ABSTRACT
This paper describes the newly-developed damage-based fatigue life model for the long-term reliability assessment of the drawn steel wires and the wire ropes. The methodology is based on the computed local stress field in the critical trellis contact zone of a stranded wire rope by the FE simulation and the degradation of the Young’s modulus of the drawn steel wires. The fatigue damage model is based on Lemitaire’s damage equations for quasi-brittle material with a damageable microinclusion embedded in an elastic mesoelement. The incremental fatigue damage calculations employing the load-cycle block is described. The routine is integrated into commercially available Finite Element Analysis (FEA) software. A case study using a single strand (1 × 7) steel wire rope with 5.43 mm-dia. drawn wires is employed to illustrate the damage-based fatigue life prediction procedures. The simulated tensile fatigue cycles consist of the load range of 145 kN and load ratio, R = 0.1. The peak applied load corresponds to 50% of the maximum breaking load of the steel wire rope. The FE-calculated results indicate that the von Mises stress, maximum principal stress and the contact pressure cycle in-phase, and with an identical stress ratio as the applied axial load. The trellis contact point is relatively small and experiences elastic stresses, thus the fatigue damage prediction for the fretting fatigue condition is appropriate. The damage initiation life at the trellis contact along the core wire is calculated at N o = 1050 cycles. An additional and improved data set of the damage model parameters of the drawn steel wires is required to achieve an accurate and validated life prediction model of the wire ropes.
