FUNDAMENTALS IN CONSTITUTIVE EQUATION: CONTINUITY AND SMOOTHNESS CONDITIONS AND LOADING CRITERION

 KOICHI HASHIGUCHI

ABSTRACT The continuity and smoothness conditions and the loading criterion are the most fundamental elements in constitutive equations for reversible/irreversible deformation, which have been defined and formulated by the author (Hashiguchi, 1993a, b, 1994). In this article the continuity and smoothness conditions are reviewed in detail. Further, the loading criterion for plastic stretching in the constitutive equation with the plastic potential surface is derived from the requirement that the proportionality factor in the plastic potential flow rule is positive; this would generally be applicable even to constitutive equations for the description of time-dependent elastoplastic deformation. In addition, the defects caused by the violation of continuity and smoothness conditions are verified illustrating unrealistic deformation behaviors predicted by the conventional and well-known cyclic plasticity models.

Key words: constitutive equation of soil, elasticity, (loading criterion), plasticity, stress, (subloading surface model) (IGC: D6/E2)