关键词： 动力机械   隔振系统   刚度   阻尼   传递率  

摘要： 采用理论分析和实验研究相结合的方法,研究了动力机械隔振系统参数对传递率的影响,获得了不同的激振力频率下,刚度和阻尼参数对传递率的影响规律,并分析了规律存在的内在机理。研究结果表明,当动力机械设备工作在低频共振区时,传递率Ta的最大值与刚度(或固有频率)无关,随阻尼比ξ增加按T_a=1/(2ξ)+1规律明显下降;当动力机械激励频率ω远高于固有频率时,传递率随隔振系统刚度减小而明显下降,同时减小阻尼比也有助于减小传递率;对于质量、刚度和阻尼均确定的系统,当激励频率远大于系统固有频率时,传递率Ta随激励频率ω增加而减小。上述结论得到了试验验证。

关键词： 机械臂   关节刚度   柔性多体动力学   拓扑优化   载重/自重比  

摘要： 针对柔性关节对工业机器人动力学特性的影响,基于"转子-扭簧"模型和有限元法,研究关节刚度对机械臂固有动力学特性的影响规律;考虑臂杆柔性和关节柔性,建立了机械臂多柔体动力学有限元模型,以机械臂轻量化为设计目标,以末端总位移量为约束条件对机械臂结构进行优化。研究结果表明,不同关节刚度对机械臂各阶固有频率的影响不同,优化后的机械臂载重/自重比增大,刚度和强度均得到提高,整体动力学性能明显提高。

关键词： 欠驱动   柔性机械臂   弹性变形   耦合分析  

摘要： 为建立柔性3R欠驱动机械臂的动力学方程,采用Euler-Bernoulli梁模型并添加经迭代计算的边界条件,对柔性机械臂进行了动力学耦合与仿真分析。在对柔性机械臂进行模态分析的基础上,将柔性机械臂视为包含边界条件的悬臂梁和简支-自由梁模型,采用假设模态法建立柔性3R欠驱动机械臂的动力学模型。仿真结果证明:添加经迭代计算的边界条件的柔性梁模型能更好地反映自由关节的加速度耦合情况。最后对柔性欠驱动机械臂与刚性欠驱动机械臂进行关节耦合指标分析,结果表明柔性欠驱动机械臂的自由关节包含更复杂的耦合情况,对柔性机械臂弹性振动的控制是对柔性欠驱动机械臂控制的关键。

关键词： 六自由度机械臂   建模   仿真分析   扭矩  

摘要： 随着工业自动化的不断发展,机械臂在自动化生产车间的应用日趋广泛。本文通过对一种六自由度机械臂的结构分析,了解其工作及传动原理。利用计算机辅助设计软件对其进行三维建模,并在动力学分析软件中进行扭矩仿真分析,为其结构设计及关节处电机选型提供参考。

关键词： 2F2R宏微机械臂   动力学模型   弹性振动   尺度效应  

摘要： 柔性宏刚性微机械臂是一类典型的刚柔混合机械臂系统。采用有限元法,以2F2R宏微机械臂为研究对象,通过分析,详细推导和建立具有普遍意义的动力学模型。基于给定关节空间运动轨迹,对2F2R宏微机械臂的结构参量、截面参量、材质、集中质量分布等与系统弹性振动尺度效应之间关系与变化规律进行分析。在此基础上,针对操作空间运动轨迹,采用宏微空间分解方法,进一步分析上述设计参量与系统弹性振动尺度效应之间关系。通过上述两方面研究工作,获得许多有参考价值的研究成果,这对于该类宏微机械臂的设计与控制都将具有重要意义。

关键词： 计算   流体动力学   航空叶轮:应用  

摘要： 对于物理这一方面来说，计算流体动力学是新的技术，近几年对于流体动力学的完善也提高了，在科学研究中的分量也很重。本篇文章就对计算流体动力学在航空叶轮机械中的应用展开探讨，为以后这项技术能更好的为航空叶轮机械领域贡献一份力量，应用流体动力学时有许多问题需要更好的解决，只注意速度与难度是不对的，要对整个运作过程完整的分析，保证它的工作量和易操作性。

关键词： binding energy   mechanical activation process   molecular dynamics   uniformity  

摘要： Herein, molecular dynamics simulations and experiments were carried to select solvent for the mechanical activation process. The interaction between solvent and each component of the Al-PTFE mechanical activated energy composites has been studied by means of molecular dynamics. Then, the status of Al and PTFE in solvent was analyzed, and the microstructure of the composite was also studied combined with experiment. At last, the mechanical activated energy composites were prepared with n-hexane as the solvent. The results show that the adsorption of PTFE, toluene, and hexane on the (0 0 1), (0 1 0), and (100) surface of Al2O3 is stable. Al2O3 (0 0 1) surface and Al2O3 (0 1 0) surface interact with 3 substances mainly via the electrostatic force. Al2O3 (1 0 0) surface interacts with 3 substances mainly via the van der Waals force. The binding energies of toluene-Al2O3 and hexane-Al2O3 are larger than PTFE-Al2O3. PTFE cannot adsorb on the surface of aluminum in the existence of n-hexane and toluene. n-Hexane can make PTFE disperse uniformly, and a considerable part of these PTFE will be coated on the surface of Al after n-hexane is removed. The uniformity of Al/PTFE mechanical activated energetic composites prepared in n-hexane is good, and it increases with the milling time.

关键词： Hydrogen reduction   Magnetite   Mechanical activation   Reduction kinetics   Nucleation and growth  

摘要： The effect of mechanical activation on the reduction kinetics of magnetite concentrate by hydrogen was studied. The magnetite concentrate was milled for 8 h in a planetary ball mill. After 8 h of milling, the average particle size was reduced from 14 to 4.4 A mu m, resulting in a lattice microstrain of 0.3. Isothermal reduction experiments were conducted by thermogravimetry to focus on the chemical reaction as the rate-controlling factor by eliminating external mass transfer effects and using a thin layer of particles to remove interstitial diffusion resistance. Thus, about 2 mg of magnetite powder was reduced at different temperatures under a sufficient flow of hydrogen. The magnetite concentrate and reduction products were analyzed by SEM and XRD. It was found that the onset reduction temperature decreased from 587 to 500 K (314-227 A degrees C) due to the mechanical activation. The activation energy for hydrogen reduction of the activated concentrate decreased about 10% compared with the as-received concentrate. In view of the results, a reaction rate expression was established based on the nucleation and growth model with an Avrami parameter n = 2.5.

关键词： Wrist watch   Mechanical regulator   Compliant hinge   Isochronism   Quality factor   FE   CFD   Multi-body  

摘要： This paper presents a new mechanical regulator for wrist watches, highlighting the methodology used to set up a comprehensive model of the device. The mechanical regulator, which is characterized by a high frequency monolithic oscillator made of monocrystalline silicon coupled to a deadbeat escapement, has been designed to provide a high quality factor, a condition necessary to guarantee enhanced chronometric performances compared to traditional mechanical regulators. The chronometric performances and the isochronism of the oscillating system have been assessed by means of a multi-body model whose parameters have been evaluated by FE and CFD simulations. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： gaseous   adsorption   fixed-bed   diffusion kinetics   modeling  

摘要： Adsorption is a complex physicochemical process involving interparticle transport, interphase mass-transfer, intraparticle diffusion, and surface reactions. Although the exact description of the adsorption process will inevitably vary from system to system, it will always be governed by those primary mechanisms. Therefore, by devising a model framework that can inherently include those mechanisms, it would be possible to create a modeling platform on which many different adsorption problems could be solved numerically. To accomplish this task, a generalized 1-D conservation law model was created to include the necessary mechanisms of adsorption on several different geometrical domains. Specific model applications for adsorption were developed under that framework and validated using experimental data available in literature or obtained in this work. This modeling platform makes it easier to model various adsorption problems and develop new adsorption models because of the common treatment of the mathematics governing the physical processes. (c) 2017 American Institute of Chemical Engineers