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Effect of Tip Roundness on the Nanoindentation of Fe Crystals
Tribology Letters ( IF 3.2 ) Pub Date : 2020-04-07 , DOI: 10.1007/s11249-020-01295-9
M. Clara Zonana , Carlos J. Ruestes , Eduardo M. Bringa , Herbert M. Urbassek

Indentation tips are never atomically sharp, but rounded at their end. We use atomistic simulation to study the effect of tip roundness for the particular case of a cube-corner pyramidal indenter by comparing the results of a spherical, a sharp cube-corner, and a rounded cube-corner tip during indention into bcc Fe. We find that as soon as the tip has indented so deeply that the spherical geometry does not hold any longer, strong deviations between the dislocation plasticity behavior show up. The rounded cube-corner tip produces less dislocations and a smaller plastic zone than the spherical indenter, when indented to the same depth. The results are better comparable, however, when the same displaced volume is considered. Finally, the dislocation nucleation mode is affected by the geometry, changing from homogeneous to heterogeneous nucleation as the tip changes from rounded to sharp. The cube-corner tips are found to produce more twinning and delay the formation of prismatic loops. For a penetration depth beyond the radius of the rounded cube-corner tip, atomic sharp pyramidal tips produce similar quantitative (hardness, dislocation density) and qualitative (pileup, dislocation arrangement) results compared to its rounded counterpart. Our results will prove important for understanding the differences between spherical indenter tips, as they are often used in simulation, and pyramidal tips, as they are used in experiment.

中文翻译:

尖端圆度对铁晶体纳米压痕的影响

压痕技巧从不尖锐,而是在其末端变圆。我们使用原子模拟通过比较在压成bcc Fe的过程中比较球形,尖锐的立方角和圆形的立方角尖端的结果,来研究特殊情况下立方角锥形压头的尖端圆度的影响。我们发现,一旦尖端压入深度太深以至于球形几何形状不再固定,位错可塑性行为之间就会出现强烈的偏差。与球形压头相比,当压入相同深度时,圆形的角锥尖端产生的位移更少,塑性区更小。但是,当考虑相同的排量时,结果具有更好的可比性。最后,位错成核模式受几何形状的影响,当尖端从圆形变为尖锐时,从均质成核到异质成核。发现立方角尖端可产生更多的孪晶并延迟棱形环的形成。对于超出圆形立方角尖端半径的穿透深度,与圆形同类相比,原子尖锐的锥形尖端产生相似的定量(硬度,位错密度)和定性(堆积,位错排列)结果。我们的结果将证明对于理解通常用于模拟的球形压头尖端和用于实验的金字塔形尖端之间的区别非常重要。与四舍五入的圆锥形尖端相比,原子尖的棱锥尖端产生相似的定量(硬度,位错密度)和定性(堆积,位错排列)结果。我们的结果将证明对于理解通常用于模拟的球形压头尖端和用于实验的金字塔形尖端之间的区别非常重要。与四舍五入的圆锥形尖端相比,原子尖的棱锥尖端产生相似的定量(硬度,位错密度)和定性(堆积,位错排列)结果。我们的结果将证明对于理解通常用于模拟的球形压头尖端和用于实验的金字塔形尖端之间的区别非常重要。
更新日期:2020-04-07
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