High cycle fatigue strength of butt welded joints of small diameter pipes

Abstract Fillet welds are usually used for joints of small pipelines with 2-inch nominal outer diameter or smaller. The fillet welded joints might not be strong enough to withstand the high cycle fatigue produced by steady-state vibrations, because they have inherent crack-like discontinuities in the root portion. The fatigue strength of butt welded joints is believed to be higher than that of fillet welded joints, so that it is desirable to use butt welded joints for small pipelines under steady-state vibrations. However, there are no available data on high cycle fatigue strength of small diameter piping butt welded joints. This paper presents new data on high cycle fatigue strength of butt welded joints in small diameter pipes and development of their fatigue strength reduction factors for design use.