Parameter Characterization And Force Chain Analysis Of Three-dimensional Particle System Based On Refractive Index Matching Technique

Particle system is widely existed in people’s daily life,and its nature is composed of a large number of discrete and irregular solid particles,which is a kind of nonlinear system between ideal fluid system and ideal solid system,so the particle system cannot be studied by general solid or fluid theory.Scholars’ research on particulate matter has been divided into three aspects: the study of inter-particle contact theory on the microscopic scale,the study of force chains on the fine scale and the study of mechanical behavior of the particulate system on the macroscopic scale.Many mechanical properties presented by the three-dimensional particle system at the macroscopic level are determined by the complex mechanical response of the force chain network at the fine scale,and the study of force chains at the fine scale has become the focus of linking macro-and microscopic studies.From the dimensional level,the study of two-dimensional particle systems is relatively complete,while in the study of three-dimensional particle systems,most scholars use numerical simulations to study them,and there is a lack of experimental verification for the simulation results due to the lack of suitable experimental means.Therefore,this paper focuses on the study of three-dimensional particle system from the experimental point of view,and initially discusses its parameter characterization and three-dimensional force chain breakage.In this paper,we conduct an experimental study on the compression of the 3D particle system based on the refractive index matching technique to obtain the 2D fault information inside the particle system,analyze the experimental data using digital image processing techniques,extract the force chain and force chain network,and analyze the evolution process.A three-dimensional force chain fracture identification method is proposed,and a three-dimensional particle system compression model is established using numerical simulation software to verify it.The main work of this paper is summarized as follows:(1)Compression experiments based on refractive index matching technology are carried out for the difficult problem of identifying the internal information of the three-dimensional particle system.We analyzed and selected the particle materials,modulated the solution matching the refractive index of the particle materials for several experiments,and created a liquid refractive index matching measurement method.Complete the compression experiment of three-dimensional particle system based on refractive index matching technology,and realize the identification of the internal information of three-dimensional particle system.(2)Processing the 2D tomographic images acquired in the experiment to obtain the internal information of the 3D particle system.Among them,a circle-by-circle radius scanning method is innovatively proposed to solve the problem of inaccurate radius identification when the Hough transform circle detection method identifies the particle edges.(3)A three-dimensional force chain break identification method based on displacement difference threshold and deflection angle threshold is proposed.By analyzing the inter-particle displacement inside the three-dimensional particle system and comparing the changes of displacement and deflection angle between the before and after moments,we determine whether the force chain is broken or not.Finally,numerical simulations are introduced to construct a large scale model to validate the method in the generalized domain.