外加应力作用下UO_(2)中空洞演化过程的相场模拟  

Phase-field simulation of void evolution in UO_(2) under applied stress

作　　者：姜彦博 柳文波[1] 孙志鹏 喇永孝 恽迪 Jiang Yan-Bo;Liu Wen-Bo;Sun Zhi-Peng;La Yong-Xiao;Yun Di(Institute of Nuclear Science and Technology,Xi’an Jiaotong University,Xi’an 710049,China;Science and Technology on Reactor System Design Technology Laboratory,Nuclear Power Institute of China,Chengdu 610213,China)

机构地区：[1]西安交通大学核科学与技术学院,西安710049 [2]中国核动力研究设计院核反应堆系统设计技术重点实验室,成都610213

出　　处：《物理学报》2022年第2期226-236,共11页Acta Physica Sinica

基　　金：国家自然科学基金委员会与中国工程物理研究院联合基金(NSAF联合基金)项目(批准号:U1830124,U2130105);中国核工业集团有限公司领创科研项目资助的课题。

摘　　要：本工作建立了外加应力作用下UO_(2)中空洞演化的相场模型.首先,使用摄动迭代法求解了弹性平衡方程,对外加应力下单个空洞周围的应力分布进行了计算,结果表明空洞边缘有应力集中现象,模拟得到的应力分布和解析解一致.然后,利用相场方法模拟了不同外加应力下单个空洞的演化过程,结果表明随着外加应力的增大,空洞的生长速度加快.最后,研究了外加应力对多晶体系中晶粒长大和空洞演化的影响,结果表明,不同晶粒内的应力大小不同,应力越小的晶粒越容易长大,尺寸越大的空洞的边缘应力也越大.晶间空洞与弯曲晶界存在相互作用,一方面晶界附近的空洞会生长成透镜状,另一方面空洞对晶界也有钉扎作用,能减缓晶界的迁移.此外,外加应力会加速多晶系统中空洞的生长,并且本文计算得到了外加应力与空洞半径的关系,发现外加应力越大,空洞的生长越快.Owing to the migration and aggregation of point defects produced by cascade collision,a large number of cavities form easily during irradiation of the uranium dioxide(UO_(2)) that is an important nuclear fuel.In addition,cavities are also inevitably introduced into the ceramic fuel during sintering.Moreover,the creep strain and thermal strain,caused by the extreme environment of high temperature and strong irradiation,significantly increase the applied stress of nuclear fuel.Therefore,it is crucial to investigate the microstructure evolution of the cavities in UO_(2) fuel under applied stress.In this work,a phase-field model of void evolution in UO_(2) under applied stress is established.Firstly,the elastic equilibrium equation is solved by the perturbationiterative method,and the stress distribution around a single void under applied stress is calculated.The results show that the stress concentration is observed at the edge of the void,and the simulated stress distribution is consistent with the theoretically analytical results.Then,the evolution processes of a single void under different applied stresses are simulated by the phase-field model.The results show that the growth rate of void increases with the augment of applied stress.Finally,the effect of applied stress on grain growth and void evolution in polycrystalline are also studied.The results show that the applied stress will accelerate the void growth.With the increase of the applied stress,the effect of the applied stress on accelerating the void evolution increases.

关 键 词：相场模拟 空洞演化 晶粒生长 外加应力 

分 类 号：TL27[核科学技术—核燃料循环与材料]