Memory effect on the formation of drying cracks

TL;DR

This paper presents a model explaining how pre-drying external forces induce plastic deformation in viscoplastic materials, affecting crack formation patterns during drying, with analytical predictions of crack positions based on force strength.

Contribution

It introduces a theoretical model linking pre-drying forces to crack patterns, providing analytical expressions and predicting a force threshold influencing crack positions.

Findings

Crack position depends on pre-drying force strength.

A threshold force determines crack location shift.

Crack deviation increases linearly with force beyond threshold.

Abstract

We propose a model for the formation of drying cracks in a viscoplastic material. In this model, we observe that when an external force is applied to a viscoplastic material before drying, the material memorizes the effect of the force as a plastic deformation. The formation of the drying cracks is influenced by this plastic deformation. This outcome clarifies the result of a recent experiments which demonstrated that a drying fracture pattern on a powder-water mixture depends on the manner in which an external force is applied before drying. We analytically express the position of the first crack as a function of the strength of an external force applied before drying. From the expression, we predict that there exists a threshold on the strength of the force. When the force applied is smaller than the threshold, the first crack is formed at the center of the mixture; however, when the force applied exceeds the threshold, the position of the first crack deviates from the center. The extent of the deviation increases as a linear function of the difference between the strength of the force and the threshold.