Estimating Fatigue Life of Wire Rope with Stochastic Approach

We propose a new method of estimating the fatigue life of wire ropes of elevator. It is based on the assumption that the life of wire rope is determined by the fretting fatigue life of wires. Estimates done on a sample wire rope with the method were in good agreement with the experimental results. The method of estimation involves four steps. First, we did a finite element analysis and estimated the pressure between the wires. To take into account the behavior of the whole wire rope and each wire in the stress analysis, we did a zooming analysis. Second, we conducted a fretting fatigue test on the wires to construct a fretting fatigue database for them. Third, we estimated the life of each wire derived from the pressures between the wires and the fretting fatigue database. Last, we estimated the life of the wire ropes derived from the life of individual wires. The rope life estimated with our new method revealed some important findings. We found that : (1) the inner wires broke earlier than the outer wires and : (2) the residual strength of the wire ropes decreased rapidly after their strength became lower than 80% of their initial strength.