A direct stiffness analysis of a composite beam with partial interaction

The use of the conventional semi-analytical stiffness method in finite element analysis, in which interpolation polynomials are used to develop the stiffness relationships, leads to problems of curvature locking when beam-type elements are developed for composite members with partial interaction between the materials of which it is comprised. The curvature locking phenomenon that occurs for composite steel–concrete members is quite well reported, and the general approach to minimizing the undesirable ramifications of curvature locking has been to use higher-order polynomials with increasing numbers of internal nodes. This paper presents an alternate formulation based on a direct stiffness approach rather than starting from pre-defined interpolation polynomials, and which does not possess the undesirable locking characteristics. The formulation is based on a more general approach for a bi-material composite flexural member, whose constituent materials are joined by elastic shear connection so as to provide partial interaction. The stiffness relationships are derived, and these are applied to a simply supported and a continuous steel–concrete composite beam to demonstrate the efficacy of the method, and in particular its ability to model accurately both very flexible and very stiff shear connection that causes difficulties when implemented in competitive semi-analytical algorithms. Copyright © 2004 John Wiley & Sons, Ltd.     

An eight‐node hybrid‐stress solid‐shell element for geometric non‐linear analysis of elastic shells

This paper presents eight‐node solid‐shell elements for geometric non‐linear analysis of elastic shells. To subdue shear, trapezoidal and thickness locking, the assumed natural strain method and an ad hoc modified generalized laminate stiffness matrix are employed. A selectively reduced integrated element is formulated with its membrane and bending shear strain components taken to be constant and equal to the ones evaluated at the element centroid. With the generalized stresses arising from the modified generalized laminate stiffness matrix assumed to be independent from the ones obtained from the displacement, an extended Hellinger–Reissner functional can be derived. By choosing the assumed generalized stresses similar to the assumed stresses of a previous solid element, a hybrid‐stress solid‐shell element is formulated. Commonly employed geometric non‐linear homogeneous and laminated shell problems are attempted and our results are close to those of other state‐of‐the‐art elements. Moreover, the hybrid‐stress element converges more readily than the selectively reduced integrated element in all benchmark problems. Copyright © 2002 John Wiley & Sons, Ltd.     

IC—V100电台锁相环频率合成器

本文从频率合成器的结构、功能入手,详细阐述了频率编程的原理及方法。     

机械锁定式地层测试技术研究与应用

机械锁定式测试技术操作简单，测试一次成功率高，资料录取准确全面，且测试结束后可直接进行封堵作业；解封时，机械锁紧产生一个向上的震击力，有利于解封，没有换位机构的测试阀在关井期间使管柱处于自由拉伸状态，有利于保护油管。在N阀上部管柱中加1-2根伸缩接头，便可用于海洋井测试。     

连续箱梁桥中跨合龙段劲性骨架优化设计

结合某连续箱梁桥悬臂施工实践,对中跨合龙段劲性骨架设置和受力进行了分析,推导了劲性骨架设计的理论计算公式,并分析了劲性骨架刚度大小对桥梁整体结构的影响。     

增力式夹具的设计与应用

增力式夹具结构紧凑，夹紧迅速可靠。它可以用较少的原动力获得较大的夹紧力，其增力倍数据实际须要同设计者调整。而且，若按机构自锁条件设计，该夹具夹紧之后，实现自锁。本文对该夹具结构做了介绍，并通过理论分析，指出增力系数和夹具自锁的设计条件。     

隔离开关二次回路防误闭锁改造与应用

分析泉州电业局220kV老式变电站原隔离开关二次防误闭锁回路存在的隐患,针对改造前存在的安全问题,提出了改造措施。     

橡胶注射成型机的特点与进展

对橡胶注射成型机主要部分的结构进行了评述，并对橡胶注射成型工艺的发展状况了简述。     

自升式海洋钻井平台锁紧装置液压系统

针对自升式海洋钻井平台锁紧装置,讨论其构成,对作为驱动装置的液压系统进行设计并作出原理图,运用solidworks和3D Studio Max软件对锁紧装置进行建模仿真.锁紧装置液压系统的设计主要采用比例阀控制的同步回路和用顺序阀的顺序动作回路来分别实现液压缸的同步运动以及顺序动作.     

基于卡尔曼滤波的髓内钉锁孔操作标定方法研究

在机器人辅助正骨手术中,髓内钉的锁孔操作需要很高的定位精确度,因此需要一种相应的高精确度系统标定方法来满足定位要求.本文利用卡尔曼滤波的间接法标定法,其跳过对定位盒顶点坐标的求取,将标定盒三个顶点的坐标作为状态参量,将机器人由拍照位姿到钻孔位姿之间的位姿变换参数当作观测参量.并在此基础上推导出状态参量与观测参量之间的映射关系,对一系列观测参量的测量,利用卡尔曼滤波算法对状态参量进行滤波估计,最后间接求取转换矩阵.实验证明,这种方法的精确度不会因为标定试验次数增多而导致标定盒磨损,重复精确度较高.