Experimental Studies on Energy Release Rate and Bifurcation Process of Fast Propagating Cracks

快速扩展裂纹能量释放速率及分叉过程的实验研究

基本信息

批准号：
12650082
负责人：
SUZUKI Shinichi
金额：
$ 2.43万
依托单位：
Toyohashi University of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12650082/
关键词：
Fracture mechanics Impact strength Experimental stress analysis Brittle fracture Fracture toughness High-polymer materials Crack opening displacement Crack propagation き裂分岐光計測

项目摘要

Two kinds of experimental studies were carried out to figure our the bifurcation mechanism of fast propagating cracks.[1] Fast Propagating cracks at bifurcation were photographed with high-speed holographic microscopy. Crack speed was more than 650m/s. The photographing was done within 10μs before and after bifurcation, and the following results were obtained.(1) Crack opening displacements, CODs, are proportional to the distance r from the crack tip before bifurcation. After bifurcation CODs of mother cracks are proportional to r from the nominal tip of the mother cracks.(2) The energy release rate obtained from the CODs increases gradually and continuously across the bifurcation points of the cracks. Discontinuous change of the energy release rate doesn't occur at the bifurcation.(3) The energy flux toward the crack tips also increases gradually and continuously at the moment of crack bifurcation, and doesn't show discontinuous change. This is caused by the fact that the crack dosen't decelerate discontinuously after crack bifurcation.[2] Two optical systems were applied to take photographs of rapidly bifurcating cracks on the both surfaces of the plate specimens, and the following results were obtained.(1) There are some bifurcating cracks whose shape on one surface of a specimen is apparently different from that on the other surface. In these cases, the crack bifurcations are not two dimensional phenomena, but three dimensional ones.(2) In the above cases, some crack branches keep developing and break up the specimens.(3) Even in the case that cracks have similar shape on the both surface of specimens, two crack branches have different opening displacement. This means that bifurcation is not symmetric with respect to the line along the mother crack.[3] The continuous increase of energy release rate across the bifurcation point may be caused by the three dimensional nature of crack bifurcation.

进行了两种实验研究，以了解我们快速传播裂纹的分叉机理。[1]用高速全息显微镜拍摄分叉时的快速传播裂纹。裂纹速度超过650m/s。摄影是在分叉前后在10μs内完成的，并获得了以下结果。（1）开口位移，COD，与分叉前距离裂纹尖端的距离成正比。母裂纹的分叉化鳕鱼与母裂纹的标称尖端成正比。（2）从CODS获得的能量释放速率在裂纹的整个分叉点上逐渐和连续地增加。在分叉时不会发生不连续的能量释放速率。（3）裂纹尖端的能量通量在裂纹分叉时也逐渐增加，并且不会显示不连续的变化。这是由于裂缝分叉后不连续减速的事实引起的。[2]使用两个光学系统来拍摄板样品两个表面上快速分叉裂纹的照片，并获得以下结果。（1）有一些分叉的裂纹，其在样品的一个表面上的形状显然与另一表面上的形状不同。在这些情况下，裂纹分叉不是二维现象，而是三维现象。（2）在上述情况下，某些裂纹分支不断发育和打破样品。（3）即使在两个样品表面上裂纹的形状相似的情况下，两个裂纹分支也具有不同的开放位移。这意味着分叉相对于沿母亲裂缝的线并不对称。[3]整个分叉点的能量释放速率的连续增加可能是由裂纹分叉的三维性质引起的。