Elastic–plastic deformation and residual stresses in helical springs

Abstract

Purpose

The purpose of this paper is to develop the method for the calculation of residual stress and enduring deformation of helical springs.

Design/methodology/approach

For helical compression or tension springs, a spring wire is twisted. In the first case, the torsion of the straight bar with the circular cross-section is investigated, and, for derivations, the StVenant’s hypothesis is presumed. Analogously, for the torsion helical springs, the wire is in the state of flexure. In the second case, the bending of the straight bar with the rectangular cross-section is studied and the method is based on Bernoulli’s hypothesis.

Findings

For both cases (compression/tension of torsion helical spring), the closed-form solutions are based on the hyperbolic and on the Ramberg–Osgood material laws.

Research limitations/implications

The method is based on the deformational formulation of plasticity theory and common kinematic hypotheses.

Practical implications

The advantage of the discovered closed-form solutions is their applicability for the calculation of spring length or spring twist angle loss and residual stresses on the wire after the pre-setting process without the necessity of complicated finite-element solutions.

Social implications

The formulas are intended for practical evaluation of necessary parameters for optimal pre-setting processes of compression and torsion helical springs.

Originality/value

Because of the discovery of closed-form solutions and analytical formulas for the pre-setting process, the numerical analysis is not necessary. The analytical solution facilitates the proper evaluation of the plastic flow in torsion, compression and bending springs and improves the manufacturing of industrial components.

Citation

Kobelev, V. (2020), "Elastic–plastic deformation and residual stresses in helical springs", Multidiscipline Modeling in Materials and Structures, Vol. 16 No. 3, pp. 448-475. https://doi.org/10.1108/MMMS-04-2019-0085