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  • Most researches on the static performance of stiffened panel joined by friction stir welding(FSW) mainly focus on the compression stability rather than shear stability. To evaluate the potential of FSW as a replacement for traditional rivet fastening for stiffened panel assembly in aviation application, finite element method(FEM) is applied to compare compression and shear stability performances of FSW stiffened panels with stability performances of riveted stiffened panels. FEMs of 2024-T3 aluminum alloy FSW and riveted stiffened panels are developed and nonlinear static analysis method is applied to obtain buckling pattern, buckling load and load carrying capability of each panel model. The accuracy of each FEM of FSW stiffened panel is evaluated by stability experiment of FSW stiffened panel specimens with identical geometry and boundary condition and the accuracy of each FEM of riveted stiffened panel is evaluated by semi-empirical calculation formulas. It is found that FEMs without considering weld-induced initial imperfections notably overestimate the static strengths of FSW stiffened panels. FEM results show that, buckling patterns of both FSW and riveted compression stiffened panels represent local buckling of plate between stiffeners. The initial buckling waves of FSW stiffened panel emerge uniformly in each plate between stiffeners while those of riveted panel mainly emerge in the mid-plate. Buckling patterns of both FSW and riveted shear stiffened panels represent local buckling of plate close to the loading corner. FEM results indicate that, shear buckling of FSW stiffened panel is less sensitive to the initial imperfections than compression buckling. Load carrying capability of FSW stiffened panel is less sensitive to the initial imperfections than initial buckling. It can be concluded that buckling loads of FSW panels are a bit lower than those of riveted panels whereas carrying capabilities of FSW panels are almost equivalent to those of riveted panels with identical geometries. Finite element method for simulating static performances of FSW and riveted stiffened panels is proposed and evaluated and some beneficial conclusions are obtained, which offer useful references for analysis and application of FSW to replace rivet fastening in aviation stiffened panel assembly.
     - 中国机械工程学报
    文章来源: 万方数据
  • 国际资本流动对经济增长的影响分析-基于国际数据的实证研究

    基于1994~2009年68个国家的年度数据构建Panel Data变截距固定效应模型,通过对资本流向和流动方式的进一步细分,来考察资本流动对不同发展水平国家经济增长的影响.结果显示:境外国际资本流入对转型国家经济增长的促进作用明显强于发达国家,对发展中国家经济效应不显著;国际资本流出仅对发达国家经济增长有显著的促进作用,对发展中国家和转型国家的经济效应均不显著.
    侯晓霞 - 经济问题
    文章来源: 万方数据
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