循环荷载作用下高强铝合金本构关系试验研究

Experimental investigation on constitutive relationship of high strength aluminum alloy under cyclic loading

为研究高强铝合金结构在地震作用下的响应、建立循环荷载作用下高强铝合金的本构关系,对17个7A04高强铝合金试件进行了单调拉伸和多种循环加载制度下的试验。分析了材料的单调性能、滞回性能、宏观破坏形态与电镜下的微观破坏形态。采用Ramberg-Osgood模型拟合了材料的循环骨架曲线,并与单调拉伸曲线做出了对比。试验结果表明:7A04高强铝合金延性较差,破坏突然、断面与拉应力方向成45度;循环荷载下表现出典型的循环硬化现象,在压应变达到1%后,其刚度和强度发生退化;材料在滞回中表现出了混合强化的特征,既包含各项同性强化又包含了随动强化。该高强铝合金在循环荷载作用下的本构关系与单调荷载作用下的本构关系存在较大区别,不能将单调荷载下的本构关系用于循环本构关系中。本文为准确计算高强铝合金结构在地震作用下的响应提供了重要基础与依据。

In order to investigate the response of high strength aluminum alloy structures under earthquake and to develop constitutive relationship of high strength aluminum alloy under cyclic loading,tests of 17 7A04 high strength aluminum alloy specimens were conducted under monotonic loading and many kinds of cyclic loading. The monotonic behavior,hysteretic behavior,macroscopic failure modes and micro-failure modes under electron microscope of the material were analyzed. Stress-strain skeleton curves under cyclic loading were fitted by Ramberg-Osgood model and compared with stress-strain curves under monotonic loading. The test results show that 7A04 high strength aluminum alloy has relatively poor ductility. The specimens break in a sudden process and the fracture surface makes a 45-degree angle with the tensile stress direction. Cyclic hardening behavior appears in the cyclic loading tests. When the compressive strain is larger than 1%,the stiffness degradation and strength degradation occur. The material shows mixed hardening behavior in the tests which includes isotropic hardening and kinematic hardening. The constitutive relationship of the high strength aluminum alloy under cyclic loading differs from that under monotonic loading. These two types of different constitutive relationship should be distinguished. The paper supplies an important basis and foundation for accurate calculation of high strength aluminum alloy structures under earthquakes.