Axial Fatigue of Multilayered Strands

Abstract

Previously reported orthotopic sheet theory is used for obtaining estimates of interwire/interlayer contact stresses throughout realistic pretensioned multilayered structural strands. These data are used in conjunction with axial fatigue data on single wires to develop a theoretical model that predicts axial fatigue life of strands (under constant amplitude cyclic loading) from first principles. The theoretical interlayer slippage over the individual points of contact between cross‐laid layers is addressed, which takes interwire friction into account. The match between the theoretical predictions and experimental fatigue data is very encouraging. Numerical examples suggest that cable axial fatigue life depends on the type of strand construction. The level of mean axial load appears to have a modest effect on the cable stress range versus fatigue life (S‐N) curves. For a given wire material, the endurance limit is found to increase with increasing level of mean axial load, becoming practically constant for mean axial loads greater than 40% of the cable maximum breaking load. Different types of cable construction are found to possess significantly different levels of endurance limit.