Total fatigue behaviour of running ropes

Dynamic stresses of mechanical elements lead to material fatigue. In the past individual fatigue modes for ropes were investigated separately for different stresses. The most detailed investigations have been made for alternating bending stress. Fewer investigations about pulsating tension-tension stress and oscillating torque stress have been made. Fatigue tests on ropes which were stressed by a combination of dynamic stresses have mainly been made for fluctuating bending and tension stress. For this combination of stresses an equivalent single alternating bending stress was used. Fatigue tests with combined stresses have hardly been made. An equation to determine the number of cycles the rope will endure in such cases does not exist. In the following a theoretical model will be presented with which the total fatigue behaviour of running ropes which may be loaded by various dynamic stresses can be described. An equation to model the expected lifetime will be introduced.

Author: U. Briem