A study of parameters of Kong-Fang fluid elastoplastic damage material model for Shandong granite
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摘要: 岩石类材料的动态力学模型的建立及相应模型参数的确定,对岩石动态力学性能研究及相关仿真计算具有重要意义。以山东五莲地区花岗岩为例,基于Kong-Fang流体弹塑性损伤材料模型(KF模型),通过准静态单轴压缩、劈裂、常规三轴实验及动态分离式霍普金森杆压缩(split Hopkinson pressure bar,SHPB)实验对模型中的强度参数进行了确定,并利用基于分离式霍普金森杆的巴西圆盘(split Hopkinson pressure bar-Brazilian disk,SHPB-BD)实验对应变率相关参数的有效性进行了验证;同时,根据平板撞击实验结果对模型中的状态方程参数进行了拟合。利用实验获得的材料参数值,采用KF模型对花岗岩侵彻实验进行数值模拟,计算得到的弹体侵彻深度及成坑尺寸与实际实验结果误差均小于15%,验证了材料模型及参数值的适用性。
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关键词:
- Kong-Fang模型 /
- 准静态实验 /
- 动态实验 /
- 平板撞击 /
- 侵彻实验
Abstract: The establishment of the dynamic mechanical model of rock materials and the determination of the relevant model parameters are of great significance to the studies of rock’s dynamic mechanical properties and related simulation calculation. Taking granite in Shandong Province as the experimental object, based on the Kong-Fang fluid elastic-plastic damage material model (KF model), the model parameters are classified into three categories, and the test scheme is then correspondingly determined. The basic strength parameters of the KF model were measured by quasi-static uniaxial compression and unconfined splitting tests. The strength-surface related material parameters were fitted by the results of the conventional triaxial tests under five different confining pressure conditions. In addition, the dynamic split Hopkinson pressure bar (SHPB) tests under several strain rate conditions were carried out to determine the strain-rate related parameters, of which the effectiveness were then verified by the dynamic split Hopkinson pressure bar-Brazilian disk (SHPB-BD) tests results. According to the principle of reverse impact and the Rankine-Hugoniot equation, the plate impact experiments with different impact stress levels were conducted by using a single-stage light gas gun, the state equation parameters in the KF model were fitted according to the impact Hugoniot results of rock samples. To verify the applicability of the material model and the experimentally measured parameter values, the simulation of a penetration process is furtherly conducted. The granite penetration tests were carried out by using a$\varnothing $ 30 mm caliber gun. The$\varnothing $ 20 mm bullets penetrated the$\varnothing $ 1200 mm×800 mm rock targets vertically, which was used to characterize the semi-infinite thickness condition, at an approximately designed speed of 670 m/s. To avoid accidental errors, combined with the high-speed photographic images, three effective penetrate results were obtained. The penetration depth and crater size of the target failure surface were directly measured and scanned by 3D scanner, the experimental average penetration depth, maximum and minimum diameters of the penetration craters were approximately 80.62 mm, 381.47 mm and 263.01 mm, respectively. Using the parameter values obtained from the laboratory experiments, the KF model is then implemented into LS-DYNA through a user-defined material model and used to simulate the penetration test of granite. According to the simulation result of damage distribution and cratering parameters of the target, the calculated penetration depth, maximum and minimum diameters of craters are 80.02 mm, 400 mm and 300 mm, respectively, so the errors between the calculated and the test results are less than 15%, which is acceptable in dynamic problems. The agreement between the numerical and experimental results provides a support to the application of the KF model and the relevant parameter values.-
Key words:
- Kong-Fang model /
- quasi-static experiment /
- dynamic experiment /
- plate impact /
- penetration experiment
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表 1 KF模型参数的分类及实验确定方法
Table 1. Parameter classification and experimental determination method of KF model
分类 参数 物理意义 确定方法 材料基本强度参数 ft 劈裂拉伸强度 准静态劈裂实验 fc 单轴压缩强度 准静态单轴压缩实验 E 弹性模量 υ 泊松比 强度面相关参数 a1、a2 强度面相关材料常数 准静态常规三轴实验 α、β、θ 应变率相关材料参数 SHPB/ SHPB-BD实验 状态方程相关参数 k1、k2、k3 状态方程参数 平板撞击实验 表 2 花岗岩的基本强度参数值
Table 2. Basic strength parameters of granite
试件 fc /MPa E/GPa υ 试件 ft /MPa UCT-1 125.088 38.076 0.310 ST-1 7.714 UCT-2 133.206 41.82 0.352 ST-2 6.9 UCT-3 128.969 38.843 0.318 ST-3 8.12 UCT-4 133.802 39.534 0.498 ST-4 6.887 UCT-5 133.772 40.759 0.259 ST-5 7.409 KF模型参数值 130.967±3.856 39.806±1.497 0.347±0.091 KF模型参数值 7.406±0.532 表 3 不同围压条件下试件的轴向峰值强度、偏压力与静水压力
Table 3. The strength, deviatoric pressure and hydrostatic pressure of rock samples under different confining pressures
试件 围压/MPa 轴向峰值强度/MPa 静水压力/MPa 偏应力/MPa 10-1 10 256.220 92.073 246.220 20-1 20 327.341 122.447 307.341 30-1 30 385.384 148.461 355.384 30-2 393.095 151.032 363.095 30-3 390.809 150.270 360.809 40-1 40 437.691 172.564 397.691 40-2 440.422 173.474 400.422 40-3 444.189 174.730 404.189 50-1 50 482.936 194.312 432.936 50-2 485.975 195.325 435.975 50-3 495.950 198.650 445.950 表 4 SHPB、SHPB-BD实验的平均应变率及相应的
$\eta_{\rm c} $ 、$\eta_{\rm t} $ 值Table 4. Average strain rates and corresponding
$\eta_{\rm c} $ and$\eta_{\rm t} $ values obtained from SHPB and SHPB-BD experiments试件 动态压缩强度/MPa ηc 平均应变率/s−1 试件 动态劈裂拉伸强度/MPa ηt 平均应变率/s−1 SHPB-1 159.324 1.217 83 SHPB-BD-1 41.395 5.589 138 SHPB-2 142.925 1.091 105 SHPB-BD-2 37.363 5.045 135 SHPB-3 160.994 1.229 102 SHPB-BD-3 45.456 6.138 133 SHPB-4 156.455 1.195 85 SHPB-BD-4 45.548 6.150 135 SHPB-5 164.434 1.256 122 SHPB-BD-5 52.404 7.076 187 SHPB-6 180.403 1.377 144 SHPB-BD-6 52.654 7.110 183 SHPB-7 145.891 1.114 168 SHPB-BD-7 49.934 6.742 187 SHPB-8 140.933 1.076 187 SHPB-BD-8 49.225 6.647 188 SHPB-9 212.790 1.625 230 SHPB-BD-9 65.320 8.820 241 SHPB-10 260.696 1.991 325 SHPB-BD-10 54.190 7.317 245 SHPB-11 158.481 1.210 258 SHPB-BD-11 70.300 9.492 239 SHPB-12 177.977 1.359 292 SHPB-BD-12 60.436 8.160 243 SHPB-13 215.694 1.647 360 SHPB-BD-13 48.513 6.550 155 SHPB-BD-14 61.372 8.287 199 SHPB-BD-15 71.112 9.602 210 表 5 花岗岩平板撞击实验结果
Table 5. Plate impact test results of granite samples
实验 w/ (m∙s−1) up,Cu (m∙s−1) up,rock /(m∙s−1) prock /GPa us,rock/ (m∙s−1) μrock G-1 298.249 170.887 212.806 3.103 5430.281 0.039 G-2 298.586 171.614 212.779 3.117 5454.783 0.039 G-3 296.200 175.154 208.623 3.183 5681.906 0.037 G-4 364.353 210.768 258.969 3.856 5543.886 0.047 G-5 362.860 210.444 257.638 3.849 5563.631 0.046 G-6 370.399 217.718 261.540 3.988 5677.582 0.046 G-7 420.639 247.273 297.002 4.553 5708.849 0.052 G-8 425.834 247.173 302.248 4.552 5607.388 0.054 G-9 424.120 246.701 300.769 4.542 5623.706 0.053 G-10 536.010 308.458 381.771 5.743 5601.403 0.068 G-11 527.022 302.785 375.608 5.632 5582.955 0.067 G-12 536.027 312.243 370.879 5.817 5840.622 0.063 表 6 花岗岩KF模型参数拟合结果
Table 6. Fitting results of KF model parameters of granite
强度参数 状态方程参数 fc/MPa ft/MPa E/GPa a1 a2/MPa −1 υ α β θ k1/GPa k2/GPa k3/GPa 130.967 7.406 39.806 0.36 0.09/fc 0.347 0.06 3.47 1.83 45.002 1413.751 −12037.857 基本力学指标 JC本构模型参数 密度/
(kg∙m−3)洛氏硬度
HRC抗拉强度/
MPa延伸率/
%截面收缩率/
%屈服强度A/
MPa硬化系数B/
MPa硬化指数n 应变率敏感
系数c温度软化
系数m7830 45 1380 12 58 1269 810 0.479 0.04 1 表 8 花岗岩靶成坑参数现场测量及三维扫描结果
Table 8. Direct measurement and 3D scanning results of crater parameters of granite targets
试验 子弹着角/(°) 侵彻速度/(m∙s−1) 侵彻深度/mm 侵彻弹坑最大直径/mm 侵彻弹坑最小直径/mm 现场测量 三维扫描 现场测量 三维扫描 现场测量 三维扫描 靶1 −3.5 638 75.05 76.29 310 327.98 245 248.36 靶2 −3.5 667 72.19 72.48 430 408.24 275 283.00 靶3 −1.5 673 96.00 91.73 410 402.60 265 261.67 表 9 实验和数值模拟得到的花岗岩靶侵彻结果比较
Table 9. Comparison of penetration results obtained from penetration test and numerical simulation
方法 侵彻深度/mm 侵彻弹坑最大直径/mm 侵彻弹坑最小直径/mm 实验 80.62±10.46 381.47±49.60 263.01±14.75 数值模拟 80.02 400.00 300.00 误差/% −0.75 4.86 14.07 -
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