2A70合金动态力学性能与本构关系的研究

Dynamic Mechanical Behavior and Constitutive Relations of Aluminum Alloy 2A70

为了研究高速冲击条件下铝合金2A70的动态力学行为,开展了低应变率缺口试样拉伸试验及光滑试样应变率范围在0.1～4 000s-1的动态拉伸试验。试验结果表明2A70合金具有一定的应变率敏感性,尤其在应变率高于1 000s-1的情况下更为明显。试验数据被用来校核不同应变率修正形式的Johnson-Cook模型应变率修正项,拟合结果表明相对于其他的应变率修正,Cowper-Symonds修正能够更好地描述2A70合金的应变率效应。低应变率缺口拉伸试验和不同应变率下光滑试样拉伸试验得到的失效应变还被用来校核Johnson-Cook断裂模型参数。通过数值仿真动态拉伸试验,证明了采用Cowper-Symonds修正的Johnson-Cook模型以及断裂模型可以很好地描述2A70合金的动态特性。

To investigate the dynamic mechanical behavior of aluminum alloy 2A70 under high velocity impact, the tensile tests are carried out by using notched round bar in low strain rate and smooth round bar over a wide range of strain rates from 0.1 s-1 to 4 000 s-1. Test results indicate that 2A70 shows relatively evident strain rate sensitivity, especially for the strain rate higher than 1 000 s-1. The stand- ard Johnson-Cook strain rate term and several derivative forms are introduced and calibrated by the test data. The results show that the Cowper-Symonds form can demonstrate the rate effect of 2A70 much more better than the others. In addition, failure strains obtained from notched cylindrical specimens in low strain rate together with those obtained from different strain rate tests are used for calibrating the Johnson-Cook fracture model. To verify the parameters of Johnson-Cook model based on Cowper-Sym- onds form, a numerical simulation of Hopkinson tensile tests on 2A70 alloy are conducted, and the a- greement is quite well.