A COMPARISON OF POTENTIAL METHODS FOR THE ALLEVIATION OF RESIDUAL-STRESSES IN THE NECKS OF ALUMINUM-ALLOY THICK-WALLED GAS-CYLINDERS

Tensile circumferential residual stresses are introduced into seamless 6351 aluminium alloy gas cylinder necks at the bore during the heat t reatment stage of the manufacturing process. To ascertain the feasibil ity of a proposed corrective procedure (selective removal of material from the gas cylinder neck) finite element analyses that modelled mate rial removal were undertaken. Results indicate that no significant ben efit was gained from the partial removal of bore material. However, re moving the inelastically deformed outer surface material is likely to provide the greatest benefit of the four options considered. The mater ial removal option was then compared with an investigation into cold w orking the gas cylinder neck to favourably modify the quenching residu al stresses. Experimental results have indicated that the application of an axially applied compressive load to the gas cylinder neck, induc ing bore yielding, favourably modifies the quenching residual stresses . This alternative of cold working the gas cylinder neck appears to be a possible method of favourably modifying the quenching residual stre ss.