M2机器导轨试验台的研制及激振对爬行抑制的试验研究

在机械、仪器和高技术密集型产品零件加工设备中,精密位移的研究受到重视。性能良好的试验装置是十分必要的。M2试验台采用微机技术、光电测量技术和数据分析与处理技术,使研究工作定量化。试验台研制成功后,曾做了法向高频激振对爬行抑制的研究。试验表明,只需很小的功率就可以消除爬行。这一实验引起同行专家的注目。     

粘-滑比对干摩擦约束结构动态响应的影响

用AFT(Alternated Frequency/Time)方法计算了受干摩擦约束系统稳态响应,进而计算了干摩擦能耗及干摩擦触点的粘滞-滑移状态。结果表明:干摩擦能耗最大值对应的结构稳态振幅没有达到最小。而应用干摩擦触点粘-滑比率来衡量干摩擦约束结构的减振性能是一种更有效的方法。最后,分析了结构内阻对选择粘-滑比率的影响。     

遥感-岩石力学(Ⅵ)——岩石摩擦滑移特征及其影响因素分析

以花岗闪长岩和辉长岩为例，结合遥感．岩石力学基础实验研究，研究了双轴加载条件下岩石摩擦滑移特征，重点对影响岩石摩擦滑移特征的5个重要因素，即正应力、岩性、摩擦表面粗糙度、含水性及摩擦速率进行了实验分析。研究表明：(1)正应力越大，越容易出现粘滑，粘滑时应力降越大，且重复粘滑的间隔周期越长。(2)相同边界条件下，辉长岩的粘滑性比花岗闪长岩强。(3)摩擦表面粗糙度对岩石的粘滑性能有较大影响，重复摩擦会增加粘滑的不稳定性。(4)含水后岩石摩擦面的摩擦强度会降低，但摩擦过程中水份随产热蒸发，其摩擦强度会逐渐恢复。(5)低速率摩擦时岩石主要表现为枯滑，而高速率摩擦时则主要表现为稳滑。     

Comparison of two stick-slip testers and recommendations for repeatable and significant stick-slip testing

Because of the interaction of the large number of parameters influencing stick-slip, it is very difficult to perform repeatable and reproducible tests that define the anti-stick-slip properties of lubricants. In order better to understand the difficulties encountered in stick-slip testing, an overview of the influencing parameters, with a discussion of each parameter, is given in this paper. Some modifications of the reciprocating stick-slip tester that was used in the ASTM test procedure before the latter was withdrawn, in order to improve the repeatability of its test results, are discussed. The significance of the results is checked by comparison with a rotary stick-slip tester. Finally, recommendations for correct stick-slip testing and interpretation of stick-slip results are presented.     

气动比例/伺服位置系统扰动观测补偿控制的研究

通过对气动比例／伺服位置控制系统的静／动特性的分析,提出了用于气动比例／伺服系统的扰动观测补偿器,仿真及实验表明,该方法可有效地改善气动比例／伺服系统的刚性差、抗外界干扰性差等弱点。     

牵引电机扭矩激扰的机车齿轮传动系统非线性特性

考虑牵引电机扭矩变化和轮轨黏着力波动等外部激励,以及齿侧间隙、时变啮合刚度和传递误差等内部激扰,采用集中质量法建立了某和谐号机车直齿齿轮传动系统的动力学模型。利用数值方法求解了电机扭矩变化时齿轮传动系统的动力学响应。结合分岔图、相平面图、庞加莱截面图、时间历程图、频谱图,分析了电机扭矩变化对系统非线性特性的影响规律,揭示了系统由单周期、多周期到混沌运动的非线性动力学演化机理。     

Relationship Between Viscoelastic and Peeling Properties of Model Adhesives. Part 2. The Interfacial Fracture Domains

The viscoelastic and peeling properties of polybutadiene/tackifying resin compatible blends have been studied in detail. Viscoelastic properties have been described through the variations of the complex shear modulus, G*(w), as a function of frequency, W, and peeling properties through the variations of peeling force (F) as a function of peeling rate (V).

The first paper of this series presented the cohesive fracture domain and the present paper explores the interfacial fracture domain: (i) rubbery interfacial (interfacial 1); (ii) stick-slip; (iii) glassy interfacial (interfacial 2). After a general survey of the properties in the three domains we present a quantitative relationship between the peeling and linear viscoelastic properties as a function of the adhesive formulation, discussing the use of time-temperature equivalence for adhesive properties. The third part of the paper presents the trumpet model of de Gennes describing the crack shape and propagation: starting from a mechanical analysis of the peeling test, it is shown how one may calculate the variations of the peeling force as a function of peeling rate in the various interfacial fracture domains: this model defines a single interfacial fracture criterion which coexists with the cohesive fracture criterion defined earlier, whatever the fracture location.

We present as a conclusion a critical discussion of the relevance and physical meaning of such a criterion and present a new outlook for the modeling and improvement of adhesive formulations.     

HDPE及其共混物的挤出压力振荡现象

采用恒速型双毛细管流变仪研究高密度聚乙烯及其共混物的压力振荡现象,测量了压力振荡的振幅及频率,计算了熔体在管壁的滑移速率和临界外推滑移长度。结果表明,发生压力振荡时,熔体与毛细管壁的界面出现“时黏时滑”转变。黏界面时,挤出物表面出现“鲨鱼皮”现象;滑界面时,挤出物表面粗糙,类似于无规破裂。随剪切速率的增加,压力振荡的振幅减小,而滑移速率、临界外推滑移长度及振荡频率均有提高。升高挤出温度和采用共混改性都可抑制压力振荡现象。     

The influence of rheological properties of mineral oil in the stick-slip phenomenon

Within the range of small and very small sliding velocities that are typical of applications such as clutch mechanisms, guideways of machine-tools, hydraulic or electric drives for robots, and continuous-indexing mechanisms, the phenomenon of ‘stick-slip’ occurs. By taking into consideration the dependence of kinetic friction force on sliding velocity during the slip period, three critical velocities of movement stability are revealed. One of the important ways for reducing the amplitude of the phenomenon is by designing lubricating grooves of optimum geometry brought about by oil viscosity and surface tension.     

高压共轨压电喷油器迟滞控制研究

通过Matlab/Simulink建立了压电堆执行器迟滞补偿模型,由压电堆执行器无外载静态试验获得了基于Maxwell粘-滑模型的迟滞特性模型参数,将模型用于高压共轨压电喷油器控制.实验结果表明,采用建立的迟滞补偿模型,通过开环前馈控制,有效抑制了压电堆执行器的迟滞影响,喷油率上升和下降速率减缓,有利于降低燃烧噪声和减小"水击现象"对喷油量波动的影响.