Molecular Dynamics Study on Fracture Mechanism of Fe-Amorphous Metal (J Integral near Mode I Crack Tip)
Molecular Dynamics Study on Fracture Mechanism of Fe-Amorphous Metal (J Integral near Mode I Crack Tip)
复制标题
Fe非晶金属断裂机理的分子动力学研究（I型裂纹尖端附近的J积分）
DOI：
10.1007/978-3-662-35369-1_7
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
H. Kitagawa
中科院分区：
文献类型：
--
作者：
K. Nakatani;A. Nakatani;H. Kitagawa
在进行裂纹扩展和断裂的分子动力学(MD)模拟时，边界条件通常由基于线弹性的应力强度因子K与材料的初始弹性性质相对应的原子位移决定。然而，我们以前的研究表明，裂纹尖端附近会出现很高的应变[1]，并且由于大应力集中下的非弹性变形，初始力学性能会随着弹性常数的降低而改变[2]。因此，线弹性条件(小尺度屈服)的假设不再实现，基于线弹性解的边界条件不再适用。J积分是连续介质力学中常给出裂纹扩展判据的具有代表性的力学参数之一，为了定量研究裂纹尖端附近损伤机械场的力学状态，本文在原子化的Fe-非晶态模型中对J积分进行了估算，J积分实际上是用在MD模拟中具有优势的J*来估算的。为了评价裂纹尖端附近的损伤力学场，对控制边界原子位移的边界条件下Fe-非晶态金属中的I型裂纹扩展进行了分子动力学模拟，并求出了J*。结果表明，力学性能的变化与材料的非线性和钝化形状有关，并通过选择合适的积分区域，利用J*积分对其进行了定量预测。
When molecular dynamics (MD) simulation of crack propagation and fracture is carried out, it is very common that the boundary conditions are determined by the atomic displacement which correspond to a stress intensity factorKbased on linear elasticity with the initial elastic properties of the material. However, in our previous studies, it was shown that a very high strain occurs near the crack tip [1], and the initial mechanical properties are changed as the elastic constants decrease because of non-elastic deformation under large stress concentration [2]. Therefore, the assumption of a linear elastic condition (small scale yielding) cannot be realized any longer and the boundary condition based on a linear elastic solution is no longer applicable. In this paper, the J integral, which is one of the representative mechanical parameters that often gives the criterion of crack propagation in continuum mechanics, is evaluated in an atomistic Fe-amorphous model in order to investigate quantitatively the mechanical state of the damaged mechanical field near the crack tip.Jis actually evaluated byJ* which is advantazeous in MD simulations. The molecular dynamics simulations of mode I crack propagation in Fe-amorphous metal under the boundary condition which controlled displacements of boundary atoms are carried out for the purpose of evaluating the damaged mechanical field near the crack tip, andJ* is evaluated. As a result, it is shown that the change of mechanical properties is concerned with the material non-linearity and the blunting shape, and that it is predicted quantitatively by using the J* integral which is evaluated by choosing the appropriate integral region.