A NEW METHOD FOR EVALUATING THE SERVICE LIFE OF STEEL WIRE ROPES OF DIFFERENT WIRE STRENGTH

With the two established methods for determining steel rope service life today, incorrect predictions with excessive service life are made for ropes with wire strengths greater than 1960 MPa at the same absolute loading. In reality, the service life may be reduced with increasing wire strength.

The paper shows results of fundamental investigations in tension-tension and rotating bending fatigue tests on rope wires of different nominal strengths to clarify this contradiction in the calculated and the actually achievable service life. The experimentally determined and different service lives of these rope wires under various types of stress are discussed and evaluated together with their material microstructural properties and microhardness. The present results confirm the significant influence of the deformation behaviour of the different rope wires on their fatigue behaviour. It is found, the better the ductility of a rope wire at the same strength is, the better its fatigue endurance.

A promising approach for a comparative evaluation of the deformation behaviour of rope wire seems the comparison of their stress-strain curves as normalised plots. This method allows to compare and predict the fatigue behaviour of two wires interest at the same percentage loading, at least phenomenologically.

Author(s): W. Frick