Page 59 - Biaxial Multiaxial Fatigue and Fracture

44 E LABESSE-JIED ET AL.

hot-spot stress is obtained by the linear extrapolation of the stress distribution to the weld toe
(Fig. 2). The location of this considered stress is due to the fact that it is generally the critical
point of the weld, i.e. the crack initiation site. The structural stress is the measured or Finite
Element calculated stress obtained at a given distance afar from the weld toe. Because of the
stress concentration generated by the geometrical discontinuity at the weld toe and directly
related to the transition radius, this structural stress is in general higher than the hot-spot one
and leads to a more conservative dimensioning.

4

le7
IogN

Fig. 1. Wohler S-N curves for classified weld geometries (from [2])

loading mode)
II, 0, Stress<oncenvation
fador : K,= 3
(strain gauge or FE)
1 linear
i,
weld-toe
extrapolatm
I -w I -L i
1
weld angle e
~ l d - t ~ ~
d I (thickness. gauge length) - 1 lo 2 mm
f
Fig. 2. Conventional design stresses in a weld joint (from [1,3])