A Comprehensive Set of Round-Bar Stress Intensity Factor Solutions for ECA of Mooring Shackle and Chain Components

摘要

Engineering Critical Assessment (ECA) has become essential for establishing if a mooring line in service is fit for continued service when low fracture toughness in some components is suspected or inspection results may suggest possible presence of discontinuities. Existing ECA codes and standards such as BS 7910 has rather limited stress intensity factor (K) solutions suitable for this type of applications, e.g., elliptical crack stress intensity factor solutions valid for a short crack regime with a/D ratio far less than 0.1 with different aspect ratios other than a/b =1. Here, D refers round bar diameter and a crack depth (minor axis) and b crack half length (major axis). As a result of a recent joint industry project (JIP), referred to as Mooring Component Assessment (MCA), a comprehensive set of K solutions have been developed for covering crack size a/D from 0.005 to 0.15 which associated with existing K solutions allows to cover a/D from 0.05 to 0.6, along a unified treatment of local stress gradients, e.g., at knuckle positions, for supporting ECA of mooring components and chain links. These K solutions are presented in a set of simple parametric forms and can be readily used for ECA assessment of shackle and chain-link components.