PSI - Issue 28

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

603

2

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

diameter of 6 mm and length of 18 . 5 mm . A slot of 1 mm diameter was established in the plastic coaxially afterwards. The copper wire of 120 µ m diameter was placed inside the slot and connected to the capacitor charged up to 20 − 22 kV . After the circuit was closed with high-rated discharger, the wire was exploded by the electric current. Generated by the explosion pressure was transmitted by the shock wave from the air slot inside the PMMA media and subsequently to the aluminium cylinder.

2

4

3

1

5

C

Fig. 1. The schematics of our experiment: 1) charging device for capacitor C ; 2) high-rated discharger; 3) aluminium shell; 4) PMMA cylinder; 5) slot with the wire to be exploded.

The aluminium shell of 0 . 5 mm thickness (internal diameter 6 mm and external diameter 7 mm ) was ruptured during these tests. Pressures in the media of cylinder were monitored with developed by us piezo-probe.

3. Equation of state for the electric explosion of wire

Here we will try to construct the equation of state for the electric explosion of wire (EEW) in the form of P ρ 0 ρ = Ae − α ρ 0 ρ , (1) based on experimental results provided by Bulgkov et al. (2009). In this equation A and α are parameters based on experimental studies of EEW; P is a pressure of the explosion products and ρ 0 /ρ is explosion products expansion coe ffi cient (dimensionless volume). ρ 0 is the initial density of exploded wire and ρ is the density of EEW products. In our tests, we used the following parameters of the setup. The copper wire of 120 µ m diameter and 25 mm length taken as exploding object. The capacitor of 0 . 5 µ F charged up to 20 kV used to provide energy for the wire explosion. So, initial energy income to the system was 100 J . By assuming that in the instant of explosion radius of explosion channel (and accordingly its volume) has zero value and density of explosion products was ρ = 150 kg / m 3 ( Bulgkov et al. (2009)) in that moment, we can estimate expansion coe ffi cient and the density of transmitted energy as

8 . 93 · 10 3 0 . 15 · 10 3

ρ 0 ρ

= 59 . 5;

=

(2)

ε = 13 · 10 6 J / kg .

Pressure in the explosion air channel may be determined by Gru¨neisen equation: P = γρε

(3)

With the Gru¨neisen parameter in the air γ = 0 . 75. Subsequently, the values of ρ and ε estimated by data provided by Bulgkov et al. (2009). Equation (3) was used to determinate air pressure for values of radius of the channel equal to 0 . 2 mm , 0 . 4 mm and 0 . 5 mm . Experimental coe ffi cients A and α estimated as A = 6 . 38 GPa and α = 0 . 024. So, pressure in the explosion channel was calculated. Results of this calculus and experiments provided in table 1.