抄録
The occurrence of a nose, i.e. non-convexity, in the stress rate response envelope of the elastoplastic constitutive model to certain stretching directions can be explained as the result of the natural property of the model adopting the pressure dependent yield/plastic potential function, whist the elastoplastic constitutive model assuming a non-associated plastic flow violates a condition of the plastic relaxation of the second work rate or stiffness moduli, representing the so-called Drucker's postulate on stability. In this article, the characters of the noses formed by the model involving associated and non-associated flow rule with pressure dependent yield/plastic potential function are examined focusing of the Drucker's postulate on stability. The existence of the stable softening mechanism is also pointed out for the non-associative elastoplastic materials.
