TLM modeling of a probe‐coupled cylindrical cavity based on compact wire model in the cylindrical mesh

This article describes an implementation of a compact wire model into the three‐dimensional transmission‐line matrix (TLM) cylindrical mesh for the purpose of an efficient analysis of probe‐coupled cylindrical microwave cavity devices. Because of a cylindrical grid structure and empirical nature of the compact model, this implementation has to take into account a change of wire model parameters with a variable cross section of the TLM nodes through which a wire conductor passes. The model accuracy has been experimentally verified and compared with the corresponding results reached by the TLM method based on a rectangular grid in order to consider its advantages. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

Drag Power Loss Investigation in Cylindrical Roller Bearings Using CFD Approach

In high-speed rolling element bearings, the drag forces can be prominent and it is demonstrated in this investigation that the classical models may not be appropriate for correctly estimating this power loss contribution. A modification of the models is thus proposed, including the usual drag forces formulation relying upon the drag coefficient to be evaluated from a numerical computational fluid dynamics (CFD) approach. A three-dimensional approach that considers both the rings and the cylinder ends seems the only adequate approach to be used because a two-dimensional approach predicts a drag coefficient value that is too low. When using the former computed drag coefficient for the evaluation of the total power losses, high values of oil volume fraction must be employed to recover the measured power losses.     

“方变圆”变径筒状结构滑模施工技术

为解决塔式光热的核心构筑物吸热塔"方变圆"变径超高筒体结构施工难题,选用一套可变形的滑模平台系统,通过操作系统上可调千斤顶支座、门架横向液压千斤顶装置、多处可调节模板角度和收缩模板的丝杆等,使得滑模根据施工需求可在一定的范围内调节模板倾角、间距,并逐步完成收缩变形,其理论滑模允许偏角20°,最终高效完成异形结构施工。该滑模系统刚度大、承载及堆料能力强、空间大、机械化程度高,施工操作简单,安全性高,适应沙漠极端环境。全过程仅需使用一套滑模体系,就能完成方形段、方变圆的变形段及圆形段施工,大大提高了施工效率,为类似环境下相似结构的施工提供了一定的参考。     

Mechanical buckling of two-dimensional functionally graded cylindrical shells surrounded by Winkler–Pasternak elastic foundation

In this research, buckling analysis of a two-dimensional, functionally graded, cylindrical shell that has been embedded in an outer elastic medium in the presence of combined axial and transverse loading based on third-order shear deformation shell theory is numerically investigated. Variations of the shell properties are considered to be continuous through length and thickness. Winkler–Pasternak foundation and simply supported boundary conditions have been applied. The problem has been solved using the generalized differential quadrature method. Geometrical, load, and foundation parameters beside functionally graded power indexes effects on the critical buckling load have been studied.     

Comparisons of buckling-to-weight behavior of cylindrical shells with composite and metallic stiffeners

The present research deals with the study of buckling pressure-to-weight ratio of cylindrical shells with laminated ring stiffeners. The research introduces a strain energy formulation for laminated rings, in which each ring stiffener may be treated individually and the geometrical dimensions and material properties of the stiffeners may be different from one another. In a parametric study, the impacts of various geometrical parameters of rings on the buckling pressure-to-weight ratio of shells for composite and metallic stiffeners are compared. The results show that the buckling-to-weight behavior of the shells with Steel stiffeners generally differs from the shells with stiffeners made of Aluminum, E-glass/epoxy, Graphite/epoxy, or Kevlar49/epoxy.     

Viscous Potential Flow Analysis of Kelvin–Helmholtz Instability of a Cylindrical Flow with Heat and Mass Transfer

A linear analysis of Kelvin–Helmholtz instability of a cylindrical interface has been carried out when there is heat and mass transfer across the interface, using viscous potential flow theory. Both fluids are considered as incompressible, viscous, and thermally conducting with different kinematic viscosities. Both axisymmetric as well as asymmetric disturbances are considered. Stability criterion is given by a critical value of relative velocity and stability is discussed theoretically as well as numerically. Various graphs with respect to physical parameters such as wave number, viscosity ratio, heat transfer coefficients, Reynolds number, etc., have been drawn and the effect of various parameters have been described. A comparison with the linear stability analysis of inviscid fluids (Lee [10]) has been made and it is observed that viscosity has a stabilizing effect on the stability of the system. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 43(6): 489–503, 2014; Published online 3 October 2013 in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21092     

新型索承叉筒网壳的构形、分类与受力特性研究

叉筒网壳是一种由若干组圆柱面网壳相贯得到的空间结构,具有独特的建筑造型与受力性能.由于其传力路径简捷,主要集中于脊线或谷线,对边界约束要求较高,一定程度限制了其应用和发展.本文提出了一种新型索承叉筒网壳结构,并给出了三种不同的分类方法,较全面地概括了索承叉筒网壳结构的形体和种类,并提出了将索承叉筒网壳作为结构单元进行组合,构建大面积结构的设想.最后,以十二边形谷线式弦支叉筒网壳为例与叉筒网壳对比,并进行了参数分析,结果表明索承叉筒网壳结构静力性能得到较大的改善.     

不同滚压方式滚丝模主要参数设计

分别对不同滚压方式下滚丝模螺距、中径以及工件的轴向运动速度等三个参数的设计计算做了推导。并结合这三个参数在不同滚压方式下的具体情况,对目前常用的四种外螺纹滚压方式的特点进行了分析,以期对有关专业技术人员设计滚丝模有所帮助。     

一起风电场变压器短路故障的诊断与分析

分析了一起风电变压器低压多股并绕导线间的短路故障案例,采用多种试验方法并结合测量数据分析,推断出了故障部位,详细的介绍了分析过程和检查情况,并提出预防措施。     

电容法微力测量中轴偏对电容梯度的影响

电容法微小力值测量中电容传感器会存在轴偏现象,影响测量精度。基于理论模型,分析计算了电容传感器在轴偏情况下的电容梯度。设计了合理的测量方案,通过高精度图像传感器及机器视觉算法,实现了轴偏及电容梯度测量,对轴偏与电容梯度之间理论数值关系进行了实验验证。实验证明了理论推导的正确性及测量方案的可性行,为后续的微力精密测量提供了误差补偿依据。在当前的电容传感器条件下,轴偏不大于50μm时,可满足误差1%以内的系统整体测量目标。