Formation Mechanism and Principle of Coated Reactive Explosively Formed Projectile

doi:10.12382/bgxb.2023.1219

Abstract

Abstract:

The formation mechanism of coated reactive explosively formed projectiles (EFP) and the influence laws of liner structure on the formation behavior of EFP are studied. A Lagrange-Euler numerical simulation model of coated EFP is established, which reveals that the formation process of coated reactive EFP mainly includes axial double-liner impacting phase, radial coat closing phase and metal precursor penetrator stretching phase. In the axial double-liner impacting phase, the velocities of two liners rise in turns with axial kinetic energy transfer. In the radial coat closing phase, the copper liner folds forward to the axis and its tail completely coats the reactive liner. It is mentioned that a metal precursor penetrator is formed on the edge of copper liner. After that, the metal precursor penetrator is stretched and even fractured over time. Further, the influences of the shape parameters of copper and reactive liners on the coating formation are studied. With the decrease in the copper liner edge thickness from 2.0mm to 0.5mm, the closing time decreases from 57.9μs to 23.9μs, meanwhile the tip velocity increases from 1 851m/s to 2370m/s, and the penetrator length increase from 76mm to 110.5mm. As the curvature radius of copper liner decreases from 60mm to 40mm, the closing time of coating decreases from 42.1μs to 28.1μs, meanwhile the tip velocity increases from 1789m/s to 2242m/s, and the penetrator length increases from 66mm to 100mm. With the decrease in the reactive liner thickness from 6mm to 2mm, the closing time decreases from 52.0μs to 32.1μs, meanwhile the reactive liner mass decreases from 6.47g to 2.37g. With the decrease in the reactive liner diameter from 32mm to 16mm, the closing time decreases from 34.4μs to 30.8μs, meanwhile the reactive liner mass decreases from 6.42 g to 1.61g. The results can provide guidance and reference for the design of coated reactive EFP shaped charge.

Key words: shaped charge, liner, formation behavior, reactive liner, coated EFP

BIE Haiyuan, ZHANG Hongyu, MA Hongbing, QIU Wenhao, ZHENG Yuanfeng. Formation Mechanism and Principle of Coated Reactive Explosively Formed Projectile[J]. Acta Armamentarii, 2025, 46(1): 231219-.

Figures/Tables 22

Fig.1 Shaped charge with double-layer coated liners

Table 1 Parameters of 8701 explosive[18]

参数	数值	参数	数值
ρ_e/g·cm^-3	1.71	R₁	4.2
D_C-J/m· $s - 1$	8315	R₂	1.1
p_C-J/GPa	28.6	ω	0.34
A/GPa	524.23	E₀/GPa	8.499
B/GPa	7.678

Table 1 Parameters of 8701 explosive[18]

参数	数值	参数	数值
ρ_e/g·cm^-3	1.71	R₁	4.2
D_C-J/m· $s - 1$	8315	R₂	1.1
p_C-J/GPa	28.6	ω	0.34
A/GPa	524.23	E₀/GPa	8.499
B/GPa	7.678

Table 2 Parameters of aluminum, copper and 45# steel[18]

材料	ρ/ (g·cm^-3)	a/ GPa	b/ GPa	C	n	m	T_m
紫铜	8.96	0.09	0.292	0.025	0.31	1.09	1356
45号钢	7.85	0.792	0.51	0.014	0.26	1.03	1793
Al	2.79	0.205	0.230	0.121	0.21	1.03	1500

Table 3 Main parameters of reactive material[20]

参数	数值	参数	数值
ρ/(g·cm^-3)	2.27	C	0.4
c₀/(m· $s - 1$ )	1450	n	1.8
s	2.2584	m	1
a/MPa	8.044	γ	0.9
b/MPa	250.6

Table 3 Main parameters of reactive material[20]

参数	数值	参数	数值
ρ/(g·cm^-3)	2.27	C	0.4
c₀/(m· $s - 1$ )	1450	n	1.8
s	2.2584	m	1
a/MPa	8.044	γ	0.9
b/MPa	250.6

Fig.2 Calculation method for the formation of coated reactive EFP

Table 4 Main parameters of air[21]

ρ_a/ (g·cm^-3)	γ_a	C_p (kJ·kg^-1· $K - 1$ )	C_v (kJ·kg^-1· $K - 1$ )	T/K	E_a/ (kJ·kg^-1)
1.225	1.4	1.005	0.718	288.2	294

Table 4 Main parameters of air[21]

ρ_a/ (g·cm^-3)	γ_a	C_p (kJ·kg^-1· $K - 1$ )	C_v (kJ·kg^-1· $K - 1$ )	T/K	E_a/ (kJ·kg^-1)
1.225	1.4	1.005	0.718	288.2	294

Fig.3 Comparison of experimental[22](upper) and numerically simulated results (below)

Fig.4 Formation process of forward EFP

Fig.5 Velocity curve of copper liner with variable thickness

Fig.6 Axial and radial velocity curves of observation points

Fig.7 Double-liner impacting phase of coated EFP

Fig.8 Radial closing phase of coated EFP

Fig.9 Metal precursor penetrator stretching phase of coated EFP

Fig.10 Pressure-and temperature-time curves at the observation points

Fig.11 Radial velocity curves of coated EFP tip with different copper liner edge thicknesses

Fig.12 Coated EFP shapes with different copperliner thicknesses (4 times stand-off)

Fig.13 Radial velocity curves of coated EFP tips with different curvature radii of copper liner

Fig.14 Coated EFP shapes with different copper curvature radii (4 times stand-off)

Fig.15 Radial velocity curves of coated EFP tips with different reactive liner thicknesses

Fig.16 Coated EFP shapes with different reactive liner thicknesses (4 times stand-off)

Fig.17 Radial velocity curves of coated EFP tips with different reactive liner diameters

Fig.18 Coated EFP shapes with different reactive liner diameters (4 times stand-off)

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