ばり付鋼材摩擦圧接継手の疲れ強さに及ぼす圧接条件の影響

抄録

The effect of flash on fatigue strength of friction welded joints are examined by means of rotating bending fatigue test, using as-welded joint specimens of hot and cold drawn mild steel round bar.
The following experimental results were obtained ;
(1) Fatigue strength of hot and cold drawn steel decreased with the increase of upset pressure.
(2) In welded joints with flash, fatigue cracks were initiated at toe of flash.
(3) Effect of upset pressure on fatigue strength was remarkable, but effect of friction pressure and total loss were slightly.
(4) Toe radius of flash decreased with the increase of upset pressure and toe angle increased with the increase of this pressure. Therefore, it was considered that the main cause of the decrease of fatigue strength was stress concentration of toe of flash.
(5) In the case of hot drawn steel, fatigue strength of the joint under any welding condition was recovered up to that of base metal, when flash was removed. In the case of cold drawn steel, however, that was not recovered, even when flash was removed.
(6) Fatigue strength of cold drawn steel joints was remarkably decreased, when fatigue failure occurred in duplicate zone of stress concentration and softening. Therefore, this material required sufficient care, when friction welding condition was selected.