Force Chain Recognition And Reconstruction Analysis Of Two Dimensional Granular System

Granular materials is common in people's daily production and life,such as sand,granary,soil slope,debris flow and so on,and people are both familiar and unfamiliar with it.Macroscopic,the performance of granular material is both rapid and explosive,so it often bring us help or disaster;On the microscopic,the granular material is formed by the accumulation of a large number of interacting discrete particles,therefore there is very complex internal behavior in the granular matter,and behind this complex behavior is a powerful and mysterious force chain network.In order to guide the macroscopic mechanical behavior of granular materials,we need to study the microscopic mechanical behavior and properties,and finally establish the macroscopic-mesoscopic-microcosmic relationship.In order to study the formation and structure of internal force chains in granular systems,the formation and structure of the internal force chains in the granular system were investigated by using the two-dimensional particle system.The digital image correlation method(DIC)was be used in studying the internal force chain evolution behavior;Extracted and analyzed the force chains of the system,and the factors such as the state of force transfer,the angle between particles and the diameter of particles were be put forward and analyzed;A simple method to identify the path and break point of the force chains is proposed based on the factors which would influent the force chains;The model of particle system was established by PFC(Particle Flow Code),and the displacement field,velocity field and force chain of the system were be analyzed.This paper mainly completed the following work:(1)Access to relevant domestic and foreign literature,and introduced the research status of particulate matter and its internal force chain.(2)The DIC method and the calculation method of inter-particle contact force based on DIC were briefly introduced.(3)A series of experiments were carried out about the two-dimensional particle system subjected to external concentrated load.The images of the particle system in the process of experiment were collected in real time.After the experiment,calculated and analyzed the images to get the displacement and strain of the system.Post-processing using Matlab software for inter-particle contact force programming and related graphics rendering.(4)The state of the particles in the particle system was analyzed,and the state of transverse force transfer and longitudinal force transfer were proposed.The effects of particle angle,particle diameter and the contact area between external load and particle were be discussed;The effects of angle(?)and force angle(?)on the fracture of the force chain were be analyzed;And the distribution of the contact force and the displacement field of the particle system were analyzed,and the development trend of the force chains of the cylindrical granular system was analyzed.(5)The displacement and moving direction of each particle in the steel ball system were analyzed by DIC method,and the displacement threshold SC and the angle threshold ?d of the particles during the concentrated force loading are defined.A method of predicting the force path in the particle system by threshold judgment is presented,and the prediction of the break point position on the force chain is given.(6)PFC software was used to simulate the test of particles under the concentrate force.The velocity field,the displacement field and the force chain of the system were be analyzed,and the simulation method is used to validate the method of predicting force path and the position of the fracture of particle system.