On Dual Configurational Forces

The dual conservation laws of elasticity are systematically re-examined by using both Noether's variational approach and Coleman–Noll–Gurtin's thermodynamics approach. These dual conservation laws can be interpreted as the dual configurational force, and therefore they provide the dual energy–momentum tensor. Some previously unknown and yet interesting results in elasticity theory have been discovered. As an example, we note the following duality condition between the configuration force (energy–momentum tensor) and the dual configuration force (dual energy–momentum tensor) ,

硅微机械谐振陀螺仪的非线性分析

给出了硅微机械谐振陀螺仪的结构,介绍了硅微机械谐振陀螺仪的工作原理,详细推导并给出了陀螺仪的输出频率和标度因数非线性的计算公式;基于影响谐振陀螺仪标度因数的参数,分析了由谐振器的振幅和梳齿静电驱动力引起的硅微机械谐振陀螺仪的非线性特性,给出了振动幅度与谐振频率关系的表达式.实验结果表明,陀螺仪的整体性能主要取决于谐振器振动幅度的稳定性.     

Behaviors of flow mechanisms and heat transfer of non-Newtonian fluids through a spinneret

This investigation examines non-Newtonian flow mechanisms and heat transfer characteristics for a micro spinneret. The working fluid, Polyethylene terephthalate (PET), is the raw material of micro fiber, and a large-scale experimental test model was designed to visualize the complex viscous flow system in the micro spinneret. To visualize the complex convective flow system, an experimental test model was constructed, using glycerin instead of PET. The related parameters of PET were compared with those of glycerin. The power law correlates the shear strain with PET viscosity at various temperatures. The pressure distribution along the flow direction was measured and the flow pattern was visualized using polyethylene (PE) powder of 20–40 m. Similar configurations were calculated for micro spinneret physical parameters to determine the thermal flow characteristics. The Reynolds number in the test model is not less than 10^–2. In the non-Newtonian PET working fluid of practical micro spinneret, flows with Re = 10⁴ to 10^–2 are in the same low Reynolds number flow regime. Therefore, the working fluid is expected to have the same flow characteristic. A numerical solution covering the range of approximately Re = 10^–4 at PET confirms that the flow characteristics of glycerin are constant for Re = 1.228 × 10^–2. The Peclet number in the test model can be adjusted to a value similar to that in the micro spinneret. The flow visualization was compared with that of the numerical solution, and the friction factor and Nusselt number in the micro spinneret were analyzed. Finally, numerical results and friction factor with various exit angles of micro spinneret in a triangular zone flow system were also summarized.     

船用气水分离器惯性级流场分析及阻力特性研究

采用二阶全展开ETG有限元与大涡模拟（LES）相结合的算法，对120－20－35－3型船用气水分离器惯性级在不同雷诺数条下的流动进行了模拟，通过其中一组雷诺数条件下计算所得该实验件阻力系数与物理实验所得阻力系数相比较，确定出该雷诺数条件下采用大涡模拟时所需的亚格子应力模型常数，将该常数带入其它各组雷诺数条件下的计算中，并将计算结果与相同条件下的物理实验结果相比较，证实了该常数的通用性。该常数一经确定，对各雷诺数条件下的流场进行分析，结果反映出采用二阶全展开ETG有限元与大涡模拟（LES）相结合的算法可以捕捉到非常丰富的涡系及涡动的时变过程。在流场分析的基础上本文计算了该实验件内的能耗场，计算结果表明实验件内的能耗主要集中在大涡丰富的区段内。     

松质骨弹性模量计算的均匀化方法

对松质骨建立了六种单胞微观结构模型，采用均匀化方法和有限元方法计算松质骨的宏观等效弹性模量。给出了六种单胞模型的松质骨弹性模量与材料密度(体分比）的关系，与实验数据进行了对比，分析了不同微观结构模型在不同骨骼中的应用。结果表明，本文方法及六种单胞模型可以对松质骨微观结构和材料性能进行有效的模拟计算。同时本文又着重对松质骨的宏观等效弹性模量与体分比的指数关系进行了探讨。     

Cr12MoV钢表面磁控溅射Ti/TiN涂层的摩擦磨损性能研究

采用非平衡磁控溅射方法在Cr12MoV钢表面制备了厚度约为3 μm的Ti/TiN涂层,测定了涂层的显微硬度,并通过划痕试验和摩擦磨损试验考察了涂层同基体的结合强度及其摩擦磨损性能.结果表明:Ti/TiN涂层能够显著提高Cr12MoV钢的表面硬度和承载能力;涂层同Cr12MoV钢基体的结合强度较高,划痕临界载荷高于60 N;与此同时,磁控溅射Ti/TiN涂层可以显著改善Cr12MoV钢的耐磨性能.这是由于磁控溅射Ti/TiN涂层硬度高且与Cr12MoV钢基体的结合强度较高所致.     

碳纳米管-聚丙烯酸乙酯复合乳液的制备及其润滑性能研究

采用乳液聚合方法合成了碳纳米管一聚丙烯酸乙酯(CNTs—PEA)复合乳液;采用JEM100XI型透射电子显微镜(TEM)观察了复合乳液的微观形貌;采用MQ-800型四球摩擦磨损试验机和MM-200型环一块摩擦磨损试验机考察了CNTs—PEA复合乳液作为水基润滑添加剂的摩擦学性能;并采用JSM-35型扫描电子显微镜(SEM)分析了磨斑表面．结果表明,CNTs—PEA复合乳液在极低浓度下即可有效地提高水基液的承载能力和抗磨性能．     

控制力矩陀螺用磁轴承磁力参数的辨识

提出一种实用的闭环辨识方法—磁中心变位移法,可以对控制力矩陀螺用磁轴承的磁力参数进行辨识。这种方法通过在磁中心处改变转子位移,得出不同位移时的电流值,再用这些值进行最小二乘辨识,得出所求的磁力参数。辨识出的电磁力模型中代入实际数据所得输出值与磁轴承实际输出数据非常吻合,证明了辨识所得磁力参数的准确性,并且用所得到的磁力参数指导磁轴承系统控制器参数的选择,使之更好地对磁轴承进行控制。实验证明,调整后的参数使转子在 30 060 r/mim 时仍能稳定地悬浮在给定位置,验证了所得磁力参数的准确性。     

Laser Doppler anemometry measurements of laminar flow in helical pipes

Three-dimensional laser Doppler anemometry measurements are performed on developed laminar flow in three helical pipes. The experimental observations are compared to results of numerical calculations employing the fully elliptic numerical method. Good agreement is found between measured data and numerical results. The three helical pipes, with curvature ratios of 0.0734 and 0.1374 and non-dimensional pitches of 0.0793 and 0.193, are adopted to study the effects of curvature and pitch on laminar flow in the experimental approach. The range of Reynolds numbers is 500–2000 to ensure laminar flow in the entire helical pipe. Both the profile shapes of the normal components of the secondary flow and those of the axial flow along the same centerline present not only similar patterns but also similar change when pitch, curvature ratio, and Reynolds number vary. The results demonstrate comprehensive relationships between the axial flow and the secondary flow.     

Epitaxy of Binary Compounds and Alloys

The present work aims at constructing a theoretical framework within which to address the issues of morphological instabilities (one-dimensional step bunching and two-dimensional step meandering), alloying, and phase segregation in binary systems in the context of (physical or chemical) vapor deposition. The length scale of interest, although nanoscopic, is sufficiently large that the steps on a vicinal surface can be viewed as smooth curves and, correspondingly, the theory is a continuum one. In a departure from theories inaugurated by Burton, Cabrera, and Frank [The growth of crystals and the equilibrium structure of their surfaces. Phil. Trans. Roy. Soc. A 243 (1951) 299–358] the steps are endowed with a thermodynamic structure whose main ingredients are a step free-energy density and edge species chemical potentials. Moreover, crystal anisotropy, with its altering of the dynamics of steps and the associated morphological instabilities, is accounted for – in a manner consistent with the second law – both in the thermodynamic and kinetic properties of terraces and, more importantly, of steps. Additionally, in contrast with most of the literature on the subject (cf. [J. Krug, Introduction to step dynamics and step instabilities. In: A. Voigt (ed.) Multiscale Modeling in Epitaxial Growth. Birkhäusser, Berlin (2005)]), adsorption–desorption along the steps, bulk atomic diffusion, and chemical reactions (both on the terraces and along the step edges) are incorporated and coupled to the other mechanisms, e.g., terrace adatom diffusion and step attachment–detachment kinetics, whose interplay governs the evolution of steps on vicinal surfaces. Importantly, aided by the concept of configurational forces for which a separate balance law is postulated Configurational Forces as Basic Concepts of Continuum Physics. Springer, Berlin Heidelberg New York (2000)]), the proposed theory allows the steps to evolve away from local equilibrium thus contributing to a general treatment of the dynamics of steps. Finally, a specialization to the epitaxy of binary compounds and alloys is afforded, yielding a generalization of the classical Gibbs–Thomson relation in the former and novel evolution equations for an individual step in the latter.