ハイブリッドポテンシャル法を用いた鉄ナノ多結晶体中のき裂進展挙動の分子動力学解析

概要

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It is well known that the fracture toughness of coarse grained materials is usually improved as the grain size is reduced. However, there are different views on the dependence of fracture property of nanocrystalline materials on the grain size. In this study, we evaluated the influences of grain size on the crack growth behavior in nanocrystalline Fe by the use of Molecular Dynamics (MD) simulations. In order to treat the crack growth in the complicated material, it is important to employ an accurate interatomic potential and a large simulation model which contains many atoms. Here we use the hybrid potential method which combines both accuracy and computational costs by switching interatomic potentials according to the local atomic structure. The crack growth resistance is estimated at two different deformation speeds by the use of crack opening angle. It is revealed that the resistance increases as the grain size is reduced in the case of slower deformation speed. In contrast, the resistance decreases as the grain size is reduced in the case of faster deformation speed. We also show that the grain size dependence of the fracture property is closely related to the shape and size of non-crystallized region which appears around crack tip.
社団法人日本機械学会の論文
2007-09-25