Embed Size (px)
Citation preview
StUNANNOUNCED1 06! ~SYSTEMS. SCIENCE AND SOFTWARE:
FINAL REPORT (DRAFT)-. SSS-R-81-5143FIIAD-A259 255
CALCULATIONAL INVESTIGATION FOR MINE-CLEARANCE EXPERIMENTS
Charles E. NeedhamJoseph E. Crepeau
systems, Science and Software DP.O. Box 8243
Albuquerque, New Mexico 87198 1993
ji 31 August 1981
Ii CONTRACT DACA39-80-C-0018
Prepared for
Commander and DirectorU.S. Army Corps of EngineersWaterways Experiment StationP.O. Box 631 Ii
SVicksburg, Mississippi 39180 .14
), R. 087ALBUQUERQUE OFFICE - TELEPHONE (505) 265-5895
MAIL ADDRESS: P.O. BOX 8243, ALBUQUERQUE, NM 87198
I 0. BOX 1620, LA JOLLA, CALIFORNIA 92038, TELEPHONE (714) 453-0060
PAGESARE
MISSINGIN
ORIGINALDOCUMENT
UNCLASSIFIED
SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered)- OREAD INSTRUCTIONSREPORT DOCUMENTATION PAGE BEFORE COMPLETING FORM
I. REPORT NUMBER 2. GOVT ACCESSION NO. 3• RECIPIENT'S CATALOG NUMBER
SSS-R-81-5149
4. TITLE (nnd Subtitle) S. TYPE OF REPORT & PERIOD COVER.OFINAL DRAFT REPORT
CALCULATIONAL INVESTIGATION FORMINE-CLEARANCE EXPERIMENTS 6. PERFORMING ORG. REPORT NUMB6R
SSS-R-81-51497. AUTHOR(e) 8. CONTRACT OR GRANT NUMBER(a)
Charles E. NeedhamJoseph E. Crepeau DACA39-80-C-0018
9. PERFORMING ORGANIZATION NAME AND ADDRESS I0. PROGRAM ELEMENT. PROJECT. TASK
AREA & WORK UNIT NUMBERS
Systems, Science and SoftwareP. 0. Box 8243Albngliergine. Ntw M~ixin R714R
1I. CONTROLLING'OFFICE NAME AND ADDRESS 12. REPORT DATE
US Army Engineer Wacerways 31_August 1981Experiment Station 13. NUMBER OF PAGES
P.O. Box 631, Vicksburg, Miss, 39180 7014. MONITORING AGENCY NAME & ADDRESS'II dillrent f=or. "'onfroflin Office) IS. SECURITY CLASS, (of 0l0l ,epo:()
UNCLASSIFIED
ISa. DECLASSIFICATION/ DOWN GRADINGSCHEDULE
16. DISTRIBUTION STATEMENT (o0 this ReporI)
This report was brought to the Library byDr. Guy Jackson, Jr., Structures Laboratoryon 21 December 1991 witlh the request that
17. DISTRIBUTION STATEMEN it be cataloged and placed in the WES Library.This contract report was originally desig-nated as 'R SL-82-1, but due to fundingit was never published.
18. SUPPLEMENTARY NOTES
* IP. XEV WORO• 'C,,ti'nue on evere* side if nces&s:y .w.d idenitify by block number)
Line-Charge Effects, Mine Clearance, Skip Zone, Airblast, Hydro-dynamic Computer CalculaLions, High Explosive Experiments, Line
Charge Experiments, Line-Charge Calculations, and ChargeConfiguration Improvement
20. AB:,TRACT (Continue on reve.-,*e side iI necesstry *nd identify by block numbee)
The detonation of military line charges is being considered as ameans to clear battlefields of implanted pressure-sensitive anti-tank mines. S.ich charges have an undesirable characteristic,however, in that, for distances less than about 1 m from the linecharge, phase duration of the positive overpressure is too shortto detonate the mines. This region in X,'hich mine clearance maynot occur is called the "skip zone".
DD .... 3 1473 EDITION OF I NOV 65 IS OeSO!.ETUC IDDjAN 7; UNCLASSIFIED
SFCUfRIT'," CLA.SIFICA flON OF THIS PAGE (When Date Entered)
PREFACE
This work was sponsored by the U.S. Army Engineer Waterways
Experiment Station (WES) and the U.S. Navy Coastal Systems Center
(NCSC). The work was carried out under Contract DACA39-80-C-0018
between 30 September 1980 and 29 August 1981. The WES Technical
Monitor for this contract was Mr. James L. Drake, Structures
Laboratory.
This work has been coordinated with the line-charge experi-
mental program at WES and is an integral part of that program.
We wish to thank Mr. Max B. Ford, Mr. James K. Ingram, and Mr.
Donald Day for their efforts in supplying and interpreting the
experimental data.
The equation of state for water, which was used in this
effort, is a proprietary code developed and owned by Systems,
Science and Software.
Aoeemu1cn ]•ovI...ITIS MR"AkIDTIC TAB Liunetomobed C
Just ilioation.,-0
DI Kr.ýh uu• o.nj ..
"Avatlabhiliy Codes
Dist speoiea.
11 INi
I CONTENTS
PREFACE ................................................ 1
PART I: INTRODUCTION 5..................................5
PART II: LINE-CHARGE AIRBLAST CHARACTERISTICS ......... 6
Shock History ........................... ... ......... 6Airblast Characteristics ....... .......... #*..... 11Calculation Variations .............................. 16
PART III: CALCULATION DESCRIPTIONS ..................... 23
Calculation Zoning ............................. 25
PART IV: CALCULATIONAL RESULTS ............ 33
Hollow-Charge Calculations .......................... 33Detonation Treatment Effect on Hollow Charges ....... 43Hollow-Charge Variations ............................ 50Additional Calculations ....................... 55
PART V: LINE-CHARGE IMPROVEMENT TESTS ................. 61
Charge Design and Experimental Procedure ............ 61Experimental Results .................................. 61
PART VI: CONCLUSIONS .................................. 67
REFERENCES ................................... .... 68
APPENDIX A: TABULATED DATA FROM GAGE RECORDS .......... 69
Event LCI-II-I ...................................... 69Event LCI-II-2 ...................................... 69
e Event LCI-II-5 ...................................... 70
LIST OF TABLES
TABLE 1: Solid-Charge Calculations ...................... 26
TABLE 2: Hollow-Charge Calculations ..................... 27
LIST OF FIGURES
FIGURE 1: Overpressure versus Ground RangeLine-Charge Calculation 15.12 kg/m ........... 8
FIGURE 2: Overpressure versus Ground RangeIL Line-Charge Calculation 15.12 kg/rn .......... 9
2
I
I LIST OF FIGURES (Continued)Page
FIGURE 3: Overpressure versus Ground RangeLine-Charge Calculation 15.12 kg/m .......... 10
FIGURE 4: Averaged Airblast Impulse versus TransverseDistance froiL Line-Charge Center (M-58 Aland BGV, 30.48-m Charge Segments) ........... 12
FIGURE 5: Surface Airblast Pressure Positive PhaseDuration (Initial Pulse) versus TransverseDistance from Line-Charge Center (M-58 Aland BGV, 30.48-m Charge Segments) ........... 13
IFIGURE 6: Overpressure verss Time at 0.749-m Radius 14
FIGURE 7: Overpressure versus Time at 0.7284-m Radius .. 15
FIGURE 8: Averaged Surface Airblast Pressure versusI Transverse Distance from Line-Charge Center(M-58 Al and BGV, 30.48-m Charge Segments) .. 17
fl FIGURE 9: Overpressure versus Time - Event 2, R=l m ... 18
FIGURE 10: Overpressure versus Time - Event Z, R=2 m ... 19
FIGURE 11: Overpressure versus Time - Event 2, R=3 m ... 20
FIGURE 12: Comparison of Overpressure for VariousInitial Conditions .......................... 21
FIGURE 13: Axial Detonation (Isothermal) ............... 24
FIGURE 14: Radial Detonation (Burn) ChargeConfiguration ...................... z .. ...... 24
FIGURE 15: SAP Solid Charge - Initial MeshConfiguration ...................... .... 29
I FIGURE 16: SAP Hollow Charge - Initial MeshConfiguration ................................ 30I FIGURE 17: SAP Problem 5.0013 - Initial Mesh
Configuration ................................ 31
I. FIGURE 18: Initial Overpressure versus Radius at 0 sec.. 34
FIGURE 19: Overpressure versus Radius at 0.011 msec .... 34
SFTCUIRE 20: Overpressure versus Radius at 0.34 msec ..... 37
I3 i3
LIST OF FIGURES (Continued)
Pagge
FIGURE 21: Overpressure versus Radius at 0.5 msec ....... 38
FIGURE 22: Overpressure versus Time at 0.6-m Radius ..... 39
FIGURE 23: Overpressure versus Time at 1.2-m Radius 40
FIGURE 24: Overpressure versus Radius ................... 41
FIGURE 25: Overpressure Impulse versus Radius ........... 42
FIGURE 26: Positive Phase Duration versus Radius ........ 44
FIGURE 27: Overpressure versus Radius at 0.25 msec ...... 45
FIGURE 28: Overpressure versus Time at 0.75-m Radius .... 46
FIGURE 29: Peak Overpressure versus Radius .............. 47
FIGURE 30: Overpressure Impulse versus Radius, ComparingDetonation Methods for Hollow-Charge Problems 48
FIGURE 31: Positive Phase Duration versus Radius ........ 49
FIGURE 32: Peak Overpressure versus Radius .............. 52
FIGURE 33: Impulse versus Radius ........................ 53
FIGURE 34: Positive Phase Duration versus Radius ........ 54
SFIGURE 35: Overpressure Impulse versus Radius........ 56
FIGURE 36: Peak Overpressure versus Radius .............. 58
FIGURE 37: Impulse versus Radius ........................ 59
FIGURE 38: Positive Phase Duration versus Radius ........ 60
FIGURE 39: Overpressure versus Radius, Hollow Charges ... 63
FIGURE 40: Impuls ....................................... 64
FIGURE 41: Overpressure versus Radius, Solid Charges
L
4I,
1 CALCULATIONAL INVESTIGATION FOR MINE CLEARANCE EXPERIMENTS
1 PART I: INTRODUCTION
I 1. The Marine Corps M58 Al and the British Giant Viper(BGV) line charges are under consideration as viable means for
pressure sensitive antitank mine clearance. An important
deciding factor lies in the elimination of an undesirable
characteristic of the charge, referred to as tne "skip zone".The skip zone is a region extending axially down the length
i of the charge and perpendicularly to a radius of about 1 m,
in which some of the mines fail to detonate. The reason
seems to lie in thp charge airblast characteristics in this
region. Here the overpressure waveform is defined by a high-amplitude shock with an extremely brief positive duration.
This results in a lowered overpressure impulse causing mines
to remain untriggered. Thus, the main objective of this calcu-lational effort was to determine an improved charge configuration
that would enhance the overpressure impulse in this region to
effect reliable mine detonation.2. The U.S. Army Engineer Waterways Experiment Station
(WES) has conducted several line-charge tests in order toobtain experimental airblast data 1 . In conjunction, Systems,
Science and Software (S 3) has performed various one-dimensionalhydrodynamic computer calculations of detonation of the line
charges. The following pages introduce the calculations and
present comparisons of data from both efforts. Some possibleimprovements to the charge configuration to minimize skip zone
effects are suggested.
I.
I PART II. LINE-CHARGE AIRBLAST CHARACTERISTICS
3. Under a previous contract with WES, S3 made hydro-
dynamic calculations to determine the validity of the experi-
mental data and the reason for the existence of the skip zone.
The Sph ical Air Puff (SAP) one-dimensional, multimaterial
hydrocode developed at the Air Force Weapons Laboratory (AF)W),
was used for the calculations 2. SAP was run in the Lagranqian
I mode using cylindrical geometry. An equation of state for
pentolite was used to calculate the hydrodynamic parameters
I during the high-explosive (HE) burn. "Snapshots", logarithmi-"
cally spaced in time, of pressure, density, velocity, and
temperature were taken. These snapshots enable one to follow
shocks as they propagate through space. An insight into the
causes of certain phenomena seen in experimental data is thus
gained. Points fixed in space, or stations, were also placed
at several radii of interest. Hydrodynamic variables we-
I monitored at each s-1-ation to obtain parameter versus time data.
These data are used for direct comparison with experimental
3 gage records.
I Shock History
4. An understanding of airblast shock formation and
I' propagation may be obtained by "walking through" the shock
wave history from one calculation. SAP Problem 5.0002 is a
I'• 15.12 kg/m line-charge calculation and its airblast history
will be used for this purpose.
5. Initially, in the charge region, the radial velocityis zero and the pressure is large (by five orders of magnitude)
compared to ambient air pressure. The high pressure is due
to an initial energy density of 5.155xi0 1 3 ergs/kg. These
initial conditions cause large accelerations and hence material
velocities of up to 5 kmps by the time the shock front reaches
6I
two charge radii. A rarefaction wave reacher7 the charge center
at the time the shock front reaches three charge radii. The
high-density detonation products expand and ocol while the air
is swept out and compressed into a thin shell surrounding thedetonation products. When the shock reaches seven charge radii,
the pressure in the shell of air is comparable to that insidethe detonation products and the air density is ten times atmos-
pheric. When the shock reaches twenty charge radii, the detona-
tion products have expanded to form a cylindrical shell with anearly evacuated center. A shock begins to form on the inner
surface of the shell while the thickness of the shell increases
as it grows radially.
6. The inner surface of the high-density detonation
products stops expanding when the shock reaches eighty charge
radii. The outer edge of the detonation products has reiacheda distance of fifty radii and the inward facing shock is at
forty radii. The in.ward facing shock accelerates inward,
gaining strength due primarily to cylindrical convergence.
7. The detonation products stop expanding and begin to
contract when the shock reaches 100 charge radii. The inward
moving shock reaches the axis of symmetry when the air shock
reaches 130 charge radii (Figure 1). Upon reaching the center
the shock reflects to a pressure greater than exists in the
air shock (Figure 2). The reflected shock moves outward and
rapidly decays (Figure 3). Other minor shocks continue to
reverberate as the air shock advances and decays.
8. It is the formation of the ring of detonation products
which causes the small impulse and short duration at small radii.
The overpressure impulse and duration increase at larger radii
because the detonation products reach their maximum radius and
the inward moving shock spreads the eneaj.y inward from the high
density ring of detonation prod'acts.
I
Problem - 5. 0002S'rime - 4.500xlO- secCycle - 11785.0Maximum - 5.5488xi05 Pa
6 Minimum - -1.0106x10 Pa.
I U-)
ý4
(0
R u Radius of(1 Detonation Products Ai hc /rn
50 Charge Radii 00Ch~argeRai
~~Inard oving Shock
10°oi0 200 300 400 500 70o-0
Radius (cm)
FIGURE 1. Overpresssure versus Ground Range
Line-Charge Calculation 15.12 kg/m
IiI
8
1 60
I Problem - 5.0002Time - 5. 30x01Q seciycle - 12122.0Maximum - 4.6571x10 5 PaMinimu•n - -5.6816xi0• Pa
S40
Center Reflected ShockS30
2'UI1 20
O Radius 0,,L/Detonatio roducts Air Shock Front
I 50 Charge Radii 100 Charge Radii
0 100 200 300 400 500 600 "700 800
Radius (cm)I-
Ii FIGURE 2. Overpressure versus Ground RangeLine-Charge Calculation 15.12 kg/m
II
I
I 5 0on I
I - Problem - 5.0002Time - 6.500x10 3- secCycle - 12536.0
40 Maxim= - 3.7217-,10 PaMinimum - -2.6277x104 Pa
I 30
I2 Iý4 20
I -i_.Il ILI .
U) Center Reflected ShockwwIRaiRadius of
Detonation Products Air Shock u ront-
0
50 Charge Radii 100 Charge Radii
I .-Lo I - -I0 100 200 300 4100 5 00 600 700 800 900
IRadius (cm)
I IFIGURE 3. Overpressure versus Ground RangeLine-Charge Calculation 15. 12 kg/ni
10
I Airblast Characteristics
I 9. An important characteristic of the line charge is
observed when plotting positive phase overpressure impulse as
a function of radius (Figure 4). For a charge density of
7.56 kg/m, the experimental data reveals an impulse "well"
centered at about 1 m (the extent of the skip zone). A peak
occurs at 3 to 4 m before the impulse falls off again.
10. SAP Problem 5.0002 is the first line-charge calcu-
lation that was made. It is compared to the data in Figures
4 and 5. The charge density was doubled in the calculation
to simulate a detonation on a perfectly reflecting surface.
A' though the calculation falls below the data, the same charac-
teristic decrease in impulse is seen, now centered at about
0.7 m. The corresponding peak occurs at just under 3 m.11. A study of the overpressure positive phase duration
versus radius reveals an important line-charge characteristic
(Figure 5). The prominent decrease in duration, starting at
a radius of about 0.4 m and e.:tending to about 1.8 m, with
a minimum at 1.2 m, was not readily apparent in the experimentaldata. A noticeable phase difference is apparent between theimpulse and duration minima. This is due to the overpressure
waveform shape at the two points. Figure 6 is the overpressure
time history from the calculation Pt 0.749 m from the charge
center. Overpressure positive phase duration is defined as the
difference in shock arrival time to the time at which the over-pressure falls below zero. In this region, the waveform is
characterized by a high-pressure spike followed by a long "tail"
of low but positive overpressure. As the shock moves out
radially, the ring of compressed air encircling the detonation
productF begins to stretch out and drop in pressure. The
detonation products follow closely behind the shock and the
drop off in pressure occurs abruptly at the inside edge. This
behavior characterizes the overpressure waveform at 1.284 m in
Ii i1
I0
000
Ln 0
IN O
00P0)>
~0 0
Lfl 00 @a0i.01
@0
U) -00
4-)
$0,
4-)
0 0
IQ (d 0).
eP4 la
a) 0 d
4v4-4 U
II-(s-vdN)aslnd,
7 H2
II
I1001i 0 M-58 Al
D BGV- Problear. 5.000
.0
.0 0
100
I 1 00O
I C0
"4-/
I,
I It0
0 1 II I I t l I i I l_ O I I It I !
0.1 1 10 50IL. Radius (i)
FIGURE Surface Airblast Pressure Positive PhaseDuration (Initial Pulse) versus Transver eSDistance from Line-Charge Center (M-58 A..and BGV, 30.48-m Charge Segments)
13
14 FI
12 Problem 5.0002
I ~10
p4
01)
$44
2
I0 _0
is 20 25 30 35 40 45 50 55
Time (sec) (x105S)
L>
IO
FIGURE 6. Overpressure versus Timeat 0.749-m Radius
14
9
7.5 - Problem 5.0002
6
0 4.5
0 3
Ii -1.5
-3130 36 42 48 54 60 66 72 78
I Time (sec) (xl0- 5 )
FIGURE 7. Overpressure versus Timeat 1.284-m Radius
1' 1I-I"
IIfL.. 15
IFigure 7. In spite of the shorter duration, a larger impulse
results because of the waveform shape.
12. The consistency between experiment and calculation
is further demonstrated by the results in Figure 8. Here, thepeak overpressure from the calculation falls along the BGVdata to a radius of 6 m. No peculiarities in the overpressure
profile are apparent in either experimental or calculational
data.
13. Overpressure versus time comparisons of the calcula-tion with experimental data are shown in Figures 9, 10, and 11.
I The experimental data show some gage noise, oscillation and
overshoot. The calculation shows the arrival of the expanded
detonation products as a sudden drop in overpressure at the
1- and 2-m stations. This is because the calculation modelsthe interface as a boundary and does not allow mixing of the
I air with detonation products. The detonation products do notreach a distance of 3 m, therefore the comparison at that range
shows a classical air shock decay in both experiment and
calculation.
I Calculation Variations
14. Three other ca]culations were run with variations in
detonation treatment, density and initial detonation energy.Problem 5.0003 treated the detonation by allowing a cylindrical
Ii detonation wave to advance radially outward through the explo-sive. This procedure is further described in PART III. Pro-
F- blem 5.0004 was initiated with a uniform detonation energy of
5.86xi01 3 ergs/kg (as opposed to 5.155x10 1 3 ergs/kgm in Problem5.0002) to determine the effects of a higher-energy explosive.
The third calculation, Problem 5.0001, used an increased chargedensity of 23.01 kg/m. The purpose of Problem 5.0001 was to
approximate a high-energy explosive uniformly mixed with 34
percent inert materials.
15. Peak overpressures versus radius from all three calcu-lations are compared with those of Problem 5.0002 in Figure 12.
I1j 16
30 I I I I _ , ,T" '
- 1 0 M-58 Al0 BGV
10_ - Problem 5.0002
1 -
00
I 0
m •')
.0.1) 0
00
0.1 .... ...
I1•. 0
0.03 ! I I , __________ I...I___ _ 1
0.3 1 10 100
I Radius (m)
FIGURE 8. Averaged Surface Airblast Pressure versusTransverse Distance from Line-Charge Center(14-58 Al and BGV, 30.48-m Charge Segments)
Ii1 |17
IIII
I Data
iII /Experimental Data
S Calculation
I4
0 AAA__ _ _ __ _ _
I I I0.0020 0.0022 0.0024 0.0026
Time from Detonation (sec)
|i.
FIGURE 9. Overpressure versus Time - Event 2
R= 1 m
II
181K
6U
S4 Experimental Data
U)U)II
• $3
S2 /S Calculation
0.0020 0. 0024 0. 0028 0. 0032
Time from Detonation (sec)
• FIGURE 10. Overpressure versus Time -Event 2
I R = 2 m,
F LI0- 119I
I . . , , i i i i I I I I I I I I I
3
S2-Experimental Data
I 3S Calculzcion
d)$4
V I
T imefo Deoato (c
20
II
2 0 1I I I I I I I I
* Problem 5.0002--- Problem 5.0003I - Problem 5.0003
10.-.---- Problem 5.0004
10
I K" Ž-
0.5 10
Radius (m)
I -~
FIGURE 12. Comparison of overpressure forVarious Initial Conditions
21
I
Minor differences due to detonation treatment (Problems 5.0002and 5.0003) are seen in this ciuparison. Slightly higher
pressures from the burn calculation inside of 0.5 m resultfrom the larger amount of kinetic energy generated by burning
the explosive. Very little difference can be seen outside the0.5 m radius.
16. Some enhancement is obtained by using the same amountof a higher-energy explosive (Problem 5.0004). An increasewhich scales as the square root of the energy density ratioswas obtained as expected.
17. The presence of large amounts of inert materialcombined with a higher-energy explosive, as in Problem 5.0001,resulted in a noticeable increase in overpressure at radii
beyond 1 m.18. The ability of the code to closely model line-charge
phenomena gives credence to previously questioned experimentaldata and confidence in the continuation of line-charge calcu-lations. An understanding of the line-charge airblast charac-
teristics was obtained from the calculations as we-l as abasis for comparison with future calculations. As previously
mentioned, the main effort was to enhance the overpressureimpulse within the region of the skip zone with a minor effecton airblast parameters at the greater radii. The increase inimpulse can be achieved by increasing the overpressure positivephase duration in this region. PART III describes S31s approach
to the solution and includes a "directory" of calculations andtheir descriptions.
2
U 22
PART III. CALCULATION DESCRIPTIONS
19. A total of 12 line-charge calculations were inade.
The purpose of the fir:st four calculations was to determine
tile ability of the code to simulate a line-chargeb The final
eight are considered to be line-charge-improvement calculations.
A breakdown and brief sunmtary of each calculation follows.
20. In order to simulate charge characteristics in the
code, several simplifying assumptions had to be made. The
charge was assumed to be an infinitely long, solid cylinder
of 100 percent HE mass. This assumption ignores end effects
of the charge and any inert mass surrounding or inside the
charge. The input charge mass was twice that of the experimental
mass in order to simulate a surface detonation on a perfectly
reflecting surface. The detonation of the charge was treated
in two ways. The first method simulates the situation if a
planar detonation wave travels axially down the charge. For
calculations using this method, Lhe initial HE region is a
high-energy density isothermal region of burned HE material.
The second treatment simulates a cylindrical detonation wavestarting at the inner HE radius and burning outward in theradial direction. The initial conditions in the HE regiop
include an inner zone of burned pentolite (properties identicalto those in the axial detonation calculations) and surrounding
zones of low energy, unburned HE material at ambient air pre3sure.
A calculation using this treatment will be referred to as a
"burn" calculation, whereas the convention for the a.cial detona-
Eion will be "isothermal".
21. Both detonation treatments are correct. It is lotclear, however, which treatment models the experimental situation
more closely. The most appropriate treatment is dependent on
where and how the charge is detonated. A representation of the
two treatments is shown in Figures 13 and 14.
22. All calculations can further be divided intc t.- groups
based upon tne charge configuration:
* -23
I41High-Energy Isothermal p = 1.66x10 3 k9/1113
ExpIlosive Material E= 5-15X1t0 1 3 ergs/kg
Unburned HE Mat~erialE =i.0O,*10i1 ergs/kgp =1.66X103 krg/rn 3
U5 1
I-1Ul 4 a-LlD~nton(un hreCniuaii
I2
II
I a. The "9olid" charge.
b. The "hollow-center" charge.
Table 1 lists the solid-charge calculations and pertinent
information regarding initial conditions for each. Table 2
describes the hollow-center-charge calculations.
I Calculation Zoning
23. The solid-charge calculations used a solid cylinderof HE surrounded by ambient air (Figure 15). The HE region
is made up of approximately 100 zones of 0.5 mm size. The
charge is surrounded by ambient sea-level air. The first few
7ones at the HE air interface are large and decreasing in size.
This is necessary due to the compression of the zones as theshock passes through. These decreasing zones are followed by
about 100 to 150 zones of constant size and then increasing
size zones at a constant expansion ratio out to a radius ofabout 14 m. Problem 5.0012 is the only deviation from the
above configuration among the solid charge calculations. A
2-cm layer of low energy, dense air surrounds the charge in
Problem 5.0012, with ambient air in the rest of the grid. '.'hismodification was made to determine the effect of surrounding
the charge with a layer of dense, inert material.
24. The basic configuration for the hollow-center charges
is shown in Figure 16. The center four to five zones contain
air at ambient pressure, with The volume of this center region
varied in three different calculations (Problems 5.0006, 5.0007,
and 5.0008). From thirty to sixty zones of HE, depending onthe calculation, surround the air zones. The HE region is again
surrounded by the decreasing, constant, and then increasing
ambient air zones. Problem 5.0013 is classified as a hollow-
center calculation, yet has a slightly varied charge configura-
tion (Figure 17). This configuration is referred to as a"double charge". The center zones are of HE surrounded by tw:o
225
-!
41-) -r-
44- 4-0
>1-
9: 0
U) 0~r >1r. >1 U) d
.m $4 IN40) *Hi LA
-I t o-i O
>T OD 00) D
urn :3 14
CDXIIl 9 r. :-- o Dr 11
4-)
I 0l) 04.~J 0 iý4) a) 4J Q)OJý4
4- D 0 0 -l0 0
WCD LA LA LA LA
tjý - % Ln Ln U') LO
.. ri -* * *
ýX (Y LA LA LA LAN HA H- H4 H
H> CD4 (D C
H0 0 0 0o 0D HD
04: 0 0 0 0
a4 z LI LO LA LA V;
26
EA 0
0 0a~r4~- $40r-
4J -P4 a)4-4(U 0 9
U) 4-) (1 lc0 W )
0'- r-4 Hrd tci0r4~~~% (d(:m Of
.r4 0 0 X- H "I .i 4) rN.O
$4 ~ ~C4J X ONri U lýC
(P) 0X U -U0 p0 (0
$4. C>4-4 (D$4 14LD cz
0 0 0 0 (d 04 .Z Z Z Z ý::UOP04 U*'aIOW
to) H r-H00 4. It 'Ud'
4rii $4 $4 $4
H0' (a~ 4-) 4-) .4-)-W Q) $4 $4 $4 0 0 0
0J4) PI 0 cn 0 wf)N~~~~ H -
'U 4. Q) $4- ON H cN
4. -tJ 4 r4 LOUOrI -
*1~~~~) (P4 '-I-. r- N tIL 0 ) 0 0
orp-I 00 0n r- 0 0 0 0
C)'d C) 0 0D eC,
I-4U~ 0m 0 0 00
010 r U) LA ) mA LA
Nl$4 . N N~ N'f N
r-4 W. 0D 0 0 0) 0C) C) C> 40 C) (
27
ON
ci)
.r t.4r (d
o 0 0 40) 4 -I MoM4. ."14)w 09
0. 04-'Q '1440 r
a) r-4 0 ý0 a) 4r-) OH 0 04 0 ~-H H ("4
0 4.). 4.
4-)
0-it 4-)
4J0) (1)M
IME-1 HI
.H-
40 0 'U IX0 *l
4.) l 0
(ULO.4 0 0L
0t (1) dO-E 0
(1) -AU
0- 0fW-
H N4 4-) t7'r- (D ri 0Q) -~ tn10 0- 0O0C iC
0rz
0 0
>1
,) -N r-4
.Q 0 -
0~
28
Explosive Material15.12 kg/m
Ambient Air Zonesof Decreasing Size
Expanding Zonesfrom Zone 207zones0. O C'mto Zone 400
"- izones
FIGURE 15. SAP Solid Charge Initial Mesh Configuration
29
Explosive Material 15.12 kg/m
AMBIENT AIR IAMBIENT AIR
IAIIr
".30 zone.,,s-
FIGURE 16. SAP Hollow Charge Initial Mesh Configuration
I3I'
I 30
DExpoiveA. Mate grial Double Charge Calculation
LFT7 Dese ir p= 10 k/m310 lb/ft Charge
AMB1IENT AIR
Ojrn
FIGURE 17. SAP Problem 5.0013 Initial Mesh Configuration
3'
zones of air and, in turn, surrounded by several more zones
of HE. A low energy, dense air is used between the two HEregions to simulate the presence of a low density foam in
this region. The final HE region is surrounded by ambient
air out to a radius of just over 13 m.25. Each of the calculations was run to a time when the
overpressure positive phase was complete inside a minimum
distance of 1.75 m. A complete set of station plots was made
for each of the calculations. Tables and plots of peak param-
eters from each station were made for direct comparison. Theseare discussed in PART IV.
I.
32
SPART IV. CALCULATIONAL RESULTS
26. The hollow-center charge calculations were the first
attempts at increasing the overpressure impulse. Stretching
the ring of detonation products is the means by which the
impulse should be increased. During the hollow-charge detona-
tion, an inward moving shock is created by the detonation
products as they move into the less dense air zones in the
center of the charge. This shock will reflect from the center,
pass through the ring of detonation products, now much wider
than in the case of the solid charge, and catch up to the main
shock, hopefully outside the skip zone. The stretched detona-
tion product ring plus the additional reflected shock should
yield a higher impulse in this region.
Hollow-Charge Calculations
27. Three separate calculations of this type were made,
varying only the volume of air in the charge center. Problems
5.0006, 5.0007, and 5.0008 contained center volumes equal toone, one half, and two times the charge volume, respectively.
Each calculation was carried out to a time at which the positive
phase duration was complete inside 3 mn.
28. The actual shock interactions can be seen by following
the results of Problem 5.0006 in time.
29. Because Problem 5.0006 is a burn calculation, the
initial overpressure versus radius profile shows a single zone
of high-energy detonation products (Figure 18). As the HE burns
to the outer surface, detonation products on the inner surfacemove inward, compressing the air in the center of the charge.A high-pressure shock is generated in the air which reflects
off the center when the main air shock has reached a radius of
0.143 m (Figure 19). The reflected shock drops in pressure as
it advances radially through the detonation products. Thereflected shock reaches the outer HE-air interface when the
33
r 00
p0,
a44
4.
244
1*00e 01"d);D:1ISS;DdJOA
34)
ji C: C>
(N i
H
O0O)
I ~-4 ~*1 '~coHe
H V
WI ':4
00 k
gl 35
I
main shock front is at a radius of 1.3 m (Figure 20). As the
reflected shock moves into the air, it generates the large
secondary pressure spike shown in Figure 21.
30. The time history results generated by this reflected
shock are represented in Figures 22 and 23. The overpressure
time history at 0.6 m in Figure 22 shows the reflected shock
as a low amplitude secondary shock as it passes through the
detonation products. It is the presence of this secondary
Ii shock which causes the increase in impulse at small distances.
At a radius of 1.2 m (Figure 23), the reflected shock is outside
the detonation products and produces a high amplitude, double
peaked waveform.
31. At later times, a second reflected shock similar to
that produced by the solid charge (as mentioned in PART II) can be
seen reflecting from the charge center. This occurs at extremely
late times and is not seen in the time frame of the experimental
pressure time recordings.
32. A plot of peak overpressure versus radius for the
three hollow-charge calculations (Problems 5.0006, 5.0007, and
5.0008) as compared to the solid-charge calculation (Problem
5.0003) is given in Figure 24. Overpressures are slightly
higher inside 0.8 m for the hollow charges because the charge
surface is closer to each station. As the main and inward
moving shocks separate, a slight decrease in pressure below
the solid charge data is seen. At a radius of 1.8 to 2 m, the
* pressure suddenly rises to the solid charge data marking the
point where the reflected inward moving shock has caught up
with the main shock. The distance at which the reflected shock
catches up ..s dependent on the center charge volume: the
smaller the volume, the earlier the shock catches up. Beyond
the joining of the two shocks, peak pressures are in close
agreement with the solid charge data.
33. The most encouraging results of these calculations
are shown in Figure 25. Here, a definite enhancement is seen
3| 3
*4 10
04.
r-4 -4 Ln 4
*U U)
CC)
IIýp4 -'I
90NU~l ;qnsat)zA
'~o37
* H H
Ir II .44
C\) 0wN
H0rJ2
0 0
(14U
N 0- 0-
II
16 1 1 1
I 14 Problem1 5.0006
12 L
C
0
U80
iN
'4
0 4-
0 4
2 Reflected Shock
0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0
Time (sec) (x10-4)
FIGURE 22, Overpressure versus Time at 0.6-m Radius
39
IIi
I70 1 V I
I 60 Problem 5.0006
I i 50
x 40 ~.,Reflected Shock
$4 30
S20
S10I 0o_
0 -10.
0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0Time (sec) (xl0 4)
FIGURE 23. Overpressure versus Time at 1.2-m Radius
I.4I °
100
i - Problem 5.0003. Problem 5.0006.i Problem 5.0007
o 0 Problem 5.0008
7 IN.
WTI
1 ,
UX7
I
0-I i0 0 10 1
Ii Radius (m)
FIGURE 24. Overpressure versus Radius
"M 4!M
II" 07_ i1 1I I I I I " i" I1I I I
I --- Problem 5.0003
-- Problem 5.0006
* Problem 5.0007
A Problem 5.0007
o Problem 5.0008
11
I
I _o \\\\
I. ,. I o .................. II I I l l
FI-U \ 5. OvrrsueIpls essRdu
I.
'll ! • l ] I I I I IA
.. 9
in overpressure impulse, as large as a factor of two, inside
the 2-m radius. Once again, the hollow charge data mimics the
solid charge data after the reflected shock catches the main
shock. The positive phase duration comparisons in Figure 26
show a significant increase in duration for hollow charges.
A factor of 2.5 increase is seen at the 1 m radius from Problem
5.0009.24. The hollow charge has certain airblast characteristics
of its own. The data reveal that the greatest impulse enhance-
ment occurs in Problem 5.0008, from the charge with a center
volume of twice the charge volume. This would seem to indicate
that the larger the center volume, the greater the increase in
impulse. There is, however, a drawback to this reasoning (aside
from the problems of constructing a charge of this configuration).* 35. As the main and reflected shocks separate, a decrease
in overpressure begins to develop between the two shocks(Figure 27). The overpressure goes negative for some time
before the reflected shock passes through this region. Theresult is a pressure-time waveform as shown in Figure 28. The
depth and duration of the first negative phase increases as
the center volume of the charge increases. A trade-off point
exists, therefore, where this brief negative phase negates the
added impulse due to increase in the center volume.
Detonation Treatment Effect on Hollow Charges
36. Problem 5.0009, with isothermal initial conditions,
was run to determine the effect of detonation treatment on the
hollow charge and as a basis of comparison for Problems 5.0010and 5.0011. Figures 29 through 31 compare the results ofProblems 5.0006 and 5.0009.
37. The results are similar to those for the solid charge
detonation comparisons. Initial pressures for the isothermal
detonation are lower than those for the burn calculation, but
are higher at distances beyond 1 m. The impulse for the
43
I
I° iJ J • iI I I" Iil I I I I 1,1
_--Problem 5.0003 -
i Problem 5.0006SProblem 5.0007
Problem 5.0008 4 0
I~I//A0
0 0I0,41o
• 0 I-
0) I
000
0- - o I
I .. •
10k 10 0 1
00/
444
i: \ /I ~\ //
L' 10-1 I I lJ II ! I LLL 1
10"-1 10 101
I Radius (in)
I FIG-URE 26. Positive Phase Duration versus Radius
Ir44r
01
co
ko
oo 00ý
0 U' e
o N C>wg4)
Cli
LI
co OCO -c i C
0 *Lt'3d) 0as~ a a
4)45
III
I ~14-~
12 Problem 5.0008
S10
Ii
aaI 044
Qiý4 44
0
I 2-
7,Ref lected Shock
Brief Negative Phase
0 2 4 6 8 10 12 14 16
Time (sec) (kxiO
I ~FIGURE 28. Overpressure versus Time at 0.75-mn Radius
46
t *Problem 5.0006AProblem 5.0009
A
A'A
II _ A ZAAA
I A
0 ""iA
A
10 6
31 0
I FIGURE 29. Peak overpressure versus Radius,47
107 ImrF -F-1 r-FF I I I I I iT IIF
_ Problem 5.0006(HE Burn)
A Problem 5.0009(Isothermal)
A
10
AA A_ _ _ _ __ _ _
10 L
48
101I 100 i01
Radius (in)
FIGURE~ 30. Overpressure Impulse versus Radius, ComparingDetonation Methods for Hollow Charge Problems
48
I
O I 01 ; 'I II_
i * Problem 5.0006A Problem S.0009 0 *
10 0, .
Ii "'AA AA
AA
10 10- i10
S~Radius (m)
FIGURE 31. Positive Phase Duration versus RadiusI,
I
isothermal calculation lies above that of the burn calculationinside 1 m, in spite of the fact that the positive phase dura-
tion shows very little enhancement. This is due to differencesin the overpressure waveform shape in this region.
38. Because an isothermal detonation lacks the initialkinetic energy of an HE burn, larger amounts of energy remain
in the center of the charge for a longer time, causing pressuresto remain at a high level for a longer time and adding to the
impulse. The impulse from the isothermal calculation yieldsto the higher impulse from the burn at about 1 m. Data from
Iboth calculations shoul," come together at greater radii.
I Hollow-Charge Variations
39. Based on the results of Problems 5.0006 through 5.0009,
two additional hollow-charge calculations were made. Previous
hollow-charge calculations revealed that a region of inertmaterial (air) placed in the charge center yielded a significant
increase in overpressure impulse in the skip zone. It was notedthat an increase in the volume resulted in a proportionalI increase in impulse. The success of the hollow charge led toan expansion of the principle in the next two calculations.
40. Because of the premature negative phase which wasnoted in Problem 5.0008, due to the large center volume, we
placed a denser material in a smaller center region in Problems
L 5.0010 and 5.0011. The predicted effect was a slowing of the
I inward moving shock resulting from the expansion of the detona-tion products. Impulse enhancement without the effects of apremature negative phase was the desired result.
41. A preliminary attempt to incorporate an equation ofstate for polystyrene and polyurethane foams3,4 into the SAPcode failed. Incompatabilities with the hydrocode were contri-buting factors to the inability of the equations of state to
I perform properly in the region of interest. A suitable equationof state for water, however, was readily available and adaptedfor use in SAP.
50
I
I 42. Problem 5.0010 calculated hollow-center line charge
effects using water in the center volume. A high density,
low energy air medium (po = 100 kg/m 3 , E = 2.43x 10 ergs/kg)
was used in place of foam in Problem 5.0011. The center
volumes for both calculations were made equal to the charge
volume. As a means of reference, airblast parameters from
I both calculations are compared with Problems 5.0002 (the solid
charge) and 5.0009 (the hollow-center charge) in Figures 32,
Ii 33, and 34.
43. In Figure 32, the overpressure profile of Problem
5.0010 follows along Problem 5.0009 to 1.2 m before dropping
to a lower pressure level. The jump in pressure seen in
Problem 5.0009 is not as pronounced in the water center calcu-
lation, meaning that the reflected shock has been weakened
somewhat. This weakening is attributed to the large amountsof energy lost in converting the water to steam.
44. This loss of energy is apparent in impulse and
I positive phase duration comparisons in Figures 33 and 34.
Impulse from Problem 5.0010 lies between the solid charge andI the hollow-center charge out to a radius of 0.75 m. At this
point the water-center calculation intercepts and even falls
below the solid charge data. Duration comparisons show onlyslight enhancement above the solid charge data between 0.6
and 1.5 m.
45. Overall results of Problem 5.0010 show some enhance-
ment in impulse due to the hollow-charge configuration. The
use of water in the center region, however, does not produce
the desired effect when compared to a standard hollow charge.
5 46. What is the effect of a less dense material on the
hollow-charge airblast? Problem 5.0011 answers this question
by revealing little to no effect, at least for a material
100 times denser than ambient air. In this calculation, air
properties were used to simulate a polyurethane air mixture
(foam) in the charge center. Air occupied the center region
I
108- ____ _
----- Problemi 5.0002A Problem 5.0009* Problem 5.00100 Problem 5.0011
10 7
:3)
10.
10 100 101
Radius (mn)
FIGURE 32. Peak overpressure versus Radius
I07• . ... ..
I
10I I 7 1 1 11
I-Problem 5.0002A Problem 5.0009* Problem 5.0010_ Problem 5.0011
III
S 106
•-4 4
S10• L J J jI I _1 I I I i I I I I10
10-1 10 101
Radius (m)
FIGURE 33. Impulse versus Radius
II
Problem 5.0002A Problem 5.0009*Problem 5.00100 Problem 5.0011
S10-
10 -1 1 1 1 01
Radiuis (i)
FIGURE 34. Positive Phase Duration versus Radius
54
3at a density of 100 kg/mr. In order to obtain ambient air
pressure, the energy of the air was significantly reduced.
Comparisons with the hollow-charge calculation (Problem 5.0009)
in Figures 32 through 34 show no effect on any of the airblast
parameters.
Additional Calculations
47. Two final line-charge improvement calculations were
made. Problem 5.0012 is a solid line-charge calculation with
a layer of dense material (air) around its outer surface. The
purpose of this calculation was to determine the effect of a
layer of inert material surrounding the charge. Problem 5.0013
is a variation of the hollow-center calculations. This calcu-
lation employed the charge configuration shown in Figure 17,
PART III. The main purpose of this calculation was to deter-
mine if an even greater impulse enhancement could be achieved
through complex shock interactions which take place in the void
region between the two HE regions.
48. Problem 5.0012 consisted of a 15.12 kg/m solid line-
charge surrounded by a 2-cm layer of dense, low energy air of
properties identical to those in Problem 5.0011. The detonation
was treated as an isothermal detonation, therefore its impulseprofile is compared to those of Problems 5.0002 and 5.0009 in
Figure 35. Unlike 2roblem 5.0011, the presence of the dense
material in this exterior region afforded a small increase in
impulse to 1.5 m. Enhancement was riot as great as that achieved
in Problem 5.0009, however.
49. The double-charge calculation (Problem 5.0013) w;asthe final line-charge improvement calculation. Half the total
charge mass was placed in each HE region. The purpose of the
double-charge configuration was to stretch the region containingdetonation products and to generate multiple shock interactions
in this region. The results of such interactions were too
complex to predict without the hVdrocode calculation.
55
4xl0 3
-- Problem 5.0002A Problem 5.0009ZA Problem 5.0012
A
10 3 A
I A
AA
AA
I 102
I
0.1 1.0 3.0
Radius (m)
IFIGURE 35. Overpressure Impulse versus Radiuis
5I
56
!
I50. Figures 36 through 38 compare airblast parameters
from Problem 5.0013 with those from Problem 5.0009. A few
subtle differences occur between the two calculations. Positivephase overpressure comparisons reveal that double charge pres-
sures are lower out to 0.5 m. Inward and outward-moving shocksfrom both HE regions are generated during the detonation. Theshocks reflect from each other in the region of air between thetwo HE regions at early times. The reflected inward movingshock catches up to the main shock at about 0.6 m, as indicated
- by the rise in peak pressure in Figure 36. An almost undetect-able rise in pressure occurs again at just over 2 m, marking
the point where the second shock has caught the main shock
after reflecting from the charge center.
51. The secondary shock interactions from the doublecharge have very little effect on hollow-charge impulse, as
is evident in Figure 37. The impulse profile from the doublecharge lies on top of the hollow-charge data of Problem 5.0009.Overpressure positive phase duration also shows only a slightdifference, except in the region 1.2 to 2 m, as demonstrated
in Figure 38.
52. Close analysis of the double-charge calculation doesreveal one important point. The inward moving shock of the
outer HE region overwhelms the outward moving shock of theinner HE region when they reflect from each other. The reason
is that the inward moving shock gains strength due to cylind&:icalconvergence as it moves inward. When the shocks reflect, the
IL outward moving shock is weakened significantly. In order tostrengthen this shock, logic suggests a reduction in the chargeI. mass in the outer HE region. This would also tend to increaseimpulse at small radii. A trade-off point exists where the
proper ratio of inner-to-outer region charge mass will yield
maximum impulse enhancement.
57
o108 I1Ii7 I I I i_
AProblem 5.0009*Problem 5.0013
A A+ • A
107@'"
AA
AA
10~
hi
I II ii-I I 1 11
10-1 ioO 101Radius (in)
L..
FIGURE 36. Peak Overpressure versus Radius
58
I
10 I7 1! ..1 1 1 _
•AProblem 5.0009*Problem 5.0013
I6
It 101
AAA
101-0 1I I 1 1 1 1110- 1O0 10
Radius (m)
FIGURE 37. Impulse versus Radius
59
I
i 101 I I I I A I i i i i I ii .
A Problem 5.0009Problem 5.0013
III
I-i .~100
A!* t
AIIAAA
*A
A
" 10- II I I 11111I
10-1 100 10
i. Radius (m)
FIGURE 38. Positive Phase Duration versus Radius
I60
i"
PART V. LINE-CHARGE IMPROVEMENT TESTS
i 53. Based on preliminary results of the hollow-charge
calculations, a series of tests was conducted by WES to deter-
mine the validity of the calculations. Overpressure gage
recordings were made at several radii. Only one recording inthe skip zone was made because gages were not available to
record the high pressures in this region. Three gages were
damaged or lost in attempts to make high-pressure measurements.
A complete set of recordings was sent to S3 for comparison and
evaluation5.
Charge Design and Experimental Procedure
54. The test series consisted of a total of six events.
Two of the events were solid-charge control shots consisting
of line charges at a density of 5.74 kg/m. Two events were
hollow line-charges consisting of a 3-inch pipe inside a 4-inchpipe with explosive in the space between the pipes. The charge
density was 2.57 kg/m. Two events used a 2-inch inside a
4-inch pipe and had a charge density of 6.6 kg/m.
55. Hollow-charge containers were constructed of commer-
cially available PVC pipe approximately 6 m in length. The
smaller pipe was centered inside the larger pipe and nitromethane
was poured into the space between the two pipes. Because of
difficulties in sustaining detonation in a hollow charge, acommercially available sensitizer was mixed with the nitromethaneI to ensure full detonation.
Experimental Results
56. Using experimental gage recordings, peak overpressure
I and overpressure impulse data were tabulated from two of thehollow-charge events and one of the solid-charge events (see
I: Appendix A). These events are referred to as LCI-II-l,
LCI-II-2, and LCI-II-5, respectively. Results of calculations
61
(Problems 5.0003, 5.0006, and 5.0008) are used for comparison
purposes. Because the yields of the experiments and calculations
were not the same, the data presented were scaled to the yield
of LCI-II-l and LCI-II-2 (2.57 kg/m). Square root scaling to
the charge density ratios was used. Experimental data from
LCI-II-l and LCI-II-2 were averaged and error bands were placed
on the data.
57. Figure 39 is a comparison of overpressure from
LCI-II-l and LCI-II-2 with Problems 5.0006 and 5.0008. The
experiments used a void fraction (ratio of center volume to
charge volume) of approximately 1.28. Problem 5.0006 had a
void fraction of one and Problem 5.0008 had a void fraction
of two. The calculational data falls near the data scatter
out to a radius of 2.5 m and shows excellent overall agreement
in peak pressures. At about 1.1 m, the pressure from Problem
5.0006 rises, marking the merging of the main and reflected
shocks. The merging occurs at 1.3 m in Problem 5.0008. The
experimental data between 1.1 and 1.4 m also shows a similar
rise. The rise in the experimental data occurs between thetwo calculations as would be expected from the volume ratios.
58. The merging of the second shock with the main shock
is an important parameter for these experiments. The secondshock has passed through the interior of the charge and has
been changed by the conditions existing in the skip zone. The
fact that the calculations agree with the radius of merging
and with the peak overpressure in this vicinity is a strong
indication that the blast parameters are properly treated bythe calculations in the range less than 1 m.
59. Impulse comparisons are given in Figure 40. Thesealso reveal excellent agreement between calculation and experi-
ment. The impulse minimum is not shown by the experiments
because gage recordings were only made as close as 0.81 m.The calculation is again within data scatter out Lo 3 m and
is slightly above the experimental data beyond 3 m.
62
10 I A I I " - I I I I I I I
SExperimental Data (V=!.28)
- A Problem 5.0006 (V=l)
0 Problem 5.0008 (V=2)
- O A•
,) Iin 1.0
ý44
I A
I.I
L. q
0.1 1 I I I I I I 10.3 1.0 10
i.i Range (m)
FIGURE 39. Overpressure versus Radius, Hollow Charges
63
I3 0
I 4444
0f04 000 0 0
o 0D o
0 00
,I *:2'4
I 64
I
60. Data from LCI-II-5 is compared to Problem 5.0003 in
Figure 40 and to earlier solid charge experiments (LCI-II-6,ILCI-2, and LCI-3) and Problem 5.0003 in Figure 41. Figure 41
shows agreement of experimental solid charge overpressuresI and calculations. Impulse comparisons in Figure 40 reveal
remarkable similarities with calculational impulse data.
Experimental hollow charge data lie above the solid charge
data inside 1 m, implying impulse enhancement in this region.
61. The question arises as to whether the experimental
solid charge data inside 1 m is reliable. This can be shown
by a comparison with impulse data from Problem 5.0003 in
Figure 40. Because calculational and experimental solid charge
data are in excellent agreement, one may conclude that the
experimental data points are valid.
62. In ref'ýrence to the comparisons, several important
points can be made:
a. Hollow-charge data from experiment and calcula-
tion are in good overall agreement.
b. Hollow-charge characteristics predicted by the
calculations are evident in experimental data.
c. Solid-charge experimental and calculational
data show excellent agreement.d. Overpressure impulse enhancement in the skip
zone for hollow charges is seen in experimental data as predicted
lI by the calculations.
63. As reported in Reference 5, an effort is underway to
I determine if the achieved enhancement is sufficient to reliablyactivate the M16 AT mine.
II
ii i|L 65
10 r -rF
\ --...--Problem 5.0003L -(Solid Cal.)
A tLCI-II-5&. LCI-II-6
- , LCI-20 LCI-3
"4 "0
A
0\A
ci -_ _ _ _ __ _ _ _ \ .-S1.0
U,04
_ A
* \00
00
U1.0 10
FIGURE 41. Overpressure versus Radius, Solid Charges
66
References
1. Ingram,, J. K.,, "Airbiast and Impulse Produced byM58 Al and British Giant Viper Linear ExplosiveCharges - Phase 2 Experiments", Preliminary Report,November 1979, U.S. Army Engineer WaterwaysExperiment Station, Vicksburg, Mississippi.
2. Whitaker, W. A., et.ai., "Theoretical Calculationsof the Phenomenology of HE Detonations", AFWL-TR-66-141, Volume I, November 1966, Air Force WeaponsLaboratory, Research and Technology Division,Kirtland Air Force Base, New Mexico.
3. Ree, Francis H., "Equation of State of Plastics:Polystyrene and its Foams", UCRL-51885, August 1975,Lawrence Livermore Laboratory, University ofCalifornia, Livermore, California 94550.
4. Mader, C. L., Carter, W. J., "An Equation of Statefor Shocked Polyurethane Foam", LA-4059, Ur 34,Physics, TID-4500, Written: November 1968Distributed: February 1969, Los Alamos ScientificLaboratory of the University of California,Los Alamos, New Mexico.
5. Ford, M. B., "Line-Charge Improvement Tests", WEESE,Unpublished Working Draft, July 1981, U.S. ArmyEngineer Waterways Experiment Station, Vicksburg,Mississippi.
68
IE
APPENDIX A
Tabulated Data from Gage Records
1. EVENT LCT-II-I
Radius Overpressure Overpressure Impulse(m) (MPa) (kPa-sec)
0.81 10+ 0.41
1.1 2.15 0.475
1.36 4.3 0.48
1.61 1.45 0.43
1.86 0.70 0.51
2.11 1.6 0.18
2.61 0.25 0.415
3.11 0.375 0.4
3.61 0.25 0.39
5.5 0.3
2. EVENT LCI-II-,2
Radius Overpressure Overpressure Impulse(m) (MPa) (kPa-sec)
0.81 2+ 0.38
1.1 2.4 0.44
1.36 3.4 0.515
1.61 1.9 0.69
1.86 0.85 0.56
2.11 1.5 0.59
2.61 1.4 0.255
3.11 0.4 0.41
3.61 0.45 0.4
69
69 ..
ii
i Tabulated Data from Gage Records (Continued)
3. EVENT LCI-II-5 (Scaled to a charge density of 2.57 kg/m)
Radius Overpressure Overpressure Impulse(in) (MPa) (kPa-sec)
(scaled) (scaled)
0.54 7.0 0.228
0.74 5.65 0.265
1.07 4.62 0.44
1.24 2.4 0.479
1.74 1.4 0.53
2.18 1.15 0.67
2.45 1.05 0.585
3.15 0.65 0.425
3.71 0.54 0.33
I,,
I7Il,
