Learning Forum

[WEI WU]

Hello everyone, I'm having problems with the electro-thermal coupling simulation for resistance spot welding:

 

After setting the ambient temperature to 21 degrees, the model shows an abnormal temperature decrease, with the low temperature areas concentrated in the contact area and edges of the sheets. 

The element I'm using is solid226 without mid nodes (the temperature undershoot problem seems to be caused by mid nodes?).

 

Does anyone perhaps know what is causing that please? It has been bothering me for a long time, thanks a lot!

 

The temperature results are as follows：

Mesh of the sheet:

[dlooman]

You're right, the main reason for undershoot is thermal shock loading of higher order elements.  You could use solid225 instead of solid226 to avoid having to remove the mid-side nodes.  I have seen small points of undershoot like you describe in other cases, but they tend to be very local.  If you create more contours below 22 deg, you might find that the lowest temperature only exists at a few small points.  These are annoying, but I believe can be ignored.  They may be caused by small errors in the contact element results.

[WEI WU]

Thank you so much for your help！

I'm using version ANSYS18.2 and there seems to be no element solid225.

When the temperature doesn't drop too much(maybe 11 degre), I think I can ignore these small errors. But if I make more heat input, the temperature even drops below 0 degre. As you said they may caused by errors in the contact element results, so is the mesh in the contact area too sparse?

[mjmiddle]

You may want to look at knowledgebase solution 2055016.

https://support.ansys.com/KnowledgeResources/Solutions?solutionIdentifier=sol2055016

[dlooman]

That's quite an old release!  A few things to try are reducing the contact thermal conductance (manually specifying it), creating a mesh that is similar in size on both sides of the contact and specifying Detection Method to be "Nodal-Dual Shape Function Projection" or "Combined."  

[WEI WU]

Thank you very much! I'll try what you said. Wish I could fix it.