基于钢框架梁柱焊接节点超低周疲劳性能的焊接孔构造优化研究

Research on configuration of access hole based on ultra-low cycle fatigue performance of steel beam-to-column connections

强往复荷载作用可能导致钢框架梁柱节点的焊接孔处发生超低周疲劳(ULCF)断裂,将数值模拟的应力应变状态代入循环孔洞扩张模型(CVGM)是预测ULCF断裂的普遍方法。将上述方法扩展至改进循环孔洞扩张模型(ICVGM),可用于各类焊接孔形节点的断裂预测,给出优化的焊接孔形。为此,基于既有试验数据提出ICVGM参数标定方法,确定Q355钢的相关参数;将ICVGM预测结果与钢框架节点局部试件断裂试验结果进行对比,揭示二者的一致性,验证ICVGM较CVGM的准确性;同时,采用ICVGM获得不同焊接孔形节点的断裂倾向,提出优化建议及合理孔形。有限元参数分析表明:增加焊接孔长度可以降低节点的断裂倾向;采用半圆形及FEMA-350推荐孔形节点的断裂倾向最低;优化孔形使得断裂位置由热影响区转移至母材,从而提高节点延性。

Severe cyclic loading can cause ultra-low cycle fatigue(ULCF)fracture of the materials around the access holes of steel moment connections.A general method for predicting the ULCF fracture is to substitute the stress-strain states of the material from numerical simulation into the cyclic void growth model(CVGM).The above method was extended to the improved cycle void growth model(ICVGM).The extended method was applied to the fracture prediction of connections with different access hole configurations in order to present the optimized configuration more intuitively.A calibration method for the ICVGM was proposed based on data from the literature to determine the corresponding parameters for Q355 steel.Then,the predicted results from ICVGM were compared with those of the fracture tests on local specimens of steel moment connections to demonstrate the consistency between them and verify the accuracy of ICVGM compared with CVGM.The fracture tendencies of the connections with different access holes were determined using the ICVGM to propose the optimized access hole.The FEM-based parametric analyses indicate that the fracture tendency of the joint decreases as the length of the access hole increases.The joints with the semi-circular and recommended access holes in FEMA-350 possess the lowest fracture tendencies.The optimized configuration improves the ductility of the joint by transferring the fracture point from the heat-affected zone to the base metal region.