Using UMAT for composite failure simulation

[shripadtokekar]

Hi
i m doing simulation of composite material in ABAQUS and for simulaiton progressive failure i have to use UMAT subroutine but i dont have any idea about how to write that. so please help me regarding that. if i can get any subroutine similar to that i can use that to understand and write my subroutine. please help thank you

[Jorgen]

If your only option is to use a UMAT then you need to two two things:
(1) write a UMAT for the material model that you are intersted in
(2) add a failure condition to that UMAT such that the stiffness goes way down at failure

Note that an ABAQUS/UMAT does not support element deletion. To simulate failure it is typically better to use ABAQUS/Explicit.

- Jorgen

[shripadtokekar]

thank u very much .....actually i m doing quasi-static simulation of composite tubes under latral loading. is it possible to do this siumulation in ABAQUS/standard. i have done it in ABAQUS/explicit but my elements are not geting deleted what i should do to delete my elements?? or is only posssible to delete the elements through VUMAT?? how can i get help regarding UMAT
one more thing i want to ask is that if i use subroutine USDFLD for failure criteria is it feasible. in this case how field variable are related to stiffness values???
please help me regarding this

[shripadtokekar]

please help me ...regarding above..thank you

[Jorgen]

You have many questions ;)

Here are are few comments:
:arrow: You can code failure into both a UMAT and a VUMAT.
:arrow: To enable element deletion in explicit you need to use the "DELETE" parameter on the "*DEPVAR" command.
:arrow: The best help for writing UMAT and VUMAT subroutines is to read the manuals very carefully, and, of course, use this web site...

- Jorgen

[shripadtokekar]

Thank you Dr. Jorgen
i will try to learn the things and code my subroutine. Actually i m biginer in FE field. i also want to know that can i delete my element without any subroutine in abaqus explicit according to failure stress?? or or that purpose aslo i need to write VUMAT?? thank you

[Jorgen]

Yes, you can active element deletion in Abaqus/Explicit without using an VUMAT. All you need is to use the failure / damage functions.

- Jorgen

[shripadtokekar]

thanx sir for ur information
sir u mean i can delete my element by using hashins damage model.......
all that i can give all the parameters through user graphics interface? and damage or failure in this case is energy based?? if i dont have that data and if i need to only predict the failure by stresses then shall i go for VUMAT??
thank you

[Jorgen]

In don't recall exactly which failure models are built-in, check out the manuals to find out. You can use the built-in failure models without any VUMAT coding :)