The formation of fracture process zones in polygranular graphite as a precursor to fracture
The formation of fracture process zones in polygranular graphite as a precursor to fracture
复制标题
多粒石墨中断裂过程区的形成作为断裂的前兆
DOI：
--
复制
发表时间：
2012
影响因子：
4.5
通讯作者：
P. Flewitt
中科院分区：
文献类型：
--
作者：
S. Nakhodchi;D. Smith;P. Flewitt
研究了多颗粒堆芯A级堆芯慢化剂石墨在四点弯曲载荷作用下断裂过程区的形成和扩展。数字图像相关性与电阻应变计测量相结合，以评估石墨测试过程中的局部和全局应变。在平面和缺口矩形梁试件上进行的实验表明，在峰值载荷之前，荷载-位移特性是非线性的。这种行为被证明是主要由局部应变（或工艺区）的存在下延伸到约3毫米的试样的拉伸表面占主导地位。在峰值载荷下，宏观裂纹沿着不规则路径快速扩展，该路径由所施加载荷的方向和石墨的微观结构控制。这些裂纹在试样完全分离之前停止。一旦形成裂纹，局部拉伸位移在这些裂纹尖端之前延伸达约3 mm的距离。它还表明，失效载荷是不敏感的缺口的存在。结果进行了讨论相对于石墨的非线性负载-位移响应的峰值负载之前，在峰值负载后的宏观裂纹扩展过程中的作用的过程区。
The initiation and growth of fracture process zones are explored in polygranular Pile Grade A reactor core moderator graphite subjected to four-point bending. Digital image correlation is combined with resistance strain gauge measurements to evaluate both the localised and the global strains during tests on graphite. The experiments, performed on plain and notched rectangular beam specimens, show non-linear load–displacement characteristics prior to peak load. This behaviour is shown to be mainly dominated by the presence of localised strains (or process zones) extending up to about 3 mm from the tensile surface of the specimen. At peak load, a macrocrack propagates rapidly along an irregular path controlled by the direction of the applied load and the microstructure of the graphite. These cracks arrest prior to complete separation of the specimen. Once cracks are formed, localised tensile displacements extend for distances of up to about 3 mm ahead of the tips of these cracks. It is also demonstrated that failure load is not sensitive to the presence of the notch. The results are discussed with respect to the role of process zones on the non-linear load–displacement response of the graphite prior to the peak load and during macrocrack propagation post peak load.