Blast characterisation through impulse measurements
JD Reinecke
1, iM SnyMan
1, R ahMeD
1, FJ Beetge
21
CSIR Defence, Peace, Safety and Security, P O Box 395, Pretoria, 0001 Email: [email protected] – www.csir.co.za
2
Armscor, Acquisition, Landward Systems, Erasmusrand, Pretoria, South Africa Email: [email protected]
IntRODuCtIOn
the development of landmine protection solutions for vehicles requires that the threat posed by landmines must be thoroughly understood
the close proximity of the exposed bottom section of the vehicles to the landmine (<600 mm) complicates the analysis
To research near-field blast loading effects with respect to blast impulse, the Scientifically Instrumented Impulse Measurement Apparatus (SIIMA) was developed under an Armscor contract.
SIIMA
SIIMA consists of a frame that is rigidly mounted to a concrete base at the CSIR’s Detonics, Ballistics and Explosives Laboratory (DBEL)
A moving mass is mounted in the center of the frame
the load cells connected to the moving mass measures the force-time duration, which is integrated over time to provide the total measured impulse of a shallow-buried near-field blast
SIIMA is currently only used as a comparative measurement as the losses in the spring damper system have not been scientifically quantified.
Scientifically Instrumented Impulse Measurement Apparatus (SIIMA) InItIAL RESuLtS
Eighty-six individual tests were executed in this test programme consuming over 660 kg of high explosives
A minimum of four tests were executed for each test point to evaluate the repeatability of the experimental design and method
All tests with the exception of two varied by no more than 5% from the average impulse value for that test point.
Still footage of SIIMA during a typical test
TM-57 REpLICA MInE vS. 8 kg SuRRogATE MInE
The uncased 8 kg surrogate mine provided higher impulse at all stand- off distances (SoDs) tested compared to the steel cased (confined) TM- 57 replica mine
This confirmed its use as a conservative test threshold for the SA battle- space.
EffECT of ChAngIng D:h RATIo
A definite trend was measured with respect to the impulse effects of increasing the D:H ratio under these test conditions
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EffECT of InCREASIng DEpTh of BuRIAL
An increasing blast impulse trend with increasing depth of burial (DOB) was measured using SIIMA.
EffECT of InCREASIng STAnD-off DISTAnCE
A general decreasing trend was measured with increasing SOD.
CoMpuTATIonAL MoDELLIng
Computational model predictions were executed using AnSYS AutODYn3D™
the quarter symmetry model consists of:
the moving mass section of SIIMA the surrounding air
explosive and the soil pit.
the moving mass is unconstrained and can be accelerated upwards
It is assumed that the blast loading by the gasses is completed within a very short time period
the upward total impulse of the moving mass should correspond with the total impulse recorded by SIIMA.
The computational model reflected about the planes of symmetry CoMpuTATIonAL RESuLTS
the computational model predictions were within 10% or better than actual measured data and within 6% or less with respect to blast load impulse for the uncased 8 kg surrogate mine for increasing stand-off distance.
COnCLuSIOnS
the test data have enabled blast loading prediction formulae to be developed
These tests have provided a first-hand view into the various parameters that affect blast loading when defined as transferred impulse
Predictions can be made using this data for charges closer to as well as further away from the target
Several parameters affect anti-vehicular mine blast output and consequently target response.
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Cpo-0067
Average impulse for various diameter to height ratios for 8 kg surrogate mines
9.0 9.2 9.4 9.6 9.8 10.0 10.2
3 4 5
D:H ratio
Impulse (kNs)
Average impulse at various DOB's for 8 kg surrogates
8.5 9.0 9.5 10.0 10.5 11.0 11.5
0 50 100 150
DOB (mm)
Impulse (Ns)
8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0
900 1000 1100 1200 1300
SOD (mm)
Impulse (kNs)
Average impulse at various stand-off distances
Computation and measurement of total impulse
0 2 4 6 8 10 12 14 16 18 20
400 600 800 1000 1200
Ground clearance (mm)
Total impulse (kNs) .
Computation DOB 50 mm Measured DOB 50 mm
Computation TM-57 DOB 50 mm Measured TM-57 DOB 50 mm
