Crack growth in the field of residual stresses in welded joints of pipelines used in a cold climate

The problem of the influence of residual welding stresses (RWS) on the process of crack propagation is considered. Finite element modeling of the growth of a semi-elliptical longitudinal crack in the RWS field is performed. To gain a more complete understanding of the process mechanics, the calculation results obtained in view of residual stresses are compared to those obtained without regard for residual stresses. The obtained results are indicative of a significant effect of the level and distribution of RWS on crack propagation. In particular, the complex stress-strain state induced by residual stresses is shown to influence essentially the forming and further growth of cracks located on the inner surface of the pipeline wall. Besides, it is found that the form of crack growth specified by residual welding stresses makes them hard to detect with the application of classical instrumented testing methods. The complex distribution of stresses may cause data corruption and, consequently, difficulties in the correct interpretation of crack shape and size. This, in turn, may significantly complicate planning and performing repair work, and this necessitates the development and use of more accurate diagnostic techniques taking into account the effect of residual stresses. The research results emphasize the importance of taking into account RWS when predicting the behavior of cracks in pipelines and planning their service and repair. Further research in this direction can contribute to creating more reliable and effective techniques for estimating the health of welded joints, this being crucial for the industrial safety and economic efficiency of operating procedures.