Study of the Effect of Large Deformation Through a Finite Deformation Based Constitutive Model for Metallic Glasses

A thermodynamically consistent constitutive model of metallic glass is presented by extending the infinitesimal deformation model of Huang et al. [Huang, R., Suo, Z., Prevost, J. H., and Nix,W. D., 2002.Inhomogeneous deformation in metallic glasses,J. Mech. Phys. Solids, 40, 1011–1027] to finite deformation. The underlying theory behind the model is the free volume theory with free volume concentration as the order parameter affected through the processes of diffusion, annihilation and creation. The main assumptions of the model include multiplicative decomposition of deformation gradient and additive decomposition of free energy. The former comprises of elastic, inelastic dilatational component associated with excess free volume concentration and isochoric plastic part while the latter consists of contributions from elastic deformation and free volume concentration. The plastic part evolves according to Mises-theory and the local free volume concentration. Homogeneous simple shear is the model problem solved using the present model and compared with the infinitesimal deformation theory to examine the effect of large deformation on stresses in metallic glasses.