Study On Fatigue Performance And Bearing Capacity Of Hoisting Wire Rope In Mechanical Stereo Garage

Following with the sustainable growth of vehicle holdings,the parking problem in cities is becoming increasingly severe.Mechanical stereo garage has been gradually promoted by its advantage of significantly improving the utilization rate of the effective garage area.The wire rope has good tensile performance and bending flexibility,which is widely used in the hoisting mechanism of mechanical stereo garage.The service condition of wire rope is complex.It is easy to cause contact fatigue,bending fatigue and other failure phenomena of hoisting wire rope under long-term cyclic alternating tensile and bending loads.In addition,minor defect inside the rope occur easily in the manufacturing process of wire rope,which gradually increases with the wire drawing process,and then affects the fatigue property of the wire rope.In the long term service,regular maintenance and replacement of hoisting wire rope are needed,which requires a large amount of capital investment.Therefore,in order to maintain the safe and stable operation of the hoisting mechanism of mechanical stereo garage and protect the safety of property and life,it is of great significance to carry out the study on the contact,bending fatigue and bearing characteristics of the hoisting wire rope and to deeply analyze the influence law of internal defects on the service performance of the hoisting wire rope.This study was supported by the Science and Technology Research Program of Chongqing Municipal Education Commission-Study on Safety Service Performance of Mechanical Stereo Garage Hoisting Mechanism(No.KJQN201800722).The influence of contact,bending fatigue performance and internal defect on the fatigue performance and bearing capacity of the single-strand hoisting wire rope was studied,attempting to provide a useful reference for the theoretical analysis and design of the hoisting wire rope.The main research content and result are as follows:(1)The finite element analysis model of tensile fatigue performance of hoisting wire rope was established.The high-precision meshing method of the helical contact area in the internal space and the constraint scheme of the end face of the rope were proposed.The problem of end effect commonly existed in the simulation of the rope was solved.Moreover,the influences of the fatigue performance,geometric parameters and material parameters of hoisting wire rope on the tensile fatigue performance were analyzed.The results showed that obvious stress concentration occurred in the core-side wire contact line area of hoisting wire rope,where was the most prone to fatigue life attenuation or even destruction due to the larger stress amplitude,which reduced the bearing capacity of hoisting wire rope.The fatigue life sensitive area of the core wire was distributed in a spatial spiral band.In order to improve the fatigue life of the hoisting wire rope,the diameter and lay angle of the side wire should be appropriately reduced,and material with smaller Elastic Modulus and larger Poisson’s ratio should be selected for the rope in the core-side wire contact state.(2)Based on characteristics of constant amplitude cyclic load,the finite element analysis model of bending fatigue performance of hoisting wire rope was established,and then the bending fatigue life of the rope was analyzed with the consideration of the effects of average stress and elastoplasticity on bending fatigue performance of hoisting wire rope.The effects of material parameters and geometric parameters on bending fatigue and bearing characteristics of hoisting wire rope were discussed.It was found that the bending fatigue life of hoisting wire rope has obvious layered distribution characteristics,and the region near the bending plane has a higher fatigue life.Hence,the fatigue life of hoisting wire rope with smaller yield stress can be effectively improved,and the wire rope material with appropriate Elastic Modulus is selected based on the size of bending load.(3)Considering the effects of average stress and elastoplasticity on fatigue performance,the finite element analysis model of tensile fatigue performance of defective hoisting wire rope was established by local stress-strain method.ICEM CFD software was used to complete the mesh division of the defective hoisting wire rope,and the hexahedral mesh with higher solving efficiency and precision was used to encrypt the defect area.It was found that fatigue damage was more likely to occur in the internal defect area of the defective wire rope.Reducing the axial bearing capacity of the hoisting wire rope was beneficial to reduce the stress-strain peak value in the internal defect area of the wire,thus increasing the fatigue life of the hoisting wire rope.Moreover,the rotation angle of the defect has a great influence on the distribution characteristics of the fatigue life of the core wire.The smaller the angle formed by the longer equatorial radius of the defect and the axis of the core wire was,the better the axial bearing capacity and fatigue life of the hoisting wire rope would be.(4)The finite element analysis model of bending fatigue performance of defective hoisting wire rope was established.Through numerical solution,it was found that the bearing capacity of the defective hoisting wire rope was negatively correlated with the peak stress,and its minimum fatigue life occurred near the surface of the defect area.The fatigue life of the defective hoisting wire rope along the whole axial path was greater than that of the non-defective one.In addition,the peak value of fatigue life in the defect area increased locally,and the minimum fatigue life reduced at the same time,which made the fatigue failure of the core wire occurred earlier.The larger the maximum von Mises stress increase rate of the defective hoisting wire rope was,the smaller the bearing capacity of the defective hoisting wire rope was,and the bending fatigue failure of the hoisting wire rope was more likely to occur.