Materials Science and Engineering: A ( IF 6.4 ) Pub Date : 2018-11-06 , DOI: 10.1016/j.msea.2018.11.019 Sandeep P. Patil , Vinayak G. Parale , Hyung-Ho Park , Bernd Markert
The nanomechanics during the indentation test on low-density nanoporous silica aerogels remains one of the least understood and explored areas of mechanics. In the present work, we performed nanoindentation using a spherical indenter on silica aerogels to investigate the mechanical properties, such as elastic modulus and hardness, and also, the deformation behaviour. Using all-atom simulations on large samples, the elastic modulus is computed from the elastic part of force–depth curves that can be fitted to the Hertz law, which shows that it increases with density. We proposed a novel approach to calculate the projected true contact area in nanoindentation and to estimate an accurate hardness of silica aerogel, which has a highly complex and randomly arranged network of atoms structure. The experimental studies of nanoindentation are performed on silica aerogel, which reveals that the measured elastic modulus is in good agreement with the simulations. However, the measured hardness values are nearly close to the projected contact area method. It suggests that in all-atom simulations the computed high hardness values using the proposed true area method are the actual local contact pressure. This new understanding may help to expand the use of computer simulations to explore the nanoindentation processes at the molecular level and to advance the macroscopic hardness calculation.
中文翻译:
纳米多孔二氧化硅气凝胶上的纳米压痕的分子动力学和实验研究
在低密度纳米多孔二氧化硅气凝胶的压痕测试过程中,纳米力学仍然是最缺乏了解和探索的力学领域之一。在目前的工作中,我们使用球形压头在二氧化硅气凝胶上进行了纳米压痕,以研究机械性能,例如弹性模量和硬度,以及变形行为。通过对大型样品进行全原子模拟,可根据赫兹定律拟合出力-深度曲线的弹性部分来计算弹性模量,这表明弹性密度随密度的增加而增加。我们提出了一种新颖的方法来计算纳米压痕中预计的实际接触面积,并估计二氧化硅气凝胶的精确硬度,该二氧化硅气凝胶具有高度复杂且随机排列的原子结构网络。纳米压痕的实验研究是在二氧化硅气凝胶上进行的,这表明所测得的弹性模量与模拟结果吻合良好。但是,测得的硬度值几乎接近于投影接触面积法。这表明在所有原子模拟中,使用建议的真实面积方法计算出的高硬度值是实际的局部接触压力。这种新的理解可能有助于扩大计算机模拟的使用,以在分子水平上探索纳米压痕过程并推进宏观硬度计算。这表明在所有原子模拟中,使用建议的真实面积方法计算出的高硬度值是实际的局部接触压力。这种新的理解可能有助于扩大计算机模拟的使用,以在分子水平上探索纳米压痕过程并推进宏观硬度计算。这表明在所有原子模拟中,使用建议的真实面积方法计算出的高硬度值是实际的局部接触压力。这种新的理解可能有助于扩大计算机模拟的使用,以在分子水平上探索纳米压痕过程并推进宏观硬度计算。