基于Nakajima试验的6061-T6铝合金胀形回弹规律研究

Research on bulging springback of AA6061-T6 based on Nakajima test

通过单向拉伸试验测试分析了不同轧制方向的6061-T6铝合金的基本力学性能,建立了Barlat＇89各向异性屈服模型和Hollomon各向同性硬化模型。在此基础上,开展了不同宽度（20～60 mm）试样Nakajima胀形回弹有限元模拟与试验,研究了在相同冲压位移下回弹量的变化规律,分析了回弹前后不同宽度试样的应力应变状态与材料流动状况,揭示了不同宽度对胀形回弹的影响机制。结果表明：对于宽度为20～60 mm的胀形试样,回弹主要发生在试样长度方向,且随着试样宽度的增加,试样长度方向上的回弹量增大;在本次Nakajima试验条件下试样处于拉-压应变状态,卸载后试样在长度方向上收缩、宽度方向上扩展;试样宽度增大,宽度方向流动阻力和弹性应力增加,促使长度方向上回弹量增加。

The basic mechanical properties of AA6061-T6 with different rolling directions were tested and analyzed by uniaxial tensile test,and the Barlat＇89 anisotropic yield model and Hollomon isotropic hardening model of AA6061-T6 material were built. On this basis,Nakajima springback simulation and test of sheets with widths ranging from 20 mm to 60 mm were carried out. Then,the springback rules under the same punching displacement were studied. The state of stress and strain evolution and material flow status were analyzed,which revealed the influence mechanism of different widths on bulging springback. The results show that the springback mainly occurs in the length direction of the sheet with widths ranging from 20 mm to 60 mm,which increases with increasing width of the sheet. The sheets are in a strain state of tension-compression on this Nakajima test conditions. After unloading,the sheets shrink in the direction of length and expand in the direction of width; the flow stress and the elastic stress in the width direction increase with the width of the sheets increases,which increase the springback in the length direction.