Many thermal constitutive models require the storage of solution-dependent
state variables. These state variables might include microstructure or phase
content information when the material undergoes phase changes. You should
allocate storage for these variables in the associated material definition (see
Allocating Space for Solution-Dependent State Variables).
There is no restriction on the number of state variables associated with a
user-defined material.
User subroutine
UMATHT is called for each material point at each iteration of
every increment. It is provided with the thermal state of the material at the
start of the increment (solution-dependent state variables, temperature, and
any predefined field variables) and with the increments in temperature,
predefined state variables, and time.
User subroutine
VUMATHT is called for blocks of material points at each increment.
When the subroutine is called, it is provided with the state at the start of
the increment (temperature, internal energy per unit mass, solution-dependent
variables, and any predefined field variables) and the state at the end of the
increment (temperature, spatial gradients of temperature). The
VUMATHT user material interface passes a block of material points
to the subroutine on each call, which allows vectorization of the material
subroutine.