Thesis deals with individual technologies of packaging stator sheets and their use in practice. The greatest emphasis is placed on welding technologies, especially on the differences between the individual methods. The experimental part of the thesis is focused on finding suitable parameters for welding the stator package using a laser with a special wobling head. The samples were evaluated in terms of penetration depth, the number of defects, especially pores and grain coarsening.

This thesis is focused on laser welding and hybrid laser-TIG welding. The first part contains a brief theoretical description of these technologies. Standard quality and plasticity tests of welded joint are also mentioned. The second, experimental part, centres on the study of plasticity of tailored blanks (made of different types of HSLA steel), that are welded with laser and laser-TIG technology. The aim of the thesis is to assess process parameters effect on weld suitability for following deep drawning operation. Based on the calculated and measured figures obtained from the experiment, the most suitable welding parameters were chosen.

This work deals with the effects of high temperature exposition of low alloyed creep resistant steels on their structural stability and structural stability of their weld joint. The theoretical part of this work gives an overview of creep resistant steels considering their chemical and phase composition and their connection to high temperature mechanical properties. The CALPHAD method is presented as generally accepted approach for equilibrated calculations and Thermo-Calc and DICTRA software packages are introduced as CALPHAD applications. Thermo-Calc software is used for calculation of phase composition of the examined materials and for calculation of the phase diagrams. Software DICTRA is used for simulations of diffusion controlled phase reactions in the analysed weld. Experimentally one weld joint of the steels 15 128 and 15 313 has been studied after four different annealing procedures. The experimental results include chemical profiles across the welds, microhardness profiles and metallographic analysis of significant regions of the welds. These experimental results are compared with the simulation results. The comparison shows a reasonable agreement between experimental and simulation data.

In this master’s thesis there are set down dependencies of distortion of T-joints on the size of heat input and welding speed. Dependencies were found for single- and double-fillet welds, for single- and multiple-pass welding. The computer simulations were carried out in programs Visual-Weld and SYSWELD. The size of the melted zones, stress fields, material structure and hardness of the weld specimens were specified. Simulation results were compared with experimentally detected values.

Master’s thesis titled Welding of turbine rotor materials discusses evaluation of welding parameters by numerical simulation in software SYSWELD and Visual - WELD. Base material 23 CrMoNiWV 8-8 is welded by submerged arc welding technology. Used flux is F 26G and electrode is flux-cored wire TOPCORE 838 B. Material structures, hardness, values of residual stresses and distortion of weldment for this process are calculated by using the numerical analysis.

This project, elaborated within the master degree presents plates welding. Based on the literature study the problems of laser welding were designed optimal welding parameters. The material, on which were in the experimental part test and geometry analysis performed was steel Hardox 400 with thickness 5 mm. These welds were compared with welds made by MAG. Equipment used for werding was fiber laser.

The use of high-strength steel is more and more frequent in the car industry. I focused on USIBOR® 1500 steel welded by Nd-YAG laser. For my experiment, there were used various welding parameters and shielding gases. To compare the weld samples, I used the tensile, bending, macrostructure, microstructure and Vickers hardness test with different combinations of thickness as well as welded material.

Composite bridges in Sweden are commonly designed as a twin I-girder section. To stablizie the bridge during launching and concreting horizontal cross bracings are used. These are normally connected to a transverse web stiffener that is welded with a throat size of 5 mm regardless of the dimensions of the bridge. During an inspection of Vårby Bridge south of Stockholm in 2006 cracks were found in this weld between the transverse web stiffener and the top flange. After discovering of these problems the Swedish Transport Administration (Trafikverket) wants the designer to present calculations for this weld. The aim of this thesis was to investigate and compare the stresses in the weld between the top flange and the transverse stiffener for different cross bracings. A finite element model of a typical composite bridge, with five different types of cross bracings, was investigated using the FE program Brigade Plus. A selection of loads including temperature-, traffic- and fatigue loads were considered. The thesis clearly shows that the design of cross bracings will affect the stress levels in the weld.

This licentiate thesis is concerned with residual stresses in aluminum alloy 6061-T6 resistance spot welded joint. Several topics related to mechanical strength of welded structures are treated such as; nugget size and microhardness and microstructures of weld zone and their influence on mechanical strength of welded structure, failure load measurement using tensile-shear test, resistance spot welding simulation, residual stress measurement by X-ray diffraction method and analysis effect of welding parameters on the mechanical strength and the residual stresses. To investigate the effect of resistance spot weld parameters on mechanical strength of welded structures, various welding parameters e.g. welding current, welding time and electrode force are selected to produce welded joints with different quality. According to the failure mode, the empirical equation was used to prediction of failure load base on nugget size and hardness of failure line. Microstructure study has been carried out to investigate microstructural changes in the welded joints. Microhardness tests are done to find hardness profiles due to microstructural changes and determine the minimum hardness. In addition, an electro-thermal-structural coupled finite element model and X-ray diffraction residual stress measurement have been utilized to analyze residual stresses distribution in weld zone. The electrical and thermal contact conductance, as mandatory factors are applied in contact area between electrode-workpiece and workpiece-workpiece to resolve the complexity of the finite element model. The physical and mechanical properties of the material are defined as thermal-dependent in order to improve the accuracy of the model. Furthermore, the electrodes are removed after holding cycle using the birth and death elements method. Moreover, the effect of welding parameters on maximum residual stress is investigated and a regression model is proposed to predict maximum tensile residual stresses in terms of welding parameters. The results obtained from the finite element analysis have been used to build up two back-propagation artificial neural network models for the residual stresses and the nugget size prediction. The results revealed that the neural network models created in this study can accurately predict the nugget size and the residual stresses produced in resistance spot weld. Using a combination of these two developed models, the nugget size and the residual stresses can be predicted in terms of spot weld parameters with high speed and accuracy. / <p>QC 20131014</p> / No

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