| 1. |
- Lyphout, Christophe, 1981-, et al.
(författare)
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Screening Design of Supersonic Air Fuel Processing for Hard Metal Coatings
- 2014
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Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 23:8, s. 1323-1332
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Tidskriftsartikel (refereegranskat)abstract
- Replacement of electrolytic hard chromium method by thermal spray technology has shown a growing interest in the past decades, mainly pioneered by depositing WC-based material by conventional HVOF processes. Lower thermal energy and higher kinetic energy of sprayed particles achieved by newly developed Supersonic Air Fuel system, so-called HVAF-M3, significantly reduces decarburization, and increases wear and corrosion resistance properties, making HVAF-sprayed coatings attractive both economically and environmentally. In the present work, full factorial designs of experiments have been extensively utilized to establish relationships between hardware configurations, process and engineering variables, and coatings properties. The relevance of those process factors is emphasized and their significance is discussed in the optimization of coatings for improved abrasion wear and corrosion performances. © 2014 ASM International.
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| 2. |
- Dahlmo, K I, et al.
(författare)
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On a new method to assess the accuracy of a CAD program.
- 2001
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Ingår i: International Journal of Prosthodontics. - : Quintessence Publishing. - 0893-2174 .- 1139-9791. ; 14:3, s. 276-83
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: This study was initiated with the purpose of developing and evaluating a system for measuring the magnitude of the variation between a computer-aided design (CAD) object created on the computer screen and a replicated object produced by computer-aided manufacturing (CAM). MATERIALS AND METHODS: Controlled geometric forms, a square and a cone, were designed in a CAD program, and measuring distances were selected. The CAD data were transmitted to CAM data, and objects were produced. The CAD/CAM process was the Procera system, and the holder system permitted the objects to be ground into cross sections, similar to the visualization in the CAD program. Five objects of each shape were produced and measured by two operators two times. Three operators measured one of the objects 30 times. RESULTS: Observed values were greater than the true value. For all objects, the systematic error was at most 15.5 microns. Interoperator difference was small. The variation because of measurement error was greater for the square object compared to the cone. However, the variation because of object was higher for the cone object than for the square. The total standard deviation was 7.7 microns. Thus, the total random error caused by object variation and measurement error was in approximately 95% of all measurements less than 15 microns. CONCLUSION: There are no differences in the measurement data derived from this method and actual measurement data from an object created by the computer-aided dental design program. The method has high validity and reliability, i.e., high accuracy.
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| 3. |
- He, Fei, et al.
(författare)
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FPR2 Shapes an Immune-Excluded Pancreatic Tumor Microenvironment and Drives T-cell Exhaustion in a Sex-Dependent Manner
- 2023
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Ingår i: Cancer Research. - : American Association for Cancer Research (AACR). - 0008-5472 .- 1538-7445. ; 83:10, s. 1628-1645
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Tidskriftsartikel (refereegranskat)abstract
- Sex-driven immune differences can affect tumor progression and the landscape of the tumor microenvironment. Deeper understanding of these differences in males and females can inform patient selection to improve sex-optimized immunotherapy treatments. In this study, single-cell RNA sequencing and protein analyses uncovered a subpopulation of myeloid cells in pancreatic lesions associated with an immune-excluded tumor phenotype and effector T-cell exhaustion exclusively in females. This myeloid subpopulation was positively correlated with poor survival and genetic signatures of M2-like macrophages and T-cell exhaustion in females. The G-protein coupled receptor formyl peptide receptor 2 (FPR2) mediated these immunosuppressive effects. In vitro, treatment of myeloid cells with a specific FPR2 antagonist prevented exhaustion and enhanced cytotoxicity of effector cells. Proteomic analysis revealed high expression of immunosuppressive secretory proteins PGE2 and galectin-9, enriched integrin pathway, and reduced proinflammatory signals like TNFα and IFNγ in female M2-like macrophages upon FPR2 agonist treatment. In addition, myeloid cells treated with FPR2 agonists induced TIM3 and PD-1 expression only in female T cells. Treatment with anti-TIM3 antibodies reversed T-cell exhaustion and stimulated their ability to infiltrate and kill pancreatic spheroids. In vivo, progression of syngeneic pancreatic tumors was significantly suppressed in FPR2 knockout (KO) female mice compared with wild-type (WT) female mice and to WT and FPR2 KO male mice. In female mice, inoculation of tumors with FPR2 KO macrophages significantly reduced tumor growth compared with WT macrophages. Overall, this study identified an immunosuppressive function of FPR2 in females, highlighting a potential sex-specific precision immunotherapy strategy.
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| 4. |
- Kisch, Annika M., et al.
(författare)
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The Meaning of Being a Living Kidney, Liver or Stem Cell Donor : A Meta-Ethnography
- 2018
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Ingår i: Transplantation. - : Wolters Kluwer. - 0041-1337 .- 1534-6080. ; 102:5, s. 744-756
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Studies on living donors from the donors' perspective show that the donation process involves both positive and negative feelings involving vulnerability. Qualitative studies of living kidney, liver, and allogeneic hematopoietic stem cell donors have not previously been merged in the same analysis. Therefore, our aim was to synthesize current knowledge of these donors' experiences in order to deepen understanding of the meaning of being a living donor for the purpose of saving or extending someone's life.METHODS: The meta-ethnography steps presented by Noblit & Hare in 1988 were used.RESULTS: Forty-one qualitative studies from 1968 to 2016 that fulfilled the inclusion criteria were analyzed. The studies comprised experiences of over 670 donors. The time since donation varied from 2 days to 29 years. A majority of the studies, 25 out of 41, were on living kidney donors. The synthesis revealed that the essential meaning of being a donor is doing what one feels one has to do, involving 6 themes; A sense of responsibility, Loneliness and abandonment, Suffering, Pride and gratitude, A sense of togetherness, and A life changing event.CONCLUSION: The main issue is that one donates irrespective of what one donates. The relationship to the recipient determines the motives for donation. The deeper insight into the donors' experiences provides implications for their psychological care.
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| 5. |
- Lahti, K., et al.
(författare)
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Productivity Aspects in Submerged Arc Welding of Thick High-Strength Steels
- 2015
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Ingår i: Proceedings of IIW International Conference, High-Strength Materials. - Helsingfors. ; , s. 1-6-
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Konferensbidrag (refereegranskat)abstract
- A series of welding tests were made on 35 mm thick F500W high strength steel. This specific steel grade is developed for use in arctic conditions, especially in shipbuilding, and it has excellent impact toughness at temperatures down to -60°C. Submerged arc welding tests were performed using solid and flux-cored welding wire keeping the heat-input at levels typically recommended for thermo mechanically processed highstrengthsteels. Process improvement trials were even made using electrode extension (EE) allowing for higher melt-on rates without any increase in the heat input.However, as the chemical composition of F500W allows for higher heat input without risk for excessive grain growth, tests at higher heat inputs were also made as reference for additional ways to increase productivity. Three fundamental means for improving productivity were analyzed in this study: 1) use of solid or flux-cored wire, 2) effect of groove preparation, and 3) use ofelectrode extension. These all can be introduced without changes in heat input, and hence implementation to existing production systems is easy, economical and quick. Highest increase in productivity is gained by using electrode extension with optimized groove geometry. In the studied thickness of 35 mm, the number of runs was decrease by 60 % from 22 to 9 without increase in the heat input and with approved mechanical properties for this specific steel. Based on the outcome of this study, submerged arc welding can successfully be used for joining of this high strength steel with approved mechanical properties and high productivity.
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| 6. |
- Lahti, K., et al.
(författare)
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Submerged Arc Welding of High Strength Steel for Shipbuilding Applications
- 2015
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Ingår i: Proceedings of JOM 18 International conference on joining materials, Helsingör, Danmark, april 26-29 2015. - : JOM-institute. ; , s. 1-8
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Konferensbidrag (refereegranskat)abstract
- In most cases primary purpose for use of high strength steels is weight reduction with resulting benefits in product lifecycle costs. However, as the operating environments vary, it is important to take consideration to the specific requirements for the product in concern. In this study, high strength steel F40SW (YS 460 MPA, UTS 550 MPa) for use in arctic conditions, e.g., icebreakers, are welded with submerged arc welding (SAW) and resulting welds are analyzed for mechanical and metallurgical properties. Submerged arc welding (SAW) is preferred joining process for thick steel plates in shipbuilding.However, as the mechanical properties of steel are improved, restrictions in heat input are often set thus limiting effective use of SAW, and probably therefore Manual Metal Arc (MMA) welding and manual Gas Metal Arc (GMA) welding are typically the processes mainly referenced in literature when welding steels with higher strength levels are studied. In this study, submerged arc welds on F40SW steel were made with overmatching tubular and solid welding wire at heat input levels above the normally recommended maximum of approximately 2,0 kJ/mm. Resulting welds were tested for mechanical properties with focus on toughness properties at low temperatures.Impact toughness KV 150 / 7,5 at -60°C was above 27J for both tested wires in the weld and at the heat affected zone (HAZ). Tested yield and tensile strength of the joints matched unwelded base material and all of the samples were broken at the base material far from the weld and HAZ area. Also the 180° bending tests for both surface- and rootside were passed without remarks. Based on the findings in this study, no obvious limitations for use of submerged arc welding in joining of arctic grade steel F40SW were observed. This encourages for increased use of SAW as economical and environmentally sound joining process for this kind of steel.
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| 7. |
- Ramjaun, T., et al.
(författare)
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Surface residual stresses in multipass welds produced using low transformation temperature filler alloys
- 2014
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Ingår i: Science and technology of welding and joining. - 1362-1718 .- 1743-2936. ; 19:7, s. 623-630
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Tidskriftsartikel (refereegranskat)abstract
- Tensile residual stresses at the surface of welded components are known to compromise fatigue resistance through the accelerated initiation of microcracks, especially at the weld toe. Inducement of compression in these regions is a common technique employed to enhance fatigue performance. Transformation plasticity has been established as a viable method to generate such compressive residual stresses in steel welds and exploits the phase transformation in welding filler alloys that transform at low temperature to compensate for accumulated thermal contraction strains. Neutron and X-ray diffraction have been used to determine the stress profiles that exist across the surface of plates welded with low transformation temperature welding alloys, with a particular focus on the stress at the weld toe. For the first time, near surface neutron diffraction data have shown the extent of local stress variation at the critical, fusion boundary location. Compression was evident for the three measurement orientations at the fusion boundaries. Compressive longitudinal residual stresses and tensile transverse stresses were measured in the weld metal.
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| 8. |
- Svensson, Lars-Erik, 1951-, et al.
(författare)
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Strength and Impact Toughness of High Strength Steel Weld Metals : Influence of Welding Method, Dilution and Cooling Rate
- 2015
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Ingår i: Proceedings of IIW International Conference, High-Strength Materials. - Helsingfors. ; , s. 1-9
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Konferensbidrag (refereegranskat)abstract
- Producing welds with properties matching those of the steel is a challenge at high strength levels. The present study has investigated how the choice of welding method affects weld metal mechanical properties through effects on dilution and cooling rate. Butt welds were produced in 12 mm plates in 777 MPa and 1193 MPa yield strength steels. Conventional arc welding methods including manual metal arc, gas metal arc welding, rapid arc welding and submerged arc welding were used as well as laser-gas metal arc hybrid welding. Filler materials with nominal yield strengths between 810 and 1000 MPa were used. Cooling times between 800 C and 500 C were varied between 5s and 15s and measured by insertion of thermocouples into the weld pool.High quality welds were produced efficiently with all welding methods even though dilution varied between 3%, for manual metal arc welding, to 73% for laser-hybrid welding. Low dilution, rapid cooling and single pass welding contributed to higher strength. Overmatching weld metal strength was achieved for the less strong steel and weld yield strengths of >1000 MPa were recorded for the stronger steel. Fracture in transverse tensile testing was always located in base material or HAZ. Impact toughness was higher for lower strength and low dilution. Results are discussed relating choice of welding method and cooling rate to weld metal properties for different steel strength levels.
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| 9. |
- Valiente Bermejo, María Asunción, 1972-, et al.
(författare)
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Effect of shielding gas on welding performance and properties of duplex and superduplex stainless steel welds
- 2015
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Ingår i: Welding in the World. - : Springer Science and Business Media LLC. - 0043-2288 .- 1878-6669. ; 59:2, s. 239-249
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Tidskriftsartikel (refereegranskat)abstract
- The influence of shielding gases on welding performanceand on properties of duplex and superduplex stainlesssteel welds was studied. Using argon as the reference gas,helium, nitrogen and carbon dioxide were added and fivemixtures evaluated. Bead-on-plate welds and circumferentialpipe welds were produced using mechanisedGMAwelding inthe downhand position. Welding performance, corrosion resistance,mechanical properties, microstructural features andweld imperfections were assessed and related to the shieldinggas. Shielding gases containing 30 % helium showed excellentresults; whilst pure argon showed unstable arc and poorweld pool fluidity and Ar+2 %CO2 resulted in underfill andporosity. Mixtures containing helium resulted in higher ductilitywelds and higher impact toughness values than weldsproduced with Ar+2 %CO2. Sound and balanced duplexmicrostructures free from intermetallics were found with suitableferrite contents for all the shielding gases studied. All theduplex pipe welds passed the corrosion test regardless of theshielding gas used, and the best results in the corrosion test forsuperduplex pipe welds were found when using Ar+30 %He+0.5 %CO2+1.8 %N2 as shielding gas.
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| 10. |
- Valiente Bermejo, María Asunción, 1972-, et al.
(författare)
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Exposure of FeCrAl Overlay Welds on Superheater Tubes : Influence of Local Environment on Degradation
- 2022
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Ingår i: Journal of Failure Analysis and Prevention. - : Springer. - 1547-7029 .- 1864-1245. ; 22:1, s. 400-408
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Tidskriftsartikel (refereegranskat)abstract
- Two experimental FeCrAl alloy overlay welds on tube shields were exposed in the superheater of a full-size waste fired boiler for 6 months. The tube shields were in different tube lines and positions within the superheater chamber to investigate possible heterogeneities in the exposure environment. The visual inspection of the exposed tube shields and the corrosion-erosion rates calculated from the analysis of cross-sections showed that the mid-length roof location experienced the most aggressive environment. The compositional differences between the two experimental alloys were not found to be determinant in their performance under these specific exposure conditions. It was concluded that erosion had a decisive influence on the results. The identification of local differences within the superheater chamber is important when deciding on the material selection for the different areas and locations to be protected. The output of this study is therefore interesting for further design consideration of superheaters as well as for future planning of exposures.
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