MODELLAZIONE DEL COMPORTAMENTO MECCANICO DELL’IRIDIO PURO IN CONDIZIONI DI SOLLECITAZIONE DINAMICA

The present work show the results obtained from the testing campaign on pure iridium at different temperatures (25÷1250 °C) and strain-rates (10-3÷104 s -1 ) in order to identify a strength material model. At low temperature, the material deforms uniformly up to fracture; at intermediate temperatures, it shows an early necking at low strain-rates while a marked hardening followed by necking at higher speed; over 1000 °C it shows an initial uniform elongation followed by necking. Due to the presence of recrystallization (between 750 e 1000°C), it was not possible to identify a unique material model, but the idea was to get two different Johnson-Cook models by means of a multi-objective optimization. The likelihood of the obtained parameters was validated through FE simulation of the different loading conditions. Post-mortem analyses of the fracture surface proved the presence of different failure mechanism.