Birth and Death of Elements in LS-Dyna

[Николай Водяхин]

I'm modeling the reinforcement of a shear bolted joint (non-prestressed, i.e., non-frictional) using welds. The welds need to be applied when the bolts in the joint are loaded. In more detail: initially, there's a simple shear bolted joint. The joint is subjected to a load of, say, 5 tons. Then, under that load, welds need to be applied. I decided to try using the "birth" and "death" of elements to trigger the weld at the right moment of loading (for example, at those 5 tons). However, a question arose: the "birth" and "death" of elements function essentially resets the stiffness at the moment of death, and then, at the "birth" of an element, it activates its full parameter. But what happens to the deformations of the born element? They aren't reset? And if the calculation is based on a deformation model of the material, then failure will result due to fictitious deformation (the deformation accumulated while the elements are still  "death" ).

[l...@schwer.net]

Perhaps a more(?) direct approach would be to use a full restart?

 

Run 1 – apply loading to bolted joint.

 

Restart Run 2 – add weld elements and continue run to new equilibrium.

 

See the section RESTART INPUT DATA in the User Manual Volume I for details.                             --len

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[Николай Водяхин]

And if I unload an STL file of a deformed model and then apply welds to it, in this case, in addition to the deformation, will the stress be retained there or will they be reset to zero?

воскресенье, 9 ноября 2025 г. в 20:54:31 UTC+3, leonarder...@gmail.com:

[l...@schwer.net]

In a situation like this, it is easier for you to try the STL file rather than accept my guess at what might happen.     --len

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