Undercutting is a welding defect that appears as a groove in the base metal directly along the edges of the weld metal. It is inevitable in fillet and butt joints if improper welding parameters are used in the operation. It is a discontinuity in the welding that produces stress concentration and lowers the strength of the weld. The stress concentration factor of an undercut is due to the reinforcement angle, undercut width, undercut depth and undercut root radius. In this study, 20 mm thick mild steel plates were welded by automatic gas metal arc welding with the carbon dioxide (CO₂) shielding gas process. A single-V butt joint was obtained after welding. Before welding, 30° groove angles were obtained by milling on the longitudinal side of each workpiece. Two plates were welded with several passes. After welding, the weldment was tested with a radiographic non-destructive testing process. A defect-free weldment was obtained. Then, standard tensile test samples were machined from the weldment. A groove was drilled in the heat-affected zone, adjacent to the weld metal boundary on every tensile test sample. Each groove resembled an undercut. The length, root radius and depth of grooves were varied. Then, the samples were broken on a tensile test machine. From the test results, the static stress concentration factor of each groove was calculated. The effects of groove geometry on stress concentration factors were determined.

中文翻译：

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咬边几何形状对焊缝静应力集中系数的影响

咬边是一种焊接缺陷，在母材中直接沿着焊缝金属的边缘出现凹槽。如果在操作中使用不当的焊接参数，则在角焊缝和对接接头中不可避免。焊接中的不连续性会产生应力集中并降低焊接强度。咬边的应力集中系数取决于钢筋角度、咬边宽度、咬边深度和咬边根部半径。在这项研究中，20 毫米厚的低碳钢板通过自动气体保护金属电弧焊与二氧化碳 (CO ₂) 保护气体工艺。焊接后获得单V对接接头。焊接前，通过在每个工件的纵向侧铣削获得 30°的坡口角。两块板通过多次焊道焊接。焊接后，焊件通过射线照相无损检测过程进行测试。获得了无缺陷的焊件。然后，从焊件上加工出标准拉伸试验样品。在热影响区钻出一个凹槽，靠近每个拉伸试样上的焊缝金属边界。每个凹槽类似于底切。凹槽的长度、根部半径和深度各不相同。然后，样品在拉伸试验机上断裂。根据试验结果，计算出各槽的静应力集中系数。确定了凹槽几何形状对应力集中因子的影响。