Thesis deals with individual technology of new welding processes "specifically FRONIUS TPSi". The greatest emphasis is on welding technology, especially on the differences between the individual methods. The experimental part of the thesis is focused on finding suitable parameters for welding filled welds.Everythingwith respect to required welds quality welded by robotic welding. The samples were evaluated in terms of penetration depth, amount of heat introduced and the number of defects.

In the present work, an investigation of the fatigue life benefits emerging from fillet weld geometries optimization has been carried out. At first, an introduction to ageing mechanisms, corrosion and especially fatigue, acting on operating marine structures has been made. Residual stresses at weld toes, stress modes, and types, geometrical factors (weld angle, toe radius, leg length), welding techniques selected, post-welding treatment and plate‟s material are some of the principal factors affecting the fatigue life of a fillet weld joint. Especially, the accuracy of various approaches in fatigue life estimation of specific geometries under pre-set types and levels of stress is studied. It is evident so far that even the notch stress concept is the most accurate method based on S-N curves, the Fracture Mechanics approach can offer more accurate solutions of a crack development through the material. Towards this, a literature review on crack evolution aspects in welded and non-welded plates under bending and tension was performed; substantial parameters were determined and finally implemented in the LEFM model which was used for the simulation purposes of Chapter 6. As far as the crack aspect ratio evolution is concerned, an extensive reference is available in literature since many researchers have investigated its contribution to the determination of geometrical paths, commonly known as “Preferred Propagation Paths”. Their significance is related with our ability to determine accurate SIF solutions leading to precise fatigue life estimations. A typical fillet weld joint 2-D model has been developed in CAE Abaqus software and a Finite Element Analysis of subject T-profile has been carried out. Through this analysis, the fillet weld angle, the weld leg length, the weld toe curvature radio ρ and the carrying load plate thickness are examined for their impacts on the maximum surface stress. Finally, a number of stress mitigating measures are proposed and their effects are analyzed. Undoubtedly, the notch stress concept today is gradually gaining more and more acceptance among other fatigue analysis practices, hence the need for an estimation of the actual surface stresses along fillet weld toes, has become imperative. Towards this, different 2-D geometries are tested against stress concentration factors developed at weld toes, which are calculated on the basis of maximum in-plane principal stresses over nominal stresses in mode I pure bending and pure tension respectively. Moreover, validation with corresponding results from literature is provided. Finally, three different concepts for reducing the maximum surface stresses are presented. The first one proposes grinding of the weld toe area and formulation of an artificial U-notch or a part- circular profile. The second one applies to non-penetrating welds and assumes the existence of a root gap of a specific geometry which is related to the fatigue life and stress concentration factor of the fillet weld joint. Last but not least, the relatively recent concept of the variable radius notch is discussed, even though it is applicable mostly to notched bodies, not weld joints. Afterwards, a Linear Elastic Fracture Mechanics analysis of reference 2D fillet weld model is demonstrated. A number of geometrical parameters considered at previous stage for their impact on surface Stress Concentration levels at the weld toe region, have been correlated to fatigue life benefits in terms of increased number of stress cycles till failure. An extensive analysis of 9 different T-butt weld joint geometries has been provided in order to investigate how positively a possible SCF reduction can affect the fatigue life of a weld joint. Essential geometric variations (weld angle, length, toe radius, root slot) were considered in the 2D model. All calculated benefits both in pure bending and pure tension cases have been reported accordingly. Based on a linear interpolation of the points scatter (SCF, N-cycles) both in banding and tension, it was observed that a surface stress mitigation of 1% could lead to 1,33 up to 2,5% fatigue life benefit in the range of SCF=2 – 2,5. It is evident so far that the geometrical optimization of a weld joint in respect of notch stress mitigation can be a powerful tool both in shipbuilding and maintenance practice in the future. However, technically wise their application may incur high initial costs of improved tools of welding and post welding treatment and robots even though it would consist a cost effective solution in a medium/long term basis. Finally, the above process is followed by a reliability analysis of the most critical geometrical parameters affecting the fatigue life of a fillet weld joint. Reliability assessment results concerning medium, high and low cycle fatigue are provided and a comparative analysis of each factor‟s impact on fatigue life has been carried out.

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The thesis is focused on microstructural stability of heterogeneous weld joint of ODS steel and tungsten. The theoretical part summarizes the basic information about the structure and properties of ODS steels and describes the methods of joining these steels with tungsten. In the experimental part, materials MA956 and WL10 were welded by using electron beam. The individual samples differ by preheating temperature or use filler material. After annealing at 800 °C/1h and 1000 °C/5h, a change of the weld metal microstructure was evaluated by using scanning electron microscope. The chemical composition was measured by energy dispersive spectroscopy. It has been found that during annealing, massive precipitation of particles occures in the whole volume of the weld metal. These particles were identified as Laves phase.

This thesis submitted deals with the project of the change of the production of the semi-finished product of the console which is produced by casting from the cast iron ČSN 42 2420. The component forms the frame of the deburring machine with two electric motors with the gearbox. For the suggested production the method MAG of technology welding was chosen. Because of the given technology the new construction of the component was chosen. The welded product consists of eight parts burnt from heavy-walled sheet metals. The suggested material of the construction is steel S235JR and for welding the filler rod Weld G3Si1, diameter 1 mm is chosen. For the determination of the optimal parameters of welding the testing through the slap next to the skin weld (size a5) was made. Simultaneously with the testing the fracture areas and the weld root were examined. The suggested parameters of welding were used during the preparation of WPS. For the assembling of the component the operating schedule of welding is planned.

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.

Volvo Construction Equipment (VCE) has invested in an advanced lasermachine that can cut sheet metal parts with angled edges. As a result, thedevice provides expanded possibilities in the design and production of sheetmetal products.The material cost component is significant in the production of sheet metalproducts. This cost can be reduced by reducing the plate's thickness andchanging its dimensions.This study examines the effects of a thinner plate thickness combined withchanged height and width dimensions and a more robust weld joint inmanufacturing a so-called A stay, a part of the articulated hauler from VCE.The study was conducted with the Design for Six Sigma (DFSS) process,product research, development, and R&D methodology, which falls under theoverall scientific, technical research methodology "Systems Engineering."The study's conclusion shows that material saving with a thinner sheet is at theexpense of reduced quality and product cycle life. In addition,recommendations for in-depth analyses have also been proposed in the study'sdiscussion section.

The object of this thesis is to assess the structural stability of heterogeneous weld joint, which consists of two different base materials (16,537 steel and 16,236 steel) and weld metal NiCrMo2.5-IG with buttering layer P24-IG. All these materials belong to the group of low-alloyed creep-resistant steels that are to be used mainly in the power industry. The weld joint was made by application of the TIG hot wire welding method. Structural stability of this joint was evaluated by carbon redistribution and microstructural changes after annealing in temperature 300 °C and 400 °C during 500 hours. For modelling the phase composition of particular steels was used the ThermoCalc software. All gained results should be employed to appraise whether the heterogeneous weld joint of the steam turbine´s rotor is eligible for long-term operation in hard working conditions.

Syftet med rapporten var att utveckla en transportvagn hos företaget Arronet Teknik AB där ett grundkoncept redan var uppfunnet sedan tidigare. Uppdraget skulle utföras för att effektivisera företagets nuvarande plåttransport. Transportvagnens huvudsakliga syfte var att transportera plåt på ett säkert, ergonomisk och praktiskt sätt från plåtlagerslokalen till produktionslokalen för beskärning. Eftersom produkten skulle sammansvetsas med metallrör, samlades litteraturstudier in i teorin för att identifiera vilket material som stålkonstruktionen ska konstrueras i. Materialet skulle ha god svetsbarhet och vara starkt föratt klara av tunga laster av plåt. Litteraturstudien innehöll även utformning av olikasvetsfogsdesigner och hur de implementeras i metallrörskonstruktioner. För att besvara frågeställning ett, som handlade om vilka krav som ställs på transportvagnen, utfördes en semi-strukturerad intervju i kombination med direkta observationer för att samla in kundkrav. Kundkraven omvandlades till produktkrav som därefter introducerades till produktutvecklingsprocessen. Frågeställning två handlade om hur transportvagnen kundekonstrueras för att uppfylla de identifierade kraven. För att besvara frågeställningen delades produktutvecklingsprocessen upp i två delar där koncept för drivna vagnar utforskades och koncept för en drivande vagn. Tester med FEM-simulationer och ostrukturerade intervjuer användes för att bestämma varsitt koncept. Arbetet resulterade i ett underlag för företaget med konstruktionsförslag för de påkopplade vagnarna, den drivande vagnen och andra komponenter som tillhörde transportvagnen. Resultaten analyserades och diskuterades därefter. / The purpose of the study was to develop a design proposition for a transport cart for Arronet Teknik AB where a basic concept already had been developed. The purpose of the task was to streamline the company’s current sheet metal handling process. The transport cart’s main purpose was to transport sheet metal in a safe, ergonomic, and practical way from the warehouse to the production premises for processing. Because the transport cart was to be welded together with metal tubes, literature studies had to be done for the theory, to identify the most common metals used in welded metal constructions. Hence the literature study contained different configurations of welding joints and how they integrate tubular constructions. To answer research question 1 which asked what the requirements of the transport cart was, a semi-structured interview in combination with direct observations was needed to collect customer requirements. The customer requirements where then translated into product requirements and then introduced into the product development process. Research question 2asked how the transport cart was to be constructed to fulfil the previously stated requirements. To answer the question the product development process was divided into two parts where one part contained the development of the driven carts and the other contained the drivetrain. Tests with FEM-simulations and unstructured interviews was used to decide upon the final concepts. The study resulted in proposed design for the company. Afterwards the results were analysed and discussed

The structural stability of creep-resistant steels P22, P91 and Eurofer´97 and structural stability of weld joint P22/P91 have been studied. The microstructural changes during annealing at temperatures of 500 – 900°C were examined. The state of equilibrium have been simulated using the ThermoCalc software. The computed results were compared with published data. A good agreement between the simulation and the published data was observed.