Shaking-induced stress anisotropy in the memory effect of paste

Abstract

When paste of fine granular particles and water is shaken in one direction and then left undisturbed, memory of the direction of shaking is retained for a sufficiently long time to result in a directional crack pattern that appears after drying. Although it has been conjectured that anisotropy in residual stresses caused by plastic deformation is responsible for this memory effect, to this time, no evidence of such anisotropy has been found. We experimentally investigated the stress in drying paste by measuring the bending of elastic plates supporting the paste sample and found stress anisotropy developing in paste. Additional bending tests suggested that paste retains plasticity during the drying process and that plastic deformation is not always frozen in place after initial shaking.

Drying paint: from micro-scale dynamics to mechanical instabilities

“…1: Large-scale mechanical instabilities in dried colloidal materials can include (a) radial and spiral cracks in a blood droplet, (b) shear bands (diagonal features) and cracks (near-vertical lines) in a paint film, highlighted by viewing under crossed polarisers, and (c) the guiding of cracks in a calcium carbonate paste, that had been pre-treated by a brief rotational flow (see e.g. [21][22][23]). Image (a) courtesy of W. Turner and D. Fairhurst, and (c) courtesy of A. Nakahara.…”

Effects of Cage-Breaking Events in Single-File Diffusion on Elongation Correlation

“…This is reminiscent of the theory of elastoplasticity in terms of natural metric, 28 which may help to clarify the Nakahara-Matsuo memory effect in pastes 29 as a manifestation of stress anisotropy induced by shaking. 30 An extension of the present work in the direction of these studies on granular pastes [28][29][30] might be possible, if the change in C ε is related to the stress field in some way analogous to nonlinear interaction betweenψ and δΞ j .…”

Effect of disorder on shrinkage-induced fragmentation of a thin brittle layer

“…However, in the case of drying dense colloidal suspensions structural and strength disorder of the model may represent different scale heterogeneities caused, e.g., by an inherent initial deformation field imprinted in the paste layer by mechanical excitations and by the variation of the size of colloidal particles. The competition of these two effects has been found to play a key role in the emergence of the memory effect in desiccation-induced cracking of paste layers [1,6,7,12].…”

“…In colloidal suspensions the amount of disorder can be controlled, e.g., by varying the range and the functional form of the size distribution of colloid particles. Vibration and flow of pastes gives rise to well-ordered crack structures since the initial mechanical excitation imprints a directional or spatial distribution of density fluctuations and plastic deformation, which overcomes the effect of disorder in the local fracture strength for crack formation [10,12]. Hence, it is an interesting question how the competition of the structural heterogeneity and the disorder of the local fracture strength of the material determines the evolution of shrinkage-induced cracking and the size distribution of fragments.…”