How to define a function in UMAT

[lisw]

Hi guys,
If I need a function in UMAT which is able to provide a extra strain in terms of time or some other variables, how should I define that?

 

[xerf]

If use UMAT you have to store the components of the strain tensor(s) as STATE variables (i.e STATEV array).

Technically it is up to the user to manage and use the STATEV array according to his needs.

For example you can design something like this:
STATEV(1) - elastic strain component 11
STATEV(2) - elastic strain component 22
.......................................
STATEV(6) - elastic strain component 13

STATEV(7) - plastic strain component 11
STATEV(8) - plastic strain component 22
.......................................
STATEV(12) - plastic strain component 13

STATEV (13) - equivalent plastic strain
STATEV (14) - whatever I want to store in STATEV(14)
and so on.....

UMAT Subroutine is supplied with plenty of info when it is called, inclunding time, temperature, step number etc. ...all the parameters being explained in the documentation section describing the subroutine.