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Research Papers

Impact Experiments Into Borosilicate Glass at Three Scale Sizes

[+] Author and Article Information
Charles E. Anderson, Carl E. Weiss, Sidney Chocron

Engineering Dynamics Department,  Southwest Research Institute, P. O. Drawer 28510, San Antonio, TX 78228-0510

We make no distinction in this article between V50 and VBL ; but will use VBL to designate V50 as determined from Lambert's equation.

The loading of the Lexan® substrate over a large diameter relative to the thickness results in the plate acting similar to a bulging membrane, creating large hoop stresses. These hoop stresses exceed the tensile strength of the Lexan® , resulting in radial fractures. Formation of the radial cracks, combined with the exiting plug, removes the loading stresses on the membrane, and elastic forces cause the deformed Lexan® plate to return to its nominally unloaded shape. Lexan® , because of its limited ductility, cannot petal like a ductile metal target, but the loading and response are similar.

J. Appl. Mech 78(5), 051011 (Aug 05, 2011) (10 pages) doi:10.1115/1.4004281 History: Received November 23, 2010; Revised May 23, 2011; Published August 05, 2011; Online August 05, 2011

Glass impact experiments were designed at three different scales—0.22-cal, 0.375-cal, and 0.50-cal—named after the diameter of the bullets. Four experimental series were conducted at the three scale sizes: (1) Lexan® -only experiments; (2) monoblock glass experiments; (3) single impact bonded glass experiments, and (4) multi-hit experiments. The experiments were conducted to obtain residual velocity Vr as a function of impact (striking) velocity Vs , including sufficient partial penetrations to calculate a ballistic limit velocity V50 . The Vs – Vr data were fit to the Lambert equation to obtain another estimate of V50 . The objective of the experiments was to investigate whether a time dependency exists in glass damage/failure for ballistic experiments, and if so, quantify this dependence. No scale effect was observed in experimental results for the Lexan® -only experiments. But a variety of scale effects were observed in the glass impact experiments, suggesting that failure is time dependent within the timeframe of ballistic events.

Copyright © 2011 by American Society of Mechanical Engineers
Topics: Glass , Bullets , Failure
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References

Figures

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Figure 1

Final target designs, based on off-the-shelf thicknesses of Lexan® (thicknesses and bullets are to scale, but not lateral plate dimensions). (a) 0.50-cal target design, (b) 0.375-cal target design, and (c) 0.22-cal target design.

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Figure 2

Damaged bullets with different heat treatments

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Figure 3

Adiabatic stress-strain curves for Rc30 and Rc53 4340 steel

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Figure 4

Residual velocity versus impact velocity for Lexan® targets

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Figure 5

Front and rear faces of a monoblock glass target experiment: 0.50-cal bullet (21-mm-thick Borofloat glass), Vs  = 257 m/s. (a) Front (strike) face, and (b) Rear (exit) face with spall cone (arrow points to spall cone).

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Figure 6

Residual versus impact velocity for monoblock glass targets

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Figure 7

Comparison of extent of damage for bonded glass versus monoblock glass. The arrow points to the exit hole in the Lexan® substrate. (a) Glass/Lexan® : Vs  = 645 m/s and (b) Monoblock glass: Vs  = 662 m/s.

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Figure 8

Residual versus impact velocity for monoblock glass and bonded glass targets: 0.50-caliber bullet

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Figure 9

Lexan® failure on rear side of 0.22-cal bonded glass targets

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Figure 10

Petalling-like failure of Lexan® substrate for 0.22-cal bonded glass targets; the arrows denote the petallike cracks emanating from failure plug

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Figure 11

Multi-hit impact experimental results for 0.50-cal target

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Figure 12

Impact into multi-hit glass versus single-hit bonded glass: 0.22-cal target

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Figure 13

Impact into multi-hit glass versus single-hit bonded glass: 0.375-cal target

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Figure 14

Impact into multi-hit glass versus single-hit bonded glass: 0.50-cal target

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Figure 15

Ballistic limit velocity V50 versus bullet caliber

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Figure 16

Vs – Vr response for bonded glass targets (Lambert’s equation). (a) Single-hit targets and (b) Multi-hit targets.

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