Dynamic characteristics and constitutive model of coal samples with different length diameter ratio
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摘要: 为研究冲击荷载下不同长径比煤样的动力学性能,借助改进的霍普金森压杆实验装置(ϕ75 mm),开展6个冲击等级(4.18~8.03 m/s)、4种长径比(0.33~1.33)下的冲击压缩实验,并结合灰色关联理论分析动力学参数与长径比之间的关联性,建立基于力学机制、Weibull分布、D-P准则的4参数单轴煤岩强度型统计损伤模型。研究表明:①煤样长径比与应变率、动抗压强度、耗散能均呈二次函数关系,且耗散能随长径比增加而降低; 与电磁能呈一次函数关系,且保持正相关。②煤样长径比对动力学参数的影响排序为:电磁能(0.88)>动抗压强度(0.84)>耗散能(0.81)>应变率(0.78)。③基于Weibull分布、D-P准则构建初始本构模型,并借助动抗压强度σmax与应变率、长径比n的关系修正,进而对比实验应力-应变曲线,验证模型可靠性(R2>0.91)。Abstract: In order to study the dynamic performance of coal samples with different length diameter ratio under impact load, this paper used an improved Hopkinson compression bar experimental device (ϕ75 mm), and carried out the impact compression experiments under 6 impact grades (4.18~8.03 m/s)and 4 aspect ratios(0.33~1.33).It analyzed the correlation between the dynamic parameters and the aspect ratio in combination with the gray correlation theory, and this study then established a 4-parameter uniaxial strength type statistical damage model of coal and rock based on the mechanical mechanism, Weibull distribution and D-P failure criterion.Results show that: ① The length diameter ratio of coal samples has a quadratic function relationship with the strain rate and dynamic compressive strength; The relationship between the dissipation energy and the aspect ratio is a quadratic function, and the dissipation energy decreases with the increase of the aspect ratio; The relationship between the electromagnetic energy and the aspect ratio is a linear function and keeps a positive correlation. ② According to the grey correlation theory, this study obtained the influence order of length diameter ratio of coal sample on dynamic parameters: electromagnetic energy(0.88)>dynamic compressive strength(0.84)>dissipation energy(0.81)>strain rate(0.78).③ The initial constitutive model is constructed based on Weibull distribution and D-P criterion, and the dynamic compressive strength σmax and strain rate、the relationship between length to diameter ratio n was corrected, and then the experimental stress-strain curves were compared to verify the reliability of the model(R2>0.91).
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Key words:
- aspect ratio /
- strain rate /
- SHPB /
- grey correlation /
- damage constitutive model
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表 1 煤样基础物理力学参数
Table 1. Fundamental physical and mechanical parameters of coal sample
密度/ (kg·m-3) 静态抗压强度/ MPa 弹性模量/ GPa 泊松比 孔隙率/% 1 307.10 18.39 0.89 0.43 2.54 表 2 SHPB冲击破坏实验数据统计
Table 2. Data of SHPB impact damage experiment
直径×高度/ (mm×mm) 编号 速度/ (m·s-1) 应变率$ \overline{\dot{\varepsilon}}$ /s-1 动抗压强度σmax/MPa 耗散能/J 辐射能/J 直径×高度/ (mm×mm) 编号 速度/ (m·s-1) 应变率$ \overline{\dot{\varepsilon}}$/s-1 动抗压强度σmax/MPa 耗散能/J 辐射能/J 75×25 CM1 5.06 120.04 22.45 3.65 0.08 75×75 MM1 4.63 103.62 7.06 2.21 0.46 CM2 5.64 136.51 12.62 7.45 0.19 MM2 5.58 123.86 11.35 3.29 0.63 CM3 6.32 146.01 35.82 9.19 0.15 MM3 6.00 139.03 12.97 5.55 0.97 CM4 6.86 159.39 34.38 12.57 0.31 MM4 6.54 149.244 13.97 6.61 0.93 CM5 7.47 177.79 32.92 13.36 0.56 MM5 7.40 169.07 15.27 7.16 1.18 CM6 7.78 182.29 43.14 14.08 0.63 MM6 8.03 176.79 20.37 9.34 1.65 75×50 ZM1 4.18 98.26 6.18 1.44 0.23 75×100 LM1 4.71 109.26 9.42 0.49 0.70 ZM2 5.25 122.50 11.00 2.04 0.43 LM2 5.69 125.68 11.82 2.59 0.78 ZM3 6.18 145.31 13.93 2.71 0.61 LM3 6.26 140.35 13.57 4.26 1.01 ZM4 6.76 155.58 16.89 5.95 0.87 LM4 6.84 152.81 14.12 4.37 1.08 ZM5 7.22 173.40 23.41 9.34 1.07 LM5 7.50 172.44 16.41 6.44 1.27 ZM6 7.61 180.04 26.32 9.42 1.24 LM6 7.90 180.98 18.07 8.25 1.38 表 3 动抗压强度拟合结果
Table 3. Fitting results of dynamic compressive strength
长径比 应变率拟合 R2 应变率/s-1 长径比拟合 R2 a -b a -b c 0.33 0.42 34.73 0.88 100 9.12 13.65 10.89 0.91 0.67 0.24 18.44 0.95 120 15.52 30.36 24.12 0.84 1.00 0.15 8.40 0.91 140 21.91 47.07 37.35 0.99 1.33 0.11 2.61 0.98 160 28.31 63.78 50.57 0.99 — — — — 180 34.71 80.50 63.80 0.98 — — — — 200 41.11 97.22 77.03 0.98 表 4 应变率-耗散能拟合结果
Table 4. Fitting results of strain rate and dissipation energy
长径比 应变率拟合 R2 a b 0.33 0.16 -15.02 0.95 0.67 0.11 -10.53 0.85 1.00 0.10 -9.72 0.97 1.33 0.09 -7.60 0.95 表 5 长径比-耗散能拟合结果
Table 5. Fitting results of length diameter ratio and dissipation energy
应变率/s-1 长径比拟合 R2 a b c 100 -1.12 0.37 1.45 0.72 120 1.54 -5.17 6.14 0.98 140 4.21 -10.71 10.84 0.99 160 6.87 -16.25 15.53 0.96 180 9.53 -21.79 20.22 0.94 200 12.19 -27.33 24.92 0.92 表 6 应变率-电磁辐射能拟合结果
Table 6. Fitting results of strain rate and electromagnetic radiation energy
长径比 应变率拟合 R2 a b 0.33 0.009 -1.06 0.92 0.67 0.012 -1.04 0.96 1.00 0.011 -0.73 0.97 1.33 0.010 -0.38 0.99 表 7 长径比-电磁辐射能拟合结果
Table 7. Fitting results of length diameter ratio and electromagnetic radiation energy
应变率/s-1 长径比拟合 R2 a b 100 0.56 -0.16 0.99 120 0.53 0.08 0.99 140 0.51 0.33 0.98 160 0.48 0.57 0.95 180 0.45 0.85 0.91 200 0.42 1.06 0.84 表 8 灰色综合关联结果
Table 8. Grey comprehensive correlation results
比较序列 综合关联度 应变率 0.78 动抗压强度 0.84 耗散能 0.81 电磁能 0.88 表 9 本构模型拟合参数
Table 9. Fitting parameters of constitutive model
编号 n $ \dot{\varepsilon}$/s-1 E/GPa εm/‰ R2 CM6 0.33 182.29 37.11 7.05 0.95 ZM6 0.67 180.04 6.20 13.01 0.93 MM6 1.00 176.79 25.00 5.40 0.91 LM6 1.33 180.98 9.50 5.63 0.99 -
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