PSI - Issue 61

119 5

Koji Uenishi et al. / Procedia Structural Integrity 61 (2024) 115–121 Uenishi and Kato / Structural Integrity Procedia 00 (2024) 000 – 000

a

b

10 mm

First impact

Stress transfer

Second impact

Highly unstable area

Fig. 3. (a) Particle movement at a shorter interval for the second experiment with double impacts (Fig. 1(b)). (b) Difference of colors between the photographs before and after the first impact suggests the important role of lines of unidirectional stress transfer. Here, there seem to exist at least four lines of stress transfer and the particles above the two neighboring lines enter a highly unstable state, and large movement and buckling-like jump become more easily possible. The elapsed time after the impact is, from top to bottom, 300, 600, 900, 5,400, 5,700 or 6,000  s.