Y. Tachibana et E. Krempl, MODELING OF HIGH HOMOLOGOUS TEMPERATURE DEFORMATION-BEHAVIOR USING THE VISCOPLASTICITY THEORY-BASED ON OVERSTRESS (VBO) .1. CREEP AND TENSILE BEHAVIOR, Journal of engineering materials and technology, 117(4), 1995, pp. 456-461
The viscoplasticity theory based on overstress (VBO) is a state variab
le theory without a yield surface and without loading/unloading condit
ions. It contains two tensor valued state variables, the equilibrium (
back) stress and the kinematic stress that is a repository for work ha
rdening (softening). The scalar valued isotropic or time (rate)-indepe
ndent stress models cyclic hardening (softening). For application to h
igh homologous temperature, the effects of diffusion which counteracts
the hardening of inelastic deformation has to be accounted for Recove
ry of state terms are introduced in the growth laws for the state vari
ables. A high homologous temperature VBO model is introduced and appli
ed to the creep and tensile tests of Alloy 800 H between 750 degrees C
and 1050 degrees C. Primary secondary and tertiary creep as well as t
ensile behavior were well reproduced. It is shown that the transition
to fluid state can be modeled with VBO.