Research On Micromechanics Visual Parameters Modeling And A Innovative Extended Finite Element Method

The research of the thesis is divided into two parts. In the first part, micro-scale mechanics unitcells are established automatically via the customization of Abaqus pre-processing module. In thesecond part, an innovative extended finite element method (XFEM) is introduced. It has beenimplemented based on the user subroutine of Abaqus software of UEL and employed to simulate theprocess of micro cracks propagation in heterogeneous material.In the first part：1. Based on translational symmetry of micro-scale mechanics unit cell, a set of periodicboundary conditions for the unit cells of rectangular, hexagonal and face centered cubic, etc. arederived. These boundary conditions can be used for various the loads, e. g. force applying, thermalexpansion and heat conduction. Then the symmetry of central reflection is used to reduce the size ofunit cell. The periodic boundary condition of the halved unit cell is established and the calculationtime could be effectively cut down for this cell.2. Based on the derived periodic boundary conditions, a program to automatically establishmicro-scale unit cell and calculate effective material properties is developed via Python language andscript interface of Abaqus. This program is employed to calculate the equivalent elastic constants,thermal expansion coefficient and thermal conductivity of fiber reinforced composite materials,particle reinforced composite materials and porous composite materials with various shape of unitcells.In the second part：3. An innovative XFEM is developed which is based on the methods of substructure and elementlocal partition. By discretizing the element which containing crack tip or separated by a crack, the ofcracks propagation is simulated. This new XFEM has been realized via the user element subroutine(UEL) in Abaqus.4. The XFEM developed in this thesis were employed to analysis the cracks extension inhomogeneous material and in the interface of Bi-materials to verify its accuracy. Further, it is used tosimulate the crack propagation in heterogeneous material. The result proves its adaptability to dealwith complex fracture process.