| 1. |
- Alijagic, Andi, 1992-, et al.
(författare)
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Particle Safety Assessment in Additive Manufacturing : From Exposure Risks to Advanced Toxicology Testing.
- 2022
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Ingår i: Frontiers in Toxicology. - : Frontiers Media S.A.. - 2673-3080. ; 4
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Forskningsöversikt (refereegranskat)abstract
- Additive manufacturing (AM) or industrial three-dimensional (3D) printing drives a new spectrum of design and production possibilities; pushing the boundaries both in the application by production of sophisticated products as well as the development of next-generation materials. AM technologies apply a diversity of feedstocks, including plastic, metallic, and ceramic particle powders with distinct size, shape, and surface chemistry. In addition, powders are often reused, which may change the particles' physicochemical properties and by that alter their toxic potential. The AM production technology commonly relies on a laser or electron beam to selectively melt or sinter particle powders. Large energy input on feedstock powders generates several byproducts, including varying amounts of virgin microparticles, nanoparticles, spatter, and volatile chemicals that are emitted in the working environment; throughout the production and processing phases. The micro and nanoscale size may enable particles to interact with and to cross biological barriers, which could, in turn, give rise to unexpected adverse outcomes, including inflammation, oxidative stress, activation of signaling pathways, genotoxicity, and carcinogenicity. Another important aspect of AM-associated risks is emission/leakage of mono- and oligomers due to polymer breakdown and high temperature transformation of chemicals from polymeric particles, both during production, use, and in vivo, including in target cells. These chemicals are potential inducers of direct toxicity, genotoxicity, and endocrine disruption. Nevertheless, understanding whether AM particle powders and their byproducts may exert adverse effects in humans is largely lacking and urges comprehensive safety assessment across the entire AM lifecycle-spanning from virgin and reused to airborne particles. Therefore, this review will detail: 1) brief overview of the AM feedstock powders, impact of reuse on particle physicochemical properties, main exposure pathways and protective measures in AM industry, 2) role of particle biological identity and key toxicological endpoints in the particle safety assessment, and 3) next-generation toxicology approaches in nanosafety for safety assessment in AM. Altogether, the proposed testing approach will enable a deeper understanding of existing and emerging particle and chemical safety challenges and provide a strategy for the development of cutting-edge methodologies for hazard identification and risk assessment in the AM industry.
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| 2. |
- Gåård, Anders, 1977-, et al.
(författare)
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Nano-scale friction of multi-phase powder metallurgy tool steels
- 2015
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Ingår i: Advanced Materials Research. - : Trans Tech Publications. - 1022-6680 .- 1662-8985. ; 1119, s. 70-74
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Tidskriftsartikel (refereegranskat)abstract
- Friction is a fundamental phenomenon in tribology involving complex mechanisms between thecontacting surfaces. Measurements of friction are often made using devices with substantially largercontact area than dimensions corresponding to microstructural features of the materials. Hence, for multi-phase materials,influence of particular microstructural constituents is not resolved. In the present work, a tribometerwith a contact area in the nano-scale range was used to map friction for different types of tool steelswith different chemical- and phase composition. Owing to the small tip radius, frictionalcharacteristics of primary carbides and the steel matrix were measured and compared. Dependingon chemical composition, a difference was observed where the coefficient of friction wasapproximately twice higher for the steel possessing highest coefficient of friction, including bothcarbides and the steel matrix.
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| 3. |
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| 4. |
- Karlsson, Patrik, 1973-, et al.
(författare)
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Galling resistance and wear mechanisms for cold-work tool steels in lubricated sliding against high strength stainless steel sheets
- 2012
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Ingår i: Wear. - Amsterdam : Elsevier. - 0043-1648 .- 1873-2577. ; 286-287, s. 92-97
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Tidskriftsartikel (refereegranskat)abstract
- Tool damage in sheet metal forming of stainless steel is of high concern for the forming industry. In the present work, ingot cast AISI D2 and advanced powder metallurgy tool steel (PM) cold-work tool steels were evaluated and ranked regarding wear mechanisms and galling resistance. Wear tests were performed using a slider-on-flat-surface (SOFS) tribometer in sliding against austenitic–ferritic (duplex) stainless steel sheets at different contact pressures in lubricated conditions. The best galling resistance was observed for the nitrogen alloyed PM tool steels. Abrasive scratching of the tool surfaces and transfer of sheet material due to adhesive wear were the main metal forming tool surface damage mechanisms. By increasing the hardness of one PM sheet metal forming tool grade, the galling resistance was enhanced.
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| 5. |
- Karlsson, Patrik, 1973-, et al.
(författare)
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Influence of size and distribution of hard phases in tool steels on the early stage of galling
- 2012
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Ingår i: TOOL 2012. - Knittelfeld : Verlag "Gutenberghaus". - 9783901384523
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Konferensbidrag (refereegranskat)abstract
- In sheet metal forming processes, contact pressures are relatively high and total sliding distances are long, which demands tool steels to prevent tool damage and to resist galling. Galling is related to microscopic and macroscopic material transfer, but, the mechanisms of initiation are not thoroughly understood.To investigate galling initiation, lubricated sliding testing in the Slider-On-Flat-Surface (SOFS) tribometer was performed for ingot cast (IC) AISI D2 type and nitrogen alloyed powder metallurgy (PM) tool steel. The sheet grade was EN 1.4509 ferritic stainless steel. To reveal mechanisms in the early stages of galling initiation, transfer and accumulation of sheet material to the tool surfaces were characterized using AFM and SEM.It was found that already after a short sliding distance, transfer of sheet material occurred covering both the matrix and the hard phases. Macroscopic analysis of the contact area showed that initial material transfer and further lump growth occurred at positions corresponding to high plastic strains in the sheet material. Even though initial material transfer was observed for both tested tool steels, the sliding distance to the point where transfer and further lump formation occurred was longer for the PM tool steel. This was discussed in correlation to differences in size and distribution of the hard phases in the tool steels, which was confirmed by AFM and SEM.
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| 6. |
- Karlsson, Patrik, 1973-, et al.
(författare)
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Influence of work material proof stress and tool steel microstructure on galling initiation and critical contact pressure
- 2013
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Ingår i: Tribology International. - Amsterdam : Elsevier. - 0301-679X .- 1879-2464. ; 60, s. 104-110
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Tidskriftsartikel (refereegranskat)abstract
- EN 1.4301 (austenitic), EN 1.4509 (ferritic), EN 1.4162 (duplex) and EN 1.4310 C1000 (metastable austenitic) stainless steels were tested in lubricated sliding against an ingot cast EN X153WCrMoV12 and powder metallurgy nitrogen alloyed Uddeholm Vancron 40 tool steels to reveal critical to galling contact pressure, Pcr. The calculated Pcr were higher for steels with higher strength. At P>Pcr, due to plastic flow of sheet material, the tool is damaged substantially and wear-induced matrix damage causes rapid galling initiation. At P
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| 7. |
- Alijagic, Andi, 1992-, et al.
(författare)
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A Novel Nanosafety Approach Using Cell Painting, Metabolomics, and Lipidomics Captures the Cellular and Molecular Phenotypes Induced by the Unintentionally Formed Metal-Based (Nano)Particles
- 2023
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Ingår i: Cells. - : MDPI. - 2073-4409. ; 12:2
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Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing (AM) or industrial 3D printing uses cutting-edge technologies and materials to produce a variety of complex products. However, the effects of the unintentionally emitted AM (nano)particles (AMPs) on human cells following inhalation, require further investigations. The physicochemical characterization of the AMPs, extracted from the filter of a Laser Powder Bed Fusion (L-PBF) 3D printer of iron-based materials, disclosed their complexity, in terms of size, shape, and chemistry. Cell Painting, a high-content screening (HCS) assay, was used to detect the subtle morphological changes elicited by the AMPs at the single cell resolution. The profiling of the cell morphological phenotypes, disclosed prominent concentration-dependent effects on the cytoskeleton, mitochondria, and the membranous structures of the cell. Furthermore, lipidomics confirmed that the AMPs induced the extensive membrane remodeling in the lung epithelial and macrophage co-culture cell model. To further elucidate the biological mechanisms of action, the targeted metabolomics unveiled several inflammation-related metabolites regulating the cell response to the AMP exposure. Overall, the AMP exposure led to the internalization, oxidative stress, cytoskeleton disruption, mitochondrial activation, membrane remodeling, and metabolic reprogramming of the lung epithelial cells and macrophages. We propose the approach of integrating Cell Painting with metabolomics and lipidomics, as an advanced nanosafety methodology, increasing the ability to capture the cellular and molecular phenotypes and the relevant biological mechanisms to the (nano)particle exposure.
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| 8. |
- Alijagic, Andi, 1992-, et al.
(författare)
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Immunotoxic, genotoxic, and endocrine disrupting impacts of polyamide microplastic particles and chemicals
- 2024
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Ingår i: Environment International. - : Elsevier. - 0160-4120 .- 1873-6750. ; 183
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Tidskriftsartikel (refereegranskat)abstract
- Due to their exceptional properties and cost effectiveness, polyamides or nylons have emerged as widely used materials, revolutionizing diverse industries, including industrial 3D printing or additive manufacturing (AM). Powder-based AM technologies employ tonnes of polyamide microplastics to produce complex components every year. However, the lack of comprehensive toxicity assessment of particulate polyamides and polyamide-associated chemicals, especially in the light of the global microplastics crisis, calls for urgent action. This study investigated the physicochemical properties of polyamide-12 microplastics used in AM, and assessed a number of toxicity endpoints focusing on inflammation, immunometabolism, genotoxicity, aryl hydrocarbon receptor (AhR) activation, endocrine disruption, and cell morphology. Specifically, microplastics examination by means of field emission scanning electron microscopy revealed that work flow reuse of material created a fraction of smaller particles with an average size of 1-5 µm, a size range readily available for uptake by human cells. Moreover, chemical analysis by means of gas chromatography high-resolution mass spectrometry detected several polyamide-associated chemicals including starting material, plasticizer, thermal stabilizer/antioxidant, and migrating slip additive. Even if polyamide particles and chemicals did not induce an acute inflammatory response, repeated and prolonged exposure of human primary macrophages disclosed a steady increase in the levels of proinflammatory chemokine Interleukin-8 (IL-8/CXCL-8). Moreover, targeted metabolomics disclosed that polyamide particles modulated the kynurenine pathway and some of its key metabolites. The p53-responsive luciferase reporter gene assay showed that particles per se were able to activate p53, being indicative of a genotoxic stress. Polyamide-associated chemicals triggered moderate activation of AhR and elicited anti-androgenic activity. Finally, a high-throughput and non-targeted morphological profiling by Cell Painting assay outlined major sites of bioactivity of polyamide-associated chemicals and indicated putative mechanisms of toxicity in the cells. These findings reveal that the increasing use of polyamide microplastics may pose a potential health risk for the exposed individuals, and it merits more attention.
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| 9. |
- Gonzales-Siles, Lucia, et al.
(författare)
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A Pangenome Approach for Discerning Species-Unique Gene Markers for Identifications of Streptococcus pneumoniae and Streptococcus pseudopneumoniae
- 2020
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Ingår i: Frontiers in Cellular and Infection Microbiology. - : Frontiers Media SA. - 2235-2988. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Correct identifications of isolates and strains of the Mitis-Group of the genus Streptococcus are particularly difficult, due to high genetic similarity, resulting from horizontal gene transfer and homologous recombination, and unreliable phenotypic and genotypic biomarkers for differentiating the species. Streptococcus pneumoniae and Streptococcus pseudopneumoniae are the most closely related species of the clade. In this study, publicly-available genome sequences for Streptococcus pneumoniae and S. pseudopneumoniae were analyzed, using a pangenomic approach, to find candidates for species-unique gene markers; ten species-unique genes for S. pneumoniae and nine for S. pseudopneumoniae were identified. These species-unique gene marker candidates were verified by PCR assays for identifying S. pneumoniae and S. pseudopneumoniae strains isolated from clinical samples. All determined species-level unique gene markers for S. pneumoniae were detected in all S. pneumoniae clinical isolates, whereas fewer of the unique S. pseudopneumoniae gene markers were present in more than 95% of the clinical isolates. In parallel, taxonomic identifications of the clinical isolates were confirmed, using conventional optochin sensitivity testing, targeted PCR-detection for the "Xisco" gene, as well as genomic ANIb similarity analyses for the genome sequences of selected strains. Using mass spectrometry-proteomics, species-specific peptide matches were observed for four of the S. pneumoniae gene markers and for three of the S. pseudopneumoniae gene markers. Application of multiple species-level unique biomarkers of S. pneumoniae and S. pseudopneumoniae, is proposed as a protocol for the routine clinical laboratory for improved, reliable differentiation, and identification of these pathogenic and commensal species.
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| 10. |
- Karlsson Häikiö, Tarja, et al.
(författare)
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Experiences from creating opportunities for producing senior lecturers in Sloyd and Visual Art Education
- 2024
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Ingår i: NERA 2024. - Malmö.
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Konferensbidrag (refereegranskat)abstract
- The Swedish Research Council (Vetenskapsrådet, VR), has funded the National Graduate School in Visual Arts and Sloyd Education, FoBoS) (Sw. Nationella forskarskolan i bildpedagogik och slöjdpedagogik). This graduate school is a collaboration between Gothenburg University, Stockholm University and Konstfack University of Arts, Crafts and Design. The work with the Graduate school began in 2019 and the first PhD students for Degree of Licentiate started in January 2020. FoBoS have contributed to practice-based research and quality in higher education in the subjects Visual Art and Sloyd Education and in this way contributed to establishing the subjects on postgraduate level by producing new researchers.There is an urgent need to do more research in Sloyd and Visual Arts Education in Sweden. The current situation in these minor school subjects is limited. Lack of research programs as well as doctoral positions means that these studies seldom can build an autonomous research environment with advisors which can support the subject’s specific inquiries, theories and methods. There is also a lack of educators in Swedish universities in subject didactics in general (The Research Council, 2023).FoBoS has been part of the strategic investment in graduate schools that has been important for “the supply of skills and to further strengthen the field of educational science as well as the scientific basis of teacher education and the school” (The Research Council, 2023 p. 6). Secure resources for career paths for new researchers and building excellent research environments as a result of the national research schools, subject didactic research, research on learning processes, on professions and professional training. Collaborative doctoral students are important as there is still a "weak connection between research on teaching and the teachers' everyday school life, as well as insufficient conditions to use knowledge from research and proven experience in the activities" (The Research Council, 2023 p. 14).In this Roundtable discussion we in the steering group of FoBoS share our experiences of our work with the graduate school, in particular challenges in supporting the development of research in this area. Some of these challenges relate to structural conditions and how support for research and graduate schools is organized. Other challenges are how to create possibilities for continued trajectories from licentiate studies to doctoral studies, as well as onwards towards post-doctoral positions. What does the future look like for postgraduate education in the subjects and in higher education? What are the conditions for producing more researchers, career opportunities and postdocs? Despite an increased number of PhD:s in educational science, there is a great shortage of researchers for teacher training, even in the aesthetic subjects "to meet the societal challenges that characterize schools and higher education today" (The Research Council, 2023 p. 6). We in the steering group for FoBoS are interested in discussing how to create new opportunities for more research and researchers in Sloyd and Visual Arts. We invite you in our Roundtable discussion.ReferencesThe Research Council [Vetenskapsrådet] (2023). Forskningsöversikt 2023. Utbildningsvetenskap. Stockholm.
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| 11. |
- Karlsson, Patrik, 1973-, et al.
(författare)
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Factors Influencing Mechanical Properties of Additive Manufactured Thin-Walled Parts
- 2017
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Ingår i: Euro PM2017 Congress Proceedings. - : European Powder Metallurgy Association (EPMA).
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Konferensbidrag (refereegranskat)abstract
- By using the Additive Manufacturing (AM) method it is possible to manufacture components with thin-walled sections and complex geometry. However, it is not clear when the surface becomes the strength limiting factor on thin-walled sections in the components or if the thickness of the components is reduced. Also, the microstructure of AM produced specimens may be heterogeneous and it is not clear how the build direction influence the strength of thin section components. In the present study, the influence of component thickness, surface roughness and build direction on the strength of AM produced components were investigated. Test specimens were manufactured using EOS M290 3D-printer and EN 1.2709 maraging steel powder. To investigate when the part thickness, surface and built orientation becomes the strength limiting factors tensile testing using thin samples built in both horizontal and vertical build orientation with thicknesses ranging from 0.2 mm to 4 mm was performed. Results on strength limiting factors are discussed.
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| 12. |
- Karlsson, Patrik, 1973-, et al.
(författare)
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Galling resistance evaluation of tool steels by two different laboratory test methods for sheet metal forming
- 2012
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Ingår i: Lubrication Science. - : John Wiley & Sons. - 0954-0075 .- 1557-6833. ; 24:6, s. 263-272
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Tidskriftsartikel (refereegranskat)abstract
- Adhesive accumulation of work material on the tool surface is today a major problem in many sheet metal-forming applications. Different laboratory test methods are used to investigate galling with respect to different tool materials, lubricants and process conditions. In the present study, the galling resistance of a modern nitrogen-alloyed powder metallurgy tool steel and an conventional ingot cast D2 type tool steel was evaluated under lubricated sliding against ferritic stainless steel sheets using a commercial pin-on-disc (POD) and an in-house made slider-on-flat-surface (SOFS) tribotester. The investigated tool steels ranked similarly in terms of galling resistanc in both test methods. However, sliding distances to galling were longer for the SOFS equipment due to continuous sliding on new lubricated sheet surface. Best performance was demonstrated by the powder metallurgy tool steel treated to 65 HRC. Differences in friction behaviour and galling initiation were analysed on the basis of the two different working conditions, i.e. open (SOFS) and closed (POD) tribosystems. Copyright © 2012 John Wiley & Sons, Ltd.
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| 13. |
- Karlsson, Patrik, 1973-, et al.
(författare)
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Generative Design Optimization and Characterization of Triple Periodic Lattice Structures in AlSi10Mg
- 2020
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Ingår i: Industrializing Additive Manufacturing. - Cham : Springer. - 9783030543334 - 9783030543341 ; , s. 3-16
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Konferensbidrag (refereegranskat)abstract
- In this work, generative design optimization and characterization of triple periodic lattice structures in AlSi10Mg are considered. Structures with Gyroid, Schwarz-D and G-prime lattices are designed optimally by utilizing a generative design optimization approach. The approach is based on topology optimization, support vector machines (SVM), radial basis function networks (RBFN), morphing operations, design of experiments and metamodels. Firstly, topology optimization solutions are generated which are represented using SVM, secondly, sizing solutions obtained by setting the SIMP parameter equal to one are represented with RBFN. Thirdly, graded lattice structures using the RBFN are morphed together with the SVM to final conceptual designs. Fourthly, design of experiments of the conceptual designs are performed using non-linear finite element analyses (FEA) and, finally, metamodel-based design optimization is conducted using convex combinations of Kriging, RBFN, polynomial chaos expansion and support vector regression models. In order to validate the optimal designs, new tensile test specimens that include the periodic lattice structures are suggested. The specimens with all three lattices are manufactured in AlSi10Mg using direct metal laser sintering with an EOS M290 machine. Tensile tests of these specimens are then performed and validated using nonlinear FEA. The test specimens are also characterized with respect to geometry and defects by means of computed tomography, optical microscopy and scanning electron microscopy. The study demonstrates the high potential of using the proposed generative design optimization approach with triple periodic lattice structures for producing robust lightweight designs using additive manufacturing. In order to demonstrate the industrial relevance the established GE engine bracket is studied in the paper and discussed at the conference.
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| 14. |
- Karlsson, Patrik, 1973-, et al.
(författare)
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Influence of tool steel hard phase orientation and shape on galling
- 2014
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Ingår i: Advanced Materials Research. - : Trans Tech Publications. - 1022-6680 .- 1662-8985. ; 966-96, s. 249-258
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Tidskriftsartikel (refereegranskat)abstract
- Conventionally manufactured cold work tool steel is often used in sheet metal forming as die material. Due to the forging process, the as-cast network structure of carbides is broken into elongated particles. Depending on the tool cross-section, the orientation and shape of carbides in the active tool surface is different. In the present research, the influence of tool steel hard phase orientation and shape on galling was investigated. D2 type tool steel was cut in three different orientations and tested in lubricated sliding conditions against AISI 304 austenitic stainless steel. Tests were performed using a Slider-On-Flat-Surface and galling was detected by changes in friction and post-test microscopy. The lubricant was Castrol FST8 using 5 g/m2 sheet material. Results showed a strong correlation between sliding distance to galling and tool steel hard phase orientation and shape at low loads, whereas high load contact resulted in early galling in all cases. Material transfer was observed mainly to the tool steel matrix. The worst performance was observed for specimens cut so that the tool steel hard phase, M7C3 carbides in the D2 steel, were oriented along the sliding direction, which resulted in longer open tool matrix areas contacting the sheet material.
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| 15. |
- Karlsson, Patrik, 1973-, et al.
(författare)
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Influence of tool steel microstructure on friction and initial material transfer
- 2014
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Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 319:1-2, s. 12-18
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Tidskriftsartikel (refereegranskat)abstract
- An investigation was conducted to study the influence of tool steel microstructure on initial material transfer and friction. Two different powder metallurgy tool steels and an ingot cast tool material were tested in dry sliding against 1.4301, 1.4162, Domex 355 MC and Domex 700 MC sheet materials. It was found that tool steel hard phase heights influence initial material transfer and friction. The coefficient of friction increased with decreasing tool steel hard phase heights at 50 N normal load and initial material transfer occurred around protruding hard phases. At higher load of 500 N the sheet material adhered to both the tool steel matrix and hard phases. Coefficient of friction decreased with increasing proof strength of the sheet material at 500 N normal load.
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| 16. |
- Karlsson, Patrik Milton, et al.
(författare)
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The Arabidopsis thylakoid transporter PHT4;1 influences phosphate availability for ATP synthesis and plant growth
- 2015
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Ingår i: The Plant Journal. - : Wiley. - 0960-7412 .- 1365-313X. ; 84:1, s. 99-110
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Tidskriftsartikel (refereegranskat)abstract
- The Arabidopsis phosphate transporter PHT4;1 was previously localized to the chloroplast thylakoid membrane. Here we investigated the physiological consequences of the absence of PHT4;1 for photosynthesis and plant growth. In standard growth conditions, two independent Arabidopsis knockout mutant lines displayed significantly reduced leaf size and biomass but normal phosphorus content. When mutants were grown in high-phosphate conditions, the leaf phosphorus levels increased and the growth phenotype was suppressed. Photosynthetic measurements indicated that in the absence of PHT4;1 stromal phosphate was reduced to levels that limited ATP synthase activity. This resulted in reduced CO2 fixation and accumulation of soluble sugars, limiting plant growth. The mutants also displayed faster induction of non-photochemical quenching than the wild type, in line with the increased contribution of ΔpH to the proton-motive force across thylakoids. Small-angle neutron scattering showed a smaller lamellar repeat distance, whereas circular dichroism spectroscopy indicated a perturbed long-range order of photosystem II (PSII) complexes in the mutant thylakoids. The absence of PHT4;1 did not alter the PSII repair cycle, as indicated by wild-type levels of phosphorylation of PSII proteins, inactivation and D1 protein degradation. Interestingly, the expression of genes for several thylakoid proteins was downregulated in the mutants, but the relative levels of the corresponding proteins were either not affected or could not be discerned. Based on these data, we propose that PHT4;1 plays an important role in chloroplast phosphate compartmentation and ATP synthesis, which affect plant growth. It also maintains the ionic environment of thylakoids, which affects the macro-organization of complexes and induction of photoprotective mechanisms.
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| 17. |
- Karlsson, Patrik, 1973-
(författare)
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The early stage of galling
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In sheet metal forming (SMF) of materials such as stainless steels there is a major problem with transfer and accumulation of sheet material to the metal forming tool surface. The problem is known as galling; a kind of severe adhesive wear, which results in severe scratching of produced parts. In this thesis, galling observed in contacts between tool steels and stainless steel sheets under lubricated sliding conditions was studied, focusing on the early stage of galling. It was found that changes in friction cannot be used as galling indicator in the early stage of galling because transfer and accumulation of sheet material happens even though friction is low and stable. The progression of galling is influenced by tool steel damage occurring around the tool steel hard phases caused by sheet material flow, which results in formation of wear-induced galling initiation sites. A correlation between the critical contact pressure to galling and sheet material proof stress was found. Galling happened at lower pressures for sheet material with lower proof stress possibly due to easier sheet material flow, resulting in quicker tool damage. Material transfer and tool steel damage were delayed for tool steels comprising homogenously distributed, small and high hard phases. Additionally, the galling resistance was higher for tool steels with higher hardness due to decreased tool steel damage. In a comparison between observations of the worn tool surfaces after wear tests and calculations in FEM it was found that material transfer did not take place at regions with highest contact pressures but at regions with highest plastic strains. The results obtained in this thesis indicate that tool steel damage and sheet material flow occurring in the contact during sliding are important factors influencing galling.
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| 18. |
- Karlsson, Patrik, 1973-
(författare)
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The influence of tool steel microstructure on galling
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In sheet metal forming (SMF) of materials such as stainless steels there is a major problem with transfer and accumulation of sheet material to the metal forming tool surface. The problem is known as galling; a sort of severe adhesive wear, which results in severe scratching of produced parts. In this thesis, the overall aim was to gain knowledge of the influence of tool steel microstructure on galling initiation under sliding conditions. It was discovered that material transfer and tool steel damage caused by sheet material flow creating wear-induced galling initiation sites occurred in the early stage of galling. The galling resistance was higher for tool steels with higher matrix hardness due to better resistance to tool steel damage. Initial friction and critical contact pressure to galling was influenced by the strength of the sheet material. Material transfer happened at low pressures and the friction value was high in a case of sheet materials with lower proof strength, possibly due to the sheet contact against the tool steel matrix resulting in high adhesion and quicker tool damage. It was demonstrated that, in addition to hardness of the tool steel matrix and sheet material proof strength, tool steel microstructural features like size, shape, distribution and height of hard phases are important parameters influencing galling. Tool steels comprising homogeneously distributed, small and high hard phases better prevented the contact between sheet material and the tool steel matrix. Thus, a metal to metal contact with high friction was more efficiently avoided, which resulted in better tool performance.
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| 19. |
- Karlsson, Staffan, 1959-, et al.
(författare)
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Antipsychotic medication in relation to national directives in people with dementia in Sweden
- 2017
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Ingår i: Program Abstracts from the 21st International Association of Gerontology and Geriatrics (IAGG) World Congress. - Washington, DC : The Gerontological Society of America. ; , s. 348-349
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Konferensbidrag (refereegranskat)abstract
- The aim of this study was to explore trends in treatment with antipsychotic medication in Swedish dementia care as reported in the most recent empirical studies on the topic, and to relate these trends to directives and recommendations from national authorities.The study included two scoping review studies and two empirical studies. The scoping studies reviewed published data in electronic databases as well as Swedish recommendations and directives in the field.During the past decade, recommendations have been developed regarding antipsychotic medication in Sweden. These recommendations were generic at first, but have become increasingly specific and restrictive with time. The scoping review showed that treatment with antipsychotic drugs varied between 6% and 38%, and was higher in younger older persons and those with moderate cognitive impairment and living in nursing homes for people with dementia. A trend towards a decrease in antipsychotic use has been seen over the last 15 years. The empirical studies showed that the medication with antipsychotics decreased from 23.4% in 2001 to 11.5% in 2007, for older people in general as well as for older people with dementia. Among older people with dementia, 10% were utilizing antipsychotic medication, with no difference between those cared for at home and those in nursing homes.Directives from Swedish national authorities seem to have had an impact on antipsychotic medication for people with dementia. Treatment with antipsychotic medication has decreased, while other psychotropic medication has increased. National directives may possibly be even more effective, if applied in combination with systematic follow-ups.
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| 20. |
- Karlsson, Staffan, 1959-, et al.
(författare)
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The trends in treatment with antipsychotic medication in relation to national directives in people with dementia : Review in a Swedish context
- 2017
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Ingår i: Capacity, Creativity and Ageing in Clinical Practice. ; , s. 36-36
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Konferensbidrag (refereegranskat)abstract
- Background: Antipsychotic medication has been commonly used in dementia treatment despite various side effects, which differ for different drug generations. As there is no clear evidence for treatment with antipsychotic medication among older people with dementia, may a review of empirical studies and national directives be beneficial.Objectives: The aim of this study was to explore trends in treatment with antipsychotic medication in Swedish dementia care in nursing homes as reported in the most recent empirical studies on the topic, and to relate these trends to directives from the national authorities.Methods: The study included two scoping review studies based on searches of electronic databases as well as the Swedish directives in the field.Findings: During the past decade, directives have been developed for antipsychotic medication in Sweden. These directives were generic at first, but have become increasingly specific and restrictive with time. The scoping review showed that treatment with antipsychotic drugs varied between 6% and 38%, and was higher in younger older persons and in those with moderate cognitive impairment and living in nursing homes for people with dementia. A decreasing trend in antipsychotic use has been seen over the last 15 years.Conclusions: Directives from the authorities in Sweden may have had an impact on treatment with antipsychotic medication for people with dementia. Treatment with antipsychotic medication has decreased, while treatment with combinations of psychotropic medications is common. National directives may possibly be even more effective, if applied in combination with systematic follow-ups.
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| 21. |
- Karlsson, Staffan, 1959-, et al.
(författare)
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Treatment with antipsychotic medication in relation to national directives in people with dementia in a Swedish context
- 2016
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Ingår i: Presented at the 26th Alzheimer Europe Conference: Excellence in dementia research and care, Copenhagen, Denmark, October 31-November 2, 2016. ; , s. 52-52
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Konferensbidrag (refereegranskat)abstract
- Background: The aim of this study was to explore trends in treatment with antipsychotic medication in Swedish dementia care in the most recent empirical studies on the treatment with antipsychotic treatment and relate it to directives and recommendations from national authorities.Methods: The study included; two scoping review studies and two empirical studies. The scoping studies were review of published data in electronic databases as well as Swedish recommendations and directives in the area.Results: The last decade, recommendations were developed regarding antipsychotic medication in Sweden, in the beginning overviewing to be more and more specific and restrictive. The scoping review showed that the treatment with antipsychotic drugs varied between 6%-38%, and was higher in younger older persons and those with moderate cognitive impairment and living in nursing homes for people with dementia. A trend of a decreased treatment with antipsychotics was seen over the last 15 years. The empirical studies showed that the medication with antipsychotics decreased from 23.5 % in 2001 to 12 % in 2007, for older people in general as well as for older people with dementia. In older people with dementia only, 10% were utilizing antipsychotic medication, with no difference between those in ordinary homes compared to those in nursing homes.Conclusions: Directives from Swedish national authorities seems to have had an impact on antipsychotic medication in people with dementia. The treatment with antipsychotic medication decreased, while other psychotropic medication increased. National directives complemented with systematic follow-ups may possibly be even more effective.Conclusion: Treatment with orexin suppressed phagocytosis and degradation of Aβ. Further investigation suggested that the effects of orexin may be mainly on, or mediated through actin. Further investigations concerning the effects of orexin antagonists may be able to offer new methods to arrest the progress of, or possibly treat, AD.
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| 22. |
- Larsson, Joakim, 1989-, et al.
(författare)
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Enhanced cooling by conformal cooling of additively manufactured wire drawing tools made of cemented carbides
- 2022
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Ingår i: Metal Additive Manufacturing Conference. ; , s. 225-235
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Konferensbidrag (refereegranskat)abstract
- Components made from wire can be found in almost all complex products. In the wire drawing process, hot rolled wire is drawn through a single or a series of tools, which reduces the cross section of the wire and enhances the mechanical properties of the material. The tribological conditions in the process are extreme and the high frictional forces between the wire and the die results in high tool temperatures. Previous studies have shown that by reducing the temperature of the drawing tool it is possible to decrease the tool wear rate. Hence, cooling of the tool is of high importance in the wire drawing process.In this study, the possibilities to decrease the tool temperature by introducing conformal cooling in the drawing tool was investigated. Drawing tools made of cemented carbide like material were designed to utilize conformal cooling and manufactured by additive manufacturing. Results on cooling efficiency in an industrial-like wire drawing process are presented and discussed.
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| 23. |
- Larsson, Joakim, 1989-, et al.
(författare)
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Enhanced Cooling Design in Wire Drawing Tooling Using Additive Manufacturing
- 2021
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Ingår i: Industrializing Additive Manufacturing. - Cham : Springer, Cham. - 9783030543341 - 9783030543334 ; , s. 426-436
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Konferensbidrag (refereegranskat)abstract
- Wire drawing is a manufacturing process in which metal rods or wires are drawn through a single or a series of dies, reducing the wire cross-section and enhancing the mechanical properties of the wire. The tribological conditions in wire drawing are quite extreme and high friction between the wire and the die results in an increased die temperature. Previous studies have shown that by reducing the die temperature the lifetime of the die increases and thus efficient cooling of the die is of high importance.Additive manufacturing enables fabrication of tools with advanced conformal cooling channels with high cooling efficiency. This technique may, therefore, be of high importance in the design of the cooling system of drawing dies. In the present study, the effect of conformal cooling design of die holder on the die temperature, and thus die performance, was investigated. A die holder was manufactured by means of laser powder bed fusion (LPBF) in an EOS M290 machine using atomized corrosion resistant steel (Corrax). The cooling efficiency of the manufactured tool holder was evaluated in an industrial wire drawing process and further analysed using FEM modelling. This study shows promising results on improved cooling efficiency for die holder designed and manufactured by additive manufacturing.
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| 24. |
- Larsson, Joakim, 1989-
(författare)
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Have you heard about wire? Monitoring of the wire drawing process
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wire made from metal is a fundamental component found in almost every complex product, ranging from a simple pen to a spacecraft. It is used to manufacture nails, screws, springs, rivets, cables, welding electrodes, and numerous other items that surround us daily.In an era characterized by increased environmental concerns and the pressing need for the industry to become more sustainable, process monitoring has emerged as a key instrument for strengthening the sustainability improvements of diverse industries and operations. Many industries have transitioned into the realm of Industry 4.0, entering an era of digital transformation and datadriven decision-making. However, the production of steel wire has fallen behind. The wire drawing process has been performed in a similar manner for the last century and the production machines generally lack advanced monitoring systems. To catch up, there is a great need to digitize the wire drawing process and that is the focus of this thesis, Monitoring of the wire drawing process.In this thesis several different methods to monitor the wire drawing process are developed and evaluated, resulting in a process monitoring system for the wire drawing process.
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| 25. |
- Larsson, Joakim, 1989-, et al.
(författare)
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In-situ evaluation of the performance of wire drawing using multiple sensors
- 2023
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Ingår i: Interwire 2023. ; , s. 3-14
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Konferensbidrag (refereegranskat)abstract
- In-situ evaluation (monitoring) of the wire drawing process is often performed manually in today’s industry which is a difficult task for the operator, requiring both time and experience. Previous research at Örebro university has been performed to identify and evaluate automated in-situ monitoring methods for the wire drawing process. From this research, several methods that can be applied for monitoring purposes have been identified. However, the advantage of using multiple sensors has not yet been investigated. How data from different monitoring sensor signals correlates with each other and if they can be combined to obtain a better understanding of the wire drawing process will be investigated and discussed in this work. Four different sensor signals; vibration, wire temperature, brightness of the wire surface and drawing force, will be compared and evaluated in wire drawing experiments where the process conditions are controlled. The results show that all the evaluated sensors indicate similar to deviations in the lubrication process, however, some problems could only be detected by some sensors. Using multiple sensors can have advantages in both detection and misrepresentation of problems and might be used to classify specific types of problems in the process.
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| 26. |
- Larsson, Joakim, 1989-, et al.
(författare)
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Monitoring and evaluation of the wire drawing process using thermal imaging
- 2019
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Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer. - 0268-3768 .- 1433-3015. ; 101:5-8, s. 2121-2134
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Tidskriftsartikel (refereegranskat)abstract
- Wire drawing is a cold work metal forming process which is dependant of a functional lubrication process. If the lubrication fails, there is a risk that both the tools and the produced wire will be damaged. Process monitoring of wire drawing is rare in today’s industry since there are no commercialised methods that deliver consistent results. In this paper, a method for monitoring of the wire drawing process is proposed and evaluated. A thermal imaging camera was used for acquiring thermal images of the wire as it leaves the drawing tool. It was found that the proposed method could capture changes in the wire drawing process and had correlation to the drawing force. An equation for estimating the friction condition between the wire and the drawing die using the wire temperature was also proposed and evaluated against experiments. The results showed that the new equation produced results that correlated well to results obtained using a conventional equation that use drawing force.
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| 27. |
- Larsson, Joakim, 1989-, et al.
(författare)
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The effect of bearing length on the surface quality of drawn wire
- 2019
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Konferensbidrag (refereegranskat)abstract
- In wire drawing, the geometry of drawing dies influences the performance of the wire process. This study investigates the effect of bearing lengths on the surface quality of the drawn wire. Wire drawing tests were done using an industrial wiredrawing machine utilizing drawing dies with different bearing lengths. The influence of bearing length on surface quality is discussed.
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| 28. |
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| 29. |
- Larsson, Joakim, 1989-, et al.
(författare)
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The Influence of Nozzle Size on the Printing Process and the Mechanical Properties of FFF-Printed Parts
- 2023
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Ingår i: Industrializing Additive Manufacturing. - : Springer. - 9783031429828 - 9783031429835 ; , s. 159-170
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Konferensbidrag (refereegranskat)abstract
- Recent process developments in Fused Filament Fabrication (FFF), such as the possibilities to use high end polymers (for example PEEK) or to manufacture metal parts and parts reinforced with continuous fibers, have increased industrial interest. Previously, this additive manufacturing (AM) technology was mostly popular among hobbyists thanks to its low investment cost. With the increased industrial interest comes higher demands on product strength and production efficiency.The FFF process has many parameters that should be optimized to meet these tougher requirements. One of these parameters is the size of the nozzle through which the filament is extruded. Today a fairly wide range of sizes are available on the market, but most standard-sized printers come equipped with a 0.4 mm nozzle.In this study, a wide range of nozzles of different sizes have been manufactured to investigate how the nozzle size affects both the printing process and the mechanical properties of the printed parts. Tensile bars have been manufactured in polylactic acid (PLA) using 7 different nozzle sizes. The samples were investigatedby means of computer tomography (CT) and optical microscopy and subjected totensile testing.
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| 30. |
- Lilja Skånberg, Patrik, 1973-, et al.
(författare)
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Actionkameror som redskap för att synliggöra elevers lärande i undervisningsutveckling
- 2021
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Ingår i: Framtidens Digitala Lärande i Skolan (FDLIS). - Halmstad : Högskolan i Halmstad. - 9789151982410 - 9789151982403 ; , s. 155-169
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- I kapitlet har forskaren Patrik Lilja Skånberg tillsammans med Magnus Lindblad, Christian Lorentzen, Kristofer Karlsson och Karin Wilsson från Varbergs kommun undersökt hur digital video erbjuder möjligheter till systematiskt undersökande, kontinuerlig formativ ämnesdidaktisk undervisningsutveckling där elevernas lärande är i centrum.
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| 31. |
- Lin, Zeyu, et al.
(författare)
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A Systematic Approach to Optimize Parameters in Manufacturing Complex Lattice Structures of NiTi Using Electron Beam Powder Bed Fusion Process
- 2024
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Ingår i: Advanced Engineering Materials. - : Wiley-VCH Verlagsgesellschaft. - 1438-1656 .- 1527-2648. ; 26:10
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Tidskriftsartikel (refereegranskat)abstract
- Herein, the quality and accuracy to manufacture delicate parts from NiTi powder using electron beam powder bed fusion (EB-PBF) technology is investigated. Therefore, benchmarks with thin cylinders and thin walls are designed and fabricated using two distinct scan strategies of EB-PBF manufacturing (i.e., continuous melting and spot melting) with different process parameter sets. After these optimizations, four different lattice structures (i.e., octahedron, cell gyroid, sheet gyroid, and channel) are manufactured and characterized. It is shown both continuous melting and spot melting modes are able to manufacture lattices with relative densities over 97%. And as-built lattice structures exhibit an excellent pseudoelasticity up to 8% depending on the design of the structure, e.g., the channel structure shows more deformation recoverability than the cell gyroid. This is attributed to the integrity of geometry as well as compressive mode of the mechanical loading. Of course, the compressive strength and ultimate compressive strength also increase with the increasing volume fraction. Moreover, the spot melting can be used as an engineering tool to customize a delicate beam-shaped structure with a superior pseudoelasticity.This study explores the precision of electron beam powder bed fusion (EB-PBF) for NiTi parts using continuous and spot melting scan strategies for the density and mechanical properties.image (c) 2024 WILEY-VCH GmbH
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| 32. |
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| 33. |
- Sundström, Johan, Professor, 1971-, et al.
(författare)
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Rationale for a Swedish cohort consortium
- 2019
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Ingår i: Upsala Journal of Medical Sciences. - : Taylor & Francis Group. - 0300-9734 .- 2000-1967. ; 124:1, s. 21-28
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Tidskriftsartikel (refereegranskat)abstract
- We herein outline the rationale for a Swedish cohort consortium, aiming to facilitate greater use of Swedish cohorts for world-class research. Coordination of all Swedish prospective population-based cohorts in a common infrastructure would enable more precise research findings and facilitate research on rare exposures and outcomes, leading to better utilization of study participants' data, better return of funders' investments, and higher benefit to patients and populations. We motivate the proposed infrastructure partly by lessons learned from a pilot study encompassing data from 21 cohorts. We envisage a standing Swedish cohort consortium that would drive development of epidemiological research methods and strengthen the Swedish as well as international epidemiological competence, community, and competitiveness.
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| 34. |
- Surreddi, Kumar Babu, 1977-, et al.
(författare)
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In-situ micro-tensile testing of additive manufactured maraging steels in the SEM : Influence of build orientation, thickness and roughness on the resulting mechanical properties
- 2018
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Ingår i: La Metallurgia Italiana. - : ASSOC ITALIANA METALLURGIA. - 0026-0843. ; :3, s. 27-33
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Tidskriftsartikel (refereegranskat)abstract
- Selective laser melting (SLM) is frequently used additive manufacturing technique capable of producing various complex parts including thin-wall sections. However the surface roughness is a limiting factor in thin sections produced by SLM process when strength is the main criterion. In this study, the influence of build orientation, thickness and roughness on the resulting mechanical properties of as-built test samples was investigated. Various thin sheets of EN 1.2709 maraging steel built in horizontal and vertical orientations produced by SLM were investigated using in-situ micro-tensile testing in a scanning electron microscope. The mechanical strength and deformation mechanisms were analyzed and explained based on thickness and build orientation. Increased ductility was observed in thicker samples as well as in the horizontal build samples. The results illustrate the potential of the in-situ test technique and aspects important to consider in design guidelines for thin AM structures.
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| 35. |
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| 36. |
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