Session: 02-09-01 Reliability of Moorings & Risers

Submission Number: 176375

Finite Element Multiaxial Fatigue Assessment of Mooring Chains Under Constant Amplitude Loading 

Mooring chains are critical to the structural reliability of offshore systems. Fatigue in these components is still often assessed using global uniaxial S–N approaches, which do not capture local stress concentrations, multiaxial effects, or the mechanisms and locations of crack initiation. This study presents a finite element–based framework for fatigue life prediction of mooring chains under constant-amplitude tensile loading. Several multiaxial critical-plane criteria are considered to estimate crack-initiation life without prescribing an initial defect.

A distinctive feature of the framework is the calculation and visualisation of fatigue indicator parameter (FIP) distributions across the entire chain link. This enables direct mapping of potential crack-initiation sites and provides a more mechanistic perspective than conventional approaches, which usually report only local stress fields or lifetimes at preselected hotspots.

Validation is undertaken through a controlled experimental campaign on small-scale commercial chains, enabling cyclic testing under different load levels and detailed fracture surface observations. Although performed at reduced scale, the experiments provide essential data for calibration and verification of initiation-based predictions, and allow comparison between FIP distributions and observed crack-initiation zones.

The methodology has the potential to enhance fatigue assessment of chain links by providing full-field FIP distributions derived from local multiaxial criteria. This approach enables identification of likely crack-initiation sites and offers a more mechanistic basis than conventional S–N methods. The framework is scalable to larger chain sizes and provides a foundation for future studies under variable-amplitude loading and more complex service conditions.

Presenting Author: Eguzkiñe Martinez Puente Mondragon Unibertsitatea

Presenting Author Biography: Eguzkiñe Martinez Puente is a PhD candidate at the Fluid Mechanics Research Group of Mondragon Unibertsitatea. Her work focuses on the structural integrity of offshore systems, particularly on fatigue life assessment of mooring lines for marine renewable energy applications. She holds a BSc in Mechanical Engineering (2021) and an MSc in Industrial Engineering (2023) from Mondragon Unibertsitatea. Her doctoral research combines numerical modelling and experimental testing to investigate degradation mechanisms in mooring chains under dynamic marine conditions.

Authors:

Eguzkiñe Martinez Puente Mondragon Unibertsitatea
Iñigo Llavori Mondragon Unibertsitatea
Alaitz Zabala Mondragon Unibertsitatea
Markel Penalba Mondragon Unibertsitatea