53 Nonconventional Technologies Review 2021 Romanian Association of Nonconventional Technologies Romania, March 2021 FLEXIBLE NONCONVENTIONAL HYBRID WELDING SYSTEM FSW-US Octavian Victor Oancă 1 , Nicușor-Alin Sîrbu 2 , Gabriela Victoria Mnerie 3 , Emilia Binchiciu 4 1 National R&D Institute for Welding and Material Testing – ISIM Timisoara, ooanca@isim.ro 2 National R&D Institute for Welding and Material Testing – ISIM Timisoara, asirbu@isim.ro 3 National R&D Institute for Welding and Material Testing – ISIM Timisoara, gmnerie@isim.ro 4 National R&D Institute for Welding and Material Testing – ISIM Timisoara, ebinchiciu@isim.ro ABSTRACT: Welding and metalworking technologies, which use ultrasonic vibration either as a primary source to achieve the prescribed operation or as an auxiliary source to improve operation efficiency and product quality, are current in international and applied international research. By assisting the ultrasonic vibration welding process, certain advantages are ensured related to the improvement of the components' behavior during the process, as well as the mechanical properties and the final quality of the joints. These advantages which, compared to conventional processes, lead to remarkable and globalized applications of ultrasonic vibration in welding. The research undertaken within ISIM led to the development of an experimental model of friction welding with rotating active element (FSW - Friction Stir Welding), equipped with an ultrasonic assistance system (US). Specialized software programs were used for constructive simulation and sizing of appropriate sonotrodes, for the frequencies of 20, 35, and 40 kHz, developed and tested to interface them in the construction of the experimental model used. The joining parts on which the sonotrodes were tested is the aluminum alloy EN AW 1200. KEYWORDS: nonconventional joint, ultrasonic vibration, experimental model, sonotrode, aluminum alloy EN AW 1200. 1. INTRODUCTION Throughout the history of welding technologies, the unconventional approach has always been a way to increase performance. In this sense, the physical phenomenon of friction is known in the art as a cause of energy dissipation; In the variant in which friction is the basis of the friction welding process (FSW), this solid-state joining process can be included in the category of nonconventional welding technologies. Research on the applicability of FSW is estimated to be still in its infancy, although it has been successfully applied to the fabrication of structural components that are difficult to weld in aerospace, rail, automotive, shipbuilding and others [10]. Friction welding (FSW) is considered one of the green manufacturing technologies because it produces minimal emissions to the environment, the sustainability of the technology is enhanced by the hybridization of the process [1]. Manufacturing technologies based on the concentration of energy developed by ultrasonic waves fall into the category of nonconventional technologies [5], [8]. Thus, ultrasonic welding occupies an important place in this processing category [5]. To improve the results obtained by friction welding, there have been concerns of researchers in the direction of stimulating the conditions by the simultaneous use in the workplace of ultrasonic vibrations (ultrasound) [2], [3], [4], [9]. The research focused on some constructive aspects regarding the creation of optimal FSW conditions with US assistance, as well as on the behavior of the metal components subjected to the joint (aluminum alloy EN AW 1200), as well as the welding quality, under the application of different regimes of thing [6]. This paper reflects, in addition to a synthesis of some results obtained in certain customized working conditions, and some ways of constructive design and process simulation, with the application of special software programs, designed and used. 2. EXPERIMENTAL CONDITIONS Figure 1. Ultrasonic welding vs. friction stir welding. [10] The experimental research was carried out in a broader framework offered by the National Research- Development Institute for Welding and Testing of Materials - ISIM Timișoara, with an experience of over 50 years, in which strategic research and innovation objectives of by strengthening technical and technological competence [8], [10]. Following extensive documentation on international concerns about FSW, the laboratory specializing in ultrasound technology recovery, CEX-US, has been expanded, continuing to promote excellence in every direction, developing and capitalizing on hybrid technologies