Study on the Mechanism of Secondary Penetration of Long-rod Projectile and Its Influencing Factors

doi:10.12382/bgxb.2023.0035

Abstract

Abstract:

A 3D SPH-FEM finite element model is established to further investigate the penetration mechanism of long-rod projectile at the third penetration stage. On the basis of verifying the effectiveness of the model, a penetration of gold rod against a semi-infinite thick 7075-T6 aluminum target is studied, the mechanism of the third penetration stage is explored, and the influence law of projectile/target density and strength, and L/D of projectile on penetration is also analyzed. The calculated results show that the reason why the P/L vs. striking velocity curve for gold rod penetrating 7075-T6 aluminum target is broken is the secondary penetration of the inverted rod debris. A tubular fragment is formed after the gold rod is eroded. At high initial velocity, its velocity is higher, its direction is consistent with the penetration direction, and its density is large. Therefore, it will continue to penetrate the target after the projectile body is completely eroded. The secondary penetration depth of the gold rod increases in an “S” shape with the increase in striking velocity, and its contribution to the total penetration depth is even as high as 15.6% at striking velocity of 3km/s. When there is a secondary penetration, it is more appropriate to divide the third penetration stage into residual and secondary penetration stages. High projectile-target density ratio is beneficial for the formation of secondary penetration. The influence of the target density and strength on the penetration capability significantly exceeds that of the projectile. Under the conditions of the unchanged length or mass of the projectile, the effect of length-to-diameter ratio on the hydrodynamics and total penetration depth is significant, but its effect on the secondary penetration is small.

Key words: gold long-rod, secondary penetration, 7075-T6 aluminum target, numerical simulation

CLC Number:

O347

TANG Kui, WANG Jinxiang, LIU Liangtao, YANG Ming. Study on the Mechanism of Secondary Penetration of Long-rod Projectile and Its Influencing Factors[J]. Acta Armamentarii, 2023, 44(12): 3707-3718.

Figures/Tables 18

Fig.1 Numerical simulation model for gold rod penetrating 7075-T6 aluminum target

Table 1 Material parameters of projectile and target

材料	G₀ / GPa	ρ/ (g·cm^-3)	σ₀/ MPa	T_m0/ K	c₁/ (m·s^-1)	S₁	G'_p	G'_T/ (GPa·K^-1)	σ'_p	β	n	γ₀	σ_m/ MPa
金杆	28	19.3	200	1280	3080	1.56	1.05	-0.00871	7.50×10^-4	49	0.39	2.99	225
铅杆	4.9	11.9	18	600	2092	1.45						2
铝杆	26.9	2.7	290	930	5380	1.34						2.1
7075-T6铝靶	26.7	2.8	496	1220	5200	1.36	1.741	-0.01645	2.74×10^-2	965	0.1	2.2	810

Fig.2 Comparison between the simulated result and the experimental result in Ref.[10]

Fig.3 Comparison between experimental (left) and simulated (right) results for jacketed long-rods impacting semi-infinite target[2]

Fig.4 Simulated results of normal and reverse trajectories

Fig.5 Simulated results for gold rods impacting 7075-T6 aluminum targets at different striking velocities

Fig.6 Penetration process of gold rod impacting 7075-T6 aluminum target at 3km/s

Fig.7 The process of gold rod erosion and formation of debris tube and velocity field

Fig.8 Evolution process and velocity field of gold rod debris during secondary penetration

Fig.9 Typical simulated results for time histories of back-end velocity, penetration velocity, projectile length, penetration depth, and interface pressure at rod-target boundary for L/D=7.35 gold rod impacting aluminum target at 3.0km/s

Fig.10 The rod/target interface pressure and the division of penetration stage when secondary penetration exists

Fig.11 Penetration depth composition and experimental results for gold rod impacting 7075-T6 aluminum target

Table 2 Results of gold rod impacting 7075-T6 aluminum target with different thickness

Table 3 Penetration depth for gold rod impacting 7075-T6 aluminum target with different thickness at different v0 mm

h/cm	v₀/(km·s^-1)
h/cm	2.540	2.771
1.4	12.703	14.020
1.5	12.617	13.357
1.6	12.656	13.301
无限厚	12.842	13.507

Fig.12 Relationship the rod/target density and penetration depth at different striking velocities

Fig.13 Relationship between penetration depth and rod/target strength

Fig.14 Relationship between penetration depth and L/D

Fig.15 Relationship between the residual velocity of eroded projectile debris and L/D

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