管道钢微观变形失效机理的分子动力学研究  

The molecular dynamics simulation of pipe steel micro-deform failure

作　　者：韩悌信 曾祥国[1] 黄了 肖雨果 

机构地区：[1]四川大学建筑与环境学院,成都610065 [2]四川中科达石油天然气新技术有限公司,成都618300

出　　处：《四川大学学报（自然科学版）》2016年第4期865-874,共10页Journal of Sichuan University(Natural Science Edition)

基　　金：四川省应用基础研究计划项目"高压输气管线钢变形与失效的多尺度行为研究"(13JC0277);四川大学能源工程安全与灾害力学教育部重点实验室(金属基纳米陶瓷涂层界面结合性能的多尺度行为研究);四川大学"985"创新平台引进人才资助项目

摘　　要：本文通过Fe-Fe3C相图得到20#钢中铁素体(碳溶于α-Fe的间隙固溶体)和渗碳体(铁和碳形成的间隙化合物,即:Fe3C)的微观组织结构,利用Material Studio软件建立α-Fe/Fe3C原子尺度的微观模型.利用Lammps软件对主裂纹附近存在微裂纹和微孔洞两种典型缺陷的20#钢模型进行了分子动力学模拟.在正则系综(NVT)条件下,研究了微观裂纹和孔洞对材料力学性能的影响.研究结果显示,裂纹的扩展是原子间化学键断裂、裂纹尖端不断发射位错导致的;当裂纹到达α-Fe/Fe3C的界面后便止裂,裂尖逐渐钝化,裂纹尖端不断向渗碳体(Fe3C)发射位错,渗碳体(Fe3C)中的原子失去了原来的排列特征,局部留下了难以恢复的空位,偏向于裂尖钝化和沿滑移面剪切断裂机制.本文提供的研究方法和结论对揭示20#钢的微观变形与失效机理具有重要的参考价值.为进一步研究腐蚀条件下20#钢的失效机理打下了基础.In this paper, micro structure of ferrite （α-Fe） and cementiti（Fe3C） in 20 # Steel are obtained through Fe-FeaC phase graph. Using Material Studio software, α-Fe/Fe3 C atomic-scale micro model can be built. Lammps software is used in molecular dynamics simulation of 20 # steel model with two typical defects near the main crack. Under the conditions of canonical ensemble（VBT）, the effects of micro- cracks and holes on the mechanical properties of the material is studied. The results showed that crack propagation is the result of chemical bonds breakage between atoms and constantly dislocation emission at crack tip. When the crack reaches the surface of α-Fe/Fe3C and stop extension. Crack tip is gradually passivated and constantly launch dislocation towards cementiti （Fe3C）. Then the atoms in cementiti （FeaC） lost its original arrangement features, and leave the local vacancy which is difficult to recover, and more likely to occur crack tip passivation and shear fracture mechanism along slip plane. Research methods and conclusions provided by this paper have important reference value to discover micro deform and failure mechanism of 20# steel. And provide foundation for further study of 20 # steel failure mechanism under corrosive conditions.

关 键 词：分子动力学 20#钢 微裂纹 位错发射 裂间钝化 

分 类 号：O346.1[理学—固体力学]