Welded joint

Welded joint

The joining of two or more metallic components by introducing fused metal (welding rod) into a fillet between the components or by raising the temperature of their surfaces or edges to the fusion temperature and applying pressure (flash welding).

Figure 1 shows three types of welded joints. In a lap weld, the edges of a plate are lapped one over the other and the edge of one is welded to the surface of the other. In a butt weld, the edge of one plate is brought in line with the edge of a second plate and the joint is filled with welding metal or the two edges are resistance-heated and pressed together to fuse. For a fillet weld, the edge of one plate is brought against the surface of another not in the same plane and welding metal is fused in the corner between the two plates, thus forming a fillet. The joint can be welded on one or both sides.

Because welded joints are usually exposed to a complex stress pattern as a result of the high temperature gradients present when the weld is made, it is customary to design joints by use of arbitrary and simplified equations and generous safety factors. The force F of direct loading, and consequently the stress S, is applied directly along or across a weld. The stress-force equation is then simply F = SA, in which A is the area of the plane of failure (Fig. 2). For eccentric loading, the force F causes longitudinal and transverse forces of varying magnitudes along the weld. See Structural connections