Experimental analysis and modeling of the mechanical and structural behavior of copper wires under creep and thermal damage tests

Abstract

This research proposes an in-depth experimental and analytical analysis to assess the mechanical and structural behaviour of industrial copper wires, subjected to tensile, creep and degradation tests at high temperature. In order to carry out these tests, a bespoke device has been developed to enable creep measurements to be taken in real time without the need for extrapolation. The work focused mainly on characterising the evolution of damage mechanisms according to temperature and stress conditions, and determining the fundamental creep parameters using analytical modelling based on the principles of the Arrhenius and power laws. The experimental tests carried out enabled the three classic phases of creep behaviour to be observed, with particular emphasis on the stable flow state. This phase was used to identify the minimum creep speeds and activation energies, which range from 22.5 to 39.9 kJ/mol depending on the stress levels applied. The damage process was modelled using the theoretical framework proposed by Erismann, with significant agreement observed between the predictive curves and the experimental data. A critical life fraction of approximately 62 % was determined, indicating that beyond this threshold, the probability of failure becomes significantly increased. Microstructural analyses using scanning electron microscopy (SEM), together with a study of the structural evolution using X-ray diffraction (XRD), revealed marked deformation of the grain boundaries and the formation of cavities at high temperatures. These microstructural phenomena are closely linked to the deterioration in mechanical properties observed. The results obtained confirm not only the efficiency and accuracy of the experimental set-up developed, but also the validity of the analytical models used. These advances will help to improve the reliability of industrial cables and optimise predictive maintenance strategies in demanding environments.