Numerical Analysis of Stress Concentration Factors in Mooring Chain Links Tensioned with and without Geometric Barriers

Resumo

The increasing demand for energy resources, combined with technological advancements, has enabled the exploration of offshore fields at increasingly greater depths. This scenario imposes more severe environmental conditions, requiring continuous improvement of guidelines and standards for mooring analysis and design. Conversely, there has been a significant increase in the number of mooring line incidents over the years. Despite advancements in understanding the behavior of these systems and their relationship with failure events, some gaps still exist. The interaction between the mooring chain links and devices such as chain hawses, mooring chocks, and fairleads - responsible for guiding or restricting the upper end of mooring lines - is often overlooked, and research in this area is limited. This study investigates the influence of contact interaction between mooring chain links and geometric barriers on stress concentration factors. A three-dimensional finite element model is developed using Abaqus to simulate chain links under combined tension, bending, and torque. Results show that the presence of geometric barriers significantly alters the behavior of the links and the locations of critical stress points. Furthermore, the interaction between the links and curved surfaces of different radii significantly influenced the accumulated plastic deformation of the chain links. The study also examines the impact of residual stress fields from proof load testing, demonstrating that their omission leads to notable differences in the results. These findings highlight the importance of accurately representing the real configuration of mooring chain links in numerical models to support more accurate fatigue assessments under actual operating conditions.