Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Shock Desensitization Effect in the STANAG 4363 Confined Component

Water Gap Test A.S.Lefrancois*, R.S.Lee and C.M.Tarver

*Participating guest from DGA/CEG (Gramat)

This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Overview (ECWGT)Introduction– Configurations– Models– Shock wave in water (time arrival, peak pressure)– Go/No Go results– Confinement influence on the Go results (Lagrangian

pressure)Conclusion

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Explosive Component Water Gap Test (ECWGT)• Experiments

– Defined by Stanag 4363 ed.3 final draft– performed by Wiweb and TNO– ∅ 3 mm PETN pellet with steel conf. 1mm, 2mm, 3.5 mm

thick

• Goal :– Trying to understand better the influence of the conf. related

to the desensitization with 3.5 mm thick confinement– Update the Stanag 4363 ed.3 for confined components with

explosive fills having a diameter less than 5 mm

• This work, Ls-Dyna runs 2D axi and 3D wedge :– Models, including Ignition and Growth– aluminum or steel annular confinement– target double height – half donor charge height and initiation type– PMMA confinement thicknesses (water column)– constitutive laws on go/no go threshold– glue between Pellet and witness rod

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Special Effect for Small Explosives < ∅ 5 mm3 mm PETN Pellets with Annular Steel Confinement

15

20

25

30

35

40

0 0,5 1 1,5 2 2,5 3 3,5 4

Confinement Wall Thickness, mm

Med

ian

Wat

er G

ap, m

m

WIWEB Sep. 2003 WIWEB Mai 2004WIWEB 2004 corrected TNO March 2002TNO Okt. 2002 Polynomisch (Trendline )

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Configurations - Models (ECWGT)

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Water shock wave (ECWGT)Time arrival versus distance in water :- Comparison experiments – calculations- Effect of the PMMA confinement

0

2

4

6

8

10

12

14

16

0 5 10 15 20 25 30 35 40 45

Gap [m m ]

Tim

e [m

icro

sec]

2D_lagrangian conf. pmma 4 mm

F.Trimborn_experiments

3D wedge ALE conf. pmma 4 mm

2D_lagrangian_no_water_conf

2d_lagrangian_conf. pmma 2mm

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Water shock wave (ECWGT)

Peak pressure versus distance in water :- Comparison experiments – calculations- Effect of PMMA confinement

0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40Distance (mm)

Peak

pre

ssur

e (k

bars

)

Experiments conf. PMMA 2mm

3D wedge ALE conf. PMMA 4 mm

2d axi conf. PMMA 2 mm

2D axi conf. PMMA 2 mm flat initiation

Median water Gap

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Go/NoGo results

Steel confinement (target)

Initiation / Donor charge Go, water gap No Go, water gap

Point / ∅ 21 mm h 20.3 mm - 16.7 mm

Point / ∅ 21 mm h 20.3 mm - 20.7 mm

Flat / ∅ 21 mm h 18 mm 15 mm 17 mm

Point / ∅ 21 mm h 18 mm(simulation reference)

15 mm 17 mm

Donor charge Go, water gap No Go, water gap

Half height donor 26 mm 28 mm

Standard height donor 27 mm 29 mm

0

10

20

30

40

50

60

0 10 20 30 40Distance (mm)

Peak

pre

ssur

e (k

bars

)

Experiments 2d axi point initiation2D axi flat initiationhalf donor point initiationInfluence of the donor pellet :

- cavity pellet- plain pellet - half donor

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Go/No Go resultsAluminum confinement

0

5

10

15

20

25

30

35

0 1 2 3 4 5Thickness of the confinement (mm)

Wat

er g

ap (m

m)

AluminumExperimentsNumerical simulations goNumerical simulations no go

∅ 3 h 3 mm PETN pellet

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Go/No Go results

Receptor charge, ∅ 3 mm Go, water gap No Go, water gap

6 mm height - 33 mm

3 mm height (reference) 27 mm 29 mm

- Steel confinement - ∅ 3 h 6 mm PETN Pellet

0

5

10

15

20

25

30

35

40

0 1 2 3 4 5 6Steel confinement thickness (mm)

Wat

er g

ap (m

m)

Experiments 6 mm height WIWEBNumerical simulation No go

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Go/No Go results

0

5

10

15

20

25

30

35

40

0 1 2 3 4Steel Confinement (mm)

Med

ian

wat

er g

ap (

mm

)

Go Calculations 2 mm thick PMMANo Go Calculations 2 mm thick PMMAExperiments 2 mm thick PMMAExperiments

Steel confinement∅ 3 h 3 mm PETN pellet

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Confinement Influence on Go Results (ECWGT)

1 mm Steelconfinement

∅ 3 h 3 mm PETN pellet

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Confinement Influence on Go Results (ECWGT)

2 mm Steelconfinement

∅ 3 h 3 mm PETN pellet

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Conclusion

– Ignition and Growth of the PETN Pellet– Influence of the donor charge, and point or planar initiation – Influence of the aluminum, steel confinement thicknesses– Influence of the height of the pellet– Influence of PMMA confinement (water column)– Influence of constitutive laws on go/no go threshold– Influence of glue between Pellet and witness rod

Experimental results are related for 2 mm and 3.5 mm confinement with desensitization due to the second lateral re-shock from the steel confinement

The numerical simulation allow us to study the following effects :

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Confinement Influence on Go Results (ECWGT)

Gap 31 mm steel 2 mm pressure – Burn fraction

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Confinement Influence on Go Results (ECWGT)

Gap 33 mm steel 2 mm pressure – Burn fraction

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Confinement Influence on Go Results (ECWGT)

Gap 33 mm steel 3.5 mm pressure – Burn fraction

Lawrence Livermore National Laboratory, Detonator / Detonation Physics Group, UCRL-PRES-216779

Confinement Influence on Go Results (ECWGT)

Flat initiation