Fatigue Crack Rrowth Simulation Using xEtended Finite Element Method

Abstract

Fatigue crack growth analysis of offshore structure is concerned by the industry because it?s economical and practical to increasing the usage life of the strucutre by extend it?s fatigue life. S-N approachs are the most common way of predicting the fatigue life now. As it is based on test, experiment, and statistical measurements, it will be invalid after a crack has initiated, after which the cracked part has to be replaced or repaired. These operations need time and budget. So the damage tolerant approaches are useful for this situation. Due to some limitation of S-N approaches, a new way of modeling the fracture mechanics is developed-the extended finite element method. Crack can be modeled independent of the mesh within XFEM framework and it allows simulation of crack initiation/propagation along an arbitrary path without the requirement of remeshing. The cohesive segment approach and VCCT approach is associated with XFEM. Also fatigue criterion can be applied for fatigue crack propagation simulation.In this thesis, the concept of XFEM and modeling fatigue crack growth is studied. Some models are made to se the power of modeling with XFEM in Abaqus software. Some parameter study is done to calibrate the element properties. Some concludes and advise of using XFEM for simulation FCG is writen according to the model analysis. At last, a case of crack around a small hole in a pipe wall is simulated with XFEM fatigue analysis. The case is given by Aker Solutions.