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EDUARDO AMARO CALDERON

Rigid body penetration into rigid wall

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Hi,

 

I am not sure if it is possible to make contact between a rigid body and rigid wall work due to incompatible kinematic conditions (see FAQ on this topic I have already shared with you).

As a workaround, instead of a rigid wall set up a meshed plane with a rigid body on it and a type 7 contact. Check the model attached:

rigid wall vs rigid.hm

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Hello, I could not see the model becasue I am using an ancient vertion of Hypermesh :( could you share the model using radioss or using an ancient vertion of hypermesh, please.

 

I followed your advice about setting a  plane but now a have this problem

 

NEGATIVE VOLUME OF TETRA

 

In the model checker tab

 

What can I do?

 

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In the model you shared there is a problem of deep penetrations when the rigid body on impactor comes into contact with rigid body on flat plate (representing rigid wall). Due to penalty contact formulation this leads to high penalty forces and stiffness, and consequently to a drop in time step. In case CST mass scaling is used there is no timestep drop but mass increase leading to error termination. This is a known issue of rigid body impact on another rigid body or on fixed nodes or on very stiff structures:

Interface Hints.pdf

 

There are possible remedies like gap increase which will allow the contact to work sooner, but this could lead to initial penetrations. Sometimes the physics of the problem involves large contact forces in which case timestep drop (or mass increase) is unavoidable. In such cases the simulation could be run in two steps, where mass scaling is used only until just before the rigid contact, and without mass scaling in the second step, allowing the timestep drop. 
I think the better modeling approach would be not to have a rigid body on the impactor, because it artificially stiffens the part and causes rigid to rigid contact difficulties.
 
The following topic might help to better understand contact issues:

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Glad to help.

 

The warning 762 informs that /SPMD setting is overridden by -nthread or -nt command in Solver run Manager.

This can be ignored and the model should be able to run.

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Hello @Hyperman

now I have this energy balance curves, I as understand when there are a lot of elements sliding and being crushed is normal to obtain high values of energy.

But is there a way to improve this energy balance?

I am using :

type 7 contact and 11

image.thumb.png.02fb65f9a48ecaae483283b877c51909.png

image.thumb.png.adebd5d2a3645ad515ae9b6a11c6b480.png

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Upon second look into your model, I noticed you have added a mass of  2.518e+07 with M-ADV0 element. The unit system declared in the header card is g, mm, ms. This means you have 25+ tonnes impact being attenuated by a 2.8 gram structure :lol: This is probably a mistake that is causing all the other problems.

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