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.

This paper presents experimental and numerical analysis of the change of temperature and force in the vertical direction during the friction stir welding of high-strength aluminium alloy 2024 T3. This procedure confirmed the correctness of the numerical model, which is subsequently used for analysis of the temperature field in the welding zone, where it is different to determine the temperature experimentally. 3D finite element model is developed using the software package Abaqus; arbitrary Lagrangian-Eulerian formulation is applied. Johnson-Cook material law and Coulomb?s Law of friction are used for modelling the material behaviour. Temperature fields are symmetrical with respect to the welding line. The temperature values below the tool shoulder, i.e. in the welding zone, which are reached during the plunge stage, are approximately constant during the entire welding process and lie within the interval 430-502?C. The temperature of the material in the vicinity of the tool is about 500?C, while the values on the top surface of the welding plates (outside the welding zone, but close to the tool shoulder) are about 400?C. The temperature difference between the top and bottom surface of the plates is small, 10-15?C.

This work presents the results of studying harmful substances in the air, released in the case of tungsten inert gas (TIG) and metal inert gas (MIG) welding of 1460 aluminum alloy (Al-Cu-Li). It is shown that the TIG process is accompanied by smaller evolution of the solid component and gas component of welding fumes than in MIG welding. Ozone concentrations during TIG and MIG welding are significantly (1.3 and 7.4 times, respectively) higher than the maximum permissible concentration. It is found that ultraviolet radiation, accompanying the welding process, is the main factor of toxic gas generation in the working zone of the studied aluminum-lithium alloys. Also, this paper presents analyses of microstructure, hardness, strength characteristics and fatigue behavior of 1460 TIG weld joints.

In this paper, we will present our investigation of the quality of J55 microalloyed steel welds that were formed by a basic flux-cored wire electrodes that were of appropriate quality and alloyed with Ni and Mo. Based on the comparison and analysis of the obtained results related to the testing of the chemical composition, mechanical properties, toughness at test temperatures, and the microstructure of welding joints formed by a classic and specially coated rutile flux-cored electrode, we assessed the justification to switch from solid wire electrodes to flux-cored alloyed wire electrodes of appropriate quality. The research aim for the application of flux-cored wire electrodes instead of solid wire electrodes is based on the advantages pertaining to a flux-cored wire: molten metal from electrode wire is transferred in the form of fine droplets, easy welding and maximum productivity within all spatial positions related to welding, improved properties of welding joints, and increased productivity when compared to a classic solid wire. Our research encompasses the development of the experimental production at the Research and Development Center IHIS Belgrade (Development Institute for Chemical Power Sources), Serbia, of the new type of a coated electrode with improved welding properties when compared to a classic electrode intended for microalloyed steel welding.

This research paper presents hardness, structure and tensile strength analysis of 1460 alloy of Al-Cu-Li system, welded joints made by Tungsten Inert Gas (TIG) welding and Friction Stir Welding (FSW). Characteristics of acoustic noise at the welding operator workplace during mechanized TIG and FSW of aluminium-lithium alloy with the purpose to develop recommendations for the improvement of health and safety during welding processes were studied. Analyzing results, we concluded that during TIG welding the values of welding noise at the workplace, are much higher than the admissible noise level limit. Results showed that the values of the welding nose reach 95 dB. The noise level at the workplace for FSW is also dangerous and reaches up a value of 84.3 dB. Also, this paper presents hardness, structure, and tensile strength measurements of 1460 alloy welded joints made by TIG and FSW welding.

Complexity of pressure vessels geometry usually causes stress and strain concentrations. Modern approach of stress and strain analysis involves numerical and experimental testing. Every experimental testing on the construction could endanger construction itself. Therefore, making a model of the construction has great benefits. Sub-sized model of the pipe branch of A6 third pipeline at Hydropower Plant Perućica, Nikšić was made in order to be subjected to a detailed experimental testing. The aim was to determine internal pressure value causing pipe branch model to plastically deform, and, to use these results for determining pressure causing real structure to plastically deform, without any measurements on the structure itself. Experimental measurements were carried out using strain gauge method. Strain gauges are positioned in critical zones. Numerical pipe branch model and results obtained by using finite element method (FEM) was verified with experimental results (in elasticity area). After verification in elastic area, experimentally by increasing pressure value, critical internal pressure causing plastic deformation of pipe branch model was determined. Based on the pipe branch model behaviour, and after determination of relation between the model and the real structure, maximum calculated internal pressure value to which the structure may be subjected in exploitation is assessed. Besides, weak spots on the structure were verified by obtaining the same results through experiment and calculation, which gives good guidelines for monitoring of this structure during usage, since it is possible, by using this analysis, to decrease the number of measurement locations for monitoring (in order to control exactly those measurement locations, which proved to be the most endangered).