Contact type 7

Altair Forum User

Good afternoon,

I often find out that contatct type 7 drives the simulation to error due to negative or null time step.

Attached to this message there's a picture that shows what usually happend in this case: there's a rounded surface that grawls over an edge surface, the consequence is that the master surface grabs a node from the slave surface (or vice-versa) causing an eccessive deformation of an element of the mesh, so the time step becomes very small.

 

I'm I doing something wrong? Is there a way to improve the contact characteristics to avoid time step decrease?

Thanks for helping me

 

 

<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

Please provide IGap value while Type 7 interface is applied. If Igap is already provided, sligtly increase the value and see.

Because of unusual element deformation, the time step is dropping drastically in this case and it may finally end up in error after running  for a long time. Moreover please see the correct loading conditions (imposed / initial) are selected.

 

Please let us know whtr it worked / not

Altair Forum User

Silvia,

 

Does this model undergo self impact?

 

It is recommend to use a minimum Gap (GapMin) equal to atleast 0.5* minimum edge length of the element. If that doesn't help you can look at the option Irem_gap.

 

Altair Forum User

Well,

 

First of all I shall advance that I'm currently using release 12, I hope we'll soon be able to install version 14, but unfortunatelly it is not possible to use the option Irem_gap.The model doesn't undergo self impact. Anyway I used contact type 7 though the master surface is a rigid body surface made of steel and the slave set nodes is taken from a tetrahedron elements mesh made of PP

Due to your suggestions I changed the interface definition as follows:

 

contact

 #  Slav_id   Mast_id      Istf      Ithe      Igap                Ibag      Idel     Icurv      Iadm

                                                                            
         1        33         4                   2                                       1          
                                        

 #              Stmin               Stmax          %mesh_size               dtmin  Irem_gap

                                                                                                                        1.00000000000000E-08
         

 #              Stfac                Fric              Gapmin              Tstart               Tstop

                                     0.3                0.55                                        
               

Altair Forum User

Hi Silvia,

 

Was there any improvement after changing the parameters in Type7 interface?

 

If you still face the issue, please share the model to have a closer look.

 

use the dropbox link in my signature below to share the model.