Dislocations in two-dimensional liquid foams

In this analysis we make the analogy between the dislocations in metals and the behaviour of 2D liquid foams in the presence of external forces. It is shown that the edge defect which appears in metals can also be introduced in a similar manner in 2D liquid foams and that the motion of this defect through the foam can occur by the process of T1 transformations. The analogy leads to the motion of local cells as opposed to the motion of a row of cells. That is, the T1 process occurs ‘locally’ and the ‘defect’, primarily introduced here as an edge dislocation, can move through the whole 2D liquid foam through the local motion of these edge dislocations. These defects as in the theory of metals lead to the reduction of the critical stress required for the ‘slipping’ of the 2D liquid foam. Furthermore, since it is these defects which are responsible for the behaviour of the 2D liquid foam to external forces and since it will be the motion of these defects which is related to the motion of the cells, it is possible, again through the analogy with ‘slipping’ in metals to determine the strain rate. The result is given as strain rate = b V .