2015 Volume 70 Issue 3 Pages 179-187
Desiccation cracks are familiar phenomena producible by drying a mixture of water and colloidal particles of a few microns in diameter. When the mixture is so dense that it has plasticity, it is called a paste. Here we show that, using memory effect of pastes, we can predetermine the morphology of the cracks so that the desiccation crack pattern becomes strikingly anisotropic. By the word "memory" we mean that mechanical treatment (such as "vibration" or "flow") applied to the paste, before the drying process starts, is somehow imprinted in the paste and determines how the cracks should be formed later. It is demonstrated experimentally that plasticity is essential to the memory effect. There are at least two types of memory effects: the first type is referred to as the memory of vibration, and the second type as the memory of flow. A possible theoretical clarification of the memory of vibration is given by the so-called residual tension theory, in which plastic deformations of an elasto-plastic fluid layer, associated with residual tension, account for the anisotropic crack pattern.