Free-edge stress concentration in angle-ply laminates

Summary For a symmetric [±]s-angle-ply laminate coupon within the framework of linear elasticity the free-edge effect is treated in a closed-form analytical way. To that end, for uniaxial tension the near-edge deformation is traced back to a complex-analytical potential. For the given boundary conditions the respective potential is determined and thus the resultant displacement field and the accompanying stresses. Thereby, in particular, a logarithmic singularity is obtained for the free-edge stress concentration.     

Mathematical Modeling,Control, Computer Simulation and Laboratory Experiments of a Spatial Servopneumatic Parallel Robot

In this paper (Part I), the special construction of a controlled parallel structure, called spatial servopneumatic multi-axles test facility (MAP), will be theoretically and numerically investigated and controlled. The investigations include the following steps: (i) design of mathematical models of different complexity of both, the test facility mechanics in terms of DAEs and ODEs (a multi-body system which contains 13 rigid bodies under spatial motion, connected by joints), and the servopneumatic actuators; (ii) construction of different linear and nonlinear (model based) control algorithms; (iii) development of a computer simulation program of the MAP; and (iv) evaluation of various computer simulation runs, obtained by applying different control algorithms and spatial command-input signals. The results show that the efficiency of the control algorithms is closely related to their complexity and cost. In order to check the closeness to reality of the computer simulation results and their benefit for industrial applications, laboratory experiments must be formed with the same MAP, the same control algorithms, and applying the same command-input signals which have been used in the computer simulations. These experimental investigations will be presented in Part II of the paper.     

Shock wave reflection over wedges: a benchmark test for CFD and experiments

In the Shock Wave Journal Vol. 2, No. 4 a benchmark test for shock wave reflection over wedges was announced. International scientists who are interested in shock wave research were invited to participate. The benchmark test aimed at comparison of various advanced numerical schemes as well as experimental results. During the last three years more than twenty results, including both CFD and experiments, were collected from all over the world. Efforts contributed by these scientists made the present benchmark test reach to a standard of the state of the art of the computational fluid dynamics applied to the shock wave research. However, it was regrettable not to publish all the results collected due to limitation on the available page number. Received 5 November 1994 / Accepted 9 September 1996     

ANALYSIS OF GROUNDING CHARACTERISTICS AND STRAIN ENERGY OF RADIAL TIRES WITH RADIAL STIFFNESS1)

利用轮胎综合试验机对径向刚度下子午线轮胎进行性能试验,采用正交试验法针对不同胎压、垂向载荷下轮胎的接地特性进行分析,结合仿真软件ABAQUS与试验进行对比。结果表明,橡胶材料Mooney-Rivli模型也具有一定的适用性,胎压增大时径向刚度发生线性变化,胎面印痕由椭圆形转变成近似矩形,印痕面积略微增大;随着胎压的不断增大,胎面印痕的面积显著减小,接触面的压力主要集中在胎肩,胎冠处也有所增加;胎压一定时,垂向载荷逐渐增大时,整个印痕面的应力呈对称分布,印痕面应力由内高外低逐渐向外高内低变化。建立数学模型与有限元软件同时对轮胎进行应变能分析,发现在低胎压150 kPa下受载荷时轮胎容易发生微小侧向位移同时发生变形,此时极易引起迟滞损失并造成应变能急剧增加。     

相位修正技术及其在大型结构现场动力测试中的应用

本文介绍了相位修正技术、A/D板随动前置放大技术、及其在大型结构现场动力测试分析中的应用.相位修正技术解决了A/D板因轮换采样的时间差引起的频域相位差问题;而随动前置放大技术则解决了实测过程中各测点信噪比悬殊时带来的问题.这些技术的实现,使得以微机为基础的直接现场采样动力分析成为可能.最后的两个实际现场测试分析例子,证明了上述技术在工程实用中的可行性与可靠性.     

用三轴转台减小陀螺加速度表输入失调角的试验研究

为了减小陀螺加速度表输入失调角，从理论上分析了陀螺加速度表输入失调角存在对陀螺加速度表测试精度的影响，提出了利用三轴转台设计减小陀螺加速度表输入失调角的试验方法。试验结果表明，利用三轴转台可以成功地将陀螺加速度表测试精度提高一个数量级。     

我国航空工业中结构分析通用软件的发展及应用前景

简要介绍了国外几个在航空工业中应用的著名结构分析通甩软件的发展情况和趋势,回顾了我国航空工业中结构分析通用软件的发展过程,以表格形式给出我国航空工业部门结构分析软件在运行环境、功能、性能、材料、载荷、前后置处理和用户界面等方面和国外同类软件的比较,和从设计部门对结构分析软件的要求,提出了结构分析通用软件在航空工业中的发展方向和前景。     

列车运行下环形轨道模型振动试验分析

搭建了环形轨道振动试验平台,开展环形轨道振动试验、轨面不平顺振动试验研究。采用INV3062T信号采集仪和INV-9828加速度传感器分别对轨道的横向响应(道床)、纵向响应(轨腰)、轨道表面和扣件支撑处进行加速度信号采集。通过凸起模拟了轨道不平顺,试验分析了轨面不平顺对钢轨动态响应的影响。分析了速度对横波、纵波和轨面不平顺的影响。结果表明:轨道横向振动幅值远大于纵向振动;相邻扣件中点处的振动响应大于扣件处;轨面不平顺会使振动响应增大甚至引起跳动;随着速度的增大,轨道振动位移响应呈上升趋势。     

The effect of temperature on the viscoelastic behavior of linear low-density polyethylene

Summary Observations are reported on linear low-density polyethylene in isothermal torsional oscillation and relaxation tests at various temperatures ranging from room temperature to 110 C. Constitutive equations are derived for the viscoelastic response of a semicrystalline polymer at small strains. The polymer is treated as an equivalent network of strands bridged by junctions (entanglements, physical cross-links on the surfaces of crystallites and lamellar blocks). The network is thought of as an ensemble of meso-regions with various potential energies for rearrangement of strands. Two types of meso-domains are introduced: active, where strands separate from temporary junctions as they are excited by thermal fluctuations, and passive, where detachment of strands is prevented by the surrounding macromolecules. The time-dependent behavior of the ensemble reflects separation of active strands from their junctions and merging of dangling strands with the network. Stress–strain relations are developed by using the laws of thermodynamics. The governing equations involve six material constants that are found by fitting the experimental data. The study focuses on the effects of (i) temperature, (ii) the deformation mode (torsion versus bending), and (iii) the loading program (oscillations versus relaxation) on the adjustable parameters.This work was partially supported by the West Virginia Research Challenge Grant Program     

傅立叶弥散分析在冲击拉伸和冲击压缩试验中的应用

将傅立叶弥散分析方法和程序（ＦＦＴＤＳＰ）应用于冲击拉伸和冲击压缩试验中，分析了输入杆和输出杆中波的弥散效应对试验结果的影响。带有弥散修正的试验结果表明，由于入射脉冲产生方式不同，冲击压缩试验系统中传播的应力波带有显著的弥散效应，而间接杆杆型冲击拉伸试验系统中传播的应力波的弥散效应一般较小。