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...
One of the important parameters of Refill Friction Stir Spot Welding is the so-called basic position of the tool. This is the arrangement of the pin and sleeve which occurs when the tool is plunged into the material. The basic positions can be divided into two categories. In the first category, the sleeve and the pin are above the sheet surface or below sheet surface and in the second category the pin is retracted within the sleeve or protrudes from it.The aim of the work was to test four settings of the basic position, and then determine the best setting of the basic position, without changing the other welding parameters. Joints made of an aluminum alloy 2024-T3 sheet having a thickness of 1.0 mm and an aluminum alloy D16UTW sheet having a thickness of 0.6 mm were analysed. The best setting of the basic position was determined based on assessment of the force carried in shear test, macrostructure and weld face of the joints.
The article presents material and functional tests carried out to implement the first part made in the Selective Laser Sintering (SLS) technology on the aircraft. The tests were done based on guidelines from aviation regulations and internal standards of PZL Mielec and Lockheed Martin Company.
Refill friction stir spot welding (RFSSW) is a new technique of metal structures joining. Within the framework of activities of PZL Mielec in R&D area (program Innolot) researches are realized which aim is to develop the RFSSW technology as a method of joining thin aluminum elements used in aircrafts constructions. The paper presents results of investigations on the RFSSW lap joints welded using rotations in the range from 1500 to 2000 rpm and tool sleeve plunge depth from 1.6 to 1.8 mm. Thin aluminum sheets of thickness 0.8 and 1.6 mm coated with alclad or anodized were welded. Results of the investigations prove that the most common cause of specimens breaking was presence of geometrical defect -the so called hook and weak bonding between parent material and working area of internal sleeve of RFSSW tool. The best tensile strength was reached in case of joint welded at rotational speed 2000 rpm and tool plunge depth 1.6 mm and 1.7 mm (5.37 kN and 5.87 kN adequately). These joints were characterized by very fine and uniform microstructure in the area between sleeve stirred zone and parent material.
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