Uniaxial/Multiaxial Creep-Ratchetting of Several Types of Steels and Its Constitutive Modelling

Abstract

In the last two decades, ratchetting (or cyclic creep, i.e. cyclic stress-induced strain accumulation) has been intensively studied, and several interesting phenomena have been reported, such as the effects of maximum stress and mean stress in uniaxial ratchetting [1–6]; the effect of the primary stress and its variation in multiaxial ratchetting [6–12]; biaxial strain accumulation [13–17]; time-dependent behavior and creep effect [2, 7, 10, 15–17]; and the effects of temperature and its variation on the material behavior [10, 15–18]. If we look at carefully these experimental data, we can find that the ratchetting behavior strongly depends on types of materials. About this point, Hassan & Kyriakides [19] mentioned that cyclic hardening/softening nature has a significant effect on uniaxial/multiaxial ratchetting, and they also presented constitutive models to describe the different ratchetting behavior appearing for several types of steels. However, they restricted the discussion within the framework of rate-independent plasticity, even though the viscoplasticity of materials (rate-dependent ratchetting or creep effect) sometimes plays an important role in ratchetting.