A free material surface which supported surface diffusion became unstable when put under external non-hydrostatic stress. Since the chemical potential on a stressed surface was greater within an indentation, small shape fluctuations developed because material preferentially diffused out of indentations. When the bulk of the material was purely elastic it was expected that this instability would run into a finite-time cusp singularity. It was shown here that this singularity was cured by plastic effects in the material, turning the singular solution to a normal crack.

Finite-Time Singularities in Surface-Diffusion Instabilities Cured by Plasticity. T.S.Lo, A.Pomyalov, I.Procaccia, J.Zylberg: Physical Review E, 2008, 78[2], 027101