Creep and Fracture Simulation of Ice using the Finite Element Method

Abstract

<p>A review of fracture mechanics, fracture toughness and creep behavior of ice is presented. An expression for evaluating the energy releases rate (J-integral) for fracture of ice under creep is developed and incorporated in the finite element program for implicit, incremental, non-linear creep analysis.</p> <p>It is assumed that the energy release rate due to fracture of ice at any creep stage is dependent on the recoverable strain energy and not affected by the non-recoverable work done during creep. A zone classification of the finite element mesh around the crack tip and the equivalent elastic displacements for the stress state at a given creep stage are used to compute the fracture toughness of ice. This is then compared with the prescibeed values of K(ic) (the crack initiation fracture toughness) or K(ia) (the crack arrest fracture toughness) for either the crack initiation or crack propogation, respectively.</p> <p>Two examples are analyzed using the method mentioned above.</p> <p>(i) A rectangular plate with symmetric edge cracks, under plane strain and subjected to uniform tension.</p> <p>(ii) A double slope ice mass with uniform thickness, and an initial crack at the knee, subjected to gravity load.</p> <p>It is assumed that the crack path is predetermined and the crack opening is of mode type I. In both examples the displacements, redistribution of stress around the crack tip and the stress intensity factors are computed at various creep stages. For the double slope example, K(i) is compared with K(ic) or K(ia) and the knee crack is propagated through a finite extension accordingly. Finally, the effect of varying the two slope angles on the stress intensity factor and crack propagation for the double slope example is investigated and was found to be sensitive to the difference between the two slope angles.</p>