Theoretical Study Of The Microscopic Dynamics Of Material Growth And Fracture

The study of the microscopic dynamic process of surface growth and materialfracture has important significance in the regions of scientific research and technologyapplication. The theoretical research to the microscopic dynamic process of surfaceroughening growth and material fracture will help to understand the macroscopic lawand microscopic mechanism of the roughening growth and material fracture. In thisdissertation, based on the ballistic deposition model with shadowing, the influence ofshadowing effects on scaling properties and its finite size effects in the depositiongrowth process of material is numerically simulated studied. At the same time, basedon extended fiber bundle models (FBM), the influence of the microstructure andfracture mechanism of material on the tensile fracture properties and statisticaldynamic properties is theoretical studied by analytical analysis and numericalsimulation methods. The specific work can be divided into the following areas:The shadowing effect of the oblique incidence of the particles in a surface growthprocess is a long-range interaction. In order to study of the impact of shadowing effecton the roughness growth process, the scaling properties of the oblique incidenceballistic deposition model and the finite size effects of the ballistic deposition modelwith shadowing are studied by numerical simulation method. The simulation resultsshow that in the large region of incidence angle, the growth surface will appearprominent anomalous scaling property, which means that long-range interactions areresponsible for the arising of anomalous scaling property. In addition, when theshadowing effect appears, the skewness and kurtosis significantly dependent on thesystem size, as a result, the skewness and kurtosis is no longer universal.In order to reveal the fracture dynamic properties of strong heterogeneousmaterials in the short-range correlation, the tensile fracture process of the FBM withstrong heterogeneities is detailed studied by numerical simulation. In this FBM, thefiber bundle is composed by a certain proportion of normal fracture fibers and highstrength fibers. The simulation results show that there is a local plastic state in thefracture process of the fiber bundle at a critical fraction of unbreakable fibers c. Inthe presence of high strength unbreakable fibers, the fiber bundle will has a greaterload capacity and longer fracture relaxation process, at the same time, the avalanchesize statistical property of the FBM in local load sharing is distinctly affected by thefraction of unbreakable fibers.The fracture process of disorder material will be dramatically affected by thecontinuous damage phenomenon of the fiber. The two main parameters of thecontinuous damage FBM with strong disorder are the expected value of the total number of failures allowed for a single fiber and the residual stiffness. Thesimulation results based on this model indicate that when the value of is small, thecritical stress and the step number of load increase before complete rupture increasewith following a power law relation, while in the large limit of, the criticalstress and the step number will reach to a saturate value. For the avalanche statisticalproperties, the avalanche size distribution of the model with various parameters can bewell fitted with a power law asymptotic behavior, while the parameters of the modelcan only influence the specific exponents of the power law.To describe the smooth nonlinear constitutive relations of some micro-structure,the multilinear FBM is constructed based on the bilinear FBM. In the global loadsharing (GLS) case, the macroscopic fracture property and the microscopic statisticalquantity are analyzed by analytic approximation and numerical simulation. Themaximum number of a fiber damaging and the ratio of Young modulus decay canengender significant impact on the macro-fracture property, while in the micro-scale,the impacts on the avalanche size distribution mainly fall on the power law exponents.The analytical results and the numerical simulation results can be well fitted eachother.The FBM with stick-slip dynamics and a variable Young modulus can welldescribe the tensile fracture process of silk and other extensive biologic fibers. Thefracture avalanche process of the model is analyzed by analytic approximation andnumerical simulation in the case of GLS. From a macroscopic view, the constitutivecurves show different morphologies varying from a local plastic state to a unimodalparabola. While in microscopic, the parameters of the model can only bring slighteffect on the exponents of the power law in the avalanche size distribution. Theanalytical results and the simulation results can coincide with each other inquantitative manner.In this dissertation, the impacts of nonlocal interaction in the growth process withthe oblique incidence on the anomalous scaling properties of roughening growthsurface and its boundary effects are explored by the studying of shadowing effects inthe ballistic deposition model with shadowing. The theoretical research of extendedFBM reveals the macroscopic properties and its microscopic mechanism in thematerial fracture process, which has great significance in improving of compositematerial properties and predicting macroscopic fracture of materials.