Contact models in cable assemblies

Abstract

Helically wound fibres or wires constitute a wide class of components in many engineering applications. This thesis addresses the modelling of the cable assembly by considering the individual wires or strands as thin rods curved, bent and twisted and stretched elements, working in unison at their contact interfaces, and to predict the local as well as global performance more accurately. The formulations made in respect of the above included the Poisson s effect of the materials of the wire and the core, the radial contraction due to the contact forces, refinement of curvature and twist expressions to include the Poisson s effect of the wires and usage of generalised strain theory to account for the curvature and twist of the helical wires with the effects of the wire stretch. Numerical computations are made for a single layered strand that maintained the combined contact mode, at the initial stage of loading and the threshold limits at which this cable changes to the core wire radial contact mode are identified. The results are validated with experimental works on two cables, one consisting of an all steel earth wire and another with a bimetallic combination of a steel wire core with a single layer of six aluminium wires, known as ACSR Dog Conductor, used in the overhead electrical power transmission lines. Similar formulations are extended to a multilayered cable assembly and the contact forces in the wire interfaces in the radial, hoop or lateral directions are estimated for the wires situated in different layers. This thesis has particularly addressed the existence of a combined contact mode in the initial stages of loading and has evaluated the corresponding stiffness of the cable assemblies. Increased stress value in the very initial stage of loading will have considerable influence on the design of cables for such applications. This is cited as the unique contribution, particularly when handled with the refined curvature and twist expressions as mentioned above. newline newline newline