Simulation of dynamic compression of plastic-bonded explosives considering heterogeneous structure
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摘要: 采用离散元方法，构建了考虑PBX炸药晶体颗粒与黏结剂非均匀性的计算模型，通过在炸药试样两端采用相向飞片加载、将原SHPB实验的应力边界替代为速度边界的方法，开展了PBX炸药的动态压缩数值模拟研究，再现了考虑PBX炸药非均质特性的SHPB实验过程，获得了不同加-卸载路径下炸药应力应变曲线以及相应的损伤破坏图像。模拟结果表明：在动态压缩过程中，虽然PBX炸药处于整体应力平衡，由于PBX高度非均质性，内部应力分布并不均匀，晶体间应力以应力桥形式传递；应力曲线为试样整体平均，试样内局部所受真实应力可能高于曲线峰值应力；出现卸载回滞曲线的试样发生局部损伤破坏，而完全软化曲线的试样发生整体失稳破坏。Abstract: The plastic-bonded explosives (PBX) simulation model with heterogeneous crystal grain and binder was presented using the discrete element method(DEM). By loading opposite flyers at both ends of the explosive sample, the dynamic compression simulation was performed adopting velocity as the boundary condition instead of stress as the boundary condition in the Hopkinson test, and replicated the compression process in the Hopkinson test. The stress-strain curves and their corresponding damage fracture images under different loading-unloading paths in the explosive sample were captured. Our simulation results indicated that the stress distribution in PBX is not uniform and the stress propagates in the form of stress bridges between crystals due to the heterogeneous structure. The actual stress in PBX can be higher than that shown by the curve's peak stress. The samples on the unloading hysteresis curves reveal local damage, while those on the completely softening curves indicate fractures resulting from integral instability.
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图 4 弹性阶段初期的应力分布与细观结构
Figure 4. Stress distribution and meso-structure at early elastic stage
图 6 弹性阶段后期的应力分布与细观结构
Figure 6. Stress distribution and meso-structure at later elastic stage
图 8 强化阶段的应力分布与细观结构
Figure 8. Stress distribution and meso-structure at hardening stage
图 10 应变软化阶段初期的应力分布与细观结构
Figure 10. Stress distribution and meso-structure at early strain softening stage
图 12 应变软化阶段后期的应力分布与细观结构
Figure 12. Stress distribution and meso-structure at later strain softening stage
表 1 材料参数
Table 1. Material parameters
材料 ρ/
(g·cm-3)c0/
(km·s-1)λ aij/GPa m n μij G/
GPaCn/
(Pa·s)εy εb HMX 1.9 2.9 2.06 1.85 1.0 3.0 0.1 10.74 11 0.02 0.005 黏结剂 1.1 2.3 1.70 7.80 1.0 2.0 0.1 6.80 11 0.10 0.020 
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