LOSS OF BREAKING LOAD OF HIGH-STRENGTH WIRES DURING TRANSVERSE PRESSURE

Summary

The results of quasi-static tensile tests and dynamic fatigue tests on high strength rope wires are presented. The results will contribute to a better understanding of wire fatigue failure with the aim of finally being able to describe the fatigue processes in the rope.

When ropes are deflected inside a rope, plastic deformations occur at the crossing points of the wires, resulting in permanent contact ellipses at these points. These are identified as areas of self-induced damage because they represent local plastic strain concentrations. In quasi-static tensile tests on wires with and without contact ellipses, it is shown that the introduced contact ellipse almost does not change the breaking load. Contact ellipses do not represent classic notches, but they do represent defects, because all wires with a contact ellipse break at this point in the tensile test. If the contact ellipse is additionally loaded with a transverse load during the tensile test, the breaking load of the wires drops to about 70%.

The wire failure in the tension-tension test is based on surface flaws and not on the contact ellipse. A notch (surface flaw) under tensile load is obviously more dangerous than the local plastic strain concentration due to contact ellipses.

The influence of a contact ellipse under bending load with additional transverse compression on the wire fatigue failure must be further investigated.

KEY WORDS:

Running ropes / deflection / transverse pressure / wire contact area / contact ellipse / high-strength wire / deformation capacity / fatigue behaviour

Author: W. Frick