Papers by Keyword: Mesomechanics

Abstract: The peculiarities of the accumulation of structural and mechanical defects on the surface of the D16chT aluminum alloy under significant plastic strains are analyzed. The peculiarities of the surface strain hardening are found, and the geometrical parameters of the relief formations are described. The relationship between multiple cracking and specimen deformation is established. It is proved that the deformation relief parameters can be used to assess damage of the D16chT alloy under static deformation.

Abstract: The XFEM was used to forecast the sub-interface crack propagation paths of carbon fiber reinforced composites, and the simulation results were compared with the SEM photos. The change of strain energy and damage dissipation energy in this process was also investigated. The results indicated that the existence of fiber had a certain influence on the crack propagation direction. And the structure energy changed along with the crack propagation.

Abstract: Using the finite element method analysis the influence of the enhanced body size to stress concentration factor and stress distribution between the enhanced body in nanocomposite coating and the matrix interface. By preliminary calculation, the paper predicts a trend that the stress distribution on the interface reduces with the decreases of the enhanced body size and the stress concentration. Theoretically proved the iomportant rule that in the field of organic composite materials if you want to improve the performance of composite materials ,the enhanced body size need to be reduced.

Abstract: Based on the Gurson-Tvergaard-Needleman micromechanical damage model, taking void growth ratio V_G as the damage variable established acoustic emission (AE) quantitative evaluation model. Taking steel 20 notched bar specimens tensile process as example, get AE information from yield to fracture process. Using ABAQUS analyzed the meso-damage process during tensile process of the specimens, and get the numerical solution of meso-damage parameters. Based on AE testing and the results of Finite Element Simulation, established the quantitative evaluation formula of V_G and AE cumulative hits N during 20 steel notched specimens tensile process. Result shows that, 20 steel from yield to fracture damage, the relationship between N and V_G is divided into two stage, namely linear damage stage and nonlinear damage stage. When the N reaches 61, the material is at the transition stage from linear damage stage to nonlinear damage stage.

Abstract: Railway ballast tamping operations is employed in order to restore the geometry of railway track distorted by train traffics. The selection of tamping parameter is usually dependent on field trials and practical experience, for lack of theoretical basis. This paper creates discrete element analysis model of railway ballast using the discrete element method, the numerical simulations are carried out to study the mesomechanics of railway ballast during tamping process. We focus on the change of railway ballast compactness and stone ballast interaction force during tamping process. The present study can be helpful for the analysis of the internal mechanism of ballast compaction during tamping process.

Abstract: A three-phase mesomechanics model was established to simulate the aggregate, cement mortar and the interface between them. In order to reflect the meso characters and heterogeneity of concrete, the parameters were randomly valued on the Weibull distribution. Then, by using this model the complete process of concrete crack propagation was analyzed based on the elastic brittle damage theory. This method was verified by simulation of uniaxial tension and three-point bend beam test. Finally, concrete structure cracking at early age during a cold snap was simulated under different surface insulation conditions. The results show that this method can simulate the crack initiation and propagation effectively and reflect the whole process of concrete crack under temperature load.

Abstract: A viscoplastic self consistent model was developed using a rate sensitive constitutive relation, isotropic hardening law, and considering the interaction between the grains and their surroundings. The model was applied to simulate the mesoscopic responses of fcc polycrystalline aggregate during tensile deformation. The macro textures, the grain rotation behaviors, plastic strain and stress heterogeneities, and slip system activities were investigated. The model successfully predicts the typical tensile textures, the grain rotations toward (111) and (100) directions and the orientation dependent slip activities, etc. The simulation results are qualitatively in agreement with experimental measurements and theoretical predictions.