Research On Cracking Algorithm Of Plane Problem Based On Specified Stress

Finite element method can transform the actual physical model into a mathematical model and is simplified to a certain extent.In this method,the infinite unknown quantity is replaced by a finite mathematical model.The higher the accuracy of the model,the closer the calculation result is to the actual solution.In recent years,with the development of computer technology,the finite element method has been widely used in various scientific fields from the initial field of structural engineering analysis.Cracks have a great impact on safety in materials and structures.Cracks will lead to the invalidation of the whole material or structure,leading to major engineering accidents.In order to accurately analyze the crack,the analysis and calculation must be based on the theory of finite element method.About crack simulation software and methods,a variety of mature and effective software and applicable methods have been invented,but each method has its applicability and shortcomings,so far there is no unified calculation method for all cases.Therefore,this thesis introduces a new method:based on finite element method of the the designated stress,the crack simulation analysis is carried out.According to this principle,this thesis proposes the designated stress method to simulate the crack.With the inelastic strain at the integral point introduced as the stress adjustment parameter,the stress at the integral point is adjusted to zero to simulate the cracking process.In order to use the new method to simulate the crack,it is necessary to use the mature software to simulate the crack.One is to get familiar with the specific location and propagation trend of the crack in the structure,the other is to extract the data,in order to compare it with the data of the new method.In this thesis,based on ABAQUS,XFEM and Cohesive methods are used for crack simulation and comparative analysis of the results,and the characteristics of crack simulation methods in ABAQUS are summarized.The specified stress method establishes the variational principle and virtual work equation with displacement and unknown inelastic strain as degrees of freedom,and obtains the equilibrium equation and other finite element formulations of the specified stress element method for plane stress problems.The derived formula is written as C++algorithm program,which is packaged with the basic finite element algorithm program.The finite element software ECSYS,which can simulate the initial crack and crack propagation,is written by simulating the crack surface stress at Gauss integral point to be zero.In order to verify the accuracy and feasibility of ECSYS,the crack simulation results of ECSYS and ABAQUS are comparatively analyzed,and the characteristics of crack simulation with specified stress method are summarized.