Ratchetting Deformation Analysis by Inelastic Constitutive Equations Incorporating Tension-Compression Asymmetry
Masatsugu YAGUCHI and Yukio TAKAHASHI
Abstract:Based on the authors' previous model and Ohno-Wang model, a viscoplastic inelastic constitutive model considering tension-compression asymmetry was developed to describe ratchetting deformation behavior of modified 9Cr-1Mo steel adequately. In the new constitutive model, the first invariant of stress was introduced into the flow rule in order to express the asymmetry. Furthermore, static recovery term was introduced into the Ohno-Wang type kinematic hardening rule to express rate/time-dependent deformation accurately, and strain range dependency of cyclic softening behavior was introduced to express effect of cyclic softening on ratchetting deformation precisely. Through the application to various test conditions, it was demonstrated that the present inelastic constitutive model is capable to describe uniaxial and multiaxial ratchetting behavior of the material with reasonable accuracy, including unordinary ratchetting behavior under vicinity of zero mean stress as well as the asymmetric monotonic and cyclic deformation behavior. Key Words:Tension-compression asymmetry, Ratchetting deformation behavior, Modified 9Cr-1Mo steel,Inelastic constitutive equations, Cyclic softening behavior