[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
## Re: [Getfem-users] Plasticity brick

**From**: |
Yves Renard |

**Subject**: |
Re: [Getfem-users] Plasticity brick |

**Date**: |
Mon, 24 Sep 2012 15:16:02 +0200 |

**User-agent**: |
Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120827 Thunderbird/15.0 |

Dear Kostas,
This behavior is not intentional. In fact the elastic threshold s in the
brick is taken to be |\sigma^{dev}| and thus it represent \sqrt{2/3}
\sigma_{vm} ...
I agree that it would be clearer if the elastic threshold would be
expressed in term of Von Mises stress. This can be changed.
Yves.
Le 21/09/2012 16:03, logari81 a écrit :
>* Hi all,*
>
>* I have recently worked with the elastoplasticity brick and I have one*
>* relevant comment.*
>
>* As a scalar measure of stress one can use either the euclidean norm of*
>* deviatoric sigma or the Von Mises stress. The difference is an*
>* sqrt(3/2) factor:*
>
>* $\sigma_{vm} = \sqrt{3/2} |\sigma^{dev}|$*
>
>* In getfem, |\sigma^{dev}| is used through the whole brick*
>* implementation except one point. Only in the stresses calculated by*
>* compute_elastoplasticity_Von_Mises_or_Tresca the result is multiplied*
>* by sqrt(3/2).*
>
>* The stresses calculated by "compute_plastic_part" and the input*
>* parameter "datathreshold" do not include the sqrt(3/2) factor. So the*
>* user of the brick has to divide the tensile yield strength \sigma_y by*
>* sqrt(3/2) before assigning it to "datathreshold" and he also has to*
>* multiply the results of "compute_plastic_part" with the same factor in*
>* order to receive stresses comparable to the Von Mises definition.*
>
>* Is this behavior intentional? Wouldn't it be more consistent to either*
>* remove the factor from "compute_elastoplasticity_Von_Mises_or_Tresca"*
>* or add it to "compute_plastic_part" and "datathreshold"?*
>
>* Best regards*
>
>* Kostas*
>
>* _______________________________________________*
>* Getfem-users mailing list*
>* address@hidden*
>* https://mail.gna.org/listinfo/getfem-users*
--
Yves Renard (address@hidden) tel : (33) 04.72.43.87.08
Pole de Mathematiques, INSA-Lyon fax : (33) 04.72.43.85.29
20, rue Albert Einstein
69621 Villeurbanne Cedex, FRANCE
http://math.univ-lyon1.fr/~renard
---------