自动检测da/dN的微机系统

研制了一种da/dN自动检测系统;介绍了其工作原理和裂纹长度a及循环数N的采集方法;与传统的目测法做了对比;显示了该系统的优越性。     

A modified model for simulating latent hardening during the plastic deformation of rate-dependent FCC polycrystals

A strain hardening model for the plastic deformation of rate-dependent FCC crystals is proposed based on experimental observations previously reported for single crystals. This model, which is an extension of that employed by et al. [1983], includes both the self-hardening and latent hardening of the slip systems. The differential hardening of the latent systems is assumed to arise from the interaction between glide dislocations and forests. With this hardening model and a rate-sensitive crystal plasticity theory, the deformation behavior of FCC polycrystals can be predicted from the deformation response of the constituent single crystals. As examples, the uniaxial tensile behaviour of pure aluminum and copper polycrystals is simulated using the extended model, and the results are compared with published experimental data. The effects of latent hardening on polycrystal deformation, especially on flow stress and the formation of tensile textures, are discussed.     

Evaluation of creep damage behavior of nickel-base directionally solidified superalloys with different crystallographic orientations

A crystallographic creep damage constitutive model is developed for nickel-base directionally solidified superalloys. The rates of material degradation and grain boundary void growth are considered. The governing parameters are determined from the creep test data of single crystals and directionally solidified superalloys with a crystallographic orientation. A finite element program is used to analyze the creep damage behavior of nickel-base directionally solidified superalloys for different crystallographic orientations. The results depend on the number of grains modelled and compare well with the experimental data.     

THE ANALYTICAL STUDY ON THE LASER INDUCED REVERSE－PLUGGING EFFECT BY USING THE CLASSICAL EIASTIC PLATE THEORY（I）─TEMPERATURE FIELDS

ＴＨＥＡＮＡＬＹＴＩＣＡＬＳＴＵＤＹＯＮＴＨＥＬＡＳＥＲＩＮＤＵＣＥＤＲＥＶＥＲＳＥ－ＰＬＵＧＧＩＮＧＥＦＦＥＣＴＢＹＵＳＩＮＧＴＨＥＣＬＡＳＳＩＣＡＬＥＩＡＳＴＩＣＰＬＡＴＥＴＨＥＯＲＹ（Ｉ）─ＴＥＭＰＥＲＡＴＵＲＥＦＩＥＬＤＳＺｈｏｕＹｉｃｈｕｎ...     

在飞航导弹中用星敏感器修正捷联惯导陀螺漂移

星敏感器是一种高精度的姿态测量装置。研究了星敏感器和陀螺的特点,对星敏感器工作原理和修正陀螺漂移技术进行了原理分析。在不利用外界提供的姿态和位置信息的情况下,采用卡尔曼滤波的信息融合算法,建立组合导航系统的状态方程和量测方程,利用星敏感器输出的载体相对于惯性空间的姿态信息来修正捷联惯导的陀螺漂移。设计飞航导弹的典型飞行轨迹,通过数学仿真,对上述算法的有效性进行了验证,结果表明星敏感器能够有效地补偿捷联惯导由于陀螺漂移带来的误差,明显提高了导航定位精度。     

横向磁场激励下铁磁梁式板的混沌运动分析

在磁体力分布的磁弹性理论模型和磁场准静态假定模式基础上，对于处在周期时变磁场 中的不可移简支铁磁梁式板非线性磁弹性动力特性进行定性与定量分析．首先利用磁场的摄 动技术和结构变形的模态法，导出了关于模态坐标的非线性动力方程；然后利用Ｍｅｌｎｉｋｏｖ方 法，从理论上给出这一磁弹性动力系统可能出现混沌运动的必要条件及参数范围；最后采用变 步长Ｒｕｎｇｅ－Ｋｕｔｔａ数值积分方法对其磁弹性相互作用的混沌现象进行了定量搜索与模拟，并 利用其轨迹的Ｐｏｉｎｃａｒｅ截面图与Ｌｉａｐｕｎｏｖ指数加以判断．结果表明磁弹性简支梁式板在横 向周期时变磁场中存在混沌吸引子，且在机械阻尼很小时其混沌吸引子表现出稠的特性．     

面向对象有限元程序的类设计

传统有限元程序设计中的许多问题可以通过面向对象程序设计方法加以解决。本文介绍了我们尝试采用ＢｏｒｌａｎｄＣ＋＋２．０进行的一种面向对象有限元程序设计，着重进行有限元程序的类划分与定义，并将几个典型的类设计成类等级。面向对象语言的继承性、封装性、多态性等特性在我们的程序设计中均得到了运用。与传统的有限元程序（通常采用Ｆｏｒｔｒａｎ）相比，面向对象有限元程序更加结构化、更易于编写、更易于维护和扩充，程序代码的可重用成分更大，它为开发大型有限元分析软件提供了一条新途径     

THE ANALYTICAL STUDY ON THE LASER INDUCED REVERSE－PLUGGING EFFECT BY USING THE CLASSICAL ELASTIC PLATE THEORY（Ⅰ）－TEMPERATURE FIELDS

ＴＨＥＡＮＡＬＹＴＩＣＡＬＳＴＵＤＹＯＮＴＨＥＬＡＳＥＲＩＮＤＵＣＥＤＲＥＶＥＲＳＥ－ＰＬＵＧＧＩＮＧＥＦＦＥＣＴＢＹＵＳＩＮＧＴＨＥＣＬＡＳＳＩＣＡＬＥＬＡＳＴＩＣＰＬＡＴＥＴＨＥＯＲＹ（Ⅰ）－ＴＥＭＰＥＲＡＴＵＲＥＦＩＥＬＤＳＺｈｏｕＹｉｃｈｕｎ...     

EXACT LINEARIZATION BASED MULTIPLE-SUBSPACE ITERATIVE RESOLUTION TO AFFINE NONLINEAR CONTROL SYSTEM

To the optimal control problem of affine nonlinear system, based on differential geometry theory, feedback precise linearization was used. Then starting from the simulative relationship between computational structural mechanics and optimal control, multiple-substructure method was inducted to solve the optimal control problem which was linearized. And finally the solution to the original nonlinear system was found. Compared with the classical linearizational method of Taylor expansion, this one diminishes the abuse of error expansion with the enlargement of used region.     

高速移动荷载下黏弹性半空间体的动力响应

分别以移动荷载和黏弹性半空间体模拟运动列车荷载和地基,分析了地基在运动列车作用下的动力响应.首先采用Green函数法求解黏弹性半空间体在各种移动荷载模式作用下的动力响应的解析解,包括恒常和简谐移动点源、线源和面源荷载.然后采用IFFT算法和自适应数值积分算法计算解析解中的二维积分,得到了包括低音速、跨音速和超音速移动荷载作用下位移的数值结果.最后分析了速度对位移的分布和最大值的影响,发现当速度大于Rayleigh波速时,位移发生显著变化.