Issue34

K.L. Yuan et alii, Frattura ed Integrità Strutturale, 34 (2015) 476-486; DOI: 10.3221/IGF-ESIS.34.53 483 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 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 t 1 [1.348 0.397 ln( )] S T K Q f       (6) 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 1/2 3/2 t n 1 ( ) [( ) ( ) ] / 2 2 / 2 2 2 x K r r y y r y r       (7) F