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日本機械学会学術誌(英文)年間アクセス数トップ10

机译:日本机械工程学会(英文)年度访问数十大

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The paper provides a brief introduction to the near-wall problem of LES and how it can be solved through modeling of the near-wall turbulence. The distinctions and key differences between different approaches are emphasized, both in terms of fidelity (LES, wall-modeled LES, and DES) and in terms of different wall-mod-eled LES approaches (hybrid LES/RANS and wall-stress-modcls)- The focus is on approaches that model the wall-stress directly, i.e., methods for which the LES equations arc formally solved all the way down to the wall. Progress over the last decade is reviewed, and the most important and promising directions for future research are discussed. In this study, we investigated the mechanism of the indentation size cflrcl tin- whose ciAstal stnulurc is hexagonal closc-patkcd. Indentation tests were performed for two types of single-crystalTi with different crystal orientations: (0001)and (1120). Indentation tests were also performed with difTcrent indenter directions. The hardness depends on the crystal orientation and indenter direction because Ti has large anisotropy. The shape of the impression also changes with the crystal orientation and indenter direction. The hardness increases with decreasing penetration depth for the (0001) and (1120) orientations, so the indentation size effect occurs. For the (0001)orientation, a sudden rapid increase in displacement occurs during indentation tests owing to twinning.This sudden rapid increase in displacement causes a rapid decrease in the hardness. Electron backscattcr diffraction was performed around the impressions to measure the geometrically necessary (GN) dislocation density. The GN dislocation density increases with decreasing penetration depth for the (0001) and (1120) orientations. This trend corresponds to strain gradient theory. The reason for the indentation size effect in Ti is the increase in the GN dislocation density. For the (0001) orientation, the indentation size effect also can be attributed to twinning. Considering both our previous study and this study, the experimental results correspond to strain gradient theory in many cases.
机译:本文简要介绍了LES的近壁问题以及如何通过近壁湍流建模解决。不同方法之间的区别和关键差异是强调的,无论是在保真度(LES,壁图,LES和DES)方面,以及在不同的墙壁 - MOD-ELED LES方法方面(混合LES / RANS和WALL-RENUMAL-MODCLS) ) - 重点是直接模拟壁应力的方法,即LES等式弧形地正式地向墙体解决的方法。讨论了过去十年的进展,讨论了未来研究最重要和最有希望的指示。在这项研究中,我们研究了缩进尺寸CFLRCL锡的机制 - 其CFLRCL TIN-其CIASTAL STNULURC是六边形CLOSC-PATKCD。对具有不同晶体取向的两种类型的单晶TI进行压痕试验:(0001)和(1120)。还使用不同的压紧方向进行压痕试验。硬度取决于晶体取向和压紧方向,因为Ti具有大的各向异性。印象的形状也随着晶体取向和压紧方向而变化。硬度随着(0001)和(1120)取向的渗透深度而增加,因此发生凹痕尺寸效应。对于(0001)取向,由于Twinning,在压痕试验期间发生位移的突然发生。这种位移的突然迅速增加导致硬度快速降低。在墨水周围进行电子反谱衍射,以测量几何必要(GN)位错密度。由于(0001)和(1120)取向的渗透深度降低,GN位错密度增加。这种趋势对应于应变梯度理论。 Ti缩进尺寸效果的原因是GN位错密度的增加。对于(0001)方向,缩进尺寸效果也可以归因于孪生。考虑到我们之前的研究和本研究,实验结果在许多情况下对应于应变梯度理论。

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    《日本機械学会誌》 |2020年第1222期|40-41|共2页
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