The ORNL constitutive model in
Abaqus/Standard
is based on the March 1981 issue of the Nuclear Standard NEF
9–5T and on the October 1986 issue, which revises the
constitutive model extensively. This model adds isotropic hardening of the
plastic yield surface from a virgin material state to a fully cycled state.
Initially the material is assumed to harden kinematically according to a
bilinear representation of the virgin stress-strain curve. If a strain reversal
takes place or if the creep strain reaches 0.2%, the yield surface expands
isotropically to the user-defined tenth-cycle stress-strain curve. Further
hardening occurs kinematically according to a bilinear representation of the
tenth-cycle stress-strain curve.
You must specify the virgin yield stress and the hardening through a
plasticity model definition and the elastic part of the response through a
linear elasticity model definition. You specify the tenth-cycle yield stress
and hardening values separately. The yield stress at each temperature should be
defined by giving its value at zero plastic strain and at one additional
nonzero plastic strain point, thus giving a constant hardening rate (linear
work hardening).
Abaqus/CAE Usage
Property module: material editor: : and
Abaqus/Standard
also allows you to invoke the optional kinematic shift
(α)
reset procedure that is described in Section 4.3.5 of the Nuclear Standard. If
you do not specify the α
reset procedure explicitly, it is not used.
Input File Usage
ORNL, RESET
Abaqus/CAE Usage
Property module: material editor: : Invoke reset
procedure