Surface residual stresses induced by torsional plastic pre-setting of solid spring bar

Abstract

Residual stresses could be induced by the plastic torsion loading of a solid round bar. This article deals with the residual stresses generated at the surface during the process of plastic pre-setting. Residual stresses were measured on the surface of a specimen by x-ray diffraction for different angles of subsequent plastic pre-setting. In addition, the residual stresses were calculated using analytical and numerical modelling by finite element methods. The analytical approach was based on the torsional characteristic, τ–γ, of the material and tension test results. It has been found that the direction of cold rolling on the surface has a significant influence on residual stresses, as it is reflected in the initial stress state. A good agreement between analytical modelling, finite element analysis, and experimental residual stress measurement was obtained.