Abstract
Recently, friction welded butt joint has come into wider use for many mechanical structural elements, e.g. small scale crank shaft, etc. However, there exists some uneasiness in the practical use of this type of joint because of lack of strength data under service load or fatigue load conditions.
So, the authors planned to conduct a systematic study on fatigue behavior of this type of joint and have been carrying out a series of experiments by using some sorts of joint specimens composed of similar metallic material.
As a part of this study, rotating bending fatigue tests were carried out to investigate the fatigue strength behavior of SUS 304/SUS 304 friction welded butt joint specimens. The results showed that the fatigue strength of the joint specimen was much lower than that of the base material specimen especially in the stress cycles range exceeding the critical number of stress cycles for the base material specimen. Furthermore, detailed observations on the fatigue fractured surface were done to give valid explanation to the characteristic strength behavior of the joint specimen revealed in this experiment.
It is concluded that the lowering trend in fatigue strength of SUS 304/SUS 304 joint specimens depends on the metallurgical feature of the friction welded interface, in other words, that the boundary layer of fiber flow direction existing around the interface gives a detrimental effect on the fatigue strength of this type of joint.
