ROPE DEFORMATION AS THE CAUSE OF FATIGUE IN RUNNING ROPES

Summary

The fatigue behaviour of running fibre ropes has not yet been fully clarified and therefore reliable discard criteria are still under discussion. The advantages of polymeric fibre ropes compared to classic steel ropes can therefore not be fully exploited and the application of running fibre ropes in practice is therefore still limited.

In their paper, the authors show that fibre ropes deform in general viscoelastic. Under a cyclic long-term mechanical load, a fibre rope undergoes irreversible viscous and time-dependent deformation and subsequently viscous strains are generated that accumulate. An increase in temperature at constant load accelerates the strain evolution. If the locally accumulated, permanent elongation exceeds a critical value, the fibres and thus finally the complete rope fail. The mechanically induced fibre rope failure occurs in the local area of the highest equivalent stress. The present approach is theoretically justified and experimentally verified.

Keywords:     fibre rope, fatigue, discard criteria, deformation behaviour, service life, polymer fibre, viscoelasticity, creep

Author(s): A. Frick, W. Frick, R. Schulz