When a surfactant-coated toothpick is inserted into a sumi film on the glycerol solution, fracture dynamics—known in Japan as sumi-wari—are triggered, forming a star-shaped pattern with multiple spikes. The number of spikes depends on the viscosity of the glycerol solution, increasing as the viscosity increases. We measured the properties of the sumi film using atomic force microscopy, which suggested that the average value of the stiffness of the film decreased as the viscosity of the solution increased. Based on the experimental results, we proposed a phenomenological model described by an overdamped equation of motion for particles coupled with breakable springs. The numerical simulations of this model reproduced star-shaped patterns similar to the experimental results. Moreover, the simulations suggested that the number of spikes and the time series of the characteristic pattern lengths depend on the spring constants. These findings are consistent with our experimental results when considering the correspondence between the spring constants in the model and the viscosity in our experiments. In the seminar, I will show the experimental results and the results obtained from our model in detail. This research is collaborated with L. Pauchard (FAST), L. Goehring ( Nottingham Trent Univ.), A. Kinoshita (Nara Women's Univ.) and H. Sakaguchi (Nihon Univ.).
Accès Salle des séminaires FAST-LPTMS (Bât. 530, salle C.120, 1er)