Chains combined with rope are used for mooring FPSO (Floating, Production, Storage and Offloading) and other floating structures. Their purpose is to keep in place these structures when they are subjected to wave and wind motions.
Oil and Gas companies need more confidence in the reliability of their mooring chains. Complex aspects like the residual stresses generated during the manufacturing process or the combination of different load modes are not included in the standards. Publications in the literature suggest that the residual stress field generated during the manufacturing process of a chain should be taken into account for Fatigue life analysis.
In this research FEA (Finite Element Analysis) is employed for obtaining simplified formulas or charts that will enable mooring engineers to consider the residual field resulting from the manufacturing process in their mooring designs without employing complex FEA.
The main steps of the manufacturing process are: Bending, Welding, Heat Treatment (Quenching and Tempering) and Proof Loading. Stress and Thermal analysis will be performed in order to predict the residual stress field. The results obtained through numerical analysis will be compared to experimental measurements performed with X-Ray Diffraction.