Studying On Voronoi Cell Finite Element Model For Damage Evolution In Porous Materials

Because of their special structure and shape,porous materials have been widely used in industrial production and attract many researchers' interest.Porous media are active in biological science,energy development,electrical materials,aerospace,and other fields,which even opens up a new way for some fields.In addition,more potential applications need to be developed.However,due to the complexity of its structure,it brings great difficulties to the analysis of the problem,especially in the calculation scale.As one of the means to solve problems,computational mechanics inevitably needs to overcome these problems and lay a foundation for other disciplines.This dissertation deals with the damage evolution in porous materials using Voronoi Cell Finite Element Method(VCFEM).The main contributions can be listed as follows:1.Two new elements based on Voronoi cell finite element(VCFEM)model are developed for fracture simulation of material containing massive holes under inner pressure.One is the element with crack initiating from edge of the inner hole.The other one is the element with crack initiating from the edge of cell which generates when cracks extend from adjacent cells.In addition,analytical solution of stress components near crack tip is added to stress function applying to complementary energy functional.When the number of the holes is over a hundred thousand,the ordinary finite element needs about hundreds of millions of meshes which are solved impossibly.However,there is the characteristic of keeping the number of grids with hole number in new Voronoi cell which makes large scale simulation possible.Also grids number in VCFEM remains constant while the number in ordinary element increases greatly with cracks.The results for a large number of numerical experiments which are to calculate stress intensity factor(SIF)have demonstrated that the present models have high precision and capture stress intensity accurately.2.A remeshing algorithm is proposed to simulate the damage evolution of porous materials.Various morphologies of crack initiation and propagation in the element are described in detail.The validity of the re-meshing program for damage evolution is demonstrated by an extended numerical example.It is also proved that the two typical elements proposed in this paper play an important role in extending the simulation.In present dissertation,two kinds of damaged Voronoi elements are analyzed and validated in detail by a large number of examples,including the effect of crack length,angle and pressure within the hole on stress intensity factor,to prove the effectiveness of the element.On this basis,the damage evolution process of porous materials is studied by using the proposed mesh re-partitioning algorithm.For porous materials,the damage research of this complex structure with large-scale voids has established a corresponding procedure.It also contributes to the progress of hybrid finite element method.