Alleviation of quenching residual stresses by cold working the necks of seamless 6351 aluminium alloy thick-walled gas cylinders

Abstract

The application of a compressive axial load to the apex of a gas cylinder neck results in the generation of Poisson-induced tensile circumferential stresses at the bore. As the compressive axial load is increased in magnitude, the stress distribution in the gas cylinder neck increases until finally yielding occurs at a specific location on the bore. Provided that the maximum compressive axial load is of sufficient magnitude, significant compressive residual circumferential stresses are generated at the bore. The purpose of this remedial action is to alleviate residual stresses that are introduced into the gas cylinder neck during the quenching stage of the manufacturing process. A destructive technique has been employed to determine quenching residual stresses in the neck of one production gas cylinder neck. This residual stress distribution is compared with one obtained by employing the destructive technique on a gas cylinder that has been cold worked by axial loading. Results indicate that tensile quenching residual circumferential stresses at the bore can be favourably modified resulting in compressive circumferential residual circumferential stresses at the bore.