动载作用下磁铁矿石破坏特性实验研究
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摘要
利用分离式Hopkinson压杆试验装置,开展了不同应变率下的磁铁矿石冲击实验。分析了磁铁矿石在动载下的力学特性和破坏裂纹演化过程,揭示了磁铁矿石块度分布规律。研究结果表明:磁铁矿石的动态弹性模量与动态强度的应变率效应显著,在不同应变率下,应力-应变曲线峰后卸载速率以及卸载方式存在差异。随应变率的提高,软化因子(K)减小,磁铁矿石软化程度加深。磁铁矿石强度比例因子λ与■呈线性分布,比能量吸收与■呈线性分布。磁铁矿石破碎形态具有明显的自相似性,随着应变率提高,磁铁矿石平均块度减小,分形维数增大,磁铁矿石破碎程度加剧,分形维数与应变率、比能量吸收均呈线性分布。通过绘制全对数粒度特征曲线直观地表达了矿石碎块的粒度分布规律,结合块度分布系数(C),进而得出了实现矿石破碎的合理应变率范围。研究成果对于磁铁矿石动载破碎机理分析、破碎块度分布及能耗分析具有重要的参考价值。
The impact experiments of magnetite ore under different strain rates were carried out by a splitting Hopkinson pressure bar(SHPB) equipment. The mechanical properties and the crack propagation of the magnetite ore under dynamic load were analyzed to evaluate the distribution pattern of the fragmentation of the magnetite ore. Experiment results indicate that the strain rate effect of the dynamic elastic modulus and strength of the magnetite ore is obvious. The unloading rates and unloading modes in the post-peak of stress-strain curve are different under different strain rates. With strain rate increasing, the softening factor(K) of the magnetite ore decreases and the softening degree increases. Both the relations between the strength scale factor(λ) of the magnetite ore and ■, and the specific energy absorption of the magnetite ore and ■are linear distribution. The broken form of the magnetite ore is of distinct self-similarity that the mean fragment size of the magnetite ore decreases, fractal dimension increases and the magnetite ore is broken strongly with strain rate. The fractal dimension increases linearly both with the strain rate and the specific energy absorption of the magnetite ore. The distribution pattern of the fragmentation of the magnetite ore, which is clearly revealed by means of the total logarithmic curve of the cumulative particle size, combined with the block distribution coefficient(C), the reasonable range of the strain rate of the magnetite ore crushing is obtained. The study results provide significant references for the analysis of the crushing mechanism of magnetite ore under dynamic load, the distribution of the fragmentation and the energy consumption.
The impact experiments of magnetite ore under different strain rates were carried out by a splitting Hopkinson pressure bar(SHPB) equipment. The mechanical properties and the crack propagation of the magnetite ore under dynamic load were analyzed to evaluate the distribution pattern of the fragmentation of the magnetite ore. Experiment results indicate that the strain rate effect of the dynamic elastic modulus and strength of the magnetite ore is obvious. The unloading rates and unloading modes in the post-peak of stress-strain curve are different under different strain rates. With strain rate increasing, the softening factor(K) of the magnetite ore decreases and the softening degree increases. Both the relations between the strength scale factor(λ) of the magnetite ore and ■, and the specific energy absorption of the magnetite ore and ■are linear distribution. The broken form of the magnetite ore is of distinct self-similarity that the mean fragment size of the magnetite ore decreases, fractal dimension increases and the magnetite ore is broken strongly with strain rate. The fractal dimension increases linearly both with the strain rate and the specific energy absorption of the magnetite ore. The distribution pattern of the fragmentation of the magnetite ore, which is clearly revealed by means of the total logarithmic curve of the cumulative particle size, combined with the block distribution coefficient(C), the reasonable range of the strain rate of the magnetite ore crushing is obtained. The study results provide significant references for the analysis of the crushing mechanism of magnetite ore under dynamic load, the distribution of the fragmentation and the energy consumption.
引文
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[18] 杜晶.不同长径比下岩石冲击动力学特性研究[D].长沙:中南大学,2011:44-49.
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[20] 李夕兵,古德生.岩石冲击动力学[M].长沙:中南工业大学出版社,1994:11-14.
[21] 梁昌玉,李晓,李守定,等.岩石静态和准动态加载应变率的界限值研究[J].岩石力学与工程学报,2012,31(6):1156-1161.LIANG Changyu,LI Xiao,LI Shouding,et al.Study of strain rates threshold value between static loading and quasi dynamic loading of rock[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(6):1156-1161.
[22] 李占金,乔国刚,米雪玉,等.冀东磁铁矿石粉碎过程节能降耗研究[J].中国矿业大学学报,2008,37(5):625-629.LI Zhanjin,QIAO Guogang,MI Xueyu,et al.Energy savings during magnetite ore preparation in eastern hebei province[J].Journal of China University of Mining & Technology,2008,37(5):625-629.
[23] 单晓云,李占金.分形理论和岩石破碎的分形研究[J].河北理工学院学报,2003,25(2):11-17.SHAN Xiaoyun,LI Zhanjin.Fractal theory characteristics and its application on rock fragmentation[J].Chinese Journal of Hebei Institute of Technology,2003,25(2):11-17.
[24] XU Yongfu.Explanation of scaling phenomenon based on fractal fragmentation[J].Mechanics Research Communications,2005,32:209-220.
[2] 谢和平,彭瑞东,鞠杨,等.岩石破坏的能量分析初探[J].岩石力学与工程学报,2005,24(15):2603-2608.XIE Heping,PENG Ruidong,JU Yang,et al.On energy analysis of rock failure[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(15):2603-2608.
[3] JANACH W.The role of bulking in brittle failure of rock under rapid compression[J].International Journal of Rock Mechanics & Mining Sciences & Geomechanics Abstracts,1976,13(6):177-186.
[4] OLSSON W A.The compressive strength of tuff as a function of strain rate from 10-6 to 103 s-1[J].International Journal of Rock Mechanics & Mining Sciences & Geomechanics Abstracts,1991,28(1):115-118.
[5] ZHAO Yangsheng,WAN Zhijun,FENG Zijun,et al.Triaxial compression system for rock testing under high temperature and high pressure[J].International Journal of Rock Mechanics and Mining Sciences,2012,52(6):132-138.
[6] 王浩宇,许金余,王鹏,等.水-动力耦合作用下红砂岩力学性质及能量机制研究[J].岩土力学,2016,37(10):2861-2868.WANG Haoyu,XU Jinyu,WANG Peng,et al.Mechanical properties and energy mechanism of red sandstone under hydro-dynamic coupling effect[J].Rock and Soil Mechanics,2016,37(10):2861-2868.
[7] DAI Feng,XIA Kaiwen.Loading rate dependence of tensile strength anisotropy of barre granite[J].Pure and Applied Geophysics,2010,167(11):1419-1432.
[8] DAI Feng,XIA Kaiwen,TANG Lizhong.Rate dependence of the flexural tensile strength of Laurentian granite[J].International Journal of Rock Mechanics and Mining Sciences,2010,47(3):469-475.
[9] 马冬冬,马芹永,袁璞,等.冻结黏土单轴与主动围压状态SHPB试验对比分析[J].振动与冲击,2017,36(19):255-260.MA Dongdong,MA Qinyong,YUAN Pu,et al.Comparison analysis and SHPB tests on artificial frozen clay in uniaxial load and confining pressure states [J].Journal of Vibration and Shock,2017,36(19):255-260.
[10] 卢志堂,王志亮.中高应变率下花岗岩动力特性三轴试验研究[J].岩土工程学报,2016,38(6):1087-1094.LU Zhitang,WANG Zhiliang.Triaxial tests on dynamic properties of granite under intermediate and high strain rates[J].Chinese Journal of Geotechnical Engineering,2016,38(6):1087-1094.
[11] 平琦,马芹永,卢小雨,等.被动围压条件下岩石材料冲击压缩试验研究[J].振动与冲击,2014,33(2):55-59.PING Qi,MA Qinyong,LU Xiaoyu,et al.Impact compression test of rock material under passive confining pressure conditions[J].Journal of Vibration and Shock,2014,33(2):55-59.
[12] 刘石,许金余,白二雷,等.基于分形理论的岩石冲击破坏研究[J].振动与冲击,2013,32(5):163-166.LIU Shi,XU Jinyu,BAI Erlei,et al.Research on impact fracture of rock based on fractal theory[J].Journal of Vibration and Shock,2013,32(5):163-166.
[13] GAO Feng,XIE Heping.Statistically fractal strength theory for brittle materials[J].Acta Mechanica Solida Sinica,1996,9(1):42-51.
[14] 王登科,刘淑敏,魏建平,等.冲击载荷作用下煤的破坏特性试验研究[J].采矿与安全工程学报,2017,34(3):594-600.WANG Dengke,LIU Shumin,WEI Jianping,et al.The failure characteristics of coal under impact load in laboratory[J].Journal of Mining & Safety Engineering,2017,34(3):594-600.
[15] 张文清,石必明,穆朝民.冲击载荷作用下煤岩破碎与耗能规律实验研究[J].采矿与安全工程学报,2016,33(2):375-380.ZHANG Wenqing,SHI Biming,MU Chaomin.Experimental research on failure and energy dissipation law of coal under impact load[J].Journal of Mining & Safety Engineering,2016,33(2):375-380.
[16] LI X B,LOK T S,ZHAO J,et al.Oscillation elimination in the Hopkinson bar apparatus and resultant complete dynamic stress-strain curves for rocks[J].International Journal of Rock Mechanics and Mining Sciences,2000,37(7):1055-1060.
[17] 王礼立.应力波基础[M].北京:国防工业出版社,2010:39-64.
[18] 杜晶.不同长径比下岩石冲击动力学特性研究[D].长沙:中南大学,2011:44-49.
[19] 许金余,刘石.大理岩冲击加载试验碎块的分形特征分析[J].岩土力学,2012,33(11):3225-3229.XU Jinyu,LIU Shi.Research on fractal characteristics of marble fragments subjected to impact loading[J].Rock and Soil Mechanics,2012,33(11):3225-3229.
[20] 李夕兵,古德生.岩石冲击动力学[M].长沙:中南工业大学出版社,1994:11-14.
[21] 梁昌玉,李晓,李守定,等.岩石静态和准动态加载应变率的界限值研究[J].岩石力学与工程学报,2012,31(6):1156-1161.LIANG Changyu,LI Xiao,LI Shouding,et al.Study of strain rates threshold value between static loading and quasi dynamic loading of rock[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(6):1156-1161.
[22] 李占金,乔国刚,米雪玉,等.冀东磁铁矿石粉碎过程节能降耗研究[J].中国矿业大学学报,2008,37(5):625-629.LI Zhanjin,QIAO Guogang,MI Xueyu,et al.Energy savings during magnetite ore preparation in eastern hebei province[J].Journal of China University of Mining & Technology,2008,37(5):625-629.
[23] 单晓云,李占金.分形理论和岩石破碎的分形研究[J].河北理工学院学报,2003,25(2):11-17.SHAN Xiaoyun,LI Zhanjin.Fractal theory characteristics and its application on rock fragmentation[J].Chinese Journal of Hebei Institute of Technology,2003,25(2):11-17.
[24] XU Yongfu.Explanation of scaling phenomenon based on fractal fragmentation[J].Mechanics Research Communications,2005,32:209-220.
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