循环荷载作用下管桁结构直接焊接节点焊材本构关系试验研究

Experimental study on constitutive relation of directly-welded joints of tubular truss structures under cyclic loading

对管桁结构直接焊接相贯节点中存在的焊缝,制作标准试件进行低周疲劳试验,得到σ-ε滞回曲线、循环应力幅值退化曲线,分析了焊材试件的破坏模式及在三种等幅循环荷载作用下滞回曲线的特点。利用ABAQUS软件模拟试验过程,与试验滞回曲线做对比,并用Ramberg-Osgood模型拟合了循环应力-应变曲线。结果表明,焊材损伤累积破坏过程分为三个阶段,裂纹萌生和破坏阶段应力幅退化较快,裂纹稳定发展阶段变化较慢;在循环荷载作用下,随着循环周数的增加,焊材循环应力幅值、卸载刚度和耗能能力均逐渐减小,呈现出循环软化特性;ABAQUS模拟的滞回曲线与试验曲线吻合较好,表明由循环加载试验标定的强化参数能用于有限元分析;Ramberg-Osgood模型能够较好模拟循环应力-应变曲线。

To study the welds existing in directly-welded joints in the intersecting nodes of the tubular truss structure, standard specimens were made for low-cycle fatigue tests. The σ-ε hysteresis curve and the cyclic stress amplitude degradation curve were obtained, and the failure mode of the welding material specimen and the characteristics of the hysteresis curve under the action of three constant amplitude cyclic loads were analyzed. ABAQUS software was used to simulate the experimental process to compare with the experimental hysteresis curve, and Ramberg-Osgood model was used to fit the cyclic stress-strain curve. The results show that the cumulative damage of welding consumables is divided into three stages. The stress amplitude degenerates faster in the crack initiation and failure stages, and the crack stable development stage changes slowly;under the action of cyclic loading, as the number of cycles increases, the cyclic stress amplitude of the welding materials, unloading stiffness and energy dissipation capacity are gradually reduced, showing cyclic softening characteristics;the hysteresis curve simulated by ABAQUS is in good agreement with the test curve, and the strengthening parameters calibrated by the cyclic loading test can be used for finite element analysis;Ramberg-Osgood model can simulate the cyclic stress-strain curve well.