3-3 – Material Instabilities
Ahmed Benallal (LMT, Ens Paris Saclay/CNRS), Henryk Petryk (Institute of Fundamental Technological Research, IPPT)
Material instabilities occur frequently in the mechanics of solids. Many inelastic phenomena like plasticity, damage or martensitic transformations can themselves be understood as macroscopic effects of micro-scale instabilities. Material instabilities are usually considered as linked to particular features of the material behavior such as softening (strain, thermal, geometric) and/or non-associativity, as well as to sensitivity to small disturbances and imperfections, lack of a unique response, emergence of nonuniform deformation patterns. Spontaneous localization of deformation, fracture initiation and failure in ductile materials, formation and evolution of microstructures, nano-scale phenomena of non-smooth nature but also various surface and interfacial phenomena are mostly observed. In the current trends to describe more and more accurately the materials behaviour over multiple length scales, instabilities can enforce development of novel concepts and methods motivated by difficulties in applying standard approaches.
Material instabilities represent the key to the modeling of a number of observed phenomena, as exemplified by: shear bands and localization of deformation; progression of compaction bands in ceramic powders and cellular materials; non-local or straingradient effects on instabilities; slip-system nonuniqueness and deformation banding in ductile single crystals; inhomogeneous slip distribution and dislocation clustering during plastic flow; creation or annihilation of interfaces during martensitic phase transformation; surface phenomena such as peel-orange, etc.; and also large-scale failure processes occurring for instance during earthquake or landslide failures.
The aim of the mini-symposium is to bring together scientists specialized in mathematical modeling and analysis, computational techniques, and experimental methods, related to material instability of any kind.