核级石墨PFC^(2D)模型的宏细观参数分析

Macro-microparameters of nuclear graphite PFC^(2D)model

颗粒流软件PFC能够很好地处理非连续介质力学的问题,模拟核级石墨的损伤和断裂过程具有独特的优势。在采用PFC^(2D)模拟核级石墨时,为了增加模拟的便捷性,实现了PFC^(2D)细观参数的快速标定。本文首先设计了四因素四水平的正交试验,分析了核级石墨的宏观参数与PFC^(2D)的细观参数关系;然后基于建立的核级石墨宏细观参数的关系,采用PFC^(2D)模拟石墨IG11的三点弯曲试验,并从位移场变形、荷载-位移曲线和断裂参数三个方面验证其宏细观参数关系的正确性。结果表明,弹性模量E随平节理模量E_(c)的增加线性增加;抗拉强度σ_(t)随平节理抗拉强度σ_(b)的增加线性增加;泊松比ν随平节理刚度比k_(n)/k_(s)的增加先增大后减小;数值模拟的位移场变化和荷载-裂缝口张开位移P-CMOD曲线与试验结果较吻合,此外,断裂参数的最大误差不超过3.57%。

Particle Flow Code(PFC)can well deal with the problem of mechanics of non-continuous media,and has unique advantages in simulating the damage and fracture process of nuclear graphite.In order to increase the convenience of using PFC^(2D)to simulate nuclear graphite,the rapid calibration of PFC^(2D)micro-parameters can be achieved.Firstly,the orthogonal experiment with four factors and four levels is designed to analyze the relationship between the macro-parameters of nuclear graphite and the micro-parameters of PFC^(2D).Then,based on the established relationship between macro-microparameters of nuclear graphite,the three-point bending test of graphite IG11 is simulated by PFC^(2D),and the correctness of the relationship between macro-microparameters is verified from three aspects:displacement field deformation,load-displacement curve and fracture parameters.The results show that Young’s modulus(E)increases linearly with the increase of the effective modulus(E_(c)),the tensile strength(σ_(t))increases linearly with the increase of the bond tensile strength(σ_(b))of the flat joint,and Poisson’s ratio(ν)firstly increases and then decreases with the increase of the stiffness ratio(k_(n)/k_(s)).The numerical simulation results of displacement field variation and load-crack opening of displacement(P-CMOD)curve agree well with the test results.In addition,the maximum error of fracture parameters is not more than 3.57%.