IG-11石墨材料断裂韧性数值模拟研究

Numerical Simulation of Fracture Toughness on Nuclear Graphite IG-11

通过使用基于内聚力模型（CZM ）的扩展有限元方法（XFEM ）对单边切口梁的三点弯曲试验进行数值模拟来研究核级石墨IG-11断裂韧性的尺寸效应，试验和分析中考虑了试样整体尺寸和厚度变化，并对数值分析中的材料断裂参数进行了敏感性研究。模拟所得断裂韧性范围为0.90～1.10 M Pa · m1/2，这与试验所测得的0.82～1.27 M Pa · m1/2接近。模拟结果表明，材料断裂功对数值分析的影响较小，而材料断裂时的抗拉强度对数值分析的影响较大；另外，核石墨的断裂韧性（KIC ）存在明显的尺寸效应，随模拟试样整体尺寸的增大，断裂韧性增大，最终趋于一定值。这与现有文献中的尺寸效应模型所得到的预测值以及试验结果吻合得较好。但试样厚度则对 KIC的变化无明显影响。

The study of size effect on the fracture toughness of nuclear grade graphite IG-11 by using extended finite element method （XFEM ） which is based on the cohesive zone model （CZM ） to simulate the fracture of single-edge-notched beams under three-point-bending was carried out .The influence of specimen size and thickness was studied both in the experiment and the simulation .Besides ,sensitivity analysis of the fracture parameters was under consideration in the numerical analysis . The predicted fracture toughness is in a range of 0.90-1.10 M Pa · m1/2 which is close to the experiment result of 0.82-1.27 M Pa · m1/2 .And the simulation results show that crack initiation strength has greater influence on the numerical analysis than the fracture energy of the material . In addition ,the fracture toughness of nuclear graphite shows a size effect ,i.e.the frac-ture toughness increases as the specimen size increases and finally converges to a con-stant value ,which agrees with the experiment and the prediction from recent size effect model as well .However ,the specimen thickness has no obvious effect on KIC .