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| Experimental research on the dynamic mechanical properties and breakage behaviors of magnetite caused by microwave irradiation |
| LIU Zhiyi1，2，GAN Deqing1，2，GAN Ze1，2 |
(1. School of Mining Engineering，North China University of Science and Technology，Tangshan，Hebei 063009，China；2. Development and Safety Key Laboratory of Hebei Province，Tangshan，Hebei 063009，China)
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Abstract In order to improve rock crushing efficiency and to reduce energy consumption of ore，the dynamic properties and breakage behaviours of magnetite caused by microwave irradiation with different microwave parameters were studied by using microwave irradiation combined with Hopkinson pressure bar(SHPB). The weakening mechanisms of mechanical properties of magnetite ore by microwave were revealed by the comparative analysis of macroscopic mechanical properties and microscopic structure characteristics. The results show that the influence of the irradiation power on the dynamic performance of magnetite is more significant than that of the irradiation time，and only when the power reaches a certain level will the effect of the irradiation time become gradually significant. With increasing the irradiation power，the damage to the internal structure of the magnetite sample undergo three stages：original crack propagation，intergranular fracture and intergranular fracture accompanied by transgranular fracture，and the slope of the elastic stage of the stress-strain curve gradually decreases with a shorter duration. The yield deformation stage becomes longer，and the post-peak stage presents three phenomena：“strain resilience”，“stress drop” and “post-peak plasticity” respectively. It is concluded that the weakening effect of microwave on P wave velocity and strength is more and more significant with increasing the irradiation power，and the magnetite sample undergo tensile and shear failure stages. It is pointed out that the weakening effect of microwave on the mechanical behaviours of magnetite is attributed to that the different sensibility of magnetite components to microwave results in differential expansion and further leads to intergranular fracture or rupture of granular inner defects. Therefore，when using microwave-assisted rock fragmentation，microwave heating parameters should be designed according to the mineral composition of the rock，the heating characteristics of each mineral and the fragmentation requirements，so as to improve the energy utilization rate and rock fragmentation efficiency of microwave-assisted rock fragmentation.
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2021, Vol. 40 
