A variational principle for a class of layered media

A variational principle is stated which describes the isothermal flow of a class of ideal incompressible materials, of which the ideal non-Newtonian liquid and the rigid-plastic von Mises solid are special cases. The principle is extended to multi-layered media separated by a prescribed interface. An inverse method is outlined for the determination of the common surface between two materials for flows parallel to a given plane.