Good toughness properties in base and weld material enable the use of duplex stainless steels (DSS) in critical applications. DSS offer high strength compared to common austenitic stainless steels. The high strength can be utilized to reduce the wall thickness and accordingly accomplish reduction of cost, welding time and transportation weight, contributing to ecological and energy savings. Although DSS have been used successfully in many applications the last decades, the full utilisation in pressure vessels has been restricted due to conservative design rules. The consequences of failure in a pressure vessel are often very severe and it is accordingly important to verify a high ductility and fracture toughness. In this study fracture toughness data has been generated that has been used to analyse the brittle failure model in the European pressure vessel code EN 13445. The evaluation of the results has been made successfully by the master curve analysis, previously applied to ferritic steels. The master curve analysis includes calculation of a reference temperature, which can be correlated to an impact toughness transition temperature. A correlation between fracture and impact toughness results is necessary for a practically applicable design code. The heat distribution and austenite reformation have been modelled to verify satisfactory toughness properties in the heat affected zone. A similar model was used to evaluate the nucleation and diffusional growth of sigma phase during isothermal heat treatment or continuous cooling. For future stainless steel development, the availability of satisfactory correlations between composition, microstructure and mechanical properties are essential to optimize alloy design. Stainless steel data has been analysed to find approximate relations between mechanical properties and the chemical composition, grain size, ferrite content, product thickness and solution hardening size misfit parameter. The solution hardening effect was successfully predicted by the Labusch-Nabarro relation and multiple regression analyses were used to evaluate hardening equations for stainless steel. / QC 20100920

The public transportation in Stockholm is expanding and in order to meet the new demand the amount of buses and depots will have to increase within the city. As a result, it is getting more important to evaluate and analyse the performance of bus depots in order to reduce its environmental impact. The aim of this work is to study the production and operational phase during a bus depot’s life cycle and introduce saving measures that can reduce the emission of carbon dioxide equivalents (CO2eq). This study is conducted in collaboration with Skanska and the depot chosen for this study is currently under construction and located in Charlottendal, Värmdö. A base model is created for the whole bus depot area and the environmental impact is evaluated regarding the activities and usage of materials during production and the energy usage during operation of the depot. The evaluation of the model is performed by using the calculation tools IDA ICE, Anavitor, SPIK and Excel, and the environmental impact is expressed in terms of emission of CO2eq during the lifetime of the depot, which is assumed to be 50 years.  In order to investigate how bus depots can be built to be more climate neutral and energy efficient, several saving measures are evaluated in four cases. The first two cases are focusing on optimising the usage of materials in the building process, by reducing the material groups with the highest environmental impact and considering green construction solutions. The other two cases are aiming towards enhancing the energy performance of the depot, by reducing the usage of energy according to BBR and deliberating an indoor parking place for the buses. The total emission of CO2eq from the base model is determined to be approximately 16 000 tonnes during the lifetime of the depot. About 42 percent of the environmental impact is instigated during the production phase and the rest of the emission is caused by the use of electricity and heat during operation. By considering the implemented measures it can be concluded that the largest reduction in emission can be obtained by optimising the usage of materials on the site, which is achieved by reducing two of the largest materials groups consisting of concrete and asphalt. By reducing the usage of these materials the total emission from the production phase can be reduced by approximately 9 percent and the total emissions can be reduced by up to 4 percent.  To verify the obtained results a sensitivity analysis is performed where three important parameters are investigated. The chosen parameters are; the assumption of the emission factors for the electricity and district heating mixes and the required heating demand for the buses. According to the sensitivity analysis the final results are highly related to the considered parameters. For instance, if the delivered district heating is assumed to be supplied by Fortum, which is the main distributor within Stockholm, it can be concluded that an indoor parking place for the buses is the most beneficial solution to reduce the total emissions. By building a new base hall the emissions instigated from the total heating demand can be reduced by 55 percent and the total emissions can be reduced by 25 percent. / Kollektivtrafiken i Stockholm genomgår i dagsläget en utbyggnation och för att möta det ökade behovet på transportmedel så måste antalet bussar och bussdepåer att öka i området. På grund av detta blir det mer och mer viktigt att utvärdera och analysera bussdepåernas prestanda för att kunna minska miljöpåverkan från dessa verksamheter. Syftet med detta arbete är att studera produktion- och driftfasen under en bussdepås livscykel samt presentera åtgärder som kan leda till en minskning i utsläppen av koldioxidekvivalenter (CO2ekv). Detta arbete utförs i sammarbete med Skanska och den studerade bussdepån, som ligger i Charlottendal på Värmdö, är för tillfället under konstruktion. För att kunna utvärdera den valda depån skapas en basmodell där klimatpåverkan utvärderas utifrån de aktiviteter och material som används i produktionsfasen och den energi som används under driften av depån. De beräkningsverktyg som har används i utvärderingen av depån består av IDA ICE, Anavitor, SPIK och Excel, och klimatpåverkan från depån uttrycks i ton CO2ekv under dess livslängd, vilken har antagits till 50 år. För att undersöka hur depåer kan konstrueras för att vara mer klimatneutrala och energieffektiva så utvärderas olika besparingsåtgärder i fyra fall. Fokus för de två första fallen ligger på att optimera materialanvändningen i byggprocessen, vilket inkluderar en minskning av de material som genererar i de största utsläppen samt en analys av mer miljövänliga konstruktionslösningar. De andra två fallen riktas istället mot att förbättra energiprestandan av depån genom att minska energianvändningen enligt BBR och överväga en inomhusparkering för bussarna.  De totala utsläppen från basmodellen utgör cirka 16 000 ton, där 42 procent orsakas under produktionsfasen och de resterande utsläppen kommer från driften av depån. Utifrån analysen kan man dra slutsatsen att den största minskningen av utsläpp kan åstadkommas genom att dra ner på mängden betong och asfalt i produktionsfasen. Genom att minska på dessa material kan utsläppen från produktionsfasen minskas med ungefär 9 procent och de totala utsläppen kan minskas med 4 procent. I känslighetsanalysen undersöks tre huvudsakliga parametrar som har en stor inverkan på det slutliga resultatet av beräkningarna. Dessa parametrar består av de valda energimixerna för elektricitet och fjärrvärme samt värmebehovet för bussarna. Enligt resultatet i känslighetsanalysen så är en inomhusparkering den förbättringsåtgärd som leder till den största minskningen av utsläpp. Detta resultat fås då fjärrvärmen antas levereras av Fortum, som är den största leverantören i Stockholmsområdet. Genom att investera i en ny busshall kan det totala värmebehovet för bussdepån minskas med 55 procent och det totala utsläppet med 25 procent.

<p>Commercial alloys are continuously developed to improve their performance. Therefore it is important to develop new optimisation software, which could be used in development of new materials or in materials selection. In this study the mechanical properties which are important in materials selection in mechanical design are investigated. Two types of materials are analysed, aluminium alloys and stainless steels but focus will be on the aluminium alloys.</p><p>Thermodynamic analysis has been used to evaluate the effect of the microstructure. Solid solution hardening has been successfully modelled for both aluminium alloys and stainless steels and follows the theories by Labusch and Nabarro. The precipitation hardening is most dominant for the hardenable aluminium alloys, but the non-hardenable alloys also increase their strength from precipitation hardening. The non-hardenable alloys are divided into tempers, which differ in the amount of strain hardening. This has also been modelled successfully.</p><p>Combining these fundamental results with multiple regression, models for mechanical properties have been created. Separate models are developed for wrought aluminium alloys and stainless steels. For the aluminium alloys this includes the solid solution hardening and the precipitation hardening. For the stainless steels the thickness, nitrogen content and ferrite content are included together with the solid solution hardening.</p>

Commercial alloys are continuously developed to improve their performance. Therefore it is important to develop new optimisation software, which could be used in development of new materials or in materials selection. In this study the mechanical properties which are important in materials selection in mechanical design are investigated. Two types of materials are analysed, aluminium alloys and stainless steels but focus will be on the aluminium alloys. Thermodynamic analysis has been used to evaluate the effect of the microstructure. Solid solution hardening has been successfully modelled for both aluminium alloys and stainless steels and follows the theories by Labusch and Nabarro. The precipitation hardening is most dominant for the hardenable aluminium alloys, but the non-hardenable alloys also increase their strength from precipitation hardening. The non-hardenable alloys are divided into tempers, which differ in the amount of strain hardening. This has also been modelled successfully. Combining these fundamental results with multiple regression, models for mechanical properties have been created. Separate models are developed for wrought aluminium alloys and stainless steels. For the aluminium alloys this includes the solid solution hardening and the precipitation hardening. For the stainless steels the thickness, nitrogen content and ferrite content are included together with the solid solution hardening. / QC 20101122