ON THE USE OF PRESSURE-SENSITIVE CRITERIA TO PREDICT YIELDING AND MULTIAXIAL FATIGUE DAMAGE IN METALLIC STRUCTURES

摘要

Most cyclic plasticity models used in multiaxial fatigue life predictions are based on a concept of a yield surface, which divides the elastic and plastic domains. Plastic straining occurs when the stress state reaches the surface and tries to move outward. Subsequent plastic straining causes the stress state to remain on the yield surface, which will translate to prevent the stress point from moving outside it according to a kinematic hardening rule that models the Bauschinger effect. The accurate modeling of the yield surface shape is fundamental to predict stress-strain relations. In this work, the main yield surface equations for isotropic materiais are compared. Even though most materiais can be modeled using Mises and Tresca surfaces, other need to consider the effect on the yield strength of the hydrostatic stress or the normal stress acting on a criticai plane. It is shown that pressure-sensitive models originally devised for concrete can be applied to predict yielding in some materiais, and even fatigue life for metallic structures with short cracks.