基于应变率影响的纳晶材料本构模型

Investigation of Constitutive Modeling for Nanocrystalline Materials Under Effects of Strain Rate

建立了一种包含规则的晶内相和塑性软化晶界位错堆积区相的双相混合模型来研究应变率对纳米晶材料力学性能的影响。根据相混合模型,建立了一种全新的以位错密度演化机制和应变梯度理论为基础的应力-应变本构关系。将本构模型计算结果与实验结果对比发现,两者符合得很好,但数值模拟表现出应变硬化行为。计算发现,由于位错线长度的降低,纳晶材料的应变率敏感系数远远高于粗晶材料。

To evaluate the influences of strain rate on mechanical behavior of nanocrys- talline （NC） materials, a phase mixture model composed of ordered grain interior and plastically softer grain boundary dislocation pile up zone was built. With the help of mixture mode, a new stress-strain constitutive relation was firstly established based on dislocation density evolution and strain gradient theory. The calculated data were then compared with experimental curves and the prediction kept in good agreement with ex- periment. Duo to the reduction of dislocation line length of NC materials leaded the strain rate sensitivity to be larger than that of coarse grain materials.