Making multipass welding simulations more robust

I am running multipass welding simulations. In the second or later welding steps, I frequently run into trouble with large deformations and elements turning inside-out, especially in the previous welding beads and the component material below the welding. Cause is obviously the low flow stress of the material at high temperature. Any good ideas for strategies on how to prevent simulations from crashing? Element deletion works, but the results are not satisfactory regarding stress results (see the image for an example).

0 QW over 1 year ago

Hi Koen,

We would first discourage you from the element deletion, as these often lead to other problems.

To avoid inside-out elements one should always check the reached peak temperature in the simulation and compare it to the real data. If there is a large deviation inbetween, you have to adjust the heat source dimensions or efficiency etc. first to make them match each other. This is so-called the calibration of the heat source and should always be done in a purely thermal simulation. After the heat source is calibrated, you can switch to a thermomechanical simulation to evaluate the distortions and other results.

Please find in the attachment a tutorial about how to do the calibration based on some examples.

Best regards,

Qi Wang

Attached Files (1)

Heat_source_calibration_2022_public.pdf
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0 koen.freytag over 1 year ago

The peak temperatures in the simulation seem fine to me. I do not understand what this has to do with avoiding inside-out elements, is this not rather a problem caused by the stress calculations? Can you explain what I should look for in the thermal simulation?
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0 QW over 1 year ago

Hi Koen,

Because the mechanical calculation is actually based on the thermal calculation. With the calculated temperature we use the material data at that temperature to calculate the stresses. In the thermal simulation one should ensure that the reached peak temperature is realistic (we recommend a value about 1.5 times of melting temperature of the material). Normally the inside-out elements are due to the too high temperature since the flow stress of the material is lower as you already known. By a heat source calibration you can check your temperature in advance without causing distortion.

If your peak temperature is fine, I would have to take a look at your model to find out what the exact problem is. Please send a test model with this problem to our support support@simufact.de and I will get back to you soon.

Best regards,

Qi Wang
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