SIMULATION: Resolve Contact Set for Bodies That Overlap

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Have you ever seen bodies pass through each other in SOLIDWORKS Simulation? You cannot always easily observe overlapping behavior. This depends on if deformed result display is used and, if so, which deformation scale is selected. In the example below I created a multi-body part, fixed the 2 rectangular parts in place, and added a horizontal load at the end of the L-shaped part. I bonded the smaller rectangle body which acts as the support for the L-shaped body. To be clear, the parts do not overlap before the study is ran.

solidworks simulation multi body part

The L-shaped body is bonded to body 1 but not bonded to body 2 in the image below. You cannot observe the missing bond when deformed result display is turned off.

What is deformed result?

Refer to the image below for an example of what it looks like when deformed result display is turned on. I do recommend that deformed result be turned on when viewing simulation result plots.

You can clearly see that body 2 is not bonded in the image below. Select “automatic” under the deformation scale of the stress plot definition and ensure that the deformed result display option is turned.

 

Warning signs for overlapping bodies?

Take note of the deformation scale because it could be a clue to the behavior in your model. For example, when deformation scale is high (usually 100 or more could be considered high) then the parts overlapping might not be passing through each other. They appear so due to the highly exaggerated deformation. If the bodies are passing through each other then check for stress concentrations of the bodies. If, like above, the stress is zero where the bodies overlap, then you most likely have an improperly setup contact set.

Identifying the issue is important, but it leads us to the next question. Why is this happening? This commonly happens when there is a gap between bodies. In some cases an incompatible mesh can cause this issue. An incompatible mesh describes the condition when nodes do not line up because one of the faces has a larger mesh than the other.

How to correct the overlap?

Create a local contact set applied between the two bodies that are overlapping in the result plot, then apply a local contact set between faces of the two bodies. If a local contact set does not correct the overlapping issue then the next step is apply a mesh control on one of the contacting faces. In this case, apply the mesh control to the face in the blue selection box. The blue box is called the source and the pink the target. For the best result, a denser mesh is preferred on the blue(source) face.

This face is highlighted in the model to help you identify the correct face. You know you have successfully applied this bonded contact when you see a stress concentration in the contacting body.

Matthew Fetke, Computer Aided Technology
www.cati.com