基于分子动力学研究纳米孔洞对多晶FeO/Fe中FeO断裂的影响

Study on the effect of nano-pores on FeO fracture in polycrystalline FeO/Fe based on molecular dynamics

孔洞缺陷是影响表面氧化皮断裂失效的重要因素.本文结合分子动力学软件Lammps和Atomsk软件建立了半径相同位置不同(模型1)和孔洞位置相同半径不同(模型2)两种模型,为了探究两者对FeO/Fe多晶模型拉伸失效的影响,文章从抗拉强度、断裂韧性、中心对称参数(CSP)三方面进行了分析,模拟结果表明:1.当孔洞位于晶界和三叉点时,模型1和2的抗拉强度随着孔洞半径的增大而减小,断裂韧性在抗拉强度降低的同时增强.2.孔洞位于晶内时,模型2的抗拉强度呈现“先下降-后上升-再下降”的变化趋势,断裂韧性整体降低;模型1既增强了模型的抗拉强度,又降低了断裂韧性.3.裂纹扩展受孔洞半径影响较大,半径达到1 nm以上时,模型2的裂纹扩展速度加快,模型1的裂纹扩展速度减慢.本研究为进一步认识氧化皮的断裂过程提供了帮助.

The pore defect is an important factor affecting the fracture failure of surface oxide skin.In this paper,two models,one with the same radius and different positions(Model 1)and the other with the same pore position and different radii(Model 2),were established by combining molecular dynamics software Lammps and Atomsk.In order to explore the influence of the two models on the tensile failure of FeO/Fe polycrystalline model,In this paper,the tensile strength,fracture toughness and center symmetry parameter(CSP)are analyzed.The simulation results show that:1.When the pores are located at grain boundaries and trigeminal points,the tensile strengths of Model 1 and Model 2 decrease with the increase of the pore radius,and the fracture toughness decreases with the increase of the tensile strength.2.The fracture toughness of Model 2 is enhanced when the pore is located in the grain.When the radius is 1 nm,the tensile strength of Model 2 is increased,but the fracture toughness is decreased.In Model 1,not only the tensile strength of the material is enhanced,but also the fracture toughness is reduced.3.The crack propagation is greatly affected by the pore radius.When the radius reaches more than 1nm,the crack propagation speed of Model 2 accelerates,while that of Model 1 slows down.This study is helpful for further understanding the fracture process of oxide skin.