热阻值的影响,为电子设备结构的热传递优化提供理论基础。     

降低固-固界面接触热阻研究

接触热阻是影响固-固界面之间传热的重要因素,文中研究了界面压力、接触面粗糙度、接触面平面度和在固-固界面添加导热介质等方式对固-固界面接触热阻的影响。研究显示在低压力水平和四角加压的方式下,降低接触面粗糙度和在接触面之间填充导热介质可以有效降低固-固界面的接触热阻。     

基于接触热阻的主轴热特性有限元分析

在考虑了轴承、主轴和箱体接触区域的接触热阻影响的基础上,利用大型有限元分析软件ANSYS对某型号机床的主轴系统进行了温度场建模,并综合分析了整个系统的热态特性.论述了热源和边界条件等因素的计算方法,考虑了以往建模时较少考虑的接触热阻因素,对模型在有、无热阻两种情况下进行了分析、对比.对比结果表明,接触热阻对系统的影响是显著的,对于精密机床的研究,建模时不应忽略这一重要因素.     

基于田口方法的PEEK/AISI 630在海水环境中的磨损敏感性试验研究

海水液压元件摩擦副材料的表面粗糙度、接触载荷、滑动速度等因素对其摩擦磨损性能具有重要影响,而各因素之间又存在着摩擦磨损交互作用。基于田口方法对PEEK/AISI 630摩擦副进行摩擦磨损试验设计,研究了摩擦副的表面粗糙度、接触载荷和滑动速度对其磨损交互性、敏感性的影响。采用极差分析确定3因素在PEEK/AISI 630摩擦学行为中的相互关系和影响主次顺序;利用方差分析得到3因素对摩擦系数、磨损率影响的显著程度和贡献率;最后,对试验数据进行回归分析,从而获得表面粗糙度、接触载荷、滑动速度分别与摩擦系数、体积磨损量之间的经验公式(又称回归方程),并对回归模型进行可靠性分析。     

表面粗糙度对轴承振动的影响

利用Fokker-P lanck方程分析表面粗糙度对滚动轴承振动的影响,结果表明,在表面凸峰处接触振动很小,而在表面凹陷处接触振动的振动速度、加速度很大。表面粗糙度对高速轴承的振动影响较低速轴承要大;表面粗糙度Ry对接触振动影响不大;接触载荷对接触振动影响很显著,接触载荷越大,在凹陷处的接触振动加速度变化越大。     

基于粗糙接触的指尖密封热分析

提出了基于粗糙表面接触热阻的修正计算方法和考虑粗糙峰高度正态分布截断影响的修正系数拟合计算公式。根据等效的概念,将指尖密封系统中各接触副的接触热阻通过"圆柱桥"模型加以描述,在此基础上建立了指尖密封系统的有限元热分析模型。通过有限元计算,获得了指尖密封系统的温度场分布,以及系统最高温度随接触副表面粗糙度、转子过盈量和系统上下游气体压差等结构工况参数的变化规律。这一工作对于指尖密封的深入研究和设计具有较高的参考价值。     

固体材料的接触传热

本文叙述了接触热阻的试验设备及其测定结果。分析了各种参数（载荷、接触表面温度、填充剂种类及其压力等）对接触传热的影响。对接触表面的变形规律作了初步探讨,提出了接触热阻的一般表达式。     

角接触球轴承油膜热阻及传热影响研究

角接触球轴承广泛应用于电主轴等高速轴系,研究角接触球轴承的润滑油膜热阻计算方法以及接触油膜热阻对轴承温度场分布的影响,对于改善角接触球轴承的工作条件和提高电主轴等轴系的运行稳定性有重要的意义。运用平板模型,分析计算了角接触球轴承的油膜热阻,探讨了影响油膜热阻的主要因素;采用有限元方法分析了角接触球轴承的温度场,研究了接触油膜热阻对轴承温度场分布的影响。结果表明:轴承转速、载荷和润滑油的动力粘度对油膜热阻有较大影响,接触油膜热阻对轴承的散热和温度场分布影响很大。     

考虑结合面接触热阻的角接触球轴承温度场分析

在对滚动轴承摩擦学及传热学进行分析的基础上,计算了角接触球轴承的摩擦热,建立了考虑结合面接触热阻的角接触球轴承热传递模型。利用ANSYS获得了轴承的温度场,对比了在考虑接触热阻和不考虑接触热阻两种情况下角接触球轴承温度场的分布情况。结果表明:考虑接触面之间的接触热阻时,轴承的温度要略高于不考虑接触热阻时,且结合面的两表面之间存在温差。     

内燃机主轴承摩擦功率损失的影响因素

研究了影响主轴承摩擦功率损失的影响因素,包括轴承表面粗糙度、润滑油温度、曲轴转速、轴颈间隙和供油提前角,同时分析各影响因素对内燃机主轴承的影响。分析所用物理模型为直列六缸内燃机,其数学模型主要依据有限差分法与欧拉法求解雷诺方程,润滑油膜接触通过在时域内压力平衡迭代计算。对内燃机曲轴主轴承摩擦功率损失影响因素进行了探讨,计算结果表明,在内燃机零部件设计阶段应充分考虑轴承间隙以及表面粗糙度对摩擦功率损失的影响。     

渐开线直齿轮瞬态微观热弹流润滑分析

考虑了瞬态效应、轮齿表面油膜温度场和轮齿表面纵向粗糙度等因素,对渐开线直齿圆柱齿轮的弹流润滑问题进行研究。载荷由双齿或单齿承担,根据实际载荷谱简化的轮齿载荷曲线,利用压力求解的多重网格法和弹性变形求解的多重网格积分法以及温度求解的逐列扫描技术,得到渐开线直齿轮瞬态微观热弹流润滑问题的完全数值解,讨论了轮齿间油膜的厚度、压力、温度沿啮合线的变化规律。数值计算结果表明,齿轮表面纵向粗糙度对轮齿间油膜的压力、膜厚、温升都有较大影响。考虑轮齿表面粗糙度后,油膜压力和温升明显增大,并随压力的增加而影响越来越显著,粗糙峰使油膜压力分布和温度分布产生振荡,轮齿表面的粗糙峰对摩擦因数影响较小,摩擦因数和最高温升在节点两侧最大。     

Surface topography and properties of frictional contacts

The influence of surface topography on contacting solids is considered. The rough surface model is suggested and is used for the calculation of some tribological contact characteristics. A rough surface is modelled by a set of asperities of regular shape (wedge, cone, cylindrical, spherical segment), of differing height. A simple height distribution function and asperity shape function are used. These functions may be integrated analytically in further calculations.The surface model is used for calculation of one of the main contact parameters - real contact pressure (or real contact area) and other principal contact parameters, such as deformation, number of contact spots, average spot area, average distance between contact spots and intercontact gap.It is shown how the above parameters may be used for the calculation of such operational contact characteristics as friction coefficient, wear rate and electrical and thermal resistance.     

粗糙表面热弹塑性接触问题的无网格法

建立可考虑屈服应力温度相关的粗糙表面热弹塑性接触无网格法数值计算模型.研究摩擦力和不同热输入情况下圆柱体与弹塑性平面的接触力学特性,探讨摩擦热效应对表面温升、接触压力和接触面积的影响.结果表明在考虑剪切摩擦力作用后,弹塑性接触压力分布不再关于接触区域中轴线对称而出现了"塌陷"现象.通过无网格法解与有限元法解比较发现不恰当的有限元网格划分会造成接触压力的数值震荡,而无网格法可避免这一现象的发生.发现忽略温度相关效应将高估最大接触压力而低估相应外载荷下产生的接触面积.     

考虑微凸体水平距离分布及相互作用的结合面法向接触刚度建模

在涉及微凸体侧接触的粗糙表面接触建模过程中,通常需要假定微凸体之间侧接触的角度分布规律。提出一种考虑微凸体水平距离分布及相互作用的结合面法向接触刚度建模方法,该方法不再需要假定角度分布规律,而是基于首次发现的单个粗糙表面微凸体水平距离正态分布规律,根据统计学理论进行考虑微凸体相互作用的结合面法向接触刚度建模。对模型进行数字仿真发现：结合面法向接触刚度与接触载荷均随着微凸体水平距离标准差的减小而增大,并且考虑微凸体相互作用会使得结合面的法向接触刚度减小。结合面法向接触刚度随弹性模量的增大而减小,随材料硬度的增大而增大。通过有限元仿真结果与模态试验结果对比可知,基于模型的有限元仿真前三阶固有频率与试验所得结果基本吻合,并且误差相对GZQ模型更小。旨在通过研究单个粗糙表面微凸体水平距离分布,突破侧接触建模时接触角度分布函数仍需假设的理论瓶颈,为更加准确地预测结合面接触特性奠定基础。     

Computational micro- and macroscopic models of contact and friction: formulation, approach and applications

This paper is dedicated to new asperity-based constitutive models of contact interfaces. These models have been obtained through a combination of finite element analysis of surface asperities and statistical homogenization techniques, to predict macroscopic, phenomenological behavior of the interface. This new approach has generalized the existing asperity-based models of contact and friction by considering realistic, complex shapes and mechanical properties of surface asperities, as opposed to previous simplified analytical solutions. This has been achieved by application, at the stage of asperity modeling, of the finite element method, which takes into account arbitrary shapes of asperities, non-linear material properties, molecular-range adhesion forces, and sliding resistance on the contact surface. The h–p adaptive mesh refinement techniques, adaptive timestepping and other adaptive methods are used to assure high accuracy of the solution. The result of this development is a new family of constitutive interface models, consistent with surface micromechanics and applicable to studies of static and dynamic friction phenomena. They are also extendible to calculation of thermal or electrical resistances, wear modeling, and other applications. This paper presents the theoretical formulation, numerical methodology and sample models of contact, adhesion and friction obtained through these homogenization techniques.     

Thermomechanical coupling of rough contact asperities sliding at very high velocity

A model has been developed to study dry friction for a steel tribopair for a large range of sliding velocity. From the topology of two parts in contact, a true contact surface is defined as a set of asperities. Each adhesive junction is associated to a local heat source in the thermal problem that is solved by Green׳s function techniques. The mechanical problem is treated by considering the adiabatic shearing process of these asperities. The coupling of thermal and shearing effects is then performed by using a homogenisation approach. Outcomes, such as the average thermal response on the contact area, appear to be in good agreement with those of the literature. Velocity dependence of the heat flux distribution between parts in contact is highlighted. The temperature profile in both solids in contact, as well as the local shear stress field, is determined at any friction time.     

材料属性温度相关热弹塑性接触问题研究

应用有限元方法建立了可考虑屈服应力温度相关效应的粗糙表面热弹塑性接触模型。研究了摩擦力和不同热输入情况下圆柱体与弹塑性平面的接触力学特性。求解了考虑屈服应力温度相关效应的粗糙表面热弹塑性接触问题,探讨了摩擦热效应对表面温升、接触压力、平均间隙及接触体应力分布的影响。提出了考虑热膨胀系数温度相关效应的热弹塑性接触模型。通过刚性圆柱体与半无限大平面的热弹塑性接触研究了热膨胀系数温度相关效应对接触体应力分布的影响。
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The correlation between surface temperature and the number of metallic contacts in the concentrated contact

Results of measurements of local changes in electrical resistance in a concentrated contact and contact surface temperatures determined with the aid of a thin-layer transducer are presented in this paper.Good agreement between the oil film thickness corresponding to the measured inlet temperature and the thickness predicted by the thermal reduction factor given by Murch and Wilson has been found. It has also been found that there exists a strong correlation between the number of individual metallic contacts (asperities) in the contact zone and the surface temperature in the inlet zone as well as the maximum surface temperature in the contact. This dependence may be described by a power function for which the exponent depends only on rolling velocity; however, the coefficient is also a function of sliding velocity.     

Surface separation and contact resistance considering sinusoidal elastic–plastic multi-scale rough surface contact

The current work considers the multi-scale nature of surface roughness in a new model that predicts the real area of contact and surface separation as functions of load. This work is based upon a previous rough surface multi-scale contact model which used stacked elastic–plastic spheres to model the multiple scales of roughness. Instead, this work uses stacked 3D sinusoids to represent the asperities in contact at each scale of the surface. By summing the distance between the two surfaces at all scales, a model of surface separation as a function of dimensionless load is obtained. Since the model makes predictions for the real area of contact, it is also able to make predictions for thermal and electrical contact resistance. In accordance with concerns in previous works that the iterative calculation of the real contact area in multi-scale methods does not converge, this work not only tests but also gives conditions required for convergence in these techniques. The results are also compared to other existing rough surface contact models.     

A partial elastohydrodynamic theory for the running-in process of hobbed gears

The running-in process of hobbed gears has been studied experimentally. The initial wear was found to be small although it increased with running speed and load. To explain the results, a simulation procedure was developed that was based on a random surface model and a proposed relation between film thickness, surface roughness and running conditions. A new oil model was used for the analysis of conditions between meshing rough flanks. The wear and deformation of asperities during the running-in period is due to direct contact between the asperities. The parameters determining wear and deformation are the adhesion and temperature between the asperities in contact.