Friction stir welds in aluminium: Design S‐N curves from statistical analysis of literature data

Abstract

Appropriate S‐N fatigue design curves for friction stir welded joints in aluminium alloys are currently not specified in design codes and standards. The present paper is intended to assist in enabling standardised fatigue design for such joints, through a comprehensive statistical analysis of more than 500 individual sets of data gathered from published literature. These data are used to establish the usual design fatigue curves for welds that give a 97.7% survival probability with 95% confidence. Experimental fatigue data represent defect‐free butt joints and include both flat plate and tubular joints between similar aluminium alloys (across the range of 2xxx, 5xxx, 6xxx, and 7xxx series). Weld conditions include as‐welded, machined, and postweld heat treated under constant amplitude cyclic loading at various stress ratios in the range from R = −1 to 0.5. A systematic comparison is presented by categorising the data according to the alloy type, temper condition, postweld heat treatment, and stress ratio and the correlation with the S‐N design curves from Eurocode 9 is also considered. The fatigue curves presented in this paper will serve as a useful guideline for engineers involved in design of friction stir aluminium joints subjected to in‐service fatigue loading.

Effect of Weld Length on Strength, Fatigue Behaviour and Microstructure of Intersecting Stitch-Friction Stir Welded AA 6016-T4 Sheets

“…This trend is also indicated by the evaluation of fatigue strength. The inverse slope values between 6 and 7 are in a good accordance with literature for friction stir welded specimens in butt configuration [ 34 ]. The R-squared value indicates a good fitting of the regression line for all stitch welds and the base material, deviating from this are the specimens of the continuous welds.…”

Fatigue strength of aluminium welded joints by a non-local approach

“…Otherwise, for instance in friction stir welding, when the geometrical notch effect is reduced, the ageing beneficial is no longer negligible and a separate investigation among different aluminium alloys is more appropriate [28,29].…”

Fatigue properties of AA6060‐T6 butt welds made by hybrid metal extrusion & bonding

“…7,8 Friction stir (FS) welded aluminium joints, on the other hand typically demonstrate superior fatigue properties compared to conventional fusion welds. 1,[9][10][11][12][13][14] Therefore, it is widely accepted that many of the negative effects of welding in the context of engineering design are reduced using solid state joining. 15 Historically, the potential for improved mechanical properties and flexibility in handling different aluminium base metal (BM) combinations and plate thicknesses was the main motivation for the development of the FS welding (FSW) process since its early launch back in 1991.…”