Crack analysis of welds. Finite element analysis of fatigue crack growth in the ERW weld of an API 5L Gr.B pipe

      Аннотация: This paper presents a way of modeling the fatigue-generated crack growth in the forging area of the ERW (Electric Resistance Welding) weld process, using the general purpose finite element software ANSYS Static Structural and APDL modules version12.0 applying the strain-life analysis ∆ε/2=σ_f/E (〖2N〗_f )^b+ε_f and the calculation of the Intensity factor KI. The study is focused on the forging area of the weld called FWZ (Forged Weld Zone) of a straight section of 20" API 5L Gr B 20" 6 m linear carbon steel pipe, starting with an induced crack at the top of the FWZ, for design pressure conditions of 1.86 Mpa and a temperature of 43 °C. This methodology integrates information that is scattered in the literature, proposing variants that sometimes exceed what has been published in previous works. The methodology is applied in the three-dimensional and dimensional modeling by means of two load cycles that exceed the design pressure values, obtaining the KI by means of Ansys and the crack propagation velocity by means of the Paris equation da/dN=C(ΔK)^m.

Ключевые слова: API 5L Gr B, electrical resistance welding, mechanical fatigue, deformations, Stresses, Finite Elements