Damage effect on the fracture toughness of nodular cast iron: Part-II. Damage zone characterization ahead of a crack tip
Damage effect on the fracture toughness of nodular cast iron: Part-II. Damage zone characterization ahead of a crack tip
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球墨铸铁断裂韧性的损伤效应：第二部分。
DOI：
10.1007/s11661-997-0183-6
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
D. François
中科院分区：
文献类型：
--
作者：
M. Dong;C. Prioul;D. François
为了了解球墨铸铁的断裂韧性，通过对CT 25试样在延性撕裂前后抛光表面的扫描电镜（SEM）观察，研究了球墨铸铁的损伤区。损伤被定义为石墨/基体界面处的脱粘。结果表明，球墨铸铁的损伤区很大（几乎遍及裂纹尖端前的整个韧带），因此线弹性断裂力学（LEFM）对小试样不适用。损伤区的大小进行了计算分析，通过引入一个损伤引发标准，这是基于观察基体和石墨球之间的界面的脱粘和铸铁的压力敏感性的测量。考虑到实际的边界条件，也计算了损伤区的数值模拟使用的修正Gurson的模型，并考虑球墨铸铁作为一种多孔材料。计算结果与损伤区观测结果吻合较好。平面应力和平面应变计算产生了几乎相同大小的塑性区。这一结果与完全致密材料的结果相反。
In order to understand the fracture toughness of nodular cast iron, the damage zone was studied by Scanning Electron Microscope (SEM) observations of the polished surface of a CT 25 specimen before and after ductile tearing. Damage is defined as decohesion at the graphite/matrix interface. It is shown that the damage zone is very large in nodular cast iron (almost throughout the whole remaining ligament ahead of the crack tip), so linear elastic fracture mechanics (LEFM) are not valid for small specimens. The size of the damage zone was calculated analytically by introducing a damage initiation criterion which was based both on observations of the debonding of the interface between matrix and graphite nodules and on measurements of the pressure sensitivity of cast iron. To take into account the actual boundary conditions, the damage zone was also calculated by numerical modeling using the modified Gurson’s model and by considering the nodular cast iron as a porous material. The calculated results led to good agreement with the damage zone observations. Plane stress and plane strain calculations yielded nearly the same size plastic zone. This result is opposite to those obtained for fully dense materials.