Study On Tribological And Mechanical Performance Of Lifting Wire Rope Strand

With the increasing depletion of shallow mineral resources,the exploitation and utilization of mineral resources in ultra-deep mines have being become national strategy issues.Wire ropes,as an important part of hoisting equipment,can directly affect the lifting capacity of the hoisting equipment in the process of mineral resources transportation in the ultra-deep mines.Based upon the National Key Basic Research Program of China(No.2014CB049403),the lifting wire ropes are selected as the study object in the present thesis,in which the tribological and mechanical performances of the lifting wire ropes subjected to tensile,torsional and bending loads are studied in detail.Then the associated conclusions are drawn,which are desired to provide a theoretical reference for the design,manufacture and application of the lifting wire ropes in the ultra-deep mines.Firstly,based on the wire rope and contact theories,the rough interwire contact model of the lifting wire rope strand is established,into which the wire surface roughness and Poisson’s ratio effects are incorporated.Simultaneously,the rough interwire contact model is solved with the author’s program code.In doing so,the conjugate gradient method(CGM)and fast Fourier transform method(FFT)are employed to solve the contact pressure and contact deformation.Meanwhile the accuracy and efficiency of the solution are verified.The numerical results demonstrate that both the non-Gaussian and Gaussian rough wire surfaces lead to a fluctuating contact deformation and relatively large contact pressure.For the two rough wire surfaces,decreasing roughness amplitude of the wire surface is helpful to reducing the contact pressure and von Mises stress of the wires.Meanwhile,both increasing the outside wire diameter and the helix angle can improve the load bearing capacity and decrease von Mises stress of the wires.Further,the friction and wear of the bending wire rope strand are studied experimentally with the fixture designed by the author.The experimental results show that the friction coefficient of the wire ropes experiences running-in and stable stages at the varied load or wear time,and it decreases with increasing load.There exists a critical wear frequency(or wear velocity)within the given frequencies.Meanwhile,the friction coefficient at the high wear frequency increases slowly with increasing time when it experiences the fluctuation at running-in period.In addition,according to the theory of wire rope and the creep and relaxation theories of wire material,the stress relaxation model of the hoisting wire rope strand is established,into which the contact between the central and outside wires and Poisson’s ratio effect are incorporated.Further,the stress relaxation model is solved with the conjugate gradient method and fast Fourier transform method,and the accuracy and efficiency of the solution are verified.The numerical results show that the axial tensile stress and von Mises stress relaxations occur in the strand subjected to a tensile load.Meanwhile,decreasing the outside wire diameter or increasing the helix angle leads to increments in the creep strain and axial tensile stress,while it helps to reducing the interwire contact deformation,contact pressure and von Mises stress.Finally,based on the deduced parametric equations of shaped strands such as spiral oval and spiral triangular strands,the accurate and effective finite element models of the two strands are established using commercial modeling software NX and commercial finite element software ANSYS.Simultaneously,the tensile,torsional and bending performances of the spiral oval and spiral triangular strands are comparatively analyzed by the varation of their outside diameter and helix angle.The numerical results show that both von Mises stresses of the spiral oval and spiral triangular strands increase with increasing outside wire diameter and helix angle under tensile and tosional loads.The study also shows that there exists an obvious neutral layers in the spiral oval and spiral triangular strads subjected to the bending load,and the interwire sliding on the two sides of neutral layer can easily result in a friction and wear of the lifting wire rope.