Residual Stress Creep Relaxation Around Cold Expanded Holes in an Aluminium Alloy

Abstract

Residual stress distributions were measured in aluminum-alloy 2650 disks after cold expansion and after exposure to creep at 150°C for various times. Strains measured as a result of boring out the hole after cold expansion were found to exhibit significant angular variations around the hole. However, after exposure to 150°C residual strains and stresses showed less angular variation. To take account of the angular variation, the Garcia-Sachs technique for measuring residual stresses was employed. Surface residual stresses on the entrance and exit faces of the disks were measured using the x-ray method. The most significant relaxation of the residual stresses occurred within the first 100 h. Two simple models were used to predict residual stress relaxation, one using a uniaxial creep relaxation model and a second using tensile and isochronous stress-strain curves. A good comparison between predictions and experiments was observed.