Abstract
Motivated by Ziegler's extremum principle, the author proposed a new hypothesis which leads to flow rules for granular materials as well as stress-dilatancy relationships. In this theory, the dissipation function has some specific characters so that the dissipation mechanism of friction can be taken into account. The simplest form of the function is obtained by generalizing Roscoe's dissipation energy and it gives the identical flow rule with Lévy-Mises relation for the metal plasticity. Another type of dissipation function is introduced through the microscopical consideration of frictional energy in granular assemblies. The corresponding flow rule seems agreeable with the plastic behaviors of granular materials observed through experiments in the past.
