数控机床电机散热温度场的数值模拟研究

电机作为数控机床的核心部件，其性能影响着机床主轴系统的精度、电机效率和使用寿命．因此，合理设计高速电机的结构使其处于最佳的温度场，了解电机在运行过程中各空气区域内的速度及温度分布非常重要．本文以某机床的电机定转子作为研究对象，利用CFD软件对转子通风道的设计方案进行数值模拟，通过数值模拟分析电机内部的流场温度场及流场分布．根据模拟结果进行优化设计，在转子和定子之间进行单排孔和双排孔的优化方案设计，通过温度分布确定最佳设计方案，为电机转子通风道的散热优化设计提供有意义的参考．     

载人列车车厢内空气流场温度场数值模拟

采用稳态不可压缩雷诺时均N-S方程、k-ε湍流模型,计算了载人列车车厢内三维空气流场和温度场。将太阳辐射热和人体散热作为能量方程的附加源项,研究了在条缝送风条件下,乘客和太阳辐射对车厢内流场和温度场的影响。计算结果表明:现有的送风方式除车厢两端外,车厢内沿长度方向气流分布比较均匀;送风口的布置对车厢内流场温度场分布影响较大,送风气流在车厢两侧形成两股比较大的流动旋涡;人体散热和太阳辐射对车厢内流场温度场影响较大,非空载时车厢内流场分布与空载时有较大差别,太阳照射和人体产生的热气流使车厢内存在较大的温度梯度,靠窗处的温度较高,过道处温度较低。流场温度场的计算结果和实验数据吻合较好。     

太空环境压力变化对液浮陀螺性能的影响分析

对太空气压变化影响液浮陀螺性能的机理进行了理论分析,然后利用有限元分析法对陀螺仪在压力变化时浮子产生的变形进行了计算.明确了压力变化对陀螺仪结构件变形的影响程度,并从几个对陀螺仪漂移产生影响的主要方面进行了深度分析,得知压力变化导致浮子的结构变形是陀螺仪性能变化的主要因素,其中框架的变形引起的陀螺漂移达0.3((°)·h-1),g.最后通过对某型陀螺仪进行压力变化试验,验证了分析结果的正确性.此外还对陀螺仪进行了封闭波纹管的实验.得出结论:采用相对厚实的结构,刚度较大、稳定性好的材料可大大提高陀螺仪对环境的适应性,另外还可以给陀螺仪装上对外界环境的密封隔离装置.     

过载-振动复合环境下液浮积分陀螺仪动力学分析

采用有限元数值计算方法对液浮积分陀螺仪在过载—振动复合环境中的动力学特性进行研究。对液浮积分陀螺仪浮子组件谐态和模态进行了分析计算，获得了复合载荷下浮子组件质心的附加偏移的数据，从而为分析陀螺仪的附加误差提供了依据。     

基于浮子运动的三浮陀螺仪工作温度标定方法

针对三浮陀螺仪工业生产过程中,工作温度标定方法精度低、耗时长的问题,提出了一种以"浮子运动趋势拐点"作为判据的工作温度标定方法。首先对三浮陀螺仪磁悬浮标定温度进行可行性分析,然后建立陀螺仪浮子受力模型以归纳浮子运动规律,借助磁悬浮控制系统提供的浮子位置信息提出本方法。试验结果表明,该方法工作温度标定精度优于±0.02℃,较现行的"最小加力法"提高15倍以上,平均耗时缩短一半。     

ANSYS在挠性陀螺仪温度场分布分析中的应用

本根据挠性陀螺仪稳定性要求对温度场分布进行了分析,采用美国有限元分析软件ANSYS5.4,在计算机上再现了T-1挠性陀螺仪启动过程中内部温度场分布的拟实模型,并最终通过大量的实验,验证了模型的正确性。     

电磁热效应止裂效果与裂纹走向关系的研究

采用理论、实验与数值分析的方法研究了在电磁热效应裂纹止裂中 ,由于裂纹走向不同导致裂纹尖端的温度场、温度梯度场分布状态的不同 ,并定量计算了它们的分布规律和差值。数值模拟计算应用了耦合场理论中热 电耦合 (焦耳热问题 )的分析方法。三方面的研究结果均表明 :在裂纹尖端处 ,由于电流产生的焦耳热源的作用 ,能够在很小的范围内熔化形成微小的焊口 ,遏制了裂纹的扩展 ;裂纹的走向是影响裂纹尖端温度场数值和温度梯度场变化即电磁热效应裂纹止裂效果的主要因素之一。     

火灾情况下混凝土板温度场的解析解

针对火灾情况下火场温度和构件边界的温度均随时间不断变化的问题,应用杜哈美尔定理分析了边界温度按一定规律随时间变化的热传导问题。推导得到了火灾情况下混凝土板温度场的解析解公式,并应用MATLAB编程计算得到了解析解结果。比较解析解的计算结果和试验结果发现:两者得到的截面温度场都呈非线性分布;两者的变化趋势一致,即近火面的温度梯度很大,距受火面越远,温度梯度越小;温度曲线都是凸向坐标轴。因此,推导得到的解析解公式适合于求解火灾时混凝土板横截面的温度场。同时,只要能够求出非齐次项与时间无关时的辅助问题的解,便可应用杜哈美尔定理求解该热传导问题的温度场,因此该方法可推广应用于火灾情况下其它构件温度场解析解的计算。     

火灾情况下混凝土板温度场的解析解

针对火灾情况下火场温度和构件边界的温度均随时间不断变化的问题,应用杜哈美尔定理分析了边界温度按一定规律随时间变化的热传导问题。推导得到了火灾情况下混凝土板温度场的解析解公式,并应用 MATLAB 编程计算得到了解析解结果。比较解析解的计算结果和试验结果发现：两者得到的截面温度场都呈非线性分布;两者的变化趋势一致,即近火面的温度梯度很大,距受火面越远,温度梯度越小;温度曲线都是凸向坐标轴。因此,推导得到的解析解公式适合于求解火灾时混凝土板横截面的温度场。同时,只要能够求出非齐次项与时间无关时的辅助问题的解,便可应用杜哈美尔定理求解该热传导问题的温度场,因此该方法可推广应用于火灾情况下其它构件温度场解析解的计算。     

指北陀螺仪与永磁陀螺电机

本文首先简述了陀螺经纬仪中指北陀螺仪的基本原理,接着提出了指北陀螺的核心部件——陀螺电机的几种主要性能对指北陀螺定向精度的影响。通过永磁陀螺电机与目前常用的感应及磁滞陀螺电机主要性能的比较,说明永磁陀螺电机是指北陀螺仪最适用的陀螺电机。它不但可以提高指北陀螺仪的定向精度,而且可以大大简化并减小仪器用电源的尺寸和重量。最后从进一步提高指北陀螺性能的基本观点出发,就主要参数的选定、电磁设计、控制方式和计算机辅助优化设计等方面,重点讨论指北陀螺仪使用永磁陀螺电机的若干特殊问题。     

The application of Moire interferometry in the measurement of displacement field and strain field at notch-tip and crack-tip

This paper presents the application of Moire interferometry in measuring the displacement and strain field at notch-tip and crack-tip before and after crack propagation. The experiment is carried out using a three point bending beam with a notch. TheN _x andN _y fringe patterns representing displacement field, and the ΔN _x/Δx and ΔN _γ/Δγ fringe patterns representing the strain field are obtained. The sensitivity of the measured displacement is 0.417 μm per fringe order. The displacement and strain distribution along the sectionx=0 have been worked out according toN _x andN _γ fringe patterns. The project supported by Chinese Academy of Sciences and National Natural Science Foundation of China     

Fluidization in combined acoustic-magnetic field for mixtures of ultrafine particles

Four kinds of SiO2 （5-10 nm）＋ Fe3O4 （44.8 μm） particle were fluidized in a sole acoustic field, a sole magnetic field and a combined acousticmagnetic field. Introduction of a single field, 100 dB/40-60 Hz acoustic or 10 mT magnetic, could suppress plugging and channeling and reduce the superficial minimum fluidization gas velocities, Umf. Combination of both acoustic and magnetic fields demonstrated even more promising results, especially more significant reduction of Umf.     

Mode I crack tip field with strain gradient effects

A plane strain mode I crack tip field with strain gradient effects is investigated. A new strain gradient theory is used. An elastic-power law hardening strain gradient material is considered and two hardening laws, i. e. a separation law and an integration law are used respectively. As for the material with the separation law hardening, the angular distributions of stresses are consistent with the HRR field, which differs from the stress results^[19]; the angular distributions of couple stresses are the same as the couple stress results^[19]. For the material with the integration law hardening, the stress field and the couple stress field can not exist simultaneously, which is the same as the conclusion^[19], but for the stress dominated field, the angular distributions of stresses are consistent with the HRR field; for the couple stress dominated field, the angular distributions of couple stresses are consistent with those in Ref. [19]. However, the increase in stresses is not observed in strain gradient plasticity because the present theory is based on the rotation gradient of the deformation only, while the crack tip field of mode I is dominated by the tension gradient, which will be shown in another paper. Supported by the National Science Foundation of China (No. 19704100), Science Foundation of Chinese Academy of Sciences (Project KJ951-1-20), CAS K. C. Wong Post-doctoral Research Award Fund and the Post Doctoral Science Fund of China.     

土体主动滑动场及主动土压力的计算

将边坡临界滑动场方法进行推广与改进,提出挡土结构中的土体主动滑动场的数值模拟方法,并得到相应的主动土压力分布。数值计算结果表明,本文方法精度高,与现有的解析解一致;且可方便地考虑挡墙面的摩擦作用、土体的不均匀分布以及复杂的外载组合,值得推广应用于工程设计。     

Phase field modeling of damage in glassy polymers

Failure mechanisms in amorphous polymers are usually separated into two types, shear yielding and crazing due to the differences in the yield surface. Experiments show that the yield surface follows a pressure modified von Mises relation for shear yielding but this relation does not hold during crazing failure. In the past different yield conditions were used to represent each type of failure. Here, we show that the same damage model can be used to study failure under shear yielding and crazing conditions. The simulations show that different yield surfaces are obtained for craze and shear yielding if the microstructure is included explicitly in the simulations. In particular the breakdown of the pressure modified von Mises relation during crazing can be related to the presence of voids and other defects in the sample.     

地磁场在导航定位系统中的应用

阐述了地磁匹配导航的基本原理及相关地磁场理论,介绍了国内外应用地磁导航的动向及发展现状,提出了地磁导航系统中三个方面的关键技术:一是导航区域地磁数据库的建立;二是载体上磁力仪的实时测量;三是地磁匹配算法。同时,结合有关地磁建模方法、地磁测量补偿算法及地磁匹配导航定位算法,分析了地磁导航存在的主要问题,指出了发展地磁导航应采取的必要措施,为下一步地磁导航的深入研究明确了方向。     

Diffusion of a megagauss field into a metal

The plane one-dimensional problem of the diffusion of a megagauss field into a metal wall is solved taking into account heat conduction and radiation transfer. At the interface, the magnetic field is assumed to be constant, and in this sense, the problem is close to the self-similar diffusion problem with parameters dependent on the self-similar variable x/ . It is shown that if heat conduction and radiation transfer are taken into account, in megagauss fields (in the examined formulation for fields B > 1.6 MGs) there is no loss of conductivity of the material evaporated by the magnetic field because of the formation of a plasma layer at the interface with a temperature in the electronvolt range. However, the role of the plasma layer in the structure of the skin layer remains insignificant up to fields B 10 MGs.Translated from Prikladnaya Mekhanika I Tekhnicheskaya Fizika, Vol. 46, No. 2, pp. 5–12, March–April, 2005.     

Two notes on nonlocal field theory

In this paper, two fundamental problems completely unsolved in nonlocal field theory are studied. The first is the dependence of nonlocal residuals. By studying this problem, a theorem concerning the relationship between the residuals of nonlocal body force and nonlocal moment of momentum is given and proven. The other problem is how to give the stress boundary conditions in the linear theory of nonlocal elasticity. The stress boundary conditions obtained in this paper can not only answer why the nonlocal stress solution satisfying the boundary conditionst _ji ^(s) n _j ¦O ₂ =p _i (p _i is a constant) on the surface of crack does not exist but also give a model of the molecular cohesive stress on the crack tip.     

飞机结构三维温度场分析程序

介绍了“飞机结构三维温度场分析”程序。该程序具有完整的自动建模体系和云图曲线显示功能。通过试验测定了“热阻”参数，进而在程序中增加了热阻元以处理不同结构件的接触问题，考虑了空气动力加热载荷情形。经过许多工程算例，结果良好。