Fracture Analysis Of Through-wall Crack To The Steel Pipe

Fracture mechanics is applied widely in the practical engineering along with the theory of fracture mechanics mature as well as the computer technology developed rapidly. At present, it has practical significance that the theory of fracture mechanics is used in the safety assessment of pipes which in service. However, the result of the fracture parameters is can't be used directly to make safe estimation for the structure which has the especial cracks. In this paper, based on fracture mechanics, the straight pipe which contained through-wall cracks are analyzed by the finite element analysis (FEA) method and ANSYS software. Finite element models are established for straight pipe which contain through-wall crack in different situations. They are analyzed and calculated. The stress intensity factor ( K I) which contained the through-wall cracks in different situations in linear-elasticity is calculated, and is transformed to correction coefficient F of stress intensity factor. Fitted method is adopted, and expression of correction coefficient F of stress intensity factor is given. According to the method in this paper, residual strength assessment of pressure-pipes which contained cracks is did. Compared with corresponding papers, the feasibility of this method is expressed.The main contents in this paper include:1 According to the theory of fracture mechanics, the way for solution of plane crack top's stress intensity factor is analyzed and studied; the ANSYS software of finite element analysis is applied to set up plane finite element model;the accuracy and the reliability of modeling as well as the application of the Shell63 unit is confirmed in this paper, and foundation is built stably for later work.2 APDL is applied to write corresponding procedure; models for through-wall crack of straight pipeline in different situations are established by FEA; stress around crack and distribution of strain field under inner- pressure are analyzed, K I in linear-elasticity is calculated.3 The result of the finite element is picked up, charts of K I changing along with the different influence factors are plotted, and rule of change is analyzed and discussed.4 The stress intensity factor shape correction coefficient F is solved further, graphs are drawn up by MATLAB, its change rules are summarized and discussed, the correction coefficient of K I is obtained through non-linear the least square estimation method.5 The residual strength assessment of the pressure pipes which contained the through-wall crack is did initially. Through analyzing and studying, the accuracy of formulas in this paper are confirmed further.