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Research Papers: Design and Analysis

# Low Velocity Perforation of Mild Steel Circular Plates With Projectiles Having Different Shaped Impact Faces

[+] Author and Article Information
Norman Jones1

Impact Research Centre, Department of Engineering, The University of Liverpool, Liverpool L69 3GH, UKnorman.jones@liv.ac.uk

R. S. Birch

Impact Research Centre, Department of Engineering, The University of Liverpool, Liverpool L69 3GH, UK

The value of $k$ for a transverse shear failure is usually much smaller than $k=1$ and lies within the range of approximately $14$ to $12$(18-19).

A more rigorous analysis of material strain rate sensitive effects using equivalent stresses and strains is reported in a companion article.

$ξ=0$, 0.6, and 0.9 for the conical projectiles.

Note that equations (15) in Ref. 8 are not correct for $2R∕d>12$ since the last term should be replaced by 4.553 and not unity as stated.

1

Corresponding author.

J. Pressure Vessel Technol 130(3), 031205 (Jun 20, 2008) (11 pages) doi:10.1115/1.2937768 History: Received October 30, 2006; Revised April 13, 2007; Published June 20, 2008

## Abstract

This article studies the perforation of mild steel circular plates struck normally by cylindrical projectiles having blunt, hemispherical, and conical impact faces. Experimental results are obtained using a drop hammer rig for the perforation of $2–8mm$ thick plates struck by projectiles weighing between $1.75kg$ and $176kg$ and traveling up to about $12m∕s$. The impact positions are at several radial locations across a plate, and it turns out that the perforation energy decreases as the impact location is moved away from a plate center toward the support. It transpires that the projectiles with hemispherical and blunt impact faces require the largest and the smallest impact perforation energies, respectively. Comparisons are made between the experimental results for the perforation energies and the predictions of several empirical equations. Design calculations for the impact perforation of plates could be undertaken using projectiles with blunt impact faces, which would provide a lower bound on the perforation energy of projectiles having hemispherical or conical impact faces, at least within the range of the parameters studied.

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## Figures

Figure 9

Comparison of dimensionless perforation energies at several positions, ξ, with an empirical equation (Eq. 6) for blunt projectiles having d∕H=2.54(2R=203.2mm). Experimental results: ——◻——, ξ=0; ——▽—— (▼ severe cracking), ξ=0.5; ——△——, ξ=0.8. — ⋅ —: empirical equation (Eq. 6) (Eq. 8 at ξ=0).

Figure 3

Variation of dimensionless perforation energies with ξ, d∕H, and striker nose geometry for 4mm thick mild steel plates with 2R=203.2mm. The notation is defined in Fig. 2. ▽: experimental results, blunt projectile with d∕H=1.27(10).

Figure 4

Variation of dimensionless energies for perforation and cracking with ξ and striker nose geometry for 6mm thick mild steel plates with d∕H=2.54 and 2R=203.2mm. ○ and ◻, defined in Fig. 2; ◼, +, and ●, energies for cracking caused by blunt, conical, and hemispherical shaped projectiles, respectively.

Figure 5

Variation of dimensionless perforation energies with ξ, d∕H, and projectile nose geometry for 8mm thick mild steel plates with 2R=203.2mm. The notation is defined in Fig. 2.

Figure 6

Photographs of some typical circular plate failures. (a) H=8mm, ξ=0, blunt-faced projectile, d∕H=1.27. (b) H=6mm, ξ=0.8, blunt-faced projectile, d∕H=2.54. (c) H=4mm, ξ=0, hemispherical projectile, d∕H=1.27. (d) H=2mm, ξ=0, conical projectile, d∕H=5.08. (e) H=6mm, ξ=0.8, hemispherical projectile, d∕H=2.54. (f) H=8mm, ξ=0, conical projectile, d∕H=2.54.

Figure 7

Variation of dimensionless perforation energies with plate thickness for d∕H=2.54 and 2R=203.2mm. The notation is defined in Fig. 4. (a) ξ=0, (b) ξ=0.5 (ξ=0.6 for × at H=8mm), and (c) ξ=0.8 (ξ=0.9 for × at H=8mm)

Figure 8

Comparison of dimensionless perforation energies with empirical equations for fully clamped circular plates (2R=203.2mm) struck at the center (ξ=0) by blunt-faced projectiles having d∕H=2.54. Experimental results: ——◻——. Empirical results: – – – – – – 1, SRI equation (Eq. 1); – – – – – –- 2, BRL equation (Eq. 2); – – – – – – 3, Neilson equation (Eq. 3) (lower curve has a coefficient 1.0 instead of 1.4); – – – – – – 4, Jowett equation (Eq. 7); —⋅—⋅— 5, Eq. 8.

Figure 1

(a) Idealized experimental arrangement with a blunt-faced projectile striking a circular plate normally at a radial distance ri from the plate center. (b) Projectile with a conical nose having a 90deg included angle. (c) Projectile with a hemispherical nose of radius d∕2.

Figure 2

Variation of dimensionless perforation energies with ξ, d∕H, and striker nose geometry for 2mm thick mild steel plates with 2R=203.2mm. ——◻——, blunt; —⋅—⋅X—⋅—, conical; – – ○ – –, hemispherical. ▽: experimental results, blunt projectile with d∕H=2.54(10).

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