New empirical relationship is proposed to calculate instantaneous maximum diameters on the sample during compression test. The proposal is a relationship between instantaneous maximum diameter, friction coefficient, initial dimensions of the sample and the displacement during the compression test. Seventeen compression tests were carried out to copper cylindrical samples without lubrication at room temperature to obtain this new empirical relationship. Numerical simulations were carried out taking into a count this new relationship for numerical validation. The maximum diameters calculated with this new empirical relationship are the same to the experimental measurements. The mechanical behavior calculated with this new relationship and with the friction corrections of Rowe and Dieter are similar. The simulations are similar to the experiments, with differences lower than 4.21%. The simulation shows higher hardening in the middle of the sample than on the bottom. Numerical simulations show that, possibly, the friction coefficient between sample and dies changes meanwhile the sample is hardening.

La mayoría de los procesos industriales para la obtención de productos por conformado en caliente transcurren durante el enfriamiento del material que se está trabajando. Esto ocurre debido a que no es posible aislar térmicamente por completo el material de trabajo del equipo, imposibilitando realizar el conformado en condiciones adiabáticas, ya sea en un proceso de colada continua, en trefilado de conductores eléctricos de cobre o en cualquier otro proceso industrial de conformado en caliente.El conformado en caliente es uno de los métodos más empleados para obtener productos metálicos semielaborados o finales. La recristalización durante el conformado en caliente es un proceso dinámico durante el cual las velocidades relativas de nucleación y crecimiento de granos nuevos determinan las propiedades mecánicas (•) Efecto de la velocidad de deformación en la recristalización dinámica de un cobre ETP durante su compresión en caliente con temperatura descendente (·)G. Torrente*, M. Torres* y L. Sanoja** ResumenEn el presente trabajo se estudia el efecto de la velocidad de deformación en la recristalización dinámica de un cobre electrolítico puro durante su deformación en caliente con temperatura descendente. Para ello, se realizaron ensayos de compresión en caliente hasta deformaciones verdaderas cercanas a uno, con cuatro velocidades de deformación, mientras descendía la temperatura. Los ensayos realizados a las dos velocidades de deformación más bajas mostraron recristalización dinámica de picos múltiples con un ascenso de la tensión en lugar del estado de saturación, debido probablemente al continuo descenso de la temperatura. Con el aumento de la velocidad, los ensayos restantes mostraron recristalización de pico simple y solo restauración, respectivamente. Los resultados experimentales se compararon con los de una simulación basada en el modelo cosenoidal amortiguado de Avrami. La simulación arrojó resultados próximos a los medidos durante la recristalización dinámica de picos múltiples, sugiriendo la aplicación del modelo a procesos de recristalización dinámica de picos múltiples con temperatura variable. Palabras ClavesCobre electrolítico puro; Recristalización de picos múltiples; Modelo cosenoidal amortiguado de Avrami; KJAM; Zener-Hollomon. Effect of the strain rate in the dynamic recrystallization of ETP copper during its hot compression with descending temperatures AbstractThe main purpose of this project is to establish the effect of strain rate in the dynamic recrystallization of an ETP copper during its hot deformation with descending temperature. For this, there were made some tests of hot compression until true deformations close to one, with four strain rates while the temperature was descending. The tests that were made to the two lowest strain rates, showed a multiple peaks dynamic recrystallization with a rise of the tension instead it reaches the steady state, maybe due a continuous decline of the temperature. With the increase of rate the rest of the tests showed simple peak recrystallization...

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The Norton-Bailey equation was used to simulate by finite elements the hardening and dynamic recovery of copper during the hot compression tests. The constants of Norton-Bailey equation were determined from the Voce-Kocks model. The simulation assumes a Mortar Contact with Coulomb friction and axial symmetry. Numerical results were compared with experiments. Six compression tests were carried out at 804 K, three with a strain rate of 0.1 s -1 and three with a strain rate of 1 s -1 . The results show: The differences between the experiments and the simulations are less than 7.69% for strain rates of 0.1 s -1 , and less than 0.67% for strain rates of 1 s -1 . This shows that the simulation of hardening and dynamic recovery of hot copper is possible with the Norton-Bailey equation. Better numerical results were obtained when the behavior of copper is typical of hardening and dynamic recovery, and this happen for high values of strain rates.