PSI - Issue 61

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

117

3

a

b

10 mm

Single impact by a steel ball

First impact

Photoelastic particle

Second impact

Buckling-like jump

Large movement inside this area due to the second impact

No particle movement inside this area

Relatively large movement

Fig. 1. Experimentally obtained photographs showing the particle motion and isochromatic fringe patterns inside the particle in a two dimensional granular medium subjected to (a) single and (b) double impact loads. Each dynamic impact is given by a free-falling steel ball (sphere of diameter 30 mm, mass 110.3 grams, impact velocity 1.43 m/s). In (b), the delayed second impact is given 5.4 milliseconds (ms) after the first one with a horizontal distance of 96 mm. In both (a) and (b), mechanically stable and unstable areas can be identified. From top to bottom, photographs are taken at 0, 6, 12, 18 and 24 ms after the first impact.