关键词： ANSYS   旋转机械模块   动力特性   转子  

摘要： 利用ANSYS中的旋转结构分析模块对转子系统进行动力特性分析,特别是对不同结构的转子进行了临界转速的计算。在某种程度上,转子系统受到的激励载荷与转子系统的特性都与转速相关,因此确定转子的临界转速就显得十分重要。利用梁单元和弹簧单元建立了转子有限元模型,通过临界转速图谱法和同步响应法确定了转子的临界转速。

关键词： 动力吸振器   悬架上控制臂   振动控制   模态识别  

摘要： 动力吸振器DVA(Dynamic Vibration Absorber)广泛地应用于解决车辆中由于动力总成振动以及路面激励等原因引起的振动和噪声问题。针对某农用机械存在的前悬架上控制臂严重变形问题,应用模态识别技术对上控制臂结构的振动固有特性进行了测试,并结合有限元的方法,分析了该车前悬架上控制臂处振动情况不理想的原因。进而在探讨动力吸振器设计方法的基础上,设计了一款优化参数动力吸振器并应用于实际。

关键词： 柔性机械臂   刚-柔耦合   动力学仿真   材料力学性能  

摘要： 为优化仿人机器人手臂设计,基于Jourdain变分建立了刚柔耦合动力学模型;通过假设模态法对动力学方程进行解耦;编写了自适应变步长求解算法;在ADAMS虚拟样机和MATLAB上对水平面内的柔性手臂运动进行了仿真,人体手臂的运动仿真在虚拟样机进行.以人体手臂运动为参考,对比分析了变截面和等截面手臂的柔性变形,比较6种不同材质手臂运动中的末端横向变形量.仿真结果表明:等截面的仿人手臂运动可以近似等效为人体手臂的运动;柔性仿人手臂末端轴向变形量远小于横向变形量,对要求不高场合可以适当忽略柔性手臂的轴向变形;ABS材质的仿人机器人手臂柔性和人体手臂较为接近;改变ABS材质手臂的截面高度,可使得仿人手臂末端柔性和人体手臂一致,且振动主频和人体手臂固有频率不同.

关键词： 机械式混沌   相空间   混沌同步   非线性响应   混沌动力学  

摘要： 针对如何可靠地产生小振幅混沌这一难题,提出了一种机械式混沌同步的新方法.在理论建模的基础上,进行了动力学特性分析,得到了系统的分岔图,观察到了在不同参数下的响应.当参数处于一定范围时,系统会出现混沌行为,特别是支点的位置发生改变时,将诱导子系统产生小幅值混沌振动.结果表明:该同步方法简单易行,可靠且无时延;当杠杆与2个子系统连接处改用弹簧而不是刚性杆时,系统的动力学行为会更加复杂.

关键词： 机械通气   急性肺损伤   呼吸动力学   血流动力学  

摘要： 目的研究采用不同机械气模式对急性肺损伤（ALI）患者呼吸及血流动力学的影响。方法选择我院2010年1月~2011年12月收治的30例急性肺损伤患者,按照ALI评分分为两组,其中ALI评分值≥2.5的16例患者采用低潮气量＋呼气末正压（PEEP）通气,对14例ALI评分值〈2.5者最初采用辅助/控制通气（A/C）,逐渐改为同步间歇指令通气（SIMV）和压力支持通气（PSV）。观察机械通气过程中患者的呼吸及血流动力学的变化。结果 PEEP在5~15 cmH2O（1 cm H2O=0.098 kPa）范围内,动脉血氧分压（PaO2）、氧合指数（PaO2/FiO2）、肺静态顺应性（Cst）随着PEEP的增高而逐渐增加（P〈0.05）。在PEEP增加到20 cm H2O时心输出量（CO）和Cst下降,外周循环阻力（SVR）、肺循环阻力（PVR）和气道峰值压（PIP）增加（P〈0.05）。SIMV,PSV与A/C相比可明显降低气道峰值压（PIP）并使Cst增加（P〈0.05）。SIMV和PSV方式均可降低SVR。结论对急性肺损伤患者,应根据不同时期选择不同的机械通气模式,才能更好的增加氧供,减少对患者的呼吸和血流动力学的影响。

关键词： 上海交通大学   工程学院   校企合作   中华   可乐   山特   机械   自动化研究所  

摘要： 2012年6月29日上午，上海交通大学机械与动力工程学院和山特维克可乐满大中华区校企合作协议正式签署。出席签约仪式的嘉宾有山特维克可乐满大中华区市场与业务总监彭晓鸿女士、上海交通大学机械与动力工程学院党委书记陶燕敏先生、副院长刘应征先生、陈明教授和制造技术与装备自动化研究所的师生们。

关键词： nanomaterials   solid solutions   mechanical alloying   diffusion  

摘要： Specific features of the kinetics of absorption of atoms of an alloying element by nanostructured alloys which lead to the formation of strongly supersaturated interstitial solid solutions upon plastic deformation of multiphase powder mixtures is discussed. The rate of absorption is shown to substantially depend on the parameters of mechanical action, segregation phenomena at the external and internal boundaries of the solid solution, and mechanisms of plastic deformation of the nanomaterials. Numerical estimates of the parameters that characterize the process of mechanical alloying of the powder mixture of iron with 25 at % carbon are given, which agree satisfactorily with the experimental data.

关键词： Mechanical properties   Molecular dynamics simulation   Graphyne   Tensile deformation   Fracture  

摘要： In this work a series of carbon allotropes related to graphene, called graphyne, graphdiyne, gaphene-3, graphene-4 and graphene-5 are constructed by connecting two adjacent hexagonal rings with different number of acetylenic linkages. Mechanical properties of these monolayer networks are investigated through acting tensile loads on the architectures and molecular dynamics simulations are performed to calculate the fracture strains and associated ultimate stresses. In the armchair loading case, the fracture strain remains nearly unchanged whereas the ultimate strength degrades gradually with longer acetylenic chains. In the zigzag loading situation, the ultimate strength remains nearly the same whereas the fracture strain improves by a little amount with longer acetylenic chains. Furthermore, Young's moduli of all the investigated architectures are computed to analyze the material stiffness at the near equilibrium regime. The obtained results show that these structures are mechanically stable with high strength and stiffness. The unique mechanical property variations of graphyne family against armchair and zigzag loads suggest flexible designations towards functional use of this novel material, especially in the direction-dependent nanomechanical applications. (C) 2012 Elsevier B.V. All rights reserved.

关键词： Biosorption   Zn(II) ion   Pseudo-second-order model   Film diffusion   Diffusivity coefficient  

摘要： The activated carbon was derived from base (0.2M NaOH)-mediated activation of biomass followed by thermal treatment at 1,123 K. The utmost metal ion uptake capacity and sorption percentage of activated carbon derived from eucalyptus biomass were 1.42 mmol g(-1) and 93.42%, respectively. Freundlich isotherm model proved to be superior with higher linear correlation coefficient R-2 = 0.96-0.98. Similarly, it was observed that pseudo-second-order reaction model with lower chi(2) (0.002703-0.009351) and sum of square errors (0.0001-0.0144) value together with higher R-2 (0.98-0.99) ruled in all the possibilities of sorption of Zn(II) ion on activated carbon surface as chemisorption. Bangham's model (R-2 = 0.93-0.95) applicability in the present investigation demarcated the fact that the main rate-controlling step in the sorption of Zn(II) ions on activated carbon surface was film diffusion rather than intraparticle diffusion. The results of diffusivity coefficients (D-f = 7.16 x 10(-6) cm(2) s(-1)) reproduced the analogous viewpoint that film diffusion is quite a dominant step in the biosorption of Zn(II). Delta G, Delta H, and Delta S values obtained through the thermodynamic study of Zn(II) biosorption system were--9798 kJ mol(-1), 34.74 kJ mol(-1), and 107.63 kJ mol(-1) K-1, respectively.

关键词： Vascular disease   Balloon-expandable stent   Parametric stent design   Finite element analysis   Computational fluid dynamics   Stent fatigue life  

摘要： Atherosclerosis, a condition related to cholesterol build-up and thickening of the inner wall of the artery, narrows or occludes the artery lumen. A stent is a miniature medical device deployed in a stenotic artery to restore the blood flow. In this paper, we propose to apply the parametric design concept onto the stent design and integrate it with the developed FEA/CFD models to evaluate several key clinically-relevant functional attributes recommended by the FDA. These key clinical attributes include stresses/strains, fatigue resistance, radial strength, expansion recoil, and wall shear stresses, which have yet to be systematically investigated. Finite element models were developed to predict the mechanical integrity of a balloon-expandable stent at various stages such as crimping onto a balloon catheter, stent expansion, radial strength to resist blood vessels from collapsing, and service life in the human body when subjected to pulsatile blood pressure. Computational fluid dynamics models were developed to predict the wall shear stress distribution in stented arteries. A stent parametric analysis was conducted using the integrated computational schemes to systematically evaluate the effects of varying stent design parameters on key clinically-relevant functional attributes. Each stent design parameter was varied in its dimension from -30% to +30% (compared to the standard case) for sensitivity studies in attempts to find the most dominant design parameter for each key clinical attribute. The developed design/analytical schemes allow us to gain deeper insight into the fundamental stent issues and evaluate the mechanical/hemodynamic behavior of various stent designs. (C) 2012 Elsevier Ltd. All rights reserved.