Damage mechanisms in synthetic fibre ropes

Synthetic fibre ropes are widely used in applications involving frequent deployment and movement by personnel, for example ship mooring lines, tug lines, etc. However, where large ropes run continuously at high tensions over sheaves, such as elevators and cranes, the use of synthetic fibre rope has not found wide use because of relatively poor fatigue life. Damage mechanisms in synthetic fibre ropes are reviewed and compared with steel wire rope where possible. As with steel wire ropes, excess heat generated during cyclic bending over sheaves can decrease the life of synthetic fibre ropes. However, the onset of degradation in polymer fibres can begin at much lower temperatures, as low as 60°C. Therefore particular attention is paid to mechanisms that contribute to heating, for example hysteresis caused by fluctuating loading, and sliding friction caused by fibres movement during bending. Methods to reduce frictional heating are discussed. Models are presented for scaling small-rope experimental data to predict large-rope fatigue life.

Author: F. Sloan