以1.5mm热成形钢为例，建立超高强度钢点焊拉剪接头有限元模型，定义了热影响区几何尺寸及其材料属性，分析了熔核尺寸对点焊接头断裂模式的影响.结果表明：部分界面断裂模式在软化区发生并在焊核内沿板厚方向失效；而焊核剥离模式则在焊核外沿板厚方向失效；获得了不同断裂模式(界面断裂，部分界面断裂和焊核剥离断裂)下的临界熔核尺寸.为超高强度钢点焊拉剪接头断裂模式评价与预测提供了技术参考.
In this paper, a finite element model of ultra-high strength steel spot-welded lap-shear joint is established by taking the 1.5mm stamped boron steel as example, the geometric dimension and material properties of the heat affected zone are defined, and the effect of the nugget size on the fracture modes of a spot-welded joint is analyzed. The results show that PPF (part interfacial fracture) occurs in the softening zone and fails inside the nugget along the thickness direction of the sheets; PF (pull-out fracture) occurs outside the nugget along the thickness direction of the sheets. The critical nugget sizes of different fracture modes (interfacial fracture, part interfacial fracture and pull-out fracture) are obtained. The study provides technical reference for the evaluation and prediction of the fracture modes of ultra-high strength steel spot-welded joints.
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