PSI - Issue 2_B

Yurii Meshcheryakov et al. / Procedia Structural Integrity 2 (2016) 477–484 481 Yu.I. Meshcheryakov, A,K. Divakov, N.I. Zhigach v , G.V. Konovalov/ St uctural Integrity Procedia 00 (2016) 000–000 5

100 120 140 160 180

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0 20 40 60 80

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free surface velocity, m/s

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500

1000 1500 2000 2500 3000

time, ns

Fig. 5. Free surface velocity profiles for the first (1) and second (2) kinds of gray iron.

The velocity profile for the second kind of gray iron is characterized by the presence of oscillations with the period of ~ 100 ns and amplitude of 10-13 m/s (Fig.5). Similar oscillations are absent at the time-resolved profile for the first kind of gray iron, which evidences the absence of local displacements of structural elements and provides much higher strength features of the material. In Fig. 6 the metallography of dynamic fracture for both kinds of gray iron is presented. The structure of gray iron consists of ferrite-perlite background with plane graffiti inclusions. Microstructure investigations of specimens after shock loading show that the first kind of gray iron which contains the greater percent of copper and titanium alloys has a much smaller density of cracks as compared to the second kind of gray iron. 2.3. Fused quartz . Results of shock tests of fused quartz for two impact velocities are provided in Table 4 and Figs. 7 and 8. In fused quartz the velocity variance also comes to zero at the end of shock front (Fig. 7). After transition zone of ~ 20 ns, the oscillating plateau follows. As distinct from the gabbro-diabase, the oscillations didn’t lead to irreversible fragmentation of material.

Fig. 6. Metallographic patterns of spall zone for the first (a) and second (b) kinds of gray iron.

The resistivity to spallation is conserved both at the impact velocity of 98.4 m/s and 224.8 m/s. However, with the increase of impact velocity the spall strength decreases: W =34. 7 m/s at the impact velocity of 98.4 m/s and W =23.1 m/s at the impact velocity of 224.8 m/s (Fig.8). Velocity variance presents over the front of compressive