The effects of localized deformation on melting processes in ice

Abstract Polycrystalline ice deformed in pure shear and in plane strain at approximately −1°C exhibited plastic flow, accommodated by intracrystalline slip and grain boundary migration. A film record of the plastic flow shows that deformation becomes localized along slip-lines that correspond to zones of high resolved shear stress. During this deformation melting occurs. While a simple calculation shows that more melt is present that can be explained by the mechanical energy input, the localization of this melting is closely related to the deformation. For example, melting is initiated along zones of high shear strain. We evaluate the possible reasons for the localization of this melting phenomenon in the ice by comparing microstructural observations on the distribution of melt in space and time with the distribution of shear strain in space and time in a numerical analogue to the experiment. The localized incompatibility of strain across grain boundaries, particularly at triple point junctions, is bound to create significant stresses in the vicinity of these boundaries and this leads to heating. From this we infer the likelihood of higher spot temperatures being realized at grain boundaries and in the zones of high shear strain. The energy concentration at these spots may help to overcome the energy barrier needed to initiate melting in the sample.