A new localized inverse identification method for high temperature testing under resistive heating: Application to the elastic‐viscoplastic behaviour of L‐PBF processed In718

Abstract

The mechanical behaviour of the nickel-based superalloy In718, as processed from laser powder bed fusion (L-PBF) additive manufacturing, is characterized at high temperature, from 800 to 1100 C. Samples built by L-PBF are submitted to sequences combining uniaxial tensile load at different prescribed velocities, and relaxation steps of different durations, operated under resistive heating under vacuum, with a home-developed testing machine. Tests are equipped with force evolution measurement, with infra-red field imaging and thermocouples to capture the non-uniform temperature distributions induced by resistive heating, and with digital image correlation to capture the nonlinear displacement fields. An inverse finite element strategy is developed to identify the parameters of a temperature-dependent elastic-viscoplastic behaviour model. The strategy is based on (i) direct finite element simulations of tests, (ii) a cost function expressing the distance between calculated and measured quantities, and (iii) a minimization algorithm. Direct numerical simulations are performed on a limited part of the working zone of samples, the zone of interest, with applied boundary conditions provided by DIC records and with an imposed temperature distribution provided by infra-red imaging. The cost function is based on the force evolution only, for a series of different tests operated at different nominal temperatures. Optimum values of constitutive parameters are obtained by minimizing the cost function value, which is achieved with the home-developed optimization platform MOOPI. Finally, the identified parameters are discussed with respect to the literature.additive manufacturing, high temperature DIC, high temperature mechanical behaviour, In718, inverse identification, laser beam melting | INTRODUCTIONNowadays, numerical thermal-mechanical simulation of additive manufacturing by laser powder bed fusion (L-PBF, also known as selective laser melting, SLM, or laser beam melting, LBM) is in constant development to predict defects, such as cracks, residual stress, and distortion. [1][2][3][4][5][6][7][8][9] Simulation is conducted at different scales, essentially the part scale

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