A study of shrinkage crack patterns

Linehan, Kelly A. (1997) A study of shrinkage crack patterns. Masters thesis, Memorial University of Newfoundland.

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Abstract

Shrinkage crack patterns which develop in a layer of a drying slurry of Al$\sb2$O$\sb3$ powder and water are studied. The ways in which the pattern changes with the depth of the layer, with friction between the layer and the container, and with added impurities are described. A statistical analysis is given of how changes in these experimental conditions affect the lengthscale of the pattern, the junction angles between cracks, the nucleation sites of the cracks, and the number of sides of the polygons formed by the cracking process. The lengthscale of the pattern increases linearly with depth. Longer lengthscales are observed in patterns where the friction between the layer and its substrate is reduced which shows that friction is the main source of stress for fracture. Most crack junctions are perpendicular showing that crack junctions are formed primarily through intersections of new cracks with pre-existing ones. These results are compared with the recent results of Groisman and Kaplan.

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