Radial inertia effect analysis of UHPC impact test based on SHPB
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摘要: 为探讨UHPC试件惯性效应对SHPB加载过程的影响，采用大型有限元分析软件LS-DYNA从试件直径、长径比以及恒应变率加载等角度出发，开展了相应的数值模拟与分析。通过对软件中Karagozian-Case-Concrete (KCC)损伤模型参数取值进行优化，建立了基于SHPB技术的UHPC材料冲击压缩数值模型并与试验验证。在此基础上，开展不同UHPC试件直径、长径比以及有无整形器下的参数分析，探讨其对SHPB试验中径向惯性效应的影响。结果表明：(1)为实现加载过程中一维应力传播和UHPC试件应力平衡，试件直径建议按0.90～0.95倍杆件直径取值；(2) UHPC试件长径比对试件加载过程中的应力平衡影响较小，但综合试件中钢纤维分布均匀性以及破坏前一维应力传播，建议按0.35～0.45取值；(3)实现恒应变率加载是UHPC材料在SHPB冲击试验中消除径向惯性效应的重要前提。Abstract: To discuss the radial inertia effect of UHPC impact test using SHPB, the numerical simulation and analysis using the software LS-DYNA are conducted by varying the specimen diameter, length-diameter ratio and constant strain rate loading. The dynamic damage behavior of UHPC material is fitted by optimizing the parameters of Karagozian-Case-Concrete (KCC) damage model in LS-DYNA. An impact model of UHPC is established and calibrated by SHPB experiments. The parameters of different UHPC specimens with or without pulse shaper were analyzed, and their effects on the radial inertia effect in SHPB test were discussed. The results show that: (1) to realize one-dimensional stress wave during the loading and stress equilibrium of specimen, the diameter of UHPC specimen is suggested to be 0.90−0.95 times the bar diameter; (2) the limited effect of aspect ratio of UHPC specimen on the stress equilibrium is observed, so the aspect ratio of UHPC specimen is suggested to be 0.35−0.45 for satisfying the uniformity of steel fiber distribution in fabrication and ensuring one-dimensional stress wave propagation; (3) the constant strain rate loading is an important prerequisite for eliminating the radial inertia effect of UHPC materials in SHPB impact test.
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图 2 KCC模型的剪切破坏面及单轴本构关系
Figure 2. Shear failure surfaces and uniaxial stress-strain relation in KCC model
图 3 UHPC本构关系拟合值与试验值对比
Figure 3. Comparison of constitutive relation of UHPCbetween fitted and experimental values
图 8 试件直径对径向惯性效应影响对比
Figure 8. Comparison of the influence of specimen diameters on inertia effect
图 9 试件长径比对惯性效应影响对比
Figure 9. Comparison of the influence of specimen aspect ratios on inertia effect
图 10 整形器设置对惯性效应影响对比
Figure 10. Comparison of the influence of pulse shaper on inertia effect
表 1 剪切破坏面确定参数
Table 1. Parameters for determining shear surface
a0y a1y a2y a0 a1 a2 a1f a2f 15.116 0.813 11 0.002 56 33.99 0.365 9 0.001 15 0.365 9 0.001 15 
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表 2 整形器材料参数
Table 2. Material parameters of pulse shapers
材料 密度/(kg·m−3) 剪切模量/GPa 屈服强度/MPa 塑性硬化模量/MPa 体积弹性模量/GPa 铝 2 700 26 276 354 67 铜 8 920 48 70 334 140
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表 3 杆件的特征参数
Table 3. Characteristic parameters of bars
部位 长度/mm 直径/mm 密度/(kg·m−3) 弹性模量/GPa 泊松比 撞击杆 305.0 25.4 9 150 200 0.3 入射杆 3 657.6 25.4 9 150 200 0.3 透射杆 3 657.6 25.4 9 150 200 0.3
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