The dynamics of terminal ballistics. Ballistic evaluation procedures for armored grille designs

114 Pages·4.428 MB·English

by  Recht R.F., Ipson T.W.

DRI No. 2025
FINAL REPORT
THE DYNAMICS OF TERMINAL BALLISTICS
Ballistic Evaluation Procedures for Armored Grille Designs
Rodney F. Recht
Thomas W. Ipson
DENVER RESEARCH INSTITUTE
University of Denver
('I)
(Colorado Seminary)
1 February 1962
Research to Develop Design Procedures
for Optimum Armor Air-Flow Grille Designs.
Contract No. DA-23-072-ORD-1302, Performed
under the Technical Supervision of the
Research and Engineering Directorate,
"Ordnance
Tank Automotive Command,
Detroit Arsenal.
NO%
Al' 4 -
FINAL REPORT
THE DYNAMICS OF TERMINAL BALLISTICS
Ballistic Evaluation Procedures for Armored Grille Designs
DENVER RESEARCH INSTITUTE
University of Denver
(Colorado Seminary)
1 February 1962
Research to Develop Design Procedures
for Optimum Armor Air-Flow Grille Designs.
Contract No. DA-23-072-ORD-1302, Performed
under the Technical Supervision of the
Research and Engineering Directorate,
Ordnance Tank Automotive Command,
Detroit Arsenal.
APPROVED BY: SUBMITTED BY:
rir M. Krill eaF echt
Mechanics Division Project Supervisor
Thomas W. Ipson
Research Engineer
'[ DENVER RESEARCH INSTITUTE- UNIVERSITY OF DENVER
FOREWORD
This report was prepared under Department of the Army
Project No. 548-03-001, Army Ordnance Contract No. DA-23-
072-ORD-130Z, Denver Research Institute Project No. 198, "Re-
search and Development to Determine Optimum Armor Intake and
Exhaust Grilles." The work was administered under the techni-
cal direction of the Research and Engineering Directorate, Ord-
nance Tank Automotive Command, Detroit Arsenal, with Mr. H.
Spiro as Project Engineer.
This report is UNCLASSIFIED when detached from the
Appendices which are classified CONFIDENTIAL.
DENVER RESEARCH INSTITUTE- UNIVERSITY OF DENVER
iii
ABSTRACT
The terminal ballistic dynamics of small arms projectiles
and fragment simulating projectiles are presented. These dynamics
include the post-impact residual velocity and direction of pro-
jectiles, projectile break-up and dispersion of projectile frag-
ments, and the mechanics of plate perforation. Ricochet dynamics
concerning steel, aluminum, and titanium armor materials have
been determined experimentally for impact obliquities up to 60
degrees. Analytical equations which accurately predict the dyn-
amics of ballistic perforation were derived and confirmed by ex-
perimental data. These equations consider the effects of obliquity,
plate thickness, edge impact and projectile shape.
A ballistic evaluation procedure, based upon the defined
terminal ballistic dynamics, was developed. While the procedure
was developed specifically for the evaluation of grilles, it can be
used equally well for evaluating any armoring concept or the per-
formance of projectiles.
Several prototype grilles were designed and evaluated.
Some of these will be fabricated and ballistically proof-tested.
DENVER RESEARCH INSTITUTE- UNIVERSITY OF DENVER
v
TABLE OF CONTENTS
Page
I. OBJECT ....... .. ................. 1
II. SUMMARY ...... ... ................ 3
III. CONCLUSIONS AND RECOMMENDATIONS ... 9
IV. INTRODUCTION ....... .............. 11
V. DETAILS ....... ................. 13
A. Terminal Ballistic Dynamics of Projectiles and
Fragments ..... .............. 13
1. Ballistic Ricochet Dynamics ....... 14
Test Procedures ... .......... 14
Test Results ........ 19
2. Ballistic Perforation Dynamics; Full Impact 48
The Characteristics of Ballistic Plate
Perforation ..... ............. 48
Residual Velocity Equation for Normal
Impact ..... .............. 53
Residual Velocity Equation for Oblique
Impact ..... .............. 55
Determination of P, the Angular Change in
Fragment Direction .. ......... 56
Thin Plates Perforated by Cylinders 59
Thick Aluminum Plates Perforated by
Steel Cylinders ........... 65
Plates Perforated by Penetrating Projectiles 67
The Angular Change in Direction,
Penetrating Projectiles .. ........ 69
Projectile Break-up .. ......... 71
3. Ballistic Perforation Dynamics; Partial or
Edge Impact .... ............ 74
Residual Velocity Equation for Edge Impacts 75
DENVER RESEARCH INSTITUTE- UNIVERSITY OF DENVER
Vij
vi
TABLE OF CONTENTS (Cont.)
Page
The Angular Change in Direction.
Partial Impact . . . . . . . . . 85
Projectile Break-up; Edge Impact . 85
4. Minimum Perforation Velocity and Ballis-
tic Limit Velocity . . . . . . . 85
Full Impact . . . . . . . . . . 86
Minimum Perforation Velocity for Edge
Impacts . . . . . . . . . . 88
B. Procedure for the Ballistic Evaluation of
Armored Grille Designs . . . . . . . 91
1. Perforation - Full Impact . . . . . 97
2. Perforation - Partial Impact . . . . 102
3. Ricochet . . . . . . . . . . 104
4. Grille Minimum Perforation Velocity 106
5. Form 198-5 . . . . . . . . . 106
6. Limitations of the Procedure . . . . 108
7. Form 198-3C . . . . . . . . . 109
C. Grille Design . . . . . . . . . . 109
1. Prototype Design . . . . . . . 111
2. Ballistic Analyses . . . . . . . 112
Ballistic Evaluation. Grille Design No.
198-051 . . . . . . . . . . 112
3. Prototype Evaluation . . . . . . . 113
VI. BIBLIOGRAPHY . . . . . . . . . . 115
VII. APPENDICES (The Appendices are classified CON-
FIDENTIAL and are bound under separate cover)
Part A. Ballistic Data. Tables A-I through
A-XII, and Figures A-1 through A-72 (see
Lists of Tables and Figures)
Part B. Bibliography of Pertinent Literature
DENVER RESEARCH INSTITUTE -UNIVERSITY OF DENVER
viii
LIST OF FIGURES (Cont.)
Number Title Page
10. Ricochet Dynamics. Ricochet Impacts. 0. 50 Cal.
Ball M2 Projectile. Aluminum Armor MIL 46027.
60 Degree Obliquity. Velocities in Feet per Second 26
11. Ricochet Dynamics. Ricochet Impacts. 20 mm.,
825-Grain WAL FSP. Aluminum Armor MIL
46027. 40 and 50 Degree Obliquity Velocities in
Feet per Second. . . . . . . . . 27
1 2. Ricochet Dynamics. Ricochet Impacts. 20 mm.,
825-Grain WAL FSP. Aluminum Armor MIL
46027. 60 Degree Obliquity. Velocity in Feet
per Second . . ............... . Z8
13. Ricochet Dynamics. Ricochet Impacts. 0.50 Cal.
APM 2 Projectile. Titanium Armor 4A1 -4V.
40 and 60 Degree Obliquity. Velocities in Feet
per Second . . . . .............. 29
14. Ricochet Dynamics. Ricochet Impacts. 0. 50 Cal.
Ball M2 Projectile. Titanium Armor 4AI -4V.
50 and 60 Degree Obliquity. Velocities in Feet
per Second . . ............. . 30
15. Ricochet Dynamics. Ricochet Impacts. 50 Cal.,
207-Grain WAL FSP. Titanium Armor 4AI -4V.
30, 40, and 50 Degree Obliquity. Velocities in
Feet per Second. . . ............ 31
16. Ricochet Dynamics. Ricochet Impacts. 20 mm.,
825-Grain WAL FSP. Titanium Armor 4A1-4V.
30 and 40 Degree Obliquity. Velocities in Feet
per Second . . . . . . . . . . . 32
17. Ricochet Dynamics. Fragmentation. 0. 30 Cal.
Ball M2 Projectile. Reading Left to Right, Top and
Bottom, 30, 40, 50 and 60 Degree Obliquities . . 35
18. Ricochet Dynamics. Fragmentation. 0. 50 Cal.
Ball MZ Projectile, 30 and 40 Degree Obliquities,
Top and Bottom. ............... 36
DENVER RESEARCH INSTITUTE- UNIVERSITY OF DENVER
16
Figuire 2. Ricochet Dynam-ics. Ballistic Test Appar-atuIs. Target
and Gatc h Pe ndulurns
DENVER RESEARCH INSTITUTE - UNIVERSITY OF DENVER
17
-4
0
-4
14
41
u-
DENVINRTI TUREE EARC -UIVESITYOF DNVE
18
The target pendulum incorporates a counter-balance which
places the center of gravity of the pendulum at the point of projec-
tile impact. This prevents the creation of torsional moments
which would complicate the pendulum trace. Four-wire support,
arranged symmetrically about the center of gravity, was used so
that the pendulum could swing with equal ease in any direction.
Both the pendulum proper and the counter-weight were constructed
of plates so that the pendulum weight could be changed. Weight
was adjusted during testing so that the pendulum swing did not
exceed 3 inches; length of the pendulum suspension was about 5
feet.
The catch pendulum is faced with Celotex and foam rubber
through which the projectile or its fragments pass to be stopped
in sand. Its suspension is similar to that of the target pendulum.
During testing, the catch pendulum was placed so that the result-
ant rebound momentum would be absorbed near the center of grav-
ity. No provision was made to adjust the weight of the catch
pendulum, aside from varying the amount of sand. In some cases
not all of the fragments were captured by the catch pendulum.
For this reason, the measured remaining momentum was used
only to check momentum triangles. In almost all cases the mo-
mentum measured by the catch pendulum agreed closely with-the
value obtained by vectorially subtracting the impulse transferred
to the target plate from the initial momentum.
Where the projectile or fragment simulator removes a
relatively small amount of mass from the target plate, and remains
intact after impact, accurate calculations of remaining velocity,
Vr, impact energy, and remaining kinetic energy can be performed
using the momentum triangles.
Fortunately, it was found that the mass removed from the
plate was negligible compared to projectile mass, except at high
obliquity and high velocity. A test series to determine the extent
of the calculation error due to the removal of plate mass showed
that mass ejected from steel plates, subjected to ricochet impact
by armor-piercing projectiles, did not exceed 3 1/2 percent of
projectile mass at impact velocities up to 2500 ft/sec or 8 percent
up to 3100 ft/sec. Impacts with aluminum and titanium involved
DENVER RESEARCH INSTITUTE- UNIVERSITY OF DENVER