Residual stress distributions around plain and cold expanded fastener holes in aluminium alloy 7050–T76 have been measured using the X-ray diffraction sin2Ψ method. Both radial and hoop stresses have been measured as a function of distance from the edge of the hole on the mandrel inlet and outlet faces. The effect of fatigue loading on the residual stress distribution around cold expanded holes has been investigated and is discussed in relation to measured fatigue endurance. The effect of the X-ray beam size on the resolution of the technique in the vicinity of the hole has been studied and life predictions incorporating the measured residual stresses have been correlated with fatigue endurance.
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