Weld tool travel speed effects on fatigue life of friction stir welds in 5083 aluminium

This paper reports the results of a study into the influence of weld tool travel speed (in the range 80–200 mm/min) on the occurrence of ‘onion-skin’ forging-type defects (similar to the root defects known as ‘kissing bonds’) in single pass friction stir (SP FS) welds, and on the effect of these defects on fatigue crack initiation and overall life. Results indicate that such defects are generally not associated with fatigue crack initiation, but may act to reduce fatigue life by providing easy linking paths between two fatigue cracks. It is likely that their influence on fracture toughness of SP FS welds would be higher, as they occur more readily when growth rates and levels of plastic deformation are higher.