Issue 34

Y. Sumi, Frattura ed Integrità Strutturale, 34 (2015) 43-59; DOI: 10.3221/IGF-ESIS.34.04

Figure 5 : Double-cantilever beam specimen [12, 24].

Figure 6 : Stability parameters for a double-cantilever beam specimen [12, 24].

Figure 7 : Crack paths observed in double-cantilever beam specimens [12, 24].

Energy Consideration of Crack Paths for Inhomogeneous Fracture Toughness Following Bilby and Cardew [20], the elastic energy release rate G due to the slightly kinked and curved crack extension can be calculated by Eq.(24) for a homogeneous material, where K I and K II , are the stress intensity factors at the extended crack tip. Substitution of Eqs. (13) and (14) into Eq. (24) leads to an expansion of G in an ascending order of h [7], and it is given by,     0 I II ; ,  O G G k k h    (48)

0 G is obtained as

where

   

    

  

  

 

  

2 

2 

8 

1  





2

2

; ,  G k k 









1   

k

k k

k

1

2

(49)

0

I

II

I

I II

II



2

2

0 G with respect to   are calculated as

The first and second variations of

8 



2 1 









2





k k 







G

k k

2

(50)



0

I

II

I II



51