On the origin of lifetime extension for HMPE ropes in bending operations

Cyclic bending over sheave fatigue tests on braided ropes of high modulus polyethylene fibers were carried out for developing a better understanding of their failure. Damage accumulation at strand cross-over locations was identified as the main failure mechanism. At these locations, strands repetitively bend and slide over each other under high contact pressure. The application of a DSM proprietary finish termed XBO markedly improved the braid lifetime. This is attributed to the friction and adhesion lowering properties of the finish. The damage accumulation process in the filaments was studied in more detail in a filament friction test. This test showed that the filament gets damaged gradually over its whole volume and not only close to the contact surface.