Crack formation in ice during creep

Publisher’s version / Version de l'éditeur:

Scripta Metallurgica, 3, 6, pp. 367-370, 1969-05-01

READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE. https://nrc-publications.canada.ca/eng/copyright

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la

première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.

Questions? Contact the NRC Publications Archive team at

PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.

NRC Publications Archive

Archives des publications du CNRC

This publication could be one of several versions: author’s original, accepted manuscript or the publisher’s version. / La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur.

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at

Crack formation in ice during creep

Gold, L. W.

https://publications-cnrc.canada.ca/fra/droits

L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.

NRC Publications Record / Notice d'Archives des publications de CNRC:

https://nrc-publications.canada.ca/eng/view/object/?id=bd170ae5-9666-4cf1-a9a4-5300ce9d151c

https://publications-cnrc.canada.ca/fra/voir/objet/?id=bd170ae5-9666-4cf1-a9a4-5300ce9d151c

Ser

TH1

N21r

2

no.

403

c . 2

f i N

~ L Y Z E ~

NATIONAL RESEARCH COUNCIL O F CANADA

BLDG

C O N S E I L NATIONAL DE RECHERCHES DU CANADA

CRACK FORMATION I N I C E DURING CREEP

by

L.W.

G o l d

R e p r i n t e d f r o m

S CRIPTA METALLURG ICA

BUILDING RESEARCH

Val.

3 ,

NO.

6 ,

J u n e

1 9 6 9

P a g e s 3 6 7

-

3 7 0

₁₁

₁₉₆₉

R e s e a r c h P a p e r N o .

403

of

t h e

D i v i s i o n

of

B u i l d i n g R e s e a r c h

OTTAWA

M a y

1969

P r i c e

1 0

c e n t s

_{NRC 1 0 7 8 7}

FORMATION DES FISSURES DANS LA GLACE DURANT

L E FLUAGE

SO MMAIRE

L a r u p t u r e g r a d u e l l e due

5

l a f o r m a t i o n d e s f i s s u r e s d ' u n m a t 6 r i e l

d u r a n t le fluage e s t

un

_{s u j e t qui r e s o i t une attention u n i v e r s e l l e .}

MEme s i beaucoup de r e n s e i g n e m e n t s ont 6th obtenus s u r l a f a s o n

dont l e s c r e v a s s e s individuelles s ' a s s e m b l e n t , c r o i s s e n t en volume

e t finalement s ' u n i s s e n t pour c a u s e r l a r u p t u r e , peu d ' a t t e n t i o n a

6th port6e

5

l a p o s s i b i l i t 6 d ' u n r a p p o r t e n t r e l a f o r m a t i o n d e s f i s -

s u r e s et d e l a d6formation e n fonction d e l a c o n t r a i n t e e t du t e m p s .

D e s r e n s e i g n e m e n t s disponibles s u r l e n o m b r e d e f i s s u r e s e t l e

c o m p o r t e m e n t du fluage avec un alliage a l u m i n u m - z i n c ont r 6 c e m -

ment 6t6 p r 6 p a r i . s . L ' a u t e u r d e c e r a p p o r t a obtenu d e s r e n s e i g n e -

ments s e m b l a b l e s pour l a g l a c e . E n plus d e d 6 m o n t r e r l a c o r r g l a -

tion e n t r e l ' a c t i o n de f i s s u r a g e e t d e l a d 6 f o r m a t i o n J c e s o b s e r v a -

tions d 6 m o n t r e n t une s i m i l a r i t 6 i n t 6 r e s s a n t e d a n s l e c o m p o r t e m e n t ,

mGme s i l e g e n r e de f o r m a t i o n d e s f i s s u r e s diff'ere e n t r e l e s deux

Vol.

3 , ?p. 257-370,

1959

Pergarnon

P r e s s ,

Inc.

P r i n t e d

i n t h e

United

States

A N A L Y Z E D

CRACK FORMATION IN I C E DURING C R E E P

L. W. Gold

Snow and I c e Section, Division of Building R e s e a r c h , National R e s e a r c h Council of Canada

Ot:awa, Ontario

(3.eceived

%rch

1 7 ,

1969)

rnl

- n c gradual. Sreakdovm of a m a t e r i a l d u r i n g c r e e p d u e to the f o r m a t i o n of c r a c k s i s a s u b j e c t r e c e i v i n g w x i e s p r e a d a t t e n t i o n . Although c o n s i d e r a b l e i n f o r m a t i o n h a s been obtaine?.

on hew indii.?.du.a! c r a c k s a r e nucleared, grow, a n d u l t i m a t e l y join t o g e t h e r to c a u s e f a i l u r e , n o t m u c h attention h a s Seen given to the p o s s i b l e i o t e r r e l a t i o r ? between c r a c k f o r m a t i o n a n d

the s t r e s s and t i m e dependence of t i e d e f o r n ~ a t i o n . W i l i i a m s ( 1 ) h a s r e c e n t l y p r e s e n t e d i n -

f o r m a t i o n on c r a c k d e n s i t y a n d c r e c p h e i a v i o u r f o r a n aluminium-zinc alloy.

he

a u t h o r h a s o b t a i ~ e d s i m i l a r information f o r i c e . I n addition t o d e m o n s t r a t i n g a c o r r e l a t i o n b e t w e e n c r a c k -

ing a c t i v i t y a n d d e f o r m a t i o n , t h e s e o b s e r v a t i o n s show a n i n t e r e s t i n g s i m i l a r i t y in behaviour,

e v e n though the m o d e of c r a c k f o r m a t i o n i s d i f f e r e n t f o r t h e two m a t e r i a l s .

:

I t i s the p u r p c s e of t h i s l e t t e r t o p r e s e n t i n f o r m a t i o n on t h e c r e e p d e p e n d e n c e of c r a c k

f o r m a t i o n In i c e t o c o m p l e m e n t t h a t p r e s e n t e d by W i l l i a m s f o r t h e a l u m i n i u m - z i n c alloy, and

t o d r a w a t t e n t i o n t o t h e s i m i l a r i t y in c r a c k i n g a c t i v i t y a n d d e f o r m a t i o n behaviour of the two

m a t e r i a L s .

C r a c k F o r m a t i o n in I c e

I c e h a s a hexagonal c r y s t a l l o g r a p h i c s y m m e t r y . The d e f o r m a t i o n b e h a v i o r of i c e and

c r a c k formation In i t exhibit m a n y of the c h a r a c t e r i s t i c s a s s o c i a t e d with hexagonal m e t a l s s u c h a s z i ~ c . A t e c h i q u e was developed f o r p r e p a r i n g p o l y c r y s t a l l i n e c o l u m n a r - g r a i n e d i c e

( 2 ) . The a v e r a g e g r a i n width wds about 2 m m and t h e length s e v e r a l t i m e s this v a l u e . B e - c a u s e of conditions a s s o c i a t e d with t h e growth of t h e i c e , t h e r e w a s a markeci tendency f o r the

bas'a! p l a n e to be p a r a l l e l t o the long d i r e c t ~ o n of e a c h g r a i n , and f o r t h e a x i s of hexagonal

s y m m e t r y t o h a v e a r a n d o m o r i e n t a t i o n in the p l a n e perpendicular to t h a t direktion.

R e c t a n g u l a r s p e c i m e n s of i c e w e r e c u t s o t h a t t h e load could b e applied p e r p e n d i c u l a r

t o t h e long d i r e c t i o n of the c o l u m n a r g r a i n s . T h i s c o m b i n a t i o n of c o l u m n a r g r a i n s t r u c t u r e ,

p r e f e r r e d c r y s t a l l o g r a p h i c o r i e n t a t i o n , and d i r e c t i o n of loading r e s u l t e d i n d e f o r m a t i o n a n d

c r a c k f o r m a t i o n t h a t w a s e s s e n t i a l l y two d i m e n s i o n a l ( 2 ) .

C r a c k s f o r m e d d u r i n g c o m p r e s s i v e c r e e p when t h e load applied t o t h e r e c t a n g u l a r

368

CRACK

F O R M A T I O N I N

ICE

3.'-

1 u K I N G CREEP

Val.

3 ,

?;a.

6

s p e c i m e n s exceeded a b o a t 4 k g / c r n 2 . They w e r e iong aild n a r r o w , with a r a t i o of ienz'ih 'io

width g r e a t e r than 3: 1 ( 3 ) . The plane of e a c h c r a c k tended t o b e p a r a l l e i t o t h e a p p l i e d conz-

p r c s s i v e s t r e s s and t o h a v e i t s long d i r e c t i o n in the long d i r e c t i o n of t h e g r a i n s . The c r a c k s tended to b e t r a n s c r y s t a l l i n e , but g r a i n boundary and t r i p l e point c r a c k s w e r e a l s o o b s e r v e d

( 3 ) . In c o n t r a s t with craclc f o r m a t i o n in the alloy t h e f o r m a t i o n of a c r a c k i n i c e had t h e c h a r a c t e r i s t i c s of a l o c a l b r i t t l e event. Once a craclc had f o r m e d i t did not a p p e a r t o i n c r e a s e

in s i z e with s u b s e q u e n t d e f o r m a t i o n .

The c r a c k s could e a s i l y be s e e n a s they f o r m e d b y using s u i t a b l e light. O b s e r v a t i o n s

f o r c r e e p s t r a i n l e s s than 0. 1 p e r c e n t showed t h a t the d i s t r i b u t i o n of c r a c k s a c c o r d i n g t o

c r a c k width had a m a x i m u n in t h e r a n g e 0. 1 to 0. 3 m m , and t h a t i t d r o p p e d oif siia-rpiy in the

. r a n g e 0. 05 to 0. 1 nzrn. As c r a c k s of t h i s width w e r e e a s i l y o b s e r v e d , it is considcrec! i h s i t h e

d r o p - o f f was r e a l , aild t h a t p r a c t i c a i l y n o c r a c k s f o r r n e d with widths l e s s than G. i mr2. Ob-

.

. s e r v a t i u n s on craclc deilsity, t h e r e f o r e , a r c c o n s i d e r e r l to S c a t r u e measure of tiic cracKing a c t i v i t y t h a t occ-orrcd.

R e s u l t s

F i g u r e 1 shows t h e dependence of craclc d e n s i t y on s t r a i n sbserveci f o r c o m p r e s s i v e

s t r e s s e s of 8 and 12 k g / c m 2 and t e m p e r a t u r e of -10" C. F i g u r e 2 g i v e s t h e a s s o c i a t e d c r e e p

c u r v e s . E a c h c u r v e i s t h e a v e r a g e of s i x t e s t s . The c r a c k r e c o r d w a s obtained by counting

a t a p p r o p r i a t e t i m e s t h e n u m b e r of c r a c k s t h a t had f o r m e d s i n c e t h e l a s t o b s e r v a t i o n .

D i s c u s s i o n

T h e s i m i l a r i t y i n t h e s h a p e of t h e craclc d e n s i t y c u r v e s a n d a s s o c i a t e a c r e e p c u r v e s i o r

i c e and t h e alloy i s q u i t e s t r i k i n g , even though the mode of c r a c k f o r r a t i o n i s different l o r the

two m a t e r i a l s . T h e r e i s a m u c h s t r o n g e r dependence of c r a c k d e n s i t y on s t r e s s f o r i c e , how-

e v e r , and t h e c o m p a r a b l e c r a c k i n g a c t i v i t y o c c u r s within a s t r a i n a t least i n orcler c.T rrragx- tude s m a l l e r . The width of t h e c r a c k s f o r m e d in the i c e i s a l s o ar, o r d e r of i - n a g n i t ~ d e l a r g e r

t h a n t h e width of 'hose f o r m e d in t h e aiioy, and :t d o e s i>oi i n c r e a s e wi:LI d e i o r r n a i o n .

T h e d i f f e r e n c e b e t w e e n the s t r e s s a n d s t r a i n dependence oi t h e c r a c k deiisity, sac: in

. .

t h e c r a c k s i z e i s p r o b a b l y due t o t h e d i i f e r e n c e in n ~ o C c vi cri:.c ii;.;ation anti ;i-ophcaiion,

.

.

O b s e r v a t i o n s on t h e i c e indicated t h a t c r a c ~ s tend t o Soi-i-&; in or a d j a c e ~ i t t o g r a i n s wit:? t h e i r b a s a l p l a n e s a p p r o x i m a t e l y p a r a l l e i o r p e r p e n d i c u l a r i o t:Le applied i c h d ( 3 j . T!?ese si.s "hard"

o r i e n t a t i o n s f o r a m a t e r i a i with hexagonal s y m m e t r y s u c h a s i c e , and s t r e s s concenzi-atlons

of t h e type a s s o c i a t e d with d i s l o c a t i o n p i l e - u p s c a n b e expected. The c l e a v a g e type c r a c k i n g

a c t i v i t y o b s e r v e d i n i c e i s c o n s i s t e n r with m o d e l s of c r a c k n u c l e a t i o n of t h e type d i s c u s s e d by

C o t t r e l ( 4 ) a n d S m i t h ( 5 ) , t h e low s u r f a c e e n e r g y of I c e ( a b o u t 100 e r g s / c m 2 j , t h e l a r g e g r a i n

V o l . 3,

No. 6

CRACK FORMATION

I N

ICE DURIKG CREEP

0 . 0 I i l i i !~ i l l

/

T e m p e r a t u r e

.

-10' C

I

C R E E P S T R A I N .

+

F I G . 1 TIIAI. M I N U T I S F I G . 2 D e p e n d e n c e of c r a c k d e n s i t y on c r e e p D e p e n d e n c e of c r e e p s t r a i n on t i m e . s t r a i n . O n e of t h e i n t e r e 9 t i n g f e a t u r e s of t h e o b s e r v a t i o n s i s t h e c o r r e s p o n d e n c e b e t w e e n c r a c k - ing a c t i v i t y a n d c r e e p b e h a v i o r f o r t h e i c e a n d t h e a l l o y . Both s e t s of e x p e r i m e n t s s h o w a n a c c e l e r a t i n g r a t e of s t r a i n d u r i n g t h e p e r i o d of maximum c r a c k i n g a c t i v i t y a t t h e l o w e r s t r e s s . F o r t h e a l l o y , t h i s i n c r e a s e c a n b e a t t r i b u t e d t o a r e d u c t i o n i n c r o s s - s e c t i o n a l a r e a owing t a c r a c k f o r m a t i o n a n d s u b s e q u e n t g r o w t h . T h i s w a s n o t s o f o r i c e , h o w e v e r , a s t h e c r a c k s w e r e f o r m e d i n c o m p r e s s i v e c r e e p . I t is c o n s i d e r e d t h a t t h e i o r m a t i o n of a c r a c k r e l i e v e d l o c a l c o n s t r a i n t s a n d a l l o w e d t h e r e g i o n t o d e i o r m m o r e r e a d i l y (i. e . c r a c k i o r m a t i o n whs a f o r m of w o r k softening). It s h o u i d b e n o t e d t h a t t h e p e r i o d of maxin:um c r a c k i n g ~ c t i v l t y :or t h e i c e , when t h e s t r e s s w a s 8 k g / c m 2 , o c c u r r e d d u r i n g t h e g s i m a r y c r e e p s t a k e . T h e l o w c r a c k i n g a c t i v i t y f o r s t r a i n g r e a t e r t h a n a b o u t 0. 8 p e r c e n t w a s a s s o c i a t e d wit^ s e c o n d a r y c r e e p . F a r b o t h s e t s or' e x p e r i m e n t s t h e r a t e or' c r a c k f o r m a t i o n a t t h e h i g h e r s t r e s s d e c r e a s e d w i t h s t r a i n a f t e r a n i n i t i a l m a x i m u m , b u t a l w a y s r e m a i n e d significalit. T h i s t y p e of c r a c k i n g a c t i v i t y w a s a s s o c i a t e d with t h e c o n d i t i o n of d i r e c t t r a n s i t i o n f r o m p r i i n a r y t o t e r t i a r y c r e e p , ivith n o i n t e r v e n i n g s e c o n d a r y s t a g e . One of t h e f a c t o r s p r o b a b l y c o m m o n t o both s e t s of e x ? e r i m e n t s w a s t h a t c r a c k n u c i e -

a t i o n w a s a r a n d o m p r o c e s s d u r i n g t h e f i r s t parz. of t h e d e f o r m a t i o n . Observations now being c a r r i e d oqt b y t h e aliihor i n d i c a t c t n a t c r a c k d i s t r l b u t l o n i n i c e 1s r a c d o m when i r a c k l n g a c t i v l -

370

CRACK FOkMATIO?;

IK ICE DURISG

C"nl;%P

Voi. 3 ,

3 0 .

6

with a l o a d of 12 k g / c m 2 , c r a c k d i s t r i b u t i o n w a s r a n d o m Lor s t r a i n l e s s tnan ahcu: 0. 5 > e - -

.

I c e n t a n d t e n d e d t o b e c o m e non-randolm t h e r e a f t e r . At t h i s s t a g e r h e r e w a s a t e n d e n c y i o r t h e c r a c k s t o o c c u r i n z o n e s p a r a i l e l t o t h e p l a n e s of m a x i m u m s h e a r . It w a s c l e a r t h a t t h e d e - v e l o p m e n t of t h e s e f a i l u r e p l a n e s w a s a s s o c i a t e d w i t h t h e o c c u r r e n c e of t e r t i a r y c r e e p . C r a c k f o r m a t i o n h a d g r a d u a l l y m o d i f i e d t h e s t r u c t u r e of t h e i c e u n t i l i t w a s n o l o n g e r a b l e t o s u s t a i n t h e a p p l i e d l o a d . O b s e r v a t i o n s on t h e s t r e s s , t i m e , s t r a i n a n d t e m p e r a t u r e d c p e i l d c n c e oi t h e c r a c k i n g a c t i v i t y i n i c e a r e t o b e pubiisheci. A c k n o w l e d g e m e n t T h e a u t h o r w i s h e s t o e x p r e s s h i s a p p r e c i a t i o n t o h i s c o l l e a g u e , D r . A. S. K r a u s z , f o r h i s h e l p f u l d i s c u s s i o n s d u r i n g t h e p r e p a r a t i o n of t h i s l e t t e r . T h i s i s a c o n t r i b u t i o n f r o m t h e D i v i s i o n of B u i l d i n g R e s e a r c h , N a t i o n a i R e s e a r c - h C o u n c i l of C a n a d a , a n d i s p u b l i s h e d w i t h t h e a p p r o v a l of t h e D l r e c t o r o i t h e Division.

(I)

J. A. W i l l i a m s , S c r i p t a M e t a l l , , 2, 273 (1968). ( 2 ) L. W. Gold, C a n .

J.

P h y s . , 43, 1414, ( 1 9 6 5 ) . ( 3 ) L.W. Gold, Can. J. P h y s . , 44, 2757, (1966). ( 4 ) A. H. C o t t r e l l , P r o c . , F i r s t T e w k s b u r y S y m p . on F r a c t u r e , M e l b o u r n e U n l v . , 1 - 2 7 , 15 63. ( 5 ) E. Smith, A c t a M e t a l l . , 14, 985, ( 1 9 6 6 ) .