Issue 44

X.-P. Zhou et alii, Frattura ed Integrità Strutturale, 44 (2018) 64-81; DOI: 10.3221/IGF-ESIS.44.06



 iu f t (2 ) 

t



where

,  1

is the maximum principal stress,  2

is the intermediate principal stress,  3

is the minimum

c

2 ( )

principal stress, the compressive stresses are defined to be positive in this paper.

1 

1 

2 



3 

Figure 4 : Wing crack distribution zone

Eq.(18) can be rewritten as :

4

2







  C

C

C

cos

cos

0

(19)

1

2

3

where



2 2

4

   (









C C

) (

1)sin

 

1

1 3

















 

 

2

2

2

2

2

2





 sin 2 +2c  c

 

 +1 +2



 sin cos 

















os

    

1 3

2

3

1

2

3





2

2 2





   c

 

2

2

2

   



 sin cos



 

  



C

cos

si

n

3

2

3

3

2



From Eq. (19), the cosine of  can be written as

2

2

2

 1







 2

cos

cos

cos

(20)

where

      

   C C C C C C C C C C 2 2 2 1 3 1 2 2 2 1 3 4 2 4 2   

2

 1



cos

2



 2

cos

1

From Eq.(20), supposing  

   2 1

, the following equation can be written

 cos cos( 



  

 2 ) cos cos

 1



 2 sin sin

 1

(21)

2 1

70