Mohammad Mousavion

Grade:  Master

Thesis Title:

Implementation of phase-field method for brittle fracture and its application to porous structures

Year: Sept. 2015- Jan. 2018.

Abstract:

Recently, phase field approaches have gained popularity as a versatile tool for simulating fracture. The purpose of this study to demonstrate the capabilities of the phase field method in crack modeling in porous media. A phase field model for brittle fracture is implemented in the commercial finite element softwar Abaqus by means of User Element Subroutine (UEL). This is accomplished by replacing the sharp discontinuities with scalar damage phase field parameter representing the diffuse crack topology. The phase field is a scalar variable between 0 and 1 which connects brocken and unbroken regions. Thus, if its value reaches one the material is fully brocken. This approach does not need predefined cracks and it can simulate curvilinear fracture path. Simulations of brittle fracture with phase field method involves the displacement field and the phase field of crack. Also the elastic displacement field and phase field of crack are solved separately is a staggered solution. To implement the solution in Abaqus two element type are used in a layered manner. Each layer used the same nodes but different degree of freedom (DOF). In general, the results of the analysis indicate that the phase field method is able to predict the growth of crack in geometrically complex structures. Also, according to the simulation results, the critical force to start crack growth suddenly decreases over a specified porosity value and it continuace decrasing with a faster rate by incrasing the porosity.

Keywords: Phase field model, Brittle fracture, Porous structures.