Determination of the Donandt Force of rotation resistant wire ropes under dynamic working conditions

The endurance of running ropes decreases steadily, being bent over sheaves with increasing tension and finally drops rapidly when exceeding the yield limit of the wires. The corresponding force is called the Donandt Force and was determined within the scope of an AIF1-funded research project (supported by Drahtseil- Vereinigung e.V Germany) with help of bending over sheave tests (BOS Test) on ropes in their original state [1]. It indicates the transition from fatigue fracture to forced rupture and therefore represents the limit to which the endurance of the rope can be calculated. With the help of regression analysis, the constants for the calculation of endurance and Donandt Force were determined. The experiments show that especially at high loads near the Donandt Force the correct number of bending cycles for discard based on external wire breaks is difficult to recognize. The destruction of the rope already starts invisibly inside the rope after a few bending cycles. Beginning with the formation of deep notches caused by transverse pressure, wire breaks occur at the intersection of the outer layers of strands and the following layer, and often lead to a rapid failure of wires in the interior rope. 1AiF: Arbeitsgemeinschaft industrieller Forschungsvereinigungen “Otto von Guericke” e.V. (Industrial Cooperative Research Associations)

Author(s): O. Reinelt, S. Winter and K.-H. Wehking