PSI - Issue 32

A.M. Ignatova et al. / Procedia Structural Integrity 32 (2021) 79–86 Author name / StructuralIntegrity Procedia 00 (2019) 000 – 000

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product ImageJ-FiJi (Analyze Particles module). The following parameters of destruction fragments have been evaluated: Feret equivalent diameter (D f ), sphericity coefficient (C sph ) and convexity coefficient (C con ) (Ignatova A.M., 2015). Statistical significance of differences between parameters of destruction fragments has been established using the method of Fisher criterion (F-criterion) at a significance level of 0.05. 3. Mica-crystalline material fragmentation conditions The study of potassium fluorphlogopite destruction including identification of parameters of destruction fragments was implemented using a pneumatic acceleration unit (fig. 3)( Ignatova A.M., 2015). Acceleration of the projectile (steel ball) was performed using an acceleration pipe with an inner diameter of 25 mm and length 3950 mm, and a telescopic punch inserter. Acceleration of the ball projectile was performed using pneumatic equipment - a 5.2 L pump with a high pressure receiver. The receiver was filled with compressed air using a high pressure compressor. Ball velocity was registered using a measurement system based on capture of time when the impactor crosses the control section of the movement trajectory limited by a net of laser beams in the beginning and end of the trajectory. Flat plate 280х160х15 mm samples were used (including 70 mm surface for fixing in the test unit’s holder). For better visibility of the experiment results, the samples were coated with white water emulsion compound and lined with measurement grid with 10×10 mm cell size.

Fig. 3. Pneumatic acceleration unit.

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b

Fig. 4. Samples installed in the holder of the pneumatic acceleration unit: ( а ) non-constrained, (b) constrained.

Two types of impact have been implemented: in non-constrained (I) and constrained (II) conditions. Impact condition (I). Potassium fluorphlogopite sample was fixed in the holder of the test unit so that only one of its ends was rigidly fixed, and other edges were unconstrained, therefore no lateral compression was present (fig. 4, а).