Both the 2D and the 3D program allow for input of volumetric strain in x,y and z direction. Alternatively you may directly specify a volumetric strain (εvol) which basically means that the specified strain is equally distributed in x,y and z direction, i.e. εxx = εyy = εzz = εvol / 3.
When applying a volumetric strain to a cluster the following procedure is followed:
So realise that the stiffness ratio between the cluster with volumetric strain and its surrounding clusters determines the final deformations and stress levels.
In example: let’s assume a cluster with stiffness E1 which has a certain applied volumetric strain and the surrounding clusters with stiffness E2 with no applied volumetric strain.
Now for the following cases we find: