Abstract
The effect of random stresses on a crystal undergoing a planar elastic instability is investigated using self-consistent mean-field theory. The results suggest that the stresses inhibit the transition and that long-range order is preserved. The scattering is calculated without using the phonon expansion and the results discussed. The effect of dislocation dipoles on the long-range order and scattering is evaluated and it is shown that if these are thermally excited long-range order is destroyed.