Les structures assemblées par points de soudure doivent satisfaire à un grand nombre de critères de performance, portant entre autres sur des aspects statiques, dynamiques, acoustiques, ou crash, qui sont fortement influencés par le nombre et la position des points de soudure. De plus, certains d’entre eux peuvent être défaillants en sortie de ligne d’assemblage ou le devenir au cours de la vie du véhicule, ce qui induit des dispersions des performances. Le challenge est donc de déterminer, dans un temps d’analyse raisonnable, le nombre et la répartition optimale des points de soudure permettant la vérification des objectifs de performance tout en garantissant le meilleur compromis entre le coût de fabrication et la robustesse des performances. Une procédure adaptative est proposée, permettant à chaque itération d’ajouter et de supprimer des points de soudure, afin d’obtenir une conception robuste. Une procédure itérative de robustesse info-gap est également présentée, afin d’analyser l’impact de la perte des points de soudure les plus influents. On définit ainsi une procédure de contrôle qualité, portant sur un petit nombre de points de soudure, permettant de garantir l’homogénéité des performances des structures fabriquées en série. Toutes les méthodologies sont validées sur une caisse en blanc de véhicule industriel.En pratique, la conception doit satisfaire plusieurs critères antagonistes. La procédure adaptative est donc étendue à l’optimisation multi-objectifs, afin d’obtenir le meilleur compromis possible en fonction des critères considérés. Une illustration portant sur l’optimisation dynamique et vibro-acoustique d’une cavité passager est finalement mené / Spot welded structures must satisfy a large variety of performance characteristics including static, noise, vibration and harshness and crash, which are strongly influenced by the numbers and positions of the spot welds. Moreover, some spot welds may be missing when structures leave the assembly line or break during lifetime of vehicle, inducing large variations in the performance characteristics. The challenge is to find the best locations and number of spot welds to achieve the performance goals while taking into account the trade-offs between manufacturing cost and robust to uncertainty in reasonable time frame. An adaptive optimization procedure is proposed, which iteratively adds and removes spot welds to obtain the robust design efficiently. An iterative procedure is also proposed to obtain the info-gap robustness curve, which allows analyzing the impact of the loss of the most influential spot welds on performance. This leads to define a quality control procedure for a small number of spot welds to guarantee the performance of a population of nominally identical structures within acceptable limits. All the methodologies are validated on a full industrial body-in-white of a vehicle.In practice, the design must satisfy several stringent and conflicting objectives simultaneously. Thus, we extend the adaptive procedure to handle multi-objective problems using the weight-sum approach reflecting the importance given to individual spot welds to obtain efficient solutions in the objective space. Finally, we propose a strategy to optimize the vibro-acoustic behavior of the passenger cabin of a vehicle by designing the numbers and positions of the spot welds.

Surface treatments used to improve the life of a material known as peening are already extensively used in industry. The main aim of peening is to introduce compressive resiudal stress to the surface and subsurface of a metallic material, however literature also includes a number of microstructural and mechanical effects that peening introduces to a material when the compressive residual stress is established. The aim of this dissertation is compare and contrast the mechanical and microstructural effects of a current industrial peening method called shot peening, with three new increasingly competitive surface treatments. These are laser shock peening, ultrasonic impact treatment and water jet cavitation peening. The surface finish, and changes in microstructure, hardness depth profile, residual stress depth profile and plastic work depth profile of the four surface treatments are analysed. The effect of the peening parameters on the material is also determined, such as length of time of treatment, shot size, step size, direction of treatment, and irradiance per centimetre squared. The effect of peening on the residual stress depth profile of a gas tungsten eight pass grooved weld is also determined. Welding is a known region of early failure of material, with one of the factors affecting this being the introduction of tensile residual stress to the surface and near surface of the weld. An analysis to determine if peening the welded region alters the residual stress was carried out. In all experiments in this dissertation, the material that was used was austenitic stainless steel, as this material is highly used, especially within the nuclear industry. The results of this dissertation show that different peening types and peenign parameters produce a variety of surface, microstructural and mechanical effects to austenitic stainless steel. Peening of an aaustenitic stainless steel welded region results in teh near surface tensile residual stress to alter to ccompressive residual stress.

The problematics of weldability of heterogeneous welds of aluminium and titanium alloys produced by electron beam welding is discussed in this work. Homogenous welds of selected alloys were analyzed in the first stage. Welding of these materials relates to formation of intermetallic phases at the interface of base materials due to differences in physical, chemical and metallurgical properties of base materials. One of the prerequisites for producing high quality weld joints is to find optimal process parameters. The influence of selected process parameters to integrity, structure and mechanical properties of heterogeneous Al/Ti joints is evaluated.

The diploma thesis focuses on laser welding of extra deep-drawn steel sheet according to the standard WSS-M1A365-A14 with a protective zinc surface layer. A 0,9 mm thick steel sheet with a zinc layer with coating weight 50 g · m^-2 is welded by a hybrid welding method Laser-TIG. The laser, as the primary energy source, is used for welding the material. The arc, provided by a non-melting tungsten electrode, is used for preheating the material for melting and evaporation of the zinc layer. Based on the initial experiments, the magnitude of the laser power with the welding speed was chosen as a constant parameter. The magnitude of the electric current, as the variable parameter, was set up to 0, 20, 30 and 40 ampers for welding the lap and the butt welds. Only one piece of the each weld type combination was made. The welds were afterwards tested to verify their quality and material properties. The first differences between laser welding with or without TIG preheating were visible during the experiment. The positive effects of the laser welding with preheating by TIG were confirmed. The material properties of the joints achieved better values and a influence of the welding defects on the quality of the joints was reduced. The Laser-TIG is a good choice for welding galvanized steel sheets in the mass production of automotive industry and it could be improved by more researches.

Design of flat pallet for automatic parking garage. Parking and description of automatic parking systems. Welding and weldability of materials. Electric arc welding and welding by melting electrode in protective gas by MIG/MAG method, welding instruments. Design of parking palette calculation and calculation this palette by MKP method. Process of drawing documentation for parking palette. Design of welding process and WPS. Description of annealing and zinc coating. Economic-technical analysis of palette for automatic parking system production.

Diploma thesis deals with creating of computational model of welded frame to perform strain-stress analysis. Thesis aims at verification of welded joints and their possible changes. The next goal is to compare stresses obtained from calculation with respect to welding standard and FEM analysis.

This report has been performed for WSP Construction Design located at Arenavägen 7 in Stockholm. WSP Construction Design is one of the leading departments in Sweden in construction solutions regarding everything from building construction to industrial building. Great competencies regarding steel, wood and concrete constructions are available within the department which is well sought. Crane girders used in the industry are exposed to large loads that vary over time that includes instantaneous lifts and the crane girders movement which lead to the phenomenon fatigue in the crane girder and its ingoing welds. A control of fatigue needs to be performed after a certain lifespan measured in time which in turn is converted to a number of loadcycles. When the number of loadcycles amounts to a greater number the input welds resistance will have been reduced and the rate of utilization thereby increased. This is fatigue. Since long BKR/BSK has handled the design of crane girders with results of satisfactory that even has exceeded the costumers expectations regarding the lifespan. New demands have been set that the BKR/BSK-standard shall be rejected and replaced by the new standard of Europe named Eurocode. The Eurocode-standard is still relatively new and on the brink to replacing BKR/BSK. This opens up for many questions regarding what this transition will mean. One of these issues is what the transition will lead to regarding fatigue. This report intends to explore and clarify any discrepancies that the two different standards BKR/BSK and Eurocode differ in design regarding fatigue in crane girders. The goal of this report is thereby to compare BKR/BSK with Eurocode from a fatigue point of view with the weight of the study on input welds were fatigue clearly arises During the project, differences between BKR/BSK and Eurocode could be identified regarding treatment of fatigue dimensioning. Because of this, much time has been needed to preform calculations according to Eurocode by hand, then analyze the result and ask our internal references at WSP for further guidance. The result this report is showing is clear differences regarding the ingoing welds utilization rates.The utilization rate for the perpendicular weld at the top flange and web was calculated to a much greater value than allowed, which lead to that the chosen crane girder in this report did not reach up to the standards of Eurocode. The report is also showing that lower utilization rates were obtained when compared to the results of the BKR/BSK calculations regarding welds placed at the rail and stiffener. Another major difference that could be detected is how the number of loadcycles is being greatly reduced on a crane girder dimensioned according to BKR/BSK that is being tested according to the Eurocode standards. The report has also showed that the way of dimensioning in Eurocode is complex. Eurocode lacks descriptions regarding how to interpret its ingoing material. This places great demands on constructors that they can handle this standard and that they are being competent in how to use and apply it in a safe way. / Denna rapport har utförts åt WSP byggprojektering beläget på Arenavägen 7 i Stockholm. WSP byggprojektering är en av Sveriges ledande konstruktionsavdelningar inom konstruktionslösningar gällande allt från husbyggnad till industribyggnad. Stora kompetenser gällande stål-, trä- och betongkonstruktioner finns inom avdelningen som är väl eftertraktad. Kranbalkar inom industrin utsätts för stora laster som varierar över tid som innefattar momentana lyft och kranens rörelse vilket medför fenomenet utmattning i kranbalken och dess ingående svetsar. En utmattningskontroll behöver utföras efter en viss livslängd mätt i tid, som i sin tur omvandlas till antal lastcykler. När antalet lastcykler uppgår till ett större antal kommer de ingående svetsarnas hållfasthet reducerats och utnyttjandegraden på så vis ökat. Detta är utmattning. Länge har BKR/BSK hanterat dimensioneringen av kranbalkar med tillfredställande resultat som till och med har överstigit beställarens förväntningar gällande livslängden. Nya krav har dock kommit på att BKR/BSK-normen skall ersättas av den nya europastandarden Eurokod. Eurokod-normen är fortfarande relativt ny och är precis i den fas där den skall ersätta BKR/BSK. Detta öppnar upp för många frågor vad denna övergång kommer att betyda. En av dessa frågor är vad övergången kommer att innebära för utmattning. Denna rapport avser att undersöka och bringa klarhet i eventuella skillnader som de två olika normerna BKR/BSK och Eurokod kan ha gentemot varandra gällande dimensionering av utmattning i kranbalkar. Målet med denna rapport är därför att jämföra BKR/BSK med Eurokod ur ett utmattningsperspektiv med tyngden av undersökningen kring ingående svetsar där utmattning tydligt uppkommer. Under arbetets gång uppmärksammades skillnader mellan BKR/BSK och Eurokodens behandling av utmattningsdimensionering. Detta har lett till att väldigt mycket tid fått läggas åt att utföra handberäkningar i Eurokod för att sedan analysera det slutliga utfallet för att sedan konsultera interna referenser hos WSP för att kunna lösa problemet. Resultatet som rapporten redovisar är tydliga skillnader i svetsarnas utnyttjandegrader. Utnyttjandegraden för vinkelräta svetsen vid övre livhals beräknades till ett värde långt över det tillåtna, vilket då gjorde att den kranbalken som dimensionerades i rapporten inte kan godkännas enligt de krav som Eurokoden ställer. Rapporten visar också att lägre utnyttjandegrader har erhållits vid jämförelse med svetsar beräknade enligt BKR/BSK. Detta avser då svetsen vid rälklammer och svets vid avstyvning och överfläns. Ytterligare en stor skillnad som påvisats är hur antalet lastcykler kraftigt reduceras på ett tvärsnitt dimensionerat enligt BKR/BSK om man skulle tillämpa Eurokodens föreskrifter. Rapporten har också visat att den dimensioneringsgång som beskrivs enligt Eurokod inte är särskilt enkel. Då Eurokoden saknar beskrivning i vissa fall hur den skall tolkas så ställer det mycket stora krav på att konstruktörer utbildas inom området innan de börjar tillämpa Eurokoden.

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