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rNULA..sIFIEIJ/%

R -PORT 110o . 710/197

U)

"A STUDY Or

.. THE 1MECHANISMI OF PE1ETRATION O HOMOGENEOUS "

"ARMOR PLATE jv .-)

INDEXEL

By

--4 E. L. REED"fl"!esobarch Metaallurgisr t

S. L. KRUEGELJr. Phys. Sci. Aide.

L A

'.. • June 14, 1937 *

WATERTOWN ARSENAL f" / WATrRroWN, MASS.

• , *'t / I' __0

.• . : rranhford/ A,;ona1~---1-23 J•--3,OCI)

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•" •: :%'-' ~RE PRODt6•'r GOV ER NM E~lrI.E St• ,

' ~ ~UNCLASSItI.. o4I

DISTRIBUTION OF REPORTS

REPORT NO, TITLE.

DATE DISTRIBUTED 4._.9.Other

Lo- Ord.i • cal Work Arm __~ y y " rvt

Author iLab File 11 1 1 1 1

1,jain Office File 1 41 -

Chief of Ordnance . * 2 2

Technll.cal Staff " 1 1

Springfield Armory 1

lWatervIlet Arsenal - 1 1/ ,

Rock Island Arsenal 1 1 -

Frankford Arsena

picatinny Arsenal 1 1

Aberdeen Proving Ground '"1 1*

Chief, Bureau Ordnance .1

* .-.- Naval Gun Factory 1Ch~ef, Bureau C & R, e

Ch, e f weldin•'," ,' " ,.,• ,• '- ,-p and as

d.-directed

*'-- Local Circulation 1 ie d

Available for special 2 2 3 1

circulation.

Other establishments 2

l requesting work.

Private Parties payingfor work

U c " I

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..

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At -t

THIS REPORT AVAILABLE IN MICROPICHE ONLY

(

r

Report No. 710/3,7 i "Watertown Arsen• -. June 14 1937

A STUDY OF

THE MECHAANISM OF PENETRATION Ok' HOMOGENEOUS

ARMOR pLATE-I

Purprose I

The purpose of this investigation was to study the

nature of deformation in partially and completely penetrated

homogeneous armor plate when subjected to impact with armor

piercing ammunition.

Conclusions

1. Armor pleroi- bullets penctrate homogeneous armor

plate by means of a punching and boring operation. The

compressed metal under bullet impact is in many cases par-

* tially forced back to the surface, forming the well known

oratera.

2. The boring action of the bullet has caused a

torsional flow pattern in the armor plate in the vicinity

of the bullet hole. The torsional flow of the metal is in

the same direction as the rotation of the bullet. The con-

tour of the area disturbed and twisted by the bullet is of

the hour-glRa shahe. the nc irng-1n bei, fit t.e 9•ivo. 111

several oases spiral markings were found on the bullet cores.

I

3. When an armor piercing bullet penetrates armor

plate, the following facts are to be considered:

(a) Some of the energy of the bullet is disl-

pated Into heat, causing a local rise in

temperature in the plate.

(b) Local deformation or faulting of the metal

progresses along planes of greatest slip stress,

L which would normally be at 45 degrees, to the

direction of impact; but in this case, due to

the rotational effects of the bullet, they are

of random orientation.

(a) Sufficient heat has been generated to raise the

temperature of these localized slip areas above

the crItical, or In sorue oases, even to the

melting point. The sudden chilling of these

areas form layers which are referred to as

I • "uwhite layersO.

(d) These "white layers" identify themselves as

martensite In their physical properties, but

1 do not possess the typical martensitic struc-

ture.

4. The ooourrenoe of "white layers" in armor plate:

I (a) They are present in the area immediately sur-

rounding the bullet hole in both high and low

ballistic plate of various compositions.

-2-

(b) The more nearly the steel approaches a true

( nmartensitic condition, the greater the con- -

centration of the 'white layer" becomes, i.e.

the harder the plate, the more concentrated.

the layers. s

5. In general, the greater the ballistic resistance,

the more "white layers" occur.

6. The impact of ball ammunition on armor plate is p

a straight punching operation. No boring action is evident.

"White layer" occurs at surface of slip between the puncning

and the body of the plate.

7. Patterns, wniich resemble strain markings In char-

.1acteristic L~cier formation, were revealed on the back faces

of±_ some armor plates by flaking off of scale while plate p

was being subjected to bullet impact.

8. High power microscopic examination of the"white

U ' • layer" present in the standard composition made unAier oblique p

illumination shows flow lines within and immediately adjacent

to the layer. The surface of the layer was not aflat smoothly

finished face but rather irregularly furrowed.

9. Crack oyetsms within and closely associated with

"white layers" are of the following types:

(a) Hair-line cracks within the "white layer".

(b) Pronounced cracks partially within the 'white

lay"er, either p:.opagated by a tearing or

4p

*0

twisting of the metal. (This latter type

comprises about one-taird of all the cracks

found in the layers).

(c) Rare, Isolated cracks crossing"v•bite layers".

(d) Crack systems with no special relationship

to "white layers".i

10. (a) High Power microscopic examination reveals, in

some cases,the pre3ence of clear cut nonmetallic

incluaions whioh were intact within the 'white

layers'6. However, the absence, in general, of

nonmetallics within the "white layer" may Indi-

cate a possibility of sufficient heat having

been generated in these slip planes to melt the

inlvuiuins which normally would occur in these

areas,

(b) On the other hand, many nonmetallice of the

V telongated type adjacent to or partially within

the "white layer" were dis%,orted but not fused.

11. Dark layers, similar in orientat:.on to the "white

layers" of standard plate, were found In Hadfield's Aus-

tenitic Manganese steel (a poor ballistic plate). However,

these layers consisted of carbide precipitates and alpha

Iroli, snowing that due to Intense heat generated within

these Blip areas, a p~iase change had takcn place.

-4-

0 0 • 0 0 S 0 0 S S S 0

S

122. NG 'White layer" was developed by bullet pene-

tratLions in rolled low cOI101o steel plete.

13. Carblde precipitation in the outer surface of

the bullet core is caused by the heat developed during

bullet impact.

14. In the samples examined, no evidence of fueion

of the metal at the edge of the bullet hole was detectedS

in LomoEeneous armor plate. Likewise, no fusion was evi-

dent in the bullet core.

l1. Hardnese surveys in the vicinity of bullet holesS

J ndtcated:

(a) That about .25 inch of metal around the

bullet hole is work hardened.I

(b) In complete penetrations, maximum hardness

is found at the entrance side of the plate.

(o) In partial penetratiov.d, maximum hardness

is found at the contour of the bullet hole

representing the ogive and extending around

the tip of the hole.S

(d) In the case of partially penetrated armor

plate containing 3.5% Nickel and 2.% Silicon,

maximum hardness was found .006 inch belowtthe tip of the bullet hole.

"- I

0 • 0 0 0 0 0 0 0 • • 0

(e' In some oases, metal deformed near

bullet impact as revealed by macro-

etching, was decidedly work hardened.

Experiviental Progedure

Several homogeneous plates and one cast plate were

selected for examination as follows:I

(a) Plate No. 29 - Higi ballistic properties.

Size 12 x 12 x 1 inch - Manufacturer-Henry Disaton& Sons, Inc.

(b) Plate No. WJ2 - High ballistic properties.ID

Size 12 x 12 x 1/2 inch - Manufacturer-Jeseop Steel Co.

(c) Plate No. Ex 26 - Medium ballistic properties.

Size 12 x 12 x 1/2'- Manufacturer-Henry Diseton & Sona.Inc.I

(d) Plate No. 614-5 - Medium ballistic properties.

Size 12 x 12 x 1/2 inch - Manufacturer-Watertown Arsenal-

Henry Dieston & Sons Co.,Inc., Order 8542, Ingot 12-614.

(e) Plate No. 2 - Poor ballistic properties.

Size 12 x 12 x 1/2 - Manufacturer-Taylor-Wharton Co.

(f) Cast Carburetor Cover No. A - Poor ballistic properties.

Size 21 1/2 x 15 x 1/2 inch - Manufacturer-Watert -i Arsenal.

Representative partial and complete penetrations in each

of the above plates were sectioned. A study of the macro-

etructure and microstructure at the area of bullet impact

was made.

4 -6-

Cheaical analysis was made on several plqtes, the

ann1yees of wnilch were not recorded in the reports sub-

mitted by Aberrdeen Proving Ground.

Spectrographic analysis was made on saruplev cut from

all plateu, except No. 2 and No. A.

The ballistic properties of the plates, as determined

at Aberdeei Provln6 Ground, are found in the following

Partial Reports or. Teat of Thin Armor Plate: 21, 59, 81,

82 and 96.

Experimentsl Re ults

1. Spectrographic AnalysIE

Spectrographic analysee of the plates examined are

given in Table 1.

Ta~ble

Spectrograuhlc Analysls

Plate No:

E0lemenIt 29 WJ2 __x 6 614.-

Ni Pre sent Faint Trece Trace Trace

Cu Trace Present Present Present

* Al Trace Trace Trace Faint Trace

Ti Trace Trace Trace Trace

Ca Faint Trace F&int Trace Faint Trace Faint Trace

0 Sr Trace Trace Trace Trace

• • • • • @ • • • • •-7-0!

I

2. Heat Treat"Unt of Pjtiteg

The heat treatmcnt given the plates by the maiiufac-

t.urer Is etated in Table 2.

Table 2

Heat Trefatmet -of Ely~ts-0

Plate .!N-o Heated to Quen!:Aninp Vedium Daw

29 1575YF Not stated 107%*F

WJ2 Not stated Not stated Not stated

Ex 26 1700OF Oil 1150OF

614-5 1650OF Oil ll0b F

2 Not stated Not stated Not stated

Cast "A" Heated 8 hours to 2102 0 F, air cooled.

Heated 5 hours at 1742 0 F, air cooled.

Heated 5 hours at 1562 0 F, furnace cooled.

Heated 2 hours at 1600 0 F, oil quenched.

Drawn 2 hours at 9256F, air cooled.

•. Chemical Analysis

The chemical analyses of the several plates examined

are given in Table 3.

I -

• • • • • • • • • • •

Table 3

Chemi cal P.nalrv81si

Plate No. C Mn P S SL NL_ _. ._. _ ._1 •S

29 .50 .7C .023 .020 .26 - 1.12 .65 .25 .312

WJ2 .425 .66 .024 .018 2.01 3.56 .24 - - -

Ex 26 .38 .69 - .17 - - 1.14 .65 .30 .296

614-5 .51 .42 .016 .013 .14 .09 1.21 .56 .29 .26r

2 1.17 11.40 .057 .018 .405 - - -

Cast "A" .19 .54 .010 .018 .16b - 1.13 .82 .21 -

4. Ballistic Propertlea

The ballistic properties of the plates as determined at

Aberdeen Proving Ground are given in Table 4.

5. klacroacoi•c and Microsoeggl EZ60141ations

@ Typical macro- and wicrostructures of deformation at pen-

etx'ationO in armor plate are shown in Figures I - 21, inclusive.

6. Hardnefis _ Sur•,e/L

Vickers-Brinell hardness surveys were made in the vicinity

of typical penetr&tions and the results plotted, as shown in

F18ureL 2j - [,.

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Discussion

Macro structure

When armor plate of the homogeneous type is either

partially or completely penetrated by armor piercing bul-

lets, several types of deformation or flow lines are de-

tected in the area of impact. Figures 1, 2, and 3 illus-

traTe the macrostructures of sections cut through bullet

holes after etching in a standard macroetching reagent.

In the first place, the banded structure is deformed

in the vicinity of the bullet hole. Banded structures in

plate are the result of deforming the dendritic segregation

present in the ingot, this segregation being elongated in

the direction of hot-work.

Furthermore, a second type of flow line or "white layer"

is observed which resists etching according to the normal

macroetching practice, and Is not oriented in any particu-

r "lar direction with respect to the axle of the bullet hole.

This *white layer* was detected in standard rolled

and cast chromium-molybdenum-vanadium plates of high and

medium ballistic properties. and also in a high ballistic

dlate containing 3.8% nickal and 2.01% silicon.

Cast plate of the standard chromium-molybdenum-vanadium

composition and of low ballistic properties showed this type

of deformation at the penetrated area.

-11.-

0 0 0 S 5 0 S 0 0 0 0 0 S

4 -

L16ure -1

Plate NoA. 29

Mlacrostructure of partial penetration

of .50 Caliber A.P. bullet into high ballis-

tic plate shows deformation of banding and

"wnhte layer".

Etch: Roeen~aain & Haughton #29, Round 3

MA 398a c

Ia a

I I

I I

__ I

# #41

(FIG

-V.V

i~ ~ ~ ~ i* N -NI~)I

Plate Ex 26

(a) Spalling and defolmation of banding,

as well as "white layer" formation, are in-

dicated in tnhs macrostructure of a corn-

plete penetration of .50 caliber A.P.

bullet into medium ballistic plate.

#Ex 26 Round 4 - MA 383a, b

(b) Shows partial penetrationcf same plate.

#Ex 26 Round 7 - MA 381

Both etched in Rosenhain & Hau4hton'e reagent.

*0 0 0 a 0 0 S 0 S

IN

7i.

* ~;- t ~ -7,*

4t

k___!,

Figure 3

Plate No, 614-5

(a) Shows cracking and slip of metal in a

complete penetration of .30 caliber A.P.

bullet into medium ballistic plate. This

section is cut off-center from the axis

of the bullet, and tnerefore appears to be

only partial. Other penetrations in this

plate butLoned badly, and in this macro

study, the start of one is plainly shown.

#614-5 Round 5 - MA 306

(b) Same plate as above, a partial penetration.

Note another crack whicn, if propagated,

would have caused a button.

#614-5 Round 8 - VLA 330

p

• • • • • • • • • • •

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Macroscopic examination of all samples indicate that

there is a relation between the amount of "white layer"

present and the ballistic resistance. To clarify, the

greater the ballistic resistance, the greater the amount

of "white layer*. The progressive changes in the con-

figuration of the"white layerI'are shown in Figures 4 (a)

to (e), which represent macrostructures of the same area

after removing progressively from 0.02 to 0.05 inch of

metal from each section. It is evident that the distri-

bution and amount of".-hite layerd' vary according to the

position of the plane cut through the bullet hole.

A study of macroetructree thus shown illustrates a

pronounced distortion of the banded structure about the

bullet hole, indicating a flowing of the metal as it is

forced aside by the bullet. It ahould be noted that the

most severe and abrupt distortion of the banding occurs

at the boundaries of the "white layer"; see Figures 2 (a),

2 (b), and 3 (a).

Figure 2 (a) illustrates a standard chromium-molybdenum-

vanadlmA plate from wnich a button was blown off; earily

development of spalling on plates of this same composition

is shown in Figures 3 (a), 3 (b) and 22 (f). The "potential"

button cracks appear to have their origin in the bands.

-12-

0 S S 0 0 0 0 0 0 0!

Figure 4

Progressive changes in the configuration of the

"white layer" are illustrated here. For each successive

picture the specimen was re-surface 6round --nd polished,

wnich resulted each ti'ne In removing from 0.02 to 0.05"

of metal from the surface. After each repolishing, the

suecimen was etched with a different etcning reagent in

order to detertine which brought out the structure the best.

in these, as in the preceding photographs, a distortion

of the bandina. about tne bullet hole is very pronounced,

Indicatiang a "flowing" of the metal as it Is forced aside

by the bullet. It should be remarked that the most severe

end abru-ipt dietortion occurs at the boundaries of the

"white layer".

Notice also the development of the three "white layers"

Drancling from the tip of the crack so prominently in (e).

In (a) tdey can be located by the deviation of the banding,

but are certainly not recognizable as a layer, while in

(b) they can be Identtfied as a very thin layer of this

peculiar structure.

(a) Etched wlth Oberhoffer's reagent #WJ2-Round 3 MA 237

(b) Etched with Stead's reagent 1,A 278

(c) Etrhed witn Rosenhain & Haughton'sreagent, diluted. MA 302

(d) Etched with Humfrey's reagent MA 312

(e) Etched with Dlckenson's reagent M'A 329

• 0 0 S 0 0 • 6 0 S S 0 0

Iý.

-- d

-77-

-~~~~ .- (J - -- ),~- -__-_u i

A macroscopic study was made on several sections of

bullet holes cut parallel to the surface and removed by

various amounts. A macro study of cross sections of bul-

let holes from the same plates has been discussed in the

foregoing.

In the case of the plate WJ2, -4, containing 3.68%

nickel and 2.01% sl.icon, wnich was partially penetrated,

particles of plate were blown off at the entrance end of

the plate, and therefore no d18to-tion was evident on the

surface layers, see Figure 5 (a). At a depth of approxJ-

mately .166 inch below the entrance face of the plate, the

first evidence of torsional flow of the metal as revealed

by the swirling effect of the dendritic segregation is

evident. Near the exit .Ae of' the plate, there is a de-

crease in size of area distorted by bullet impact.

Heavy membranes of "white layer" were present near

the bullet hole in the layers near the entrance face of the

plate. Tae orientation of these layers varied considerably.

Crack systems were promoted by the severe twisting of the

metal during bullet penetration. This plate is particularly

interesetng due to the fact that dendritic segregation per-

sisted throughout the entire plate and evidence of the marked

rotational effect of the bullet was revealed by the swirl of

the dendritic 8e&e6atlon.

-13-.

0 0 0 0 0 B B S S 0 0 0

Figure 5

Plate #WJ2 - 4 HIgh Ballistic Plate

Progressive changeb in the macrostructure. Markeddendritic segregation persists throughout the layersas well an the torsional deformation caused by bulletspin.

(a) Considerable metal blown out by the bullet, there-fore no torsional deformation evident.

Rocenhain & Haughton etch. MA 345

(b) Metal st.l1 blown out, slight swirl evident.Oberhoffer't etch. 1V 7447

(c) True picture of swirl evident sinne we are nowbelow area blown out by bullet.

Obernoff'er's etcn, as are all the following.MA 772

(d) M MA 806

(e) 1MA 853

(f) Note deformation extends below the bullet hole.MA 860

g) AMA 866

(h) 4A 873

(3) MA 876

(k) MA 886

(1) Note crack forms at outer limit of swirl deforma-tton. Corresponds to (c) above. MA 773

(m) MA 80b

(n) MA 854

(o) Note the defornatlon extending below bullet hole.MA 857

(p) Note the deformation which, covering same area,

shows less violent perturbation of metal. MA 866

(q) VA 872

(r) Note beglnnuin of very sltght decrease in area ofdtelturbance. VA 877

(s) MA 885

0 S S 0 0 0 0 0 0 • 0 0 0 9

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F~i.ure 6_

26-6 Medium Ballistic Plate

S

Consecutive layers throuh the surface show muchthe same sort of thing as Figure 5. However, thedendritic structure is almost negligible.

(a) Blackened zone shows metal forced up by bulletimpact. Tae light structureless body of themetal is the normal decarburized surface.

1% Nital MA 285

(b) Swirling structure is slightly masked by theadditional force introduced by the upheaval ofmetal. Oberhoffer's etch as well as the following.

MA 745

(cV) MA 752

(d) Swirl of metal Is undistorted MA 775

(e) MA 803

(f) MA 824

(g) MA 874

(h) Back face of plate. MA 855

(j) Corresponds to (b) above. MA 746

(k) IA 7.53

(1) MA 774

(M) MA 802

(n) MA 825

(o) MA 875

(p) MA 856

(q) Ball ammunition into armor plate. No swirlingaction of the metal about the edges of thebullet hole can be found.

Bullet: Cal .30 Ball MI, 2733 f.s. impact.MA 813

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Figure 7 (a) illustrates graphically the contour of

the area disturbed and twisted by the bullet.

Figure 6 illustrates the progressive changes in macro-

structures of area affected by bullet impact in a standard

chromium-molybdenum-vanadium plate completely penetrated

by a Cal .30 A.P. M1922 bullet.

In the first three layers, the outer portion of the

swirl is masked by the upheaval of the metal forced back

by the bullet.

This upheaval of metal is clearly revealed in 6 (a).

Beginning at and extending below the ogive to a

depth of 0.35 to 0.45 inch, a decided twist is evident and

then It decreases in intensity at the exit face of the plate.

Since the force causing the twisting of the metal has

the same direction as the spin of the bullet, it is reason-

able to assume that this distortion is produced by the

bullet spin.

A study of the macrostructures of this series indicates

that 'white layers" represent planes of greatest slip stress,

oriented 30 to 45 degrees to direction of impact, and persist

at the bullet hole. A circular swirl of deformed dendritic

segregation as the result of the spinning of the bullet

was clearly evident.

Figure 7 (b) illustrates the hour glass shaped contour

of the area affected by bullet impact.

-14-

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Figure 8 e

S

(a) Twisting of metal inside hole made

by armor piercing bullet impact.

Unetched.

1.-4A 832

(b) Scale blown off bac% of armor plate

by bullet impact shows character-

Istic Lfder line pattern. See5 0

Figures 9 (a) & (b). Unetched.

710-200

S

S • S 5 0 • 5 0 0 0 0 5 S 6 • 0

It is interesting to note the similarity of the hour

glass shaped contour of the area in armor plate of the

.-A standard composition and a similar strained area revealed

by Fry's reagent around a partial penetration in a low

carbon steel plate.

To confirm the opinion that the twisting of plate

metal about the bullet hole was caused by the spin of the

bullet, there is illustrated (Fig. 6 (q)) a punching impact

made with ball ammunition. Due to the flattening of the

lead immediately on striking, no spinning action was intro-

duced into the plate, and true to predictions, no torsional

flow could be found in this plate.

Spiral striations on bullet cores as the result of a

boring action through plate are shown in Figure 8 (c).

Twisttng of the plate metal when an armor pierci.ng

bullet strikes armor plate is clearly shown in Figure 8 (a).

Strain markings in the form of LUder lines are oc-

casionally revealed on the rear face of armor plates due

to the fact that scale is sometimes blown off in these

formations, see Figures 8 (b)

This scale pattern has no obvious relation to the o,:-

currence of "white layer".

It has been impossible thus far to reveal strain

jiarkings or Lader lines in armor plate by variou3 methods'

of etcxiing. Fry's reagent, whica is reooomended for,

-15-:t •d ,.JJ :A 1N 3I,•f,;JJ,'\UUL IV Ud-iLlUU~th'••.-

Figure 8

(a) Twisting of metal inside hole made

by armor piercing bullet Impact.

Unetched.

M4A 83•

(b) &cale blown off back of armor plate

by bullet impact shows character-

istic Lftder line pattern. See

Figures 9 (a) & (b). Unetched.

710-200

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revealing strain in low and medium carbon steels, is not

suitable for revealing strain in armor plate, due to the

Sfact that no free ferrite persists in heat treated armor

plate. There are inserted photographs, Figures 9 (a), (b),

which illustrate clearly Lader lines on the front and back

faces of a low carbon steel plate subjected to impact with

Cal .30 ball ammunition at a striking velocity of 2600 f.s.

It is interesting to note that Lfders on the rear face

of low carbon steel plate affected by bullet impact, as re-

vealed by the Fry reagent, are quite similar to the strain

markings on the rear face of the same plate shown by blowing

off scale, see Figure 8 (c).

Micro structure

Normal etching reveals clearly the movement or faulting

of the metal near the bullet hole but, on the other hand,

fails to reveal the internal structure of the "white layer",

a as shown in Figure 10 (a), (b) and (c). The abrupt shift

in the banding continuity from one side of thp "white layer"

to the other in Figures 10 (a) and (b),ahows distinct evi-

dence of a sudden slipping of the metal in the plane tnrouslt

the layer. The degree of this deformatton is evident when

it is considered that in the undistorted roglon beyond the

bullet hole, the banding is perpendicular to the direction

-16-

JbiijjdAj 31NJrINNU :JIV 1V (:3: J(IUUUd J i

Fl.gure-9

(a)IJder lines on face of low carbon plate

after imlpact with ball ammuiwtion

2 600 f. a.

Fry's reagent after heatIng 45 mninutes,

preheatlri6 at 20000.

L'.A 8235

(b) Riear face of same plate.

Frys9 reagent after heating, 45 minutes,

Preheatring at '20000.

MA~ 871

a. , -05LFL OK/ TorD 0,- ,hL4107.

.0 - r92" 51L, I [O5 0 ' c A.7 0 /

j. i j J 4 .i j.. i j~), Iv uj~ji wii, Jo.I

Fig~ure .9_Le

Scale blown off back of low carbon plate

subjected to A.P. bullet impact of various

striking velocities. Scale blown off back

of plate shows characteristic Lkder line

patterns.

710-182

0

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0

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Figure 10

(a) The abrupt shift in the banding continuity from

one side of the layer to the otner shows distinct

evidence of a sudden slipping of the metal in the

plane thru the layer. The degree of this deformation

is seen when one consitders that in the undistorted

region beyond the bullet hole, the bands are perpen-

dicular to the direction taken by the bullet, wnereas

here they are off this normal by approximately 600.

Tne pronounced drawing in of the metal toward the tip

of the layer occurs in almost every case.

l, Nital #Ex 26 Round 5. YWA 175

(b) The maroetch does riot define the banding so clearly

as the others but the slipping of the metal, as well

as the change in direction of the bandin6 across this

peculiarly snaped boundary, is evident. The path of

tnis layer docs not follow any apparent rule, and thie

one case illustrates typical behavior, (not in sanape,

but in the E'pparent, irregularity of path), of a con-.

siderable proportion of' the layers.Rorgenhain & HaugnLon's reagent. #614-5 Round 5c

?AA 412

(c) in this case the layer seemE to be the boundary of tin

angular deflectioii of the bo.ndlng, rather than tiho nlice

of a linear shift in their continuity. The "density"I o•i

these bandin&s al~o appe',rs different on etien r3ide,

flo. a k id of conp;reqn1on of ttie banid i2 on tie K

rinar'cst tne bul]ct hole. iLs; Nital, /}Ex 26-Pouni , ?.!A 17,;

],i,"j hi,' .3 3 N Jf.'Jd .JAUJ .j V U]i~i IU.J~fld.iJL

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taken by the bullet, whereas in the cases illustrated

they are deflected from 45 to 60 degrees from normal.

The "white layers" which are shown in Figures 10 (a),

(b), ana (c), and in 12 (c) and (d) are typical of tihoae

"examined in various armor plate compositions, and it is

evident that they are not oriented in any particular di-

rection with respect to the axis of the bullet. They occur

either parallel to or at various angles to the bullet axis,

* , see Figures 11 (a), 11 (c), 12 (c), (d), 13 (a) and (b).

It was determined that "white layers" were present

occasionally at the edges of the bullet hole, as shown in

Figures 11 (a) and 20 (a). It is interesting to note that

these particular "white layers" are etched more readily than

those away from the bullet hole. Typical flow lines are

evident in the layer at the edge of the bullet hole,

Figures 11 (a), and 12 (a).

In the case of some "white layers" close to the bullet

hole, flow lines are prepent in the outer borders of the

layer, see Figure 11 (b). Also, after a relatively deeo

etcnin6, v coring effect is noted in some of these "white* layero", see Figures 11 (b), (c) and 12 (b)- It is pos-Ible

that the heat of bullet impact has tempered some of the

"white layers", thus producing troostitic borders (softer

material).

-. 7--

Jb~j• 1NJL~rJlUd•\U J.iv J~ C .uuJ3I UU

Figure 11

(a) Illustrating the sort of fine 'flow' lines found

at the outer edges of many of the broader layers.

Here they branch into a relatively thick layer which

forms a coating on the bullet hole, where they be-

come more pronounced. A coating like this which

shows the "flow lines so plainly in all cases, e,.ches

much more readily than layers in the interior of the

metal, regardless of whether 'flow'lines are found or

not.1% Nital #614-5 Round 5 MA 170

(b) Etching to the extent shown in this micrograph,

which brings out a set of 'flow" lines to a consider-

able depth into the layer, was rarely found on a

lightly etched and untempered specimen. The layer in

also unusually broad.

1% Nital #614-6 Round 10, MA 399

(c) Layer which runs quite parallel to the bullet hole.

Notice here also the "coring" effect caused by the

partial etching of the borders while the center re-

maine unetched.

l1 Nital #614.5 Round 3 UA 164

3SNJdX- IN:.t• AOJ\ IV (UJ;lJJUUddiU

- * . . g.° .* .*- '-. **o . .,-_. *1 .,~* .. . *... ,-Y - ' - -- . . - . .

iii'

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Fi. i WA ,-.

J (. .. a i:' I ,,.3 .,U U

Figure 12

(a) Deformed metal at lower edge of the penetra-

tion cavity. Usually the "white layers" at the

edge of the bullet holes are readily etched as

shown in this photomicrograph,

2% Nital #614-5 Round 8 HAI-i1O

(b) Coring effect at edge of 'white layer". This

coring effect is probably caused by tempering

of the martensitic "white layer' as the result

of heat from bullet impact, thus producing

troostitio borders.

5%1 Nital #614-6 Round 8 HAl-140

(o) Layer branching out at 450 angle from bullet

hole.

1% Nital #614v5 Round 9 MA 172

(d) Tnis"white layerwhich terminates in the vi-

cinity of much slag, does not seem to have

any relation to it.

1% Nital #614-6 Round 10 MA 398

3SNldxj 1NJI4NUJAOD IV UjZ)(1COUd'U

L;-4

-444

IV'if,'

ACr

A-41

IL.- ,

16 1

On one occasion it was determined that after a "white

layer" was formed, the metal slipped along a plane which

was clearly revealed by etching, see Figure 14 (a).

"White layers" do not follow nonmetallic inclusions of

the stringer type, as shown in Figures 12 (d) and 16 (d).

It has been shown under hig~n power examination that

rounded nonmetallics are present in the "white layers",

in contrast to deformed or broken nonmetallic inclusions

outside the "white layer", see Figure 15 (c).

On the other hand, Figures 15 (a) and (b) show unaffected

nonmetallice adjacent to and partially within the "white

layer".

It was difficult to correlate the formation of crack

systems with "white layer" formation. Basing a conclusion

on the direction and occurrence of cracks in relation to

the "white layers", they may be divided into two classes:

(a) Cracks which may have formed during the formation

of "white layer", Figures 16 (a) and (b), 14 (c)

and (d), 17 (a), (b), and (c);

(b) Cracks which may have folmed after the layer,

Figures 11 (b) and 13 (a);

In nearly one-third of the "white layers" examined,

crack eystems were found showing evidence of twisting, or

rupture by tearing the metal apart, Figures 16 (b), 17 (a),

(b) and (c).

-18-

]-SWJJX- 1N.INUJA(JU IV (JJJIIUULUdJLU

(a) An Interesting concurrence of crack and

"white layer", although no inference can

he drawn es to any inter-relation of the

two.

1% Nital #614-5 Round 10. MA 400

(o) Thi& shows an abrupt shift in the crack's

continuity at the boundary of the 'white

layer", indicating either a slipping of

this whole layer after the formation of the

crack, or a slipping of the metal after the

crack's formation that was part of the

process of layer formation.

1% Nital #A Carburetor Cover MA 229

35.NJd_ J JNh NLU3AOý) IV (J.-l•UUdJU

c~> 'k

gum.

., ~. A.

-4,~

f-/c j WA , ~ 4L

.5i'jj~~~~~~j,~~~, A JJ U ~ jj ~ U j (~~ ~

Flgure 14

(a) This layer obviously was formed previous to aslipping )f the metal along the plane markedby a very faint line cutting across tae layerat the point of its abrupt snift.

1% Nital #614-5 Round 10 MA 406

(b) A "white layer" at high power and, as in everyoase examined, no structure Is discernible.

1% Nital #WJ2 Round 9 .LA 167

(c) A orack which progresses along one side of the

layer, cuts ecross it and progresses along theother side, with no apparent cause for itstermination at either end, or no indication ofits origin.1% Nital #WJ2 Round 9 MA 163

(d) Fine crack progressing down "white layer" andswerving off to an abrupt end.

• .%1 Nital #614-5 Round 5 MA 414

"(e) Typical microatructure of decarburized surfacoof armor plate away from bullet hole.

1% Nital MA 276

(f) Typical trooetito-Porbite structure of metalforced upward at bullet impact.

1% Nital MA 275

3SNJdA. iN3VNU3AOD IV UJilCiOUdd3

4 AA

J.) l4~dd P

•Igure 15

(aO Elongated slag inclusions bordering "white layer".Sketch shows location of slag with respect tobullet hole. Normally, I.e. beyond the region inwhich the bullet exerted its influence, all the

- slag was elongated in the direction of rolling,"that is perpendicular to the bullet penetration.

KA 714

(b) Another nonmetallic stringer, this one penetra-ting into the interior of the "white layer".The deviation from a straight line upon enteringinto the layer suggests a "flowing" of the metalin the layer most severe at, the core, but at atemperature insufficient to fuse the slag.

1$ Nital #614-0 Round 6c MA 713

(c) Dark spots are actually gray-colored inclusionswith smooth spherical. shape in the "white layer".They have been undisturbed by the deformation ofthe metal. It is believed that sufficient heathas been produced in the formation of these "wnitelayers" to melt the norimetallics. Upon subsequentsolidification, the particles assumed their normalohapes and thus presented the appearance of havingbeen unaffecued by the chock of penetration.

Si XZ5000 5% Nital #614-5 Round 8 HAI-129

(d) Long slag strlinger which stops at the "white layer".This is und.oultedly a coincidence, but it does

4 show that the "white layer" formation does not- ... form with any particular relation to the stringer

inclusions.

1% N'itl #614-5 Round 10 MA 401

-',i2~sr• . J I-JiLN J,'J IV (IljillIU JU]U

%# Y

IN.

11 4 A,

15~~ W*. 6-37 6R

I6

* ~Fi~ure 16

(a) The deformation of the banding as well as the

* relationship of "white layers" to the cracks is

especially pronounced in this micrograph. The

complete absence of "white layer" in some places

would indicate that the continuity of Its formation

was interrupted by the simultaneous growth of the

crack. There is certainly in this case some re-

lation between the cracks and layers, but just

what it is, is not obvious.

1% Nital #614-b Round 3 MA 165

(b) This crack in the "white layerP shows either

a pulling apart of a fairly wChesive substance

to form the creck, or else a torsional force

aoting in the crack's formation. This twisting,

jaged type of crack is frequently found, and

. •comprises about one-third of all the cracks

found in layers.

1% Nital #WJ2 Round 9 MLA 168

I

]MiJJ•,A•j J Wf;"NJUcAUy) jV (J:I IUQl~tdJU,

Figure 17

f-t-A IllustratinG in different steels, and at

various magnifications, the twisting Jagged crack

characteristic of a large proportion of cracks in

"white layers".

(a) This micrograph Is not so clear because of the

very deep etch, but it shows the twisting of

crack and "white layer' at high power.

10% Nital #614-5 Round G. MA 166

(b) Notice the termination of the cracking at the

extreme upper part of the picture. On visual

examination of the rest of the "white layer" it

was found to be entirely free of cracks from

this point on.

Rosenhain & Haughton #29 Round 2 MA 395MA 396

(c) Color bandings brought out by this etch show a

4 very definite torsional movement of the metal

when examrried. vieually. Unfortunately the photo-

graphic emulsion does not bring out the true

color values, and. therefore a good deal of the

effect is lost.

Picric A(,id etch. ffAU2 Round .3 MA 407

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It Is believed that this evidence of twist in the

crack systems is the result of torsional impaot. The

"twists in 'waite layers" were found near the bottom and

close to the aide of the bullet hole. Together with the

information obtained from macro study, these pictures

support the view that the spin of the bullet hA".s exercised

a torsional force on the metal.

The "white layers" are resistant to the normal pro-

cedure of etching. Relatively deep etching reveals a fine

acicular structure similar to marteneite in 'white layers"

found in an armor plate containing 3.58% nickel and 2.01%

silicon, Figures 18 (d), (e) and (f). The structure of the

armor plate proper was marteneitic. On the other hand, the

layer appearance i.n a standard chromium-molybdenum-vanadlium

armor plate is similar to that of sorbite, Figures 18 (a),

(b) and (c). Their failure to exhibit an aclular structure

is no proof that they lack the characteristics of hardened

steels since such steels do not necessarily have to assume

one definite type of structural arrangement.

The structure of this ohrome-molybdenum-vsnadium plate

was troostito-sorbitic.

High power examination after continued etching, the

standard composition in 2% nital reveals the presence of

fine, though rounded, detail within the "white layer" and

alco the presence of cracks shown in Figure 19 (o).

-19-

Figure 18

These micrographs show the beat of the results

from an exhaustive series of tests made to discover what,

if any, method of etching would bring out the structure

in these "white layers".

(a) Very deep Nital etch. #614-5 Round 5. MA 238

(b) Deep HCl etch. #614-5 Round 5. 1•A 307

(c) Very deep HC1, HCU and UN0 3 , and finally Rosenhain

and Haughton applied in that order.#614-5 Round 10. MA 305

(d) Deep Rosenhain and Haughton etch,#WJ2 Round 3. MA 303

(e) Rosenhain and Haughton, re-etched deeper th-an (d).The blackened area in the lower right corner appearsbecause the etch was so deep as to eat away the metalsurrounding the "white layer".

#WJ2 Round 3. .A 304

j . (f) Same as (e), but r different locati)n in the opeclnre:i.Note the appearance of layers within the layer.

#WJ2 Round 3. MA 305

(g) Scratch test, showing a considerable necking down of. ,the scratch as it passes thrnough the "white las yv .

#614-5 Round 5. WA 240

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A study of the "white layers" under oblique illumina-

tion revealed many Interesting details which could not be

detected with the use of vertical illumination. The almost

complete absence of characteristic, well-defined structural

outlines (see Figure 19 (a) ) was noted and explained with

the aid of oblique illumination by which it was possible

to photograph the real surface conditions of the "white

regions", Figures 19 (b) and (d). The latter were hard

- -enougn to resist the cutting action of the polishing medium.

They presented to the microscope, therefore, not flat smoothly

finished faces but rather irregular, cracked, furrowed onee,

the structural features of which could not possibly be seen

as normal metallographic outlines.

The relative hardness of the layer as compared to that

of the surrounding metal is illustraLed by the scratch test

shown In Fi6ure 18 (g). Moreover, the hardness of these

layers is evident since they stand out in relief after metal-.

lographic poliehing.

The results of this investigation indicate that thcsu

"Owhite layers" are martensitic as the result of heat gener-

ated by slip. In this connection, it is interesting to notec

that E. A. Atkins found that fractured wires had been sub-

Jected to such intense friction that the skin was converted

Into marteiislte (The Journal of the Iron & Steel Institute,

No. 1, 1927, Vol. CXV, p. 443).

-2-0-3i.Jux j Ir•V4Nd3AU'j IV UtjlWlUJdJU

L•-u re 19

__ _ (a) Microstructure of a "white layer' in thevicinity of a bullet hole. Vertical ilium-.Ination. Note absence of definite micro-structure after hormal etching.

2% Nital #614-5 Round 8 HAl-J06

(b) Same as In 15 (a) - Oblique illumination.Fine cracks are evident within the "whitelayer", aleo flow lines are present withinand adjacent to the layer.

2% Nital #614-5 Round 8 HAl-10l

(c) Same as 15 (b) after additional etching in2% Nital. Vertical illumination. Notepresence of fine though rounded detail withinthe "white layer" and also the presence ofcracks.

X3000 #614-5 Round 8 HAI-113

(d) Fine detail apparent in another "whitelayer". Oblique illumination. Here is evi-dence of the furrowed condition of the sur-face which prevents the presentation of well-defined structural characteristics.

XOOO 5% Nital f614-5 Round 8 HAl-148

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Furthermore, N. Dawidenkow and I. Mirolubow found these

"white layers" in a 0.39% carbon steel sample 13 x 13 x 7 nn

which was subjected to the impact of a ram weighing 50 Kg

and falling from heights between 2 and 3 meters. The

authors stated, "The material of the layer finds itself

in the martenaitic condition only possessing no charac-

teristic needle-like structure, because it was formed wider

peculiar conditions, which have not been investigated, such

as high pressure and high transformation velocity."

"(Technical Physics of the U.S.S.R. 1935, Vol. II, p. 281).

The authors also found that tempering of the layers nroduce&

structural changes and a decrease in hardness. This agrees

with the results on tempering of the layers produced by

bullet impact which are described below.

Temperibg a standard chromiuw-molybdonum-vanadium ariior

plate at 2000C for half an hour causes a transformation at

the borders of tae"white layers" into a constituent which

closely resembles troostite, see Figures 20 (a), (b), and (c)

Tempering this composition at 300*C for half an hour

causes a nearly complete transformation of what IF believed

to be martensite in the "hite layer" into troostite,

Figures 20 (d), and (e). In several instance&, tie exact

o'iiter of the layer was not fully transformron at the 3000C

•emer, see Figure 20 (e).

3-ý.JJd -j I1NrW rJ., U AU) IV UJJI)(JUtJdJU

Fi g•e 20

(a) This specimen, on which the scratch tests and tenp-er!nu tests were made, is shown here before eit herwas done. The deformation of the banding is worth io-tice, as well as the flow lines discernible in thewhite coating around the tip of the bullet hole. Thedifference between this coating and the "white lvyer"Is also brought out, since one of the layers cain btclearly seen within this coating. Compare Fig. 7(a).

1% Nital etch #614-5 Round 5. "'A 171

(b) Same location in the specimen after tempering 50minutes at 2000C, surface grinding, and repolilshing.Here the difference between the coating and the lay-ers has become more pronounced. The configuration ofthe "white layer" is of course different because ofthe change in the sectioning plane, but the layers

1.... ,originally well-defined, have begun to show a slightfuzziness at the edges, which It seems reasonable toarsumr, is due to the tempering action rather thn-the change in plane.

1% flital etch #614-5 Round .5. MA 3549

(c) Layer structure examined closely after the 20000temper. The fuzziness indicated in (b) shows itselfas a slight etching.

1% Nital etch #6±4-5 hound 5. MA 325

(d) After 3000C temper, showing a precipitation ofcarbides on the layer that are slightly larger thanthose fowud in the normal metal. The ease with whichthe layers etched after this tempering confirms thededuction from (b) and (c) that some transformationla beginning to take place.

#614-6 Round 5. MA 353

(e) Another layer in thlo same specimen. The fine"feather" appearance caused by flow lines on the

½;. .. •.. •outer portions of the layer are similar to those t3hownin the untempered specimen, Figure 7 (b).

1% Ni{tal etch #614-5 Round 5. IMA 354

(f) A different compoaltion steel, also tempered at. 300%,"for 30 minutes. This also shows a carbide preciplta-tlcn, but more uniformly than the other specimen.Troobtito-sorbite.

1,% Hital etch 4WJ2 Round 5. MA 365

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44

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II

Tempering a 3.58% nickel, 2.01% silicon composition

at 300 0 C for half an hour promoted a complete treansforme tion

of the layer into a constituent resembling troostito-sorbitU,

Figure 20 (f).

After tempering, "white layers" had the following

metallographic characteristics: (a) they stood out leu6

in relief after polishing; (b) had a slightly lower r'esis-I

tanoe to abraslon; (c) did not appear to be exteneively tur.-

"rowed; and (d) had a greater fineness of uocr2.Q ure.

Rolled low carbon steel plate contairviifý 0.19Z cfj.abor,,

when penetrated by armor piercing bullets, is not subject

to "white layer" formation.

Macroscopic examination of penetrated Hadfield's

Austenitle /.aneaneLJe Steel, containing 1.17% carbon eno.

11.40% manganese, revealed :o darkened zone in the vionIty

of trne penetrations, Figurec 21 (a), (b), (c), and (d).

i.,icroocopic e-:,aamination indicated that theoe darkuned

areas cvL t, of carbide p-ecipitation, deformed austenitic

graino, and darzk l'Iyere simi~lar, with respect to oriontut o;.,

to the "white Jayurs," found in nonauatenitlo stelci, but

which were darkoried readily by the normal etuhln6, see

Flý:urcu ý'l 4! (h), indl (1).

The combine. cilfuct of severe deformation and loc:l

Srfie in temperature c.urnrg Oullet imipact has evidentjly

-PI•

Plate #2

(a), (b), (c), (d), These all show a characteristicblackening about the bullet hole which is a carbideprecipitation caused by heat effect of the pene-trating bullet.

1, Nital etch. MA416, MA417, MA397, MA432

(e) This is the same as Figure (d), but photographedwith oblique Illumination. The faulting, or slip3ines revealed In this are present in all the speci-mens, but are partially obscured by the parallelillumination in the other photos, which was neces-sary to reproduce the carbide precipitation.

1% Nital etch. MA 433

(f) Microstructure of plate in an area far removedfrom the penetration.

1% Nital etch. V!A 390

(g) A micrograph of the faulting lines reveals themto be places of denrue carbide precipitation. Thedistortion of the structure by the impact is evi-dent when this micro is compared to (f).


(h) Ct'bides, precipitated out in the '.eat of im-pact, form aloni grain boundarlos and slip lines.


(1) Cerbides found in Aelected areas as well asgraln boundaries.

1% XNItil etch. MA 39P

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caused decomposition of the austenite into areas containing

carbide and possibly 6ome alpha iron. Also, carbide preclpl,.

tation was present at the boundaries and in the slip planes

-- of the austenitio grains.

The structure of the manganese steel plate at consider-

able distance away from the bullet penetrations consists of

a normal austenitic grain with no evidence of carbides at

the grain boundaries, Figure 21 (f).

- Mi .icroscopic examination of a cross section of bullet in

plate chowed no evidence of fusion of bullet core to plate.

Furthermore, the effect of heat resulting from bullet pen-

etrations on the structure of plate and core is given below:

(1) Carbide precipitation at surface of core Immediately

adjacent to the plate, Figures 22 (a) and (b).

(2) Deformed "white layer" at ed6e of plate in con-

tact with bullet core, Figure 22 (a).

(3) Decarburization occasionally found at the sur-

face of the bullet core, Figures 22 (o) and (d).

(4) Troostitic layer near surface of bullet core,

Figures 22 (c) and (d).

It has been previously shown that bullet cores are

slightly decarburized after heat treatment. Therefore, It

Is difficult to state definitely whether the decarburiza-

tion, found in the present core stuck, is due to heat of

UUll0t In.Jact.

-23-

J •;J ,J.' J Jr• j i]•J ,(Jl) IV (1 .)!iil•OJfj jj JjiI

Figure 22

(a) The flow lin3s In the white coating on the

plate's edge, as well as the indication of flow

• . in the plate itself (upper portion of photo marked 1)

is shown in contrast to the structure of jacket

metal, 2, and the bullet core (lower half marked 3).

S'-1% Nital #614-5 Round 3. MA 430

(b) This micro shows the oore and plate in complet.

S.. .oontget at this point. Notice the carbide precipl-

tate on the core, and flow lines In the plate.C 1% Nital #614-b Round 3. MA 159

(c) Extreme edge of core, which shows ai surface

decarburlzation.

1% Nital #614-5 Round 3. MA 429

(d) Strucoture of core 0.0006 inches from the edce.

Compare with Figure (c). The blackenin6 is due to

tempering from heat generated by impact.

1% Nital #614-5 Round 3. MA 428U

(e) Crack on tip of bullet core. Compare thin core

structure with the structure on the aides, shown

above. 1% Nital #614-6 Rou, d 3. MA 4C1

(f) Unetched photo showing the locations of the

mlicrographs.

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A thin layer of jacket metal located between the

bullet core and plate is shown in Figure 22 (a).

Figure 22 (f) shows a cross section of this bullet core

in plate.

Hardne ss Surveys

A Vilckers-BrInell hardness survey of about twenty-five

penetrations of homogeneous armor plate indicates that in

partiallv penetrated plate, the maximum hardness iu in the

vi.oInlty o* tLe tip of the penetration or neur the contour

of the bullet hole, representing the ogive, as noted in

Figures 23, 24, 25, 26, 29, 31, and 33.

Several tests indicated that about .16 inch away from

the bullet hole the hard~iess dropped fifteen points below

the normal hardne6s of the plate, see Figure 27. Thio

indicated that a tempering effect may have been producea

by the heat of bullet impact. Immediately at the edge of

the bullet hole, the hardness was twenty points higher than

that of the plate.

Hardness surveys were ocoaslonally made follow.1ni" the

contour of the bullet hole, as shown in Figure 28. This

particular plate spalled. The metal near the bullet hole

Is hardened considerably while the hardness throu,. thv

-24-

J 'l.I'i j I N 1 jL '4 J J,',j U i V U j I iIU U U d.JU

cross section of the plate from top to bottom varies as

shown in Figure 28. The areas near the blowing off of

_ _the button are relatively harder.

Hardness readings near the penetration of Ex 26-1

are irregular, see Figure 30.

The hardness of areas near penetrations in Hadfield's

Manganese Steel was increased in some areas about 250 points,

Vickers-Brinell, Figures 31, 32. Bullet impact evidently

promotes pronounced local work hardening in this steel,

but not to the extent, however, to stop the bullet from

penetrating the plate.

As a matter of interest, a hardness survey was made

near penetrations in a low carbon steel plate, Figures 33

and 34. Curves typical of those determined on some armor

plate penetrations were obtained.

A series of interesting hardness surveys were made on

layer3 cut parallel to the surface at various depths, the

Eame sections which were studied macroscopically, Figure6

35 to 51 inclusive.

Hardness surveys at the surface of the armor plate

Investigated, showed that the samples were noticeably

decarburized.

Hardness curves illustrate the fact previously din-

cussed that upheaval of the metal around the bullet lwcatct

Y l - J iN I U 1,'\U J'f Lv UJJi u( JuJd il'

has occurred. This metal has the hardness of heat treated

armor plate while areas away from the bullet hole are

S 'r relatively soft, due to decarburization. Figure 14 (f)

shows the microetructure, the troostito-sorbltic struc-

ture wnIch has been pushed upward by the bullet, walle

14 (e) illustrates the structure of the normal decarburized

surface.

The crater on the surface of the armor plate it [lietrkl

. pushed upward by the bullet. This area of disturbance oi,

the surface coincides with the deformation revealed by

macro-examination, see Figure 7 (b).

Hardness surveys on layers frow the nickel-silicon

plate (WJ2-4) indicated that the metal deformed around tVic

bullet hole, as shown by a macro study, was hbrdened ap-

preciably (Figures 35 - 43).

"Figurns 44 -* 5 show that the b~rdness Increase in

the penetrated chrn:ce-molybdenum-vanadium steel was In--

creased to about -'O points Vickere-Brinell along tIe o~tve.

Also, the work hardened area coincides fairly well with the

p contour of the distorted metal as revealed by trie mrcro-

etch in Figure 7 (b).

-26-

JUjN•,U.J I NjviktU j/\L):j iV L)J1.)IIUUUJ-U

Lnknowle dement

Study or the "whlte layeru formation before and

after teiLpering under very high power was made by

M. R. Norton.

Reepectfully submitted,

E. L. Reed,Research Metallurgi st.

i

S. L. Kruegel,Jr.Phys. S3 .Aide.

-27-

3SIjiOA3 i NdL^'NUJ/AUu .IV UJJIIUU~dJlh

Ha-rdn-er. SlarvOY6 of Pealetr'abione In

Homaogeneous Armor Plate of High, M~editum, and

Poor Ballistic Properties.

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CARBON STEEL PLATE

Homogeneous Carbon Steel Plate.441

12 x 12 x 1/2"

Brinell - 120

C__ _An _Q,_ -.2 _-__ Or

.19 .42 .025 .034 .012 .05

Ammunitior - .3o cal. 165 Sr. MJ922. A.P.

_ Range - 100 yards.

Specification - AXS-54, Rev. 2.

Partial Penetration - Str. Vel. 1500 f/s.

Complete Penetration - Str. Vel. 2300 f/s.

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. .........- .. s .S. . .• + , " .. . .. . g:.• -, , Wo• . ,•. . . .. .r

k, Mi 'gtft%"

,...+ .. .".• . o, o.+ ., * -'. ... .•.• .. .• o-'. -- .• .. '?,,i .. . -'.,-- <i- ....... 1

rrwVt4;:; -4 .-. C... -:p. J! rf Y%4

v. - i - tJft&ft . -' f dm--a " 4-p .I i. r ' *

S~~~~~~~~~~~................ ..... '"...•"... ........ft "-''tb#t

1 -. S•fl _

,4 .,itftft-f.t+ftftftftftlll ft• ,i. I , + + ,~ . t• -l + .- l i

4... . .. ... . ..W ' '-'.. .. ' ... .~f . j......' ,.U -- f.t :::.•. ** . .. ..... - ,,-,.• ! . . .. - a n ... . . A

.ink

4 ... •, ,' "- . 4 :ft..-.4wn

* *-'a., t:\ % . -t .ft .. .. A It .j .+0+., 4. 9 .

.. .. -. • ..b .w.: •, +.¶ ..S3...,.,p~ f. .. .. .t .. !. .. . "' •-S.. . . . .. . .. . ....&.f~tta*~~L .. " . . .... '. .. , -. ,

" " "• ' .ftft.-j* ft..... -.: ¢ + ' • m + • • + + - -, *ft i• 1f t •ft

.. + .. ,.... .... + *... - .. ..9. . . ,+ . • : ,, •

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PLATE NO. 29

High Ballistio

DISSTON - Homogeneous Armor Plate.

12 x 12 x 1"

Actual thiokness - 1.01651

Brinell - 418

C - -- S -_.a_ __Z_ r_ o __Va

.50 .?0 .25 .020 .02o3 1.12 .65 .25

"Ammunition - .50 cal. 750 gr. M-1 A.P.

Range - 100 yardA.

Specification - 31.

Round 1. Str. Vel. 2499 f/s. Partial Penetration.

Helht of Bulge on Back - .01"

Depth of Penetration - .77"

Round 2. Str. Vel. 2566 f/a. Partial Penetration.

HeIght of Bulge on Back - .061

Depth of Penetration - .980

Round 3. Str. Vel. 2,40 f/l. Partial Penetration.

Height of Bulge on Back - .06".

Depth of Penetration - .96".

...... 3SNjd×d IN h..v• ( N hJ.N Q IV__._ __Q_

-- . --- -.- ' -r- -~ - -owrll

* ,I*Y--*PC

411"-

6"

j 4 tj .11 VL

Z !- -.2

Jt 777-h-4""..';I

- I~~ '1t 1

*~~- M21 14 I

.....A

A

.- M W.

It I t B

PLATE NO. WJ2

High Ballistic

JESSOP - Homogeneous Armor Plate

12 Y 12 x 1/2"

Actual thickness- .496"

S Cr

.425 .66 2.01 .018 .024 3.58 0.24

Ammunition - .30 cal. 165 gr. M1922 A.P.

Range - 100 yards.

Specification - 31.

Round 3. Str. Vel. 2599 f/a. Partial Penetration.


Round 4. Str. Vel. 2682 f/e. Partial Penetration.



Heliht of Bulge on Back - .01".

JbNJdXJ I NJNLJU3AU IV UL:i~JflUdd:3U

- - - - -- -- .. - -'

6

APPEN DIX

p. I !

Plate with High Ballistic Limit

Plates 0No. 29 WJ 2

PLATE NO. 29

Size: 12 x 12 x 1 inches

Manufacturer: Henry Dieston & Sons Co.

Type: Homogeneous

Ammwiitlon: Caliber .50 A.P., 750 eratn M-1

Distance from Plate to Muzzle: 100 yards

Brlnell Hardness: 418

Chemical Composition:

C LMn Si 8 P Va Cr Mo Cu

C.50 0.70 0.25 0.020 0.023 0.25 1.12 0.65 0.312

Balli stics

RudRund 3

Penetre tion Partial Partial

Striking Velocity 2568 ft/sec. 2540 ft/sec.

Height of Bulge-back 0.C6 inch 0.06 inch

Depth of Tadent 0.98 inco 0.96 inch

-1.0

I S

-0 0 -0 0 0

Plate wilth Hitch BallUetic Limit

PLATE WJ2

1•ize: 12 x 12 x 1/2" inches

Manufacturer: Jessop Steel Co.

Arnmunition: Caliber .30 A.P., 165 gr. bullet M1922


Brinell Hardness: 555


C Tvi L N1 -r

0.425 0.66 2.01 0.018 0.024 3.58 0.24

Balli-Eic

Round 3 Round 4 npunj Round 9 -"-

Penetration Partial Partial Partial Partial

Striking Velocity 2b99 2682 2639 2945ft/sec. ft/sec. ft/sec. ft/eec.

Height of Bulge-back - .01 inch 0.00 inch 0.01 inch

Depth of Penetration - - -

-2-

1*

K

I

Plate with Medium Ballistic Limit

Plates Ex 26 614-5

PLATE EX 26

Size: 18 x 18 x 1/2 inches

Manufacturer: Henry Disston & Sons Co.

Type : Homogeneous

Ammunition: Caliber .30 A.P. 165 grain bullet M1922

Distance from Platde to Muzzle: 100 yards

Brinell Hardness: 402 - 418


C .__L. IM . & No

0.38 0.69 0.17 0.30 1.14 0.65 0.296

Roturid 4 R~a - Round 6 Hound 7

Penetrati on Complete Complete Complete Partial

StrikingVelocity 2704 2696 2388 2286

ft/eec. ft/sec. ft/eec. ft/sec.

Core thru back - 0.65 inch

Core thru front - 0,02 inch

Diameter ofhole .41 inch - .01 inch

• ••

0 S 0 0 0 0 0 06 0 0

Plate with Medium Balligtic Liwat

PLATE 614-5

i7Size: 1 x 18 x 1/2 inches

""Manufacturer: Watertown Arsenal - Henry Diseton & Sons Co.W.A. Order 8542 - Ingot 12-614

Ammunition: Caliber .30 A.p. 165 grain 11922


Brinell Hardnees: 430 - 444


C _ Si j _ Jj! va CrN' _.j_ . C_

0.61 0.42 0,14 0.013 0.016 0.09 0.29 1.21 0.56 0.252

Bell sls~op

Round 3 Round 5 Round 8 Round 9 Round 10

Penetration Complete Complete Partial Partial PartialC.I.P.Striking 2673 2495 2391 2409 2446Velocity) ft/sec. ft/sec. ft/sec. ft/sec. ft/soc.

Ht.Bule-back - 0034 0.05" 0.06"

Dia.Hole-back .- .0l" - -

Core thruback ,26 -

Spalling,

-4-

p w 0 0 0 00 0

a!

Plate with Poor Ballletic Limit

PLATE NO. 2


Manufacturer: Taylor-Wharton Co.

Type: Homogeneous

Ammunition: Caliber .30 A.P. 165 grain L11922 0

Distance from Plate to Muzzle - 50 yards



S P.

1.1? 11.40 0.405 0.018 0.05?

Ballistics

Round C Round D E2 urd

Penetretion Complete Complete Complete

Striking Velocity 2215 ft/sec. 2357 ft/sec. 2283 ft/eec.

Dia. Hole-back - 0.25 inch -

Core thru back .53 inch - 0.25 inch

Core thru front .07 inch -

Ht. Bulge-back 0,14 inch 0.17 inch

- 5-.

* F • • • • • •

ARb.OR PLATE

(Subjected to Ball Ammunition Impact)

PLATE NO. 1i.- Round 19


MaY'nufacturer: Henry Disston & Sons Inc..

Ammunition: Caliber .30 Ball U1, 110 grain bullet

Striking Velocity - 2733 ft/sec.

Diameter of Hole in back -0.340 (complete penetration)


Brinell HardnesB: 418

Chemir'cal Composition:c S L CSr _ Va

0.50 0.70 0.25 0.020 0.023 1.12 0.65 0.25

-6-

0

* 0 0 0 . . 0.

LOW CARBON STEL

(Used for Study of Defor'mation at Bullet Impact)


Ammunition: Caliber .30 A.P. 165 grain L1922Caliber .30 Ball Ammunition. Ul

Distarce from Plate to Muzzle: 100 yards.



0.19 0.42 0.025 0.034 0.012 0.05

.7.

PLATE NO. 614-5

Medium Ballistic

DISSTON - Homogeneous Armor Plate.

18 x 18 x 1/2"

Actual Thickness - .606"

Brinell - 430 - 444.

.51 .42 .14 .013 .016 .09 1.21 .56 .29

Ammunition - .30 cal. 165 gr. U1922. A.P.

Range - 100 yards.

Specification - AXS - 54.

Round 1. Str. Vel. 2696 f/s. Complete Penetration.

Diameter cf Hole in Back - .70".

Round 2. Str. Vel. 2656 f/s. Complete Penetration. C.I.P.


Diameter of Hole In Back - .005".

Round 5. Str. Vel. 2495 fis. Partial Penetration.

Diameter of Hole in Back - .01".

Round 9. Str. Vel. 2409 f/e. Partial Penetration.

Helght of Bulge on Back - .05".



p 0 0 0 0 0 0 0 0 0 0

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