Dynamic fracture toughness of high strength metals under impact loading: increase or decrease
Dynamic fracture toughness of high strength metals under impact loading: increase or decrease
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DOI：
10.1007/s10409-011-0440-1
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发表时间：
2011-06
影响因子：
3.5
通讯作者：
Zejian Xu;Yu-long Li
中科院分区：
文献类型：
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作者：
Zejian Xu;Yu-long Li
在以往的动态断裂研究中发现了一个难以捉摸的现象，即高强度金属的动态断裂韧性（DFT）总是随着加载速率的增加而增加，其量级为TPa·m1/2·s−1。为了验证这一点，本文研究了航空工业中常用的两种高强度钢30CrMnSiA和40Cr的DFT随加载速率的变化。在改进的分离式霍普金森压杆（SHPB）实验装置上，30CrMnSiA和40Cr的冲击速度分别为9.2 ~ 24.1 m/s和16.3 m/s，实验结果进行了比较。结果表明，对于30CrMn-SiA，裂纹尖端加载率随冲击速度的增加而增加，而断裂起裂时间和DFT同时减小。然而，在40Cr的测试中，DFT也有增加的趋势，与其他报告相似。通过对动应力强度因子（DSIF）与加载率之间关系的深入研究，得出了以往研究中普遍存在的增大趋势可能是错误的，这是由有限的冲击速度域以及实验和数值过程中存在的误差引起的。为了揭示DFT对加载速率的真正依赖关系，需要在较大的冲击速度范围内进行实验。
An elusive phenomenon is observed in previous investigations on dynamic fracture that the dynamic fracture toughness (DFT) of high strength metals always increases with the loading rate on the order of TPa·m1/2·s−1. For the purpose of verification, variation of DFT with the loading rate for two high strength steels commonly used in the aviation industry, 30CrMnSiA and 40Cr, is studied in this work. Results of the experiments are compared, which were conducted on the modified split Hopkinson pressure bar (SHPB) apparatus, with striker velocities ranging from 9.2 to 24.1 m/s and a constant value of 16.3 m/s for 30CrMnSiA and 40Cr, respectively. It is observed that for 30CrMn-SiA, the crack tip loading rate increases with the increase of the striker velocity, while the fracture initiation time and the DFT simultaneously decrease. However, in the tests of 40Cr, there is also an increasing tendency of DFT, similar to other reports. Through an in-depth investigation on the relationship between the dynamic stress intensity factor (DSIF) and the loading rate, it is concluded that the generally increasing tendency in previous studies could be false, which is induced from a limited striker velocity domain and the errors existing in the experimental and numerical processes. To disclose the real dependency of DFT on the loading rate, experiments need to be performed in a comparatively large striker velocity range.