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FSW (Friction Stir Welding ) and RFSSW (Refill Friction Stir Spot Welding) joints have been increasingly used in industrial practice. They successfully replace fusion-welded, riveted or resistance-welded joints. In the last two decades, dynamic development of this method has stimulated investigations of the fast methods for joint diagnostics. These methods should be non-destructive and easy to be used in technological processes. The methods of assessment of joint quality are expected to detect discontinuities in the structures welded using FSW and FSSW methods. Reliable detection of flaws would substantially extend the range of applications of FSW joints across many sectors of industry, including aviation. The investigations carried out in this paper allowed for characterization of defects present in FSW and RFSSW joints. Causes of these defects were also stressed. An overview of the methodologies for assessment of joint quality was presented. Results of assessment of the quality of joints made of 2024T6 aluminium sheet metal using FSW and RFSSW method were presented.Keywords: Friction Stir Welding, investigation, defects Złącza FSW i RFSSW są coraz częściej stosowane w praktyce przemysłowej. Dobrze zastępują złącza spawane, nitowane czy zgrzewane oporowo. Dynamiczny rozwój metod w ostatnim dwudziestoleciu skutkuje poszukiwaniem szybkich metod diagnostyki złączy. Metody te powinny być nieniszczące oraz dać się zastosować podczas procesu technologicznego. Od sposobu oceny jakości złączy oczekuje się wykrycia nieciągłości struktur zgrzewanych metodą FSW i FSSW. Możliwość skutecznego wykrywania wad pozwoliłaby na znacznie szerszy zakres zastosowań złączy FSW w wielu sektorach przemysłu w tym w przemyśle lotniczym. Na podstawie przeprowadzonych badań w pracy przedstawiono charakterystykę defektów występujących w złączach FSW i RFSSW, wskazano na przyczyny ich występowania oraz przedstawiono przegląd metod badań umożliwiających ocenę jakości złączy. Zaprezentowano przykładowe wyniki oceny jakości złączy wykonanych z blach aluminiowych 2024T6 metodą FSW i RFSSW.

Friction stir welding is one of the newest methods of metal welding. The method is constantly being developed and friction stir spot welding (FSSW) is one of its varieties. The method is mainly used in the aircraft, automotive and shipbuilding industries. During the process, heat is generated as a result of friction between the tool and materials as well as plastic deformation of the joined materials. The paper presents a numerical analysis of welded structures made of 6061-T6 aluminium alloy. The specimens were joined by refill FSSW. This method joins metals in a solid state. The numerical calculations were performed using the ADINA System based on the finite element method. The sheets were modelled with shell elements and the joints were modelled with 3D-solid elements. The experimental investigations were carried out using a non-contact system allowing for measuring displacements and strains in real time. The numerical results were compared with the test ones. The structures were assessed regarding strength and the possibility of their application in the aircraft industry.Keywords Finite element method Á Aluminium 6061-T6 Á Refill friction stir spot welding (RFSSW)

Forming of titanium sheets, especially titanium alloy sheets, is very difficult due to low drawability caused by a high ratio of the yield point to the tensile strength Re/Rm, usually more than 90%. Although drawability of titanium sheets can be enhanced by forming at elevated temperatures it is avoided due to the high costs and difficulties associated with the operation of the process. Therefore the authors have developed an unconventional stamping method allowing for forming of almost unworkable materials at ambient temperature, such as Ti6Al4V titanium alloy. The paper presents both numerical simulation and experimental results of the stamping process using a device specially designed for this purpose.

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Friction stir welding (FSW) is one of the youngest methods of metal welding. Metals and its alloys are joined in a solid state at temperature lower than melting points of the joined materials. The method is constantly developed and friction stir spot welding (FSSW) is one of its varieties. In the friction stir spot welding process a specially designed tool is brought into rotation and plunged, straight down, in the joined materials. Heat is generated as a result of friction between the tool and materials, and plastic deformation of the joined materials. Softening (plastic zone) of the joined materials occurs. Simultaneously the materials are stirred. After removal of the tool, cooling down the stirred materials create a solid state joint.Numerical simulation of the process was carried out with the ADINA System based on the finite element method (FEM). The problem was considered as an axisymmetric one. A thermal and plastic material model was assumed for Al 6061-T6. Frictional heat was generated on the contact surfaces between the tool and the joined elements. The model of Coulomb friction, in which the friction coefficient depends on the temperature, was used.An influence of the tool geometry on heat generation in the welded materials was analysed. The calculations were carried out for different radiuses of the tool stem and for different angles of the abutment. Temperature distributions in the welded materials as a function of the process duration assuming a constant value of rotational tool speed and the speed of tool plunge were determined. Additionally, the effect of the stem radius and its height on the maximum temperature was analysed. The influence of tool geometry parameters on the temperature field and the temperature gradient in the welded materials was shown. It is important regarding the final result of FSSW.Keywords: Friction stir spot welding (FSSW), metal welding, FEM, Al 6061-T6Zgrzewanie tarciowe z przemieszaniem (FSW) jest jedną ze stosunkowo niedawno opracowanych metod łączenia metali. Należy do grupy metod łączenia metali i ich stopów w stanie stałym, w temperaturach niższych od temperatury topnienia łączonego materiału. Metoda jest stale rozwijana, a jedną z jej odmian jest punktowe zgrzewanie tarciowe z przemieszaniem (FSSW).W procesie punktowego zgrzewania tarciowego z przemieszaniem specjalnie zaprojektowane narzędzie wprowadzane jest w ruch obrotowy i wgłębiane, pionowo w dół, w obszar łączenia dwóch elementów. Wskutek tarcia narzędzia o materiał oraz plastycznego odkształcania materiału, generowane jest ciepło. Następuje zmiękczenie materiału łączonych elementów. Zmiękczony materiał (uplastyczniony) jest stale mieszany. Po wyprowadzeniu narzędzia, przemieszany materiał stygnąc tworzy między spajanymi elementami złącze w stanie stałym.Symulację numeryczną procesu za pomocą metody elementów skończonych wykonano z wykorzystaniem programu ADINA. Problem rozpatrywano jako zagadnienie osiowosymetryczne. Przyjęto termoplastyczny model materiału -Al 6061-T6. Ciepło tarcia generowane jest na pow...