In order to improve aero engine performance, it is necessary to reduce the welding residual stress of aero engine blisk. In this paper, finite element method was employed to simulate electron beam welding process of b...In order to improve aero engine performance, it is necessary to reduce the welding residual stress of aero engine blisk. In this paper, finite element method was employed to simulate electron beam welding process of blisk, in accordance with the deducing formula（ p = kh ） , the heat input is changed with the weld depth to control welding residual stress of blisk. The calculation results show that welding residual stress of blisk can be controlled effectively by reducing the heat input on the conditions of meeting the demand of weld penetration and guaranteeing the welding quality, a new theoretical method and some numerical data are provided for controlling welding residual stress of blisk.展开更多
基金The research was supported by Postdoctoral Science Foundation of China （No. 20070410900） and Heilongjiang Postdoctoral Fund （No. LBH-Z07129 ）.
文摘In order to improve aero engine performance, it is necessary to reduce the welding residual stress of aero engine blisk. In this paper, finite element method was employed to simulate electron beam welding process of blisk, in accordance with the deducing formula（ p = kh ） , the heat input is changed with the weld depth to control welding residual stress of blisk. The calculation results show that welding residual stress of blisk can be controlled effectively by reducing the heat input on the conditions of meeting the demand of weld penetration and guaranteeing the welding quality, a new theoretical method and some numerical data are provided for controlling welding residual stress of blisk.
文摘当前300 m级高拱坝的抗震性能评估已经普遍采用基于坝体-地基动力相互作用的分析模型,然而,包含地基的分析模型底部地震动输入边界的水平空间尺度可以达到几千米,空间跨度大,显然不应忽略地震动在模型水平外边界上的不均匀性,尤其是在近断层地震动作用下。为研究模型外边界均匀地震动输入对拱坝动力响应的影响,以某270 m高度的高拱坝为例,采用ETA(Event Tree Analysis)方法对比分析了均匀输入和考虑行波效应的非均匀输入对拱坝位移、应力和损伤响应的影响。研究发现,相对于均匀输入得到的拱坝应力响应结果,考虑行波效应的拱坝应力响应部分区域的最大拱向应力增大,而最大梁向应力减小,且地震动输入侧的应力增大明显;相对于均匀输入,考虑行波输入的坝体损伤响应规律主要是对坝面上的损伤有所减小,而对拱端处及坝底的损伤有所增大;从坝顶相对坝底的最大位移可以看出,行波输入相对于均匀输入的坝顶位移增大明显,且从空间上来看,在靠近左岸的坝体坝顶位移向上游增大明显,坝顶位移随着向右岸移动而不断减小,靠近右岸的坝体坝顶位移向下游增大明显。
文摘通过焊接热模拟研究了在超大线能量下焊接时Al元素、Mg元素和Ti元素含量对EH36高强船板钢热影响区粗晶区组织、性能的影响规律,采用Thermo-Calc热力学计算与SEM,EDS测试相结合的方法揭示了Al元素、Mg元素和Ti元素含量与母材中氧化物类型、尺寸、数量及粗晶区相变的关系.结果表明,Al_(2)O_(3)无法诱导针状铁素体相变,当Al元素质量分数低于0.005%时,钢中可形成Mg元素、Ti元素或其复合氧化物,可促进粗晶区针状铁素体相变.Mg元素和Ti元素联合添加时,当Mg元素质量分数由0.0042%降低为0.0013%,氧化物类型由MgO转变为Mg_(2)TiO_(4),经统计20个视场内的氧化物数量由408个提高到503个,平均直径由1.37μm减小到1.10μm,显著提高了非均匀形核的比表面积,抑制了晶界铁素体的形成,使t8/5=300 s时粗晶区热模拟试样-20℃冲击吸收能量由43 J提升到127 J.
