This paper describes about the experimental study on the shear fatigue strength of the fillet weld of welded beams, such as connecting web and flange. Though these problems, in our opinion are important in practice as well as in design, we could not find any papers which clarified these problems.
The object of this experiment is, at first, in comparision of shear fatigue strength of fillet welds, automatic and manual. Next, it is in clarifying the fatigue strength of fillet weld, which is simply under pure shearing stress or combined stresses, shearing and tensile or compressive.
Moreover, shear fatigue strength of fillet welds were compared with I section specimen and box section specimen.
Fatigue test was made with 4 type specimens whose moments of inertia were nearly equal and nominal throat of fillet welds were, also, nearly equal ; 6mm.
The plates used were SM41 & SM41W.
The Results obtained are as follows ;
(1) We succeed at obtaining fatigue fracture by pure shear with special specimen whose she-aring stress distribution along the welding direction was uniform.
(2) The, fatigue strength of fillet joint welded by automatic method was almost the same as that of manual weld referred to the nominal throat stress. However, referred to the actual throat stress, manual weld was about 30% stronger than the automatic weld.
(3) It was found that the axial stress did not at all affect the shear fatigue strength when the fillet joint under combined stresses. But it must be considered that there is stress concentra-tion as to the shearing stress on the throat section by the gap in the root part, but no stress con-centration as to the axial stress.
(4) I section specimen was about 30 % stronger than box section in fatigue strength at N= 2×10
6 cycles as to the nominal stress.
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