Caustics experimental study on the interaction between moving cracks and voids under impact loading
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摘要: 为了研究含有圆形缺陷的半圆盘试件在不同冲击速度下的断裂特征，采用霍普金森杆加载系统和动态焦散线试验系统，对半圆盘试件进行了试验研究。结果表明：裂纹起裂前，焦散斑半径出现跳跃情况，是入射杆的反复加载造成的；随着冲击速度的增加，裂纹穿过圆形缺陷的应力强度因子峰值有所增加，裂纹穿过圆形缺陷的扩展速度也增加明显；随着圆形缺陷半径的增大，裂纹在圆形缺陷处发生二次起裂时的应力强度因子变大。Abstract: In order to study the fracture characteristics of semi-disc specimens with circular defects under different impact speeds, Hopkinson rod is used to dynamically load the semi-disc specimen, and the fracture process of the semi-disc specimen is observed by the dynamic caustics test system, Through the combination of the two test systems, the fracture characteristics of the semi-disc specimens are studied, the research results show that: before the crack initiation, the focal speckle radius jumps, which is caused by the repeated loading of the incident rod. With the increase of the impact velocity, the peak stress intensity factor of the crack passing through the circular defect increases, and the propagation speed of the crack passing through the circular defect also increases significantly, which shows that the impact velocity contributes to the crack propagation. With the increase of the radius of the circular defect, the stress intensity factor of the second crack initiation at the circular defect becomes larger.
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Key words:
- semicircular disk /
- caustics /
- crack growth rate /
- stress intensity factor /
- SHPB
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图 3 半圆盘弯曲试验示意图
R—试件半径;d—厚度;a—裂纹长度; S—2个支撑点的距离;r—缺陷半径
Figure 3. Schematic diagram of semi-disc bending test
图 4 运动裂纹与空孔相互作用动态焦散图
Figure 4. Dynamic caustics diagram of the interaction between moving cracks and voids
图 5 缺陷半径1 mm时裂纹二次起裂的速度随时间变化曲线
Figure 5. When the defect radius is 1 mm, the speed of the second crack initiation varies with time
图 6 缺陷半径1 mm时裂纹二次起裂的应力强度因子随时间变化关系曲线
Figure 6. When the defect radius is 1 mm, the intensity factor changes with time when the crack initiates a second time
图 7 不同入射速度及不同孔径下裂纹二次起裂时的KⅠd值
Figure 7. The KⅠd value of the second crack initiation under different incident speeds and different apertures
表 1 有机玻璃力学参数
Table 1. Mechanical parameters of plexiglass
参数 密度ρ/
(kg·m-3)动态弹性
模量Ed/GPa泊松比vd 纵波波速
CP/(m·s-1)横波波速
CS/(m·s-1)剪切模量
G/GPa数值 1 180 6.1 0.31 2 320 1 260 1.28 
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表 2 不同入射速度及不同孔径下裂纹二次起裂时KⅠd
Table 2. Statistical table of KⅠd for the second crack initiation under different incident speeds and different apertures
缺陷半径r/mm 二次起裂KⅠd/(MPa·m1/2) v1=2.7 m/s v2=2.3 m/s v3=2.2 m/s v4=2.0 m/s v5=1.5 m/s 1.0 2.10 1.80 1.75 1.69 1.60 1.5 2.30 2.20 1.90 1.80 1.70 2.0 2.70 2.50 2.30 2.10 1.80 2.5 3.60 3.20 2.90 2.60 2.30 3.0 3.80 3.30 3.24 3.10 2.90
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