PSI - Issue 47

Irina A. Bannikova et al. / Procedia Structural Integrity 47 (2023) 602–607 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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material as a function of load energy near some critical point by Astrom et al. (2004), Katsuragi et al. (2003) and Katsuragi et al. (2004), which corresponds to the transition from a material with damage to a fragmented material. The statistical laws of fragmentation are explained by the main aspects of fracture related to the nature of singularities typical of critical phenomena, which in case of fracture are accompanied by nucleation of defects and their multiscale interaction leading to the nucleation and growth of cracks by Davydova et al. (2014), Davydova et al. (2016) and Naimark (2016). With regard to fragmentation, this manifests itself in a qualitative change of statistical distributions of fragments in size (mass) depending on the material structure and the intensity of loading. Empirically determined statistical laws of fragmentation are mainly described by exponential, lognormal and power distributions. Experimental investigation of fragmentation of ceramics and natural materials (quartzite, quartz, sandstone) quasi static, dynamic and shock-wave loading was conducted using high-speed video imaging and photomultipliers (PMT) for fractoluminescence recording to establish the relation between defect, induced multiscale mechanisms of structural relaxation and scaling laws of fragmentation.

Nomenclature EEW electric explosion wire DL dynamic loading QSL quasistatic loading d*

characteristic size of fragment

d T

tube thickness

h d

an average height sample an average diameter specimen

N m

number of fragments with mass greater than some given value

mass of fragments sample density

ρ

N t

number of intervals time greater than some specified

t imp

time intervals between pulses of the entire signal of fractoluminescence

PMT

photomultiplier

2. Samples. Loading methods The samples (ceramic tubes on the basis of Al 2 O 3 ; quartzite, quartz, sandstone had the form of a cylinders) and their parameters are presented in Fig. 1 and in Table 1, respectively. Dynamic loading of the samples was carried out on the Hopkinson Kolsky bar setup by Davydova and Uvarov (2013). Quasi-static loading was conducted on electromechanical universal testing machine Shimadzu AGX-Plus with Shimadzu application "TRAPEZIUMX". Shock-wave loading was realized on electric thin wire explosion (EEW) machine. See Table 1.

Fig. 1. Samples for testing. (a) ceramics, Al 2 O 3 ; (b) quartzite and (c) quartz; (d) sandstone.