Implementation of viscoplastic constitutive model in MARC computer code

The MARC non-linear finite element computer program [1] has been used for incorporation of the Bodner-Partom model (Viscoplastic behaviour). The main objective is to provide evidence for the applicability of the unified constitutive models to describe the time and temperature dependent response of metals submitted to arbitrary load or deformation histories, and in addition, to demonstrate the practical application that will depend on their adaptability in computational algorithms when incorporated into finite element methods for stress analysis. The aspects that are explained in the following paragraphs are: a) A brief summary of the main concepts of Bodner-Partom model. b) Implementation in MARC : Subroutines applied. c) Calculations performed and comparison with classical approach and test results. d) Main results and conclusions. The calculations are carried out on test specimens for LCF conditions with and without dwell time at the maximum strain in each hysteresis cycle, for two materials typical in turbine discs for aeronautical applications. This research is part of a BRITE/EURAM project Programme BREU 6021 " Development of an understanding of materials properties under the combined influence of creep, fatigue and oxidation".