In this work, based on the traction-separation (T-S) constitutive relations extracted from molecular dynamics (MD) simulation, a peridynamics (PD) model is proposed to investigate the crack propagation behavior of the polycrystal BBC-Fe under mode I loading condition. MD simulation is carried out to give an insight into the cracking process and fracture mechanism according to the analysis of atomic configuration and stress distribution. The atomic stress at the crack tip with respect to the opening distance is tracked during the steady cracking stage to provide a stable T-S relation. The fracture parameters of single crystal Fe are obtained via MD simulation, based on which the PD parameters are obtained through an energy equivalent method. After that, a PD approach combined with cohesive zone model (CZM) is proposed to study the mode I fracture in polycrystal Fe. A good agreement has been found between the proposed PD model and the classical CZM based on a quasi-static splitting test of a single Fe crystal. Subsequently, PD simulations are performed concerning the dynamic crack propagation in a polycrystal Fe. What’s more, the effect of grain size, the grain boundary strength and the horizon size of PD on the fracture characteristics are examined. It can be concluded that the T-S relation originated from classical cohesive theory can be regarded as an effective bridge between MD and PD. This work provides a new thought to study the fracture behavior of polycrystals from the atomic deformation mechanism to micro-fracture description.

在这项工作中，基于从分子动力学（MD）模拟中提取的牵引分离（TS）本构关系，提出了一种绕动力学（PD）模型，以研究I型加载条件下多晶BBC-Fe的裂纹扩展行为。通过对原子构型和应力分布的分析，进行了MD模拟，以深入了解开裂过程和断裂机理。在稳定的开裂阶段，跟踪裂纹尖端相对于张开距离的原子应力，以提供稳定的TS关系。通过MD模拟获得单晶Fe的断裂参数，在此基础上通过能量当量法获得PD参数。之后，提出了一种PD方法与内聚区模型（CZM）相结合的方法来研究多晶铁的I型断裂。基于单个Fe晶体的准静态分裂测试，在建议的PD模型和经典CZM之间已经找到了很好的协议。随后，进行关于多晶铁中动态裂纹扩展的PD模拟。此外，研究了PD的晶粒尺寸，晶界强度和水平尺寸对断裂特性的影响。可以得出结论，源自经典内聚理论的TS关系可以看作是MD与PD之间的有效桥梁。这项工作为研究多晶的断裂行为提供了新的思路，从原子变形机理到微观断裂描述。基于单个Fe晶体的准静态分裂测试，在建议的PD模型和经典CZM之间已经找到了很好的协议。随后，进行关于多晶铁中动态裂纹扩展的PD模拟。此外，研究了PD的晶粒尺寸，晶界强度和水平尺寸对断裂特性的影响。可以得出结论，源自经典内聚理论的TS关系可以看作是MD与PD之间的有效桥梁。这项工作为研究多晶的断裂行为提供了新的思路，从原子变形机理到微观断裂描述。基于单个Fe晶体的准静态分裂测试，在建议的PD模型和经典CZM之间已经找到了很好的协议。随后，进行关于多晶铁中动态裂纹扩展的PD模拟。此外，研究了PD的晶粒尺寸，晶界强度和水平尺寸对断裂特性的影响。可以得出结论，源自经典内聚理论的TS关系可以看作是MD与PD之间的有效桥梁。这项工作为研究多晶的断裂行为提供了新的思路，从原子变形机理到微观断裂描述。进行有关多晶Fe中动态裂纹扩展的PD模拟。此外，研究了PD的晶粒尺寸，晶界强度和水平尺寸对断裂特性的影响。可以得出结论，源自经典内聚理论的TS关系可以看作是MD与PD之间的有效桥梁。这项工作为研究多晶的断裂行为提供了新的思路，从原子变形机理到微观断裂描述。进行有关多晶Fe中动态裂纹扩展的PD模拟。此外，研究了PD的晶粒尺寸，晶界强度和水平尺寸对断裂特性的影响。可以得出结论，源自经典内聚理论的TS关系可以看作是MD与PD之间的有效桥梁。这项工作为研究多晶的断裂行为提供了新的思路，从原子变形机理到微观断裂描述。