Compression Induced Progressive Breakage Mechanism Of Particle Beds Made Of Quasi-brittle Material

Particulate materials are widely used in civil engineering and chemical engineering because of their satisfactory mechanical property. While particle can be broken under high stress level, which would affect the macroscopic physical mechanical properties, and then affects the deformation, strength and safety of the beds.. Considering the effect of particle breakage, we need to pay more attention on it. In this thesis, we adopted two types of quasi-brittle material and have done some research on the basic particle breakage mode and internal mechanism, which based on the method of experiments and numerical simulation. More details are as follows:(1) The experiment of quasi-static compression breakage for single particle was carried out. From the experiment, we can obtained the basic breakage mode of single particle, and found that the main cause of particle breakage is tension effect, which induced two intersecting fractures. With the help of the Force-Displacement curve we obtained and related theories, we can calculate some basic parameters of the particulate material, like the tension strength and elasticity modulus, which can be used in the numerical simulation.(2) Two types of quasi-brittle material named aluminium oxide particle and figuline particle were adopted for the compression breakage experiment of multiple particles. A set of experiment equipment was invented, which realized real-time observation of particle breakage. By changing the parameters: particle material, particle size and particle size distribution, we obtained the progressive breakage mechanism with the condition of monotone increasing load, and proposed a breakage mechanism model. A model of three development stages for Force-Displacement curves was proposed, too.(3) Different topography of the fractures plane were observed and compared by scanning electron microscope. The result showed that the fractures were mainly induced by tension effect. Specially, we improved the concept of relative breakage potential by Hardin based on the sieving analysis test. The concept of broken potential and the energy imported for the breakages were combined to analyzed the degree of breakage..(4) Numerical simulation for single particle breakage and multiple particles breakage were carried out based on the theories of Nonlinear damage fracture mechanics. The numerical simulation results are consistent with the experiment results. The effects of fracture energy to particle breakage mode and macro-response were also discussed in the thesis, which revealed the breakage law further.