PSI - Issue 2_B

Oleg B. Naimark / Procedia Structural Integrity 2 (2016) 342–349 Author name / Structural Integrity Procedia 00 (2016) 000–000

346

5

(REMIX REM 10-8 camera, time lag between pictures established in the different ranges of crack velocity: steady-state

s  10 ). Three characteristic regimes of crack dynamics were

С V V  , branching

C V V  and fragmenting

B V V  , when the multiply branches of main crack have the autonomous behavior (Fig.3, 4).

lg   sec c

V 0

3 4 2 5 6

1

2

-6 -5 -4

0.1

0.2

0.3

  GPa

a

Fig. 2: Fracture time c t for shocked rod of PMMA (1) and ultraporcelain (2) versus stress amplitude a  . Insert: surface pattern with mirror zones in different spall cross sections [6]. The scaling properties of failure were studied also under the recording of the stress dynamics using the polarization scheme coupled with the laser system, Fig.6,7. The stress temporal history was measured in the marked point deviated from the main crack path on the fixed (4 mm) distance. This allowed us to investigate the correlation property of the system using the stress phase portrait   ~  for slow and fast cracks.

, / V m s

B V

4 0 0

C V S V

0

6 0

2 0

4 0

, M P a 

Fig. 4: Crack velocity V versus stress  .

С V V  , branching

Fig. 3: Stress pattern for steady-state

C V V  and fragmenting

B V V  scenario of crack dynamics.

1 mm

1 mm

C B V V V   ) crack.

C V V  ) and fast (

Fig. 5: Failure surface for slow (left,