Elastic-plastic work-hardening deformation under combined bending and torsion and residual stresses in helical springs

Residual stress plays an important role with respect to the operating performance of helical springs. Its effect on the different properties of a material (fatigue, fracture, corrosion, friction, wear, etc.) can be considerable. In the modern design of springs, residual stress has therefore to be taken into account. In the present article, the mathe-matical theory of residual stresses and strains in helical springs is introduced. The theory of residual stresses in helical springs allows calculating the stresses on all steps of manufacturing process, particularly during the coiling and preset-ting.