Crack Paths 2012

_

_ 1 ,_’ ’

2t—1'1—T2 ndO'(T1)dO'(T2)

Wr(t)—6'(t)0'(t)

20000) g l D,[ T J 871

812 drldcz

(2)

0

Negative terms on equation (2) represent the dissipated energy on the viscoelastic

material under loading 6(t). Total energy communicateby loading 6(t) to viscoelastic

material is:

85(1)

W. 0) - [00)

d1:

61'

(3)

Time to failure under constant stress (strain) ratio is espressed according different

criteria [10]:

D Reiner—WeissenberCgriterion (R—W),with: W, (t) S * 00',2 : 2

ti :( (n+l)(n+2) 2 )/”(glj/”(1_1)1/n

To

2(n+2)+(2—2”+ )

D1

7

(4)

M a x i m uWmo r kStress Criterion ( M W S ) ,with: W, (t) S %0',2:

t

1,

D /” 1

1/n

i 20+”) " g1 (71)

To

1

(5)

M a x i m uSntrain Criterion (MS), with: 8( t) _

/"

/n

l

D 1

( f ): (1+ n)l/n

( F—l)

To

1

i7

(6)

A n dthe ModifiedReiner-WeissemberCgriterion ( M R - W ) ,with: W, _<(D0/2) 0'1 (Xt):

tf _ ( ln+1]]n+2] ) / n ( B Q ) 1 /1n_(1)]/n

% _ 2(n+2)+(2—2”+2)

D1

0’?

(7)

410