Abstract: Straightness is one of the important quality parameters for shaft parts, and straightening is a necessary process in the production process of shafts. Aiming at the limitations of the existing straightening process, the straightening process by rotational bending for small and medium-sized shaft parts is proposed. Based on the universal finite element software LS-DYNA, the YU hardening model was used to carry out a numerical simulation study on the process, to reveal the straightening mechanism,and explore the influence of various factors on the straightening effect. The research results show that any material point undergoes multiple alternating positive and negative stress changes during the straightening process. In the process of gradual unloading, it is equivalent to that the shaft has undergone multiple reciprocating bends with gradually decreasing curvature, so that the curvature of any micro-segment in the axial direction gradually approaches zero to achieve its straightening. The residual deflection decreases with the increase of the bending amount. When the elastic area ratio reaches 0.2, the residual deflection reaches the minimum. As the rotation speed increases, the residual deflection first decreases and then increases. When the ratio of the rotation speed to the bending amount is 125 r/rad, the straightening effect is better. The length-diameter ratio, initial deflection and initial residual stress have little influence on the straightening effect, and good straightening results have been achieved by using the same process parameters.Numerical simulation results verify the feasibility of the process, without the need for complex initial deflection measurement, and the residual deflection of the plain shaft and stepped shaft after straightening are both within 0.1 mm.

Key words: straightening, shafts, hardening model, residual deflection, reciprocating bending