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Dynamic crushing characteristics and energy consumption characteristics of magnet ore under different impact specific energies |
| GAN Deqing1, 2, 3, 4, YU Zehao1, 2, 3, 4, LIU Zhiyi1, 2, 3, 4, SUN Haikuan1, 2, 3, 4 |
(1. College of Mining Engineering, North China University of Technology, Tangshan, Hebei 063210, China; 2.Collaborative Innovation Center of Green Development and Ecological Restoration of Mineral Resources, Tangshan, Hebei 063210, China;
3. Hebei Province Key Laboratory of Mining Development and Security Technology, Tangshan, Hebei 063210, China;
4. Hebei Province Green Intelligent Mining Technology Innovation Center, Tangshan, Hebei 063210, China) |
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Abstract To investigate the influence of impact specific energy on the dynamic mechanical properties and crushing characteristics of magnetite stone, as well as to analyze the size effect of magnetite under varying loading energies, this study aims to determine the optimal loading energies for crushing ores of different sizes and to minimize energy loss. A separated Split Hopkinson Pressure Bar (SHPB) test system was employed to conduct impact experiments on magnetite ores of lengths 30, 35, 40, 45, and 50 mm, using four different impact air pressures. The analysis was conducted from five perspectives: deformation characteristics, strength characteristics, energy characteristics, cracking modes, and fragmentation degree. The results indicate that, for magnetite specimens of identical length, an increase in impact air pressure initially causes a decrease, followed by an increase in the dynamic modulus of elasticity; the peak strain and dynamic compressive strength both increase. Additionally, energy dissipation, the ratio of energy dissipation, and the unit volume of dissipated energy exhibit an upward trend. The fractal dimensions of ore lumps increase, while the average size of the fragments decreases, indicating a deeper degree of crushing. When impact air pressure is held constant, the dynamic mechanical characteristics of magnetite ore demonstrate a pronounced size effect. As specimen length increases, the dynamic modulus of elasticity increases exponentially, with a faster growth rate observed at lower air pressures. The dynamic compressive strength shows a linear increase, with a more rapid rate at higher pressures, while peak strain decreases. Furthermore, the dissipated energy and its proportion increase, and the dissipated energy per unit volume decreases. The fractal dimensions of the block size decrease, the average size of crushed pieces increases, and there is a significant increase in the number of larger fragments. The increase in specimen length inhibits the initiation of cracking in magnetite stone, alters the cracking mode, and reduces the number of cracks. The energy dissipation per unit volume is positively correlated with the fractal dimension, with a higher correlation coefficient than that observed with the negatively correlated average particle size of fragments. The increase in crushing specific energy promotes the crushing of magnetite stone, though this promotion effect gradually diminishes. As impact air pressure increases, the influence of unit crushing specific energy on the mechanical properties of magnetite stone becomes progressively weaker. Calculations suggest that the optimal crushing specific energy for magnetite stone is approximately 2.5, which yields a higher energy utilization rate. The findings of this study provide valuable guidance for the safe production of mines and the impact crushing of magnetite stone.
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2025, Vol. 44 
