Crack formation in ice plates by thermal shock

Cracks were formed in the surface of smooth ice blocks by bringing them into contact with a second colder ice block. The temperature change within each block and the associated thermal stress were calculated. The ultimate strength of a smooth ice surface was found to be between 30 and 40 kg/cm[ 2]. The surface temperature shock necessary to produce this stress was about 6 degrees C. There was a marked preference for the cracks to form parallel to the basal and prismatic planes. Maximum depth of crack penetration was obtained with ice blocks made up of only one or two crystals with their C axis perpendicular to the surface. The minimum observed value for the strain energy release rate at crack arrest was calculated to be between 150 and 200 ergs/cm[2] for each cm[2] of new crack surface, indicating that for the crystallographic orientation and stress distribution of those experiments there was relatively little plastic deformation at the crack tip. The associated crack edge stress intensity factor was between 3.0 X 10[6] and 3.5 X 10[ 6] dynes cm[-3/2].Des fissures ont \ue9t\ue9 form\ue9es \ue0 la surface de blocs de glace lisses en mettant ces derniers en contact avec un block de glace plus froid. Les changements de temp\ue9rature \ue0 l'int\ue9 rieur de chaque bloc et les efforts thermiques associ\ue9s \ue0 ces changements ont \ue9t\ue9 calcul\ue9s. La r\ue9sistance ultime d' une lisse surface de glace variait entre 30 et 40 kg/cm[2]. Le choc thermique de surface n\ue9cessaire pour produire cet effort a \ue9t\ue9 d'environ 6 degr\ue9s C. Les fissures se sont g\ue9n\ue9 ralement form\ue9es parall\ue8lement aux plans prismatiques et \ue0 la face basale. Les fissures ayant la plus grande p\ue9n\ue9 tration ont \ue9t\ue9 obtenues avec des blocs de glace n'ayant qu' un ou deux cristaux et un axe C perpendiculaire \ue0 la surface. On a calcul\ue9 que la plus basse valeur observ\ue9e pour la vitesse de lib\ue9ration de l'\ue9nergie des efforts aux points d'arr\ueat des fissures variait entre 150 et 200 ergs/cm[ 2] pour chaque cm[2] de nouvelle surface de fissure. Ceci indique que pour l'orientation cristallographique et la distribution des efforts des exp\ue9riences faites il y avait relativement peu de d\ue9formation plastique \ue0 l'extr\ue9mit\ue9 des fissures. Le facteur d'intensit\ue9 des efforts au bord des fissures variait de 3.0 X 10[6] \ue0 3.5 X 10[6] dynes cm[-3/ 2].[-3/2].Peer reviewed: NoNRC publication: Ye