颗粒材料破碎演化路径细观热力学机制

沈超敏; 刘斯宏

doi:10.6052/0459-1879-18-340

颗粒材料破碎演化路径细观热力学机制

沈超敏,
刘斯宏^2),

河海大学水利水电学院,南京 210098

基金项目: 1) 国家自然科学基金(U1765205),国家重点研发计划(2017YFC0404800)以及中央高校基本科研业务费专项资金(2018B40914)资助项目.

详细信息

作者简介:
作者简介: 2) 刘斯宏,教授,博导,主要研究方向：土石坝工程、粒状体力学与土工袋技术. E-mail: Sihongliu@hhu.edu.cn

中图分类号: TV16;
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出版历程
- 刊出日期: 2019-01-17

EVOLUTION PATH FOR THE PARTICLE BREAKAGE OF GRANULAR MATERIALS: A MICROMECHANICAL AND THERMODYNAMIC INSIGHT

Shen Chaomin,
Liu Sihong^2),

Department of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing 210098, China

摘要

摘要: 颗粒材料在高应力环境下会发生颗粒破碎现象,颗粒破碎不仅影响颗粒材料的力学特性,同时与大量工程问题密切相关.目前的相关研究主要集中在唯象地描述颗粒破碎的演化以及破碎对力学特性的影响层面,对颗粒破碎演化路径的物理机制研究较少.本文基于热力学框架,采用细观力学中细观-宏观的均匀化方法推导了颗粒体系弹性能和破碎能量耗散,并在最大能量耗散的假设下,在热力学框架内,建立了理想化的无摩擦球体颗粒等向压缩过程的弹性-破碎模型,阐述了颗粒材料破碎演化路径细观热力学机制.由于模型的推导不依赖任何唯象的经验公式,因此模型中包含的参数均有明确的物理意义.模型预测与前人试验结果对比表明,材料的初始级配对弹性压缩模量和破碎应力的影响并不相同：不同分形维数级配对应的弹性体变模量存在极大值,而破碎应力却随着分形维数的增大单调递增;颗粒破碎的演化符合最大能量耗散原理,且颗粒材料的压缩曲线可以分为弹性-破碎-拟弹性3个机制不同的阶段.
- 颗粒材料 /
- 颗粒破碎 /
- 级配 /
- 热力学 /
- 细观力学
Abstract: Particle breakage of granular materials is ubiquitous in nature and engineering practices and often takes place under high stress levels. The phenomenon of particle breakage may not only influence the mechanical response of granular materials, resulting the contraction of the volume of the material and reduction of the shearing strength, but is also closely associated to a variety of engineering problems. The existing research is mainly focused on depicting the evolution of the particle breakage and uses a quantifiable parameter to relate the particle breakage to the subsequent mechanical response. However, little attention has been paid to exploring the underlying physics of the driving force that initiates and attenuates the particle breakage. In this study, we present the formulation of an elastic-breakage model for the isotropic compression of frictionless spheres in the framework of thermodynamics. In the model, both the elastic strain energy and the dissipation due to particle breakage are formulated using the micro-macro averaging procedure, which is often used in micromechanics of granular materials. The evolution path of the particle breakage is determined using the maximum energy dissipation hypothesis. As the modelling does not involve any empirical results, all the model parameters have concrete physical meanings. Comparison of the model prediction with the experimental data in the literature showed that the initial gradation has different effects on the elastic bulk modulus and the breakage stress: the bulk modulus increase initially and then decrease with the fractal dimension of the gradation, which implies that there is a peak bulk modulus for a certain value of the fractal dimension; while the breakage stress increases monotonically with the increase of the fractal dimension. In addition, both the bulk modulus and the breakage stress increase monotonically with the increase of the polydispersity of the particle sizes. The evolution path of the gradation due to particle breakage is found to indeed satisfy the maximum dissipation hypothesis. Both experimental results and model prediction show that the compression curve of granular materials can be divided into three stages: the elastic compression stage under low compressive stress, particle breakage stage and the pseudoelastic compression after sufficiently large amount of particle breakage.
- granular material /
- particle breakage /
- gradation /
- thermodynamics /
- micromechanics

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