v. hohler, a. j. stilp and k. weber- hypervelocity penetration of tungsten sinter-alloy rods into...

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P e r g a m o n

I n t. J. l m p a c t E n g n g , Vol. 17, pp. 409-418, 1995Copyright © 1995 Elsevier Science Ltd

Printed in Great Britain. All rights reserved0734-743X/95 $9.50+0.00

H Y P E R V E L O C I T Y P E N E T R A T I O N O F T U N G S T E N S I N T E R - A L L O Y R O D SI N T O A L U M I N U M

V . H o h l e r , A . J . S ti lp a n d K . W e b e r

Fraunhofer-Institut ~ r Kurzzeitdynamik, Ernst-Mach-Institut, Imp act Phy sics Division,

Eckerstr . 4, 79104 Freiburg, Germ any

S u m m ar y- -T h e penetration of tungsten sinter-alloy rods having length-to-diameter ratios o fL/D = 10 and 12.5 into alumina targets was investigated in the velocity range Vp = 1.2 5 to 3

km/s. Th e depth o f penetration (DOP ) test and the time resolved oberservation usin g a 600 k V

flash X-ray system were applied to assess the protection efficiency of the ceramics. F rom DO P

tests, the residual penetration into a steel backing yields the d ifferential efficiency facto r DE F

and the mass efficiency factor MEF. DE F increases with vp; M EF decreases. O n the othe r hand,

DE F decre;Lses as ceramic thickness increases; M EF increases and converges to D EF for

residual penetration zero. Fro m the time resolved measurements, position an d length reduction

o f the ro d during penetration in the ceramics were obtained. T he process c an be described b y

Ta te 's fluid jet m odel in good approximation. The target resistance param eter R, defined in the

modified Bernoulli equation, characterizes th e ceramic performance. Th e averag e R values are

5.4, 6.1 an d 4.8 G Pa a t impact velocities Vp = 1.7 , 2.5 an d 3 km/s, respectively, i.e. the re is no

strong dependence o f R on vp.

N O T A T I O N

CS Comp ression strength R

D rod diameter st:

DE F differential efficiency facto r sa

DO P depth o f penetration t

E Youn g modulus ulh ceram ic sheet thickness v

HE L Hugoniot elastic limit vp

HH-RH A high ha rd RH A UTS

HV Viekers hardness W S

1 instantaneous rod length Y

L0 launched rod length oil/a2

L reduced rod length at impact 8

M EF mass efficiency factor Pc

p semi-infinite penetration in HH -RH A pp

PR residual penetration in HH -RH A pa

backing

target material resistance (modified

Bernoulli equation)

head posi t ion of the rod in the

ceramics

tail position o f the rod in the ceramics

t ime

penetration velocityinstantaneous rod velocity

impact velocity

ultimate tensile strengthtungsten sinter-alloy

projectile material flow stress

(mod ified Bernou lli equation)

yaw and pi tch angles

elongation

density o f ceramcis

density o f projectile m aterial

density o f steel

4 0 9



Pene t r a t ion o f tungs ten -a l loy rods in to a lu m ina 41 1

impact . A 1 .5 mm rubber fo i l is inser ted in between the f ront cover p late a nd ceram ics for s t ress

dampening. P i tch an d ya w angles are ~ , teasured by f la sh X-ray sys tems dur ing impact .

In the ease o f observing the penetrator ins ide the ceram ics , the la teral d im ens ions of the ceramics a nd

the use o f cor tf inement are res tr ic ted . The avai lable 600 kV f lash X-ra y sys te m del ivers p ictures of

acceptable qu~dity for max imal la teral ti le d imens ions of 100 mm . Therefore the targe t ar rangem ent of

Fig . 2 was used for these measurem ents , performed at Vp >_ 1 .7 km/s . No w the ceram ic block is on ly

par t ly Conf ined because o f the 50 m m window fo r the f l ash X- ray observa tion . T he ce ram ic b lock i s bu i l to f 20 m m f il es a t 1 .7 km /s and o f 10 m m t i l es a t 2 . 5 and 3 km /s ; one t es t was done w i th 5 m m and one

with 20 m m 1ti les a t 3 km/s . T he m easured parame ters are d ef ined in F ig . 3 . T ime is recorded by

tr igger ing the 180 and 600 kV sys tems with a shor t c i rcui t t r igger fo i l and b y coun t ing the t ime betwee n

the two f lashe,¢ . The m omen t of impact ( t = 0) w as determined f rom the 180 kV f lash X-ray picture . T he

accu racy of the penetrat ion t ime t is + 0 .15 Ixs. The u ncer tain t ies o f l , s~ and SH are + 0 .1 mm and + 0 .2

mm , respectively .

All ceramic' t i les are square in shape and plane gr inded. Th ey are g lue d together , to the b acking, a nd

to the conf ineraent with a two-com ponent epoxy adhes ive.

T he m anufac tu re r o f the A l203 ti l es was Hoechs t C eram T ec , Germ any . A l l f il e s a r e p roduced

according to the same product ion procedure, character ized by the t rade nam e A1898. This guaran tees a

good co ns is tency of the m ater ial propert ies , g iven in Table 1 .

1801<V FLASH X -R AY

U 1.5mm RUBBERI

" ® I I CERAMICS1 8 0 k V T ~ I I I

- , . I L l I I I

TRIGEER FO IL 10,20ramMILD STEE L CONF.

180kV FLASH X-RA Y

U 1.5mmRUBBER

EERAM,CS

600kV| I I

TRIGGER FOIL 10ram MILD STEEL CONF.

FIG. 1. DOP tes t ar rangem ent appl ied

at 1 .25 and 1 .7 km/s .

FIG. 2 . Arrangem ent for DOP- and t ime resolved tes ts

used a t vp > 1 . 7 km /s .

Vp

f = 0 S ~

L =

Time = f

t - - - - - v

///

¢-o/

/

/

/

/

FIG. 3 . Def ini t ion of parameters for t ime resolved measurements .



412 V. HOHLERe t a l .

TABLE 1. PARAMETERS OF ROD PROJECTILES AND TA RGETM A T ER IA L S ( * N A H M [ 2 2 ] )

Projecti l e % L0 L0/D L pp UT S H V SMate ri a l [km / s ] [m m ] [m m ] [g / c m [GPa] [GPa] [% ]

1W SI 1 .25/1 .7 72.5 12.5 72.5 17.6 1 .2 ± 0 .02 4 .2 ± 0 .1 10 ± 1WS2 2 .5 /3 .0 50 10 49.9 /49.5 17.6 1 .49 + 0 .015 5 .35 ± 0 .1 8 .8 ± 2

S t e e l p s t U T S H V

b a ck in g [ g / c m ] [ G P a l [ G P a l

H H - R H A 7 .8 5 1 . 4 5 ± 0 . 1 4 . 4 ± 0 . 2

C e r a m i c s p, CS HV gr a in s iz e E HE L Poi sson

[g /cm3] [GP a ] [GP a ] [ trm] [GP a ] [G P a ] r a t i o

A1203 3.8 4.0 21 6 - 12 360 5.3 - 7.5 * 0.24 - 0.26

R E S U L T S

The e xpe r i me n t a l da t a a re summ a r i z ed i n Ta b l e 2 . Expe r i me n t s wi t h Nos . < 2 019 a re D OP t e s t s (F i g . 1 ) .

Exp er imen ts wi th Nos . ___ 7349 a re D O P tes t s in com bina t ion wi th t ime reso lved measu remen ts (F ig . 2) .

Bes ide the tes t No s . , the sym bols used in the d iagram s a re g iven. S ince Vp in the exper im ents shows a

cer ta in spread sK, sa , 1 , u and v have been c orrec ted to Vp = 1 .7, 2 .5 and 3 .0 km /s acc ording to , e .g . , sK

( V p l ) = ( V p I / V p 2 ) ' S K ( V p 2 ) . N o a d j us tme n t o f t i me t wa s pe r fo rme d , u a nd v me a ns a ve ra ge ve l oc it i es wi t h u

= s r / t a nd v = sH/t . R ha s be e n c a l c u la t e d on t he ba s i s o f the m od i f i ed Be rnou l li e qua t i on a nd m e a ns an

a ve ra ge va l ue r efe r r i ng t o pe ne t ra t ion ti me t. Y = 2 a nd 2 .3 GP a w e re u se d fo r W S 1 a nd W S 2 ,respec t ive ly .

Th e DO P te s t revea ls the res idua l pene t ra t ion PR, the sem i- inf in i te pene t ra t ion p and th e d i f fe rent ia l

a nd ma ss e f f i c i e nc y fa c t o r s wi t h

D EF - (p - PR) Psi M EF = P p~

Po hc Pchc +P aPs t

P R/P , DE F a nd M EF a re p l o t t ed ve r sus po h~ / L i n F i gs. 4 , 5 a nd 6 . Th e no rma l i z a t i on by L i s ne e de d

be c a use o f the t wo d i f f e re n t L / D- ra ti o s u se d i n t he e xpe r i me n t s . Th e da t a i n t he se t h re e d i a g ra ms re fe r t o

t he e xpe r i me n t a l i mpa c t ve l oc i t y vp, i. e. , p ha s be e n c o r re c t e d a cc o rd i ng t o t he d a t a i n T a b l e 3 . S i n ~

pa / p , DE F a nd M EF de pe nd on l y s li gh tl y on vp , t he c o r r e c t e d da t a i n t he d i a g ra ms a re a l so va l i d in goodappro xim at ion a t the fou r cent ra l ve loc it ie s 1 .25 k in /s , e tc .

The ma i n re su l t o f F ig . 4 i mp l ie s t ha t P R / P i nc rea se s wi t h Vp. N o re ma rka b l e c ha nge o f t he c u rve t r a c e

i s obse rve d de pende n t upon Vp. The p o i n t s ma rke d by a n a r ro w me a n e x t ra po l a t i on t o P R / p = 0 . T he

correspon ding h~ va lue i s som e kind o f semi- inf in i te pene t ra t ion in A1203. A t vp = 1 .7 k nds the inf luence

of the two d i f fe rent conf inemen ts (see F igs . 1 and 2) and o f the d i f fe rent la te ra l t i l e d imensions can b e

seen. Bo th confinements behave a l ike for la te ra l ti l e d imensions of 100 mm in the to ta l h~ range . On th e

other hand, pa is a l it t l e le ss for la tera l t i l e d imensions > 150 mm f or p ~ / L > 3 .25 ( l~ > 6 0 ram).

The re fo re , t wo e x t ra po l a t e d va l ue s a re g ive n a t 1 .7 km/ s . Th e t i me t o pe ne t ra te 60 mm c e ra mi c s i s i n the

o rde r o f t = 65 ~ ts ( s . Ta b l e 2 ). Ac c ord i ng t o Ande rson a nd Mor r i s [14 ] , e dge e f f~ t s p l a y a ro l e i f t > 2 t* ,

whe re t* i s the av erage t ime o f the longi tudina l and shea r waves ne~:led to prop aga te to the la te ra l t a rge t

e dge a nd ba c k t o t he t r a j e c t o ry . In t he c a se o f 100 nun l a t e ra l t i l e d i me ns i ons wi t h a 10 - 20 nun

c onf i neme n t , t * i s a bou t 18 - 22 ~ ts . S o i t ma y b e c onc l ude d t ha t fo r t he t e s t a r ra nge m e n t a pp l i e d he re ,

edge e ffec ts p lay a ro le i f t > 3 t* .



Penetrat ion o f tungs ten-a t ioy rods into a lumina 413

The targets bu i l t up b y 5 , 10 or 20 m m th ick t i les show a neg l ig ib le in f luence of the t ile th ickness on

PR/P a t 3 km/s ( see Table 2 , Nos. 7839 , 7843 , 7844) .

The general tendencies of DE F dependent up on Vp and h~ are indicated in Fig. 5 . Fo r Vp = co nst. , D EF

decreases wi th h~ and converges a t PR = 0 versus M EF, which had a l ready been observ ed by Ernst and

H o o g [ 1 8 ] in the o rdnance veloci ty range . Fur thermore DEF grows wi th vp . This behavior i s very

in terest ing and ma y be expected . How ever the curves becom e f la tte r a t h igher ve loci t ies and come c loser

together , i .e . , fhe increase of DE F w ith vp is reduced at higher velocit ies, nearly disa ppears from 2.5 to 3km/s and is strongly dependent upon 1~.

TABLE 2. LIST OF DATA

N o . S y m b o l No. of cer. tiles of h, lat tile vp (xl/ct2 l~.(vp)thickness dim.

5 1o 20 mm [mm] [mm] Ira/s] ['1 [mm]

2017 1 19.8 180 1246 1.0/<1.0 17.5

2018 2 39.6 180 1246 1.0/<1.0 5.0

2019 3 59.8 180 1252 0. 01 <1 .0 0.0

2002 o 1 20.2 100 1705 0.31<1.0 42.62003 o 2 40.1 100 1709 1.8/<1.0 28.9

2004 o 3 61.1 100 1702 1.51<1.0 16.72000 o 4 81.4 100 1 7 0 5 4.8/<1.0 4.2

2014 A 1 20.0 150 1 7 1 7 0.8 1<1 .0 43.4

2011 A 2 40.0 150 1 7 2 1 <0.51 <1.0 31.7

2012 A 3 60.0 150 1717 0.8/<1.0 14.7

2013 A 4 80.0 150 1716 1.0/<1.0 2.8

1986 V 1 19.9 180 1 7 1 0 0.3/<1.0 44.6

1985 V 2 39.5 180 1711 0.51<1.0 30.2

1984 V 3 59.6 180 1698 1.0/<1.0 15.2

1983 V 4 79.0 180 1708 1.0/<1.0 2.2

7393 D 2 40.6 100 1711 0.7/<1.0 29.7

7349 [] 1 2 51.0 100 1691 0.8/<1.0 19.4

7394 D 3 60.0 100 1 7 0 6 0.5 1<1 .0 14.5

7395 D 4 80.7 100 1 7 1 0 ~1.0 1<1. 0 4.67899 1 10 100 2552 0.2/1.7 60.27900 2 20 100 2522 1.0/6.4 50.7

7901 3 30 100 2537 0.11<0.5 39.1

7902 5 50 100 2550 0.1/1.9 23.97903 7 70 100 2516 0.5•0.2 10.2

7896 + 1 10 100 3024 <2.013.1 66.87905 + 1 10 100 3023 <1.0/4.8 67.0

7907 + 1 10 100 2994 0.2/1.4 68.0

7836 + 2 20.5 100 2984 2. 01 <1 .0 58.1

7847 + 2 19.9 100 3002 0.511.5 58.3

7848 + 2 19.6 100 2968 3.0/1.6 58.87904 + 3 30 100 3025 0.5/0.2 50.07845 + 3 30.8 100 3000 0.0•3.0 50.2

7837 + 4 40.8 100 2991 0.3/<1.0 38.67840 + 4 41.1 100 3000 0.2/<1.0 40.1

7849 + 4 40.4 100 2995 4.8/0.2 41.37838 + 6 62.0 100 3037 0.3/<1.0 21.67850 + 7 69.8 100 2980 <1.0/<1.0 18.77839 + 8 82.0 100 3003 <1.0/<1.0 7.57843 x 4 81.1 100 2998 <1.01< 1. 0 8 .8

7844 0 15 80.8 100 2995 <1.0/0.0 9.0

7851 + 10 101.2 100 2964 <1.0/0.1 07852 + 10 100.5" 100 2963 <111.5 0



4 1 4 V. HOHLER e t a l .

TABLE 2. LIST OF DATA (CONTINUED)

No. t sK 1 u R

[ ~ 1 I m m ] Im m ] [ m / s ] [ O e a ]

7393 21.2 20.5 56.8 961 5.1

7349 26.0 24.4 52.7 943 5.47394 53.0 47.6 30.5 895 6.0

7395 81.1 72.4 13.2 888 5.1

7899 5.0 7.8 45.1 1560 5.5

7900 10.6 16.4 39.9 1547 5.77901 17.5 26.3 32.1 1503 6.77902 29.7 44.9 21.2 1511 6.37903 31.5 47.2 19.3 1498 6.4

7907 4.5 8.9 44.9 1973 4.2

7847 3.0 5.9 46.3 1967 4.3

7848 4.2 8.2 45.1 1952 4.7

7904 14.7 28.6 34.4 1945 4.7

7845 12.7 25.0 36.3 1969 4.37849 19.3 37.6 30.9 1948 4.8

7850 32.9 63.1 14.8 1918 5.17843 39.0 72.2 7.9 1852 5.8

7844 38.7 73.4 8.4 1897 5.4

7852 39.3 73.9 8.9 1881 4.9

TABLE4 . S E M I - I N F IN I T E P E N E T R A T I O N p A N D V E L O C I T Y D E P E N D E N C E O F p I N T H E B A C K I N G

STEELI-~-RHA

vp p L dp /dvp

[km/s] [mm] [mm] [I0 z m m/(m /s)]

W Sl 1 .25 33 .0 72 .5 6 .27

W SI 1 .7 62 .4 72 .5 6 .27

WS 2 2 .5 68 .3 49 .9 2 .13

WS2 3 .0 76 .3 49 .5 1 .16

q-4 -

I I I • = 1 . 2 5 ' 2 0 / 1 8 0~ . [ ] = 1 . 7 ~ 0 / i 0 0

° - i l l o = I . ~ , ~ O A o o

B ÷ v : L~.~O, so

• •= ? . . . . 5 / 1 . 0 / / 1 0 0

• I~ ~ × = 3.d.~0/I00+ = 3.6'10'100

[ ] • < > = 3 . 6 1 S ; / l O 0

¢q. ~ + +O -

I • • ~L

_ , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

~ = Z E R O I : ~ K I ' R A T I O N I N ~ - r r ; r . ~ A C K I N GT r - - - - r " i ! 1 ~ - - - i I

o . o 1 . o z . o 3 . 0 ., , . o 5 . 0 o z o e . o

r t ' ,_oc~c~ ~ /cm*"3)

O -

d-

F IG . 4 . R e s id u a l pe n et ra ti on p R v e r s u s c e r a m i c b l o c k t h i c k n e s s h ~ . T h e a r r o w s y m b o l s m a r k e x t r a -

p o l a t e d v a l u e s 1 ~ (P R = 0 ) . 1 . 2 5 / 2 0 / 1 8 0 e t c . m e a n s Vp = 1 . 2 5 k m / s / 2 0 m m t i l e t h i c k n e s s /1 8 0 m m l a te r a l t i le d i m e n s i o n .



P e ne t ra t i on o f t ungs t e n -a l l oy rods i n t o a l umi na 415

i v • ÷ •m + +

= . _ . 0 r TO

~. • ~ )

l @ = 1 2 , 5 , ~ 0 / 1 8 0 LX= 1.7/'~0/1,50 × = 3.0~ /~, "100t'~ ' f.~ 4 [] = 1.7,/~/100 v = L;~exYlso + = 3.0 16/100

/ ,¢

l o = 1.7/zo/loo • = z~,,1o; oo <>= 3 .6 /5 / loo

| /I t I r I I I

o.o 1.o z.o ~.o ~.o ~.o ~.o 7.0 e.or h o c * h c / L ( g / c m * * 3 )

FIG. 5 . D i ffe rent ia l e ff ic iency fac tor D EF versus ce ram ic b lock th ickness 1~.

¢O

O

i , r °t

• = L 2 5 , 9 ~ O / t 8 0I D = 1.~"67ioo

o = L '~ ? Z 0 7 1 0 0

i ! 1 1 v = 1 . 7 , A Z O / l e O• = ? . ~ / I 0 / I 0 0

o I I [ I X = 3 . 0 / ~ , . / 1 0 0

+ = 3 . 0 / 1 0 / 1 0 0

¢=

3 . 0 / ~ / 1 0 0! t

0.0 1.0 zo 3.0 ~.o 5.0 6.0 7.0 8.0rhoc *he , / L (g / c m**3)

F IG. 6 . M a ss e f f i c ie nc y fa c t o r ME F ve r sus c e ra mi c b l oc k t h i c kne s s 1~ .

The M EF pa ra me t e r g i ve s the be s t qua n t it a t ive a s ses sme n t a bo u t t he p ro t e c t i on improv e me n t o f a r e a l

t a rge t u s i ng c e ra mi c s . The MEF da t a a re p l o t t e d i n F i g . 6 . MEF i nc re a se s wi t h h¢ a nd a c h i e ve s i t s

ma x i m um a t P R = 0 . F u r t he rmore , ME F goe s dow n wi t h vp fo r 1~ = c ons t . S o a n i nc re a se o f ME F a t a

high er velo city vp2 bec om es po ssible on ly since h~ (vp2) can be th icke r than 1~ (vpl), i fvp2 > Vpl.

F i g . 7 show s som e e xa mpl e s o f f l a sh X- ra y p i c t u re s o f t he pe ne t ra ti on p roc e s s t a ke n wi t h t he 60 0-kV

sys te m. No . 71394 i s t a ke n f rom a rod wi t h c a l i be r 5 .8 mm , t he o t he r s f rom rods wi t h c a l i be r 5 nun . F o r a

be t t e r qua n ti t a ti ve compa r i son , p i c t u re No . 7394 i s r e duc e d by a f a c t o r 5 / 5 .8 . One m a y se e t ha t t he rods

be ha ve a c c o rd i ng t o t he f l u id j e t m ode l. T he re a re some d i s c on t inu i ti e s o f t he ma t e r i a l f l ow a t t he

in te rfaces beV~een the t il e s . This indica tes an inf luence of the in te rfaces on the pro cess . O n the o ther

hand, su ch an inf luence on PR, SK or 1 e tc . (see Table 2 and F ig . 7 , Nos . 7839 , 78 43, 7844 , 78 52) ca nno t

be obse rve d i n the t e s ts ma d e a t 3 km/ s w i t h 5 , 10 o r 20 mm t h i c k ti le s . The re fo re a ge ne ra l c onc l us i on

cann ot be mad e tha t t i l e th ickness has a negl ig ib le inf luence .

The R da t a i n Ta b l e 2 de pe nd on t i n t he s a me m a nne r a t a l l ve l oc it ie s . R i nc re a se s wi t h t d u r i ng e a r l y

pene t ra t ion , achieves a p la teau and decreases s l ight ly dur ing la te pene t ra t ion . Th is beha vior had a l rea dy

be e n obse rve d a nd e xp l a ine d by H a uve r e t a l. [16 ] a t o rdna nc e ve loc i ti e s. The re duc t i on o f R du r i ng e a r l y

pe ne t ra ti on oc c u rs o n l y i n t e s ts w i t hou t a c ov e r p la t e , a s done he re a nd i s c a use d by t he i mp a c t da ma ge .The sma l l r e duc t i on du r ing l a t e pe ne t ra ti on i s e xp l a i ne d by t he p re de s t ruc ti on o f t he c e ra m i c s i n f ron t o f

t he rod . The ve l oc i ty de pe nde nc e o f R i s r e la t ive l y smal l. The a v e ra ge R da t a a re 5 .4 , 6 .1 a nd 4 .8 G P a a t



416 V. HOHLERe t a l .

1.7, 2 .5 and 3.0 km/s. R is in the order of HEL (see Table 1, Sternberg [9]) . No increase o f R up to 3.0

km/s ca n be observed , as w as expected by P ar tom and Li t t le f ield [21] .

The data for SK, Sa and I are plotted in Figs. 8 and 9 versus normalized t ime t .vp/L and norm alized

head posit ion pcsg/L. Th e curves we re calculated on the basis of Tate 's m odel (Tale [5]), using the

average R valu es for A1203 and Y = 2 and 2.3 G Pa for WS~ and WS2, respe ctively. The ca lculation w as

done within the l imits vp and v ' , where v ' = (2(R-Y)pp) ~/2. No w, according to A nderson et al . [19], the R

v a lu e o f HH - R H A i s 5 GPa . Th e r ef o re v ' i s c a l cu la ted u s in g th e R v a lu e 5 G Pa o f HH- R H A a t 3 k m /sand the average R values 5.4 and 6.1 G Pa of AI:O3 at 1 .7 and 2.5 km/s, respectively. There is good

agreement between experiment and calculation. Some deviations occur during late penetration. I t is

interesting that the simple one-dimensional mod el delivers a good description of the process . Ho we ver

this fact should not be overinterpreted. There is a need to develop improved theoretical models.

Never the less , the R values de termined f rom t ime reso lved measurements can be considered to be

characterist ic quantit ies in describing the protection performance of brit tle materials also.

Fig. 10 shows the average rod erosion (L-I) /sK versus sg. This erosion decreases with vp and behaves

according to R, i .e . , the erosion increases during early penetration up to a plateau and slows down

slightly during late penetration. The decrease during late penetration depends upo n Vp and n early

disappears at 3 km/s.

7394 1.7 km/s 7901 2.5 km/s

7 9 0 4 7843 7844 3 km/s 7852

FIG. 7. Flash X-ray pictures taken from the penetration process.

i _ ' = 1 . 7 2 0 ' I 0 0 , ~ . 4 , ~ . ~ -- 2 .0 G P a

~ ~ ~ > : = 3 . 0 ' 2 0 ' I 0 0 , R - ~ . 8 , Y - - ~ 3 G P a' ~ - = 3 . 0 ' 16' 100) ~ a.o' 5 ; l o o ~ . ~ J " ~ "

q " ' - ; - - c " . ' ;, -

o i . . 4 ......... ~ "

~ ' . ~ & 5 Lo L 5 i o

t'*~'lq,%

1

f - -

3 .0

FIG. 8. Front and tail posit ions sK and s a of the penetrating rod versu s t ime t . The curves are calc ulated

according to Tate.



Pene t r a t ion o f tungs ten -a l loy rods in to a lum ina 417

o.O-

0 .0

[ ] = 1 . 7 / 9 .2 0,/ 1 0 0 , R = ~ . 4 , Y = ~ 0 G P a

• = ~ / t 0 ~ 1 0 0 , R - - ~ . I, Y - - ~ 3 G P a, × = 3 . 0 / 2 . 0 / 1 0 0 , R = 4 . 8 , Y = ~ . 3 G P a

" ~ . + = 3 . 6 / t O ' / t O 0~ . . ~ o - - 3 . o ? 5 :, t o o

' " .. \ ' 2 " , .

• i -- • i ~i I

t.o z.o 3.o 4.0 ~.o 6.0 7.0 8.0rhoc*sK % (g ~m**3)

FIG. 9 . Res idua l length 1 versus h ead p os i t ion s~:. The curves are calculated .

q

6 4 --

0 .0

F2

~2 V2~2

~2 : : L T / 2 0 / I 0 0 X = 3 . 0 / 2 0 / 1 0 0 o = 3 . 0 / ' 5 / l o 0

• = z.5,'i0/loo + = 3.d/to;'toot.o zo 3.o ~.0 5 . o 6 . 0 7.0

rhoc*sK % (g 'am**3)

I

8 . 0

FIG. 10. Av erage rod ero sion (L-l) versus h ead po sition st: .

C O N C L U S I O N S

The protect ion ef f ic iency of a lumina ceram ics agains t long rod project i les has b een inves t igated up to

an im pac t ve lce i ty o f 3 km /s . DO P tes t s and t im e r esolved m easurem en ts were per fo rm ed . I t ca n be

shown that T ate ' s f lu id je t model a lso descr ibes the penetrat ion process abo ve ordnan ce veloci t ies in good

approximation. Th e res is tance R def ined in the mo dif ied Bernoul l i equat ion is a go od param eter to

character ize the protect ion ef f ic iency of the ceramics . R shows no remarkable d ependence on the im pact

veloci ty . Despi te the good approximation achieved by Tate ' s model , there is a need to develop an

improved descr ip t ion of the process , taking in to account , e .g . crac k propa gat ion ef fects .

R E F E R E N C E S

1. M . L . W i lk ins , C . F . C l ine and C . A . Honode l , Four th p rogres s r eport o f ligh t a rm or p rogram .

Lawrence Radiation Lab. Rept. UCRL-50694 (1969).

2 . M . L . W i lk ins, R . L . L and ingham and C . A . Honode l , F i f th p rogres s r epor t o f l igh t a rm or p rogram .Lawrence Radiation Lab. Rept. UCRL-50980 (1971).



418 V.HOHLER et al.

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targets by m eans o f flash X -ray photographs. Proc. 35th AR A Meeting, Meppen, G erman y (1984) .

4. V .P . Alekseevskii, Penetration of a rod into a target at high velocity. Fizika Goreniya Vzryra, 2, 99

(1966).

5. A. Tate, A th eory for the deceleration of long rods after impact. J . Mech. Phys. Solids , 15, 387

(1967).

6. D. Yaziv, G. Rosen berg and Y. Partom , Differential ballistic efficiency o f appliqu6 armor. Proc. 9thlnt. Symp. Ballistics, Shrivenham, UK (1986).

7. S. J . Bless, Z. Rozenberg and B. Yoon, Hypervelocity penetration o f ceramics, lnt. J. lrapact

Engng., 5, 165 (1987).

8. Z. Rozenberg and Y. Yeshurun, The relation between ballistic efficiency and com pressiv strength o f

ceramic tiles. Int . J. lmpact Engng., 7, 357 (1988).

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J. Appl. Phys. , 65, 3417 (1989).

10. P. Woolsey, St. Mariano and D . Kokidko, Alternative test methodology for ballistic performance

ranking o f armor ceramics. Proc. 5 th Annua l TAC OM Arm or Co ord inat ing Conference, Monterey,

CA, US A (1989).11. P. W oolsey, Ceramic materials screening by residual penetration ballistic testing. Proc. 13th lnt .

Symp. Ballistics, Stockholm, Sweden (1992).12. I . Mellgard, L. Holmberg and L. G. Ols son , An experimental method to compare the ballistic

efficiencies o f different ceramics against long rod projectiles. Pro c. 11th lnt. Syrup. Ballistics,

Brussels, Belgium (1989).

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ceramic targets, lnt . J. lmpact Engng., 9, 247 (1990).

14. C h.E . A nderson and B. L. Morris, Th e ballistic performance o f confined A1203 ceram ic tiles. Int. J.

I m p a c t E n g n g . , 12, 167 (1991).

15. M .W . Burkett, G. E. Cort, R. B. Parker, A. D. Rollett and S. R. Skaggs, Ballistic performance

evaluation o f 90 w t % A1203 against a subseale kinetic en ergy long rod penetrator. Proc. 13th lnt .

Symp. Ballistics, Stockholm, Sweden (1992).

16. G .E . H auver, P. H. Netherwood, R. F. Benck, W. A. Gooch, W. J. Perciballi and M. S. Burkins,Variation o f target resistance during long rod penetration into ceramics. Pro c. 13th lnt. Syrup.

Ballistics, Stockholm, Sweden (1992).17. D. Yaziv and Y. P artom, The ballistic efficiency o f thick alumina targets against long rod

penetrators. Pro c. 14th lnt. Syrup. Ballistics, Quebec, Canada (1993).

18. H .J . Ernst and K. Hoog, Protective power o f several ceramics, correlated to som e static material

parameters. Proc. 13th lnt . S ym p. Ballis tics , Stockholm, Sweden (1992).

19. C h. E . Anderson, V. Hohler, J . D. Walker and A. J. Stilp, Penetration o f long rods into steel and

glass target: Experiments and computations. Proc. 14th lnt . S ym p. Ballis tics , Quebec, Canada

(1993).

20. A .A . Kozhushko, I . I . Ry kov a and A. B. Sinani, Resistance of ceramics to penetration at impact

velocities above 5 km/s. J. de Physique 1V (Colloque C3, suppl, au J. de Physique III), 1, 117

(1991).21. Y. P artom and D . L. Littlefield, Dependence of ceramic armor resistance on projectile velocity.

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22. H. Nahm e, Ernst-M ach-Institut. Private comm unication (1994).

v. hohler, a. j. stilp and k. weber- hypervelocity penetration of tungsten sinter-alloy rods into...

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