恒定剪切作用下全尾膏体微观结构演化特征

Microstructural evolution characteristics of an unclassified tailing paste in constant shearing

全尾砂膏体作为一种塑性流体,其内部结构的形貌特征与浆体流动性能紧密相关,研究剪切过程中微观结构的演化特征,对于分析膏体管道输送及制备工艺中的流动行为具有十分重要的意义.本文借助扫描电镜技术,拍摄了不同搅拌时间的膏体微观结构图像.综合应用计算机图像处理技术和分形理论,估算了膏体微结构的分形盒维数,提出以结构系数λ作为微结构形貌特征的表征指标,建立了搅拌过程中微结构时间演化过程的数学模型.某铅锌尾矿膏体相关实验的结果表明:其结构系数λ随搅拌时间急剧减小,并逐渐趋于平缓,最终达到某一平衡状态.通过对实验数据的拟合,得到其演化模型相关的破坏系数及恢复系数,分别为0.171及0.491.

As a plastic fluid, the morphological features of internal structure in an unclassified tailing paste closely relate to its flow properties. Studies on the evolution characteristics of internal structure during the sheafing flow process have extremely important significance for analyzing flow behavior in pipeline transportation and paste preparation. In this paper, scanning electron microscopy was used to investigate the meso-structure images of the paste at different mixing time. The fractal dimensions of these meso-structure images were estimated by the image processing technology and fractal theory. A structure coefficient A was put forward to explain the morphological features of meso-structure, and a time-evolution mathematical model of meso-structure was built in the mixing process. Some related experiments were done for a lead-zinc tailing paste. It was found that the structure coefficient A flattened out gradually after a steep fall with mixing time, and finally reached an equilibrium state. The failure coefficient and restitution coefficient in the evolution model were obtained to be 0. 171 and 0. 491 respectively by fitting experimental data.