Metallic sandwich panels subject to underwater blast respond in a manner dependent on the relative time scales for core crushing and water cavitation. This article examines the response at impulses representative of an (especially relevant) domain: wherein the water cavitates before the core crushes. Three core topologies (square honeycomb, I-core, and corrugated) have been used to address fundamental issues affecting panel design. Their ranking is based on three performance metrics: the back-face deflection, the tearing susceptibility of the faces, and the loads transmitted to the supports. The results are interpreted by comparing with analytic solutions based on a three-stage response model. In stage I, the wet face acquires its maximum velocity with some water attached. In stage II, the core crushes and all of the constituents (wet and dry face and core) converge onto a common velocity. In stage III, the panel deflects and deforms, dissipating its kinetic energy by plastic bending, stretching, shearing, and indentation. The results provide insight about three aspects of the response. (i) Two inherently different regimes have been elucidated, designated strong (STC) and soft (SOC), differentiated by a stage II/III time scale parameter. The best overall performance has been found for soft-core designs. (ii) The foregoing analytic models are found to underestimate the kinetic energy and, consequently, exaggerate the performance benefits. The discrepancy has been resolved by a more complete model for the fluid/structure interaction. (iii) The kinetic energy acquired at the end of the second stage accounts fully for the plastic dissipation occurring in the third stage, indicating that the additional momentum acquired after the end of the second stage does not affect panel performance.

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The Cold Lake heavy oil development is located in northeast Alberta, Canada. It began commercial operation in 1985 and uses a thermal recovery process called cyclic steam stimulation (CSS). During steaming cycles, the dilation and re-compaction that occur within the reservoir cause the overburden to deform much like the motion of flexing a thick telephone book. At weak overburden layers, shear slip plane(s) can form due to excessive shear stress overcoming the interlayer cohesion. Over multiple steaming/production cycles, the cyclic flexing and associated shear slip may lead to overburden casing fatigue failures. In this paper, a multi-scale geomechanics modeling methodology is presented to predict the onset of failure due to CSS-related ultra low cyclic fatigue (ULCF). The modeling methodology consists of: (i) converting geological data into a representative finite element model of a single or multiple CSS pads, (ii) constructing a near-well submodel that includes thermal cement and casing, and (iii) constructing a detailed casing and connection submodel to predict the ULCF life of a pipe body or connection. To predict the ULCF life of the casing and connection, an algorithm based on the concept of cyclic void growth is incorporated into the submodel. It provides the capability to predict the number of steam cycles to failure using the concepts of demand and capacity. This enables studying the effects of alternative steaming practices on overburden shear slip and casing/connection life. Based on the learning from the multi-scale modeling, it is found that shear displacements on a shear slip plane can be superimposed using a single-well solution. By applying steaming and production scaling functions, the shear slip can be determined at any location and time. Integration of the single-well solution with ULCF algorithm has facilitated development of a new software tool that can be used to manage CSS operations in Cold Lake.