Hello,

I want to use Hypoplastic Interface (Fric Subroutine) in my ABAQUS contact models. However, I don’t know how I can determine Virtual Shear Zone Thickness. It is the Parameter #24 in the FRIC subroutine Manual. Is there a simple rule of thumb to determine this parameter? Same question also goes for Surface Rougness Coefficient (Parameter #23).

Thanks.

Tags:
1. Hans Henning Stutz 6 years ago

Thank you for your post. The virtual shear zone thickness dependent on the charateristic length of the element. I would suggest in the first step that you use ds = 1.0. Please have in mind the virtual thickness is a critical parameter input for the hypoplastic interface model.

The shear zone thickness I took from the following reference:

Arnold, M. (2008). Application of the Intergranular Strain Concept to the Hypoplastic Modelling of Non-Adhesive Interfaces. In The 12th International Conference of International Association for Computer Methods and Advances in Geomechanics (IACMAG) (pp. 747–754).

and have a look about page 751. Arnold described the calibration procedure. In short:
The parameter kappa_r controls the evolution of shear stresses and the virtual interface thickness ds_v is a scalar for the displacements. The parameters can be obtained by back calculation. Arnold proposed to use two computations: 1. The first with kappa_r = 1 and ds_v = 1. The parameter kappa_r is then approximately the ratio between the peak shear strength and the peak shear strength. This kappa_r is used in the second run to scale the displacements, ds_v can then be chosen to fit the test data.

Regards,
Hans Henning

2. Hans Henning Stutz 6 years ago

Sorry, I forget two words in the last sentence:

• Mahmoud Hamed 5 years ago

Hello Dr. Hans
It is written in the PDF named ” Implementation of hypoplastic granular interface models using
FRIC subroutine ” exactly at ( 5 Trouble shooting ) that:

” 2D and axial-symmetric simulations:
The interface model is currently only available for 3D simulations”

To avoid the misunderstanding, do you mean that i can not use ( only) FRIC Subroutine if i will use axial-symmetric option but i can use it normaly for UMAT Subroutine ? or i can not overall use axial-symmetric option with any Subroutine ?

Mahmoud HAMED
3SR Laboratoire, université de grenoble alpes, FRANCE

• Hans Henning Stutz 5 years ago

Dear Mahmoud,

This means the subroutine (FRIC) can be only used in 3D simulations (no plane strain or axial symmetric).
I have a modified version, I will try to uploaded in the next week.

Best,
Hans

3. Mahmoud Hamed 5 years ago

Dear Prof. Hans

So, i will continue using UMAT Subroutine with axial-symmetric option because 3D simulation takes time.

I have another inaquire if you don’t mind, For UMAT subroutine in ABAQUS ( I downloaded it which belong to Prof. David Mašín), i should put Number of 22 Parameters for the Mechanical constants in order as mentioned in this Link :
https://web.natur.cuni.cz/uhigug/masin/plaxumat/node5.html

The question here, Should i also put the interface parameters ( From 23 to 26) mentioned in your PDF
( Implementation of hypoplastic granular interface models using FRIC subroutine ) to the UMAT subroutine? or parameters from 23 to 26 are only belong to FRIC subroutine ?

Thank you again for your help
Kind Regards,
Mahmoud HAMED

• Hans Henning Stutz 5 years ago

Dear Mahmoud,

If you only use the Umat in the Materials use only 22 parameters, if you use the Fric subroutine you should use 26.

Best regards,
Hans

• Naif Alsanabani 5 years ago

Dear Dr. Hans
I simulated soil in Abaqus by using hypoplastic model. currently, I tried to model block foundation on saturated sand, type of loading that subjected on the foundation is cyclic loads.
To obtain a homogenous model system, the interaction of structure-soil interface should be considered by using hypoplastic interface.
Could you provide me Fric of hypoplastic interface code please?

Best regards.
Naif Mohammed

• Hans Henning Stutz 5 years ago

Dear Naif,

Regards,
Hans Henning Stutz

4. Naif Alsanabani 5 years ago

Dear Dr. Hans
Thanks for your quick response and helping.

Best regards
Naif Mohammed