An equivalent uniaxial fatigue stress model for analyzing landing gear fuse pins

We study the biaxial stress state conditions in landing gear fuse pins in the fuse groove. This biaxial state comprises a combination of shear stresses which are usually the largest stresses in the fuse pin by design, and compressive stresses which keep the half-section of the fuse pin in equilibrium. Conventional fatigue analysis techniques use an equivalent uniaxial stress, based on the Mises stress of a pure-shear condition. The respective predicted fatigue damages are much higher than those obtained from fuse pin cyclic tests. A new equivalent uniaxial fatigue stress model is proposed that includes the additional compressive stress as a relief on the fatigue damage in the fuse groove, thereby explaining the observations from fuse pin tests. The model is used in conventional uniaxial strain-life fatigue software (Goodrich Aerospace’s Fatigue Life V2) to predict the fatigue damage on a landing gear fuse pin with a sample load spectrum. The results are then compared to the pure shear model, and to a biaxial finite element fatigue analysis. As compared to the equivalent Mises model, the proposed model provides less conservative estimation of the fuse pin fatigue life, the latter value being higher than that provided by the two-dimensional finite element calculation. __________ Translated from Problemy Prochnosti, No. 3, pp. 85–98, May–June, 2006.     

Correlation for the Carbon Dioxide and Water Mixture Based on The Lemmon–Jacobsen Mixture Model and the Peng–Robinson Equation of State

Models representing the thermodynamic behavior of the CO₂–H₂O mixture have been developed. The single-phase model is based upon the thermodynamic property mixture model proposed by Lemmon and Jacobsen. The model represents the single-phase vapor states over the temperature range of 323–1074 K, up to a pressure of 100 MPa over the entire composition range. The experimental data used to develop these formulations include pressure–density–temperature-composition, second virial coefficients, and excess enthalpy. A nonlinear regression algorithm was used to determine the various adjustable parameters of the model. The model can be used to compute density values of the mixture to within ±0.1%. Due to a lack of single-phase liquid data for the mixture, the Peng–Robinson equation of state (PREOS) was used to predict the vapor–liquid equilibrium (VLE) properties of the mixture. Comparisons of values computed from the Peng–Robinson VLE predictions using standard binary interaction parameters to experimental data are presented to verify the accuracy of this calculation. The VLE calculation is shown to be accurate to within ±3 K in temperature over a temperature range of 323–624 K up to 20 MPa. The accuracy from 20 to 100 MPa is ±3 K up to ±30 K in temperature, being worse for higher pressures. Bubble-point mole fractions can be determined within ±0.05 for CO₂.     

金属掺杂对In2O3薄膜光学性质的影响

研究了射频溅射法制备的金属／半导体类型颗粒膜的光学特性。通过样品透射谱分析，发现金属Fe的掺杂使半导体In2O3的带间跌迁由直接跃迁变为间接跃迁；随Fe所占体积份数的增加，局域态尾变宽，带隙变窄。这是由于掺入Fe颗粒后。母体材料与金属颗粒的界面处表面态增多，以及母体材料的非晶化引起的。     

低热固相反应在材料合成中的应用

介绍了低热固相反应机制的研究进展、反应特点及影响低热固相反应的一些因素。重点阐述了低热固相反应在纳米材料、有机合成、电池材料、气敏材料以及其它一些功能材料中的应用。阐明低热固相反应确实是新型材料制备的一种简便、有效并有光明前景的方法。     

Determination of the pressurising period for stored cryogenic fluids

It is a normal operating condition for a lot of cryogenic storage vessels that no boil-off gas is vented over long periods, which leads to a simultaneous pressure increase of the stored fluid. One main reason therefore is to avoid product losses during transport or between withdrawals. At transport conditions the mixing of the fluid can be assumed to be ideally, which results in a maximum reachable pressurising period. At stationary conditions the pressurising period is expected to be shorter, because a stratification is rising up, so that the heat capacity of the stored fluid cannot be used completely.In a thermodynamic view, an isochore change of state takes place and the heat flux into the vessel rises the internal energy of the fluid. For the representation of the isochore change of state a new developed Δu/v-v-diagram with the 1 × 10⁵ Pa reference as a basis line is introduced. The basis line is linear for the filling rate and functionally connected with the specific volume.For the fluids He and H₂ e.g., Δu/v-v-diagrams are pointed out, using the u- and v-values on the saturation lines for the two phase region and those of some isobar lines for the region above the critical pressure.     

基于组态软件的分布式低压变电箱监控系统的Web发布

介绍了基于组态软件的分布式低压变电箱监控系统构成,可实现数据采集、状态检测、无功补偿、远程监控等功能,并根据主控计算机和远程监控计算机处于不同网络位置给出了3种基于组态软件的Web发布模式。     

开关磁阻电动机稳态特性的研究

用等效磁网络模型方法给出了开关磁阻电动机稳态特性的计算结果，结合系统的驱动电路和驱动逻辑建立了开关磁阻电动机稳态分析的实验模型，分析了开关磁阻电动机稳态运行过程中绕组电流、磁场储能和动态转矩的变化情况，尤其是对电机磁场储能的研究。详细的仿真分析证实了该方法的可行性，通过实验进一步证实了该方法的有效性。     

基于自适应有限元法和改进遗传算法的边坡临界滑动面搜索

本文采用自适应有限元法进行边坡稳定分析,将改进的遗传算法和自适应有限元法相结合,建立基于应力场的边坡任意形状临界滑动面的全局搜索方法，该改进的遗传算法采用十进制编码,并根据个体适应度不同对交叉概率和变异概率进行自适应调整,使群体中的优良个体不易被破坏,同时又保证种群个体的多样性,从而提高算法的搜索效率.通过典型算例分析,证明这种基于自适应有限元分析和改进遗传算法的边坡任意形状临界滑动面搜索方法可行、高效。     

锅炉汽温控制状态反馈极点配置的两种简易设计方法

状态反馈极点配置对于大惯性锅炉汽温对象来讲是一种有效的控制方法。该文针对锅炉汽温的动态特性及控制方式的特点,提出了两种基于代数运算的简易极点配置方法,其一据二项式定理,将被控对象整定为时间常数可成倍减小的多阶惯性环节;其二利用代数运算实现了极点的任意配置。该配置方法避免了采用常规极点配置方法时较为繁琐的矩阵运算,便于工程应用,且极点配置过程以减小汽温对象的惯性时间和加快对象的响应过程为核心,有直观的工程物理意义。最后,利用某300MW火电机组汽温模型,验证了该极点配置方法的有效性和优越性。     

ANSYS软件在高功率密度异步电机定子热分析中的应用

介绍了应用ANSYS自带的APDL编程语言进行软件开发的经验。将该软件应用于高功率密度异步电机定子热分析中。实现了该电机定子自动建模、自动施加载荷的功能，使用和修改都很方便。并且计算速度快。通过对该电机定子温度场计算结果的后处理，得出了该电机定子运行在不同时间段里的温度分布图，以及该电机定子壳体任一节点的温升曲线。