Explosion Mechanics

Investigation of a Nickel-Aluminum Reactive Shaped Charge Liner

[+] Author and Article Information
I. Lewtas

QinetiQ plc,
Fort Halstead, Sevenoaks,
Kent TN14 7BP, UK

N. Harrison

QinetiQ plc,
Cody Technology Park, Farnborough,
Hampshire GU14 0LX, UK

P. Gould

QinetiQ plc,
Bristol Business Park,
Coldharbour Lane,
Bristol BS16 1FJ, UK

D. Williamson

Cavendish Laboratory,
Cambridge University,
JJ Thompson Avenue,
Cambridge CB3 0HE, UK

Manuscript received June 28, 2012; final manuscript received December 26, 2012; accepted manuscript posted January 9, 2013; published online April 19, 2013. Assoc. Editor: Bo S. G. Janzon.

J. Appl. Mech 80(3), 031701 (Apr 19, 2013) (13 pages) Paper No: JAM-12-1270; doi: 10.1115/1.4023339 History: Received June 28, 2012; Revised December 26, 2012; Accepted January 09, 2013

A nickel/aluminum (NiAl) reactive powder system has been investigated to determine its mechanical properties under quasi-static and high rate compression to understand its deformation behavior. A shock recovery system has been used to define shock reaction thresholds under a triaxial loading system. Two nickel/aluminum (NiAl) shaped charge liners have been fired into loose kiln dried sand to determine whether the jet material reacts during the formation process. A simple press tool was developed to press the liners from a powder mixture of nickel and aluminum powder and a simple conical design was used for the liner. The shaped charge jet particles were recovered successfully in the sand and subjected to a detailed microstructural analysis. This included X-ray diffraction (XRD) and optical and electron microscopy on selected particles. The analysis demonstrated that intermetallic NiAl was detected and all the aluminum was consumed in the particles examined. In addition, different phases of NiAl were detected as well as silicon oxide in the target material. There was also some evidence that the aluminum had melted along with evidence of a dendritic microstructure. This is the clearest evidence that the shaped charge jet material has reacted during the formation process. Simulations have been performed using the GRIM Eulerian hydrocode to compare with flash X-rays of the jet.

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Fig. 1

Schematic illustrating various processes and their associated effects occurring during shock compression of powders (courtesy of N. Thadhani)

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Fig. 2

Particle size distribution for Al powder (left) and Ni powder (right)

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Fig. 3

SEM images of Al powder (left) and Ni powder (right)

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Fig. 4

SEM picture for 75% TMD NiAl (left) and 90% TMD NiAl (right)

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Fig. 5

Experimental arrangement for the determination of the shock Hugoniot

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Fig. 6

Front (dark) and rear (light) gauge traces for high (left) and low (right) velocity impact for NiAl

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Fig. 7

Measured Hugoniot curves for NiAl at 75% TMD

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Fig. 8

Initial EOS for nickel aluminum pressed powder for a range of TMDs

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Fig. 9

Comparison of compaction between that predicted by foam theory and that measured on powders

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Fig. 10

Variation in bulk and shear modulus with density. Equation is trend line on bulk modulus.

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Fig. 11

Comparison of Porter–Gould EOS with Cambridge experimental data

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Fig. 12

Schematic of shock recovery system

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Fig. 13

Photographs of the shock recovery system showing the general deformation and the recovery of sample material for the 955 m/s impact case

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Fig. 14

Micrograph of the polished cross section showing the approximate extent of regions where XRD was taken

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Fig. 15

XRD scan from recovered sample on axis

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Fig. 16

Phase diagram for nickel aluminum powder systems

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Fig. 17

SEM micrograph indicating potential areas of melt (i.e., smooth regions)

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Fig. 18

SEM micrograph from the central part of the reacted powder showing uniformity of NiAl microstructure

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Fig. 19

Boundary between reacted and unreacted material for 606 ms−1 impact case

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Fig. 20

Percentage of material reacted v impact velocity for 60% TMD NiAl in the shock recovery system

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Fig. 21

Simulation “design curves” of maximum pressure v impact velocity for shock recovery rig

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Fig. 22

Photographs of recovered largely unreacted samples (top and middle) compared to a partially reacted sample (bottom)

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Fig. 23

Schematic of NiAl shaped charge design

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Fig. 24

Schematic of press tool

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Fig. 25

Examples of NiAl shaped charge cone and full charge

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Fig. 26

Morphology of pressed powder in liner at apex and base

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Fig. 27

Flash X-rays at 26 (top left), 36 (top right), and 46 μs (bottom) after detonation

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Fig. 28

Comparison of simulation with experiment for unreacted model (top) and reacted model (bottom)

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Fig. 29

Typical appearance of collected debris

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Fig. 30

Optical microscopy showing dendritic microstructure consistent with AlNi (dark) and Ni5Al3 (light)

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Fig. 31

Backscattered electron micrographs showing a segregated microstructure




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