Effect Of Impaired Surface Quality On Bending Fatigue Characteristics Of Wire Rope

Bending fatigue characteristics of wire rope are influenced by impaired surfacequality. And impaired surface quality is one of the main causes of failure of steel wirerope. It is necessary for designers to know the effect of impaired surface quality onbending fatigue behavior, laws of failure and mechanisms of failure.In this paper, the effect of impaired surface quality on bending fatigue behaviorof wire rope was studied by eyeballing and nondestructive quantitative detection on aself-made bending fatigue test platform combined with SEM, optical microscopy andother instruments, including investigating the effect of damage forms, cycle ofbending fatigue on breaks, damage value, fatigue life.At the same time, the staticanalysis and fatigue life prediction of impaired surface quality of1×7IWS ropebending on nylon pulley. And the simulation results were compared with the testresults. The results of the study show that:(1) The mechanical properties of the wire rope were affected by surface breaks.And the wire steels of the adjacent side were changed by surface breaks under highstress. Broken wires and the wear loss amount appear on the twist of surface breaks.The growth rate of surface breaks increases faster. But the fatigue life of wire ropes isreduced. The sum damage value of wire rope is lower because of the decreasedfatigue life. When the rope was abandoned by manual inspection, the limit damagevalue of wire rope was not reached by defectoscope.(2) The effective bearing cross-sectional area of the wire rope was reduced bysurface wear. The stress concentration was produced by surface wear. Broken wiresappeared on the twist of surface wear. And the rope was abandoned by manualinspection. The mechanism of wire fracture on surface wear was wear damage andfatigue fracture. Defects on the surface were easy to form a source of fatigue whichwas lead to the final fracture. Fretting wear was existed inside of wire rope.(3) The substrate materials of steel wire were severely degraded by surfacecorrosion. And the corrosion pits were appeared on the surface. Broken wires and themax damage value were concentrated in the corrosion area. But the wire rope wasabandoned by manual inspection. The mechanism of wire fracture was crack initiationof anodic dissolution. In the interaction between corrosion and fatigue, corrosion pitswere formed on the surface of wire steel, resulting the final broken wires rope. Thefracture surface crack area was subject to cleavage fracture. And the micro porous onthe surface was detected. (4) The results of simulation analysis show that: the maximum equivalent stressof impaired surface quality of wire ropes was increased by the depth of the surfacedamage. And the amount of deformation of the adjacent strands was increased by thesurface wear. In the role of fatigue loads, the predicted value of fatigue life on thesurface wear was poor. And fatigue life was decreased rapidly with the increasingdepth of wear. Fatigue life and stress ratio was positively correlated in the same loads.Fatigue life was increased with the increasing stress ratio.