基于SMMS模型的钢框架梁柱节点断裂分析

Fracture analyses for beam-column connections of steel frame based on the strain modified mean stress model

为了更好地预测钢结构焊接节点的延性断裂,结合空穴扩张模型(VGM)和应力修正临界应变模型(SMCS)的优点,提出了一种应变修正平均应力(SMMS)模型,给出了SMMS模型的推导过程.通过现有的平滑缺口圆棒拉伸试验校准了国产Q345钢材的VGM,SMCS和SMMS模型的韧性参数,分析比较了三种模型的特点及计算量大小.最后利用已有的Q345钢材梁柱节点局部焊接拉伸试验对SMMS模型预测钢材延性启裂的有效性展开分析.研究表明:SMMS模型的韧性参数与VGM,SMCS模型类似,在三种平滑缺口圆棒尺寸下的校准结果均比较接近,且其离散系数较小,说明SMMS模型的韧性参数是材料的固有属性;SMMS模型相比VGM模型计算较为简便,相比SMCS模型受应力三轴度的波动影响较小;SMMS模型的延性启裂预测结果与VGM模型较为接近,且与试验值较为相符,表明SMMS模型可用于钢结构焊接节点的延性断裂预测.

To better predict the ductile fracture of welded connections in steel structures,a strain modified mean stress(SMMS)model was proposed,which combines the advantages of the void growth model(VGM)and the stress modified critical strain(SMCS)model.The derivation process of the model was given.The VGM,SMCS model and SMMS model parameters of Q345 steel made in China were calibrated through the existing tensile tests of notched round bars.The characteristic and calculation workload of the each model was analyzed and compared.Finally,the effectiveness of SMMS model in predicting ductile fracture of steel was analyzed by using the existing local welded tensile tests of Q345 beam-column connections.The results show that the SMMS model parameters of three notched tests are close like the VGM and the SMCS model.The dispersion coefficient of the SMMS parameters is small,which indicates that the parameters are the inherent properties of materials.The SMMS model is simpler than the VGM and less affected by the fluctuation of stress triaxiality than the SMCS model.The ductile fracture prediction of the SMMS model is close to VGM and in good agreement with the experimental values,which shows that the SMMS model can be used to predict the ductile fracture of welded connections in steel structures.