The Numerical Test Method Based On DDA And Its Application

Under the mixed high order DDA frame,the numerical simulation of the closed circuit control mechanism of the electro-hydraulic servo test machine has been realized through deep development and innovation.A numerical test method has been established to simulate the bear capacity,deformation and failure mechanism of rock materials and the numerical experimentation has been carried out on the uniaxial mechanical properties of the rock materials.Firstly,the research methods of rock basic mechanical properties and the development process of mechanical testing machine were briefly introduced,and the existing research progress of numerical experiments was reviewed.Then,the servo control principle and the secondary development of the hybrid high-order DDA method were mainly introduced to realize the simulation of servo control loading technology.After that,the correctness and feasibility of the program was verified by a two block contact model which can be solved analytically.Further,the numerical test model of the actual rock sample was established by electron microscope scanning and image recognition,which truly reflects the composition and contact characteristics of the mineral particles inside the rock material.In order to establish the relationship between the mesoscopic structure of rock and the macroscopic mechanical response,a new method was provided to establish the relationship between the microstructure structure of rock and the macroscopic mechanical response.The results are as follows:(1)The basic formulas of each submatrix of mixed higher-order DDA method were derived,and three problems,namely,special simplex integral,initial stress and contact,were clarified.(2)The DDA source program was redeveloped with C language,and the servo control system and joint unit program were embedded.Then,a simple two-block contact model was used to verify the program.The results are reasonable and effective.(3)With the help of SEM technology,the texture mineral composition analysis was carried out,and the image recognition and edge extraction algorithms were developed by Matlab,and then the image was reconstructed digitally.The model can truly reflect the internal structural characteristics of rock samples.On this basis,parameters can be assigned.(4)The area of bulk material was subdivided through the preprocessing function of ANSYS,which meets the need of contact and calculation of material crystal.The results show that the peak and residual strength of each specimen were highly correlated with the crystal content and position of mesotectonite,and the displacement and stress of each specimen were anisotropic and extremely inhomogeneous.The distribution of joint surface and the parameters of block boundary have great influence on crack propagation.