Study On The Influence Of Corrosion Pit On Mechanical Properties Of Braided Wire Rope

As an important traction member in the tension wire-laying project,the quality of the braided wire rope not only has a direct impact on the smooth construction of the wireline,but also relates to the safety of the wireline construction personnel.During the service of braided wire rope,the outer side wire of the strand is susceptible to environmental damage and corrosion damage,which is mainly caused by the occurrence of corrosion pits on the surface of the steel wire,which leads to the decline of the mechanical properties of the steel wire.Furthermore,it affects the mechanical properties of the braided wire rope.In this paper,the YS9-8×19 galvanized braided wire rope for traction construction is taken as the research object,The corrosion characteristics and mechanical properties of the braided wire rope were studied by electrochemical corrosion test,immersion corrosion test,Detection of surface corrosion pits on the outer side,numerical simulation and tensile breaking test.The main research contents are as follows:(1)The corrosion causes of traction braided wire ropes were analyzed and the corrosion mechanism was discussed.The effects of three single factors of Cl~-concentration,temperature and pH on the corrosion rate of steel wire rope substrate and its surface galvanized layer were investigated by electrochemical test.The relationship between corrosion rate and three single factors was established.Based on the response surface methodology,the effects of the interaction of Cl~-concentration,temperature and pH on the corrosion rate of the steel wire rope substrate and its surface galvanized layer were studied.The relationship between corrosion rate and the interaction of three factors was established.The results show that the concentration of Cl~-,temperature and pH will affect the corrosion rate of the steel wire rope substrate and its surface galvanized layer,and there are obvious interactions between the three influencing factors.(2)The shape and depth of the corrosion pit on the outer surface of the braided wire strand were measured after soaking and corrosion,and the influence of the immersion corrosion time on the surface corrosion of the outer layer side wire was studied.The results show that there are mainly craters of semi-spherical and semi-ellipsoidal shapes on the surface of the outer side of the corrosion,and the maximum corrosion pit depth increases with the immersion corrosion time(corrosion degree).(3)The corrosion pit morphology on the outer side wire surface is simplified,and the spatial geometric model of the braided wire rope with different corrosion degrees is established.The explicit dynamics algorithm is used to numerically simulate the size and distribution of the equivalent stress inside the corrosion pit of different braided wire ropes under different applied tensile forces.The simulation results show that stress concentration occurs inside the corrosion pit,and the maximum equivalent stress appears inside the corrosion pit.The maximum equivalent stress is less affected by the shape of the corrosion pit and is affected by the applied tension and corrosion pit depth.(4)The tensile breaking test was carried out on the braided wire ropes with no corrosion and different corrosion degrees.The influence of corrosion degree on the tensile mechanical properties of the braided wire rope was further explored,and the influence law of the maximum corrosion pit depth on the breaking force of the steel wire rope was obtained.The tensile fracture morphology was observed and the fracture properties of the corroded braided wire rope were analyzed.It further shows the influence of stress concentration inside the corrosion pit on the tensile mechanical properties of the steel wire rope.The validity of the geometric modeling and simulation results of the corrosion pit is verified,which has important guiding significance for the life prediction research of the corrosion of the steel wire rope.