how can use Vumat to simulate the ductile fracture criterion of Oyane

[ductoan_bkct@yahoo.com]

Dear Dr. Jorgen Bergstrom and everybody

I have just studied Abaqus and would like to use Vumat to simulate the ductile fracture criterion of Oyane which have the equation: I=(1/b)*integral(0-fracture strain) of (mean stress/Smises stress + a)*d(strain), where a, b is testing parameters. The fracture will be appear when I reach 1 unit.
Could you please show me how to write algorithm to calculate (I) and out put (I) in Vumat.

thanks you so much

I am looking forward to hearing from you

Nguyen Duc Toan

[Jorgen]

The new version of Abaqus that just came out (v6.8) has a new user subroutine called VUSDFLD. This subroutine allows you to define a user-defined field variable at integration points. You can then use this field variable to directly degrade the material properties in the input file, or you can use the field variable to trigger failure within a VUMAT.

It should be possible to calculate your specific fracture criterion if you use an internal state variable.

I am curios, where did this fracture criterion come from? Do you have a reference? What material are you interested in using it for?

- Jorgen

[ductoan_bkct@yahoo.com]

Dear Dr. Jorgen Bergstrom

Thanks you for replying. I am trying to study UVMAT and apply subroutine for ABAQUS, Beside that I am using ABAQUS 6.5. So I couldn't use your suggetion about ABAQUS v6.8.

This criterion com from: M. Oyane, T. Sato, K. Okimoto and S. Shima. J. Mech. Work. Technol. 4 (1980), pp. 65–81. There are alot of application to simutle fracture. Here, I used aluminum material.

I also link to one of paper using this criterion:
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TGJ-41M9FXX-2M&_user=178164&_coverDate=08%2F30%2F1999&_alid=753413353&_rdoc=2&_fmt=high&_orig=search&_cdi=5256&_sort=d&_docanchor=&view=c&_ct=2&_acct=C000013158&_version=1&_urlVersion=0&_userid=178164&md5=13a371a1f173c7e663ac2210571fe34e

If you can solve this problem, please infrom me!

Thanks you so much

Nguyen Duc Toan

[Jorgen]

First v6.5 is rather old. I recommend that you switch to the latest version (v6.8).

If you are stuck with v6.5, then you can still implement that failure condition directly into a VUMAT subroutine. You need to be aware, however, that writing a VUMAT takes, as the Abaqus manuals says it: "requires considerable expertise." I have to agree with that statement.

- Jorgen

[ductoan_bkct@yahoo.com]

Dear Dr. Jorgen Bergstrom

Thanks for your recommendation.
I will try my best to study how to using ABAQUS and VUMAT subrountine.
If you have some sample files (*.inp and *.for ) which show how to output SDVs from VUMAT subroutine and display in ABAQUS, Could you please send to me? I am very thankful for your help.

Nguyen Duc Toan

[Jorgen]

Here's an example (http://polymerfem.com/forums/showthread.php?t=42) for how to write an Abaqus VUMAT.

Best of luck,
Jorgen

[vincejebsen]

that's the one i was looking for. thanks Jorgen. :D