[O-08] Kitchen Earth Science: its potential for producing diverse goals by hands-on experiments

[O08-P08] Plumose pattern on fracture surfaces of drying pastes

★Invited Papers

*Sakaguchi Hidetsugu, Michiko Shimokawa¹ (1.Nara Women’s University)

Keywords:drying fracture, Pattern on fracture surface, discontinuous progress of cracks, mathematical model

Random polygonal crack patterns occur at the bottom of dry dams and in rice fields. Such crack patterns also occur when a paste made from water and cornstarch in the kitchen dries. A plumose-like pattern often appears on the fractured surface of these cracks. Here, when vibration is applied to a paste of calcium carbonate, cracks develop in a direction perpendicular to the direction of vibration. We report the results of our observation of the progression of these cracks. Unlike the fracture of glass, the crack progresses slowly and can be followed with the naked eye. Before a crack forms, a slight indentation appears on the surface of the paste, and a crack appears from the bottom of the indentation. The position of the dent can be used to predict the position of the crack a little further down the line. If the position of the dent deviates from the tip of the crack, a discontinuity in the crack occurs. Although the cause of the plumose pattern formation has not yet been undersood, it might be related to the discontinuity of the crack. We will report our numerical simulation of a mathematical model, where a plumose-like pattern appears due to the occasional lateral jumps of the crack surface .