Caracterización del proceso de soldadura por puntos por fricción agitación empleando el análisis de señales vibroacústicas

Abstract

Welding plays an important role in industrial processes, among the most important of which are electronic arc welding with consumable and non-consumable electrode; solid phase welding (cold welding, by friction, by explosion, by ultrasound, by diffusion, among others); gas welding, etc. Towards the end of the last century, in 1991, a new metal jointing process emerged, the welding by friction – agitation, Friction Stir Welding (FSW) This innovative process was created due to the necessity of making welded unions which were impossible to obtain by conventional fusion welding techniques, as is the case with some aluminum alloys which are used in aeronautical, motor and other relevant industrial sectors. Another improvement is the welding process of friction agitation by spots: Friction Stir Spot Welding (FSSW) which was created as an alternative to the method of Resistance Spot Welding (RSW) In this paper in addition to revising the existing bibliography up to the present date, completing a detailed description of the materials and methodologies employed in the development of investigation, the results of experiments obtained through the characterization and study of vibroacoustic waves emitted during the process and the execution of the mechanical trials to the dissimilar union wielded using FSSW are analyzed and discussed. An analysis of the behavior of the envelope of the signal during the process and the influence of the parameters of the process of FSSW in its form is carried out. What is more, an analogy between the envelope of the vibroacoustic signals with the forces during the process and the mechanical properties of the joint are also established; in addition, a macrographic analysis of the welding is also executed. Thus, the feasibility of the application of the technique for the study of this type of process is demonstrated in it. As the focus of attention for the analysis, the techniques of vibroacoustic signals analysis, and their correlation with the parameters of the process and mechanical properties of the joint are found. Basically the parameters are studied; speed of the tool’s rotation and the waiting time; evaluating as well its incidence in the mechanical properties of the welded union. Finally it is demonstrated that the vibroacoustic signals can be employed as a non-invasive technique in the detection of the stages of the process and forces during the FSSW process, which contributes to the main input of this project.