Inelastic constitutive equation in Alloy800H

Kaji, Yoshiyuki  ; Kikuchi, Kenji; Penkalla, H. J.*

A creep constitutive equation in Alloy800H was developed at 700, 800 and 850oC. In the equation, the inelastic strain rate is written in the form of a flow equation of the Norton-Bailey type and the hardening during deformation under various loads is induced by an internal stress which is subdivided into back stress and friction stress. The back stress represents a conservative part of the creep resistance while the friction stress includes all the dissipative parts in the internal structure such as grain boundary sliding, diffusion and interaction between dislocation and precipitation. Parameters were determined by the deformation properties for creep under constant stress conditions at each temperature. Deformation analyses show a good agreement between calculations and experimental results for creep tests at each temperature.