PSI - Issue 13

Koji Uenishi et al. / Procedia Structural Integrity 13 (2018) 652–657 Uenishi et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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a

Stemming material ejected later by gas pressurization

Cracks in these rectangular areas emerge first

Main crack

Blast holes

Dummy holes

Widening of curved main crack

50 mm

b

Cracks in the rectangular areas

Blast holes

Stemming material ejected

Desired main crack being widened

Desired main crack

50 mm

Fig. 2. Fracture development in the specimens (top view) for the cases (a) IC-09/00 and (b) IC-10/00, recorded by the high-speed digital video camera at a frame rate of 50,000 frames/s. The initial grid spacing is 50 mm, and the time elapsed after the leftmost photograph is (a) 200, 600 and 1,800  s, and (b) 100, 200 and 1,000  s, respectively. Although a fracture criterion should be included for the analyses of the post-failure phase (technically already implemented in our numerical code) and for instance, experimentally observed dynamic fracture in a reinforced concrete beam by conventional, overcharge blasting can be well simulated utilizing the code with e.g. the maximum principal tensile stress fracture criterion (Uenishi et al., 2010), we must always keep in mind that our knowledge on real three dimensional dynamic phenomena and fracture criteria for moderate (non-overcharge) blasting (by detonating explosives or applying EDI) is still limited. Most of the widely employed fracture criteria have been derived from one- (or at most