中小型轴类零件旋转弯曲矫直工艺数值模拟研究

直线度是轴类零件重要的质量参数之一,矫直是轴生产过程中的一道必要工序。针对现有矫直工艺的局限性,提出中小型轴类零件旋转弯曲矫直工艺。基于通用有限元软件LS-DYNA,使用Y-U强化模型对工艺过程进行了数值模拟研究,揭示其矫直机理,探究各因素对矫直效果的影响。研究结果表明,矫直过程中材料任意质点应力均经历多次的正负交替变化,在逐渐卸载过程中使轴向任意微段的曲率逐渐趋近于零,实现其矫直。残余挠度随着弯曲量的增加而降低,当弹区比达到0.2时,残余挠度达到了最小。随着旋转速度的增加,残余挠度先减小再增大,当旋转速度与弯曲量的比值为125r/rad时,矫直效果较好。长径比、初始挠度(大小及挠曲形式)以及初始残余应力对矫直效果影响较小,采用相同的工艺参数均取得了良好的矫直效果。数值模拟结果验证了工艺的可行性,无需经过复杂的初始挠度测量,光轴和阶梯轴矫直后残余挠度均在0.1mm以内。

Numerical Simulation Research on Straightening Process of Small and Medium-sized Shaft Parts by Rotational Bending

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.