Mechanism of expanding fracture of 45 steel cylinder shells driven by modified SHPB
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摘要: 采用改进型霍普金森压杆实验技术，对不同膨胀断裂状态的45号钢薄壁金属圆柱管进行了冻结回收，直接观测了薄壁金属圆柱管动态膨胀断裂过程中的裂纹萌生、扩展情况以及最终断裂模式等断裂演化特征。对冻结回收样品进行的金相显微分析完整观察到了裂纹萌生、扩展直至断裂的整个膨胀断裂过程，并得出以下结论：薄壁金属圆柱管在中应变率的膨胀断裂过程中，拉伸和剪切断裂机制起主导作用。裂纹萌生于外壁面，并由外向内扩展，断裂模式随加载应变率的提高逐渐由拉剪混合向纯剪切过渡。与爆轰加载的高应变率薄壁金属圆柱管断裂过程不同的是，随加载载荷的增加，薄壁金属圆柱管的断裂逐渐由拉伸断裂向剪切断裂过渡，而非绝热剪切断裂，这种差异的产生原因尚待研究。Abstract: Cylinder shells of 45 steel were freezing recovery experimented using a modified SHPB device to observe the whole fracture process, including crack initiation, crack propagation conditions and final fracture modes.By microanalysing the internal structures of the recovery samples, the whole fracture process was observed, and some conclusions were obtained:the tensile and shear fracture mechanism played a dominant role in the dynamic fracture process of cylinder shells, cracks initiated from the outer wall, then propagated into inner wall, the fracture mode changed from tensile-shear mixing to pure shear with increasing load strain rate.There were some differences between these experimental results and the results loaded by detonation, which need us to further study, that the fracture modes would change from tensile to pure shear in these experimental results, rather than adiabatic shear in detonations with increasing strain rate
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Key words:
- solid mechanics /
- mechanism of fracture /
- SHPB /
- metal cylinder shells /
- dynamic expanding fracture
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图 4 圆柱管裂纹起始位置与扩展形式
Figure 4. The propagation route and starting position of crack on cylinder shells
图 5 圆柱管在不同加载应变率下裂纹扩展形式与断口形貌
Figure 5. The route of crack propagation and fracture surface morphology of cylinder shells at different strain rates
表 1 圆柱管在不同加载应变率下的实验结果
Table 1. Experimental results of cylinder shells under different strain-rate
No. D/mm v/(m·s-1) σn/MPa εr t/μs $\dot{\varepsilon}_{r} / \mathrm{s}^{-1}$ 断裂状态 1 8.04 20 134 0.20 154 1.3×103 拉伸裂纹萌生 2 8.04 20 134 0.21 160 1.3×103 拉剪混合 3 8.04 20 134 0.21 160 1.3×103 拉剪混合 4 8.04 25 145 0.22 147 1.5×103 剪切裂纹萌生 5 8.04 25 145 0.23 150 1.5×103 纯剪切断裂 6 8.04 25 145 0.23 150 1.5×103 纯剪切断裂 
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