This paper deals with the heat generation in the Al alloy Al2024-T3 plate under different rotating speeds and plunge speeds during the plunge stage of friction stir welding (FSW). A three-dimensional finite element model (FEM) is developed in the commercial code ABAQUS/Explicit using the arbitrary Lagrangian-Eulerian formulation, the Johnson-Cook material law and Coulomb’s Law of friction. The heat generation in FSW can be divided into two parts: frictional heat generated by the tool and heat generated by material deformation near the pin and the tool shoulder region. Numerical results obtained in this work indicate a more prominent influence from the friction-generated heat. The slip rate of the tool relative to the workpiece material is related to this portion of heat. The material velocity, on the other hand, is related to the heat generated by plastic deformation. Increasing the plunging speed of the tool decreases the friction-generated heat and increases the amount of deformation-generated heat, while increasing the tool rotating speed has the opposite influence on both heat portions. Numerical results are compared with the experimental ones, in order to validate the numerical model, and a good agreement is obtained

A coupled thermo-mechanical model was developed to study the temperature fields, the plunge force and the plastic deformations of Al alloy 2024-T351 under different rotating speed: 350, 400 and 450 rpm, during the friction stir welding (FSW) process. Three-dimensional FE model has been developed in ABAQUS/Explicit using the arbitrary Lagrangian-Eulerian formulation, the Johnson-Cook material law and the Coulomb’s Law of friction. Numerical results indicate that the maximum temperature in the FSW process is lower than the melting point of the welding material. The temperature filed is approximately symmetrical along the welding line. A lower plastic strain region can be found near the welding tool in the trailing side on the bottom surface. With increasing rotation speed, the low plastic strain region is reduced. When the rotational speed is increased, the plunge force can be reduced. Regions with high equivalent plastic strains are observed which correspond to the nugget and the flow arm

The aim of this work is to analyse the process of friction stir welding (FSW) of 3 mm thick aluminium plates made of high strength aluminium alloy -2024 T3, as well as to assess the mechanical properties of the produced joints. Friction StirWelding is a modern procedure which enables joining of similar and dissimilar materials in the solid state, by the combined action of heat and mechanical work. This paper presents an analysis of the experimental results obtained by testing the butt welded joints. Tensile strength of the produced joints is assessed, as well as the distribution of hardness, micro-and macrostructure through the joints (in the base material, nugget, heat affected zone and thermo-mechanically affected zone). Different combinations of the tool rotation speed and the welding speed are used, and the dependence of the properties of the joints on these parameters of welding technology is determined.

The paper analyses the impact of the tool geometry on the friction stir welding (FSW) method on fracture toughness values of the base metal (BM) and weld metal (WM) of a butt welded joints of a high strength aluminium alloy. Values of fracture toughness KJIc were obtained using single-edge notched bend (SENB) specimens with fatigue precrack sampled from the BM and TMAZ (thermomechanically affected zone). Single specimen method was used according to ASTM E 1820 and parameters of elastic-plastic fracture mechanics were determined (CTOD crack tip opening displacement and the J integral). Although the welding tools had different values of cone angle (α = 2.5°-10°) and the variable length of the pin (h = 5.1 mm-5.4 mm) at a constant ratio of the number of tool revolutions and the speed of welding, the largest value of fracture toughness has the retreating side of the weld, then the advancing side of the WM, while the BM has the lowest value. This is the effect of recrystallization process in the retreating side of the WM due to combined rotating-straight forward motion of the tool during which the softened material is repeatedly transformed from one side to the other side around the centre of the tool.

M. Perović i dr.Utjecaj kinematičkih faktora zavarivanja trenjem miješanjem na karakteristike zavarenog spoja kovanih ploča od legure aluminija EN AW 7049 A Original scientific paper In this paper, the influence of rotation speed and welding speed on the impact strength, microstructure and cross section micro hardness of FSW welded joints of Al-Zn-Mg-Cu high strength aluminium alloy is studied. Rotation speed was varied from 750 min −1 to 850 min −1 and welding speed from 60 mm/min to 80 mm/min. It was found that the energy of crack propagation is up to three times higher than the energy of crack initiation. This ratio was found by testing the Charpy notched specimens taken from left and right from the weld centre, 4 mm from the notch in a direction opposite to a direction of welding. Micro hardness distribution in the nugget does not show large dissipation of value regardless if the measuring point is in the upper or lower section of the nugget. Weld microstructure characteristics and zones are clearly defined at the basis of grain size and material flow. Keywords: dynamic recrystallization; friction stir welding; impact strength; micro hardness distributionUtjecaj kinematičkih faktora zavarivanja trenjem miješanjem na karakteristike zavarenog spoja kovanih ploča od legure aluminija EN AW 7049 A Izvorni znanstveni članak U radu se analiziraju utjecaji broja okretaja i brzine zavarivanja na udarnu žilavost, metalografska obilježja i raspodjelu mikrotvrdoće po površini poprečnog presjeka FSW zavarenog spoja kovanih ploča od visokočvrste legure aluminija faznog sastava Al-Zn-Mg-Cu. Broj okretaja je mijenjan u rasponu od 750 min −1 do 850 min −1 , a brzina zavarivanja od 60 mm/min do 80 mm/min. Razdvajanjem energije inicijacije pukotine od energije potrebne za njezinu propagaciju, uočava se da je čak i do tri puta veća vrijednost energije koja je potrebna za njezinu propagaciju. Odnos energije inicijacije i energije propagacije je dobiven ispitivanjem Charpy epruvete sa zarezom u središtu, lijevo i desno od središta metala šava 4 mm u smjeru suprotnom od smjera zavarivanja. Distribucija mikrotvrdoće metala šava ne pokazuje veliko rasipanje vrijednosti bez obzira da li je mjerno mjesto u gornjoj ili donjoj razini površine zavarivanih komada. Na mikrograficima jasno se uočavaju zone strukturnih sadržaja zavarenog spoja na osnovi veličine zrna i linija tečenja materijala.