A NEW INNOVATIVE APPROACH TO DETERMINE THE TOTAL AMOUNT OF BENDING CYCLES FOR WIRE ROPES UNTIL FATIGUE – INTRODUCED IN REVISED ISO 16625 – ENABLED BY CONCEPT CHEMNITZ

Summary

Since the early 2000s efforts have been made to introduce a new way to calculate the lifetime for a rope in rope drives, implemented in EN 13001-3-2:2014. This elaborated standard uses a cycle-based approach instead of a time-based approach, previously well-established for many years in DIN 15020-1 for example. Since its introduction, many discussions arose towards the cycle-based approach, especially regarding safety and multilayer spooling. This article will also show which wrong assumptions in EN 13001-3-2 lead to the controverse.

In 2015, a standardisation project was launched to revise ISO 16625:2013 Cranes and hoists – Selection of wire ropes, drums and sheaves, establishing a dedicated working group comprised of experts from various crane and hoist manufacturers, rope manufacturers, and scientists from universities. As the group sought to determine the scope and objectives of this endeavour, EN 13001-3-2 was used as a starting point. The evaluation of EN 13001-3-2, particularly its major shortcomings, provided crucial motivation to examine both the method Stuttgart and the method Leipzig, as well as the scientific findings associated with these approaches.

Consequently, an innovative framework was proposed to reframe ISO 16625, aiming to overcome known limitations and fulfil the project’s objectives. The revised edition of ISO 16625 is set to comprise a cycle-based methodology, with proofs of competence based on the limit state method for both fatigue strength and static strength, and in addition addressing multilayer spooling. Furthermore, the standard will cover various facets of running and stationary ropes. Central to this new approach is a mathematical model for all fatigue investigations, named by the author “Concept Chemnitz”. The concept can be used to simplify any kind of lifetime or fatigue evaluation for any steel based specimens or design details with a specific geometry under cyclic or alternating load or stress where the slope of the Wöhler-lines are changing because of notch effects.– To verify the fatigue strength of running steel wire ropes over sheaves, Concept Chemnitz utilizes a new reference point with characteristic values to determine the total amount of bending cycles for wire ropes until fatigue. This reference point serves as the basis for defining S-N curves across different D/d ratios, providing a less complex and scientifically validated foundation for rope design and safety assessment.

Author: M. Golder