This research deals with the fatigue behavior of butt-welded joints, by considering the geometry and post-welding cooling cycles, as a result of cooling in quiet air and immersed in water. ASTM A-36 HR structural steel was used as the base metal for the shielded metal arc welding (SMAW) process with welding electrode E6013. The welding reinforcement was 1 mm and 3 mm, respectively; axial fatigue tests were carried out to determine the life and behavior in cracks propagation of the tested welded joints, mechanical characterization tests of properties in welded joints such as microhardness, Charpy impact test and metallographic analysis were carried out. The latter were used as input for the analysis by finite elements which influence the initiation and propagation of cracks and the evaluation of stress intensity factors (SIF). The latter led to obtaining the crack propagation rate and the geometric factor. The tested specimens were analyzed, by taking photographs of the cracks at its beginning in order to make a count of the marks at the origin of the crack. From the results obtained and the marks count, the fatigue crack growth rate and the influence of the cooling media on the life of the welded joint are validated, according to the experimental results. It can be concluded that the welded joints with a higher weld reinforcement have a shorter fatigue life. This is due to the stress concentration that occurs in the vicinity of the weld toe.

This work carries out a theoretical study about the influence that profile geometry of the weld seam joints has on fatigue life. It is considered that SMAW butt-welded joints, 6 mm-A36 structural steel board, and the E6013 electrode. The influence of geometry is parametrized by the overweight weld and the radius of the weld toe. To do the latter, an arrangement of experiments were made into 3 levels for each factor. For the development of the current work some information obtained from experimental results was used (i.e., weld profile and mechanical properties). The geometry of one group of real weld seams is digitalized and simulated in the construction of 3D solid-models, while a superficial semi-elliptical crack is defined around the weld toe. By applying the Finite Element Method, analytical equations are obtained for the weld magnification factors (Mk). As main results of this work stand out, on the first hand, the strong influence that slub has on the fatigue life, an excess thickness means a reduction in the life forecast to even 42% for the welded joint. Secondly, the different behavior of strength intensity factor around the crack edge, which makes the crack become longer and narrower. The analytical equations for Mk can be utilized on life-management model for butt-welded joints.