Flintstone have developed a new fatigue test rig add-on for their versatile horizontal test rig.

General Fatigue Testing

Flintstone have developed a new fatigue test rig add-on for their versatile horizontal test rig. The fatigue rig set up allows load cycles up to 2700kN and 130mm displacement, making it ideal for tension-tension fatigue testing of:

• Mooring chain segments
• Mooring chain accessories
• Wire Rope

Mooring applications

Crane lines

Guy lines

Fatigue in Marine Applications

Mooring chains and accessories are subject to cyclical loads in the harsh marine environment. Damage, defects, corrosion, wear, out-of-plane bending (OPB), twist, and improper design can all contribute to the causes of mooring line failure. However, material fatigue due to the ever present cyclical loading, more often than not, has a role to play in the downfall of any mooring line.

Stress hotspots are created in a loaded component due to its geometry: steps, notches, corners all create hotspots. Damage, wear and corrosion create all create geometrical anomalies in the loaded component. If these stress hotspots are above the endurance limit, then the damage due to the cyclical load accumulates. If the cyclical load continues then eventually the material will fail, cracks propagating from the stress hotspot site.

S-N Curves (Stress amplitude vs Number of Cycles) describe the fatigue performance of material and components. The S-N curves are usually generated from physical testing and give a good guide to how the material or component will behave.

Therefore, the ability to test components with different fatigue regimes is important for developing new products and introducing new materials for use in mooring applications. Moreover, this type of testing is invaluable for verification of mooring chain sections intended for re-use and/or life extension projects