基于SHPB的UHPC冲击试验径向惯性效应分析

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。

Radial inertia effect analysis of UHPC impact test based on SHPB

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.