Interface stability under biaxial loading of bilayered sheets between rigid surfaces—I. Bifurcation analysis

bifurcation method has been applied to the plastic stability analysis of a bimetallic sheet between rigid surfaces subjected to biaxial loading. An orthotropic, incrementally-linear solid and plane strain conditions are assumed. In order to predict the stability behaviour near the bimaterial interface, three possible regimes (elliptic, hyperbolic and parabolic) are considered and two modes of instability are mentioned, namely, the diffuse mode, characterized by spatially periodic deformations, and the localized shear band mode. In general, undulations can be expected in the elliptic regime and shear band instabilities only appear in the hyperbolic and parabolic regimes. Attention is concentrated on the diffuse mode. Critical equivalent strains have been obtained, as a function of a wavenumber defined in the analysis. Numerical results are presented for three different constitutive models and for a number of combinations of the geometric and material parameters, to assess their influence on the critical strain. Copyright © 1996 Elsevier Science Ltd.