不同裂纹扩展阶段对SCC裂尖蠕变场的影响

Influence of different crack propagation stages on SCC crack tip creep field

裂尖区域蠕变是核电材料应力腐蚀裂纹扩展的主要驱动因素之一,为研究不同裂纹扩展阶段下SCC裂尖蠕变场的变化规律,采用紧凑拉伸试样建立了SCC裂尖蠕变的有限元模型,以核电常用的奥氏体304不锈钢为研究对象,分析裂尖蠕变以及蠕变对裂尖力学场的影响,同时以裂纹长度的变化表征裂纹扩展的不同阶段,进而研究了不同裂纹扩展阶段下对裂尖蠕变及蠕变率的影响规律,通过ABAQUS数值模拟分析软件计算可得,高蠕变量区域主要集中分布在近裂尖区域,裂纹长度对SCC裂尖蠕变场的影响较大,随着奥氏体304不锈钢裂纹长度的不断增加,裂尖蠕变量以及蠕变率也在不断增加。随着蠕变的推进,到达稳态蠕变阶段时蠕变率均趋向于同一水平,且随时间的继续增加,蠕变率变化不大,同时裂纹扩展速率随着裂纹长度呈现出指数的增加规律,在应力腐蚀开裂初始阶段,裂纹扩展速率较慢,随着裂纹长度的增加,扩展速率越来越快。为进一步研究基于蠕变致SCC开裂的结构安全性评价提供一定的理论参考。

Creep is one of the main driving factors that causes environmental assisted cracking at crack tip in nuclear material.To examine the creep field around SCC crack tip under different crack growth stages,a finite element model of SCC crack tip creep was established using CT specimens.The influence of creep at crack tip and creep on the mechanical field at crack tip was studied using 304 austenitic stainless steel in nuclear power plants.The different stages of crack growth are characterized by the change of crack length.Results show that the high creep zone distributes mainly near the crack tip by ABAQUS numerical simulation analysis software.Crack length has a great influence on the creep field of SCC crack tip.With the increasing of the crack length of austenitic 304 stainless steel,the creep rate and the creep rate at the crack tip are also increasing.With the advancing of creep to reach the steady-state creep stage,the creep rate tends to be the same level,and as the time continues to increase,the creep rate does not change much,with the crack growth rate increased exponentially as the crack is expanding.In the initial stage of stress corrosion cracking,the crack growth rate is slower.As the length of the crack increases,the growth rate becomes faster and faster.This provides a theoretical reference for further research on structural safety assessment of SCC cracking based on creep.