Localization in a quasibrittle material is studied using a local second-gradient model.
Since localization takes place in a medium assumed to be initially homogeneous,
nonuniqueness of the solutions of an initial boundary value problem is then also
studied. Using enhanced models generalizes the classical localization analysis. In
particular, it is necessary to study solutions more continuous (that is, continuous up
to the degree one) than the ones used in analysis involving classical constitutive
equations. Within the assumptions done, it appears that localization is possible in
the second-gradient model if it is possible in the underlying classical model. Then
the study of nonuniqueness is conducted for the numerical problem, using
different first guesses in the full Newton–Raphson procedure solving the
incremental nonlinear equations. Thanks to this method, we are able to simulate
qualitatively the nonreproducibility of usual experiment in the postpeak
regime.
Keywords
continuum with microstructure, second gradient, finite
element, bifurcation, strain localization, mode switching,
reproducibility