Study On Mechanical And Frictional Wear Performance Of Wire Rope Strand

With increasing depth of underground coal mining,a multi-rope structured hoisting device for a deep mine is desired.During the running process of the said hoisting device,there must be a motional dyssynchrony between the wire ropes and a deformation mismatch in the device,resulting in a tension difference between the ropes,and even the device’s abnormal performance and rope breaking.The wire rope’s mechanical and frictional wear performance significantly affects the safe production of the hoisting device.Meanwhile,frictional wear between the ropes and that between the ropes’ wires are inevitable during long term service,resulting in the requirements for scheduled maintenance and replacement that increase the cost significantly.It is reported that,however,most of the ropes for deep mines in our country depend heavily on import,indicating that in-depth studies on the mechanical and frictional wear performance of wire ropes are significant for breaking foreign technology blockades and for realizing an independent development of high performance wire ropes in our country.Supported by the National Key Basic Research Program of China(973)(No.2014CB049403),the present thesis gives a study on the axial extensile,torsional and bending properties as well as the interwire frictional wear performance of single strand wire ropes(in short,wire rope strands),which intends to provide a theoretical reference to the analysis,design and selection of the hoisting ropes in deep mines.The main contents and conclusions of this thesis are as follows:(1)Based on the structural features of spiral triangular strands(STS)and spiral straight strands(SSS),parametric spatial equations for the wires of the strands are derived.With the considerations of the effect of Poisson’s ratio and the elasto-plasticity of the wires,the finite element models of the strands are established and verified through comparisons with reported results.By means of finite element method,the overall mechanical property and the local interwire contact performance of the strands subjected to tensile,torsional and bending loads are comparatively studied.The comparison shows that the tensile,torsional and bending stiffnesses of the STS are larger than the corresponding values of the SSS.The deformation and stress yield of the STS are more obvious than those of the SSS under the axial tension and torsion conditions,which are opposite to the conclusion under the bending condition.Moreover,a contact failure is more likely happen to the STS due to its larger interwire contact pressure,compared with the SSS.(2)A solution model for the interwire helical contact in a simple straight strand is built and numerically solved by the use of conjugate gradient method and fast Fourier transform.Then the coupling model for the axial mechanical property and interwire contact performance of the strand is established by combining the helical contact model and the thin rod theory.Based on the verified coupling model,the effects of the core-wire contact deformation on the axial mechanical property and the interwire contact performance of the strand are analyzed.The present solving procedure has a similar accuracy with the finite element method(FEM),and it is more efficient than the FEM.The results show that the maximum von Mises stress of the wires caused by the core-wire contact occurs at a region beneath the contact interface,where the stress yield is likely to happen.Compared with the results ignoring the core-wire contact deformation,the tensile and torsional stiffnesses of the strand considering the said deformation are smaller.(3)Based on the elastic contact theory,thin rod theory and semi-analytical method,a solution model for the varying interwire contact of a spiral straight strand is proposed and verified through comparisons with reported results.By means of a numerical procedure,the evolution rules of performances for the core-wire contact and wire-wire contact of the strand at varying axial load are studied.Moreover,the effect of the interwire contact status on the axial mechanical property of the strand is discussed.The results show that the axial tension makes the central and outside wires closer,while the axial torsion leads to the approach between adjacent outside wires.The coupled contact status happens to the strand under some certain axial loads,and the distribution of interwire contact load is relatively uniform in this contact status.As the axial loads increase,moreover,the stiffnesses of a large lay angle strand increase obviously.(4)With the consideration of friction and contact deformation,the mechanical model of a spiral straight strand subjected to a bending load is established.Then the friction is automatically solved by means of methods including improved Euler’s predictor-corrector method,which overcomes the shortage of commercial softwares.Based on the verified model,the bending property and the interwire frictional contact performance of the strand are analyzed.The results show that the consideration of the core-wire frictional contact can obtain a larger bending stiffness of the strand compared with a pure bending model.The core-wire friction is zero at the furthest part from the curvature center of the bended strand,where the tensile failure and stress yield are likely to happen.The bending fatigue are liable to happen at the neutral layer.The strand with a large lay angle has a better resistance to bending fatigue but worse frictional wear property,compared with a small lay angle strand.(5)A wear model of a spiral straight strand subjected to a periodic bending load is built.Experiment tests of steel wires are conducted to obtain the wear coefficient and validate the interwire wear model.The evolution of interwire frictional wear law and its effect on the interwire contact performance of the strand are numerically studied.The results show that the interwire wear only happens on the side further from the curvature center of the bended strand than its neutral layer,and the maximum wear depth occurs at the middle position between the neutral layer and the furthest location from the curvature center.As the wear process goes on,the interwire contact area increases while both the contact pressure and contact deformation decrease.A significant stress concentration and local deformation happen at the position furthest from the said curvature center,where the wires are not worn.Moreover,an increment in the lay angle of the strand leads to more severe interwire wear and contact,which may result in dangers such as wire fracture.