Bending fatigue of wire ropes under torsion

The lifetime of running wire ropes can be affected by various loads. The basic loads which occur are the tensile force and the bending load. The bending fa~gue with these two loads has been thoroughly investigated and the results of these investigations are known and calculable. Torsion as a third load , caused by twisting of the rope, can easily occur; however the impact of this combined load on the lifetime of the wire rope has long been unclear. An extensive research project was funded by the German Research Foundation (DFG) and carried out at the University of Stuttgart in order to describe the impact of a combined load consisting of tensile, bending and torsional load on the lifetime of wire ropes. As one result of this project it is now possible to calculate the lifetime under consideration of twist. For a safe use of wire ropes, one discard criterion should appear at an appropriate time before rope failure. For that reason the behaviour of ropes, under torsion as a third load , regarding the number of wire breaks and other abnormali~es was also considered within the scope of the research project. The research project in detail as well as the results and findings are presented in [1). This paper gives an overview of the project, the theoretical fundamentals and the experimental results as well as the conclusions, which are described in detail in [1).