Objects Go Through Each Other - Is It Just Deformation Scale, or Is It a Bad Set Up?

[amirandaL4VAC]

Will objects inevitably go through each other at a certain deformation scale? I have 3 plates clamped together by bolt connectors with a preload. There are separation contacts between their faces. I'm not sure why with the separation contact, they'd still go through each other. Is this just a consequence of having too large of a deformation scale, or does this indicate that the analysis was improperly set up?

[John_Holtz · Accepted solution]

Hi @amirandaL4VAC.

The answer to this question, "Will objects inevitably go through each other at a certain deformation scale?", is Yes.

Separation contact is a spring. When the gap between the surfaces is 0, the force in the springs is 0. When the parts begin to penetrate mathematically, the contact force in the springs increase. Once the springs generate the force to resist the load, the penetration stops (but it still exists, mathematically). When you exaggerate the penetration by some large value, it appears the parts pass through each other. (This appears most often in a linear analysis where the default deformation scale is some value (10% of something) so that the small displacement can be seen.

You need to look at the results to determine if the penetration you see is due to exaggerating the displacement, or is it because something is wrong with the contact setup. You do this by:

• Don't exaggerate the displacements! View the displacements at an absolute value of 1 and see if there is penetration.
• Look at the displacement results and the values. Do the parts move the same distance? Or does one part move farther than the other and really penetrate (by more and 1E-6 or whatever penetration normally occurs).
• Look at the contact force. If there is a nonzero contact force in the nodes, the contact is working. If the contact force is 0, something is wrong.

John