Item: Interfacial crack velocities in a snow slab – numerical simulation
Title: Interfacial crack velocities in a snow slab – numerical simulation
Proceedings: Proceedings of the 2006 International Snow Science Workshop, Telluride, Colorado
Authors: P. Mahajan and S. K. Joshi Department of Applied Mechanics Indian Institute of Technology Delhi, Hauz Khas, New Delhi - 110016, India
Abstract: A snow pack consists of weak layers embedded in strong layers. The interface bond between a weak layer and layers in between which it is sandwiched may not be strong and there may be regions that are not bonded. The un-bonded regions act as stress raisers from where propagation of crack can take place, in mode II, along the weak interface. The crack propagation along the interface under a shear and compressive load (due to the weight of skier) is studied using cohesive zone elements to describe the interface between the weak and strong layers. Four properties of the interface namely fracture energy in normal separation, fracture energy in shear separation, tensile and shear strengths are needed to characterize the cohesive elements. Tension and shear experiments on sieved snow with an ‘ice lens’ and shear experiments on field snow with a weak interface are performed to get an estimate of the cohesive zone properties. The cohesive model, incorporated in a finite element mesh, is used to determine the speed of crack growth along the interface. The average cracks speed depends on modulus of the layers on either side of interface and for the modulus values studied here, is between 40 m/s and 200 m/s.
Keywords: cohesive zone, dynamic crack growth, weak layer, snow, finite element
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