ADD=WITH STRAIN Vs ADD=STRAIN FREE

[bocage]

Hi,

I'm trying to simulate a process of deposition of melted material onto a substrate, and study the evolution of stress and strain.
I'm using *Model change add to activate the successive elements, but I'm not sure if I should be using the option "with strain" or "strain free".
The manual says that you use "with strain" if you want the elements to be strained at the moment of activation, but what strain is that?
When should you use one or the other? Any good example to illustrate the situation?
Thank you

To

 

[xerf]

Your decision should depend on the physical phenomenon you are trying to simulate.

 

[Cansand]

There are two options that can be used for adding the removed elements in
subsequent steps:

*MODEL CHANGE, ADD=STRAIN FREE
*MODEL CHANGE, ADD=WITH STRAIN

The first option activates the elements strain-free and is appropriate ,for example, for modeling the placement of the second layer of a structure being built in a staged construction manner e.g embankment. The second option can
be used, for example, for reassembling a disassembled assembly

 

[bocage]

Hi Xerf,

I'm modelling the deposition of molten material on top of a substrate. I assume that the material is added at the melting temperature, so, neglecting solidification, I would like to have a strain free set of elements which is activated at melting temperature and will cool down to room temperature, generating thermal stresses due to temperature gradients between substrate and molten material.
My problem is that, prior to element activation, the substrate has undergone thermal expansion as well, so it will expand and the contacting nodes between substrate and new elements will have changed position. If I add the new elements "strain free", they get "shrinked" due to this shift of some of their nodes. If I add them "with strain", they become inflated for no apparent reason. For instance, if I activate a 1*1*1 cube, in increment 0, it's activated correctly, but in increment 1 it will deform (is that the "with strain" effect) into something with a much larger volume, like 15 times larger. This cannot be due to thermal expansion, because at melting temperature it should expand much less than that...
Any idea?