Creo Simulate - Contact surfaces expanding

[dsx2]

Hi guys,

Im trying to model a 4 point bending rig in Creo Simulate 4.0 and am running into issues.

Firstly, the rollers are defined as contact surfaces to the sample and base.

If i let the roller supports move in the x and y direction, the rollers actually expand when i simulate, instead of moving, keeping contact with all the surfaces.

If i let the roller move only in y direction, i do not get expansion, however the rollers still keep in contact with surfaces.

The forse present (0.5kN on tungsten) are no where near high enough to cause deformation.

The roller contrains are not defined in assembly, they are defined as 3D contacts in 
mechanisms and then dragged into place

I really don't know what to do about this.

Cheers

[ehaenen]

Hello dsx

Several issues at play here.

First: If you perform a normal linear analysis, small displacements, a rotation of a body will look like inflation when you exaggerate the deformation. Imagine displacement along a tangent to the cylinder. If you scale that, the cylinder wil "grow". You could live with that, maybe keep the deformation  scale at 1.0 but the right solution is: perform a large deformation analysis.

In the linear case, all loads and contacts are applied at what is the original undeformed shape. When something actually moves, or deflects significantly, you need large deformation analysis.

You also require output in several (many) steps. in any case, keep deformation scale at 1.0 (otherwise in contact analysis objecty appear to move through each other).

I do not know exactly the consequence of your modeling approach "they are defined as 3D contacts in 
mechanisms and then dragged into place"

I would see to it that the rtolers are constrained in some sort of form to prevent them flying away to the sides (singularity) and define contact in structure.

Below is a video of an example with really lartge deformations (no contact). There is no expansion here.

Good luck

erik