The Study Of Finite Element Method Of Film Fracture In The Film-substrate System

The thin film-substrate system refers to a composite material which condenses or deposits some thickness on the surface of a substrate.It has become one of the most effective ways to improve material or structural performance.Due to the film is prone to fracture in the process of use,even if the material or the structure has not yet reached the destruction of stress,and even much less than the destruction of stress,the material or the structure has a destabilizing failure.Therefore the study of film fracture has theoretical and engineering significance.The finite element method has made a new opportunity to study the film fracture.The finite element software was used to simulate the process of film fracture,which was resonated by the researchers.The extended finite element method(XFEM)is an extension method of traditional finite element method based on element division.It uses a special displacement function and uses extended degrees of freedom to describe discontinuities,so it is no longer necessary to re-partition the mesh to satisfy the geometric discontinuity.The purpose of this paper is to use the extended finite element method to simulate the uniform arrangement of channel crack of the film through the ABAQUS finite element platform.The analysis result and the proposed model of channel crack of film were mutually verified.Meanwhile,the validity of model during the unloading phase has been vertified by the stress-strain curve obtained by simulating the presupposed channel crack.The following aspects are introduced and analyzed:(1)The thin film substrate system is briefly introduced,and the research methods of the film fracture at home and abroad are summarized.(2)The basic principle of fracture mechanics and the basic theory of extended finite element method are introduced and summarized.(3)A model of film fracture in thin film-substrate system is proposed,which is a series of parallel thin film-substrate systems connected with the substrate.Meanwhile the stress-strain curves of loading and unloading are given and the formula of elastic modulus of the film-substrate system is deduced before and after fracture.(4)The modeling process based on the platform of ABAQUS is described.The film fracture of thin film-substrate systems is simulated,and the simulation results areanalyzed.The related curves are plotted by means of Origin to analyze the crack initiation,propagation and penetration,and to verify the validity of the model.The presupposed channel crack is simulated to verify the validity of the model during unloaded process.There are some conclusion:Using the finite element method and taking tolerance error as the disturbance condition realize the numerical simulation of the film fracture in thin film-substrate systems.The stress-strain curve of the thin film-substrate does not reflect the crack initiation,propagation and penetration,but the first derivative and the second derivative curves can be clearly reflected.The channel crack must be accompanied with the occurrence of spalling phenomenon.The finite element platform can be used to justify the proposed channel crack model.The larger the crack number is,the more errors introduced into the model.The smaller the crack-segment length ratio is,the more accurate the model predicts.