摘要
本文采用基于近场动力学框架的位错动力学叠加模型对FCC单晶在四种不同取向下的I型弹塑性开裂行为进行模拟研究.在模型中,无需预设裂纹扩展路径和内聚力区域,裂纹扩展路径由位错与裂纹的相互作用自动确定.数值计算了FCC单晶体在不同取向时的位错分布演化和裂纹扩展路径.分析表明取向会影响韧性和断裂行为,并证实了单晶体的单轴拉伸开裂行为遵循施密特因子关系,即位错更倾向于在施密特因子大的滑移面上形核并滑移.计算得到位错裂纹演化结果显示,不同取向时位错在滑移系上的分布和演化行为会导致不同晶体断裂模式.
Metallic single crystals,which are widely used in industrial devices due to their excellent properties,make the study on the mechanical behavior of metallic single crystals a necessary task.Dislocation evolution affects the plastic deformation and fracture of crystals,while the nucleation and evolution of dislocations are related to crystal orientation.Investigating the mechanism of the influence of crystal orientation on the elastoplastic cracking process,especially from the perspective of dislocation evolution and interaction between dislocations and cracks,is of great significance for solving the challenging problems of elastoplastic fracture and brittle-ductile transition in metallic crystalline materials.However,the framework of classical continuum mechanics has singularity problems when dealing with discontinuities such as cracks.In this paper,the Mode I elastoplastic fracture in a single crystal of four different orientations is investigated by using the superposition scheme for discrete dislocation dynamics(DDD)in the framework of peridynamics(PD).As a nonlocal alternative to the framework of classical continuum mechanics,PD models use spatial integration instead of spatial derivative,making it well-suited for problems where discontinuities may occur and develop.Moreover,PD models allow for integrating possible nonlocal effects induced by dislocations/microstructure/damage and their evolution.Therefore,the DDD-PD model can simulate elastoplastic fracture by considering the autonomous interactions between dislocations and crack growth.For obtaining the results,neither a preset cracking path nor a cohesive zone model is needed.The results show that the mechanical behavior of a single crystal under Mode I fracture exhibits evident orientation dependence,meaning that the change of orientation leads to differences in the crystal’s toughness,critical applied strain,and fracture behavior.The simulation reproduces the brittle-ductile transition be¬havior of the facture in single crystals,which is related to the nucleation and motion of the dislocations near the crack tip.The numerical elastoplastic deformation and facture results also capture the Schmid factor dependence.Dislocations tend to nucleate and glide on the slip planes with a larger Schmid factor.It shows that the distribution and evolution of dislocations on the slip system,affecting the crystal fracture pattern,vary with crystal orientation.
作者
董文博
陈子光
Wenbo Dong;Ziguang Chen(Department of Engineering Mechanics,School of Aerospace Engineering,Huazhong University of Science and Technology,Wuhan,430074;Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment,1037 Luoyu Road,Wuhan,430074)
出处
《固体力学学报》
CAS
CSCD
北大核心
2023年第5期565-577,共13页
Chinese Journal of Solid Mechanics
基金
国家自然科学基金青年项目(11802098)
中央高校基本科研业务费专项资金(2021GCRC021)资助
关键词
离散位错动力学
近场动力学
塑性
断裂
晶体取向
discrete dislocation dynamics
peridynamics
plasticity
fracture
crystal orientation
