Analysis of the critical crack size and operational factors in tensile armors of flexible pipes.

Resumo

Oil & Gas companies have been looking for new hydrocarbon deposits in deep and ultradeep waters.
However, this scenario has shown numerous challenges related to exploiting these natural resources, forcing the
offshore industry to invest in new technologies to resist extreme environmental conditions and increase operational
safety. Therefore, understanding how to evaluate crack behavior in offshore structures is essential as it helps predict
the equipment’s service life, reduces the cost related to inspecting, and avoids accidents. Hence, this work studies
crack propagation in tensile armors of flexible pipes considering corrosive environments. The cross-section of the
analyzed tensile armors was assumed to be rectangular, and the nonlinear material response was represented with
the Ramberg-Osgood model. Finally, two-dimensional (plane-stress) finite element (FE) models were constructed
to evaluate the effect of cracks in these armors. The FE models estimated the energy release rate (J−integral)
and stress intensity factor (KI ) when cracked armors were under operational loadings. The BS7910 standard’s
equations calculated the fracture parameters as well. Then, the responses obtained with both models helped to
elaborate on the failure assessment diagram (FAD) level 1. These analyses allowed an understanding of the wire’s
capacity for several crack sizes and operational loadings.