Relaxation behavior of a three-layered wire cable under a combined tension and bending load

Stress relaxation happens to a wire cable that is often wrapped around a pulley during a long-term service process, which causes mechanical performance degradation of the wire cable. In order to investigate the stress relaxation performance of a three-layered wire cable subjected to a combined tension and bending load, a finite element simulation model of a wire cable-pulley device is established using methods of parametric modeling and modified time-hardening modeling, during which the coupling effect between the stress relaxation and contact property is considered. The distributions and evolutions of creep strain, von Mises stress, and contact pressures are obtained. The influence of the lay angles of the helical layers, the axial load, and wrap angle on the stress relaxation behavior of the wire cable is analyzed. The results show that the maximum contact pressure, maximum equivalent stress, and maximum creep strain all occur in the middle region of the three-layered wire cable in the wrap section and locate near the pulley side. The stress relaxation causes smaller magnitudes and more uniform distributions of the contact pressure and equivalent stress, which reduces the risk of severe local contact. The interwire contact pressure, relaxation rate, creep rate, and bending moment reduction of the three-layered wire cable increase with the increments in the lay angles of helical layers, the axial force, and the wrap angle. Under the combined tension and bending load, the stress distribution of the wire cable is mainly concentrated in the middle of the bending section, where stress yielding and other dangerous conditions are most likely to occur. The stress relaxation behavior of the wire cable is sensitive to the lay angle of the intermediate layer and the wrap angle.