Effects of the toe shape of the flash on stress concentration factor in friction welded joints

Summary

The authors have previously reported that the fatigue strength of friction welded joints with a flash is markedly affected by the toe shape of the flash caused by friction welding conditions. Accordingly, in this report, the effects of the toe shape of the flash upon the stress concentration factor α of friction welded joints were examined by means of the rotating bending fatigue test. Simulated friction welded joint specimens were employed in the experiments; the stress concentration factor was measured using the copper electro-plating stress measuring technique. The toe shape of the flash was characterised by four factors which were the toe radius r, the toe angle θ, the root height h and the toe width b.

The results obtained are as follows:

1.	The effects of r upon α were marked when r was small; however, for comparatively greater values of r, the effects were hardly detectable.
2.	The effects of θ upon α increased with increasing θ; however, this tendency was hardly noticeable for greater values of r.
3.	The effects of h upon α were marked when h was less than 0.9 mm (D/d = 1.15); however, the effects of h were hardly noticeable for greater values of r.
4.	The minimal effects of b upon α were noted in the case of comparatively small values of r; however, the effects were hardly noticeable for greater values of r.
5.	r, θ, h and b affected α whilst inter-reacting with one another.