PSI - Issue 28

Victor Kats et al. / Procedia Structural Integrity 28 (2020) 602–607

606

V. Kats, V. Morozov / Structural Integrity Procedia 00 (2020) 000–000

5

With specially designed piezo-probe, we registered pressures in PMMA media on a various radius. Dependence between this pressure and radius provided in figure 5.

10 8

11

10

9

8

7

6

5

P, Pa

4

3

2

1

0

0

0.01

0.02

0.03

0.04

0.05

0.06

R, m

Fig. 5. Dependence between pressure on the external surface of PMMA cylinder and radius of the cylinder.

Obtained dependence allows us determinate pressure on the external surface of the PMMA cylinder (radius r = 3 mm ): P 3 = 970 MPa . So, the pressure transmitted into aluminium shell by the shock wave propagated through the PMMA media may be determined with equation analogous to (4):

2 ρ 4 c 4 ρ 4 c 4 + ρ 3 c 3

P 3 .

(5)

P 4 =

3 and c 4 = 6300 m / s are density and sound speed of the aluminium shell. And ρ 3 = ρ 2 = 3 = c 2 = 2670 m / s are the same parameters for PMMA. So, after this calculations pressure transmitted

Here ρ 4 = 2700 kg / m

1180 kg / m 3 , c

into the shell is P 4 = 1630 MPa . Which is actually the radial stress acting on the shell: P 4 = σ r = 1630 MPa .

(6)

This stress appears to be enough for the shell failure, as shown in our experiments. The study Bagheri et al. (2017) estimates circular stress being very close to the radial pressure: σ r ≈ 1 . 1 σ t . So, circular stress for our experiments determined as σ t = 1480 MPa . It may be regarded as failure strength of a studied y aluminium shell. This result has good correspondence with Kanel et al. (2008). According to obtained by us experimental dependence P ( r ) and experimental results provided by Morozov et al. (2020) fracture strength of PMMA in our experiments may also be estimated as 240 − 480 MPa and lays in good correspondence to Parhomenko, Utkin (1990) and Demidov et al. (2017).

5. Conclusion

In the presented study, we developed and pilot-tested technique to experimentally estimate failure strengths for a composite thick-walled 2-component cylinder. The pressures measured with developed by us specially designed piezo-probe and estimated with fundamental classic models. Circular stress in the aluminium shell estimated as the final result and boundary value of this stress to rapture the shell was determined. All obtained outputs compared to published results.