Michael Atlas

Inconsistent Mesh with Global Bonded vs. Free in Non-Linear and between X64 and X32

Discussion created by Michael Atlas on May 29, 2008
Is this to be expected?

I have assemblies with contact in which I have defined local contact conditions for all of the faces that interact or are bonded.

Almost by accident I found that the models mesh differently (and run differently) depending on whether the Global Contact Condition is set to Free vs. Bonded or No Penetration and that they also mesh differently whether I mesh in SW2008 SP3.0 on X32 or X64.

I care because in some of my more complex models this is enough difference to make the model either run or not run at all (i.e. it sits at the first contact iteration forever trying to determine number of contact points).

To test this I loaded one of the tutorial models "Nl_Pipe_Holder" and meshed it both ways.

In SW2008 SP3.0 on X64, with Global set to Bonded and a default element size/tolerance of .12"/.006" I got 3619 elements.
With Global set to Free I got 3594 elements.

To make it worse, the model meshes differently when run an an XP32 machine where Bonded results in 3595 elements and Free gives 3597. (I've already reported this problem earlier and it was assigned SPR 435168)

From the attached screen dumps you can see that the contact surface of the "pipe" has meshed differently at the spot the two parts initially touch, even though a Local Contact Condition already specifies these faces as No Penetration.

According to the documentation the local conditions should override global conditions, so why does the global setting make a difference here?

When you run the analysis it is obvious that the No Penetration condition has won out as the parts can slide over each other.