EFFECT OF INTERFACIAL TRELLIS CONTACT FORCES IN A WIRE ROPE

摘要

Tension resisting elements like wire ropes are critical elements in countless engineering applications ranging from material handling, construction site applications, tethers in underwater platforms, apart from stay cables in cable stayed bridges. The main advantage of the wire rope lies in its capacity to support large axial loads with high flexibility in bending and torsional modes. These properties are useful for their own storage, transportation and also in engineering applications where - frequent bending is encountered in pulleys/sheaves/drums. The source of such a peculiar mechanical property of the rope can be attributed to the local relative movements between adjacent wires of the rope. A wire rope is a cable assembly consisting of a central core strand surrounded by a number of strands wound helically in a single or multi layers. The wires making up the strand are of helix patterns and when such strand combine to form a rope it takes up invariably another helix pattern, involving many times, a double helix arrangement. Depending on the nature of the contact of the helical wires at their interfaces the rope behaviour can be examined. Point or line contact forces, may arise, resulting in localised stresses. When these strands are assembled to form a wire rope, the complexity of the interfacial contact arrangement generally lead to simplified assumptions for predicting the rope response. An attempt is made in this paper to model a wire rope strand and deduce its equations of equilibrium, considering the interfacial contact forces andstudying the associated slip of the wires. A mathematical model is developed to estimate the axial and torsional response of the rope. The effect of the interfacial forces is studied and compared with earlier researchers, where such considerations are not or partially made.