基于双线性强化模型的挤压凹模自增强技术研究

Research on Autofrettage Technology for Extrusion Die Based on Bilinear Hardening Model

为了进一步提高单层冷挤压凹模的弹性承载能力,可对其进行自增强处理。建立考虑材料应变硬化和包辛格效应的双线性强化自增强理论模型,得到自增强凹模三个加载过程的应力情况,并确定自增强压力的范围。采用ANSYS有限元软件对自增强挤压凹模的应力分布规律及内壁的位移做了数值模拟分析,模拟结果和理论计算相吻合。将采用双线性强化模型和理想弹塑性模型的结果进行比较,得到应变硬化和包辛格效应对自增强效果的影响规律。在凹模工作压力一定的情况下,通过优化分析,得到满足凹模尺寸精度和强度要求的最佳自增强压力,数值优化结果和理论解析值吻合较好,可为工程应用提供理论依据。

Autofrettage is adopted for improving the elastic load capacity of single-layer extrusion die.Bilinear kinematic hardening autofrettage model is established and the stress formulae of three loading procedures are derived considering the strain-hardening and Bauschinger effect of material.According to the theoretical formulae,autofrettage pressure scope is obtained.The simulations of stress distribution and the inner wall displacement of the autofrettaged extrusion die are performed by using ANSYS finite element software,and the results coincide well with the theoretical derivations.The effect law of strain-hardening and Bauschinger effect on autofrettage is discussed by comparing the results of bilinear kinematic hardening model and ideal elastoplastic model.When the working pressure is constant,the optimum value of the autofrettage pressure is determined to meet high size accuracy and strength requirement of a single-layer extrusion die.