| People build mechanical model of particle system from engineering practice,and use numerical simulation,indoor test,theory analysis and other methods,and have achieved fruitful research results under the condition of multi pipe.To explain the macro phenomena of particle system,we need to break the inherent concept with the idea of multi-scale,cross-disciplinary and interdisciplinary,and explore the dynamic mechanism of particle system from macro,micro and micro perspectives by means of interdisciplinary and innovative research.Granular material shows a unique phenomenon different from pure gas,liquid and solid matter.The particle system has different mechanical properties due to its different composition and form.The mechanical mechanism of the particle system from solid to liquid phase has been a difficult problem to find but not be achieved.It is difficult to give a reasonable explanation for many phenomena only from the perspective.So far,there is no theory that can describe the mechanical mechanism of the liquid phase and the mutual transformation between the two.Force chain is a very important concept in mesoscale of particle system research,similar to the concept of soil skeleton in soil mechanics.Force chain is an important medium connecting macro and micro,and it is a stable structure of interaction between particles on micro scale.Its evolution directly affects the macro mechanical properties of particle system.Based on the summary of the research and development of particle materials,this paper designs the particle system test under linear load,and analyzes the experimental data by digital image correlation(DIC)and image processing technology.Through the analysis of the deflection angle and coordination number of particles,the displacement,strain field and contact force of the particles system,the evolution process of force chain and force chain network is explored,and the factors of the fracture and failure of the force chain are analyzed.At the same time,PFC-2D(particle flow code 2D)software is used to simulate the test,and the displacement field,force chain and particle structure are obtained.The experimental results and numerical simulation results are compared and discussed.The main work of this paper is summarized as follows:(1)The related literatures of the mechanical properties of granular materials are reviewed,and the research progress of particle materials,the measurement technology of indirect contact force of particles,the theory,test and Simulation of force chain are introduced in detail;(2)The development,principle and the influence of the selection of calculation parameters on the accuracy and speed of the DIC method are introduced.Finally,the principle of indirect contact force measurement and its advantages in particle system research are described;(3)The compression test of particle system under linear load is designed,the main equipment used in the test is introduced,and the preparation,operation and matters needing attention in the test are described in detail;(4)The load test of particle system under linear load is carried out,a large number of test data are obtained,and the deformation information of particle system is obtained by digital image correlation method.The program of particle element method is realized by combining image processing technology and programming method.It can obtain the information of deflection angle,coordination number,displacement field,strain field and indirect contact force of particles during the loading process.The qualitative analysis and quantitative calculation of force chain are realized.The dynamic evolution of force chain and force chain network is analyzed,and the evolution of force chain network to particle macro mechanics is discussed the effect of performance;(5)The experiment of particle system under load is simulated by PFC,and the evolution of force chain is explored from displacement,force chain and structure. |
PDF Full Text Request