Issue 46

W. Song et alii, Frattura ed Integrità Strutturale, 46 (2018) 94-101; DOI: 10.3221/IGF-ESIS.46.10

N root

It should be noted that the K  stands for the simplified form of mode I notch stress intensity factor. In order to calculate the NSIFs and SED by EFM method, Meneghetti [20] connects the peak stress with these results to obtain closed-form expression of NSIF and averaged SED values for different modes, which are written as follows:

N

K



1





K

1.38

(7)

FE

1 d   1







 

, 0, 

peak

N

K



2





K

(8)

3.38

FE

2 d   1

r 





 

, 0, 

peak







, 0, r peak    

where d is the mean finite element size.

and

are the stress results under polar coordination from

, 0, peak   

N

i K values can be obtained from numerical results using very refined FE mesh patterns. Finally, SED

FE analysis. The

values can be deduced by the PSM equation, which is shown as follows:

    

    

2

2



1 



2 



   

   

   

1

1

2 

0   d     R

0   d     R



e

e

1





2

1 W K 

2







 

 





 



 

K

(9)

 

, 0, 

 

, 0, 

FE

peak

FE r

peak

, eq peak

E

E

E

2

 

The equivalent peak stress can be obtained from the following equation:

2

2

2    f

2

, eq peak    c 

 



r 

f

(

)

(10)

 

, 0, 

 

, 0, 

w w

peak w

peak

1

2

1 w f and

2 w f are induced according to element size and the corresponding control volume for SED evaluation. It

where









and

for as-welded joints can be simplified by a correction

should be noted that the relationship between

peak

, eq peak

f , which is shown as follows:

parameter w

peak     



(11)

f

w

, eq peak

For the notch opening angle 2 135    and the average FE size

0.5 d mm  , the parameter w

f is obtained as 1.064. If

the SED values are determined from NSIF analytical solutions, the PSM values can be calculated from Eqn. 9.

Weld Root

Rc

Weld toe

Rc

t

Tension

2a

θ

h

2α

Bending

L

Figure 1 : Geometry of cruciform welded joints and corresponding SED geometry illustration.

96