Development And Application Of Discrete Element Simulation System For Mixing Materials

In resent years, through the development of computer technology, many researchers apply numerical analysis to engineering research. In the research field of the mixing materials, numerical simulation is one of the most important techniques, but the research progresses for the mixing composite material which is composed with elastic materials and viscoplastic materials have not developed enough. Concrete is one of the most important materials for hydraulic engineering project, and is also composite material which is composed from several raw materials but the reasonable tool for simulating the process of mixing concrete does not existed now. In this respect, author developed a simulation system of mixing materials by applying discrete element method, and then applied it to simulate the process of mixing composite material, i.e. mixing concrete.In the beginning of this research, the experiments and numerical simulations of mixing plastic balls were conducted for verification of this simulation system. In the results, the analytical results insisted very good agreement with the experiment results. Then anthers regarded that concrete as a material composed with viscoplastic materials i.e. mortar and elastic materials i.e. coarse aggregate, and established the method of setting parameters of each material property. For verification of this system for mixing concrete, the consistency tests of concrete were conducted to various mixing proportion, and through comparing the test results with the analytical results, it was verified that this system can simulate the process of mixing concrete in high accuracy.On the other hand, to research mixing materials or develop a mixing device, it is necessary to evaluate the mixing condition of materials. In the research field of powder mixing, standard deviation of volume consistency of the marker materials is usually used as the index for evaluating mixing condition of materials, i.e."mixing index". But the mixing index for concrete mixing has not developed yet. Therefore, in this research, concrete was modeled as mortar and aggregate two phase material, the standard deviation of volume percentage of coarse aggregate to concrete of samples were calculated as mixing index for concrete. Then the experiments of measuring mixing index for concrete were conducted for its verification.Author applied this developed discrete element simulation system for mixing materials and concept of mixing index to simulate and analyze the mixing performance of existance static mixing device, and developed new type static mixing device. In the results, the mixing mechanism of existance static mixer and its problem were explained.Through these analyses, author developed new type static mixer, and conducted the experiment and analysis of mixing materials to discuss its mixing performance. In the results, it was found that this simulation system is able to simulate the problem of mixing material in high accuracy.