The influence of twist on tension-tension fatigue of wire ropes Part II
The prediction of the fatigue life of wire ropes which are subject to tension-tension loading (T-T) and twisting due to height-stress is an issue related to ropes suspended over large differences in height. Though terminated non-rotating at both ends, due to its own weight a torsionally active, T-T loaded wire rope undergoes different conditions of twist along its free length (e.g. offshore mooring lines, mine hoisting ropes and ropes in aerial ropeways).
By performing an extensive, systematic research program it became possible to quantify the influence of twist on the T-T fatigue life of two different wire rope constructions and to gain a deeper understanding on the interactions of the failure mechanisms.
This article describes the goals and the contents of the research program. The experimental T-T fatigue test results and findings of microscopic investigations are presented. A new regression approach is shown. The regression coefficients of the investigated rope constructions and a mathematical model to describe the T-T fatigue life as a function of load range, minimum load and twist are presented. The model is validated in a correlation analysis. A calculation tool is described which calculates the tensile forces, rope torque, rotation angles, twist angles and the T-T fatigue life of the rope to be expected in the surrounding conditions.
Author(s): Ernst, B. & Wehking, K.-H.