纤维金属层板(Fibre metal laminates,FMLs)具有优异的综合力学性能,现已成功应用于航空等领域。高速冲击性能是FMLs重要的力学性能指标之一,然而由于FMLs高速冲击破坏机制的复杂性,目前对其高速冲击性能的研究还处于起步阶段。鉴于此,...纤维金属层板(Fibre metal laminates,FMLs)具有优异的综合力学性能,现已成功应用于航空等领域。高速冲击性能是FMLs重要的力学性能指标之一,然而由于FMLs高速冲击破坏机制的复杂性,目前对其高速冲击性能的研究还处于起步阶段。鉴于此,本文在综述FMLs力学性能的基础上,重点从实验研究和有限元模拟等方面讨论了FMLs高速冲击性能研究现状,最后提出了FMLs力学性能现有研究中存在的一些问题和未来潜在的发展方向。展开更多
In many cases, preventing permafrost from further thaw due to human activities might be the first choice for embankment design in permafrost regions. 2-D finite element analysis was conducted in this paper, in which p...In many cases, preventing permafrost from further thaw due to human activities might be the first choice for embankment design in permafrost regions. 2-D finite element analysis was conducted in this paper, in which phase change was taken into consideration to simulate the thermal regime of the Qinghai-Tibetan Railway with Expandable Polystyrene (EPS). Based on the predicted maximum thaw depth in the following 50 year, the best position for insulation was presented and the relationship between the thickness of insulation and the height of embankment was analyzed. Besides, the applicable range of insulation in embankment engineering of the Qinghai-Tibetan Railway in terms of Mean Annual Air Temperature (MAAT) was suggested and the influence of geothermal field of permafrost on the applicable range of the insulation was discussed.展开更多
In permafrost regions of Qinghai-Tibetan Plateau, the critical embankment height must be considered in the process of the construction of highway, especially for the global climatic warming. In this paper, the two-dim...In permafrost regions of Qinghai-Tibetan Plateau, the critical embankment height must be considered in the process of the construction of highway, especially for the global climatic warming. In this paper, the two-dimensional numerical analysis for the critical embankment height (for gravel road surface and coarse-grained soil) has been performed by using the finite element method. In the calculation, we think that the service life of the construction is at least 50 years. The mean annual air temperatures applied to the calculation model are -6.5 ℃, -6.0 ℃, -5.5 ℃, -5.0 ℃, -4.5 ℃ and -4.0 ℃, respectively, and the value of temperature rise are taken as 1.10℃ in the coming 50 years. The minimum embankment heights derived from the analysis are 0\^85 m, 0\^92 m, 1\^01 m, 1\^18 m, 1\^60 m and 2\^66 m for the different mean annual air temperatures and the maximum embankment heights are 7\^68 m, 7\^55 m, 7\^34 m, 7\^00 m, 6\^45 m and 5\^85m, accordingly. On condition that the service life of embankment is 50 years, the critical value of the mean annual air temperature is -3\^5 ℃. Namely, in the areas where the mean annual air temperature is higher than -3\^5 ℃, the critical embankment height does not exist.展开更多
The present study considers mathematical classification of the time differential operators and then applies methods of approximation in time such as Galerkin method (GM ), Galerkin method with weak form (GM / WF ), Pe...The present study considers mathematical classification of the time differential operators and then applies methods of approximation in time such as Galerkin method (GM ), Galerkin method with weak form (GM / WF ), Petrov-Galerkin method ( PGM), weighted residual method (WRY ), and least squares method or process ( LSM or LSP ) to construct finite element approximations in time. A correspondence is established between these integral forms and the elements of the calculus of variations: 1) to determine which methods of approximation yield unconditionally stable (variationally consistent integral forms, VC ) computational processes for which types of operators and, 2) to establish which integral forms do not yield unconditionally stable computations (variationally inconsistent integral forms, VIC ). It is shown that variationally consistent time integral forms in hpk framework yield computational processes for ODEs in time that are unconditionally stable, provide a mechanism of higher order global differentiability approximations as well as higher degree local approximations in time, provide control over approximation error when used as a time marching process and can indeed yield time accurate solutions of the evolution. Numerical studies are presented using standard model problems from the literature and the results are compared with Wilson’s θ method as well as Newmark method to demonstrate highly meritorious features of the proposed methodology.展开更多
基于带定位格架类三角形子通道超临界水流动传热试验,数值研究了棒径为8 mm,栅距比为1.4的超临界水冷堆(Supercritical Water Cooled Reactor,SCWR)类三角形通道超临界流动传热定位格架结构影响,分析了同型定位格架典型结构参数和不同...基于带定位格架类三角形子通道超临界水流动传热试验,数值研究了棒径为8 mm,栅距比为1.4的超临界水冷堆(Supercritical Water Cooled Reactor,SCWR)类三角形通道超临界流动传热定位格架结构影响,分析了同型定位格架典型结构参数和不同定位格架型式对堆芯通道超临界流动传热特性的影响规律。研究结果表明:定位格架可强化堆芯通道超临界水传热,同型格架本体厚度越大,压力损失越高,格架处壁面温度越低,局部换热能力越好,当增大格架本体厚度,弱化程度无明显差异;阻流片型定位格架下游局部换热能力提高显著,阻流片直径越大,上游压力越大,局部壁温越低,换热系数越高,增大阻流片直径可减小传热弱化区域大小,强化传热能力;不同定位格架型式对比研究发现交错叶片型弱化区域最大,阻流片型定位格架弱化区域最小,阻流片型定位格架具有最佳的传热强化效果。展开更多
文摘纤维金属层板(Fibre metal laminates,FMLs)具有优异的综合力学性能,现已成功应用于航空等领域。高速冲击性能是FMLs重要的力学性能指标之一,然而由于FMLs高速冲击破坏机制的复杂性,目前对其高速冲击性能的研究还处于起步阶段。鉴于此,本文在综述FMLs力学性能的基础上,重点从实验研究和有限元模拟等方面讨论了FMLs高速冲击性能研究现状,最后提出了FMLs力学性能现有研究中存在的一些问题和未来潜在的发展方向。
文摘In many cases, preventing permafrost from further thaw due to human activities might be the first choice for embankment design in permafrost regions. 2-D finite element analysis was conducted in this paper, in which phase change was taken into consideration to simulate the thermal regime of the Qinghai-Tibetan Railway with Expandable Polystyrene (EPS). Based on the predicted maximum thaw depth in the following 50 year, the best position for insulation was presented and the relationship between the thickness of insulation and the height of embankment was analyzed. Besides, the applicable range of insulation in embankment engineering of the Qinghai-Tibetan Railway in terms of Mean Annual Air Temperature (MAAT) was suggested and the influence of geothermal field of permafrost on the applicable range of the insulation was discussed.
文摘In permafrost regions of Qinghai-Tibetan Plateau, the critical embankment height must be considered in the process of the construction of highway, especially for the global climatic warming. In this paper, the two-dimensional numerical analysis for the critical embankment height (for gravel road surface and coarse-grained soil) has been performed by using the finite element method. In the calculation, we think that the service life of the construction is at least 50 years. The mean annual air temperatures applied to the calculation model are -6.5 ℃, -6.0 ℃, -5.5 ℃, -5.0 ℃, -4.5 ℃ and -4.0 ℃, respectively, and the value of temperature rise are taken as 1.10℃ in the coming 50 years. The minimum embankment heights derived from the analysis are 0\^85 m, 0\^92 m, 1\^01 m, 1\^18 m, 1\^60 m and 2\^66 m for the different mean annual air temperatures and the maximum embankment heights are 7\^68 m, 7\^55 m, 7\^34 m, 7\^00 m, 6\^45 m and 5\^85m, accordingly. On condition that the service life of embankment is 50 years, the critical value of the mean annual air temperature is -3\^5 ℃. Namely, in the areas where the mean annual air temperature is higher than -3\^5 ℃, the critical embankment height does not exist.
文摘The present study considers mathematical classification of the time differential operators and then applies methods of approximation in time such as Galerkin method (GM ), Galerkin method with weak form (GM / WF ), Petrov-Galerkin method ( PGM), weighted residual method (WRY ), and least squares method or process ( LSM or LSP ) to construct finite element approximations in time. A correspondence is established between these integral forms and the elements of the calculus of variations: 1) to determine which methods of approximation yield unconditionally stable (variationally consistent integral forms, VC ) computational processes for which types of operators and, 2) to establish which integral forms do not yield unconditionally stable computations (variationally inconsistent integral forms, VIC ). It is shown that variationally consistent time integral forms in hpk framework yield computational processes for ODEs in time that are unconditionally stable, provide a mechanism of higher order global differentiability approximations as well as higher degree local approximations in time, provide control over approximation error when used as a time marching process and can indeed yield time accurate solutions of the evolution. Numerical studies are presented using standard model problems from the literature and the results are compared with Wilson’s θ method as well as Newmark method to demonstrate highly meritorious features of the proposed methodology.
文摘基于带定位格架类三角形子通道超临界水流动传热试验,数值研究了棒径为8 mm,栅距比为1.4的超临界水冷堆(Supercritical Water Cooled Reactor,SCWR)类三角形通道超临界流动传热定位格架结构影响,分析了同型定位格架典型结构参数和不同定位格架型式对堆芯通道超临界流动传热特性的影响规律。研究结果表明:定位格架可强化堆芯通道超临界水传热,同型格架本体厚度越大,压力损失越高,格架处壁面温度越低,局部换热能力越好,当增大格架本体厚度,弱化程度无明显差异;阻流片型定位格架下游局部换热能力提高显著,阻流片直径越大,上游压力越大,局部壁温越低,换热系数越高,增大阻流片直径可减小传热弱化区域大小,强化传热能力;不同定位格架型式对比研究发现交错叶片型弱化区域最大,阻流片型定位格架弱化区域最小,阻流片型定位格架具有最佳的传热强化效果。
