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K.L. Yuan et alii, Frattura ed Integrità Strutturale, 34 (2015) 476-486; DOI: 10.3221/IGF-ESIS.34.53

is seen, however, it has been found that the measured surface stress by X-ray method is very sensitive to the location of measurement spot [25].

a) b) Figure 11 : Transverse residual stress distributions and plastic deformation at weld toe; (a) as-weld, (b) UIT with η=40%.

Figure 12 : Distribution of transverse residual stress of as-weld and UIT specimens in the depth direction, and comparison with experimental results [20].

F ATIGUE LIFE PREDICTION

F

or accurate fatigue life prediction of a weld joint, it is necessary to consider the stress concentration and residual stress near the weld toe. According to the measurements [20], the weld toe radius r of as-weld and UIT specimen are assumed as 0.25 mm and 2 mm, respectively. The stress concentration factor, K t , of the weld toe is estimated by the following formula proposed by Tsuji [26]

0.467 Q f 

1 [1.348 0.397 ln( )] S T   



K

(6)



t

where

( / ) /[2.8( / ) 2] Q l r W T  

2 [1 exp( 0.9 / 2 )]/[1 exp( 0.9 / 2 ( )] f W l W l          

T is the main-plate thickness of 16mm, l is the leg length of 7mm, θ is the flank angle of 45°, and W=S=T+2l . Under tension load, the stress distribution near the weld toe is calculated by

t n 

K

r

r

1 2

1/2

3/2 ) ]

x 





( ) y

[(

)

(

(7)

y r 

y r 

/ 2

/ 2

2 2

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