采用基于机制的应变梯度塑性的传统理论(CMSG), 对具有不同尺寸的铜纳米晶粒及孪晶的应力--应变关系进行了有限元模拟. 在分析中提出了孪晶薄层强化带的概念并用粘聚力模型模拟晶界的滑移和分离现象, 给出了在单向拉伸条件下不同厚度孪晶薄层和不同材料参数对孪晶铜总体应力-应变关系的影响, 同时也给出了晶粒中孪晶薄层取向分布对孪晶铜应力-应变关系的影响. 数值模拟结果显示: 随着晶粒尺寸和孪晶薄层间距的减小, 应变梯度效应逐渐增强, 材料强化效果越明显; 孪晶薄层的取向分布对材料整体的力学性能有较大影响, 并且随着晶粒及孪晶薄层间距的减小, 孪晶薄层取向的影响也越来越小. 最后, 有限元计算结果与实验数据进行了对比分析.
The stress-strain relations of nanocrystalline twin copper with different size grains and twins are studied by using FEM simulations based on the conventional theory of mechanism-based strain gradient plasticity (CMSG). The concept of twin lamellae strengthening zone is proposed in our analysis with a cohesive interface model to simulate grain-boundary sliding and separation. Roles of many material parameters affecting stress-strain curves of polycrystalline twin copper are studied in detail. Furthermore, the effects of both twin lamellar spacing and twin lamellar distribution on the stress-strain relations are investigated under tension loading. The numerical simulations show that: both the strain gradient effect and the material hardening increase with decreasing the grain size and twin lamellar spacing. The distributions of twin lamellae have a significant influence on the general mechanical properties, and the effect will become into small with decreasing the grain and twin lamellar spacing. Finally, the prediction results of FEM are compared with the data of several experiments.
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