Comparative Research on Failure Mechanisms of Steel Wire Ropes during Bending Fatigue under Constant and Variable Loads

In order to comparatively reveal fracture mechanisms and wear evolution characteristics of steel wire ropes during bending fatigue under constant and variable loads, the self-made bending fatigue test rig of steel wire rope was employed to carry out bending fatigue tests of steel wire ropes under constant and variable loads. The statistical method by disassembling strands manually and VW-9000 series high-speed digital micro system were employed to comparatively investigate distributions and number of fractured wires, morphologies of fractures and wear scars at fractures of steel wires, evolutions of wear scar dimensions of unfractured and fractured wires in the rope. The results showed that as compared to bending fatigue of steel wire rope under the constant load, the bending fatigue of steel wire rope under the variable load presented later occurrences of fractured wires, more and fewer fractured wires in the outer layers of core and outer strands, respectively, larger extrusion deformations at fractures of outer layer wires in the core strand, lower ratios of crack propagation zones at fractures of steel wires at various layers in the core strand, overall smaller dimensions of wear scars of steel wires in various layers, and easier discarding of steel wire rope.