Effect of plastic deformation on torsional fatigue properties of a low carbon steel

This paper is aimed to investigate the effect of roller working on the torsional fatigue properties of a typical low carbon steel referring by the resutls of FEM analysis. Three types of specimens had been prepared with plastic deformation value of 0, 0.5 and 1.0mm, respectively. The main results obtained in this study are as follows: (1) The torsional fatigue strength of roller-worked specimen with 1.0mm plastic deformation is increased more than twice of that of non-roller worked specimens. (2) Surface hardness of roller worked specimen is much higher than that of the non-roller worked one, and compressed and elongated structure is formed at the notch bottom of the specimen. (3) Crack length along the axial direction of roller worked specimens is longer than that of the non-roller worked specimen, and plural cracks initiated and propagated in the roller worked specimens. (4) The residual stress distribution at the specimen's notch bottom was analysed using FEM analysis and it is verified the same tendency as the experimental results.