Mechanics of Amorphous Metals (Elastic-Plastic Finite Element Analyses Using Inhomogeneous Defects Theory)
Mechanics of Amorphous Metals (Elastic-Plastic Finite Element Analyses Using Inhomogeneous Defects Theory)
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DOI：
10.1299/kikaia.79.1807
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
Y. Shibutani;M. Wakeda;Takamasa Yoshikawa
中科院分区：
文献类型：
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作者：
Y. Shibutani;M. Wakeda;Takamasa Yoshikawa
非晶金属的塑性变形依赖于平均应力（静水压力），即由于原子结构的随机性而具有可压缩性。这种特性导致了它们在变形上的本征各向异性。此外，在弹性区之后出现的局部剪切带不允许有足够的伸长。这是这种材料的关键缺点，人们一直在努力克服它。本文建立了基于非齐次缺陷理论的本构律和缺陷密度（相当于自由体积）的演化律，并给出了平均应力相关屈服函数。本构和缺陷演化规律中使用的几个参数与实验结果拟合。首先采用单单元模型进行有限元分析，以获得完全均匀的变形。在室温下得到了不同多轴应力状态下的屈服曲线。采用弹性极限作为屈服应力，Drucker-Prager屈服准则中参数κ为0.09，预测结果与有限元解吻合较好。在块体模型下，缺陷密度初始波动时的单轴变形行为在最大值点后呈现局部剪切带，且剪切带与应力轴的各向异性角度与实验及其他计算结果一致。
Plastic deformation of amorphous metals is dependent on a mean stress (hydrostatic pressure), that is, compressible due to the random atomic structure. This property leads their intrinsic anisotropy on deformation. In addition, the localized shear bands occurring just after an elastic region do not allow the sufficient elongation. This is the crucial drawback of that material which has been strongly tried to overcome. In the present paper, a constitutive law based on the inhomogeneous defects theory and an evolutional law of defects density (equivalent to free volume) were formulated with the mean stress-dependent yield function. Several parameters used in the constitutive and the defects evolution laws were fitted to the experimental results. Finite element analyses were first performed using one element model to obtain the perfectly uniform deformation. Yield curves under some multiaxial stress states were obtained at room temperature. Employing the elastic limit as a yield stress and the parameter κ of 0.09 in Drucker–Prager yield criterion, the prediction agrees well to the FEM solutions. The uniaxial deformation behavior with an initial fluctuation of defects density using a block model, then, exhibits the localized shear bands after the maximum point, and the anisotropic angles of such bands to the stress axis were coincident with the experimental and the other computational results.