循环荷载作用下SN490B钢材本构关系试验研究

为对比结构消(耗)能元件芯材SN490B在单调和循环荷载作用下的本构关系，研究其在循环荷载作用下的力学特性，对20个SN490B钢材试件分别进行单调加载和16种加载制度下的循环加载试验，并对3种试件断口进行断口电镜扫描试验，分析SN490B钢材的单调性能、滞回性能和破坏形态，并采用Ramberg-Osgood模型拟合钢材的循环骨架曲线。试验结果表明：SN490B材料自身延性好，循环加载导致的材料累积损伤使其延性变差；循环荷载作用下，材料出现包辛格效应、循环硬化等现象，各滞回曲线均稳定饱满，具有较好的滞回性能；试件试验段伴随明显塑性变形而形成断口，断口微观为有微孔的波纹断裂表面，属延性破坏；应用Ramberg-Osgood模型拟合效果较好。SN490B钢材在循环荷载作用下的本构关系不同于单调荷载作用，采用单调荷载作用下材料的本构关系计算循环荷载作用下材料的反应不够准确。

Experimental study on constitutive relation of steel SN490B under cyclic loading

In order to obtain the constitutive relation of SN490B steel under cyclic loading and study the differences between constitutive behavior of SN490B steel under monotonic loading and cyclic loading, monotonic and cyclic experiments of 20 SN490B specimens including two monotonic tensile specimens, two monotonic compression specimens and sixteen different cyclic loading specimens were conducted. Moreover SEM experiments on fracture surface of specimens under monotonic loading, gradual amplitude cyclic loading and equal amplitude cyclic loading were also done. Based on the experimental data, the monotonic behavior, hysteretic behavior and macro-and micro-failure modes were investigated. The one-dimensional stress-strain skeleton curves under cyclic loading were fitted using Ramberg-Osgood model. The results show that SN490B steel has obvious merits such as good ductility, seismic behavior and hysteretic behavior. But cumulative damage caused by cyclic loading makes the ductility weakened. Bauschinger effect and cyclic hardening appear in the experiment. The details on the SEM photo shows the fracture is ductile fracture. The constitutive behavior of SN490B steel under monotonic loading and cyclic loading are different, so it is not accurate to predict the behavior of SN490B steel under cyclic loading using constitutive relation under monotonic loading. The study and the numerical value simulation of constitutive relation under cyclic loading are of great importance.