REDUCTION OF SPRINGBACK AND RESIDUAL-STRESSES DURING WINDING OF A HELICAL SPRING

Wire exhibits considerable torsional springback after cold forming, by winding into a helical spring. This springback can be reduced by the application of a tensile pull during the winding process. The applied tensile load reduces the moment required to form a plastic hinge. Removal of the tensile pull after winding further reduces the constrained moment in the cross section and resultant springback. More importantly, the reduction of springback can be related to a reduction of residual stresses in the wire.