冲击载荷下磁铁矿石完全断裂强度的尺寸效应

矿石完全断裂是实现有效机械破碎的前提,为研究磁铁矿石完全断裂强度的尺寸效应,本文开展了落锤冲击加载实验,分析了立方体试件承受的冲击力时程曲线特征、不同尺寸试件的冲击强度与冲击速率的关系和完全断裂强度与尺寸的理论关系。研究表明:立方体试件冲击力的变化经历了冲击力快速上升阶段、稳定加载阶段、冲击力下降阶段和回升与震荡阶段,冲击力有效加载时间为6～8ms;落锤对磁铁矿石的冲击作用表现出显著的尺寸效应,冲击强度随冲击速率的增大而增大,但增长的速率随试件尺寸的降低而升高;随着立方体试件尺寸的增大,完全断裂强度呈先减小后增大的变化特征,存在完全断裂强度最低的矿石尺寸。研究结果对优化破碎机械工艺参数、提高矿石破碎效率具有一定理论指导意义。

Size effect on complete fracture strength of magnetite under impact load

Complete fracture of ore is the premise of effective mechanical crushing, the dropweight impact experiments were carried out to research the size effect on complete fracture strength of magnetite, and the time-history curves of impact force of the cubicspecimens, the relations of impact strength to impact velocity with different sizes, the theoretical relation of complete fracture strength to the size were analyzed. The study showed that the change of impact force of the cubic specimens have experienced the stages of rapid ascent, stable loading, descent, rebound and oscillation, effective loading of impact force lasts for 6-8ms; significantsize effects of magnetite were shown under the drop weight impact, impact strength increases with the increase in impact velocity, but the increasing rate increases with the decrease in specimen size; complete fracture strength decreases first and then increases with the increase in specimen size, the lowest complete fracture strength ofspecimen size is existing.The study results have certain theoretical guiding significance for optimizing the process parameters of crushing machinery and improving the crushing efficiency of ore.