基于XFEM模拟的核级石墨断裂行为研究

Study on fracture behaviors of nuclear graphite using XFEM simulation

为研究核级石墨的断裂性能,对单边切口的石墨梁进行三点弯曲试验,并采用扩展有限元(XFEM)对其断裂行为进行数值模拟。通过将数值模拟结果与试验得到的荷载-位移曲线进行对比,验证了数值模拟的可靠性。研究结果表明,加载过程中断裂过程区(FPZ)完全发展时,其长度lFPZ最大,约为14.16mm,约为石墨梁韧带高度的68%;分析了缝高比a0/D在起裂和失稳时石墨的断裂参数的变化,结果表明:随着a0/D的增大,起裂荷载Pini和峰值荷载Pc随着a0/D的增加而减小,Pini/Pc的比值保持稳定在0.8左右;双K断裂参数KIcini和KIcun基本保持不变;FPZ的长度lFPZ在完全发展之前呈线性增加,之后长度逐渐减小。

In order to study the fracture performance of nuclear graphite,three-point bending tests were performed on graphite beams with a single-edged notch,and the fracture behaviors of graphite beams are numerically simulated using extended finite element(XFEM).Numerical load-displacement curves obtained from the XFEM simulation are compared with the experimental results and good agreement is observed,the reliability of the numerical simulation is confirmed.Through numerical simulation, the length lFPZ of the fracture process zone(FPZ) of graphite during the loading process is obtained.When the FPZ is fully developed,the LFPZ reaches its maximum,which is about 14.16 mm and is about 68% of the ligament length.Variations of fracture parameters corresponding to fracture initiation and instability with a0/D are analyzed.The results indicate that with the increase of a0/D,the fracture initiation load Pini and the peak load Pc decrease with the increase of a0/D,and the ratio of Pini/Pc remains stable at about 0.8;KIcinc and KIcun remains basically unchanged;the length of FPZ lFPZincreases linearly before the FPZ is fully developed,and then gradually decreases in length.