PSI - Issue 61

Koji Uenishi et al. / Procedia Structural Integrity 61 (2024) 108–114 Uenishi et al. / Structural Integrity Procedia 00 (2024) 000 – 000

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differently. In this case, the static tensile strain is set at 0.028 that is equal to the static limit, and the impact velocity of the projectile is about 63 m/s. In Fig. 2(a), it is recognized that the fracture evolution consists of two stages as summarized in Fig. 2(b): (i) Upward nearly vertical prograde propagation of the primary fracture starting from a a

Primary fracture

0  s

20  s

40  s

Projectile

60  s

80  s

100  s

Secondary fracture

120  s

140  s

160  s

180  s

200  s

220  s

10 mm

b

ii

Tension

Merged

i

240  s

Projectile

Fig. 2. (a) Specimen with the same configuration (Fig. 1(a)) is used but now the uniaxial strain is set at the static limit level, 0.028, above which fracture extension occurs. The impact velocity of the projectile is some 63 m/s, with the time of impact being 0  s. Again, using the high-speed camera, the evolution of dynamic impact-induced fracture in the specimen is observed. (b) First, as in the previous case shown in Fig. 1(b)-(c), dynamic primary fracture depicted in red (i) is initiated at bottom near the point of impact and propagates upwards nearly vertically in a prograde manner, but it is arrested in the middle of the specimen. Then, another fracture, the secondary one indicated in light blue (ii), is initiated on the top free surface at a position away from the primary fracture and travels downwards along a perforation line dipping 45 degrees in a retrograde (reverse) fashion. The primary and secondary fractures are merged and the entire specimen is split into two.

position near the point of impact and arrested in the middle of the specimen, indicated in red; and (ii) Counterintuitive downward retrograde (reverse) secondary fracture initiated at some 120  s at a remote position on