Experimental determination of the velocity field for behind-the- armor debris (BAD)

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Experimental determination of the velocity field for behind-the- armor debris (BAD)
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Table of Contents
    Title Page
        Page i
        Page ii
    Acknowledgement
        Page iii
    Table of Contents
        Page iv
        Page v
    List of Tables
        Page vi
        Page vii
    List of Figures
        Page viii
        Page ix
        Page x
        Page xi
        Page xii
        Page xiii
        Page xiv
    Abstract
        Page xv
        Page xvi
    Chapter 1. Introduction
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
    Chapter 2. Hardware description
        Page 10
        Page 11
        Page 12
    Chapter 3. Test conduct and data reduction procedures
        Page 13
        Page 14
        Page 15
        Page 16
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    Chapter 4. Data evaluation
        Page 40
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    Chapter 5. Eulerian finite element model study
        Page 87
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    Chapter 6. Hydrocode theory
        Page 161
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        Page 163
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    Chapter 7. Summary, conclusions, and recommendations
        Page 179
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        Page 184
        Page 185
    References
        Page 186
        Page 187
        Page 188
    Biographical sketch
        Page 189
        Page 190
        Page 191
Full Text










EXPERIMENTAL DETERMINATION OF THE
VELOCITY FIELD FOR BEHIND-THE-ARMOR DEBRIS (BAD)












BY

WILLIAM WINFIELD DYESS, JR.


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY



UNIVERSITY OF FLORIDA


1994






























Copyright 1994

by

William Winfield Dyess, Jr.













ACKNOWLEDGMENTS


I wish to thank my committee for their support and advice during this

educational process. In particular, I thank Dr. C. Allen Ross for his advice,

support, and encouragement. Without him this effort would not have been

possible. I would like to thank Mr. Danny A. Brubaker for his help in the

computation portion of this study. Without his effort, this portion could not have

been completed. I would also like to thank my wife, Mildred, for her patience,

support, and understanding throughout this effort. I would like to acknowledge the

financial support of the Air Force Development Test Center at Eglin Air Force

Base, Florida, and the personal support and encouragement of Dr. Dan Stewart,

Mr. Ron Jacob, and Mr. Herb Brown. Finally, I wish to acknowledge the efforts of

Mr. Steve Brown, Ms. Emily Farver, Mr. John Cleary, and Ms. Deborah Godwin for

their support in the editing and layout of this dissertation.














TABLE OF CONTENTS

paae

ACKNOW LEDGMENTS ........................................ iii

ABSTRACT ................................................. xv

CHAPTERS


1 INTRODUCTION ..........


. . . . . . . . . . . . . . . 1


O bjective ..................
Background ................
Approach ..................

2 HARDWARE DESCRIPTION ....

G eneral ...................
Penetrator ..................
Targets ....................


3 TEST CONDUCT AND DATA REDUCTION PROCEDURES

G eneral ........ ............ ......... ... ......
Crater Characterization ...........................
Basic BAD Characterization .......................
Enhanced BAD Velocity Characterization ..............

4 DATA EVALUATION .............................


.. 13


G eneral .........................
Crater Characterization ..............
Basic BAD Characterization ...........
G eneral .......................
Target Plate Data ................
Spall Panel Data .................
Spall Mass Data .................
Spall Cap Velocity Data ............
Enhanced BAD Velocity Characterization .
Method 1: Make Screen Method .....
Method 2: Radiographic Method.....
Chapter Summary ..................


...... 40
...... 49
...... 50
...... 50
...... 51
...... 53
...... 54
...... 57
...... 77
...... 77
...... 77
...... 86








5 EULERIAN FINITE ELEMENT MODEL STUDY ....


G eneral .. . .. ... ... ... .. . .. ... .. . .. ... ... ... ...
Validation of Code Inputs .................................
G eneral .... .... ......... ... ...... ...... ...........
Semi-infinite Armor Characterization .......................
Finite Armor Characterization ............................
Comparison of Model Results to Test Results ..................
G eneral ................ ... ... ... ... ..............
Study of 2.50-Inch (0.0635 Meter) Target Impact
(Fracture Strength = -1.30 GPa) .......................
Study of 2.50-Inch (0.0635 Meter) Target Impact
(Fracture Strength = -0.85 GPa) .......................
Study of 2.00-Inch (0.0508 Meter) Target Impact
(Fracture Strength = -0.85 GPa) .......................
Study of 0.75-Inch (0.01905 Meter) Target Impact
(Fracture Strength = -0.85 GPa) .......................
Study of 2.50-Inch (0.0635 Meter) Target Impact


(Fracture Strength =
Chapter Summary ......

6 HYDROCODE THEORY .


-0.50 GPa)


87

87
88
88
88
100
110
110

110

126

135

145


... .. . .. ... .. 152
............... 160


Background .............
Governing Equations .......
Introduction ............
Conservation Equations ...
Constitutive Relations ....
Equations of State .......
Failure Criteria .........
Discussion of Equations .....
Spatial Discretization .......
Time Integration ..........
Artificial Viscosity .........
Chapter Summary .........


7 SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS ........

REFERENC ES ..............................................

BIOGRAPHICAL SKETCH ......................................


161
162
162
163
164
168
171
174
175
176
177
177

179

186

189














LIST OF TABLES


Table paqe

1 Classification of the Behavior of the Penetrator as a Function of Velocity
in Terms of the Relative Strengths of Target and Penetrator ...... 7

2 Definition of Various Metallic Components of the Armor ........... 12

3 Test Condition for the Complete Test Series Target Definition ...... 41

4 Test Condition for the Complete Test Series Impact Data ......... 42

5 Test Condition for the Complete Test Series Evaluation Summary ... 43

6 Results of the Crater Test Series ............................ 44

7 Results of the BAD Test Series Target Plate, Spall Bundle, and
Spall Cap Velocity Data ................................ 45

8 Results of the Complete BAD Test Series Spall Mass Data ........ 46

9 Velocity Field Data from Test CLG0982 ....................... 47

10 Velocity Field Data from Test CLG0955 ....................... 47

11 Velocity Field Data from Test CLG0953 ....................... 48

12 Velocity Field Data from Test CLG0956 ....................... 48

13 Parameter Definition for the Various Cases Evaluated with CTH
for the Crater Characterization ........................... 92

14 CTH Results Compared to Test CLG0854 ..................... 92

15 CTH Results Compared to Test CLG0853 ..................... 93

16 CTH Results Compared to Test CLG0855 ..................... 93

17 CTH Results Compared to Test CLG0856 ..................... 94

18 Finite Target Comparative Data ............................ 108








19 Tracer Particle Velocity, Component Velocities, and Direction Angle
at 500 Microseconds from Computation of Test CLG0982
(Fracture Strength = -1.30 GPa) ......................... 116

20 Tracer Particle Velocity, Component Velocities, and Direction Angle
at 200 Microseconds from Computation of Test CLG0982
(Fracture Strength = -0.85 GPa) ......................... 127

21 Tracer Particle Velocity, Component Velocities, and Direction Angle
at 200 Microseconds from Computation of Test CLG0875
(Fracture Strength = -0.85 GPa) ......................... 136

22 Tracer Particle Velocity, Component Velocities, and Direction Angle
at 200 Microseconds from Computation of Test CLGO951
(Fracture Strength = -0.85 GPa) ......................... 146

23 Tracer Particle Velocity, Component Velocities, and Direction Angle
at 200 Microseconds from Computation of Test CLG0982
(Fracture Strength = -0.50 GPa) ......................... 153














LIST OF FIGURES


Fi-gure

1

2

3

4

5

6

7

8

9

10


11

12


13

14

15


16 Design of the Spall Box Used for BAD Testing Side View ......

17 Design of the Spall Box Used for BAD Testing Front View ......

18 Front of One of the Quarter Steradian Zone Switch Screen Designs


Velocity Distribution .....................................

Cross Sections of Spall Bubble Concepts .....................

Event Ranges .........................................

Schematic Drawing of the Penetrator .........................

Test Area C-64 .........................................

Schematic of Test Area C-64 Setup ..........................

Typical Preimpact Radiographs .............................

Preimpact Radiographic Setup ..............................

Radiographic Setup for the BAD Debris Radiographs .............

Technique Used to Define the Crater Characterization
Data for Inclusion into the Database .......................

Primary Hole Measurements Taken for Inclusion into the Database ...

Spall Ring Measurements Taken from the Sectioned
Target for Inclusion into the Database ......................

Spall W itness Bundle Definition .............................

Typical Data Taken from the Spall Panels ......................

Positioning of the Spall Bundle in a Spall Box ...................


)age

.4

.5

.6

11

* 17

18

19

20

21


22

23


24

25

26

27

28

29

33









19 Side View of the Three-Array Form of the Quarter
Steradian Zone Switch Screen Design ......................

20 Schematic of the Process of Sectioning the Spall Cone ............

21 Schematic of the Enhanced Velocity Test Setup Side View ........

22 Schematic of the Enhanced Velocity Test Setup Sectioned View ....

23 Data Collection Area .....................................

24 Spall Cone Geometry versus Test Parameters ..................

25 Comparison of the Actual Craters Created by the Penetrator ........

26 Database Data from the Crater Tests .........................

27 Penetration versus Velocity ................................

28 Calculated Crater Volume versus Kinetic Energy .................

29 Limit Thickness versus Velocity .............................

30 Average Profile Hole Diameter as a Function of the Target
Areal Density ........................................

31 Average Spall Ring Depth as a Function of the Target
Areal Density ........................................

32 Average Spall Ring Diameter as a Function of the Target
Areal Density ........................................

33 Sectioned Views 2.0-Inch (0.0508 Meter) Targets ...............

34 Sectioned Views 2.5-Inch (0.0635 Meter) Targets ...............

35 Rear View 3-Inch (0.0762 Meter) Targets .....................

36 Sectioned View of Selected BAD Targets ......................

37 Sectioned View 3.5-Inch (0.0889 Meter) Target .................

38 Computer Generated Plot of the Perforations of the First Spall
Witness Panel for Selected BAD Tests .....................

39 Number of Holes in Panel 1 of the Spall Bundle as a Function
of the Target Density ..................................


34

35

36

37

38

39

59

60

61

62

62








40 Number of Holes in Panel 2 of the Spall Bundle
as a Function of the Target Areal Density ................... 71
41 Spall Half-Cone Angle as Measured on Panel 1 of the
Spall Bundle as a Function of the Target Areal Density ......... 72

42 Total Spall Mass as a Function of the Target Areal Density ......... 72

43 Number of Fragments Whose Mass are Greater Than
One Gram as a Function of the Target Areal Density ........... 73

44 Total Nonferrous Spall Mass as a Function of the Target Areal
D ensity ............................................ 73

45 Total Ferrous Spall Mass as a Function of the Target Areal Density ... 74

46 Percent of Dust as a Function of the Target Areal Density .......... 74

47 Mass Distribution Plot .................................... 75

48 Spal Cap Velocity Expressed as a Percent of the Impact
Velocity as a Function of Target Areal Density ................ 76

49 Typical Traces from the Make Screens ........................ 80

50 Standard Overhead Radiographic View behind a 0.75-Inch
(0.01905 Meter) Target ................................. 81

51 Standard Side Radiographic View behind a 0.75-Inch
(0.01905 Meter) Target ................................. 81

52 New Side Radiographic View behind a 0.75-Inch
(0.01905 Meter) Target ................................. 82

53 Standard Overhead Radiographic View behind a 2.5-Inch
(0.0635 Meter) Target .................................. 83

54 Standard Side Radiographic View behind a 2.5-Inch
(0.0635 Meter) Target .................................. 83

55 New Side Radiographic View behind a 2.5-Inch
(0.0635 Meter) Target .................................. 84

56 Fragment Velocity Test Data Compared to Single Bubble Predictions .. 85

57 Fragment Spatial Test Data Compared to Single Bubble Preditions ... 85

58 CTH Grid Pattern for Semi-infinite Armor Study .................. 91








59 Volum e Study .......................................... 95

60 Penetration Depth Study .................................. 96

61 Comparison of the Crater Shape of CLG0853 to Those Predicted
by Cases 1, 3, and 5 .................................. 97

62 Comparison of the Crater Shape of CLG0853 to Those Predicted
by Cases 2, 3, and 4 .................................. 98

63 Comparison of the Crater Shape of CLG0854 to Those Predicted
by Cases 1 and 3 .................................... 102

64 Comparison of the Crater Shape of CLG0855 to Those Predicted
by Cases 1 and 3 .................................... 103

65 Comparison of the Crater Shape of CLG0856 to Those Predicted
by Cases 1 and 3 .................................... 104

66 Predicted Crater Using Case 4 and CLG0853 Models and Values
in a 3-D Evaluation ................................... 105

67 Range of BHN Encountered as a Function of RHA Thickness ...... 106

68 Ultimate Tensile Strength versus BHN for Steel ................. 107

69 CTH Grid Pattern for Finite Armor Study ...................... 108

70 Comparison of Measured versus Computed Spall Cap Velocity ..... 109

71 CTH Grid Used for the Simulation of Test CLG0982
(2.50-Inch [0.0635 Meter] Target) ........................ 113

72 Tracer Particle Pattern for Simulation of Test CLG0982 ........... 114

73 Computed Velocity Plot for Tracer 17 of CLG0982 .............. 115

74 Computed Velocity Plot for Tracer 29 of CLG0982 .............. 115

75 Calculated Velocity Vector Field for CLG0982 at Time =
0 Microsecond (Fracture Strength = -1.30 GPa) .............. 117

76 Calculated Velocity Vector Field for CLG0982 at Time =
23 Microseconds (Fracture Strength = -1.30 GPa) ............ 118

77 Calculated Velocity Vector Field for CLG0982 at Time =
53 Microseconds (Fracture Strength = -1.30 GPa) ............ 119









78 Calculated Velocity Vector Field for CLG0982 at Time =
83 Microseconds (Fracture Strength = -1.30 GPa) ............

79 Calculated Velocity Vector Field for CLG0982 at Time =
100 Microseconds (Fracture Strength = -1.30 GPa) ...........

80 Calculated Velocity Vector Field for CLG0982 at Time =
200 Microseconds (Fracture Strength = -1.30 GPa) ...........

81 Calculated Velocity Vector Field for CLG0982 at Time =
500 Microseconds (Fracture Strength = -1.30 GPa) ...........

82 Calculated Velocity Vector Field for CLG0982 at Time =
1,000 Microseconds (Fracture Strength = -1.30 GPa) ..........

83 Calculated Spall Cap Area for CLG0982 at Time =
1,000 Microseconds Enlarged (Fracture Strength = -1.30 GPa)

84 Calculated Velocity Vector Field for CLG0982 at Time =
23 Microseconds (Fracture Strength = -0.85 GPa) ............

85 Calculated Velocity Vector Field for CLG0982 at Time =
53 Microseconds (Fracture Strength = -0.85 GPa) ............

86 Calculated Velocity Vector Field for CLG0982 at Time =
83 Microseconds (Fracture Strength = -0.85 GPa) ............

87 Calculated Velocity Vector Field for CLG0982 at Time =
100 Microseconds (Fracture Strength = -0.85 GPa) ...........

88 Calculated Velocity Vector Field for CLG0982 at Time =
200 Microseconds (Fracture Strength = -0.85 GPa) ...........

89 Calculated Velocity Vector Field for CLG0982 at Time =
500 Microseconds (Fracture Strength = -0.85 GPa) ...........
90 Calculated Material Interface Plots for CLG0982
(Fracture Strength = -0.85 GPa) .........................

91 Tracer Particle Pattern for Simulation of Test CLG0875 ...........

92 Calculated Velocity Vector Field for CLG0875 at Time =
25 Microseconds (Fracture Strength = -0.85 GPa) ............

93 Calculated Velocity Vector Field for CLG0875 at Time =
50 Microseconds (Fracture Strength = -0.85 GPa) ............


94 Calculated Velocity Vector Field for CLG0875 at Time =


75 Microseconds (Fracture Strength = -0.85 GPa) ............

xii


120


121


122


123


124


125


128


129


130


131


132


133


134

137


138


139


140








95 Calculated Velocity Vector Field for CLG0875 at Time =
150 Microseconds (Fracture Strength = -0.85 GPa) ........... 141

96 Calculated Velocity Vector Field for CLG0875 at Time =
200 Microseconds (Fracture Strength = -0.85 GPa) ........... 142

97 Calculated Velocity Vector Field for CLG0875 at Time =
400 Microseconds (Fracture Strength = -0.85 GPa) ........... 143
98 Calculated Material Interface Plots for CLG0875
(Fracture Strength = -0.85 GPa) ......................... 144

99 Tracer Particle Pattern for Simulation of Test CLG0951 ........... 147

100 Calculated Velocity Vector Field for CLG0951 at Time =
25 Microseconds (Fracture Strength = -0.85 GPa) ............ 148

101 Calculated Velocity Vector Field for CLGO951 at Time =
50 Microseconds (Fracture Strength = -0.85 GPa) ............ 149

102 Calculated Velocity Vector Field for CLG0951 at Time =
75 Microseconds (Fracture Strength = -0.85 GPa) ............ 150

103 Calculated Densityfelocity Vector Field for Late Times for
CLGO951 (Fracture Strength = -0.85 GPa) .................. 151

104 Calculated Velocity Vector Field for CLG0982 at Time =
25 Microseconds (Fracture Strength = -0.50 GPa) ............ 154

105 Calculated Velocity Vector Field for CLG0982 at Time =
75 Microseconds (Fracture Strength = -0.50 GPa) ............ 155

106 Calculated Velocity Vector Field for CLG0982 at Time =
100 Microseconds (Fracture Strength = -0.50 GPa) ........... 156

107 Calculated Velocity Vector Field for CLG0982 at Time =
200 Microseconds (Fracture Strength = -0.50 GPa) ........... 157

108 Calculated Velocity Vector Field for CLG0982 at Time =
500 Microseconds (Fracture Strength = -0.50 GPa) ........... 158

109 Calculated Material Interface Plots for CLG0982
(Fracture Strength = -0.50 GPa) ......................... 159

110 Comparison of the Calculated Values for BAD Velocity and
Those Determined from Actual Tests 0.75-Inch
(0.01905 Meter) Target ................................ 181








111 Comparison of the Calculated Values for BAD Velocity and
Those Determined from Actual Tests 2.00-Inch
(0.0508 Meter) Target ................................. 181

112 Comparison of the Calculated Values for BAD Velocity and
Those Determined from Actual Tests 2.50-Inch
(0.0635 Meter) Target ................................. 182

113 Tracer Point Velocities as a Function of Origin for 2.50-Inch
(0.0635 Meter) Target Impact (Fracture Strength = -0.85 GPa) ... 185

114 Tracer Point Velocities as a Function of Origin for 2.50-Inch
(0.0635 Meter) Target Impact (Fracture Strength = -0.50 GPa) ... 185














Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the Requirements
for the Degree of Doctor of Philosophy

EXPERIMENTAL DETERMINATION OF THE
VELOCITY FIELD FOR BEHIND-THE-ARMOR DEBRIS (BAD)

By

WILLIAM WINFIELD DYESS, JR.


December 1994


Chairman: C. Allen Ross
Major Department: Aerospace Engineering, Mechanics and Engineering Science


Impacts of deforming/eroding projectiles on metallic armors generate a highly

energetic debris field behind the armor during the perforation process. In the

community involved with this event, the debris field is referred to as the behind-the-

armor debris (BAD) field. The study of BAD and its effects, as defined in this

dissertation, was started in 1959. Since that time, various empirical models have

been developed which strive to predict the field. Only recently have the

capabilities of the hydrocodes been added.

The BAD field is generally studied as several components: fragment spatial

distribution, fragment mass distribution, and fragment velocity distribution. This

dissertation addresses one of the basic issues of the last component. Prior to this

work, there were two theories in the community. The first was that the fragments

in the BAD field were on the outer edge of the expanding BAD field (single bubble








theory). This resulted in a single parabolic distribution of the velocity field about

the line of impact. The shape of the parabola was then adjusted to provide an

overall energy match. The second theory was that the fragments in the BAD field

were distributed over a series of expanding fronts (multiple bubble theory).

This study proves conclusively that the single bubble theory is invalid. High

fidelity data is presented which refutes the concept, and a test technique was

developed and is presented which can be used to acquire further high fidelity data

for continued studies. In addition, an advanced test technique is discussed which

would allow, with some developmental effort, the ability to collect high fidelity data

as a part of the standard BAD field characterization, thus reducing the cost of

obtaining the data.

This dissertation also contains a study of the ability of a commercial

hydrocode to duplicate the results of the tests. The results were encouraging, and

areas where further work is needed were identified. The dominant data input for

matching the resulting BAD field to that determined from the test was found to be

the fracture strength. Further work in characterizing this parameter in the high

strain rate environment needs to be accomplished.













CHAPTER 1
INTRODUCTION


Objective

The primary goal of the proposed investigation was to obtain an improved

understanding of the velocity in the behind-the-armor debris (BAD) field resulting

from projectile impact. To accomplish this, a new test technique was developed to

obtain the required velocity data. A correlation between the resulting test data and

the results from a commercially available hydrocode was sought. It was not the

intent of this study to remodel the complete penetration process, but considerable

review of this area was necessary in order to understand the latter stages of this

event which formed the basis of the fragmentation process. Comparison will

involve fragment size, fragment velocity, and fragment size distribution.


Background

BAD, as used in this dissertation, is defined as the debris behind the target

plate, or armor, which was composed of fractured target and projectile material.

For this study, this BAD was generated by the penetration/perforations of a target

plate by a deforming/eroding projectile. This BAD should not be confused with the

debris associated with penetration/perforation of a rigid projectile which may result

in scabbing, plugging, or petaling. In general, this latter event was reasonably

understood and modeled.








The history of BAD modeling is fairly recent. In 1959, a test series known as

the Canadian Armament Research and Development Establishment (CARDE)

trials [1] was conducted. This was the beginning of the modern understanding of

BAD effects. This test series evaluated the damage done to "modern" tanks by

"modern" shape charge warheads. Using this data, Nail, Jackson, Beardon [2] and

others developed the first models, using a consistent data set, for predicting the

loss of combat utility for tanks. These models were expanded to include all ground

mobile targets. These early models were so-called "compartment" models. The

models related the probability of the loss of combat utility of a ground mobile target

to the size of the hole made by the shape charge jet. The model was referred to

as a "compartment" model because each compartment of the ground mobile target

(i.e., turret, engine area, crew compartment, etc.) was assigned a different loss of

combat utility requirement. The use of this type of simple model has continued

over the years because of its low cost and small data requirements. To keep the

technique current and usable, several changes have been made. The more

important were as follows: 1) a minimum residual penetration for both jets and

long rod penetrators was defined, which ensured ample residual energy accom-

panied the armor hole size to generate the required lethality; and 2) the definitions

of the "compartments" have been changed, and current damage data have been

added to augment the damage predictions.

In the 1980s, the concept of a point burst methodology was introduced. This

technique required a detailed geometric model of the target since the concept was

to model the spall field and predict the damage to the target components. The

most notable of the models were developed by Flint [3], Nail [4], and Ozolins [5].








Once the damaged components were determined, a criticality analysis was used to

determine the effect of the damage on the combat utility of the vehicle.

The development of the point burst methodology has been largely performed

by analysts, and statistical techniques have been used throughout. The method-

ology could be referred to as a statistical fit to empirical data with little physics or

continuum mechanics used. The point burst methodology has allowed major

improvements in the prediction of vehicle vulnerability. This ability was even better

when the actual warhead tests data were incorporated into the model. With one

notable exception, techniques have been developed which enabled a standardized

collection of data to determine the necessary BAD field parameters. The one

parameter which remained unresolved was the velocity of the fragments in the

BAD field.

The best velocity model was based entirely on the spall cap velocity. The

spall cap velocity was easily obtainable from radiographic coverage of the spall

field behind the armor. This spall cap velocity (sometimes referred to as the

residual penetrator velocity) was the maximum fragment velocity along the shot

line. The fragment velocities were modeled, by quarter steradian zones, using an

energy balance. The central zone was assigned the velocity of the spall cap, the

next zone was assigned a reduced velocity, etc. The velocity assignment was

based on a parabolic distribution. All fragments within each zone were assigned

the velocity of that zone, and a total energy was calculated for the spall field. If the

value of the energy of the spall field minus that of the impact event was other than

zero, the parabolic distribution was modified. This continued until an energy








balance was achieved. This process is further explained in Chapter 4. Figure 1

presents a schematic of this type of distribution.

















Figure 1. Velocity Distribution


No one in the field assumed this technique was exact, and everyone agreed

that it could be improved. However, at the time of this study, there was disagree-

ment about what form the improvement should take. The basic problem was that

there were two assumptions as to the composition of the BAD field. The first was

that all mass in the debris field was on the expanding spall bubble. The second

was that the expanding spall field was composed of several bubbles, each with its

own velocity field. These concepts are shown in Figure 2. Before any further

meaningful work could be done in this area, the true composition of the BAD field

needed to be resolved experimentally.
























a. Single Bubble


b. Multiple Bubbles
Figure 2. Cross Sections of Spall Bubble Concepts



The primary areas of current interest for the defeat of ground mobile targets

are in the high transition and hydrodynamic ranges which are characterized by

large numbers of energetic fragments resulting in a complex and highly lethal spall

field. These areas are defined in Figure 3 as Phases II and Ill. The line

appearing as a horizontal line and labeled the hydrodynamic limit is calculated

from Equation 1-1 below.










(1-1)


I Lpp


where:


is the penetration depth
is the length of penetrator
is the density of the penetrator material
is the density of the target material


Figure 3. Event Ranges


As an example, for a copper penetrator and a rolled homogeneous armor

(RHA) target, the hydrodynamic limit was 1.07 and occurred at a velocity of

approximately 2.3 to 2.5 kilometers per second (km/s).








Figure 3 could be calculated for any penetrator material versus target

material, and the shape of the curve would change depending on their properties.

The displayed shape is for materials which deform during the penetration process.

The events discussed in this report were contained in late event range I1. and early

event range Ill. It should be noted that in this region the transverse wave velocities

in the target were of the same order of magnitude as the penetration front velocity.

Woodward [6] presented this consideration in a different manner in Table 1. The

materials which will be discussed in this report fall within the first category of this

table, and the velocity regime is well within the last block. The yield strengths

discussed in Table 1 should be the dynamic yield strength of the materials at the

strains rates to be encountered in the event. For the higher strain rate regions

where values as high as 106 /s may be encountered, split Hopkinson bar data (order

104 Is) was generally used as the most applicable.


Table 1. Classification of the Behavior of the Penetrator as a Function of Velocity
in Terms of the Relative Strengths of Target and Penetrator

Relative Flow Stress
of Projectile Behavior with Increasing Velocity
and Target
yp < (Tyr Mushrooming Projectile enters target and deforms inside target
Projectile enters target,
T

inside target do not target
deform
Projectile enters Projectile elements Both
ayp > 3our target without outside target deform, but ro
deforming those within do not
Note: oyp Yield strength of penetrator
o Yield strength of target









In the late 1980s, modifications were made to the hydrocodes by Johnson,

Stryk, Holmquist, and Souka [7] and Grady [8] which enabled the codes to predict

the spall field parameters. Even though these codes predicted the spall fields,

they were too costly and time consuming to be used for vulnerability analyses.

Vulnerability analyses involved several thousand impact points of a munition on a

target to determine the overall probability of reduction of combat utility. Zukas and

Kimsey [9] presented data showing that a typical three-dimensional calculation of

one impact required 39 hours of Cray X-MP central processing unit (CPU) time.

Thus, it was unlikely that the vulnerability community would embrace the

hydrocodes as a tool of its trade.

Since the spall modeling part of the codes had never been incorporated in

actual spall prediction associated with vulnerability studies, their true ability to

predict results within the complex environment of a real-world engagement had not

been assessed. Alternately, the current techniques have been through exhaustive

evaluation in this manner.

What was needed was a better understanding of the event so that a standard

production test method could be developed, or a current one modified, to generate

the required fragment velocity data. Alternately, if the code capability could be

verified for this regime, then the codes could be used to generate the basic data

for the vulnerability models, thus reducing the overall cost of testing.


Approach

Step 1: A series of tests would be conducted involving the impact of a

copper rod on various thicknesses of RHA. These impacts would be concentrated

in the 1.5- to 2.3-km/s velocity range. This range was selected for the reasons as









follows: 1) the region was commonly encountered for projectiles of this size in

practical applications, and 2) the region involves the transition range between

dynamic strength dependence and hydrodynamic flow. Data would be gathered to

characterize the terminal effects of the penetrator. This characterization would

include the composition of the BAD field as a function of the armor thickness and

the impact velocity. Portions of the BAD field from selected tests would be

examined to determine the mass and velocity vector of the individual fragments.

The details of this step are discussed in Chapters 2 through 4.

Step 2: A series of simulations of the tests conducted in Step 1 would be

generated using a commercially available hydrocode. The purpose of this portion

of the study was to investigate the BAD phase of the event. The grid size and

constitutive model inputs would be adjusted until the penetration/perforation

predictions of the code matched the parameters found in the characterization

performed in Step 1. The primary parameters which would be considered during

this process would be the semi-infinite penetration depth and the residual

penetrator velocity. After the adjustments were made, the code would be used to

investigate the agreement between the predicted BAD parameters and those found

in the tests of Step 1 for the failure criterion provided with the code. The details of

this step are discussed in Chapters 5 and 6.

Step 3: Conclusions would be drawn as to the merit of the hydrocode as

applied to this problem. A recommendation would be made as to the type of

standard test which could be employed to provide the necessary data in a

production environment. The details of this step are discussed in Chapter 7.














CHAPTER 2
HARDWARE DESCRIPTION


General

The hardware used in this series consisted of the penetrator and target as

well as the test diagnostic equipment which is fully covered in the work by Dyess

[10]. The diagnostic equipment will not be further discussed, except in general

terms. The penetrator and targets are discussed in the following paragraphs.


Penetrator

Figure 4 presents the schematic of the penetrator used in these tests. The

purpose of the aluminum drag cone was only to provide stability. Its effect on the

terminal effects of the penetrator should be minimal. The material of the penetrator

itself was annealed copper.


Targets

There was only one type of target examined under this effort which was

various thicknesses of RHA. The basic parameters of RHA are presented in

Table 2. The high hard armor data are presented for comparison as this was the

hardest metal used for general armor efforts, and the mild steel data are presented

for general comparison and also because they were used in the witness packages

(spall bundles).















































Figure 4. Schematic Drawing of the Penetrator






12


Table 2. Definition of Various Metallic Components of the Armor

Armor Military Brinell Thickness
Type Specification Hardness Number Range
(BHN) (in.)

High hard A-46100-3 418-555 0.25 1.50

RHA A-125606 269-418 0.25 6.00

Mild steel S-7952 100-156 0.06-0.13
Note: in. Inch = 0.0254 meter














CHAPTER 3
TEST CONDUCT AND DATA REDUCTION PROCEDURES


General

A complete review of how the basic tests were conducted and the data

reduced was written by Dyess [10]. In general, the tests were conducted on Test

Area C-64 (Figures 5 and 6) at Eglin Air Force Base (AFB), Florida. The pene-

trators were fired from the 125-millimeter (mm) smooth bore gun. In addition to the

basic tests discussed in the work by Dyess [10], special tests for determining the

BAD velocity vector fields were conducted. The test conduct and data reduction

procedures for these special tests will be discussed in detail later in this section.

Reduction of the basic data was accomplished in the usual format for crater

characterization and BAD characterization as discussed in the work by Dyess [10]

for explosively formed penetrators (EFP). Although not an EFP, this penetrator

was similar with regard to the terminal effects; thus, the test procedure and data

reduction procedure were basically the same. This included crater data, profile

hole diameter data, spall ring data, spall panel data, spall mass data, and spall cap

velocity data.

The preimpact data for these tests were mostly taken from radiographs.

Figure 7 presents a typical set of preimpact radiograph. The two radiographs were

taken in orthogonal planes. Not only could the velocity be calculated, but also the

preimpact angles and rotational rates were measurable. Figure 7 shows a sizable

preimpact pitch and almost no yaw. In order to insure that data reduction









confusion was minimized, a standard practice involving the numbering of the

radiographic plates was adopted. Odd-numbered plates were used for vertical

(overhead) views and even-numbered plates were used for horizontal (side) views.

A schematic of the preimpact radiographic setup is presented as Figure 8.

Figure 7 also demonstrates one of the strengths of this dual-source, orthogonal

system. Even if one of the sources were to fail (as it did in this case), the required

results would be obtainable. Occasionally, the radiographic data for the preimpact

portion of the experiment was not available. For these cases, the preimpact

velocity was obtained from a make screen. Make screens were composed of two

sheets of conducting material with a sheet of nonconducting material separating

them. When the projectile or other conducting material penetrated the screen, an

electrical circuit was made and the event was recorded. Two of these screens, at

a known distance apart, were used as a backup source of velocity data to the

radiographic instrumentation. Due to the reduced accuracy in the velocity data and

the inability to obtain orientation data, the make screen data was not the preferred

source.

A radiographic setup (Figure 9) similar to, but more extensive than, the

preimpact setup was used to collect data on the BAD field's overall shape and the

spall cap velocity. Again, a set of make screens were used as a backup source of

spall cap velocity data. Here the screen data can be even more misleading since

a small fragment in front of the spall cap can easily be what triggers the screen.

In order to understand the technique which was used to present the basic

data, the term "areal density" must be defined. Thickness and areal density were

related through a simple calculation. The areal density was computed by dividing








the mass of the base armor, or target, by the frontal area perpendicular to the

projectile flightpath. This calculation, throughout this report, resulted in units of

kilograms per square meter (kg/m2). The equivalent thickness, in inches, was

simply the areal density divided by 200 kg/m2 inches. This constant is the areal

density of 1 inch (0.0254 meter) of steel. This method of presenting the data was

common within the lethality/vulnerability community where the practice has been

found to be beneficial when dealing with complex targets.


Crater Characterization

The crater data were taken in accordance with the requirements of Dyess [10],

as shown in Figure 10. Notice that the data were taken every quarter inch

(0.00635 meter) into the armor from a section of the crater. This allowed for

calculations involving the volume of the crater as well as determining the exact

depth of penetration. Note that the bulge was also recorded. This information

was used in calculating the true "semi-infinite" depth of penetration. This is the

penetration which would occur in a homogeneous, continuous media of infinite

thickness.


Basic BAD Characterization

The BAD or spall data were collected in accordance with the requirements in

the report by Dyess [10]. In summary, this meant that hole data were taken in

accordance with the definitions given in Figures 11 and 12. The profile hole

diameter was the diameter of the smallest cross-section of the perforation. This

diameter was recorded both vertically and horizontally and the average of the two

values obtained. The spall panel data were taken using the spall bundle, as






16


defined in Figure 13. Figure 14 presents a processed spall panel with quarter

steradian zones drawn on the panel. Figure 15 reveals the placement of the spall

panel in the spall box behind the target. This arrangement can also be seen in

Figure 6. Figures 16 and 17 show the spall box used for these tests. This box

was used to completely contain all spall fragments.










































Figure 5. Test Area C-64


















-in. THICK
SPALL BOX


KeV 150 X-RAY
AFTER ARMOR





SPALL BOX OPENING
5 t 4 in. WIDE x 5 It 8 in. HIGH



KeV 150 X-RAY SYSTEM
PREIMPACT






VELOCITY SCREENS
X-RAY SWITCH


GUN SHOT TEST SETUP
U-4 8t I


P


RFLLILLLLAU


LATE SPALL WITNESS
BUNDLE
HEIGHT OF
SPALL BOX 911


SPALL BOX
ROTATES FROM 0- 700

0


I _E[. BACKSTOP
iB ,34GSPALL STRIPPER
TARGET

FOURTH STRIPPER














THIRD STRIPPER


SECOND STRIPPER


FIRST STRIPPER


NOTE: in. Inch = 0.0254 meter
ft Feet = 0.3048 meter

Figure 6. Schematic of Test Area C-64 Setup


. ... ... ..... I .. ..... ..... ..... ... ..

























a. Side View


b. Overhead View


Figure 7. Typical Preimpact Radiographs















TUBE HEAD 2 TUBE HEAD 1


TRIGGER
SCREEN
PLANE


SHOT LINE -


Figure 8. Preimpact Radiographic Setup


TUBE HEAD 4


TUBE HEAD 3















TUBE HEAD 7


TUBE HEAD 9


TUBE HEAD 10


Figure 9. Radiographic Setup for the BAD Debris Radiographs














BULGE DEPTH


PERPENDICULAR
REFERENCE LINE


NOTE: in. Inch = 0.0254 mee I

Figure 10. Technique Used to Define the Crater Characterization
Data for Inclusion into the Database











































Note: hi
ho
wi
wo


- Inside Height of Spall Ring
- Outside Height of Spall Ring
- Inside Width of Spall Ring
- Outside Width of Spall Ring


Figure 11. Primary Hole Measurements Taken for Inclusion into the Database





24







dill










... . ............. SPALL RING DEPTH







hIi


Note: hi Inside Height of Spall Ring
ho Outside Height of Spall Ring

Figure 12. Spall Ring Measurements Taken from the Sectioned
Target for Inclusion into the Database




















1/i1-in. MILD STEEL PANEL







DISTANCE IN INCHES


LENGTH AND WIDTH
ARE SUFFICIENT TO
/ e e e INSURE COVERAGE OF
SPALL CLOUD AREA




e. o /s.inMILD STEEL PANEL

''V 'V 1 STRFA
%% A 9 % e o
e' #e # # #



r,-,II7i1,tI
,ri~iI ,,, .- ." I 1I :
,I # #");G I #"1I7.I1
e ZONE,, 1
'%e 204,4 ,#


RHA
D14- 2


I


E) = SPALL CONE ANGLE
2


WITNESS PANEL ZONES
WITH SPALL CONE ANGLES
4 in. WITNESS PANEL NO. 1


O ANGLE IN DEGREES

162 -


NOTE: in. Inch = 0.0254 meters

Figure 13. Spall Witness Bundle Definition











NOTE: Cross Hairs is Aimpoint. Numbers on Upper Right are Shot Line Correction from Aim point.


Figure 14. Typical Data Taken from the Spall Panels












































Figure 15. Positioning of the Spall Bundle in a Spall Box




















SPALL PACKAGE
INSERTION OPENING


PROTECTION PLATE


SHOT UNE -


WINCH AND PULLEY SYSTEM
FOR TILTING SPALL BOX. ADJUSTS
TO ANY ANGLE THROUGH 60 DEGREES


SIDE VIEW
NOTE: in. Inch = 0.0254 meler

Figure 16. Design of the Spall Box Used for BAD Testing Side View


TOP VIEW














TOP VIEW SECTION


PLATE TO ISOLATE
FRONT AND BACK
SPALL AREAS


SPALL PACKAGE
POSITION








POSITION OF X-RAY
FILM CASSETTES


FRONT VIEW


Figure 17. Design of the Spall Box Used for BAD Testing Front View


I NOTE: in. Inch 0.0254 meter I








Enhanced BAD Velocity Characterization

The problem with obtaining the individual spall fragment velocities was the inability to

determine which fragment was which on a radiographic view. The fragments were

irregular, plate-like in shape, and usually tumbling. Thus, the shadows which they cast on

the radiographic plates generally were not the same when viewed from two points or at

two times. Add to this the complexity of some of the fragments approaching the radio-

graphic source and some approaching the radiographic film, and the problem became

insurmountable with current capabilities.

Two different methods were attempted during this effort. The first was to place from

16 to 32 make screens in two or three arrays between the back of the target and the front

of the witness bundle. The distance between the target and the witness bundle was only

2 feet (0.6096 meter) in the normal setup, a small area to use for this type of experiment.

Figures 18 and 19 show one of the several setups examined. For this particular attempt,

three make screen arrays at 6 inches (0.1524 meters) apart were used. The goal of this

method was to obtain the velocity of the spall fragments in quarter steradian zones

without affecting the gathering of the normal, required data. To match the generally used

data format, the make screens were made in the shape of quarter steradians and, in

some cases, further divided so that several distinct screens composed each quarter

steradian zone. Besides the setup already shown, an attempt was made to take data with

even smaller zones thus reducing the number of impacts per zone. Since the number of

recording channels was limited, this necessitated that only a quarter of the spall cone be

covered. That is, instead of the screens being over the entire surface of the witness

bundle, only a quarter of the witness bundle face was covered. A further attempt was

made by removing the witness bundle and placing the screens at a larger standoff from








the rear of the target. This allowed the BAD field to spread and enabled the screens to

be further separated. For typical make screen work, this technique will result in improved

accuracy. Additionally, this allowed for the first screen to be further removed from the

breakout point on the back side of the armor which reduced the impacts of small,

ineffective particles. For all of these techniques, the data were recorded with a Pacific

Model 5700 Portable Data Acquisition System with a sample rate of 500 kilohertz (kHz).

The second method involved the "slicing" of a portion of the spall cone. This

concept is shown in Figure 20. The schematic of the basic setup used is shown in

Figures 21 and 22. Specific experiment related values (such as spatial relationship

between the back of the target where the perforation was assumed to be going to occur

and the various radiographic sources and make screens) were recorded prior to each

experiment and adjusted based on the actual perforation point after each test. The high

density polyethylene was used as the surface of the front plate to suppress the number

and velocity of the BAD fragments which were eliminated from the continuing BAD field by

the plate. This was done to reduce the potential damage which these fragments could

cause in the test area. The portion of the polyethylene surface which normally incurred

the most damage was designed so that it could easily be replaced for each experiment.

Figure 23 presents the data collection area. This setup was different than the standard

BAD test setup. Therefore, in order to generate this data as a standard portion of BAD

data in a production environment, additional tests would be required. This would result in

additional costs which was seen as a distinct disadvantage. However, the hope was to

obtain enough data and understanding so that techniques similar to those previously

explained could be employed. This test method again employed the Pacific

instrumentation. However, the primary method of data collection was through








radiographic reduction. Since only a narrow band of the spall cone was allowed into the

zone where the radiographic data were collected, the data were much easier to reduce.

After reduction of the data to determine the velocity vector for each fragment of interest,

each fragment was traced back to the approximate point of origin. If this point was not

within, or nearly within, the exit hole of the penetrator through the target, the fragment

was determined to have been affected by the slicing of the spal field. This could have

happened, for example, by a deflection of the fragment due to an impact on the sides of

the opening in the first plate. In addition to the radiographic and make screen data, the

fragments were captured and weighed. Frequently the fragments directly on the shot line

were not captured because of the excessive kinetic energy of this zone. This could be

done in later tests as it has been done for other efforts.

One final point should be noted about these tests. The first method described would

generate all data required for the complete characterization of the BAD velocity field. The

second method would not. There were two primary reasons for this. First, the method

investigates only a slice of the BAD field, not the entire field. Thus, the results would

have to be manipulated to model the entire BAD velocity field. Second, due to geometric

constraints as shown in Figure 24, only a portion of the BAD field slice was analyzed.

This coverage could be improved for future tests. However, the second method was

designed for the specific purpose of observing the general makeup of the BAD field. Both

test methods may be required to completely characterize the BAD velocity field.





































Figure 18. Front of One of the Quarter Steradian
Zone Switch Screen Designs


















































Figure 19. Side View of the Three-Array Form of the Quarter
Steradian Zone Switch Screen Design














TOP VIEW


SPALL FIELD BARRIER
(FRONT PLATE)
USED TO SECTION BAD FIELD
-'-


TARGET


PROJECTILE
DIRECTION


MAXIMUM SPALL CONE ANGLE


SECTIONED SPALL CONE


SHOT LINE


Figure 20. Schematic of the Process of Sectioning the Spall Cone














































NOTE: Not to scale
in. Inch 0.0254 meter
POLY High density (1 gram per cubc centimeter) polyethylene


Figure 21. Schematic of the Enhanced Velocity Test Setup Side View












REPLACEABLE POLY


REPLACEABLE POLY
SECTION

V24.0in.] k > 24.0in.


,.- POLY


72.0 in.


72.0 in.
FRONT PLATE
(2.0-in.-THICK POLY/1.0-in.-THICK STEEL)


2.0 in.

36.0 in.


12.0 in.in
72.0 in.






L2. n.

IL -72.0 in.
BACK PLATE
(1.0-in.-THICK STEEL)


NOTE: Not to scale
in. Inch = 0.0254 meter
POLY High density (1 gram per cubic centimeter) polyethylene

Figure 22. Schematic of the Enhanced Velocity Test Setup Sectioned View


POLY,


K


36.0 in.


4.0 in.



j- 1.75 in.











































Figure 23. Data Collection Area

















MAXIMUM SPALL CONE ANGLE


- - -
- - -


Figure 24. Spall Cone Geometry versus Test Parameters


'I


--4














CHAPTER 4
DATA EVALUATION


General

In this dissertation, all of the collected and reduced data will be presented, and

then each set will be discussed in the appropriate subsection. Tables 3, 4, and 5

present the preimpact data for all tests. Table 6 presents the crater data for all

crater tests, and Tables 7 and 8 present the BAD data for all BAD tests. Tables 9,

10, 11, and 12 present reduced fragment velocity data for those tests which were of

sufficient quality for the reduction to be meaningful. The use of "ND" in the tables

denotes that no data were available for that entry. The use of "N" or "NA" denotes

that data were not applicable for this test.

The standard method for collecting data as outlined by Dyess [10] were

followed. This method results in data being acquired in the units with which the

data collectors were most knowledgeable. In the past, this was found to result in

much fewer inadvertent errors. However, as can be seen in the previously

presented tables, the resulting raw data was in mixed units. Mass data was

recorded in metric units whereas everything else was recorded in British units.

This trend was continued throughout this document to ensure that all reduced data

and analytical results could be compared directly to the raw data. In all cases,

either the metric equivalent or the appropriate multiplicative constant were provided

for consistency.






41


Table 3. Test Condition for the Complete Test Series Target Definition


Test Brinell Target Areal Test
Number Hardness Number Thickness Density Type
(BHN) (in.) (kg/m2)

CLGO852 255 12.00 2400 Crater
CLG0853 255 12.00 2400 Crater
CLG0854 267 12.00 2400 Crater
CLG0855 255 12.00 2400 Crater
CLG0856 255 12.00 2400 Crater
CLG0857 321 2.00 400 Spall and Make Screens
CLG0858 364 0.75 150 Spall and Make Screens
CLG0859 302 3.50 700 Spall and Make Screens
CLG0860 340 1.50 300 Spall and Make Screens
CLG0863 340 2.00 400 Spall and Make Screens
CLG0866 321 2.00 400 Spall and Make Screens
CLG0867 321 2.00 400 Spall and Make Screens
CLG0875 340 2.00 400 Spall and Make Screens
CLG0877 321 1.00 200 Spall and Make Screens
CLG0894 364 1.00 200 Make Screens
CLG0919 340 0.75 150 Make Screens
CLGO920 364 0.75 150 Make Screens
CLG0927 321 0.75 150 Make Screens
CLG0928 340 0.75 150 Make Screens
CLGO951 364 0.75 150 Spall Velocity
CLG0952 364 0.75 150 Spall Velocity
CLG0953 364 0.75 150 Spall Velocity
CLGO954 364 1.50 300 Spall Velocity
CLG0955 321 2.00 400 Spall Velocity
CLG0956 340 2.50 500 Spall Velocity
CLGO981 302 2.00 400 Spall Velocity
CLGO982 302 2.50 500 Spall Velocity
CLG0983 321 2.00 400 Spall Velocity
CLG0984 321 2.00 400 Spall Velocity
CLG1003 302 3.00 600 Spall
CLG1004 321 2.50 500 Spall
CLG1013 387 0.75 150 Spall
CLG1014 340 0.50 100 Spall
CLG1015 340 0.50 100 Spall
CLG 1016 302 2.50 500 Spall
CLG1017 340 0.50 100 Spall
CLG1018 302 3.00 600 Spall

Note: kg/m2 Kilogram per square meter
in. Inch = 0.0254 meter










Table 4. Test Condition for the Complete Test Series Impact Data


Test Penetrator Impact Pitch* Yawb Impactc
Number Mass Velocity Angle Angle Angle
(g) (ft/s) (deg) (deg) (deg)


CLG0852
CLGO853
CLG0854
CLG0855
CLG0856
CLG0857
CLG0858
CLG0859
CLG0860
CLG0863
CLG0866
CLG0867
CLGO875
CLG0877
CLG0894
CLGO919
CLGO920
CLG0927
CLG0928
CLGO951
CLG0952
CLGO953
CLG0954
CLGO955
CLGO956
CLGO981
CLG0982
CLG0983
CLG0984
CLG 1003
CLG 1004
CLG1013
CLG1014
CLG1015
CLG1016
CLG1017
CLG1018


501.4
501.7
501.2
501.1
500.7
501.8
499.8
500.4
501.4
500.3
501.4
500.0
499.6
501.4
499.4
500.9
500.3
500.0
500.6
500.0
501.1
500.0
500.0
500.0
500.0
501.1
503.5
503.4
503.0
503.7
502.7
503.3
502.5
503.5
503.5
503.8
501.9


6104
5976
5115
7034
8225
5906
6050
6168
6084
6424
6164
6164
6063
6160
6000
5814
5883
6093
6020
6138
6150
6244
6238
6213
6250
6313
6362
6188
6300
6163
6220
6120
6193
6024
6207
6107
6127


0.00
0.00
2.50
-1.00
0.00
-2.50
0.00
0.00
0.00
2.00
0.00
-1.50
0.00
ND
-3.50
0.00
2.50
1.00
0.00
0.00
1.00
-2.00
-1.50
-1.00
-1.00
-1.00
0.00
0.00
-1.50
0.00
-2.50
-1.00
0.50
ND
0.00
ND
0.00


0.00
0.00
0.00
0.00
0.00
0.00
-2.50
-1.00
0.00
-1.50
-1.50
-5.00
0.00
ND
-1.00
1.00
-1.50
-1.00
0.00
0.00
1.50
-2.50
-2.50
-3.00
-1.00
0.00
0.00
0.50
-2.00
0.00
-2.00
-1.50
0.00
ND
0.00
ND
-1.50


J._ _ _I. I I
Note: a Measured up (+) or down (-) from shot line
b Measured right (+) or left (-) from shot line
C Calculated from pitch and yaw angles

Impact Angle = arctan ftarnPitch Angle) + tan Yaw Angle)

ft/s Feet per second = 0.3048 meter per second
g Gram
ND No data available


0.00
0.00
2.50
1.00
0.00
2.50
2.50
1.00
0.00
2.50
1.50
5.22
0.00
ND
3.64
1.00
4.30
1.41
0.00
0.00
1.80
3.20
2.91
3.16
1.41
1.00
0.00
0.50
2.50
0.00
3.20
1.80
0.50
ND
0.00
ND
1.50






43


Table 5. Test Condition for the Complete Test Series Evaluation Summary


Test DATA
Numberr11T
Crater j Hole Panel Fragmentation j Velocity

CLG0852 G N N N N
CLG0853 G N N N N
CLG0854 G N N N N
CLG0855 G N N N N
CLG0856 G N N N N
CLG0857 N G G G G
CLG0858 N G G G G
CLG0859 N G G G G
CLG0860 N G G G G
CLG0863 N G G G G
CLG0866 N G G G B
CLG0867 N G G G G
CLG0875 N G G G G
CLG0877 N G G G G
CLG0894 N G N N G
CLGO919 N G N N G
CLGO920 N G N N N
CLGO927 N B N N N
CLGO928 N G N N N
CLGO951 N B N N G
CLG0952 N G N N G
CLG0953 N G N N G
CLGO954 N G N N G
CLG0955 N G N N G
CLG0956 N G N N G
CLGO981 N G N N G
CLG0982 N G N N G
CLG0983 N G N N G
CLGO984 N G N N G
CLG1003 N G G G G
CLG1004 N G G G G
CLG1013 N G G G G
CLG1014 N B G G G
CLG115 N B G G B
CLG1016 N G G G G
CLG1017 N B G G G
CLG1018 N G G G G

Note: B Bad
G -Good
N Not applicable







44


Table 6. Results of the Crater Test Series


Test Corrected Penetration
Number Depth Bulge Depth Depth X D
(in.) (in.) (in.) (in.) (in.) (in.)

CLG0853 2.48 0.20 2.28 0.00 0.30 3.84
0.25 0.37 3.66
0.50 0.46 3.52
0.75 0.53 3.36
1.00 0.62 3.20
1.25 0.75 2.96
1.50 0.86 2.82
1.75 1.00 2.46
2.00 1.29 2.00
2.25 1.56 1.26
2.50 2.12 0.12

CLG0854 1.78 0.20 1.58 0.00 0.90 3.22
0.25 0.80 3.18
0.50 0.86 3.10
0.75 1.02 2.86
1.00 1.15 2.64
1.25 1.30 2.36
1.50 1.62 1.62

CLG0855 2.96 0.18 2.78 0.00 0.96 3.76
0.25 1.04 3.58
0.50 1.08 3.48
0.75 1.15 3.32
1.00 1.20 3.30
1.25 1.18 3.40
1.50 1.16 3.34
1.75 1.12 3.26
2.00 1.36 2.88
2.25 1.50 2.62
2.50 1.74 2.12
2.75 2.12 1.36

CLG0856 3.80 0.20 3.60 0.00 0.85 3.90
0.25 0.94 3.90
0.50 0.99 3.76
0.75 1.01 3.72
1.00 0.96 3.76
1.25 0.96 3.82
1.50 0.92 3.92
1.75 1.00 3.66
2.00 1.10 3.50
2.25 1.16 3.12
2.50 1.32 2.84
2.75 1.52 2.44
3.00 1.66 2.12
3.25 1.94 1.84
3.50 1.16 1.36
3.75 3.02 0.20

Note: in. Inch = 0.0254 meter










Table 7. Results of the BAD Test Series Target Plate,
Spall Bundle, and Spall Cap Velocity Data


Hole Data Spall Bundle Data

Test Average Average Holes Cone Holes X-Ray
Number Spall Ring Spall Ring Average Panel Angle Panel Spall Cap
Diameter Depth PHD No. 1 Panel No. 2 Velocity
(in.) (in.) (in.) No. 1 (M s)

CLG0857 3.63 ND 2.63 46 31.34 27 2846
CLG0858 3.10 ND 2.38 128 48.78 56 5295
CLGO859 0.00 0.00 0.00 0 0.00 0 0
CLGO860 3.50 0.78 2.44 115 46.79 61 4229
CLG0863 3.88 0.31 2.53 74 41.70 40 3284
CLG0866 3.86 0.45 2.25 51 42.75 28 ND
CLG0867 4.03 0.34 2.64 74 37.20 38 3267
CLG0875 3.72 0.26 2.29 63 35.32 32 3254
CLG0877 3.18 0.28 2.13 144 40.93 78 5144
CLG0894 3.06 0.26 2.34 NA NA NA 5071
CLGO919 2.88 0.21 2.27 NA NA NA 5011
CLGO920 3.07 0.16 2.40 NA NA NA NA
CLG0927 2.98 0.24 2.43 NA NA NA NA
CLG0928 2.99 0.22 2.53 NA NA NA NA
CLGO951 ND ND 2.10 NA NA NA 5292
CLG0952 3.15 0.17 2.47 NA NA NA 5221
CLG0953 3.09 0.20 2.35 NA NA NA 5230
CLG0954 3.57 0.57 2.45 NA NA NA 4306
CLG0955 4.01 0.51 2.63 NA NA NA 3143
CLG0956 3.99 0.94 2.74 NA NA NA 2377
CLGO981 3.90 0.52 2.72 NA NA NA 3341
CLG0982 4.01 0.98 2.90 NA NA NA 2512
CLG0983 3.91 0.54 2.69 NA NA NA 3027
CLG0984 3.88 0.54 2.65 NA NA NA 3748
CLG1003 3.75 1.51 2.73 26 34.23 5 1400
CLG1004 4.37 0.92 2.64 ND ND ND 2307
CLG1013 3.19 0.15 2.31 142 48.32 64 5373
CLG1014 6.13 0.00 5.80 121 49.02 55 5533
CLG1015 ND ND ND ND ND ND ND
CLG1016 4.66 0.56 2.67 50 45.60 20 2700
CLG1017 7.10 0.07 6.60 100 44.45 45 5613
CLG1018 3.95 0.83 2.80 47 33.52 5 1029

Note: ft/s Feet per second = 0.3048 meter per second
in. Inch = 0.0254 meter
NA Not applicable
ND No data available










Table 8. Results of the Complete BAD Test Series Spall Mass Data


Ferrous Nonferrous Combined
Test Total Number
Number >1 gram Dust >1 gram Dust Spall Mass Fragments
(g) (g) (g) (g) (g) >1 gram

CLG0857 1126.06 65.93 181.55 29.88 1403.42 133
CLG0858 358.44 179.92 199.06 28.96 766.38 134
CLG0859 0.00 0.00 0.00 0.00 0.00 0
CLG0860 963.94 153.58 124.24 40.18 1281.93 183
CLG0863 1187.88 126.98 285.81 19.61 1620.28 119
CLG0866 963.20 120.87 149.74 28.68 1262.49 125
CLG0867 1155.24 142.57 130.27 33.44 1461.52 120
CLG0875 1161.89 58.16 179.89 28.32 1428.27 128
CLG0877 615.94 219.45 167.40 28.06 1030.85 169
CLG0894 ND ND ND ND ND ND
CLGO919 ND ND ND ND ND ND
CLG0920 ND ND ND ND ND ND
CLG0927 ND ND ND ND ND ND
CLG0928 ND ND ND ND ND ND
CLGO951 ND ND ND ND ND ND
CLG0952 ND ND ND ND ND ND
CLGO953 ND ND ND ND ND ND
CLG0954 ND ND ND ND ND ND
CLG0955 ND ND ND ND ND ND
CLG0956 ND ND ND ND ND ND
CLGO981 ND ND ND ND ND ND
CLG0982 ND ND ND ND ND ND
CLG0983 ND ND ND ND ND ND
CLG0984 ND ND ND ND ND ND
CLG1003 3160.53 38.91 106.58 11.57 3317.59 103
CLG1004 1961.35 53.06 231.55 43.00 2288.96 99
CLG1013 329.23 168.22 61.52 22.43 581.40 126
CLG1014 310.35 155.41 193.67 4.16 663.59 104
CLG1015 807.44 125.90 1.05 4.90 939.30 77
CLG1016 2192.43 67.59 265.82 16.79 2542.63 106
CLG1017 1392.70 183.26 50.39 7.71 1634.07 97
CLG1018 2380.32 41.86 195.90 25.68 2643.76 79

Note g Gram
ND No data available









Table 9. Velocity Field Data from Test CLG0982


Fragment Thetaa Velocityb Originc
Number (deg) (ft/s) (in.)

1 -3.08 3821 -0.04
2 5.54 2537 1.30
3 0.52 2579 1.46
4 0.22 2512 1.16
5 -3.55 2671 -0.33
6 -21.77 2238 1.31
7 4.15 2881 0.33
8 -0.24 3542 1.01
9 8.55 2793 3.83
10 -2.40 3391 0.52
11 1.11 3356 -0.95
12 22.86 2470 0.00
13 10.59 1989 1.47
14 3.33 2306 1.32
15 17.84 2307 -0.33
16 10.91 2291 0.94
Notes: a Measured up (+) or down (-) from shot line
b Measured along fragment path
Measured up (+) or down (-) from center of exit hole at rear surface of
target

ft/s Feet per second = 0.3048 meter per second
in. Inch = 0.0254 meter



Table 10. Velocity Field Data from Test CLG0955


Fragment Thetaa Velocityb Originc
Number (deg) (ft/s) (in.)

1 -10.09 3632 -0.21
2 19.09 3377 0.19
3 12.63 3503 1.37
4- 0.96 3768 -0.65

Notes: a Measured up (+) or down (-) from shot line
b Measured along fragment path
C Measured up (+) or down (-) from center of exit hole at rear surface of
target

ft/s Feet per second = 0.3048 meter per second
in. Inch = 0.0254 meter









Table 11. Velocity Field Data from Test CLG0953


Fragment Theta a Velocityb Originc
Number (deg) (ft/s) (in.)

1 -0.16 6290 0.13
2 9.00 6369 -5.99
3 2.90 6312 -0.00
4 2.53 6128 0.93
5 10.78 5038 1.48
6 14.55 4868 1.27
7 8.46 4453 1.75
8 3.14 5180 1.31
9 5.13 5979 -1.14
10 2.11 5791 0.11
11 -7.06 5212 -1.59
12 -7.66 5078 -0.48
13 -7.06 5463 1.02
14 -5.93 5944 1.94
15 -4.76 4874 -0.26
16 -4.06 6180 1.54

Notes: Measured up (+) or down (-) from shot line
b Measured along fragment path
C Measured up (+) or down (-) from center of exit hole at rear surface of
target

ft/s Feet per second = 0.3048 meter per second
in. Inch = 0.0254 meter


Table 12. Velocity Field Data from Test CLG0956


Fragment Thetaa Velocityb Originc
Number (deg) (ft/s) (in.)

1 -3.02 2980 -2.06
2 1.97 2769 0.39
3 -0.74 2377 0.32
4 -4.77 3017 0.34
5 7.15 3216 -4.31
6 -2.19 2663 0.24
7 -0.71 2857 0.02

Notes: a Measured up (+) or down (-) from shot line
b Measured along fragment path
C Measured up (+) or down (-) from center of exit hole at rear surface of
target

ft/s Feet per second = 0.3048 meter per second
in. Inch = 0.0254 meter








Crater Characterization

Figure 25 presents the photographs of the various penetrator-generated

craters at different impact velocities. All of the targets for the crater studies were

composed of two 6-inch (0.1524 meter) thick blocks of RHA. The purpose of these

tests was to determine the effect of velocity on the performance of the penetrator

so that estimates could be made as to the velocity effect on the BAD data. Figure

26 presents these same tests, but the recorded data were used. The primary point

to note was that the shapes of the craters were basically the same. Notice,

however, that each of the craters from the recorded data has a flat bottom,

whereas the actual craters do not. This variance resulted because the recorded

data plots stopped at the corrected depth (measured depth minus bulge). Thus,

the more deformed the armor, the more squared off the crater.

The crater comparison shows that the increased velocity has resulted in an

increase in the depth of penetration. This is in keeping with the increase in kinetic

energy on target. Figure 27 presents a plot of the penetration versus velocity. The

dotted line at the top of the plot is the hydrodynamic limit for this penetrator/target

condition as determined by the usual square root of the density ratio rule pre-

sented as Equation 1-1. Figure 28 presents a plot of the crater volume as calcu-

lated from the sectioned target versus the impact kinetic energy. The nearly

straight line was as predicted by the theories presented in A Short Course on

Penetration Mechanics by Wilbeck, et al. [11].








Using the empirical algorithm presented by Matuska [12] and refined for

copper EFPs by Dyess [13], the predicted value of the limit thickness (the

thickness which the penetrator will perforate 50 percent of the time) can be

determined. The algorithm is

= P + 0.4 D. (4-1)

where:

is the limit thickness
pc is the corrected penetration depth
D. is the steady state diameter of the crater

The predicted limit thicknesses determined were 2.68 inches (0.06807 meter)

at approximately 5,000 feet per second (ft/s) (1,524 meters per second [m/s]),

3.48 inches (0.08839 meter) at approximately 6,000 ft/s (1,829 m/s) impact

(nominal velocity for these tests), 4.10 inches (0.10414 meter) at approximately

7,000 ft/s (2,134 m/s) impact, and 4.99 inches (0.12675 meter) at approximately

8,000 ft/s (2,438 m/s) impact. A plot of these data is presented in Figure 29.


Basic BAD Characterization

General

The purpose of this subsection is to evaluate the effect of armor thickness on

the BAD generation of the penetrator under the selected nominal impact condition.

For this dissertation, the target areal density is used as the independent parameter

and is used for each of the major data displays. Nondimensional parameters were

not used for these presentations since Dyess [14] showed that results were highly

dependent on the high strain rate material properties of the penetrator and target








materials, and only limited success was achieved when comparing impacts on

RHA using copper and pure iron penetrators. To attempt to compensate for the

effects of the dynamic properties, the thickness data were nondimensionalized

using the limit thickness. This parameter was selected since it was itself a function

of these dynamic properties. As long as the penetrator and target materials were

not changed and the impact velocities were kept within the range of interest (1.5 to

2.3 km/s) the results were useful for predicative purposes. However, even with

these constraints, the predictions were only valid if the targets being considered

were from 20 to 80 percent of the penetrator's limit thickness. Attempts to use the

same predictions for different materials were less successful. For example, use of

the copper/RHA data to predict pure iron/RHA results were, at best, only of limited

use.

The basic concept of BAD data can be divided into four classes which are

target plate data, spall panel data, spall mass data, and spall cap velocity data.

These will be discussed in the subsequent sections.


Target Plate Data

Three primary parameters were examined in this section: the profile hole

diameter, the spall ring depth, and the spall ring diameter. These parameters were

previously defined in Figures 11 and 12. The plots of these three parameters are

shown in Figures 30, 31, and 32.

Historically, the thin armor effects were dependent on the tail cone diameter,

the medium armor effects were dependent on the confinement of these processes

and energy within the armor causing additional erosion and plastic flow, and the

final or near-limit thickness armor effects were dependent on the "plugging" of the








armor. This plugging occurred when the terminal energy of the penetrator was just

barely sufficient to cause perforation. When this occurred, a final hole, roughly the

size of the residual penetrator, was sheared through the remainder of the target.

Similarly, the spall ring was not formed in the thin armor. As the armor thick-

ness increased, the spall ring became wider and deeper. This growth continued

until very near the limit thickness, usually 90 percent or higher. At this point, the

spall cap spalled off as a solid piece or several large broken pieces, resulting in a

large, shallow, flat-bottomed ring. The final or plugging condition had no spall ring.

The presented plots of these data follow the above discussed trends. How-

ever, there was considerable scatter in the spall ring depth data. The reason for

this scatter can be seen in Figures 33, 34, and 35. Figure 33 presents section

photographs of three of the 2-inch (0.0508 meter) targets. In the first case, both

sides of the hole show clear formation of the spall ring. However, only one side

has completely broken free of the target. In the second case, neither side has

completely broken free of the target. The third case shows both sides broken free,

but the upper side has been partially closed by the adjacent ring. Figure 34 shows

two sections of 2.5-inch (0.0635 meter) targets. In the first case, the spall ring has

been formed, but little has broken free. Notice that the ring measured (broken

free) was only one of a possible three rings. The second case shows a larger ring

which was generated by two of the possible rings breaking free. Figure 35 shows

the rear of two of the 3-inch (0.0762 meter) targets. In the first case, a robust,

complete ring has been formed and ejected. In the second case, the ring has

been formed, but much of the material still remains. The above simply

demonstrates the normal variations encountered during testing. All of the targets








were RHA manufactured to the government specification for armor. In several

cases, the targets were from the same plate of RHA. However, in the spall ring

formation, the local surface condition, the local carbon content, etc., all may play a

major role. Naturally, due to the scatter encountered in this portion of the data

reduction, a similar scatter was anticipated in the mass data. Fortunately, only a

small fraction of the total BAD mass originated from the spall ring for this class of

impacts, so the scatter would be less dramatic. The formation of the spall ring,

although only a small contributor to the total mass, may contain the information

necessary to the understanding of the wave interactions in the spall formation.

Figure 36 presents the sectioned views for a selection of the targets tested.

This figure demonstrates the general trends as discussed during the introduction to

this subsection.

Note also that the test against the 3.5-inch (0.0889) target did not perforate.

The sectioned view as presented in Figure 37 shows the target to be very close to

being defeated. This compared well with the value of 3.48 inches (0.08839 meter)

calculated from Equation 4-1.


Spall Panel Data

Three primary parameters were examined in this section. These were the

number of holes in panels 1 and 2 of the spall bundle and the half-cone angle of

the spall field as determined by the perforations of the first spall panel. To

generate a concept of what these parameters relate to, Figure 38 presents the

computer captured data showing the perforations of the first witness panel for the

same tests as were presented in Figure 36. This allows an easy correlation as to








the perforation and its result. The data reduced from the raw computer data are

then presented as Figures 39, 40, and 41.


Spall Mass Data

Spall mass was collected using the spall box discussed previously. All mass

recovered was cleaned and sorted according to material. Any fragment of 1 gram

or more was individually processed, and the location where it was recovered in the

spall box was recorded. The possible recovery locations, in order of the implied

increasing energy, would be on the floor of the spall box in front of the spall

bundle, between panels 1 and 2 of the spall bundle, between panels 2 and 3 of the

spall bundle, between panels 3 and 4 of the spall bundle, and behind the spall

bundle. All material particles less than 1 gram from the same recovery area were

processed as a composite and labeled as dust. After completion of all data

reduction, the material was photographed on a special mat identifying where the

fragments had been found and their material nature.

Figure 42 presents the total spall mass recovered as a function of the target

areal density. As explained by Dyess [10], the collection technique used for the

spall mass recovery was such that all mass in the spall field was recovered with

the possible exception of a portion of the residual penetrator. This recovery

included both the effective, highly energetic mass, and the slow, ineffective mass.

This figure presents a composite of these data.

Figure 43 presents the data generated by counting and weighing the indi-

vidual recovered spall fragments. Again, as stated by Dyess [10], all spall frag-

ments of 1 gram or more were individually recorded. This figure presents the total

of such fragments recovered.








Figures 44 and 45 present the same data as above in a different and more

detailed manner. First, the portion of the spall mass which originated as part of the

penetrator is shown (Figure 44). Next, the spall mass which was originally part of

the target is presented (Figure 45). Finally, the percent of dust is presented in

Figure 46 as the percent of the total recovered spall mass. This percentage figure

gives an easy indication of the degree of fracture which the armor had undergone.

The plot of the nonferrous mass indicates a problem which was mentioned earlier.

Some of the penetrator mass was obviously not recovered when thin armor was

tested. This mass was in the stopper plates behind the spall bundle and not

recoverable.

Just as it was necessary to find a method that would allow for the modeling

of the distribution of the various size holes within the spall panel, it was also

necessary to find a method of determining the masses of the fragments which

made these holes. In general, the holes in the panels were divided into four

classes: Class 1, up to 1/4 inch (0.00635 meter) in diameter; Class 2, 1/4 to

1/2 inch (0.00635 to 0.0127 meter) in diameter; Class 3, 1/2 to 1 inch (0.0127 to

0.01905 meter) in diameter; and Class 4, greater than 1 inch (0.01905 meter) in

diameter. For example, if our model said that there would be 10 Class 4 holes in a

panel and the distribution was given by polar zone, then it was necessary to know

what the average mass was of the 10 largest fragments. Then, if the model said

20 Class 3 holes, the average mass of the next 20 largest fragments was needed,

etc. The plots used to accomplish this are presented in Figure 47. To obtain this

graph, the fragment masses were arranged in descending order. The largest one

was then plotted as the 1 fragment. The two largest were then added together and








the average mass was plotted as the 2 fragment. Thus, if the average mass of the

10 largest fragments were desired, simply read across the graph on the 10 frag-

ment line until the appropriate test number was encountered; the average mass is

below on the scale.

Of course this technique would have little value unless it were repeatable and

could be modeled for other target thicknesses. This is, in fact, the case as is

shown in Figure 47. Here data from different tests at different armor thicknesses

are plotted. As seen, there is an obvious relationship between these curves. At

the thicknesses where repeated tests were made, good correlation exists. As the

target thickness increases, the curves move to the right, implying increased frag-

ment size. This fact, of course, has already been demonstrated. Now consider

the two thinnest targets (0.50 and 0.75 inch [0.0127 and 0.01905 meter]). Notice

how the 0.50-inch (0.0127 meter) target data spreads across the plot for the three

cases and how the slopes of the curves are basically the same at the highest

number count. The problem here is that the target is severely overmatched. This

results in an irregularly formed hole through the thin armor due to pieces being

fractured off the armor around the hole. This can also be seen in the hole data

(Figures 30 and 32). One large piece broken from the target will shift the entire

curve to the right. However, this is not repeatable. To a lesser extent, this

problem occurs in the 0.75-inch (0.01905 meter) target curve as well. However, for

the thicker targets, the techniques generate repeatable curves. Notice that as the

target thickness increases, the basic curve moves to the right; meaning that the

average weight of the fragments increase. Also notice that as the target thickness








increases, the slope of the upper portion of the corresponding curves increases

slightly. These observations were consistent throughout the range where the

target was not severely overmatched (1 inch [0.0254 meter] and higher).


Spall Cap Velocity Data

The spall cap velocity was measured for this subsection. This was the

velocity of the leading point of the spall field and usually consisted of the residual

penetrator fragments mixed with some of the target material. As stated previously,

the spall cap velocity was normally used to model the velocities of the rest of the

field by employing an approximately parabolic distribution and an energy match.

An approximate value for the BAD energy were first calculated by the empirical

relationship


EBAD =El t~ (4-2)


where:

EBAD is the BAD field kinetic energy
E, is the impact kinetic energy
tt is the finite target thickness
is the limit thickness.

The spall field was then divided into a series of quarter steradian zones. The

central zone was assigned a velocity equal to the spall cap velocity. Each








subsequent zone was assigned a percentage of the spall cap velocity based on

the equation


v = V (cos e) (4-3)

where

v is the velocity along the e ray
vMP is the spall cap velocity
e is the ray angle from the shotline.

Note that Equation 4-3 provided the velocity along a ray. The band of angles

for a given quarter steradian zone were used to get an average velocity in the

zone. The total energy of the BAD field was then computed using this velocity

distribution and the assumed mass distribution and compared to the energy

computed from Equation 4-2. The velocities, as calculated from Equation 4-3,

were then modified until a match in the BAD energy using the two techniques was

achieved. This process is explained by Flint [3] in more detail including examples

of results in vulnerability analyses.

Figure 48 presents the spall cap velocity data as a function of the target areal

density. Note that the spall cap velocity is actually presented as a nondimensional

parameter by dividing it by the impact velocity. This transaction also negates the

small effects caused by the small variations in impact velocity.









Projectile Direction










a. 5115 ft/s (1559 m/s)
(CLG0854)




7 -


...........


c. 7034 ft/s (2144 m/s)
(CLG0855)


b. 5976 ft/s (1821 m/s)
(CLG0853)


d. 8225 ft/s (2507 m/s)
(CLG0856)


Figure 25. Comparison of the Actual Craters Created by the Penetrator

















3.60




2.80


nr
w
112.00




1.20




0.40


0.40 120 2.00 2.80 3.60
DEPTH (in.)

0 CLG 0 CLG0852, CLGO853
0 CLG0855 x CLG085


NOTE: in.-r I 6. 0.0254Dmtr
Figure 26. Database Data from the Crater Tests
















HYDRODYNAMIC LIMIT
-------- ----------


6,000


I I I I I I I I I I I I I BIll I I IIII
7,000 8,000
VELOCITY (ft/s)


NOTE: ft/s Feet per second = 0.3048 meter per second

Figure 27. Penetration versus Velocity


0.8-


0.6-


OA -


02-


-I


5 I,
5,000







62




I I ; I I I ; I I I ; I

500.0 0856-



400.0
8 s855
w
S300.0
_.1 0853
0
>
w 200.0
I-


100.0



0, . . . . . . . .

0.0 0.4 0.8 12 1.6 2.0 2.4 2.8 32
ENERGY (MJ)

NOTE: cc Cubic centimeter
W Megajouwe
Figure 28. Calculated Crater Volume versus Kinetic Energy





6.0






C0 4.0
w
z

I-
I-

2.0






0.0 ,
5,000 6,oo 7,000 8,000
VELOCITY (f/s)
NOTE: in. Inch = 0.0254 meter
t/s Feet per second = 0.3048 meter per second
Figure 29. Limit Thickness versus Velocity













I 01017
I01
6.0
ir 01014

I 5.0


wU 4.0 I
-J

Ui 3.0 -.I


a:2.0 I

LU
W.O

0.

c 1.0 I
w
>
0.0 -- 9

0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0
TOTAL TARGET AREAL DENSITY (kg/rn2)
NOTE: in. Inch = 0.0254 meter
Figure 30. Average Profile Hole Diameter as a
Function of the Target Areal Density


1A

12

w
a 1.0
Z
_86D


0.6
(I 9541 6 1 l

0 0 866
~0,4


< 02 IVX&
@1017
0.0 .. 01 -----------------------" 9"
I I I i I I I I I
0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0
TOTAL TARGET AREAL DENSITY (kg/rn2)
NOTE: in. Inch = 0.0254 meter

Figure 31. Average Spall Ring Depth as a
Function of the Target Areal Density


01003


!







64





I I J 1 I
7.0 1OJ7


60 *1014
LU
5.0
<* 01016

4.0
z
a:

0.0
u 2.0


u. 1.0
<
0.0 - - )

0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0
TOTAL TARGET AREAL DENSITY (kg/rn2)
NOTE: in. Inch = 0.0254 meter

Figure 32. Average Spall Ring Diameter as a
Function of the Target Areal Density










Projectile o Direction


b. Case 2


c. Case 3


Figure 33. Sectioned Views 2.0-Inch (0.0508 Meter) Targets


a. Case 1










Projectile o Direction


b. Case 2


Figure 34. Sectioned Views 2.5-Inch (0.0635 Meter) Targets


a. Case 1



























a. Case 1


b. Case 2

Figure 35. Rear View 3-Inch (0.0762 Meter) Targets










Projectile o Direction


a. 0.75 Inch (0.01905 Meter)


c. 2.50 Inch (0.0635 Meter)


b. 1.50 Inch (0.0381 Meter)


d. 3.00 Inch (0.0762 Meter)


Figure 36. Sectioned View of Selected BAD Targets








Projectile o, Direction


Figure 37. Sectioned View 3.5-Inch (0.0889 Meter) Target



















o, h 'r~
J



.&t






a. 0.75 Inch (0.01905 Meter)


b. 1.50 Inch (0.0381 Meter)


c. 2.50 Inch (0.0635 Meter) d. 3.00 Inch (0.0762 Meter)


Figure 38. Computer Generated Plot of the Perforations of the
First Spall Witness Panel for Selected BAD Tests




































Figure 39.


Number of Holes in Panel 1 of the Spall Bundle
as a Function of the Target Density


' I I I I I I I
80.0
0 877
70.0
-j @1013
UJ 60.0 : 1015 @880

< 0 IflP58
cD 50.0
w
-J 01017
0
M 40.0 0 863
LL
0
Cr 30.0 8075
w
20.0
z
10.0

0.0----------------------- -
I I . . . . I .
0.0 100.0 200.0 300.0 4W0.0 500.0 600.0 700.0
TOTAL TARGET AREAL DENSITY (kg/rn2)
Figure 40. Number of Holes in Panel 2 of the Spall Bundle
as a Function of the Target Area[ Density


I I I I I I '

140.0 0 119 7
1015
858
120.0 1014
z 0880
a-100.0 0 1017
UJ
w
-J
0 80.0

0 863
60.0 876
857 1018
2 40.0

20.0 *1003

0.0 "-- I
I II I I I I I I 1

0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0
TOTAL TARGET AREAL DENSITY (kg/rn2)



































Figure 41.


Spall Half-Cone Angle as Measured
on Panel 1 of the Spall Bundle as a
Function of the Target Areal Density


I I I I I I

3,200.0 : 010 3

2,800.0

' 2,400.0 010161

2,000.0 -

- 1,600.0 1017 863

_. 120.0 85) 886
ICI6 877
800.0 5
O ~ooo '1013
400.0
0.0.......................................

0.0 100.0 200.0 300.0 400.0 500.0 600.0
TOTAL TARGET AREAL DENSITY (kg/rn2)

Figure 42. Total Spall Mass as a Function
of the Target Areal Density


_~~ @0 @1018
U j 40.0 8 7
LU 875

LL 30. 857
0.
Z
z
020.0
o
U_

Z "10.0
_J

0.0 a9

0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0
TOTAL TARGET AREAL DENSITY (kg/rn2)













I I


I i


* 86(


Number of Fragments Whose Mass
are Greater Than One Gram as a
Function of the Target Areal Density


320.0

280.0 863
1016 -
240.0

'858* 8

0 -10140 77
CC- 16D.0 eas0
W a 6880
LL
z
0 120.0
Z o1 3

I- 80.0 1013
0 01017
40.0

0.0 - - -
' I I I I I I1 I I
0.0 100.0 200.0 300.0 400.0 500.0 600.0
TOTAL TARGET AREAL DENSITY (kg/rf2)

Figure 44. Total Nonferrous Spall Mass as a
Function of the Target Areal Density


S877
0)160.0
A

Z- a58
t'20.0 1013
0D 0 1014 1OiC 0 14 D3
cc 01017
LL
U-80.O @1015 0 8ii

w
Co
2 40.0
ID

z



I ,I1 i I, Ii I IlI

0.0 100.0 200.0 300.0 40.0 500.0 600.0
TOTAL TARGET AREAL DENSITY (kg/m2)


Figure 43.


. I I I z






































0.0 100.0 200.0 300.0 400.0 500.0 600.0
TOTAL TARGET AREAL DENSITY (kg/rn2)

Figure 45. Total Ferrous Spall Mass as a
Function of the Target Areal Density





01013

0.320

0858

0 10140 877
0240


LL
O
S0.160 8L0
UJ
o 01017 *a66
w
C. 0.080 883



0.0


0.0 100.0 200.0 300.0 40.0 500.0 60.0
TOTAL TARGET AREAL DENSITY (kg/rn2)

Figure 46. Percent of Dust as a Function
of the Target Areal Density


3200.0


2,800.0

2,400.0


2,000.0

1,600.0

1200.0


800.0

400.0


6/"5





01016 -



l l I



880~ 866
1015 0?7



I 1.
, I I I i I I I j














1,000.0







100.0
I-
z

u.


Z 10.0
x
x -
x i 0O* 4D
*( CO C)0

x *j-x 00 .0 0 0

1.01 0,... 40, ...... ?a w" ".'..6. .
1.0 10.0 100.0 1,000.0 10,000.0
AVERAGE MASS OF N LARGEST FRAGMENTS (g)


0.50 in. 0 2.00 in.
X 0.75 in. 03 2.50 in.
+ 1.00 in. 3.00 in.
1.50 in.

NOTE: in. -Inch = 0.0254 meter I

Figure 47. Mass Distribution Plot
















--0.800
wI I I I

8



o
1-0.600 0
4M4


~0.400 ol


WL I 1003
> 0200
-J 1018

CD3
0.0 --- To


0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0
TOTAL TARGET AREAL DENSITY (kg/rn)

Figure 48. Spall Cap Velocity Expressed as
a Percent of the Impact Velocity as
a Function of Target Areal Density









Enhanced BAD Velocity Characterization

Method 1: Make Screen Method

The series of tests, which used just the make screens, generated inconclusive

data. Because of the destructive nature of the environment and density of the

spall fragments within the small area where the measurements were taken, the

data were frequently good for only the first fragment through the screens. Thus, at

best, the velocity of the leading edge of the spall field was determined. This was

not satisfactory. Figure 49 presents a typical set of traces from a front and back

screen. Although some data were obtained, there was a significant degree of

noise which could have actually been data from a subsequent or simultaneous

impact of another fragment.


Method 2: Radiographic Method

The slicing technique was developed so that a better understanding of what

was transpiring could be gained. With this better understanding, it was hoped that

the more complete and complex data generated in the previous tests could be

understood. This would eventually lead to a system which could be employed as

an addition to the normal test setup without sacrificing any of the required data.

Figures 50, 51, and 52 present a comparison between a standard spall field

radiograph taken behind a 0.75-inch (0.01905 meter) target and the radiograph

obtained behind the same target for this type of test. In reducing radiographs, the

ratio between the distance from the radiographic source to the fragment and the

distance from the radiographic source to the film was essential. This ratio was

used to determine the position in real space of the fragment shown on the film. If

a fragment could be recognized in orthogonal radiographic views then, through an








iterative process, its position could be determined. Figures 50 and 51 illustrate the

problems associated with this procedure. Notice the images on the two figures of

the spall cap at T2 (time 2). Figure 50 shows a large piece of the spall cap torn

loose and following the lead piece. In Figure 51, the shadowing was such that this

cannot be seen. This was a simple, but obvious, example of the problems

associated with shadowing which make the exact resolution of the position of a

fragment difficult, if not impossible. To determine the velocity vector for a

fragment, it was necessary to locate the fragment in four views (orthogonal at two

times). This increased the difficulty level significantly. Not only does the

shadowing problem exist but the fragments were tumbling, thus changing their

projected appearance. This can also be seen in Figures 50 and 51. Now consider

Figure 52. Since only a defined slice of the BAD field was allowed into the field of

view of the radiographics, orthogonal views are not necessary. The ratio of the

distances was controlled. Now the makeup of the spall field could be determined.

For example, consider the fragment labeled A in Figure 52. Its path can easily be

determined. Notice that the tumbling and the different angle of projection has

changed its projected shape slightly, but it was still easily recognized, its position in

real space easily computed, and its velocity vector easily determined. Notice also

the fragments labeled as B in Figure 52. These fragments were easily tracked, as

shown, from the T1 to the T2 position. Notice how they have moved apart and, in

some cases, changed their projected shapes. The group of fragments labeled as

C in Figure 52 illustrate these traits even more succinctly. Figures 53, 54, and 55

present the same comparison for a 2.5-inch (0.0635 meter) target.

Tables 9 and 10 present the findings for the 2.0-inch (0.0508 meter) target.

There were significant differences in the fragment velocities, both as a function of








angle (theta) from the shot line, and even along the same theta ray. This fact is

again shown in Tables 11 and 12 which present the same data for a 0.75-inch

(0.01905 meter) and a 2.5-inch (0.0635 meter) target.

Figure 56 presents all of the measured fragment test data and the predicted

fragment velocity data from Equation 4-3. As can be seen from this figure, the

predicted velocities were generally lower than the actual measured values. This

was expected since the predicted values are based on the single bubble assump-

tion. Figure 57 presents this data in a different manner. Here the spatial distri-

bution of the fragments at 500 microseconds are shown along with the predicted

position of the bubble from Equation 4-3. Again, the difference between the

predicted positions and the actual data is obvious.














10.0


8 .0 ----------. ........ .... ........ ..........


6.0

44 0 --------.-----.......... --------.--.-----.---------.----- ------- .---- .--


2 .0 ........... ----- --- -........... .. :........ 1 ----- ........ .......... L .........


0.300000 0.440000 0 .-';8= 0.720000 0.86000 1.00000
TIME x 10 0-2
CH03 TRIGGER OCCURRED 342.095299 SECONDS AFTER START
CLG954 SCREEN #3


a. Start Screen Trace

10.0


. . . . . ..- . . .... . .. . . . . . .. . . .... . . . . . .
2.0










4.0 - -........ . ...... .. .......



2 .0 .............. ... ...... ......... .


0.000-
0.300000 0.440000 0-580000 0.720000 0860000 1.00000
TIME x 10-2

CH04 TRIGGER OCCURRED 342.095299 SECONDS AFTER START
CLG954 SCREEN #4

b. Stop Screen Trace


Figure 49. Typical Traces from the Make Screens



















































Figure 50. Standard Overhead Radiographic
View behind a 0.75-Inch
(0.01905 Meter) Target


Figure 51. Standard Side Radiographic
View behind a 0.75-Inch
(0.01905 Meter) Target















































Figure 52. New Side Radiographic View behind
a 0.75-Inch (0.01905 Meter) Target



















































Figure 53. Standard Overhead Radiographic
View behind a 2.5-Inch
(0.0635 Meter) Target


Figure 54. Standard Side Radiographic
View behind a 2.5-Inch
(0.0635 Meter) Target













































Figure 55. New Side Radiographic View behind
a 2.5-Inch (0.0635 Meter) Target