The purpose of this study is to develop a curve to the fatigue life of a specific portion of general structures. The weld).The weld has several variables that, if not controlled and studied, may change the resistance of loads applied to a whole structure, causing a premature failure of the structure. Focusing the study of this work in cyclic loading of welded structures, we must consider that a statistical analysis to determine the test load should be made, since there is not enough samples available, limiting the number of observations results. Making use of an infrared camera and the Thermoelastic Stress Analysis , we can observe the stress distribution along the specimen. Focusing around the welding spot, a potential residual tension can be examined. The study will take place on the existence of deviations within a continuous manufacturing process, where it can be found a divergence of cyclical elastic stresses for a product that has undergone the same manufacturing process.