UFIELD subroutine

[shripadtokekar]

Hi sir
i have one question regarding this subroutine can i use this subroutin for simulating the failure criteria?? as one example is abaqus on composites uses this subroutine. may i know how we can relate the field variable on material properties??

[Jorgen]

The USDFLD subroutine is available only for ABAQUS/Standard and not Explicit, and since Standard does not support element deletion it is more difficult to simulate progressive failure in implicit simulations using ABAQUS. Furthermore, I am not sure if you can connect the user field to a failure condition. I suspect that you cannot do that.

Anyone else know for sure?

- Jorgen

[shripadtokekar]

Thanks Dr. Jorgen
for your reply. actualy in ABAQUS problems manual one example of damage of composite plates is there their they have used three user defined field variable. one field variable is directly assigned to the damage parameter and other two are changed according to failure criteria they have specified, if field variable is 1 the properties goes zero. whther i can use this logic to my problem. for simulating failure criteria. ??

[chindan]

If you are making your properties to zero namely the stiffness please make sure you reduce the stiffness to 1% the original value. Otherwise due to numerical instabilities you would have problems with your UMAT. You can refer to a paper of where they have mentioned reducing the stiffness to a low non zero value.

Wang, J., Callus, P.J. and Bannister, M.K, “Experimental and numerical investigation of the tension and compression strength of un-notched and notched quasi-isotropic laminates” Composites Structures. Vol. 64 (2004) 297 – 306.

Best regards,

[shripadtokekar]

Thanx sir for ur advice..........