Finite element analysis of compressive deformation of bulk metallic glasses

Finite element analysis of a stress-overshoot phenomenon in a Pd-based bulk metallic glass was carried out using a fictive stress model in conjunction with the Maxwell viscoelastic model under uniaxial compression. The overshoot results from non-linear viscoelasticity in the glass transition region, under deformation at constant strain rate. The friction effect between a cylindrical workpiece and a die was shown to produce mainly three stress-concentration sites, which play an important role in creating free volume. These sites give rise to a redistribution of the structural disordering state inside the workpiece, and lead to a change of the average stress blunt. Once inhomogeneous deformation occurs during the development of the stress peak at the initial stages under high strain rates (5 x 10(-3)-2.2 x 10(-2) s(-1)), the effective stress distribution within the workpiece becomes narrow and the deformation homogeneity is recovered in the ensuing steady state flow. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.