抄録
A smoothing of fillet toe results in an improvement of its fatigue strength, but at the same time it seems to develop its liability to root failure occurrence from root defect. The purpose of this study is to investigate the relation between root failure and stress concentration and to find the control condition of root failure on the fatigue of a toe-smoothed non-load-carrying type cruciform fillet welded joint.
In fatigue tests, size of fillet (s) are 5-23 mm. After welding, toe are TIG-dressed and circular holes are made at the root of fillet as defect by electrical discharge machining. Diameter of circular holes (φd) are 0.3 and 0.6 mm. The maximum stress of fatigue cycle was set at yield stress of the material (S=σmax-σmin, σmax=σY).
As the results of finite element analyses and fatigue tests, it was found that root failure could be prevented in the ratio of about s/d≥53-33 from a point of view of stress concentration factor (in practice: s/d≥36-13) in d=0.3-0.6mm, but fatigue strength decreased on excess size of fillet on the contrary.
