Influence of Emergency Load on the Residual Strain Value of Torsion ShaftsInfluence of Emergency Load on the Residual Strain Value of Torsion Shafts

Abstract

Scope of the research: when operating the torsion shaft in alternating mode the emergency loads may occur, upon which the resulting stresses will exceed the yield strength of steel. In this case, the Bauschinger effect is exhibited, consisting in the reduction of the plastic deformation resistance of steel after preliminary plastic deformation of opposite sign. The studies of the Bauschinger effect aspects at the alternating torsion are practically not available. An effective way to improve elastic properties of steel is stress tempering. The purpose of this work has been to investigate the influence of the deformation value and the direction at stress tempering specimens of hardened medium-carbon Cr-Ni-Mo steel on the residual strain under alternating emergency load. Main results: it has been found out that after tempering with plastic deformation the manifestation of the Baushinger effect, when twisting the specimens to emergency angle in one direction and then in the reversed one, is of ambiguous character. This effect depends on the plastic deformation ratio of steel during heat treatment and on the direction of test strain. The anisotropy of properties observed constitutes an essential disadvantage for elastic elements operating under alternating loads. Practical significance: it has been found out that the lowest residual strain in the specimen is observed when the strain value during steel tempering corresponds to the deformation produced by emergency load. The obtained results will be useful in development of torsion shaft processing technology that provides reducing of anisotropy properties under alternating emergency load.
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