On the influence of the quasi-static deformation behavior of a wire rope on its fatigue performance

Ropes are load-controlled components and stress safety is considered relevant for service life. However, it is observed that the service life of ropes loaded by tension-tension can increase with increasing mean stress. This observation cannot be explained by the safety concept described above. This means for the author that the fatigue of ropes and consequently their service life is not load controlled. This observation is consistent with the general scientific findings on the fatigue behavior of metals, which states that the applied strain is the decisive parameter with regard to material fatigue. The cause of the mean- stress-dependent fatigue behavior of steel ropes is their nonlinear deformation behavior under load, which means that the rope stiffness is not constant but depends on the applied elongation, i.e. at a comparable higher stress safety a shorter service life might occur. Thus, the author promotes a strain safety concept for service life approach of wire ropes.

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