FUNDAMENTAL UNDERSTANDING OF HMPE MOORING ROPE ENDURANCE
The fatigue lifetime of high modulus polyethylene, HMPE, fibres, especially in mooring ropes, is governed by plastic deformation (creep) failure. As such, fatigue life can be predicted with DSM Dyneema’s Performance Model based on the dynamic load condition, temperature, and the time under load. Testing confirms that HMPE fibre types that resist creep deformation result in higher fatigue life.
Investigation of Miner’s damage summation on creep revealed that Miner’s rule is applicable for HMPE. The contribution of varying load periods, and varying temperature periods can be predicted by summation of permanent elongation. The result from these periods determines the final lifetime.
A rope temperature model has been developed based on hysteresis, axial slip and strand-on-strand movement, and validated through testing. Temperature measurements were performed on full sized dynamically loaded vessel mooring ropes. The fundamental understanding of HMPE rope endurance and the models developed enable accurate lifetime predictions for rope designs and their applications.
Author(s): M. Vlasblom, R. Bosman, A. Gualdi and J. Plaia