  In this paper, the dynamics of a system of a finite number of screw
dislocations is studied. Under the assumption of antiplane linear elasticity,
the two-dimensional dynamics is determined by the renormalised energy. The
interaction of one dislocation with the boundary and of two dislocations of
opposite Burgers moduli are analysed in detail and estimates on the collision
times are obtained. Some exactly solvable cases and numerical simulations show
agreement with the estimates obtained.
