电驱动偏心转子与复合振动环境振动同步的理论研究

在振动环境中，当带偏心转子的电机旋转角速度与振动环境的角频率相近时，两者可以实现振动同步。针对这一特殊现象，本研究提出一种小参数积分均值法来研究该振动同步问题，设置电驱动偏心转子角速度与振动环境角频率之差的积分均值为变量，通过积分变换将电驱动偏心转子与复合振动环境之间的动力学方程转化为二阶周期系数微分方程，应用周期系数二阶微分方程相关理论推导得出实现振动同步的同步性判据和稳定性判据，并通过数值仿真验证了同步性与稳定性判据的有效性。本研究提出的将电驱动偏心转子角速度与振动环境角频率之差的小参数积分均值法，为研究振动同步理论提供了一种新的方法。     

汽轮机转子的温度场及热应力场计算

利用积分变换法导出了蒸汽温升率连续变化时汽轮机转子的温度场和热应力场计算公式。本公式可直接应用于转子的应力监测与控制。和差分法相比，解析法的数据处理速度快，能满足快速监测、及时跟踪与控制的要求。关键词：汽轮机转子；温度场；热应力场     

常规螺杆泵定子有限元分析

螺杆泵定子橡胶不仅是易损构件，而且它与转子的配合状况对螺杆泵的工作性能影响显著。目前，还没有能够直接对实际工况下的定子橡胶的变形和受力状态进行测试的有效手段，因此对螺杆泵定子进行有限元分析自然是有益的尝试。重点研究定子橡胶衬垫内轮廓线的变形规律，而应力和应变分布情况仅作为辅助性的分析；对螺杆泵工况的考虑方面，重点研究均匀内压作用的情况，再考虑工作压差以及定子与转子的装配等所引起定子橡胶的变形和受力的变化。利用有限元分析软件Abaqus，对螺杆泵定子进行研究，得出了螺杆泵定子在不同工况下的受力状态和变形规律以及定子材料参数对变形规律的影响。利用此规律可对螺杆泵进行优化设计，提高其工作效率。     

裂纹转子的振动响应研究

本文研究了裂纹转子的振动响应。文章首先通过应力强度因子积分得到含裂纹轴单元的刚度矩阵；建立了裂纹转子的运动微分方程。进而研究了裂纹转子的振动响应，得出了裂纹转子的振动响应随裂纹位置和深度的变化关系。为工程上早期诊断微小裂纹提供了理论根据。     

无力矩非对称双自旋卫星的姿态运动

本文从动量矩守恒定律出发,导出以欧拉角及相对转动角为参变量的非对称双自旋卫星在无力矩状态下的一阶运动微分方程组,并利用能量积分获得零马达力矩条件下的解析形式姿态运动规律。以此讨论了转子自转角速度接近零时一类卫星的姿态运动稳定性,及其在消旋过程中通过不稳定区域时的非驻定姿态运动。文中顺便指出并纠正了文献[7]、[10]的错误之处。     

控制力矩陀螺用主动电磁轴承数字控制系统设计与实现

讨论了以TMS320VC33为核心的数字控制系统硬件结构。针对磁悬浮控制力矩陀螺转子的大惯量、小跨距、扁平转子和高速旋转时的陀螺效应，采用积分分离和不完全微分PID加交叉反馈控制策略。实验证明，该系统能够有效地抑制高速转子的陀螺效应，达到控制力矩陀螺电磁轴承高速稳定运行的要求。     

结构非线性动力分析混合时间积分并行算法

综合隐式和显式时间积分技术,对结构非线性动力反应分析提出一种并行混合时间积分算法.该算法采用区域分解技术.将并发性引入到算法中,即利用显式时间积分技术进行界面节点积分而利用隐式算法求解局部子区域.为实现并行混合时间积分算法,设计了灵活的并行数据信息流.编写了该算法的程序,在工作站机群实现了数值算例,验证了算法的精度和性能.计算结果表明该算法具有良好的并行性能,优于隐式算法.     

大型转子-基础-地基系统的非线性动力分析

针对实际工程中的大型机组，在线性理论分析基础上，引入转子系统的非线性油膜力项，采用子结构模态综合法，形成一个比较接近实际大型汽轮发电机组的包括陀螺转子-非稳态非线性油膜转承-弹性基础-地基系统的非线性系统计算模型。通过对系统方程进行分块直接积分求解，得到了不同位置的轴承在不同转速和不同转子偏心量下引起的系统非线性动力学现象，为大机组的非线性分析和改进提供较完善的理论分析和计算的基础。     

非线性转子——轴承系统1／2亚谐共振全局分岔研究

本文以采用短轴承模型的具有不平衡质量单园盘非线性刚性转子－－轴承变研究对象，利用中心流形定理和平均法相结合的方法，以及Ｔａｋｅｎｓ又特性值理论方法，在其临界点处对其有１／２亚谱共振情况下的周期振动、调幅和调相振动、以及同窠、异宿轨道的分岔性态进行了研究，给出了控制系统稳定运行的结构参数区域，为大型复杂转子系统的油膜失稳控制提供了某些理论依据。     

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合隐式和显式时间积分技术,对结构非线性动力反应分析提出一种并行混合时间积分算 法. 该算法采用区域分解技术. 将并发性引入到算法中,即利用显式时间积分技术进行界面 节点积分而利用隐式算法求解局部子区域. 为实现并行混合时间积分算法,设计了灵活的并 行数据信息流. 编写了该算法的程序,在工作站机群实现了数值算例,验证了算法的精度和 性能. 计算结果表明该算法具有良好的并行性能,优于隐式算法.     

考虑结构自重的基于NURBS插值的3D拓扑描述函数法

在许多如大坝、桥梁等大型土木工程结构中,结构的自重是初始设计阶段必须考虑的重要载荷之一,因此研究自重载荷作用下的结构拓扑优化设计问题具有十分重要的意义.针对考虑自重载荷作用的拓扑优化问题所面临的主要困难,总结了现有处理考虑自重载荷的拓扑优化问题的三类主要方法;提出一种基于非均匀有理B样条(non-uniform rational B-splines,NURBS)基函数插值的拓扑描述函数方法,基于此方法研究了考虑设计依赖自重载荷作用的2D/3D结构优化设计问题.在列式下,高阶NURBS基函数被同时用于三维NURBS实体片中的几何场、位移场及设计变量场插值,实现了几何模型、分析模型和优化模型的有效统一,确保了位移场及设计变量场的高阶连续性;详细推导了基于NURBS基函数插值的考虑自重载荷作用的三维结构拓扑优化模型及其灵敏度列式,并采用移动渐进线方法(method of moving asymptotes,MMA)进行了优化求解;多个算例验证了方法的有效性和稳定性,结果表明,优化迭代过程稳健,收敛快,能够有效地克服自重载荷作用下连续体结构拓扑优化中经常遇到的低密度区域材料的寄生效应及目标函数的非单调性等问题.     

Equilibrium equations for 3D critical buckling of helical springs

In most cases,the research on the buckling of a helical spring is based on the column,the spring is equivalent to the column,and the torsion around the axial line is ignored.A three-dimensional(3D) helical spring model is considered in this paper.The equilibrium equations are established by introducing two coordinate systems,the Frenet and the principal axis coordinate systems,to describe the spatial deformation of the center line and the torsion of the cross section of the spring,respectively.By using a small deformation assumption,the variables of the deflection can be expanded into Taylor’s series,and the terms of high orders are ignored.Hence,the equations can be simplified to the functions of the twist angle and the arc length,which can be solved by a numerical method.The reaction loads of the spring caused by the axial load subjected to the center point are also discussed,giving the boundary conditions for the solution to the equilibrium equations.The present work is useful to the research on the behavior of the post-buckling of the compressed helical spring.     

Characterizing fluid structure interactions of a helical coil in cross flow

Mechanical vibrations compromise the integrity of key components of thermal power plants. Without careful design, strong resonances during steady state operation can wear these components to the point of failure, leading to an unsafe situation that may force a plant to shut down. The purpose of this research is to further the understanding of the vibrations induced in a helical coil subject to steady fluid flow. A helical coil steam generator, such as that found in most integral pressurized water reactors, appears to eliminate many flow-induced vibration concerns when compared to traditional steam generators; however this has yet to be clearly demonstrated experimentally. The objective of this study is to detail and demonstrate a new method to quantify the motion of a helical coil in an annulus subject to external axial flow of water and further characterizing the influence of pitch-to-diameter ratio on the fluidelastic instability of a helical coil. This is accomplished by observing the motion of a helical coil mounted to an inner opaque cylinder through an outer glass tube using a high speed video camera. A mirrored image-pair is used to observe this structure from two perspectives simultaneously, allowing for three-dimensional characterization of the coil motion. The experimental facility is described in detail. The method developed herein for identifying specific points on the coil from images and mapping them to the coil location using the law of refraction is described. An uncertainty analysis of the coil position measurement is conducted based on geometry and refractive index which can be readily applied to measurements obtained using this method. The outcome of empirical observations shows these helical coils to hold a slightly higher resonance frequency than that of cylinders in cross flow, their mechanical stiffness approximated through analytical means shows to produce relatively accurate natural frequencies when compared to the empirical data – 14.1 Hz and 12.5 Hz, respectively for first mode vibration. This study”s contributions present a new method for metering fluid structure interactions with high-fidelity, provide new empirical data which has not previously been produced, and make observations to the response of a helical coil which are new to the field of fluid-structure interactions.     

Modelisation of thermoelastic linear behaviour of tungsten filaments in simple and twin helical spring configurations

By trying to increase the luminosity or the life expectancy of an incandescent lamp, an idea consists of a series of successive rolling up of the tungsten filament. This gives geometrical configurations of filaments named simple, twin, or triple helical spring, etc… In this paper, we will limit only to the cases of the simple and twin helical spring filaments. Under the combined effects of the high temperature and the stresses induced by its own weight, the filament creeps by becoming plastically deformed in a permanent and a continuously manner, until the rupture. The theoretical study of the behaviour of these filaments needs the knowledge of internal efforts distribution, deformations modes, and their evolutions. The present work consists on an elastic structural analysis which must be the first step. Since the objective is also to study the influence of the filament self-weight solicitation, the orientation (or position) with respect to gravitational direction should be taken into account. Numerical results are obtained by finite element method. They showed a negligible influence of the solicitations due to the variation of the temperature with respect to those of the self-weight, and a relative sensitivity to the position changes for the twin helical spring filament. For this later, we have developed an analytical method which is only valid in the case of a vertical position. Because of some difficulties, the comparison between the numerical and analytical results could not be carried out directly. However, the analytical approach proved to be qualitatively useful for the analysis of numerical results.     

精细时程积分法及其数值衍生格式应用评估

旋翼气动弹性耦合动力学方程本质上是一组刚性比较大的非线性偏微分方程。在有限元结构离散后，可改写为非齐次微分方程组，其中非齐次项是桨叶运动量（位移与速度）和气动载荷的函数。针对这类方程，本文尝试引入精细积分法及其衍生格式，借助数值方法计算Duhamel积分项。从积分精度与数值稳定性方面比较研究具有代表性的精细库塔法和高精度直接积分法。结合隐式积分算法，评估精细积分法应用于旋翼动力学方程的可行性。算例表明，精细积分法对矩形直桨叶动力学方程具有足够的求解精度。     

LES investigation on the dependence of the flow through a centrifugal pump on the diffuser geometry

Large-Eddy Simulation is utilized to investigate the rotor–stator interaction within a centrifugal pump. Comparisons are presented across diffuser geometries for two values of the flow-rate. Decreasing the incidence angle on the diffuser blades at off-design is found the main source of higher pressure rise and lower overall values of turbulent kinetic energy within the pump, resulting in efficiency improvement. The impact on the second-order statistics of the flow is especially significant. However, the values of the pressure fluctuations acting on the diffuser blades, defining fatigue loads on them and cavitation phenomena, are found especially affected by the rotor–stator clearance. Results show that at reduced flow-rates the rotation of the diffuser blades around their mid camber is a better option than rotating them around their leading edge. They also suggest that at larger flow-rates the increased incidence on the diffuser blades causes pressure side separation and large shear layers populating the diffuser channels, not affecting substantially the region of interface between impeller and diffuser, but having detrimental effects on the performance of the latter. The rotation of the diffuser blades around their leading edge should be preferred when the pump operates at flow-rates larger than the design one, avoiding decreasing the rotor–stator gap, thus resulting in smoother rotor–stator interaction and lower pressure fluctuations.     

Effect of axial load on the propagation of elastic waves in helical beams

Helical structures are designed to support heavy loads, which can significantly affect the dynamic behaviour. This paper proposes a physical analysis of the effect of axial load on the propagation of elastic waves in helical beams. The model is based on the equations of motion of loaded helical Timoshenko beams. An eigensystem is obtained through a Fourier transform along the axis. The equations are made dimensionless for beams of circular cross-section and the number of parameters governing the problem is reduced to four (helix angle, helix index, Poisson coefficient, and axial strain). A parametric study is conducted. The effect of loading is quantified in high, medium and low-frequency ranges. Noting that the effect is significant in low frequencies, dispersion curves of stretched and compressed helical beams are presented for different helix angles and radii. This effect is greater as the helix angle increases. Both the effects of stress and geometry deformation are shown to be non-negligible on elastic wave propagation.     

旋翼尾流与地面干扰时地面涡现象的研究

用Ｎ－Ｓ方程对近地飞行时旋翼尾流与地面干扰时产生的地面涡现象进行了数值计算旋翼对流场的作用由分布在特定区域内的动量源项模拟结果表明，旋翼尾流撞到地面后的卷起和轴向流动的拉伸作用是形成地面涡的原因；地面边界层形成的二次分离涡向地面涡内输入（与尾流所携带的涡量）相反的涡量，而使地面涡保持平衡；地面涡的存在和运动使旋翼附近流场大大改变     

Nonlinear bending behavior of 3D braided rectangular plates subjected to transverse loads in thermal environments

Nonlinear bending behavior of 3D braided rectangular plates subjected to transverse loads is investigated. A new micro-macro-mechanical model of unit cells is suggested. In this model, a 3D braided composite may be considered as a cell system and the geometry of each cell is deeply dependent on its position in the cross-section of the plate. The material properties of the epoxy are expressed as a linear function of temperature. Based on Reddy’s higher-order shear deformation plate theory and general von Kármán-type equations, analytical solutions for nonlinear bending behavior of simply supported 3D braided rectangular plates are obtained using mixed Galerkin-perturbation method. The numerical examples concern effects of geometric parameters, of fiber volume fraction, braiding angle and load boundary condition.     

变转速共轴旋翼载荷建模及实验验证

对共轴双旋翼无人飞行器操纵结构的简化,会引起旋翼载荷变化更加复杂。共轴双旋翼转速控制方法有助于飞行控制系统的实现,但是在飞行控制律设计时,需要透彻了解变转速旋翼的气动载荷变化,建立精准的旋翼载荷模型。本文深入分析了旋翼变转速情况下单旋翼系统和共轴双旋翼系统的旋翼入流分布,建立了单旋翼变转速旋翼载荷计算方法,提出了共轴双旋翼变转速旋翼载荷计算方法。明确了低雷诺数对微型旋翼飞行器的旋翼载荷计算影响,引入雷诺数修正系数完成对旋翼翼型升阻系数气动参数的修正和验证,提高了变转速共轴双旋翼载荷模型的计算精度。设计了一套变转速单旋翼系统和共轴双旋翼系统的旋翼载荷测量实验装置,通过实验测试完成了对共轴双旋翼载荷计算方法的验证,表明了所提出的变转速共轴双旋翼载荷模型和实验测试装置是可信的。