颗粒材料剪切流动状态转变的环剪试验研究

发布时间：2018-02-15 11:28

本文关键词： 颗粒材料环剪仪临界剪切速率剪切流动流动状态转化　出处：《力学学报》2016年05期 　论文类型：期刊论文

【摘要】：颗粒材料的剪切流动行为广泛地存在于滑坡、泥石流等自然灾害以及矿物原料传输、泵送等工业过程中.颗粒材料在不同体积分数、剪切速率和应力约束下会表现出不同的流动状态并发生相互转化.对颗粒材料在剪切流动过程中力学特性的研究有助于加深理解其发生不同流动状态的内在机理,为解决相应的颗粒材料问题提供理论依据.为此,本文研制了颗粒材料剪切流动的中型环剪仪,并对颗粒材料在不同法向约束应力和剪切速率下的剪切应力和体积膨胀率进行了测试.结果表明,剪切应力和体积膨胀率均随剪切速率的增大而增大,但增长速率在临界剪切速率处发生转变,使其随剪切速率的平方呈分段式线性增长.通过对颗粒材料在不同剪切速率和惯性数下有效摩擦系数变化趋势的分析,讨论了颗粒材料由慢速流向快速流转化的基本规律,以及在临界剪切速率处发生流动状态转化的内在条件.此外,通过对不同法向应力下临界剪切速率以及快速流动下运动规律的测试,发现临界剪切速率随法向应力的增加而减小,即法向应力可促进颗粒材料由慢速流向快速流的转化,但在快速流动状态下的有效摩擦系数对法向应力不敏感.以上对颗粒材料在不同剪切速率、法向应力下流动状态的环剪试验研究有助于揭示其发生不同流动状态转化的内在机理.
[Abstract]:The shear flow behavior of granular materials is widely used in industrial processes such as landslides, natural disasters such as debris flows and mineral raw materials transport and pumping. Under shear rate and stress constraints, different flow states will appear and mutual transformation will occur. The study of mechanical properties of granular materials in shear flow process will contribute to a better understanding of the intrinsic mechanism of different flow states. In order to provide the theoretical basis for solving the corresponding particle material problems, a medium size annular shear apparatus for the shearing flow of granular materials is developed in this paper. The shear stress and volume expansion ratio of granular materials under different normal confinement stress and shear rate are tested. The results show that both shear stress and volume expansion ratio increase with the increase of shear rate. However, the growth rate changes at the critical shear rate, which increases linearly with the square of the shear rate in a piecewise manner. The variation trend of effective friction coefficient of granular materials at different shear rates and inertial numbers is analyzed. In this paper, the basic law of the fast flow transition from slow to fast flow of granular materials is discussed, and the internal conditions of flow state transition at critical shear rate are also discussed. It is found that the critical shear rate decreases with the increase of normal stress, that is, the normal stress can promote the transformation of particle materials from slow to fast flow through the measurement of the critical shear rate under different normal stresses and the law of motion under the rapid flow. But the effective friction coefficient under the condition of rapid flow is not sensitive to normal stress. The experimental study on the flow state under normal stress is helpful to reveal the internal mechanism of the transition of different flow states.
【作者单位】：大连理工大学工业装备结构分析国家重点实验室;
【基金】：国家自然科学基金(U1234209,11572067) 国家重点基础研究发展计划(2010CB731502)资助项目
【分类号】：O347.7

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