Investigation on influences on the service life of running ropes under reverse bending
Final Report Abstract
It is generally known and taken into account in the relevant literature and also in the corresponding standards that counterbending of a running wire rope leads to significantly higher damage per bending cycle compared to bending in the same direction. Knowledge of the quantitatively existing additional damage due to counterbending is essential for the service life design of the rope drive. Although attempts are often made to avoid counterbending by design, this is very often not possible due to a wide variety of boundary conditions. Furthermore, in none of the methods used so far is the axial distance of the counterbending sufficiently taken into account. Currently, a limiting center distance of e.g. 165d or even 200d is used for the consideration of the counterbending in the rope drive calculation, depending on the literature. For larger center distances, the design is based on bending in the same direction. Well-founded test results for the design of these consideration limits are not known here. Within the scope of the project, no consideration limit could be defined in the investigated range of the axial distance of the counterbending, from which point a counterbending can be considered as bending in the same direction in the service life calculation of a running wire rope. The consideration limits given in the literature have been disproved in the project and must in any case be corrected significantly upwards. According to the theoretical preliminary considerations, counterbending has an increasing influence on service life with decreasing rope force and increasing D/d ratio. Rotation-free rope constructions are more susceptible to additional damage due to counterbending. Non-rotation-free rope constructions tend to experience more uniform loading due to twisting between two successive deflection sheaves and thus less excess damage. The rotation characteristics of a rope between two deflection sheaves do not depend significantly on the center distance of the sheaves and seem to be rather given by the rope construction. Even at very small center distances of 10 x d, no greater additional damage could be detected in the test than at larger center distances. Based on the present test results, it is urgently recommended to take into account an existing counterbending in the rope drive calculation even beyond the previously known consideration limits (>200d) in order to exclude possible safety risks.
Publications
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Impact of reverse bending on the lifetime of running ropes”, OIPEEC Conference – The Hague 2019, ISBN: 978-1-7336004-0-8
S. Hecht
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„Comparison on the impact of reverse bending on the deterioration behaviour of two typical running ropes”, OIPEEC Conference / 7th International Ropedays – Stuttgart – September 2022, ISBN: 978-1-7336004-1-5
S. Hecht
