PSI - Issue 82

Koji Uenishi et al. / Procedia Structural Integrity 82 (2026) 72–78 Uenishi et al. / Structural Integrity Procedia 00 (2026) 000–000

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wooden structures subjected to vertical shock, or even that of simpler wooden columns, has not been understood yet. Here, dynamic splitting of brittle solid specimens under vertical shock (impact) is studied where each specimen has one single or double vertical straight perforation lines with aligned straight small-scale cracks corresponding to grain in wood materials. The dynamic splitting under vertical shock may be relevant also to the very fundamental dynamic fracture of a wooden column in the vertical direction, i.e. wood chopping. 2. Dynamic splitting along a single or double straight perforation line(s) consisting of small-scale cracks The direction of wood grain is modeled via the orientation of preset small-scale cracks in the specimen, and fracture development in the grain direction is experimentally observed. Instead of circular holes aligned in a single or two straight line(s) usually assumed in the study on fracture behavior of perforated materials (e.g. Tokiyoshi et al., 2001; Dastjerdi et al. 2011; Ma et al., 2015; Lin et al., 2023; Peng et al., 2023; Wang et al., 2023), straight perforation lines of aligned straight small-scale cracks are considered here. Our previous experiments regarding the collective and individual mechanical behavior of straight small-scale cracks have shown, for example, that if a number of perforation lines are preset in a two-dimensional brittle polycarbonate specimen, fractures do not always follow one of the perforation lines, and they can easily jump to remote places and change propagation directions a b

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Fig. 1. Polycarbonate specimens (70 mm ´ 40 mm, thickness 2 mm) prepared for the dynamic fracture experiments, with (a) a single and (b) double straight perforation line(s) consisting of straight small-scale cracks (length 4 mm except for the notches (1mm)). The interval between each crack edge is 0.5 mm. Each specimen with an “axe” (cutter) is dropped onto a rigid plate where it is subjected to vertical dynamic impact from bottom. Then, the axe moves downwards along the perforation line, and fracture behavior is observed with a high-speed video camera.