Search
Close this search box.
Notifications
Clear all

User element and constitutive tensor

14 Posts
3 Users
0 Likes
975 Views
Posts: 42
Topic starter
(@aas0092)
Eminent Member
Joined: 16 years ago

Found an example

Just wanted to say that I have found an example of a case where uhyper and umat are used in the same file. It actually very simple. 😎

It is the umathrt3.f file in the Abaqus documentation.

It works just as any other subroutines do, just in series, and in the same file.

Davinci

Reply
Posts: 80
(@FrankMonkey)
Trusted Member
Joined: 15 years ago

UMAT combined with UEL

Hello,

I would like to remind you:

26.15 User-defined elements

Material definitions (Material data definition, Section 16.1.2) are not relevant to user-defined

element types. For general user elements all material behavior must be defined in subroutine UEL, based

on user-defined material constants and on solution-dependent state variables associated with the element

and calculated in subroutine UEL.

This is the only advice I can give you. I couldnt excavate a single

example explaining how this is done.

Frank

Reply
Posts: 42
Topic starter
(@aas0092)
Eminent Member
Joined: 16 years ago

User element and applied force

Hi everyone

I have created a 3D 8-noded user element.

I am running a single element displacement test.

[B]Why is it that I can apply a displacement boundary condition, but not a force?[/B]

When I try to use a force, I get the error message:

***WARNING: ELEMENT 5 INSTANCE PART-1-1 CANNOT BE USED AS AN UNDERLYING

ELEMENT TO DEFINE A SURFACE IN THIS CURRENT VERSION. THIS ELEMENT

WILL NOT BE CONSIDERED AS PART OF THIS SURFACE.

Please advise.

Kind Regards

Davinci

Reply
Posts: 3998
(@jorgen)
Member
Joined: 5 years ago

It should work also with a force boundary condition.

I must say, however, that the error message you listed is quite odd.

I am not sure how to interpret it 😮

Reply
Posts: 42
Topic starter
(@aas0092)
Eminent Member
Joined: 16 years ago

Hi the error message is from a cook membrane test with the UEL.

There were 8 elements in total, 4 of which had a shear force applied to one surface, and they each gave the error stated before.

If I changed the shear force to a shear displacement, it worked.

But this is not the way the standard cook membrane test should be performed.

Reply
Posts: 42
Topic starter
(@aas0092)
Eminent Member
Joined: 16 years ago

To answer my own question:

Forces can be applied directly to nodes in UELs, however pressures cannot be used as surfaces are not allowed/defined for UELs fro some reason. (as I understand it)

Anybody know how to get around this?

Reply
Posts: 3998
(@jorgen)
Member
Joined: 5 years ago

I afraid that I dont have a good answer to that.
Anyone else with suggestions?

-Jorgen

Reply
Page 2 / 2
Share: