PSI - Issue 2_B

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

480

4

mesoscale-1, so it may be concluded that irreversible displacement of structural element of mesoscale-2 begins just at the moment when relaxation of local stresses at the mesoscale-1 is exhausted. Analogous steps present at the rest of the velocity profiles, registered at the impact velocities of 92 m/s, 117.5 m/s and 224.8 m/s (Fig.4). The velocity UInst defines the structural instability threshold at the mesoscale-2. In the process of displacement of structural element, a local stress relaxation occurs after what the material restores its resistivity to dynamic fracture (piece FK in Fig. 3). After transition of shock front into plateau of compressive pulse, the oscillations of particle velocity are initiated.

140

4

120

3

100

2

80

60

Uins t

40

1

20

free surface velocity, m/s

0

0

500

1000

1500

2000

2500

3000

time.ns

Fig. 4. Free surface profiles for gabbro-diabase at the impact velocities of 37.2 m/s, 92m/s, 117.5 m/s and 126 m/s.

2.2. Gray iron In the present work two kinds of gray iron with different alloying of copper and titanium were tested. The chemical composition for both kinds of gray iron is provided in Table 2.

Table 2 . Chemical composition of gray iron. Kind of gray iron

Element content, mass %

Element Kind 1 Kind 2

C

S

N

Si

P

Se

Mn

Fe

Cu

Ti

4 4

0.07 0.07

0.0049 0.0052

1.92 1.79

0.08 0.15

0.1

0.26 0.20

92.84 93.49

0.33 0.08

0.39 0.14

0.07

Results of shock tests for gray iron are provided in Table 3 and Fig. 5. Table 3. Results of shock tests for gray iron Kind of gray iron U imp , m/s U inst , m/s W, m/s

А osc ,m/s

 t, ns

Kind 1 Kind 2

221.3 224.8

161

27

-

-

82

14.5

12

214

The second column in Table 3 provides the impact velocity, the third column gives the structural instability threshold, the fourth column provides the value of spall strength of the material, the fifth column provides the magnitude of oscillations at the plateau of pulse and sixth column means the time development of local damage at the mesoscale-2. Although the impact velocities for both materials are approximately identical, the instability threshold and spall strength for the second kind of gray iron turn out to be twice smaller.