IDENTIFICATION OF LOCAL VISCOPLASTIC PARAMETERS IN WELDS AT ROOM TEMPERATURE AND 625°C BY INVERSE METHOD BASED ON DIGITAL IMAGE CORRELATION AND FINITE ELEMENT SIMULATION

This work deals with an inverse identification method of constitutive equations parameters applied to tensile experiments conducted at room temperature and 625 degrees C for each part of a steel welded joint (base metal, ICHAZ [Intercritical Heat Affected Zone], FGHAZ [Fine Grain Heat Affected Zone], CGHAZ [Coarse Grain Heat Affected Zone] and weld metal. Digital image correlation (DIC) is used to generate experimental input data for finite element simulations of tensile and tensile-relaxation tests. An evolution of the constitutive equation is presented as a function of the different studied loading conditions. Viscosity is added for the 625 degrees C tensile tests. In order to analyze a wide range of strain rate with 625 degrees C tensile-relaxation tests, an elasto-visco-plastic constitutive equation with a double Norton flow is chosen. Each part of the welded joint has a different behaviour in terms of yield stress, ultimate tensile stress and hardening at both room temperature and 625 degrees C. After identification, simulations show a good agreement with experimental results.