modifing UMAT for tresca yield

[prashant sharma]

hi every one, i hang up with a problem while i am trying to modifing the abaqus UMAT for tresca yield condition ,,, so any one can tell me what to keep in mind while modifing the uMAT for tresca as it is made for SMISES yield..

waiting for help

prashant

[Jorgen]

I don't quite understand: you are modifying "tha abaqus UMAT for tresca yield condition". What is that UMAT and where did you get it??

A UMAT subroutine is used to specify the complete stress-strain response, not only yielding. Can you explain more about what you are trying to do?

- Jorgen

[prashant sharma]

actaully my objective is to analysis a annular disk with elastic-plastic material properties. as u r familiar with ABAQUS it uses the smises yield creteria for yielding once the component cross the yield point ( this is done in two ways one way is to define stress-strain curve in standard deck file & other way is to uses the UMAT agian which assume the yielding smises). but my aim is to uses the tresca yield condition instead of smises in my analysis , so for that i am keeping all other parameters untouched in ABAQUS UMAT since they will be same for both material and tring to change only yield function.

now i think u have understand my problem.. so please let me know how to modify the UMAT or if i have to write the UMAT freshly for tresca yield condition how i can write it.

thanks in adavance

-prashant

[Jorgen]

I still do not quite understand. If you are not happy with the built-in elastic-plastic model in ABAQUS, then you can write your own UMAT. If you have experience writing UMATs then it will not be that difficult to create a model based on the Tresca yield condition. If you do not have experience writing UMATs then I recommend that you start reading the user's manuals very carefully...

- Jorgen

[magiconly]

it's very easy. There is already UMAT for mises theory in user manual. what you need to do to modify the criterion for yielding. the first thing you need do is get toatally understand of the example UMAT, then it's easy to change. you can refer to "introduction to computatioanl plasticity" by FUNNE (OXford University). GOOD LUCK