On elastoplastic deformation of grey cast iron

Many engineering materials appear an independent from the kind of loading elastoplastic material behavior. With respect to the sign convention we get, for instance, the same stress-strain diagrams for tension and compression. For materials which contain voids, pores, etc., different elastoplastic stress–strain curves can be obtained in tension and compression tests. In addition to these experimental observations, such materials often show inelastic volumetric deformations. Grey cast iron is a typical example of this kind of material. Constitutive equations for this special elastoplastic behavior are derived as a particular case of generalized constitutive equations for isotropic materials based on a potential. The yield condition is established on the second invariant of the stress deviator and, additionally, on the first invariant of the stress tensor and on a hardening parameter. The plastic potential depends on the same arguments, but a nonassociated flow rule is assumed. For the hardening function, a modification of the plastic work hardening model is used. All parameters of the model are identified by tests. The verification is realized by different independent tests.