| 1. |
- Ståhl, Jan Eric, et al.
(författare)
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Key Performance Index for Creating an Integrated and Sustainable Academy - A University with the Ability to Meet Future Needs and Challenges Identified in Society and Industry
- 2024
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Ingår i: Moving Integrated Product Development to Service Clouds in the Global Economy - Proceedings of the 21st ISPE Inc. International Conference on Concurrent Engineering, CE 2014. - 2352-7528 .- 2352-751X. - 9781643685113 - 9781643685106 ; 52, s. 643-659
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Konferensbidrag (refereegranskat)abstract
- Key performance indexes (KPIs) in various forms have always been used in one way or another in the production and processing of raw materials. The need for KPIs was accentuated with the advent of industrialism in the western world. The way and strategy of manufacturing industrial products has been divided into several so-called developmental transformations. Primarily after the depression of the 1930s and after the Second World War, a way of working and a basic view was gradually created that has resource efficiency and goal achievement as a fundamental idea. This publication describes how KPIs can be used in higher education to create a sustainable academy to meet challenges in industry and society over time. This with a focus on sustainability and continuity as well as a strategic integration between the academy's various missions. These missions consist of teaching, research and collaboration. Furthermore, according to the Higher Education Ordinance, teaching shall rest on a scientific basis and, when appointing senior positions, equal weight shall be attached to the merits that can be linked to teaching and research. In addition to teaching and research, collaboration must be conducted with the surrounding society. Society places increasing demands on the knowledge conveyed in teaching to harmonize with current needs and to prepare for future needs and challenges. A starting point for the publication is that needs and challenges can best be met through a conscious and strategic integration between the academy's various missions. Another aspect that is highlighted in this publication is the importance of strengthening the collaboration between basic subjects and more applied and industry-related subjects, which provides renewal in the applied subjects at the same time as the basic research can be utilized at a higher rate. In an industrial perspective, a more continuous TRL scale is obtained, which provides a more effective implementation of research results. A development path that strengthens the Academy's mission areas is the principle of affiliation of personnel from industry and other sectors of society and increased admission of industrial doctoral students and other external doctoral students. In order to monitor the development of the respective mission areas of academia and its integration, the use of KPIs will be addressed. A discussion of their benefits will be highlighted but also the associated difficulties, especially when conditions change. The conducted literature study shows that there are very few or rather no found publications dealing with KPIs for the integration of the Academy's different missions. KPIs are well developed for higher education in terms of its implementation and associated economics. Corresponding published work related to KPIs in research deals primarily with conventional academic bibliometrics.
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| 2. |
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| 3. |
- Hambäck, Peter A., et al.
(författare)
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Insekter och spindlar i anlagda våtmarker : Intressanta fynd från en systematisk undersökning i Uppland och södra Halland
- 2022
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Ingår i: Entomologisk tidskrift. - 0013-886X. ; 143:1-2, s. 47-66
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Tidskriftsartikel (refereegranskat)abstract
- Wetland area has decreased dramatically compared with preindustrial times, and in manyagricultural areas almost all wetlands have been drained to gain cropland. The trend hasin recent years been reversed because society has realized the many benefits of wetlandfunctions, such as for nutrient retention and flood control. In this study we inventoried 75 wetlands in Uppland and Halland for insects and spiders with Malaise traps, pitfall traps andsuction sampling. Most included wetlands are constructed, because the main purpose was toexamine if these wetlands also can be good for arthropod diversity, but we also included somemore natural wetlands as comparison. In total, we identified more than 25,000 individualsof more than 900 species of Coleoptera, Araneae, Diptera and Heteroptera. We found onenew species for Sweden, Hilara manicata Meigen 1822, and 37 new regional records. Alarge number of species found are considered threatened or else rare. Some wetlands closeto Mälaren were particularly interesting, with three species (Hypsosinga heri (Hahn 1831),Rhaphium antennatum (Charlier 1835) and Bagous robustus Brisout de Barneville 1863)that have no records nearby during recent times. These and other species found in the studyshow that constructed wetlands can provide good habitats for arthropod biodiversity andrare species, particularly if wetland shores are grazed and trampled by cattle.
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| 4. |
- Nilsson, Magnus, et al.
(författare)
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A 9-band WCDMA/EDGE transceiver supporting HSPA evolution
- 2011
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Ingår i: [Host publication title missing]. - 0193-6530. ; , s. 366-368
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Konferensbidrag (refereegranskat)abstract
- The future of cellular radio ICs lies in the integration of an ever-increasing number of bands and channel bandwidths. This paper presents a transceiver together with the associated discrete front-end components. The transceiver supports 4 EDGE bands and 9 WCDMA bands (l-VI and Vlll-X), while the radio can be configured to simultaneously support the 4 EDGE bands and up to 5 WCDMA bands: 3 high bands (HB) and 2 low bands (LB). The RX is a SAW-less homodyne composed of a main RX and a diversity RX. To reduce package complexity with so many bands, we chose to minimize the number of ports by using single-ended RF interfaces for both RX and TX. This saves seve ral package pins, but requires careful attention to grounding. The main RX has 8 LNA ports and the diversity RX has 5, with some LNAs supporting multiple bands. On the TX side, 2 ports are used for all EDGE bands and 4 for the WCDMA bands.
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| 5. |
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| 6. |
- Sarlus, Zmar, 1984-, et al.
(författare)
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Timing and origin of the host rocks to the Malmberget iron oxide-apatite deposit, Sweden
- 2020
-
Ingår i: Precambrian Research. - : Elsevier. - 0301-9268 .- 1872-7433. ; 342
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Tidskriftsartikel (refereegranskat)abstract
- The northern Norrbotten region in Sweden hosts abundant iron-oxide apatite (IOA) deposits including Kiirunavaara, the type locality for Kiruna-type deposits, and Malmberget. Felsic and intermediate metavolcanic rocks hosting the Malmberget IOA deposit contain oscillatory zoned zircon which yield magmatic U-Pb SIMS ages of 1885±6 Ma and 1881±6 Ma, respectively. Metamorphic rims on zircon from these rocks yield 1797±7 Ma and 1775±6 Ma, respectively, and record the age of the latest Svecofennian regional metamorphic event in the Gällivare area, tentatively interpreted as regional contact metamorphism. Two granite dikes that cut the ore yield U-Pb zircon emplacement ages of 1790±6 Ma and 1791±7 Ma, respectively, overlapping with the metamorphic overgrowths, and set a lower age limit for ore formation in the Malmberget IOA deposit. Rocks hosting the Malmberget IOA deposit have an alkalic to alkali-calcic affinity with a geochemical signature that favors a continental-arc, transitional to extensional setting. These rocks are suggested to have been generated in a back-arc region, in response to subduction beneath the craton margin retreating to the SW or W. The obtained ages and geochemical signatures of these rocks coincide well with the regionally defined Kiirunavaara group rocks, hosting several other IOA deposits in northern Sweden.
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| 7. |
- Sarlus, Zmar, et al.
(författare)
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Timing of plutonism in the Gällivare area : mplications for Proterozoic crustal development in the northern Norrbotten ore district, Sweden
- 2018
-
Ingår i: Geological Magazine. - : Cambridge University Press. - 0016-7568 .- 1469-5081. ; 155:6, s. 1351-1376
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Tidskriftsartikel (refereegranskat)abstract
- Zircon ion probe (secondary-ion mass spectrometry or SIMS) data from a set of intrusive rocks emplaced in the vicinity of major ore bodies, as well as from large igneous intrusions in the Gällivare area, gave the following results: (1) the Dundret ultramafic–mafic layered complex (1883±5 Ma), the Aitik granite (1883±5 Ma), the Nautanen diorite (1870±12 Ma), the Vassaravaara ultramafic–mafic layered complex (1798±4 Ma), the Aitik dolerite (1813±9 Ma), the Bergmästergruvan and Sikträsk syenites (1795±4 Ma and 1801±3 Ma, respectively) and the Naalojärvi granite (1782±5 Ma). These data broadly fall within the ranges 1.89–1.87 Ga (early Svecofennian) and 1.80–1.78 Ga (late Svecofennian), but geochronologically allow further subdivision into pulses at 1885–1880, 1875–1870, 1800 and 1780 Ma. During these events, large layered ultramafic–mafic and felsic plutonic rocks were generated with distinct overlap in time suggesting coeval felsic–mafic magmatism. Results also indicate the presence of inherited c. 1.87 Ga zircon crystals in the plutonic rocks at 1.78 Ga, supporting reworking of the previous crust. These data indicate the importance of mantle-derived mafic underplating in the process of crustal magma generation in the region. The c. 1.88 Ga event that generated ultramafic–mafic layered complexes is tentatively suggested to have played an important role in the formation of the Aitik Cu–Au porphyry system. The later event at c. 1.80 Ga, generating voluminous mafic–felsic units, is suggested to be coupled to the regional iron-oxide-copper-gold (IOCG) overprint.
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| 8. |
- Adegoke, Olutayo, 1979-, et al.
(författare)
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Influence of laser powder bed fusion process parameters on the microstructure and cracking susceptibility of nickel-based superalloy Alloy 247LC
- 2022
-
Ingår i: Results in Materials. - : Elsevier. - 2590-048X. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Microstructures of material conditions of nickel-based superalloy Alloy 247LC fabricated using laser powder bed fusion (L-PBF) were investigated. Experiments designed in a prior study revealed the L-PBF process parameters for which the material conditions displayed a reduced susceptibility to cracking. Certain process parameters produced material conditions with an increased susceptibility to cracking. In this study, the material conditions were investigated in detail to reveal their microstructure and to determine the cause of cracking. The reason for the transition between a reduced to an increased susceptibility to cracking was examined. The results revealed solidification cracking occurred at high-angle grain boundaries. Solidification cracking may have been promoted at high-angle grain boundaries because of the undercooling contribution of the grain boundary energy. Furthermore, Si segregation was observed in the cracks. Thus, the presence of Si most likely promoted solidification cracking. It was observed that a high crack density, which occurred in the high energy density material condition, was associated with a large average grain size. The fact that certain combination of process parameters produced microstructures with a low susceptibility to cracking, indicates that reliable Alloy 247LC material may be printed using L-PBF by employing improved process parameters. © 2022
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| 9. |
- Adegoke, Olutayo, 1979-, et al.
(författare)
-
Influence of laser powder bed fusion process parameters on the microstructure of solution heat-treated nickel-based superalloy Alloy 247LC
- 2022
-
Ingår i: Materials Characterization. - : Elsevier. - 1044-5803 .- 1873-4189. ; 183
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Tidskriftsartikel (refereegranskat)abstract
- In this study, Alloy 247LC samples were built with different laser powder bed fusion (L-PBF) process parameters. The samples were then subjected to solution heat treatment at 1260 °C for 2 h. The grain size of all the samples increased significantly after the heat treatment. The relationship between the process parameters and grain size of the samples was investigated by performing a design of experiment analysis. The results indicated that the laser power was the most significant process parameter that influenced the grain height and aspect ratio. The laser power also significantly influenced the grain width. The as-built and as-built + heat-treated samples with high, medium, and low energy densities were characterized using a field emission gun scanning electron microscope equipped with an electron backscatter diffraction detector. The micrographs revealed that the cells present in the as-built samples disappeared after the heat treatment. Isolated cases of twinning were observed in the grains of the as-built + heat-treated samples. The disappearance of cells, increase in the grain size, and appearance of twins suggested that recrystallization occurred in the alloy after the heat treatment. The occurrence of recrystallization was confirmed by analyzing the grain orientation spread of the alloy, which was lower and more predominantly <1° in the as-built + heat-treated conditions than in the as-built conditions. The microhardness of the as-built + heat-treated samples were high which was plausible because γ’ precipitates were observed in the samples. However, the L-PBF process parameters had a very low correlation with the microhardness of the as-built + heat-treated samples.
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| 10. |
- Adegoke, Olutayo, et al.
(författare)
-
Influence of laser powder bed fusion process parameters on voids, cracks, and microhardness of nickel-based superalloy alloy 247LC
- 2020
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Ingår i: Materials. - 1996-1944. ; 13:17
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Tidskriftsartikel (refereegranskat)abstract
- The manufacturing of parts from nickel-based superalloy Alloy 247LC by laser powder bed fusion (L-PBF) is challenging, primarily owing to the alloy’s susceptibility to cracks. Apart from the cracks, voids created during the L-PBF process should also be minimized to produce dense parts. In this study, samples of Alloy 247LC were manufactured by L-PBF, several of which could be produced with voids and crack density close to zero. A statistical design of experiments was used to evaluate the influence of the process parameters, namely laser power, scanning speed, and hatch distance (inherent to the volumetric energy density) on void formation, crack density, and microhardness of the samples. The window of process parameters, in which minimum voids and/or cracks were present, was predicted. It was shown that the void content increased steeply at a volumetric energy density threshold below 81 J/mm3. The crack density, on the other hand, increased steeply at a volumetric energy density threshold above 163 J/mm3. The microhardness displayed a relatively low value in three samples which displayed the lowest volumetric energy density and highest void content. It was also observed that two samples, which displayed the highest volumetric energy density and crack density, demonstrated a relatively high microhardness; which could be a vital evidence in future investigations to determine the fundamental mechanism of cracking. The laser power was concluded to be the strongest and statistically most significant process parameter that influenced void formation and microhardness. The interaction of laser power and hatch distance was the strongest and most significant factor that influenced the crack density. © 2020 by the authors.
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| 11. |
- Adegoke, Olutayo, et al.
(författare)
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Laser beam powder bed fusion and post processing of alloy 247LC
- 2019
-
Ingår i: MS and T 2019 - Materials Science and Technology. - : Materials Science and Technology. - 9780873397704 ; , s. 27-34
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Konferensbidrag (refereegranskat)abstract
- Alloy 247LC is sensitive to cracking during laser beam powder bed fusion (PBF-LB) manufacturing. Post processing is thus required to close cracks and achieve desired properties. In this study, samples of Alloy 247LC were manufactured by PBF-LB and subsequently post processed by hot isostatic pressing (HIP), HIP + solution and ageing heat treatments. The microstructure was characterized. Results showed cracks in the as-built condition. Cracks were not detected after HIP. Bright microconstituents were observed in the region between the cells, mainly, because of the partitioning of Hf and Ta into the intercellular region, where they presumably form carbides. What is assumed to be oxides were prominent in the microstructure. Thermodynamic calculations showed rapid formation of ?’ precipitates in the alloy, due to the high total concentration of Al and Ta and this was linked to the high hardness values in the as-built condition. © 2019 MS&T19®
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| 12. |
- Adegoke, Olutayo
(författare)
-
Processability of Laser Powder Bed Fusion of Alloy 247LC : Influence of process parameters on microstructure and defects
- 2020
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is about laser powder bed fusion (L-PBF) of the nickel-based superalloy: Alloy 247LC. Alloy 247LC is used mainly in gas turbine blades and processing the blades with L-PBF confers performance advantage over the blades manufactured with conventional methods. This is mainly because L-PBF is more suitable, than conventional methods, for manufacturing the complex cooling holes in the blades. The research was motivated by the need for academia and industry to gain knowledge about the processability of the alloy using L-PBF. The knowledge is essential in order to eventually solve the problem of cracking which is a major problem when manufacturing the alloy. In addition, dense parts with low void content should be manufactured and the parts should meet the required performance. Thus, the thesis answered some of the important questions related to process parameter-microstructure-defect relationships.The thesis presented an introduction in chapter 1. A literature review was made in chapter 2 to 4. In chapter 2, the topic of additive manufacturing was introduced followed by an overview of laser powder bed fusion. Chapter 3 focused on superalloys. Here, a review was made from the broader perspective of superalloys but was eventually narrowed down to the characteristics of nickelbased superalloys and finally Alloy 247LC. Chapter 4 reviewed the main research on L-PBF of Alloy 247LC. The methodology applied in the thesis was discussed in chapter 5. The thesis applied statistical design of experiments to show the influence of process parameters on the defects and microstructure, so a detail description of the method was warranted. This was given at the beginning of chapter 5 and followed by the description of the L-PBF manufacturing and the characterization methods. The main results and discussions, in chapter 6, included a preliminary investigation on how the process parameters influenced the amount of discontinuity in single track samples. This was followed by the results and discussions on the investigation of voids, cracks and microhardness in cube samples (detail presentation was given in the attached paper B). Finally, the thesis presented results of the microstructure obtainable in L-PBF manufactured Alloy 247LC. The initial results of the microstructure investigation were presented in paper A.
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| 13. |
- Adegoke, Olutayo, 1979-
(författare)
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Processability of Laser Powder Bed Fusion of Alloy 247LC-Influence of process parameters on microstructure and defects
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is about laser powder bed fusion (L-PBF) of the nickel-basedsuperalloy Alloy 247LC. Alloy 247LC is mainly used in gas turbine blades and processing the blades with L-PBF may confer performance advantage over the blades manufactured with conventional methods. This is mainly because L-PBFis more suitable, than conventional methods, for manufacturing the complex cooling holes in the blades. The research was motivated by the need for academia and industry to gain knowledge about the processability of the alloy using L-PBF. The knowledge is essential to eventually solve the problem of cracking encountered when processing the alloy. In addition, dense parts with low void content should be processed and the microstructure and properties should meett he required performance. Heat-treatment is usually performed to acquire final properties, so it is also of interest to study this aspect. Thus, the thesis answered some of the important questions related to process parameter-microstructure- property relationships.
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| 14. |
- Adegoke, Olutayo, et al.
(författare)
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Review of laser powder bed fusion of gamma-prime-strengthened nickel-based superalloys
- 2020
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Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 10:8
-
Tidskriftsartikel (refereegranskat)abstract
- This paper reviews state of the art laser powder bed fusion (L-PBF) manufacturing of γ′ nickel-based superalloys. L-PBF resembles welding; therefore, weld-cracking mechanisms, such as solidification, liquation, strain age, and ductility-dip cracking, may occur during L-PBF manufacturing. Spherical pores and lack-of-fusion voids are other defects that may occur in γ′-strengthened nickel-based superalloys manufactured with L-PBF. There is a correlation between defect formation and the process parameters used in the L-PBF process. Prerequisites for solidification cracking include nonequilibrium solidification due to segregating elements, the presence of liquid film between cells, a wide critical temperature range, and the presence of thermal or residual stress. These prerequisites are present in L-PBF processes. The phases found in L-PBF-manufactured γ′-strengthened superalloys closely resemble those of the equivalent cast materials, where γ, γ′, and γ/γ′ eutectic and carbides are typically present in the microstructure. Additionally, the sizes of the γ′ particles are small in as-built L-PBF materials because of the high cooling rate. Furthermore, the creep performance of L-PBF-manufactured materials is inferior to that of cast material because of the presence of defects and the small grain size in the L-PBF materials; however, some vertically built L-PBF materials have demonstrated creep properties that are close to those of cast materials.© 2020 by the authors. Licensee MDPI, Basel, Switzerland.
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| 15. |
- Adegoke, Olutayo, et al.
(författare)
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Scanning electron microscopy and atom probe tomography characterization of laser powder bed fusion precipitation strengthening nickel-based superalloy
- 2023
-
Ingår i: Micron. - 0968-4328 .- 1878-4291. ; 171
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Tidskriftsartikel (refereegranskat)abstract
- Atom probe tomography (APT) was utilized to supplement scanning electron microscopy (SEM) characterizationof a precipitation strengthening nickel-based superalloy, Alloy 247LC, processed by laser powder bed fusion (LPBF). It was observed that the material in the as-built condition had a relatively high strength. Using both SEMand APT, it was concluded that the high strength was not attributed to the typical precipitation strengtheningeffect of γ’. In the absence of γ’ it could be reasonably inferred that the numerous black dots observed in thecells/grains with SEM were dislocations and as such should be contributing significantly to the strengthening.Thus, the current investigation demonstrated that relatively high strengthening can be attained in L-PBF even inthe absence of precipitated γ’. Even though γ’ was not precipitated, the APT analysis displayed a nanometer scalepartitioning of Cr that could be contributing to the strengthening. After heat-treatment, γ’ was precipitated and itdemonstrated the expected high strengthening behavior. Al, Ta and Ti partitioned to γ’. The strong partitioningof Ta in γ’ is indicative that the element, together with Al and Ti, was contributing to the strain-age crackingoccurring during heat-treatment. Cr, Mo and Co partitioned to the matrix γ phase. Hf, Ta, Ti and W were found inthe carbides corroborating previous reports that they are MC.
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| 16. |
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| 17. |
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| 18. |
- Andersson, Joel B. H., et al.
(författare)
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Structural controls on sulphide (re)-distribution in Kiruna
- 2019
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Ingår i: Proceedings of the 15th SGA Biennial Meeting, 27-30 August. - : University of Glasgow Publicity Services. ; , s. 115-118
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Konferensbidrag (refereegranskat)abstract
- In this study, we investigate a potential structural control on sulphide distribution in phyllite from the Kiruna area, northern Norrbotten, Sweden. We use X-ray tomography and X-ray fluorescence analyzed in tandem on a 40 cm section of oriented drill core. Scanning Electron Microscopy and Energy Dispersive Spectrometry are used in combination with optical microscopy to analyze mineralogy and microstructures. The results show that sulphides are distributed along So bedding planes, re-distributed along S-2 axial planar cleavage planes, and trapped by F-2-hinge zones and shear bands visible as elevated sulphide concentrations. The results of this study underlines the strength of X-ray tomography to image 3D geological structures and their relation to mineral distributions.
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| 19. |
- Andersson, Joel B.H., et al.
(författare)
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Structural Evolution of the Central Kiruna Area, Northern Norrbotten, Sweden : Implications on the Geologic Setting Generating Iron Oxide-Apatite and Epigenetic Iron and Copper Sulfides
- 2021
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Ingår i: Economic geology and the bulletin of the Society of Economic Geologists. - : Society of Economic Geologists. - 0361-0128 .- 1554-0774. ; 116:8, s. 1981-2009
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Tidskriftsartikel (refereegranskat)abstract
- To guide future exploration, this predominantly field based study has investigated the structural evolution of the central Kiruna area, the type locality for iron oxide-apatite deposits that stands for a significant amount of the European iron ore production. Using a combination of geologic mapping focusing on structures and stratigraphy, petrography with focus on microstructures, X-ray computed tomography imaging of sulfide-structure relationships, and structural 2D-forward modeling, a structural framework is provided including spatial-temporal relationships between iron oxide-apatite emplacement, subeconomic Fe and Cu sulfide mineralization, and deformation. These relationships are important to constrain as a guidance for exploration in iron oxide-apatite and iron oxide copper-gold prospective terrains and may help to understand the genesis of these deposit types. Results suggest that the iron oxide-apatite deposits were emplaced in an intracontinental back-arc basin, and they formed precrustal shortening under shallow crustal conditions. Subsequent east-west crustal shortening under greenschist facies metamorphism inverted the basin along steep to moderately steep E-dipping structures, often subparallel with bedding and lithological contacts, with reverse, oblique to dip-slip, east-block-up sense of shears. Fe and Cu sulfides associated with Fe oxides are hosted by structures formed during the basin inversion and are spatially related to the iron oxide-apatite deposits but formed in fundamentally different structural settings and are separated in time. The inverted basin was gently refolded and later affected by hydraulic fracturing, which represent the last recorded deformation-hydrothermal events affecting the crustal architecture of central Kiruna.
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| 20. |
- Andersson, Joel B.H., et al.
(författare)
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The tectonic overprint on the Per Geijer apatite iron ores in Kiruna, northern Sweden
- 2017
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Ingår i: Mineral Resources to Discover. - : Society for Geology Applied to Mineral Deposits. - 9782981689801 ; , s. 903-906
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Konferensbidrag (refereegranskat)abstract
- This ongoing project focusses on the structural evolution of the Per Geijer apatite iron ores in Kiruna, northern Sweden. The Per Geijer iron ores are situated in a NNE-SSW trending shear zone. This study indicate that the shear zone was active during D2 E-W compression giving rise to dip-slip and oblique slip components. The ductile fabric is overprinted by brittle structures carrying Cu, possibly representing traces of a separate Iron Oxide Copper Gold event in northern Norrbotten.
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| 21. |
- Andersson, Joel B.H., et al.
(författare)
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U-Pb zircon-titanite-apatite age constraints on basin development and basin inversion in the Kiruna mining district, Sweden
- 2022
-
Ingår i: Precambrian Research. - : Elsevier. - 0301-9268 .- 1872-7433. ; 372
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Tidskriftsartikel (refereegranskat)abstract
- To constrain the tectonothermal evolution of the type locality for iron oxide-apatite deposits, we have obtained U-Pb zircon, titanite, and apatite age data for the Kiruna mining district in northernmost Sweden. The results indicate that the host basin initiated in an overall extensional regime as indicated by the deposition of alluvial conglomerates and greywackes. A volcanic intercalation in a conglomerate unit northwest of the Luossavaara iron oxide-apatite deposit yields a U-Pb zircon age of 1887 ± 3 Ma representing the timing of the earliest Orosirian volcanism in the central Kiruna mining district coinciding with the onset of basin development. In-situ analysis of titanite on hydrothermally altered fracture planes within a cataclastic fault damage zone (c. 270 m from the fault core system associated to the Luossavaara iron oxide-apatite deposit) yields complex U-Pb data. Applying a strict discordance filter yields a 207Pb/206Pb age of 1889 ± 26 Ma. The age implies that the fault probably has a syn-volcanic origin and that syn-volcanic faults may have played an important role during iron ore emplacement. The mineralized basin was subsequently buried and metamorphosed under upper greenschist-facies conditions and later tectonically exhumed and cooled below the apatite closure temperature at 1805 ± 26 Ma indicated by apatite from the Nukutus iron oxide-apatite deposit. Basin inversion is temporally constrained by syn-tectonic titanite as part of sodic-calcic + Fe + Cl hydrothermal alteration along a brittle-ductile reverse shear zone to the east of the study area. Titanite grains that show sector and oscillatory zoning yield an age of 1812 ± 3 Ma, which we interpret as the onset of basin inversion. Homogeneous (relatively unzoned) titanite in the same sample yields an age of 1802 ± 8 Ma, tentatively indicating that the tectonothermal activity lasted up to c. 20 m.y.
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| 22. |
- Andersson, Joel, et al.
(författare)
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CasADi -- A symbolic package for automatic differentiation and optimal control
- 2012
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Ingår i: Recent Advances in Algorithmic Differentiation. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 9783642300226 ; , s. 297-307
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Konferensbidrag (refereegranskat)abstract
- We present CasADi, a free, open-source software tool for rapid, yet efficient solution of optimization problems in general and dynamic optimization problems in particular. To the developer of algorithms for numerical optimization and to the advanced user of such algorithms, it offers a level of abstraction which is notably lower, and hence more flexible, than that of algebraic modeling languages such as AMPL or GAMS, but higher than working with a conventional automatic differentiation (AD) tool. CasADi is best described as a minimalistic computer algebra system (CAS) implementing automatic differentiation in eight different flavors. Similar to algebraic modelling languages, it includes high-level interfaces to state-of-the-art numerical codes for nonlinear programming, quadratic programming and integration of differential-algebraic equations. CasADi is implemented in self-contained C++ code and contains full-featured front-ends to Python and Octave for rapid prototyping. In this paper, we show how CasADi can be used for optimal control using either a collocation approach or a shooting approach.
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| 23. |
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| 24. |
- Andersson, Joel, et al.
(författare)
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Dynamic optimization with CasADi
- 2012
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Ingår i: IEEE 51st Annual Conference on Decision and Control (CDC), 2012. - 0743-1546. - 9781467320658 ; , s. 681-686
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Konferensbidrag (refereegranskat)abstract
- We demonstrate how CasADi, a recently devel- oped, free, open-source, general purpose software tool for nonlinear optimization, can be used for dynamic optimization in a flexible, interactive and numerically efficient way. CasADi is best described as a minimalistic computer al- gebra system (CAS) implementing automatic differentiation (AD) in eight different flavors. Similar to algebraic modeling languages like AMPL or GAMS, it includes high-level interfaces to state-of-the-art numerical codes for nonlinear program- ming, quadratic programming and integration of differential- algebraic equations. CasADi is implemented in self-contained C++ code and contains full-featured front-ends to Python and Octave for rapid prototyping. In this paper, we discuss CasADi from the perspective of the developer or advanced user of algorithms for dynamic optimization for the first time, leaving out details on the implementation of the tool. We demonstrate how the tool can be used to model highly complex dynamical systems directly or import existing models formulated in the algebraic modeling language AMPL or the physical modeling language Modelica. Given this symbolic representation of the process models, the resulting optimal control problem can be solved using a vari- ety of methods, including transcription methods (collocation), methods with embedded integrators (multiple shooting) as well as indirect methods.
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| 25. |
- Andersson, Joel, 1981-, et al.
(författare)
-
Effect of Different Solution Heat Treatments on the Hot Ductility of Superalloys : Part 3 - Waspaloy
- 2013
-
Ingår i: Materials Science and Technology. - 0267-0836 .- 1743-2847. ; 29:1, s. 43-53
-
Tidskriftsartikel (refereegranskat)abstract
- The susceptibility to heat affected zone cracking of Waspaloy has been investigated in terms of its hot ductility, measured as the reduction of area (RA). Gleeble testing with on-heating as well as on-cooling test cycles was carried out to illuminate the influence of different 4 h solution heat treatments between 996 and 1080°C. A ductility maximum of between 80 and 90%RA was found at 1050–1100°C for all conditions in the on-heating tests. Although the different heat treatment conditions showed similar macrohardness, the particle size and distribution of the γ′ and M23C6 phases differed, which significantly affected the on-heating ductility in the lower temperature test region. The ductile to brittle transition was initiated at 1100°C in the on-heating testing with indications of grain boundary liquation at the higher test temperatures. Ductility recovery, as measured in the on-cooling tests from 1240°C, was very limited with <30%RA for all conditions and test temperatures except for the 1080°C/4 h treatment, which exhibited 60%RA at 980°C.
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| 26. |
- Andersson, Joel, 1981-, et al.
(författare)
-
Effect of solution heat treatments on superalloys : Part 1 – alloy 718
- 2012
-
Ingår i: Materials Science and Technology. - : Taylor & Francis Group. - 0267-0836 .- 1743-2847. ; 28:5, s. 609-619
-
Tidskriftsartikel (refereegranskat)abstract
- The hot ductility as measured by Gleeble testing of Alloy 718 at four different solution heat treatments (954°C/15 h, 954°C/1 h, 982°C/1 h and 1050°C/3 h+954°C/1 h) has been investigated. It is concluded that constitutional liquation of NbC assisted by δ phase takes place and deteriorates the ductility. Parameters established by analysing the ductility dependence on temperature indicate a reduced weldability of the material in the coarse grain size state (ASTM 3) while indicating an increased weldability when containing a large amount of δ phase due to a grain boundary pinning effect. The accumulation of trace elements during grain growth at the highest temperature is believed to be the cause for the observed reduced on-cooling ductility.
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| 27. |
- Andersson, Jonathan, et al.
(författare)
-
Estimating the cold-induced brown adipose tissue glucose uptake rate measured by 18F-FDG PET using infrared thermography and water-fat separated MRI
- 2019
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Brown adipose tissue (BAT) expends chemical energy to produce heat, which makes it a potential therapeutic target for combating metabolic dysfunction and overweight/obesity by increasing its metabolic activity. The most well-established method for measuring BAT metabolic activity is glucose uptake rate (GUR) measured using 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET). However, this is expensive and exposes the subjects to potentially harmful radiation. Cheaper and safer methods are warranted for large-scale or longitudinal studies. Potential alternatives include infrared thermography (IRT) and magnetic resonance imaging (MRI). The aim of this study was to evaluate and further develop these techniques. Twelve healthy adult subjects were studied. The BAT GUR was measured using 18F-FDG PET during individualized cooling. The temperatures of the supraclavicular fossae and a control region were measured using IRT during a simple cooling protocol. The fat fraction and effective transverse relaxation rate of BAT were measured using MRI without any cooling intervention. Simple and multiple linear regressions were employed to evaluate how well the MRI and IRT measurements could estimate the GUR. Results showed that both IRT and MRI measurements correlated with the GUR. This suggest that these measurements may be suitable for estimating the cold-induced BAT GUR in future studies.
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| 28. |
- Andersson, Joel, et al.
(författare)
-
Evolution of structures and hydrothermal alteration in a Palaeoproterozoic supracrustal belt : Constraining paired deformation–fluid flow events in an Fe and Cu–Au prospective terrain in northern Sweden
- 2020
-
Ingår i: Solid Earth. - : Copernicus publications. - 1869-9510 .- 1869-9529. ; 11:2, s. 547-578
-
Tidskriftsartikel (refereegranskat)abstract
- An approximately 90 km long Palaeoproterozoic supracrustal belt in the northwestern Norrbotten ore province (northernmost Sweden) was investigated to characterize its structural components, assess hydrothermal alteration–structural geology correlations, and constrain a paired deformation–fluid flow evolution for the belt. New geological mapping of five key areas (Eustiljåkk, Ekströmsberg, Tjårrojåkka, Kaitum West, and Fjällåsen–Allavaara) indicates two major compressional events (D1 and D2) have affected the belt, with each associated with hydrothermal alteration types typical for iron oxide–apatite and iron oxide Cu–Au systems in the region. Early D1 generated a regionally distributed, penetrative S1 foliation and oblique reverse shear zones that show a southwest-block-up sense of shear that formed in response to NE–SW crustal shortening. Peak regional metamorphism at epidote–amphibolite facies broadly overlaps with this D1 event. Based on overprinting relationships, D1 is associated with regional scapolite ± albite, magnetite + amphibole, and late calcite alteration of mafic rock types. These hydrothermal mineral associations linked to D1 structures may form part of a regionally pervasive evolving fluid flow event but are separated in this study by crosscutting relationships.During D2 deformation, folding of S0–S1 structures generated F2 folds with steeply plunging fold axes in low-strain areas. NNW-trending D1 shear zones experienced reverse dip-slip reactivation and strike-slip-dominated movements along steep, E–W-trending D2 shear zones, producing brittle-plastic structures. Hydrothermal alteration linked to D2 structures is a predominantly potassic–ferroan association comprising K-feldspar ± epidote ± quartz ± biotite ± magnetite ± sericite ± sulfides. Locally, syn- or post-tectonic calcite is the main alteration mineral in D2 shear zones that intersect mafic rocks. Our results highlight the importance of combining structural geology with the study of hydrothermal alterations at regional to belt scales to understand the temporal–spatial relationship between mineralized systems. Based on the mapping results and microstructural investigations as well as a review of earlier tectonic models presented for adjacent areas, we suggest a new structural model for this part of the northern Fennoscandian Shield. The new model emphasizes the importance of reactivation of early structures, and the model harmonizes with tectonic models presented by earlier workers based mainly on petrology of the northern Norrbotten area.
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| 29. |
- Andersson, Johan, et al.
(författare)
-
Extracting Simulation Models from Complex Embedded Real-Time Systems
- 2006
-
Ingår i: Proceedings of the 2006 International Conference on Software Engineering Advances, ICSEA'06, Tahiti, French Polynesia. - 0769527035 ; , s. Article number 4031792-
-
Konferensbidrag (refereegranskat)abstract
- A modeling process is presented for extracting timingaccurate simulation models from complex embedded real-time systems. The process is supported by two complementary methods for tool-supported model extraction, Model Synthesis and Hybrid Model Extraction. The generated models enable impact analysis for complex real-time systems with respect to dynamic system properties, such as timing and resource usage. This can make software maintenance more predictable with respect to time-to-market and development costs, since timing errors can be identified early and avoided. The contribution of the paper is the modeling process, the Hybrid Model Extraction method and an interactive modeling tool, MASS, designed to support Hybrid Model Extraction of large implementations in C.
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| 30. |
- Andersson, Joel, 1981-
(författare)
-
Fabrication and Weldability Aspects of Ni- and Ni–Fe Based Superalloys : A Review
- 2023
-
Ingår i: Proceedings of the 10th International Symposium on Superalloy 718 and Derivatives. - : Springer Cham. - 9783031274473 - 9783031274497 ; , s. 659-696
-
Konferensbidrag (refereegranskat)abstract
- Superalloys are commonly used in structural components of aero-engines. Superalloys in general, Ni- and Ni–Fe-based superalloys, belong to an important group of materials used in aerospace applications. Fabrication and associated weldability aspects of structural components for the hot section of aero-engine gas turbines continue to be of high importance to the manufacturing industry within this discipline. Cracking and specifically hot cracking as well as strain age cracking is a serious concern during the welding and additive manufacturing (AM) of these structural components. The cracking phenomena can occur during welding, AM or subsequent heat treatment of precipitation-hardening superalloys. The cracking behaviour can be influenced by several factors, i.e., chemical composition in terms of hardening elements and impurities, the microstructure of base material, and weld zone, together with corresponding welding, AM and post-treatment process parameters. This paper provides a review of Ni- and Ni–Fe-based superalloys concerning fabrication and weldability aspects within the context of structural components of aero-engines. Also, the paper offers insight and analyses to research publication data of welding and AM of superalloys in the context of annual publication developed over the years as well as specific contributions from countries, affiliations, and specific researchers.
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| 31. |
- Andersson, Joel Håkan, 1981, et al.
(författare)
-
Effect of different solution heat treatments on hot ductility of superalloys Part 2-Allvac 718Plus
- 2012
-
Ingår i: Materials Science and Technology. - : Taylor & Francis Group. - 1743-2847 .- 0267-0836. ; 28:6, s. 733-741
-
Tidskriftsartikel (refereegranskat)abstract
- The hot ductility of Allvac 718Plus for different solution heat treatments (954 degrees C-15 h, 954 degrees C-1 h, 982 degrees C-1 h and 1050 degrees C-3 h+954 degrees C-1 h) has been investigated using Gleeble testing. Substantial variations in the microstructure among the heat treatments affected the Gleeble test hot ductility only to a very limited extent. Constitutional liquation of the NbC phase was found to be the main cause for the poor ductility at high testing temperatures in the on-heating cycle as well as at the lower temperatures on-cooling. Grain boundary delta phase was seen to assist the constitutional liquation of the NbC phase. Based on established evaluation criteria for Gleeble ductility testing, a ranked indicator for weldability is suggested.
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| 32. |
- Andersson, Joel Håkan, 1981, et al.
(författare)
-
Effect of solution heat treatments on superalloys Part 1 - alloy 718
- 2012
-
Ingår i: Materials Science and Technology. - : Informa UK Limited. - 1743-2847 .- 0267-0836. ; 28:5, s. 609-619
-
Tidskriftsartikel (refereegranskat)abstract
- The hot ductility as measured by Gleeble testing of Alloy 718 at four different solution heat treatments (954 degrees C/15 h, 954 degrees C/1 h, 982 degrees C/1 h and 1050 degrees C/3 h+954 degrees C/1 h) has been investigated. It is concluded that constitutional liquation of NbC assisted by delta phase takes place and deteriorates the ductility. Parameters established by analysing the ductility dependence on temperature indicate a reduced weldability of the material in the coarse grain size state (ASTM 3) while indicating an increased weldability when containing a large amount of delta phase due to a grain boundary pinning effect. The accumulation of trace elements during grain growth at the highest temperature is believed to be the cause for the observed reduced on-cooling ductility.
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| 33. |
- Andersson, Joel Håkan, 1981, et al.
(författare)
-
Hip-densification of alloy 718 and ati 718Plus®
- 2014
-
Ingår i: 8th International Symposium on Superalloy 718 and Derivatives 2014; Pittsburgh; United States; 28 September 2014 through 1 October 2014. - Hoboken, NJ, USA : John Wiley & Sons, Inc.. - 9781634396424 ; , s. 425-435
-
Konferensbidrag (refereegranskat)abstract
- Cast Alloy 718 and ATI 718Plus® have been investigated to disclose their ability to develop Hot Isostatic Pressing (HIP) porosity which may form as a consequence of the casting process. Artificial defects were manufactured in cast Alloy 718 and ATI 718Plus® block and sealed by electron beam welding prior to the HIP treatment which was carried out at three different temperatures, namely; 1120 °C, 1165 °C, and 1190 °C at a pressure of 100 MPa. It was seen that there are no significant difference in the ability to heal pores in between cast Alloy 718 and ATI 718Plus®. No major difference in between the three different temperatures were disclosed whereas the size of the pore seem to have the biggest impact on the ability to heal, which was supported by careful SEM characterization and by simplified calculations considering two different sizes of pores.
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| 34. |
- Andersson, Joel Håkan, 1981
(författare)
-
Hot Cracking and Grain Boundary Weaknesses of Nickel - Based Superalloys
- 2008
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Abstract Grain boundary weaknesses of nickel-based superalloys not only materialize during service in the hot turbine engine sections but also during the weld manufacturing. The performance, in this respect, of the most commonly used alloys at Volvo Aero Corporation (VAC), 718 and the higher temperature capacity Waspaloy, are therefore the main subjects for this thesis. The emerging Allvac 718® PLUSTM (718 Plus) is also included due to the prospect of replacing the expensive Waspaloy. The overall emphasis is on weldability through Varestraint testing but limited work was initially carried out on notch rupture sensitivity of 718 Plus.The notch rupture testing of 718Plus emphasized the importance of the secondary phases like delta-phase in the grain boundaries.Hot cracks were observed in all alloys with re-solidified products on the liquated and re-solidified grain boundaries. Grain boundary liquation and segregation of alloying elements was considered to be the primary reason for liquation of HAZ grain boundaries which caused cracking.Evidence of constitutional liquation of Nb rich MC type carbides in alloy 718 and 718 Plus were found in the region adjacent to the fusion zone and also on the cracked grain boundaries. The resolidified products along the hot cracks consisted of γ + MC type carbide and γ + Laves eutectics.
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| 35. |
- Andersson, Joel Håkan, 1981, et al.
(författare)
-
Investigation of Homogenization and its Influence on the Repair Welding of Cast Allvac 718Plus
- 2010
-
Ingår i: Proceedings of The 7th International Symposium on Superalloy 718 and Derivatives, TMS (The Minerals, Metals and Materials Society). - Hoboken, NJ, USA : John Wiley & Sons, Inc.. - 9781617827709 ; 1, s. 439-454, s. 439-454
-
Konferensbidrag (refereegranskat)abstract
- Heat treatment experiments have been carried out to bring understanding to the efficacy of different temperatures and dwell times on the degree of homogenization of the cast Allvac 718Plus alloy which is prone to segregation mainly due to its high content of niobium. The effect of homogenization on weld repair was also examined. The homogenization heat treatment temperatures ranged from 1050°C to 1200°C with 1hr, 5 hrs and 10 hrs dwell times. The degree of homogenization was measured as the reduction of the amount of Laves phase by manual point counting in an optical microscope at high magnification. Longer range, interdendritic, patterns were established through line scan EDS analysis in SEM. It was found that short time (1hr) does not significantly reduce the amount of Laves phase whereas 5 hrs and 10hrs are much more efficient. Interdendritic homogenization does not occur to any measurable extent even at the highest temperature and longest dwell time (1200°C-10hrs) which was also reflected in bulk macro Vickers hardness tests.In the weld repair tests, one of the most homogenized material conditions (1125°C-5hrs +1200°C-10hrs) turned out to be the most prone to cracking while the number of weld cracks after a moderate homogenization heat treatment (1125°C-5hrs) was much smaller .
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| 36. |
- Andersson, Joel Håkan, 1981, et al.
(författare)
-
Repair welding of wrought superalloys: Alloy 718, Allvac 718Plus and Waspaloy
- 2012
-
Ingår i: Science and Technology of Welding and Joining. - 1743-2936 .- 1362-1718. ; 17:1, s. 49-59
-
Tidskriftsartikel (refereegranskat)abstract
- The ability to weld repair three precipitation hardening superalloys, Alloy 718, Allvac 718Plus and Waspaloy, with GasTungsten Arc Welding is compared in this study. Four different solution heat treatment conditions for each material were examined; Alloy 718 and Allvac 718Plus heat treated at 954 °C-1 h, 982 °C-1 h, 954 °C-15 h and 1020 °C-1 h and Waspaloy for 4 h at 996 °C, 1010 °C, 1040 °C and at 1080 . By metallography, the total number of cracks was evaluated both in the HAZ and in the FZ which made it possible to consistently rate the repair weldability of these three materials. Alloy 718 was significantly the best one with Allvac 718Plus slightly better than Waspaloy. As expected, the solution heat treatment conditions only affected the HAZ cracking behavior.
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| 37. |
- Andersson, Joel Håkan, 1981
(författare)
-
Solidification Cracking of Alloy Allvac 718Plus and Alloy 718 at Transvarestraint Testing
- 2008
-
Ingår i: EPD Congress 2008, TMS, ed. S. M. Howard, 2008.. ; , s. 157-169
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Allvac 718Plus is a newly developed superalloy with a good potential for use in fabricatedaircraft engine structures when service temperatures exceed 650°C; the limit for standard alloy718. Fabrication involves welding, where cracking usually is a prohibitive factor. Comparison ofthe solidification cracking behavior between these two alloys was made by Transvarestrainttesting. It was shown that the total amount of cracking was significantly lower for 718Plus alloy,which was associated with a lower amount of γ/Laves or γ/NbC eutectic-type constituents. Thisin turn is believed to be due to the lower iron content of the Allvac 718Plus material. Theanalysis of alloying element segregation both within primary dendrite and interdendriticconstituents clearly indicates that the segregation of Nb is the controlling factor in determiningthe final solidification microstructure in these alloys. The Nb concentrations of these constituentsare significantly higher compared to the bulk alloy concentration. This was confirmed by theSEM-EDS analysis and calculations assessed with JMatPro, the latter also indicated that alloy718 is more prone to form Laves and NbC eutectic-type constituents compared to Allvac 718Plusmaterial.
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| 38. |
- Andersson, Joel Håkan, 1981, et al.
(författare)
-
Solidification of alloy 718, ati 718Plus® and waspaloy
- 2014
-
Ingår i: 8th International Symposium on Superalloy 718 and Derivatives 2014. - Hoboken, NJ, USA : John Wiley & Sons, Inc.. - 9781634396424 ; , s. 181-192
-
Konferensbidrag (refereegranskat)abstract
- Alloy 718, ATI 718Plus® and Waspaloy have been investigated in terms of what their respective solidification process reveals. Differential thermal analysis was used to approach the task together with secondary electron and back scattered electron detectors equipped with an energy dispersive X-ray spectroscopy detector. These experimental methods were used to construct pseudo binary phase diagrams that could aid in explaining solidification as well as liquation mechanisms in processes such as welding and casting. Furthermore, it was seen that Waspaloy has the smallest solidification range, followed by Alloy 718, and finally ATI 718Plus® possessing the largest solidification interval in comparison.
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| 39. |
- Andersson, Joel Håkan, 1981
(författare)
-
Weldability of Ni-based superalloys
- 2014
-
Ingår i: 8th International Symposium on Superalloy 718 and Derivatives 2014; Pittsburgh; United States; 28 September 2014 through 1 October 2014. - : John Wiley & Sons, Inc.. - 9781634396424 ; , s. 249-262
-
Konferensbidrag (refereegranskat)abstract
- This paper reviews the inherent weldability of precipitation hardening Ni-based superalloys commonly used in structural components of aircraft engines. Weldability often refers to alloys resistant to cracking during welding which for superalloys is difficult to comprehend since specific liquation and cracking mechanism may differ in this class of materials. A new procedure of evaluating the weldability as well as susceptibility towards strain age cracking of these alloys is proposed in which standard metallographic examinations are used to understand the cracking mechanisms in parallel with systematic ductility measurements such as Varestraint or Gleeble testing.
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| 40. |
- Andersson, Joel Håkan, 1981
(författare)
-
Weldability of Precipitation Hardening Superalloys – Influence of Microstructure
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Superalloys and in particular the precipitation hardened Ni-based superalloys havealways been used extensively in the hot sections of jet engines. Large hot structuralengine components with complex geometry have preferably been cast as single piececomponents since the large scale vacuum investment casting process becameavailable about fifty years ago. However, a recent trend is to cast smaller pieces whichcan be joined with sheet or forged parts to fabricate structural components. Therationale for this fabrication strategy is the possibility to save weight by the use of higherstrength wrought material, where geometry allows, and join these wrought parts withcast material where complex geometry is needed and where the demand for strength ismoderate. One of the major challenges using this strategy is the obvious fact thatnumerous welds must be made which requires the fundamental understanding, notleast metallurgical, of how different materials may be joined by specific weldingprocesses.The main objective of this research has, for this reason, been to examine and interpretthe weldability of precipitation hardened superalloys from a metallurgical standpoint.Two newly developed superalloys Allvac® 718PlusTM and Haynes® 282® are comparedwith the two well established Alloy 718 and Waspaloy. The understanding of theinfluence of secondary phases such as carbides and δ phase in the microstructure wasaddressed by systematic hot ductility testing (Gleeble) and by weldability testing(Varestraint). The effect of secondary phases were also analysed through practicalwelding as by electron beam welding (EBW), and by gas tungsten arc welding (GTAW).The research showed that all the techniques used (Varestraint testing, Gleeble testing,DSC thermal analysis and welding (GTAW repair and EBW)) in studying the weldabilityindependently provided important knowledge and most importantly that a combination ofthe results from these different techniques were necessary for the understanding of theweldability of these four alloys. From a microstructural point of view it has been possibleto show that δ phase contrary to what has generally been assumed improves theweldability due to its ability to inhibit grain growth and to assist in the healing of cracks.For future research, a new modified weldability testing method was developed where itis possible to perform Varestraint, Transvarestraint and spot-varestraint testing at ramspeeds from 15 to 300 mm/s using GTAW, plasma arc welding and laser welding.
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| 41. |
- Andersson, Joel, 1981-, et al.
(författare)
-
HIP-Densification of Alloy 718 and ATI 718Plus
- 2014
-
Ingår i: 8th International Symposium on Superalloy 718 and Derivatives. - Hoboken, NJ, USA : John Wiley & Sons. - 9781119016809 - 9781119016854 ; , s. 425-436
-
Konferensbidrag (refereegranskat)
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| 42. |
- Andersson, Joel, 1981-, et al.
(författare)
-
Hot Cracking of Allvac 718Plus, Alloy 718 and Waspaloy at Varestraint Testing
- 2008
-
Ingår i: 4th International Symposium on Aerospace Materials and Manufacturing Processes. - Montreal : Canadian Institute of Mining, Metallurgy and Petroleum. - 9781617386169 ; , s. 401-413, s. 401-413
-
Konferensbidrag (refereegranskat)abstract
- Varestraint testing together with DSC and SEM-EDX analyses have been performed as means of investigating the hot cracking susceptibility of Allvac 718Plus, alloy 718 and Waspaloy. The solidification sequences in Allvac 718Plus and alloy 718 were very similar to each other starting by an initial solidification of the gamma phase, gamma/MC reaction at around 1260°C and then finally ending the sequence by gamma/Laves eutectic reaction at around 1150°C. Waspaloy had the same solidification sequence, except no Laves phase formation takes place, and solidification started at a somewhat higher temperature as compared to alloy 718 and the solidification sequence ends by a gamma/MC reaction at around 1245°C. The total amount of hot cracking in Waspaloy was shown to be much less than that in alloy 718 and in Allvac 718Plus which is believed to be related to the presence of the Laves eutectic in the latter two alloys with corresponding larger solidification ranges. Hot cracking of 718Plus is slightly less than in 718.
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| 43. |
- Andersson, Joel, 1981-, et al.
(författare)
-
Hot Ductility Study of Haynes 282 Superalloy
- 2010
-
Ingår i: Superalloy 718 and Derivatives. - Hoboken, NJ, USA : The Minerals, Metals, and Materials Society. - 9780470943168 ; , s. 539-554, s. 539-554
-
Konferensbidrag (refereegranskat)
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| 44. |
- Andersson, Joel, 1981-, et al.
(författare)
-
Improved understanding of Varestraint Testing : Nickel-based superalloys
- 2016
-
Ingår i: Cracking Phenomena in Welds IV. - : Springer Publishing Company. - 9783319284323 - 3319284320
-
Konferensbidrag (refereegranskat)abstract
- Information about the book:This is the fourth volume in the well-established series of compendiums devoted to the subject of weld hot cracking. It contains the papers presented at the 4th International Cracking Workshop held in Berlin in April 2014. In the context of this workshop, the term “cracking” refers to hot cracking in the classical and previous sense, but also to cold cracking, stress-corrosion cracking and elevated temp. solid-state cracking. A variety of different cracking subjects are discussed, including test standards, crack prediction, weldability determination, crack mitigation, stress states, numerical modelling, and cracking mechanisms. Likewise, many different alloys were investigated such as aluminum alloys, copper-aluminum dissimilar metal, austenitic stainless steel, nickel base alloys, duplex stainless steel, creep resistant steel, and high strength steel.
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| 45. |
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| 46. |
- Andersson, Joel, et al.
(författare)
-
Integration of CasADi and JModelica.org
- 2011
-
Konferensbidrag (refereegranskat)abstract
- This paper presents the integration of two open source softwares: CasADi, which is a framework for efficient evaluation of expressions and their derivatives, and the Modelica-based platform JModelica.org. The integration of the tools is based on an XML format for exchange of DAE models. The JModelica.org platform supports export of models in this XML format, wheras CasADi supports import of models expressed in this format. Furthermore, we have carried out comparisons with ACADO, which is a multiple shooting package for solving optimal control problems. CasADi, in turn, has been interfaced with ACADO Toolkit, enabling users to define optimal control problems using Modelica and Optimica specifications, and use solve using direct multiple shooting. In addition, a collocation algorithm targeted at solving large-scale DAE constrained dynamic optimization problems has been implemented. This implementation explores CasADi's Python and IPOPT interfaces, which offer a convenient, yet highly efficient environment for development of optimization algorithms. The algorithms are evaluated using industrially relevant benchmark problems.
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| 47. |
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| 48. |
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| 49. |
- Andersson, Jan Joel, et al.
(författare)
-
The European Security Strategy : Reinvigorate, Revise or Reinvent?
- 2011
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper argues that a strategic discussion on the EU’s external action is overdue, and that the future of the European Security Strategy (ESS) should be the centre of that discussion. The precise nature of an eventual new strategy, the process by which it is undertaken, and its intended effects are open questions, however. We offer background, analysis, and reform options as a contribution to a wider European debate on the future role of the EU as an actor on the global stage.
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| 50. |
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