Effects of finishes of weld toe and mean stresses on bending fatigue strength of transverse fillet welded joints were investigated. Variation of radius and position of weld toe and flank angle along the weld bead were statistically analyzed.
The results are summarized as follows
i) Fatigue strength of SM58Q (MIG⋅as-welded), SM58Q (TIG finished), HT80 (ground), HT80 (ground+peended) increased to 114%, 130%, 120% and 214% at Nf=10
6 under minimum stress σmin=0 compared with that of the corresponding low hydrogen electrode·as-welded specimens. However, the effect of peening vanished in the low cycle region under σmin=0 as well as in the entire region under high mean stress.
ii) Statistical analysis of the values of curvature (1/ρ, ρ : radius of weld toe) along the weld bead were performed for normal, logarithmic normal, Weibull and Gumbel distribution. It was found that the curvature of weld toe in all cases of weld finishes obeys the Gumbel distribution.
iii) Fatigue strength reduction factor Kf was calculated using equivalent stress concentration factor Kreq which was derived from averaging the scatter of stress concentration factor Kt (caused by the variation of ρ) and the calculated Kf values were in good agreement with the test results.
iv) Fatigue strength under high mean stresses in the neighborhood of yield point ay decreased little compared with that under σmin=0 except for the peened specimen.
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