往复密封轴用Y形密封圈密封性能分析

为研究往复密封轴用Y形密封圈在静、动密封工作时的密封性能,利用有限元软件ABAQUS建立了Y形密封圈二维轴对称有限元模型,讨论了工作压力、密封间隙、往复运动速度、摩擦系数对其密封性能的影响。结果表明:静密封工作时,Y形密封圈内部应力基本呈对称分布;动密封工作时,Y形密封圈内唇侧应力明显大于外唇侧应力,外行程应力变化波动幅度大于内行程相应应力变化波动幅度,外行程更易引起密封圈失效;Y形密封圈根部、上端开口处、内唇唇口、密封圈与活塞轴接触区域较易发生失效;Y形密封圈最大接触应力均大于相应工作压力,具有较好的密封性能;往复运动速度对最大Von Mises应力影响较小;工作压力、密封间隙、摩擦系数对最大剪切应力影响较大。     

轴用Yx形密封圈动密封特性的有限元分析

以轴用动密封Yx形密封圈为研究对象,运用有限元法建立二维轴对称模型,分析其在往复单向动密封中的密封性能,并对其不同工况下的力学性能进行研究。结果发现:动密封中Yx形密封圈主接触面最大接触应力、内部Von Mises应力的大小随时间而波动变化,且其作用位置随往复运动方向的改变而变化;主接触面平均摩擦力与介质压力、摩擦因数和密封间隙成线性关系,且几乎不因速度而变化,但最大摩擦力在各影响因素下却表现出了非线性特征;0.05~0.35 m/s范围内,速度对剪切应力影响较小;介质压力、摩擦因数、密封间隙对内行程的剪切应力影响较大;外行程在密封圈的失效过程中起主要作用;密封圈与轴接触的表面、内唇唇口、沟槽以及根部为易破坏的部位。仿真结果与实际失效特征吻合。     

低温往复O形圈失效机制研究

针对油气弹簧O形圈低温往复条件下普遍出现的失效现象,采用有限元方法建立O形圈摩擦力计算模型,研究常温与低温工况下O形圈的应力、接触宽度、摩擦力随油液压力的变化规律。结果表明,随油液压力的增加,常温下O形圈的应力、接触宽度、摩擦力均增大,而低温下Von Mises应力、接触宽度减小,接触应力和摩擦力增大;低温工况下O形圈的Von Mises应力、接触应力和摩擦力远大于常温工况;当油液压力大于12 MPa时,摩擦力随油液压力的变化率增加;低温工况下橡胶材料的玻璃化导致的O形圈拉力与摩擦力增大是其密封性能下降进而失效的主要因素,实际使用中必须予以考虑。     

高压氢气环境下橡胶O形圈静密封结构有限元分析

利用ABAQUS软件建立了高压氢气环境下橡胶O形圈静密封结构的有限元分析模型,研究了高压氢气作用下由于橡胶材料的吸氢膨胀对O形圈变形及应力的影响,探讨了不同初始压缩率、氢气压力、沟槽间隙、有无挡圈等工况下O形圈最大Von Mises应力、最大剪切应力和最大接触应力的变化规律。结果表明:高压氢气环境下,吸氢膨胀会导致橡胶O形圈的截面高度和面积的增加,但对O形圈的应力基本无影响。增加O形圈压缩率会提高初始安装工况下的接触应力,有利于初始密封的形成,但当介质压力较大时,过高的压缩率会显著增加剪切应力,导致O形圈发生剪切破坏。相较于低压工况,高压下密封沟槽间隙对O形圈的Mises应力和剪切的影响非常显著,较大的沟槽间隙会使O形圈发生挤出和剪切破坏,而安装密封挡圈可明显改善O形圈的变形和应力情况,有效防止O形圈被挤入沟槽间隙,同时提高密封性能。     

加氢枪用滑环式组合密封圈密封性能研究

本文提出一种加氢枪用滑环式组合密封圈,工作压力达70MPa,由PEEK材料的滑环和氟橡胶的O形圈组成.模拟分析了密封圈的静密封机理及介质压力的影响.测试了密封圈的静密封和动密封性能.结果 表明:滑环与活塞杆的接触压力,及滑环与O形圈的接触压力,随介质压力呈线性变化,前者斜率大于后者.最大Von Mises应力分布在滑环...     

D形橡胶密封圈的有限元分析及改进

采用ABAQUS软件分析介质压力、预压缩率对D形橡胶密封圈的变形、接触应力、米塞斯应力和剪切应力的影响,并和近似尺寸的O形圈进行对比。通过分析发现:相比于O形圈,D形圈内部米塞斯应力作用范围更小,而其接触面宽度更大;不同介质压力下D形圈能获得更好的密封性能,但压力较低时其寿命将小于O形圈;在较小预压缩率下D形圈更易获得良好的密封效果,且寿命也更长;高预压缩率下D形圈仍能获得更好的密封效果,但更容易出现老化;在圆弧与矩形连接处添加圆角凸台,结构优化后可有效降低D形圈内部的米塞斯应力以及剪切应力,使其具有更长的使用寿命。     

氟橡胶O形圈往复运动回弹摩擦特性实验研究

对低气体压力密封条件下氟橡胶O形圈的往复运动回弹摩擦特性展开实验研究。采用O形圈往复摩擦磨损实验台对氟橡胶O形圈与2Cr13不锈钢摩擦副摩擦力-位移曲线进行测量,分析运动位移、压缩率和密封压力对氟橡胶O形圈回弹摩擦性能的影响规律。结果表明:6%~15%压缩率条件下,在1 mm往复运动范围内,氟橡胶O形圈的回弹摩擦力随位移增加呈现线性增加;往复运动位移超过1 mm后,氟橡胶O形圈的回弹摩擦力稳定,不再随位移增加而发生明显变化;O形圈回弹摩擦力随压缩率增大而增大,密封压力越高回弹摩擦力越大。     

O形旋转密封圈的密封性能有限元分析

利用有限元软件ABAQUS建立了摆动液压油缸O形旋转密封圈的二维轴对称模型,分析计算了旋转轴直径、O形圈截面直径、O形圈内圆周向压缩率等结构参数对密封面最大接触压力和范·米塞斯(Von Mises)应力的影响。结果表明:介质压力为0时,旋转轴直径、O形圈截面直径对范·米塞斯(Von Mises)应力和密封面最大接触压力影响较大;O形圈内圆周向压缩率对Von Mises应力影响较大;在介质压力下,旋转轴直径、O形圈截面直径分别对Von Mises应力及最大接触压力的影响都不大,O形圈内圆周向压缩率主要是为了避免橡胶的焦耳效应;分析结果验证了长期使用的设计经验。     

高压气体密封橡胶O形圈往复摩擦特性实验

采用往复摩擦实验研究高压气体密封条件下橡胶O形圈的摩擦性能,分析密封压力大于3 MPa条件下密封压力、压缩率和橡胶材料对O形圈往复运动摩擦性能的影响规律。结果表明：高压条件下O形圈所呈现的摩擦力-位移时变曲线特征与低压条件相同,且黏滞特性明显。高压条件下随着密封压力的增加,丁腈橡胶O形圈最大摩擦力和滑动摩擦力呈线性增长,与低压下最大摩擦力存在极大值和滑动摩擦力趋于稳定不同;高压条件下丁腈橡胶O形圈的最大摩擦力与压缩率呈非线性关系,最大摩擦力存在极大值,与低压下最大摩擦力随压缩率的增大而增大不同;与丁腈橡胶材料不同,三元乙丙橡胶、硅橡胶和氟橡胶的摩擦力随密封压力的增加而逐步增加并趋于平稳,且摩擦力小于丁腈橡胶。     

液压式配气系统O型密封圈动密封特性分析

利用ABAQUS软件建立活塞运动速度为4 m/s、介质压力为6 MPa、摩擦因数为0.3的液压式配气系统O型密封圈有限元分析模型,分析不同往复运动速度、预压缩率、介质压力对液压式配气系统O型密封圈动密封特性的影响。结果表明:O型密封圈密封面的接触压力随位移的变化而产生波动,接触压力随介质压力、预压缩率的增大呈线性增大,运动速度对接触压力影响不大,接触压力曲线波动幅度随运动速度、介质压力、预压缩率的增大而增大;O型密封圈与油缸之间接触面的动密封性能优于O型密封圈与活塞之间接触面;O型密封圈在推程时的动密封性能优于回程;预压缩率小于10%时,O型密封圈不能满足该液压式配气系统的动密封要求,要确保O型密封圈的密封性,需要选择合理的预压缩率。     

Introducing an Evolving Local Neuro-Fuzzy Model – Application to modeling of car-following behavior

This paper proposes an Evolving Local Linear Neuro-Fuzzy Model for modeling and identification of nonlinear time-variant systems which change their nature and character over time. The proposed approach evolves through time to follow the structural changes in the time-variant dynamic systems. The evolution process is managed by a distance-based extended hierarchical binary tree algorithm, which decides whether the proposed evolving model should be adapted to the system variations or evolution is necessary. To represent an interesting but challenging example of the systems with changing dynamics, the proposed evolving model is applied to model car-following process in a traffic flow, as an online identification problem. Results of simulations demonstrate effectiveness of the proposed approach in modeling of the time-variant systems.     

On the Use of Enterprise Models

This paper presents the results of a field study designed to determine how enterprise models are used. The paper begins with an introduction to enterprise models then provides an overview of the survey method used. No known empirical studies have been conducted to determine how enterprise models actually are used by industry. The research is designed to answer this question. A screening sample and complete web-based survey of 72 enterprise modelers was conducted. The primary research question of this survey was on the use of enterprise models, with particular focus on the three dimensions of living models: scope, enactment, and dynamicity. Half the respondents claim that their enterprise models were of their entire division, multiple divisions, and even multiple enterprises. It is encouraging to see that enterprise models are used on such a wide scope. The enactment of the enterprise models was not as large as was expected. Of the respondents, 75% claimed that their models did not receive information from the enterprise more frequently than quarterly. The same was true for how often the models provided information to the enterprise. Seventy-five percent did not update their models more than five times (although, 32% did update the model three to five times). Finally, additional areas of research are proposed.     

智能设计中的基因模型

分析综述了智能设计的层次、研究现状和发展趋势 ,提出和研究了智能设计的知识模型 ,即符号模型、神经网络模型和基因模型 ,并对基因模型进行了重点阐述 ,进而对未来的研究提出展望     

计算机辅助设计在印刷机械设计中的应用

通过计算机辅助设计在印刷机械设计中的应用方法介绍,给计算机辅助设计在其它设计中的应用提供一种思路。     

Thermomechanical modelling strategies for multiphase steels

In multiphase steels, heat treatments such as quenching are usually applied to achieve a desired metallurgical composition to attain the expected mechanical properties. In these processes, residual thermal stresses arise during the cooling of the material which may induce a permanent deformation leading to dimensional instability. This deformation can be increased by the existence of phase transformations in the steel which should not be overlooked.In the current work, the thermomechanical modelling of multiphase materials is discussed. Firstly, a multiphase thermo-elasto-plastic-viscoplastic model is presented and applied to simulate several quenching heat treatments in a high carbon steel. The model uses the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation to describe the diffusion transformation and the Koistinen-Marburger model to characterise the diffusionless martensitic transformation in non-isothermal kinetics. This allows the observation of the evolution of the different steel phases (austenite, ferrite, pearlite, bainite and martinsite) during the cooling process. However, it is not possible to determine the residual stresses that arise in the intersection of the different phases.In the second part, the model that considers generalised multiphase transformation being compared with a multiphase homogenisation model for the case of a dual-phase steel during cooling and subsequent forming. The homogenisation micro-model operates over a periodic Representative Unit-Cell (RUC), detailing the heterogeneous material distribution due to the different metal phases. Therefore, it is possible to determine the residual stress fields in the intersection of the different phases. On the other hand, this model does not allow to reproduce the transformation process from austenite during cooling. Continuous cooling processes are studied in both parts. Following the heat treatment, tensile and shear test curves are presented and compared with experimental results for the second part.     

飞机易损性模型简化方法研究

针对工程应用中飞机零部件数目庞大导致易损性计算耗时长的问题,提出了3种飞机模型简化方法:产品封装法、等效法和修正法.产品封装法主要用于飞机系统部件的简化,等效法主要用于飞机结构部件的模型简化,修正法则用于飞机全机模型的简化.经过简化后的飞机模型,部件数目在300以内.使用飞机易损性评估方法计算模型简化后的飞机易损性,其...     

Discharge coefficient in the combined weir-gate structure

The present study investigated the flow discharge coefficient (C_dt) in the combined rectangular broad crested weir-gate structure. To this end, the effect of the following dimensionless parameters on the C_dt were investigated: the width ratio of the central weir to the width of the total structure (B/B_o), the height ratio of the central weir to the height of the central weir floor (Z/P), the ratio of the gate width to the width of the total structure (b/B_o), the ratio of the gate opening height to the height of the central weir floor (d/P), and the ratio of the head on central weir to the total head behind the structure (h₁/H). The Flow-3D numerical model, artificial intelligence models such as linear multilayer perceptron (MLP), Canfis network (CNN), recurrent network (RNN), modular neural network (MNN), and regression equation, were used to estimate the C_dt. The results indicated that increasing d/P and b/B_o ratios led to a decline in this coefficient. In the case of h₁/H ≤ 0.4, an increase in B/B_o ratio resulted in decreasing the turbulence intensity and C_dt while the impact of enhancing the size of B/B_o was not significant if h₁/H > 0.4. Besides, increasing Z/P ratio caused an increase in resistance against the flow and thus a decline in C_dt. Further, the results of artificial intelligence models and regression equation demonstrated that the MNN model with an RMSE and R² of 0.03 and 0.97, respectively, could have an accurate estimate of the C_dt values.     

Modeling nonlinear behavior in a piezoelectric actuator

A piezoelectric tube actuator is employed as a sample positioning device in Nanocut, a cutting instrument conceived to study the mechanics of nanometric cutting. Extension of functionality of the instrument as a nanometric machine tool motivates the search for an accurate model of the actuator for implementing feedback control. A simple nonlinear model describing longitudinal expansion of the piezoelectric tube actuator is presented in this paper. The model derivation is based on a non-formal analogy with nonlinear viscoelastic materials under uniaxial extension, for which the responses to a step input are similar to the piezoelectric tube. Suitability of the model structure for arbitrary inputs is tested by cross-verification between time and frequency domains. Two parameter estimation procedures are examined and the results of the experimental work for characterization, estimation and validation are presented.     

基于改进RANSAC特征提取的掘进装备视觉定位方法研究

为解决煤矿井下低照度、高粉尘、多杂光环境中掘进装备位姿测量不易的问题,提出了一种基于改进随机抽样一致性(RANSAC)特征提取的掘进装备视觉定位方法。首先,对矿用防爆相机采集的三激光标靶图像进行预处理,分别建立形状模型与线框模型;其次,根据形状模型以坐标极值为椭圆模型初始点,将前后两次内点差值比值作为最优迭代次数,迭代求取椭圆模型最优参数获得点特征;然后,根据线框模型以像素坐标模为直线模型初始点,利用自适应条件阈值、抽样次数获得线特征;最后,将点线特征作为三点三线位姿解算模型输入,通过空间坐标变换求得掘进装备位姿信息。实验结果表明,在掘进装备距三激光标靶80 m范围内,所述视觉定位方法的相对误差为±45 mm,可基本满足煤矿井下掘进装备定位需求,为煤矿井下恶劣环境中掘进装备的位姿测量提供一种新的思路。     

粉末成形过程中摩擦行为研究进展

粉末成形过程中的摩擦行为是一个十分复杂的问题,受粉末和模具材料性能、粉末形状大小、模具表面状况、粉末与模具间相对运动速度、润滑剂特性、粉末和模具温度等许多因素的影响.摩擦造成了制品密度低、分布不均匀、模具磨损,影响了制品的性能、尺寸精度及其应用范围.特别是复杂形状、厚度尺寸较大的粉末冶金制品,摩擦的存在极易造成制品的失效.摩擦行为的复杂性使得对其进行准确的测定和表达比较困难,加之这方面的研究不多,造成了进一步研究的困难.综述近几年国外对粉末成形过程摩擦现象的研究进展,着重介绍目前常用的两种摩擦测试和描述方法,即闭模式和剪切板式摩擦测定方法,为进一步研究粉末成形中的摩擦行为、提高制品性能提供参考.