Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Fretting fatigue of 6201 aluminum alloy wires under variable amplitude loading
Submission Author:
Ian Matos , DF
Co-Authors:
Ian Matos, JOSE ALEXANDER ARAUJO, Fábio Castro
Presenter: Ian Matos
doi://10.26678/ABCM.COBEM2021.COB2021-1561
Abstract
In recent years, much has been done to understand the fretting process that takes place in overhead conductors subjected to aeolian vibrations. While traditional fatigue tests on conductors are still widely used, new studies have tried to understand the fretting process by means of local scale fatigue tests between two wires in contact. Additionally, efforts have been directed towards the development of finite element models of the conductor and the contact between wires. However, little has been done to provide a more realistic representation of the aeolian vibrations in such tests and simulations. While most studies consider constant amplitude vibrations, field measurements suggest that the conductors' oscillations have a variable amplitude nature, often following a beat pattern. In this context, the present study investigates the fretting behavior of wires under variable amplitude loading. Fretting fatigue tests on a wire/wire contact configuration were performed using 6201-T81 aluminum alloy wires taken from an AAAC (All Aluminum Alloy Conductor) 900 MCM conductor. The tests were be performed using loading blocks and beat pattern oscillations representative of the amplitude variations verified in transmission lines. A finite element-based life estimation methodology was implemented to predict the fatigue lives of the wires. The methodology uses an average stress over a fatigue damage zone to consider the stress gradients beneath the contact and the Smith–Watson–Topper parameter to quantify the fatigue damage. In previous studies, this methodology was employed to predict the fatigue lives of wires under fretting conditions when subjected to constant amplitude fatigue loadings. The goal of the present research was to extend this methodology for problems with variable amplitude loading, using the rainflow method for cycle counting and the Miner's damage rule to estimate the damage produced by a beat or a loading block. To evaluate the methodology, the estimated lives are compared to the ones observed in the fretting fatigue tests. The effect of variable amplitude on the fretting regime and fracture behavior of the wires is investigated.
Keywords
Overhead Conductor, Aluminum wire, Fretting Fatigue, variable amplitude loading, life prediction
