两栖飞机铝合金的中低应变率力学性能

为研究水陆两栖飞机用航空铝合金材料在中低应变率区间内的动态力学性能，在常温下针对飞机船底壁板结构用7475-T761和7055-T76511铝合金采用电子式万能材料试验机开展准静态及低应变率拉伸实验，采用高速液压伺服试验机开展中应变率动态拉伸实验，获得了0.005～500 s^-1区间内的铝合金应力-应变曲线，拟合和验证了Johnson-Cook本构模型。结果表明：在应变率0.005～500 s^-1区间内，7475-T761和7055-T76511铝合金均呈现出了显著的应变率强化效应；从准静态向中应变率增加，7475-T761铝合金的失效应变随着增大，而7055-T76511铝合金先降低后增加；7475-T761铝合金表现出了显著的应变硬化效应，而7055-T76511铝合金应变硬化效应相对较弱；两种铝合金的断口形貌均未表现出明显的颈缩现象；拟合得到的Johnson-Cook本构模型能够较好表征两种铝合金材料的动态力学性能，最大均方根误差为13.7 MPa。

Dynamic Properties of Aluminum Alloys for Amphibious Aircraft under Medium-Low Strain Rate

In order to study the dynamic mechanical property of aluminum alloy for amphibious aircraft, dynamic tensile tests were carried out by using an electronic universal tensile test machine and high velocity test system at room temperature. The stress-strain curves of 7475-T761 and 7055-T76511 aluminum alloy of seaplane bilge structure were obtained under strain rate between 0.005~500 s-1, and Johnson-Cook constitutive model was fitted and verified. The results show that the strain rate hardening effect of 7475-T761 and 7055-T76511 aluminum alloy is obvious under strain rate between 0.005~500 s-1, and the failure strain increases with the increase of strain rate. 7475-T761 aluminum alloy has a certain strain hardening effect, but 7055-T76511 aluminum alloy has a weak strain hardening effect. The fracture morphology of two aluminum alloys shows no obvious necking phenomenon. The fitted John-Cook constitutive model can well characterize the dynamic mechanical properties of two aluminum alloys, and the maximum root mean square error is 13.7 MPa.