往复密封数值仿真模型及试验验证

基于混合润滑理论建立往复密封数值仿真模型,该模型综合考虑了密封系统中密封件的宏观固体力学变形、密封接触区微观粗糙峰接触、油膜厚度分布等因素,可以分析得到往复密封摩擦力、泄漏量等关键性能参数。以往复密封常用的斯特封为研究对象,通过往复密封基础试验台测量表征往复密封特性的关键参数摩擦力及泄漏量。试验与仿真结果表明:斯特封的瞬时摩擦力随着介质压力的升高而增大,反装斯特封的泄漏量随着往复行程的累积而增加。试验测量结果与仿真模型计算结果基本一致,验证了仿真模型的正确性。     

基于混合润滑模型的往复密封动特性研究

为研究往复运动密封性能,采用MatLab数值方法建立一种混合润滑模型,该模型包含弹性力学、流体力学和接触力学分析。基于混合润滑模型,研究粗糙度和往复速度对动态往复密封摩擦力、泄漏量和油膜厚度等密封性能的影响规律,揭示液压往复密封机制。结果表明:往复运动密封圈处于混合润滑状态,接触区不仅有流体压力,还包含粗糙度接触压力;存在临界粗糙度σ_c和临界速度u_c,当粗糙度σ<σ_c时,随粗糙度的增大内行程的泄漏表现为越来越小的内泄漏,当σ≥σ_c时,随粗糙度的增大内行程的泄漏表现为越来越大的外泄漏;当速度uc时,净泄漏量随速度的增大表现为越来越小的外泄漏,当u≥u_c时,净泄漏量随速度的增大表现为越来越大的内泄漏;随着粗糙度的增加,膜厚与内行程的摩擦力增大,而外行程的摩擦力无明显变化;随着速度的增加,油膜厚度增加,内行程摩擦力减小,而外行程摩擦力变化很小。     

液压系统中往复运动密封机制分析

针对唇型往复运动密封模型,提出一种分析往复运动密封在液压缸内外行程中油膜压力和温度分布的方法。采用有限差分法求解压力,采用逐列扫描技术计算温度。研究内外冲程中相对滑动速度和密封截面形状对密封机制的影响。结果表明:相对滑动速度越大,密封的动压效应越明显,油膜温度越高,且温度波动最大的区域位于最小膜厚处;刃倾角α、β取值及边界条件同时影响密封间隙的压力分布。     

双唇Y形拉杆密封的密封性能研究*

建立双唇Y形拉杆封的混合润滑模型,并进行流体力学、接触力学、变形力学分析。利用MatLab软件实现对模型的求解,得到密封区域的流量、膜厚和接触压力分布,并分析不同密封件粗糙度对轴向往复双唇Y形密封圈的摩擦力矩、泄漏量的影响。结果表明:在双唇Y形往复密封中,两唇在密封过程中均处于混合润滑状态,且第一内唇处的膜厚大于第二内唇处;第二内唇静态接触压力近似于对称分布,且第二内唇最大接触压力大于第一内唇最大接触压力,表明第二内唇作为密封的第二道防线可以保证良好的密封效果;密封件粗糙度是影响矩形密封性能的重要因素,随表面粗糙度的增加,直线往复密封的摩擦力和泄漏量增大,存在一个临界粗糙度使泄漏方向改变。     

往复式骨架油封密封界面内油膜压力和厚度分布

以汽车减震器密封用的往复式骨架油封为研究对象,基于润滑理论建立密封界面内的流体润滑数值计算模型来分析往复式骨架油封的密封性能,该模型耦合了固体力学、流体力学以及变形力学分析。采用ANSYS有限元分析提取密封区的静接触压力进行固体力学分析,采用超松弛迭代法求解雷诺方程进行流体力学分析,采用影响系数法求解密封唇面的变形,其中假定密封唇面的微凹凸形貌具有正弦和双余弦分布。通过模型分析密封唇面微凹凸形貌、往复速度对密封界面内的油膜压力和厚度的影响规律。结果表明:在2种不同形式的密封唇面微凹凸形貌下,内行程中密封界面内的油膜压力大于外行程的;密封唇面微凹凸形貌以正弦函数分布,往复式骨架油封密封处发生泄漏;密封唇面微凹凸形貌以双余弦函数分布,往复式骨架油封具有良好的密封性能。     

混合润滑条件下的斯特封高速摩擦与密封特性

为准确研究斯特封高速摩擦与密封特性,基于混合润滑理论,综合流体空化效应、密封接触变形和微观粗糙峰接触等因素影响,建立了斯特封摩擦与密封的数值计算模型.研究了往复运动速度和密封压力对油膜厚度、摩擦力和泄漏量的影响,搭建了往复密封试验台来验证模型的准确性.结果表明:计算摩擦力与实验摩擦力相近.混合润滑模型能更好地模拟高速柱...     

O形圈动密封特性的有限元分析

利用软件ABAQUS建立了O形圈的轴对称有限元模型,分析了其在往复动密封中的密封性能,并对其不同工况下的力学性能进行了研究。结果表明:往复动密封中,O形圈主密封面最大接触应力与Von Mises应力的作用位置随运动方向的变化而改变,且大小随时间呈波动变化;速度小于0.25 m/s时,速度对摩擦力与剪切应力几乎无影响;随着摩擦系数、介质压力的增大,摩擦力与剪切应力对速度的敏感性变高;介质压力与摩擦系数对摩擦力与剪切应力影响较大,剪切应力与摩擦力呈同步变化;密封外行程Von Mises应力与剪切应力均大于内行程,更易引起疲劳与剪切破坏;预压缩率增加到一定值时,O形圈在动密封中所受的摩擦力急剧上升,动密封中预压缩率不宜过大。     

基于流动因子的高压柱塞副往复密封性能研究

采用数值计算方法,建立了基于平均流动因子的往复密封混合润滑模型。分析了阶梯形组合密封圈表面粗糙度对其往复密封摩擦力、泄漏量和油膜厚度的影响规律。结果表明:内行程摩擦力随粗糙度的增大而增大,而外行程摩擦力无明显变化。存在临界粗糙度σ_c,当σ<σ_c时,随粗糙度的增大,内行程向内的剪切流量大于向外的压差流量,内行程泄漏量为正值,表现为越来越小的内泄漏;当σ≥σ_c时,随粗糙度的增大,内行程向内的剪切流量小于向外的压差流量,内行程泄漏量为负值,表现为越来越大的外泄漏。随着速度的增大,其临界粗糙度随之增大;随粗糙度的增大,平均油膜厚度增大,而粗糙度对量纲一化油膜厚度影响很小。研究方法为往复密封结构设计与优化提供了依据。     

旋转轴唇形密封混合润滑理论模型和试验验证

基于旋转轴唇形密封的反向泵送机理,采用流量因子统计学方法同时考虑密封唇表面粗糙峰接触的影响进行唇封性能的理论分析,建立唇封的混合润滑模型,模型耦合考虑流体力学分析,粗糙峰接触力学分析以及变形分析。求解雷诺方程得出油膜压力和切应力,利用GREENWOOD-WILLIAMSON接触模型计算粗糙峰与轴之间的接触压力,采用影响系数法进行变形分析。基于所建立的混合润滑模型,结合一种典型的唇封结构,对评价唇封性能的泵送率和摩擦扭矩进行数值计算,并通过自主研制的台架试验验证了唇封混合润滑模型的正确性。由于表面粗糙峰是导致旋转轴唇形密封产生泵送效果的原因,利用验证的理论模型对粗糙度对泵送率、摩擦扭矩和接触面积的影响进行分析。     

基于田口试验方法的双唇Y形拉杆封参数优化研究

为了探究不同结构及运行参数对双唇Y形密封性能的影响以及最优动态密封参数组合,利用ABAQUS有限元分析软件模拟分析双唇Y形拉杆密封在静压状态下的密封性能,通过改变第二内唇的左右倾角、轴向位置和过盈量,研究参数变化对双唇Y形拉杆密封性能的影响。分析动态密封下工作压力、活塞杆运行速度和密封件粗糙度对双唇Y形圈的摩擦力矩、泄漏量的影响。并利用田口试验设计方法对密封圈参数进行优化,确定参数的最佳水平。结果表明:随着第二内唇过盈量增大,两个唇最大接触压力均随之增大,而轴向位置对第二内唇最大接触压力影响不明显;当第二内唇左倾角大于25°、右倾角大于30°后最大接触压力波动显著增加;密封圈与活塞杆间的摩擦力随着密封件粗糙度、密封压力的增加而变大,而往复速度对摩擦力影响不大;当粗糙度大于0.95μm时密封出现外泄漏,密封压力的增加使密封圈的净泄漏量逐渐减小。研究的双唇往复密封最佳动态密封参数组合为工作压力8 MPa、粗糙度0.9μm、活塞杆运行速度10 mm/s。该研究结果可为具有微小扭转或弯曲变形工况下的液压缸拉杆密封设计提供参考。     

A Numerical Model of a Reciprocating Rod Seal With a Secondary Lip

A numerical model of an elastomeric reciprocating hydraulic rod seal, with both a primary and a secondary lip, has been developed. It is applicable to cases in which the stroke length is significantly larger than the seal width. Coupled fluid mechanics, contact mechanics, and deformation analyses are applied to each lip. Mass conservation and the pressure of the intervening fluid couple the two lips to each other. The leakage, the film thickness distribution, the fluid and contact pressure distributions, and the friction force are predicted for both the outstroke and the instroke for a typical seal, operating with mixed lubrication.     

基于压力渗透载荷的蕾形密封特性分析及参数优化

为改善蕾形密封的密封性能,考虑介质压力渗透效应,利用有限元分析软件ANSYS研究安装工况及介质压力作用下蕾形密封的密封特性,以及运动速度、摩擦因数、几何参数对动密封性能的影响。研究表明:介质压力作用时,蕾形密封密封面接触压力主要由支撑部承担,密封圈不会被挤入密封间隙,具有较好的抗磨损、抗挤出特性;动密封工况下,外行程比内行程产生的接触压力更大,外行程接触压力随摩擦因数增大而增大,内行程则相反,运动速度对动密封性能影响较小。根据几何参数对密封性能的影响对其进行响应面优化,在满足密封要求的前提下降低了活塞杆表面的最大等效应力,降低了活塞杆因表面疲劳磨损而发生密封失效的风险。     

基于流固热多场耦合的高速旋转唇形密封性能研究

针对一种橡胶材料高速旋转唇形密封,结合其自身结构及应用工况,通过方程离散化计算等方法,建立定量分析密封系统密封性能的数值仿真模型。基于所建立的模型对密封实际服役状态下界面流体力学、宏观固体力学、表面粗糙峰微观接触力学、唇口摩擦生热等多物理过程之间的耦合关系进行分析,借助实验验证并完善数值仿真模型的准确性。通过所建立的数值仿真分析模型研究油封唇口接触压力分布、唇口温度、摩擦力矩及泄漏率等衡量密封性能的关键参数随转速的变化规律。结果表明：在高转速条件下考虑摩擦生热时油封径向力减小,接触宽度增加,摩擦力矩减小,说明摩擦热对油封密封性能产生较大影响。     

Transient EHL analysis of an elastomeric hydraulic seal

Recent steady-state numerical analyses of reciprocating hydraulic rod seals have revealed many important details about the operation of such seals, including the fact that they generally operate with mixed lubrication in the sealing interface. However, these seals frequently operate under transient conditions, with the rod speed and sealed pressure undergoing cyclic variations with time. In the present study, a transient numerical model has been developed to take account of the varying rod speed. The model consists of a fluid mechanics analysis of the lubricating film of hydraulic fluid, a contact mechanics analysis of the contacting asperities on the seal lip and a structural analysis of the seal deformations. The fluid mechanics analysis consists of a finite volume solution of the Reynolds equation using a mass-conserving algorithm, which accounts for possible cavitation. The contact mechanics analysis utilizes the Greenwood–Williamson model. The structural analysis consists of a finite element analysis. Typical results are presented for an injection molding application. Of greatest importance is the net leakage per cycle. Also presented are the cyclic histories of such performance characteristics as the lubricating film thickness, contact pressure and fluid pressure distributions, the friction force on the rod and the instantaneous flow rate.     

Fluid-solid interaction model for hydraulic reciprocating O-ring seals

Elastohydrodynamic lubrication characteristics of hydraulic reciprocating seals have significant effects on sealing and tribology performances of hydraulic actuators,especially in high parameter hydraulic systems.Only elastic deformations of hydraulic reciprocating seals were discussed,and hydrodynamic effects were neglected in many studies.The physical process of the fluid-solid interaction effect did not be clearly presented in the existing fluid-solid interaction models for hydraulic reciprocating O-ring seals,and few of these models had been simultaneously validated through experiments.By exploring the physical process of the fluid-solid interaction effect of the hydraulic reciprocating O-ring seal,a numerical fluid-solid interaction model consisting of fluid lubrication,contact mechanics,asperity contact and elastic deformation analyses is constructed with an iterative procedure.With the SRV friction and wear tester,the experiments are performed to investigate the elastohydrodynamic lubrication characteristics of the O-ring seal.The regularity of the friction coefficient varying with the speed of reciprocating motion is obtained in the mixed lubrication condition.The experimental result is used to validate the fluid-solid interaction model.Based on the model,The elastohydrodynamic lubrication characteristics of the hydraulic reciprocating O-ring seal are presented respectively in the dry friction,mixed lubrication and full film lubrication conditions,including of the contact pressure,film thickness,friction coefficient,liquid film pressure and viscous shear stress in the sealing zone.The proposed numerical fluid-solid interaction model can be effectively used to analyze the operation characteristics of the hydraulic reciprocating O-ring seal,and can also be widely used to study other hydraulic reciprocating seals.     

基于斯特封的飞机作动器主密封有限元分析

斯特封作为常用的往复密封图,在密封过程中起着重要作用.选用斯特封作为飞机作动器密封的主密封件,首先通过单轴压缩实验获得斯特封D形圈和阶梯圈的材料参数,然后利用ABAQUS软件完成斯特封在不同工况下的有限元仿真.通过设置往复密封系统的结构、材料、工况等参数,选择流体压力渗透载荷加载方式,获得斯特封在不同油液压力时过盈安装...     

Simulation and experimentation on the contact width and pressure distribution of lip seals

The relative motion between two mated parts of machinery always generates heat from friction. The lubricant serves as a medium not only to reduce the friction but also to enhance heat dissipation. In order to contain the lubrication oil, lip seal is a most frequent sealing part used in these applications. This paper aims to study the contact width and contact pressure of the seal lip under the various interference fits between the shaft and seal. The contact force associated with the pressure was used to estimate the generated heat due to friction. Thereby, this frictional heat flux was employed to analyze the temperature distribution within the rubber seal. According to the temperature distribution, the thermal deformation of the seal and the concern of material ageing can be examined. Since the use of a seal with a shaft under allowable dimension tolerance is foreseeable, the fit with different degree of interference was investigated. On the other hand, a simple apparatus to measure the width and pressure on the contact lip zone under different diameters of shaft was designed and fabricated. The contact width and contact pressure were distilled from the press mark of a pressure-sensitive film. The measurements were used to demonstrate the feasibility and accuracy of the proposed set up.     

水泥环破碎器矩形异形活塞密封性能分析

针对传统圆柱形液压活塞承载力不足问题,提出一种矩形异形活塞,研究其在不同工况下的密封性能。基于Abaqus软件建立异形活塞有限元模型,研究介质压力、密封间隙、活塞运动状态以及摩擦因数对密封性能的影响,并分析异形密封环不同位置处的应力分布和翻转情况。结果显示：静密封时,介质压力越大,密封环的最大Mises应力和最大接触应力越大;密封间隙越小,最大Mises应力与最大接触应力越大;相比静密封,内行程过程中最大Mises应力和最大接触应力都有明显增加,且随摩擦因数增加而增加,而外行程中最大Mises应力和最大接触应力相比静密封差异较小;各工况下应力最大值均出现在密封环圆弧段;在活塞运动过程中密封圈并未发生翻转,只是存在位置的平移情况。研究结果证明了异形活塞的可行性以及良好的密封性能,为活塞结构设计与优化提供了依据。