*3.3. Residual Stresses*

Figure 10 shows the residual stresses determined by neutron diffraction in the 6005A-T6 aluminium alloy single-sided and double-sided FSWs. In both specimens, the longitudinal and transverse residual stress distributions agreed with the typical 'M' shape pattern of FSW aluminum alloys [6]. The normal residual stresses were observed with little variations, especially on L3 line of the single-sided FSW which remained near to a value of zero. Notably, the average uncertainty of the obtained stresses is approximately ±13 MPa in these measurements.

**Figure 10.** Residual stresses on L1 (**a**), L2 (**b**), L3 (**c**) in the single-sided FSW and L1 (**d**), L2 (**e**), L3 (**f**) in the double-sided FSW.
