Investigation of the damage caused by wire contact points and its influence on the safety of running high-strength ropes

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The objective of the research project is to contribute to the clarification of the cause of failure in dynamically loaded (running) wire ropes with different static wire strengths, with special focus on the influence of wire contact points and press ellipses.Currently, in rope technology for running ropes, the rope tension load in comparison with the nominal rope strength is regarded as significant for the fatigue behaviour. This leads to an incorrect estimation of service life, especially in the case of high-strength wire ropes, as shown by the literature and the results of our own preliminary investigations. The current prediction that higher wire strengths lead to an increased rope service life is wrong; in fact, the service life is reduced! This contradiction in the estimation of service life is presumed in the previous neglect of the different deformability of wires of different strengths.In preliminary investigations it could be shown for the individual rope wire that a strain-based consideration of service life can solve the existing problem and provide a reliable, safety-related design. Based on the preliminary tests, we assume that rope failure is also caused by exceeding a critical elongation in the rope wires. In the research project applied for, a new method for determining the formation of damage and rope failure is to be developed. For the development of the method, the approach already used in related sciences, namely that component failure is limited by a maximum tolerable plastic deformation, is to be used. This means that the plastic strain accumulated during component operation, including previous deformations, determines the damage development and finally the service life. The solution approach of the planned research project is that indications of the service life of ropes of different strengths can be obtained from their relative stress-strain curves in tensile tests until breakage. The aim is to prove the influence of the plastic deformation of wires of different strengths on the service life of a rope manufactured from them. Special attention is focused on the formation and effect of contact points and press ellipses on the fatigue behaviour of ropes. This novel research approach will be investigated and validated.