Brittle to ductile transition during indentation of ice

Abstract

The brittle to ductile transition in the deformation behaviour of ice is considered for indentation by a flat, rigid indentor under fully elastic plane strain or plane stress conditions. It is assumed that failure occurs when a crack initiated near an edge of the indentor is propagated immediately by the maximum shear stress at the site. Consideration is given to the relaxation of the elastic moduli and the change in the critical stress intensity factor for crack propagation that occur in the transition range of strain rates. The analysis shows that for the assumed conditions, the indentation pressure varies inversely with the square root of the width of the indentor, and increases to a maximum with decreasing strain rate. It also indicates that the necessary and sufficient conditions for brittle failure of ice are a critical combination of shear strain and strain rate that will cause a crack to form, which propagates immediately under the imposed stress. Key words: ice, elasticity, indentation, brittle to ductile transition, fracture mechanics, failure.