Metals
For metals whose material behavior includes metal creep and/or time-dependent volumetric swelling, the routine allows any “creep” and “swelling” laws (viscoplastic behavior) of the following general form to be defined:
where
- ˉεcr
-
is the uniaxial equivalent “creep” strain, conjugate to ˜q, the Mises or Hill equivalent stress;
- ˉεsw
-
is the volumetric swelling strain;
- p
-
is the equivalent pressure stress, p=-13(σ11+σ22+σ33); and
- ˜q
-
is the equivalent deviatoric stress (Mises' or, if anisotropic creep behavior is defined, Hill's definition).
The user subroutine must define the increments of inelastic strain, △ˉεcr and △ˉεsw, as functions of p and ˜q and any other variables used in the definitions of gcr and gsw (such as solution-dependent state variables introduced by you) and of the time increment, △t. If any solution-dependent state variables are included in the definitions of gcr and gsw, they must also be integrated forward in time in this routine.
Abaqus computes the incremental creep strain (or the incremental viscoplastic strain) components as
where n is the gradient of the deviatoric stress potential, defined as
and R is a matrix with the anisotropic swelling ratios in the diagonal if anisotropic swelling is defined; otherwise, R=I.