Effect of interference fits on the fatigue lives of bolted composite joints

The effect of interference fits on the fatigue lives of bolted composite joints is investigated by conducting mechanical tests. Static and fatigue tests are carried out on specimens made of carbon-bismaleimide composites joined together as double-lap single-bolt joints. The bolts having interference fits ranging of 0 (neat fit), 0.5%, 0.75% and 1% are performed. The results demonstrate the relationship between fatigue life and different values of interference fits. After the fatigue tests, non-destructive evaluation (NDE) and scanning electron microscope (SEM) are used to observe the damage of the surrender and surface of the hole. The test results show that the interference fitted specimens have improved fatigue life compared to the neat fitted specimen. The NDE and SEM results reveal that the damage degree of interference fitted specimen is weaker than that for the neat fitted one.     

Calculation of strain amplification matrix for strain invariant failure theory based on representative volume element models with periodical boundary condition

Strain invariant failure theory (SIFT) is a micro-mechanics-based failure theory for multi-scale failure analysis of composite materials originally proposed by Gosse and Christensen. In this paper, the approach for obtaining strain amplification matrix which is a key step for the execution of SIFT is improved by adopting representative volume element (RVE) finite element models considering periodical boundary condition, based on which more actual deformation mode is reflected. The deformation modes and strain data at the characteristic points of the centroid cell of multi-cell RVE model are analyzed and taken as a reference. It can be concluded that more reasonable deformation mode and relationship between the micro-mechanical and macro-mechanical strain states are obtained by employing the new model. Finally, numerical examples are provided to illustrate the determination of strain amplification factors within the RVEs considering periodical boundary condition at the characteristic points.     

城市公共空间活力评价体系研究

从城市公共空间使用者感受空间活力的角度,通过遴选城市公共空间活力影响因子,以问卷调查为基础,借助统计分析软件,运用层次分析法和专家评分法,建立了量化的城市公共空间活力评价体系,为制定建设和发展宜人的城市公共空间与和谐的现代化城市策略提供依据。     

公路软土地基处理技术分析

主要分析了公路软土路基的特征以及其危害。处软土路基的方法有很多,介绍公路软土路基常见的几种处理方法,针对不同的软土地基类型来采取不同类型软基的处理方法,从而提高公路的质量。     

构筑中国沿海发展轴的骨干——建设上海北至大连、南至香港沿海大铁路

<正> 一、构筑沿海综合交通走廊势在必行 中国东部沿海地带,土地面积占全国13％,人口占41％。目前,该地带工农业总产值已占全国59％,国民生产总值占52％;不到1/7的国土,构成中国经济的半壁江山。今后,随着沿海开放的深化、香港、澳门的回归和中国统一进程的加速,沿海地带将出现四个巨大城市群:①以北京、天津、大连为中心的环渤海城市群;②以上海、南京、杭州为中心的长江三角洲城市群;③以厦门、福州、台北为中心的闽台海峡城市群;④以广州、香港、澳门为中心的珠江三角洲城市群。这四大城市群,集中了全国最先进和最庞大的生产力、创新力和影响力,是带动中国现     

风雨同车

我的桑塔纳是1997年买的，当时最大的感觉是——“我有车了!!”，无限的高兴，心里面跟沸腾的开水一样。咕嘟咕嘟的一直在冒着喜悦的泡泡。我当时最大的愿望就是带着全家老小在全市兜一圈。     

基于计算机技术的纸质海图改正新方法

此文提出了一种基于计算机技术的纸质海图改正新方法。它利用软件的方法实现了改正内容的计算机输入、定位、绘制和打印输出等功能，有效克服了目前国内外在纸质海图改正过程中存在的劳动强度大、效率低以及改正内容定位精度低、容易出差错筝问题，是纸质海图改正技术的革新。     

Analysis of through-the-thickness stress distribution in thick laminate multi-bolt joints using global-local method

The stress distribution surrounding the fastener hole in thick laminate mechanical joints is complex. It is time-consuming to analyze the distribution using finite element method. To accurately and efficiently obtain the stress state around the fastener hole in multi-bolt thick laminate joints, a global-local approach is introduced. In the method, the most seriously damaged zone is 3D modeled by taking the displacement field got from the 2D global model as boundary conditions. Through comparison and analysis there are the following findings: the global-local finite element method is a reliable and efficient way to solve the stress distribution problem; the stress distribution around the fastener hole is quite uneven in through-the-thickness direction, and the stresses of the elements close to the shearing plane are much higher than the stresses of the elements far away from the shearing plane; the out-of-plane stresses introduced by the single-lap joint cannot be ignored due to the delamination failure; the stress state is a useful criterion for further more complex studies involving failure analysis.