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由微米级粗晶颗粒和纳米级纳晶颗粒组成的纳米晶双峰材料不仅具有高强度,还具有较高的延性。根据Taylor强度理论和Johnson-Cook模型提出纳米晶双峰材料的一个新的本构模型,研究了晶粒尺寸和纳米裂纹对纳晶双峰材料本构及失效行为的影响,并进行了数值计算。结果表明,模型预测的结果与实验结果有很好的一致性。由计算结果可知:在纳晶双峰材料中,纳晶基体能提供高强度,粗晶能有效提高材料延性;纳米裂纹的存在不会导致破坏,反而对应变硬化起积极作用。
The nanocrystal bimodal material composed of micron-sized coarse-grained particles and nano-sized nanocrystalline particles not only has high strength but also has high ductility. Based on Taylor’s strength theory and Johnson-Cook model, a new constitutive model of nanocrystal bimodal material was proposed. The effects of grain size and nanocrack on the constitutive and failure behavior of nanocrystalline bimodal material were investigated and numerically calculated . The results show that the results of model prediction are in good agreement with the experimental results. From the calculation results, we can see that in the nanocrystal bimodal material, the nanocrystalline matrix can provide high strength, the coarse grain can effectively improve the ductility of the material; the existence of the nanocracks does not lead to the destruction, but instead plays an active role in the strain hardening.