Comparison of the results of solving the problem of fracture mechanics for pipe with non-through crack

Dangerous conditions to the pipelines can often be caused by different defects which occur in the pipe walls. Non-through surface cracks attract particular interest. Generally these cracks have com- pound front form - in other words, they are polyvalent. Modern methods of nondestructive inspection do not give complete information on the crack front shape with adequate accuracy. In global practice de- fects are approximated with the semielliptical cracks to simplify calculation methods. In this case the defect is considered two-parameter and it is only defined by maximum depth and length.This paper examines a steel pipe, which has been weakened by the semi-elliptical non-through surface crack. The crack is common to the external pipe area and has longitudinal orientation. The pipe is exposed to internal pressure. Fracture mechanics problem is resolved with ANSYS CAE-system. Stress intensity factor values distribution for the crack front points is under analysis. These values were obtained by using invariant J-integral. J-integral values calculation was performed using integration over a region technique. The obtained results are compared with the data published by other authors. These data resulted from the analysis of pipes and cylindrical pressure vessels weakened by non-through cracks. The results of numerical modelling correlate accurately with the existing solutions. Accuracy of the fracture mechanics problem solution can be significantly increased by using regular mesh with mul- tiple finite elements along to the crack front. Fracture mechanics parameters investigation identified presence of edge effect common to the area where the crack front goes to the pipe surface. Edge effect refers to the local maximum values which are much higher than the crack front end points values. These values should be used while investigating crack propagation under variable loading - that is when pul- sations take place in load condition.