Fatigue Characteristics of Brass Welded Wire Joints

As a kind of welding wire, brass alloy has natural advantages. Its main advantages are good mechanical properties, good wear resistance and excellent fluidity. It is suitable for non-temperature cold welding. The fatigue characteristics of the lower joints are described below by HS221.

Fatigue is a process of cumulative damage, which is the change of material performance under repeated cyclic stress or strain. After enough cycles of cyclic stress or strain, fatigue crack or fracture will occur in the welded structure.

Compared with brittle fracture, the deformation of fatigue fracture is very small, but the fatigue fracture needs multiple loading, while brittle fracture usually needs multiple loading; structural brittle fracture is completed instantaneously, while fatigue crack propagation is slow, and it takes a period of time or even a long time to destroy. For brittle fracture, the influence of temperature is very important. With the decrease of temperature, the risk of brittle fracture increases rapidly, but the fatigue strength of materials does not change significantly.

The fatigue resistance of metal structure depends on its material, shape, size, surface state and service conditions. The fatigue fracture process of any material undergoes crack initiation, stable propagation and instability propagation, i.e. instantaneous fracture 0 stages.

The fatigue damage of welded structures often originates from the stress concentration zone of welded joints. Therefore, the fatigue of welded structures is actually the welding defects of fatigue welded joints in the details of welded joints, such as incomplete penetration, slag inclusion, undercut, crack, etc. This "congenital" fatigue crack source can directly pass the initiation stage of fatigue crack and shorten the fracture process. There are serious stress concentration and high welding residual stress in the welded joint, which will make the welded structure easier to produce fatigue cracks and lead to fatigue fracture.

The profile parameters of actual welded joints vary randomly along the weld length, and the resulting stress concentration also varies randomly. This randomness leads to fatigue crack initiation with random characteristics. Therefore, in the fatigue process of welded joints, multiple fatigue cracks may occur simultaneously or successively along the length direction of weld toes. The propagation of these small cracks causes adjacent cracks to merge into longer cracks, and longer cracks to further expand and merge into long and shallow fatigue cracks of weld toes.