Why do we prefer to have Solid elements in Foams with Elform 1 instead of 2 ? - LSdyna Related

Elform 2 is a fully integrated model, so there is a tendency for negative volume in soft materials due to crushing. Elform 1 is a single integration model. As the integration point is in the middle of the element, even if the crossing over of nodes of one edge over the other may cause a physical negative volume but for all calculations it is possible that the centre node of the element is still on the +ve side and hence negative volume will be avoided. In case of excessive compression or warping, this may also become a negative volume.