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RESEARCH PAPERS: Terminal Ballistics

Experimental and Numerical Investigations on the Origins of the Bodywork Effect (K-Effect)

[+] Author and Article Information
F. Coghe2

Department of Weapon Systems and Ballistics, Royal Military Academy, Renaissance Avenue 30, Brussels 1000, Belgiumfrederik.coghe@rma.ac.be

N. Nsiampa, G. Dyckmans

Department of Weapon Systems and Ballistics, Royal Military Academy, Renaissance Avenue 30, Brussels 1000, Belgium

L. Rabet

Department of Civil Engineering and Materials, Royal Military Academy, Renaissance Avenue 30, Brussels 1000, Belgium

2

Corresponding author.

J. Appl. Mech 77(5), 051801 (Jun 09, 2010) (9 pages) doi:10.1115/1.4001692 History: Received July 17, 2009; Revised April 12, 2010; Posted May 04, 2010; Published June 09, 2010; Online June 09, 2010

Abstract

The integration of a high-hardness steel armor plate inside the bodywork of a vehicle may result in a decrease in the overall ballistic resistance. This phenomenon is referred to as the bodywork effect. The effect was examined for a $5.56×45 mm$ North Atlantic Treaty Organization (NATO) Ball projectile. Previously reported experimental work has confirmed the numerically based assumption that the bodywork effect was due to the flattening of the tip of the projectile upon perforation of the frontal bodywork plate prior to hitting the integrated armor. The amount of qualitative and quantitative experimental data has now been extended. In order to eliminate the data dispersion observed after perforating the bodywork, an adapted projectile geometry with a truncated nose was fired directly against the armor plate. Ballistic testing also involved firing a soft-core $5.56×45 mm$ projectile for which a similar mechanism was observed. A finite element code was used to simulate the impact process for the different types of projectiles. The parameters of the selected strength and failure models were experimentally determined for the high-hardness armor plate. As to the ballistic limit velocity and plugging morphology there is a good correspondence between the experimental and computed results. Nevertheless, an improved failure model is necessary to get satisfactory computed residual projectile velocities.

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Figures

Figure 1

Different projectile geometries used for ballistic testing with (a) standard SS109 projectile, (b) standard M193 projectile, and (c) adapted flat-tipped SS109 projectile

Figure 2

Different original and recovered projectiles with (a) the original SS109 projectile, (b) an SS109 projectile after perforation of the 1mm bodywork sheet, showing a flattened projectile tip, (c) an SS109 projectile after perforation of the 1 mm bodywork sheet, showing blunting of the projectile tip with detached ring of the bodywork sheet attached to the projectile tip, and (d) the adapted flat-tipped SS109 projectile

Figure 3

Comparison of the residual velocities for the simulated and experimental results for the different projectile geometries: (a) regular SS109 projectile, (b) flat-tipped SS109 projectile, and (c) regular M193 projectile. Curves were fitted to the data using the analytical Lambert model (25).

Figure 4

Stress-strain curves obtained with the SHPB for different temperatures and nominal strain rates of (a) 1000/s and (b)1500/s, and the fitted constitutive strength model (JC: Johnson–Cook)

Figure 5

(a) Comparison of the fracture strain given by the failure model (JC: Johnson–Cook) and the average experimental data points; (b) statistical evaluation (99% confidence interval) of the failure model for different temperatures by use of the experimental fracture data

Figure 6

Initial impact and flattening of the M193 leading to deformation localization

Figure 7

Penetration channel as a function of impact speed for the M193 projectile; experimental results for respective impact velocities of (a) 911 m/s, (b) 911 m/s, and (c)1062 m/s; numerical results for respective impact velocities of (d) 880 m/s, (e) 900 m/s, and (f) 1100 m/s. The figures represent impacts just below, just above, and well above the ballistic limit velocity, both for the experimental as for the simulated case. Due to ballistic dispersion, the same impact velocity can lead to both a partial and a complete perforation, as in the experimental cases (a) and (b).

Figure 8

Plugging mechanisms: (a) single plug for low impact velocities, (b) double plug for higher impact velocities, and (c) front face of armor plate for higher impact velocity showing dual diameter

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