| 1. |
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| 2. |
- Åkerfeldt, Maria, 1982, et al.
(författare)
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Textile piezoelectric sensors – melt spun bi-component poly(vinylidene fluoride) fibres with conductive cores and poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) coating as the outer electrode
- 2014
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Ingår i: Fashion and Textiles. - : Springer Science and Business Media LLC. - 2198-0802. ; 1:1
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Tidskriftsartikel (refereegranskat)abstract
- The work presented here addresses the outer electroding of a fully textile piezoelectric strain sensor, consisting of bi-component fibre yarns of β-crystalline poly(vinylidene fluoride) (PVDF) sheath and conductive high density polyethylene (HDPE)/carbon black (CB) core as insertions in a woven textile, with conductive poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) coatings developed for textile applications. Two coatings, one with a polyurethane binder and one without, were compared for the application and evaluated as electrode material in piezoelectric testing, as well as tested for surface resistivity, tear strength, abrasion resistance and shear flexing. Both coatings served their function as the outer electrodes in the system and no difference in this regard was detected between them. Omission of the binder resulted in a surface resistivity one order of magnitude less, of 12.3 Ω/square, but the surface resistivity of these samples increased more upon abrasion than the samples coated with binder. The tear strength of the textile coated with binder decreased with one third compared to the uncoated substrate, whereas the tear strength of the coated textile without binder increased with the same amount. Surface resistivity measurements and scanning electron microscopy (SEM) images of the samples subjected to shear flexing showed that the coatings without the binder did not withstand this treatment, and that the samples with the binder managed this to a greater extent. In summary, both of the PEDOT:PSS coatings could be used as outer electrodes of the piezoelectric fibres, but inclusion of binder was found necessary for the durability of the coating.
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| 3. |
- Lindberg, Siv M, et al.
(författare)
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A product semantic study of the influence of the sense of touch on the evaluation of wood-based materials
- 2013
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197 .- 0261-3069. ; 52, s. 300-307
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Tidskriftsartikel (refereegranskat)abstract
- Based on product semantics, this study investigated how the tactile attributes of wood and wood-based composites are perceived and interpreted semantically. The wood-based samples included ash, birch, elm, oak, pine, OSB (oriented strand board), two wood pulp-reinforced polylactide composites, Comp A and B and one wood-fiber reinforced polypropene composite, Comp C. The subjects rated the samples by the descriptive words natural, exclusive, eco-. friendly, rough, inexpensive, reliable, warm, modern, snug and solid. The most significant differences between the samples were found for roughness and for the descriptors, reliable, natural and solid. A principal component analysis yielded three attributes based on the tactile perceptions: reliable, old-. fashioned and smooth. The solid wood pieces were perceived as natural and oak was perceived as being exclusive. The composite materials presented a greater variation in terms of perceived attributes than the wood specimens.
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| 4. |
- Andersson, Joel Håkan, 1981, et al.
(författare)
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Investigation of Homogenization and its Influence on the Repair Welding of Cast Allvac 718Plus
- 2010
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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
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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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| 5. |
- Andersson, Joel, 1981-, et al.
(författare)
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Hot Ductility Study of Haynes 282 Superalloy
- 2010
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Ingår i: Superalloy 718 and Derivatives. - Hoboken, NJ, USA : The Minerals, Metals, and Materials Society. - 9780470943168 ; , s. 539-554, s. 539-554
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Konferensbidrag (refereegranskat)
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| 6. |
- Andersson, Joel, 1981-, et al.
(författare)
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Metallurgical Response of Electron Beam Welded Allvac® 718Plus™
- 2011
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Ingår i: Hot Cracking Phenomena in Welds III. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642168635 ; , s. 415-428, s. 415-428
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Konferensbidrag (refereegranskat)abstract
- Electron beam welding of forged Allvac 718Plus superalloy has been carried out without any visible cracks in weld cross-sections. Healed cracks in the heat affected zone were, however, seen in most cross-sections with the healing as well as the cracking believed to be due to the constitutional liquation of the δ-phase. The δ-phase undergoes constitutional liquation in the Heat Affected Zone (HAZ) and consequently decreases the ductility of the material and renders cracks in the HAZ but due to the large amount of eutectic liquid produced at the same time the healing of the opened cracks takes place.
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| 7. |
- Matysiak, Hubert, et al.
(författare)
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Microstructure of Haynes® 282® Superalloy after Vacuum Induction Melting and Investment Casting of Thin-Walled Components
- 2013
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 6:11, s. 5016-5037
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to characterize the microstructure of the as-cast Haynes® 282® alloy. Observations and analyses were carried out using techniques such as X-ray diffraction (XRD), light microscopy (LM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray spectroscopy (EDS), wave length dispersive X-ray spectroscopy (WDS), auger electron spectroscopy (AES) and electron energy-loss spectrometry (EELS). The phases identified in the as-cast alloy include: γ (gamma matrix), γʹ (matrix strengthening phase), (TiMoCr)C (primary carbide), TiN (primary nitride), σ (sigma-TCP phase), (TiMo)2SC (carbosulphide) and a lamellar constituent consisting of molybdenum and chromium rich secondary carbide phase together with γ phase. Within the dendrites the γʹ appears mostly in the form of spherical, nanometric precipitates (74 nm), while coarser (113 nm) cubic γʹ precipitates are present in the interdendritic areas. Volume fraction content of the γʹ precipitates in the dendrites and interdendritic areas are 9.6% and 8.5%, respectively. Primary nitrides metallic nitrides (MN), are homogeneously dispersed in the as-cast microstructure, while primary carbides metallic carbides (MC), preferentially precipitate in interdendritic areas. Such preference is also observed in the case of globular σ phase. Lamellar constituents characterized as secondary carbides/γ phases were together with (TiMo)2SC phase always observed adjacent to σ phase precipitates. Crystallographic relations were established in-between the MC, σ, secondary carbides and γ/γʹ matrix.
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| 8. |
- Andersson, Joel, 1981-, et al.
(författare)
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Effect of Different Solution Heat Treatments on the Hot Ductility of Superalloys : Part 3 - Waspaloy
- 2013
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Ingår i: Materials Science and Technology. - 0267-0836 .- 1743-2847. ; 29:1, s. 43-53
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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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| 9. |
- Escalera, Edwin, et al.
(författare)
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Thermal treatment and phase formation in kaolinite and illite based clays from tropical regions of Bolivia
- 2012
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Ingår i: 6th EEIGM International Conference Advanced Materials Research. - Bristol : IOP Publishing Ltd.
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Konferensbidrag (refereegranskat)abstract
- The aim of this study was to compare the thermal behaviour of clays containing illite and kaolinite in various proportions. The clays contained small amounts of K and Fe, which act as fluxing agents. In order to investigate the phase formations during heating, the samples were examined in a differential scanning calorimeter at temperatures up to 1300°C. The thermal expansion of the samples was determined by dilatometer measurements from room temperature up to 1150°C. Phases were identified using x-ray diffraction and scanning electron microscopy. In all samples, most of the kaolinite was transformed into metakaolinite during heating up to 650°C, while illite remained unchanged up to 950°C. There was no influence of K and Fe on dehydroxylation. Metakaolinite formed at temperatures above 950°C leading to a Si-Al spinel. Furthermore, mullite was formed in the temperature interval 1050-1150°C. In this temperature range, the mechanism of mullite formation depended on the amount of K and Fe in the samples, changing the temperature of formation of mullite. It was observed by x-ray diffraction that most of the illite was transformed into a Si-Al spinel phase at 1050°C, and during further heating transformed into mullite. An increased amount of illite in the clays slightly decreased the melting temperature. The dilatometer measurements showed expansion and shrinkage for the dehydroxylation and spinel-phase formation, respectively.
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| 10. |
- Krakhmalev, Pavel, 1973-, et al.
(författare)
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Microstructure and properties of intermetallic composite coatings fabricated by selective laser melting of Ti-SiC powder mixtures
- 2014
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Ingår i: Intermetallics (Barking). - : Elsevier. - 0966-9795 .- 1879-0216. ; 46, s. 147-155
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Tidskriftsartikel (refereegranskat)abstract
- Transition metal silicides and carbides are attractive advanced materials possessing unique combinations of physical and mechanical properties. However, conventional synthesis of bulk intermetallics is a challenging task because of their high melting point. In the present research, titanium carbides and silicides composites were fabricated on the titanium substrate by a selective laser melting (SLM) of Ti -(20,30,40 wt.%)SiC powder mixtures by an Ytterbium fiber laser with 1.075 mu m wavelength, operating at 50 W power, with the laser scanning speed of 120 mm/s. Phase analysis of the fabricated coatings showed that the initial powders remelted and new multiphase structures containing TiCx, Ti5Si3C5, TiSi2 and SIC phases in situ formed. Investigation of the microstructure revealed two main types of inhomogeneities in the composites, (i) SiC particles at the interlayer interfaces and, (ii) chemical segregation of the elements in the central areas of the tracks. It was suggested and experimentally proven that an increase in laser power to 80 W was an efficient way to improve the laser penetration depth and the mass transport in the liquid phase, and therefore, to fabricate more homogeneous composite. The SLM Ti (20,30,40 wt.%)SiC composites demonstrated high hardness (11-17 GPa) and high abrasive wear resistance (3.99 x 10(-7)-9.51 x 10(-7) g/Nm) properties, promising for the applications involving abrasive wear. (C) 2013 Elsevier Ltd. All rights reserved.
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| 11. |
- Musalek, Radek, et al.
(författare)
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Fatigue Performance of TBC on Structural Steel Exposed to Cyclic Bending
- 2014
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Ingår i: Proceedings of the International Thermal Spray Conference. - : ASM International. ; , s. 880-885
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Konferensbidrag (refereegranskat)abstract
- For applications with variable loading, fatigue performance of coated parts is of utmost importance. In this study, fatigue performance of conventional structural steel coated with thermal barrier coating (TBC) was evaluated in cyclic bending mode by "SF-Test" device. Testing was carried out for as-received and grit-blasted substrates, as well as for samples with Ni-based bond-coat and bond-coat with YSZ-based top-coat. Comparison of results obtained for different loading amplitudes supplemented by fractographic analysis enabled identification of dominating failure mechanisms and evaluation of fatigue resistance alteration due to the deposited coatings.
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| 12. |
- Oikonomou, Christos, 1980, et al.
(författare)
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Evaluation of the thickness and roughness of homogeneous surface layers on spherical and irregular powder particles
- 2014
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Ingår i: Surface and Interface Analysis. - : John Wiley & Sons. - 0142-2421 .- 1096-9918. ; 46:10-11, s. 1028-1032
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Tidskriftsartikel (refereegranskat)abstract
- The present study describes the development of a theoretical model for estimating the thickness of homogeneous surface layers on spherical and irregular shaped powder particles using the XPS depth profiling. As opposed to flat surfaces, such an approach for substrates of specific geometry is not straightforward. One needs to consider those geometrical factors associated with the experimental setup and sample's roughness, which impose an angle dependence on the photoelectrons peak intensity, X-ray flux and ion etch rate over the surface in question in order to evaluate it. The novelty of the current model lies in the introduction of geometrical freedom in connection to the experimental arrangement, which can be tailored to match the needs of contemporary instruments. The model was evaluated experimentally by analyzing the surface oxide layers on metal powder grades of different morphology. Complementary analytical techniques such as high resolution (HR) SEM and focused ion beam (FIB) were used in combination to further characterize the surface layers prior to the XPS investigations. The results reveal that the estimation of the oxide/metal interface from the measured relative metal intensity signal as function of etch depth using the model is in extremely good agreement with the corresponding values from direct measurement of HR SEM on FIB cross-sectioned powder samples. The model deviates slightly only for the irregular shaped powder, which can be regarded as means for quantification of surface roughness of the material. The model is used as a basis for a computer software that estimates the thickness of surface layers for powdered materials.
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| 13. |
- Sandin, Gustav A, 1983, et al.
(författare)
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Environmental evaluation of a clear coating for wood: toxicological testing and life cycle assessment
- 2012
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Ingår i: PRA's 8th International Woodcoatings Congress (oral presentation and confereence proceeding paper).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- WoodLife is an on-going project under the EU Seventh Framework Programme aimed at developing a water-based clear coating for exterior wood products. Adding nanoparticles to a conventional coating could improve its UV-protecting properties, thus decreasing the need for maintenance of coated wood products. Wood products could thereby replace non-wood alternatives, which could result in lower environmental impacts.This paper describes an environmental evaluation carried out within the WoodLife project, in which we test whether the nanoparticles are toxic for the bacteria Vibrio fischeri, and use Life Cycle Assessment (LCA) to map the environmental consequences of applying the coating on a wood product. This goes beyond the scope of most environmental evaluations of nanotechnologies, which tend to include either an assessment of the possible toxicity of the nanomaterial or an LCA.The toxicological testing indicates low ecotoxicity of the nanoparticles, but further development of suitable testing methods is warranted to enable a full ecotoxicological evaluation. The LCA shows that a wooden window frame with the new coating can be environmentally superior to plastic and aluminium window frames. However, the potential in part depends on variables such as recycling rates and disposal practices, which are highly uncertain for future products with long service lives.
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| 14. |
- Wanner, Bertil, 1963-, et al.
(författare)
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Cutter Exit Effects during Milling of Thin-walled Inconel 718
- 2012
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Ingår i: Advanced Materials Research. - : Trans Tech Publications Inc.. - 1022-6680 .- 1662-8985. ; 590, s. 297-308, s. 297-308
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Tidskriftsartikel (refereegranskat)abstract
- During milling of thin-walled components, chatter vibrations give rise to process issues. These include dimensional inaccuracy, damaged and scrap parts, and damaged cutting tools. This, in turn, leads to loss of production time with increasing cost as a consequence. This paper identifies the force profile during a single cut milling process. It focuses on the exit and post-exit behavior of the cut and discusses the process dynamics. The force profiles of various tool-to-workpiece positions are analyzed as regards the exit and post exit phases. A standard on-the-market cutter and a specially designed zero rake cutter are used in the investigation. Finally, a time-domain simulation of the force is performed and compared to the experimental results. The study concludes that a small change in exit angle may result in a considerable improvement in cutting behavior. In addition, the tool position should be chosen so that the cutter exits in the least flexible direction possible for the workpiece.
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| 15. |
- Wanner, Bertil, 1963-, et al.
(författare)
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Milling Strategies for Thin-walled Components
- 2012
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Ingår i: Advanced Materials Research. - : Trans Tech Publications Inc.. - 1022-6680 .- 1662-8985. ; 498, s. 177-182, s. 177-182
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Tidskriftsartikel (refereegranskat)abstract
- Recent developments in the Aerospace industry have led to thin-walled, reduced-weight engine designs. Due to demands in manufacturing, production speeds and material removal rates (MRR) have increased. As component wall thickness gets thinner, the consequence oftentimes is an increase in chatter vibrations. This paper suggests that a correctly chosen tool-to-workpiece offset geometry may lead to a robust and chatter-free process. The results show the differences in force response for three geometries while varying the overhang of the workpiece. This is part of a concerted effort to develop a robust methodology for the prediction of chatter vibrations during milling operations of thin-walled Aerospace components. This paper outlines certain robust machining practices. It also analyzes the criticality of the choice of offset between tool and workpiece during milling setup as well as the effects that the entry and exit of cut have on system vibrations.
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| 16. |
- Pavlopoulou, E., et al.
(författare)
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Phase separation-driven stratification in conventional and inverted P3HT:PCBM organic solar cells
- 2013
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Ingår i: Organic electronics. - : Elsevier BV. - 1566-1199 .- 1878-5530. ; 14:5, s. 1249-1254
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Tidskriftsartikel (refereegranskat)abstract
- We have used neutron reflectivity to investigate the stratification of poly(3-hexylthiophene) (P3HT) and phenyl-C-61-butyric acid methyl ester (PCBM) blend films. Films were spun-cast on poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) and titanium oxide (TiOx) layers to mimic the procedures followed for the fabrication of conventional and inverted organic photovoltaics respectively. The resultant scattering length density profiles reveal a PCBM-rich layer is formed in the vicinity of PEDOT: PSS or TiOx, while PCBM is depleted at the free surface of the film. PCBM segregation close to the substrate is further enhanced by annealing. This stratification is considered to be favorable only for inverted devices. (C) 2013 Elsevier B. V. All rights reserved.
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| 17. |
- Wandebäck, Fredrik, et al.
(författare)
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Variation Feedback and 3D Visualization of Geometrical Inspection Data
- 2010
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Ingår i: Proceedings of the ASME 2009 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE, August 30 - September 2, 2009, San Diego, California, USA. - 9780791849057 ; 8, s. 197-208
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Konferensbidrag (refereegranskat)abstract
- There is no type of manufacturing process that is not afflicted by variation. Activities intended to ensure the quality of a company's geometry processes are usually referred to as geometry assurance activities. One clear industrial problem is to understand the relations between the products concept and the manufacturing process. Dimensional data is a very important source of experience of how a product's geometry has worked in the interaction with the actual manufacturing system. Users therefore need good analysis and presentation tools of geometry outcomes to support both the product developers and production engineers in the analysis of the production output and its consequences. Today the dimensional data can be difficult to obtain or access, and is not necessarily presented in such a way as to provide the user with all necessary information. This paper presents how presentation and analysis tools of geometrical inspection data can be taken a step further. New functionality for feature based 3D visualization of inspection data has been developed which integrates the variation simulation platform and the inspection data database. The goal has been to create better tools for analysis of geometrical variation and increase the understanding of the sources of variation.
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| 18. |
- Fahlström, Karl, et al.
(författare)
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Minimization of distortions during laser welding of ultra-high strength steel
- 2014
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Ingår i: ICALEO 2014 Congress proceedings. ; , s. 1-10
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Konferensbidrag (refereegranskat)abstract
- Ultra high strength steels are frequently used within the automotive industry for several components. Welding of these components is traditionally done by resistance spot welding, but to get further productivity and increased strength, laser welding has been introduced in the past decades. Fusion welding is known to cause distortions due to built-in stresses in the material. The distortions result in geometrical issues during assembly which become the origin of low joint quality due to gaps and misfits.U-beam structures of boron steel simulating B-pillars have been welded with laser along the flanges. Welding parameters and clamping have been varied to create different welding sequences and heat input generating a range of distortion levels. The distortions have been recorded dynamically with an optical measurement system during welding. In addition, final distortions have been measured by a digital Vernier caliper. The combined measurements give the possibility to evaluate development, occurrence and magnitude of distortions with high accuracy. Furthermore, section cuts have been analyzed to assess joint geometry and metallurgy.The results shows that final distortions appear in the range of 0-8 mm. Distortions occur mainly transversely and vertically along the profile. Variations in heat input show clear correlation with the magnitude of distortions and level of joint quality. A higher heat input in general generates a higher level of distortion with the same clamping conditions. Section cuts show that weld width and penetration are significantly affected by welding heat input.The present study identifies parameters which significantly influence the magnitude and distribution of distortions. Also, effective measures to minimize distortions and maintain or improve joint quality have been proposed.Finally, transient FE simulations have been presented which show the behavior of the profiles during the welding and unclamping process.
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| 19. |
- Jiang, Janna, 1978-, et al.
(författare)
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Numerical modelling of the compression behaviour of single-crystalline MAX-phase materials
- 2010
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Ingår i: Advanced materials research. - : Trans Tech Publications. - 1022-6680. ; 89-91, s. 262-267
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Tidskriftsartikel (refereegranskat)abstract
- In this article a numerical model to describe the mechanical behaviour of nanophased singlecrystalline Ti3SiC2 is proposed. The approach is a two dimensional finite element periodic unit cell consisting of an elastic matrix interlayered with shear deformable slip planes which obey the Hill's yield criterion. The periodic unit cell is used to predict compression material behaviour of Ti3SiC2 crystals with arbitrary slip plane orientations. Stress strain relationships are derived for Ti 3SiC2, and the effect of slip plane volume fraction as well as orientation of the slip planes are investigated. The two main deformation mechanisms of the material namely; ordinary slip and so called kinking are considered in the study.
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| 20. |
- Lööf, Johan, 1979, et al.
(författare)
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Optimizing Locator Position to Maximize Robustness in Critical Product Dimensions
- 2010
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Ingår i: ASME 2009 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, IDETC/CIE2009; San Diego, CA; United States; 30 August 2009 through 2 September 2009. - 9780791848999 ; 2:PARTS A AND B, s. 515-522
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Konferensbidrag (refereegranskat)abstract
- The way parts are located in relation to each other or in fixtures is critical for how geometrical variation will propagate and cause variation in critical product dimensions. Therefore, more emphasis should be put on this activity in early design phases in order to avoid assembly and production problems later on. In earlier literature, locator positions have been defined using optimization to reach a robust locating scheme. This implies that the total robustness of a part is optimized by placing the locators in an optimal way. Sometimes there are areas on parts that are more sensitive to variation than others. Therefore, this paper suggests an approach for optimizing the positions of locators in a locating scheme to maximize robustness in defined critical dimensions. A formulation of an optimization problem is presented, and an algorithm solving this in a heuristic approach is developed. Finally, this algorithm is applied on an industrial example.
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| 21. |
- Ryttberg, Kristina, 1977, et al.
(författare)
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The effect of cold ring rolling on the evolution of microstructure and texture in 100Cr6 steel
- 2010
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Ingår i: Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing. - : Elsevier BV. - 0921-5093. ; 527:9, s. 2431-2436
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Tidskriftsartikel (refereegranskat)abstract
- This paper concerns the development of microstructure and texture during cold ring rolling of 100Cr6 steel rings with starting rectangular cross-sections. By interrupting the rolling process at pre-defined intervals expansion ratios ranging from 1.05 to 1.5 were achieved resulting in varying degrees of deformation of the rings. Results for rings with a simple rectangular cross-section were compared with results for a cold rolled ring with a more complex cross-section. By combining results from optical and scanning electron microscopy with hardness measurements the two different ring shapes were shown to display similar material flow during cold ring rolling. The deformation was most severe near the inner diameterof the rings decreasing towards the area of the outer diameter. By employing electron back scatter diffraction (EBSD) the ring rolling process was shown to change the {111}-fibre texture of the ring blanks to a {110} texture. This implies a mixture of both shear and compressive deformation during rolling.
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| 22. |
- Tam, Eric, 1980, et al.
(författare)
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XRD and XPS Characterisation of Transition Metal Silicide Thin Films
- 2012
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 606:3-4, s. 329-336
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Tidskriftsartikel (refereegranskat)abstract
- Binary transition metal silicides based on the systems Ti-Si, Fe-Si, Ni-Si and Cr-Si were fabricated on Si wafers by means of ion-beam co-sputter deposition and subsequent annealing. The crystalline structures of the phases formed were identified from the characteristic patterns acquired by means of X-ray diffraction (XRD) measurements. The phase formation sequences were described by means of the Pretorius’ effective heat of formation (EHF) model. For the Ti-Si, Fe-Si and Ni-Si systems, single phase thin films of TiSi2, β-FeSi2 and NiSi2 were generated as the model predicts, while a mixture of CrSi + CrSi2 phases was obtained for the Cr-Si system. The surface chemical condition of individual specimens were analysed by using X-ray photoelectron spectroscopy (XPS). The chemical shifts of transition metal 2p3/2 peaks from their metallic to silicide states were depicted by means of the Auger parameters and the Wagner plots. The positive chemical shift of 2.0 eV for Ni 2p3/2 peak of NiSi2 is mainly governed by the initial-state effects. For the other silicide specimens, the initial-state and final-state effects may oppose one another with similar impact. Consequently, smaller binding energy shifts of both negative and positive character are noted; a positive binding energy shift of 0.3 eV for the Fe 2p3/2 level was shown for β-FeSi2 and negative binding energy shifts of 0.1 and 0.3 eV were determined for CrSi + CrSi2 and TiSi2, respectively.
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| 23. |
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| 24. |
- Sarius, N.G., et al.
(författare)
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Electroplating of nickel in grooves under the influence of low and medium frequency ultrasound
- 2011
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Ingår i: Journal for Electrochemistry and Plating Technology. - 1866-7406. ; 1:3, s. 19-28
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Tidskriftsartikel (refereegranskat)abstract
- The effect of ultrasonics on filling properties has been studied by Ni electroplating from a sulphamate electrolyte in high aspect ratio grooves. The experiments have been performed with two different modes of ultrasound: a) 25 kHz ultrasound with an effect of 225 W directed perpendicular to the substrate surface; b) ultrasonic standing waves of 100 kHz and 400 kHz parallel to the substrate surface. It was found that both methods improve the filling in grooves that are between 0.35 and 1 mm wide with aspect ratios between 0.6 and 3, compared to electroplating with conventional agitation. Under the investigated conditions the 400 kHz standing wave parallel to the surface was most efficient to improve filling of grooves.
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| 25. |
- Sarius, N.G., et al.
(författare)
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Influence of ultrasound and cathode rotation on the formation of intrinsic stress in Ni films during electrodeposition
- 2011
-
Ingår i: Transactions of the Institute of Metal Finishing. - 0020-2967 .- 1745-9192. ; 89:3, s. 137-142
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Tidskriftsartikel (refereegranskat)abstract
- The influence of 25 kHz ultrasound and cathode rotation during electroplating of Ni films on Si wafers has been studied with respect to intrinsic stress formation. Current densities from 1·6 up to 28·3 A dm−2 were used in an additive free Ni sulphamate electrolyte. In general, more efficient agitation by either ultrasound or cathode rotation was found to reduce intrinsic stress towards compressive levels compared with conventional agitation with an electrolyte circulation pump. Furthermore, intrinsic stresses become less dependent on changes in current density. The latter effect is most pronounced for ultrasonic agitation. Structure analysis of samples deposited by ultrasonic agitation shows dense deposits with initially smaller grains at high ultrasonic effect. Locally increased temperature at the substrate surface could be an important effect of ultrasound agitation.
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| 26. |
- Runnemalm, Anna, 1970-, et al.
(författare)
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Automatic Inspection of Spot Welds by Thermography
- 2014
-
Ingår i: Journal of nondestructive evaluation. - : Springer Science and Business Media LLC. - 0195-9298 .- 1573-4862. ; 33:3, s. 398-406
-
Tidskriftsartikel (refereegranskat)abstract
- The interest for thermography as a method for spot weld inspection has increased during the last years since it is a full-field method suitable for automatic inspection. Thermography systems can be developed in different ways, with different physical setups, excitation sources, and image analysis algorithms. In this paper we suggest a single-sided setup of a thermography system using a flash lamp as excitation source. The analysis algorithm aims to find the spatial region in the acquired images corresponding to the successfully welded area, i.e., the nugget size. Experiments show that the system is able to detect spot welds, measure the nugget diameter, and based on the information also separate a spot weld from a stick weld. The system is capable to inspect more than four spot welds per minute, and has potential for an automatic non-destructive system for spot weld inspection. The development opportunities are significant, since the algorithm used in the initial analysis is rather simplified. Moreover, further evaluation of alternative excitation sources can potentially improve the performance.
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| 27. |
- Curry, Nicholas, 1984-
(författare)
-
Design of Thermal Barrier Coating Systems
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thermal barrier coatings (TBC’s) are used to provide both thermal insulation and oxidation protection to high temperature components within gas turbines. The development of turbines for power generation and aviation has led to designs where the operation conditions exceed the upper limits of most conventional engineering materials. As a result there has been a drive to improve thermal barrier coatings to allow the turbine to operate hotter for longer.The focus of this study has been the development of a new generation of TBC system for industrial implementation. The goal for these new coatings was to achieve lower conductivity and longer lifetime than those coatings used today. The route taken to achieve these goals has been twofold. Firstly an alternative stabiliser has been chosen for the zirconium oxide system in the form of dysprosia. Secondly, Control of the powder morphology and spray parameters has been used to generate coating microstructures with favourable levels of porosity.Samples have been heavily characterised using the laser flash technique for evaluation of thermal properties. Measurements were performed at room temperature and at intervals up to 1200°C. Samples have also been tested in their as produced state and after heat treatments of up to 200 hours.Lifetime evaluation has been performed using the thermo-cyclic fatigue test to expose coating systems to successive cycles of heating and cooling combined with oxidation of the underlying metallic coating.Microstructures have been prepared and analysed using SEM. An image analysis routine has been used to attempt to quantify changes in microstructure features between coating types or coating exposure times and to relate those changes to changes in thermal propertiesResults show that dysprosia as an alternative dopant gives a reduction in thermal conductivity. While small at room temperature and in the as produced state; the influence becomes more pronounced at high temperatures and with thermal exposure time. Overall, the greatest sustained influence on thermal conductivity has been from creating coatings with high levels of porosity.In relation to lifetime, the target of double the thermo-cyclic fatigue life was achieved using a coating with engineered porosity. Introducing a polymer to the spray powder helps to generate large globular pores within the coating together with a large number of delaminations. Such a structure has shown to be highly resistant to TCF testing.
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| 28. |
- Gschösser, Florian, et al.
(författare)
-
Hidden Ecological Potentials in the Production of Materials for Swiss Road Pavements
- 2012
-
Ingår i: Journal of Management in Engineering - ASCE. - 0742-597X. ; 27:1, s. 13-21
-
Tidskriftsartikel (refereegranskat)abstract
- Sustainability has become a major concern in the field of civil infrastructures in recent years. Developing road construction projects with lower ecological impacts over a project’s entire life cycle can help in making road infrastructure contribute to sustainable development. This study focuses on the ecological potentials in the production of road materials used in Swiss road pavements. The environmental assessment was performed using a cradle-to-gate life-cycle assessment (LCA) approach in which all processes from the raw material extraction to the finished product were considered. The comparison of the results of the best-case asphalt pavement and the standard asphalt pavement for Swiss highway construction shows ecological potentials of up to 55%. Use of the best-case concrete pavement lowers the environmental impact by up to 53% in comparison to the worst-case concrete pavement for Swiss highways. Concerning composite pavements, the best-case variant offers an ecological potential 38% higher than the standard pavement.
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| 29. |
- Hosseini, Seyed, 1981, et al.
(författare)
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A Methodology for Temperature Correction When Using Two-Color Pyrometers : Compensation for Surface Topography and Material
- 2014
-
Ingår i: Experimental mechanics. - : Springer Science and Business Media LLC. - 0014-4851 .- 1741-2765. ; 54:3, s. 369-377
-
Tidskriftsartikel (refereegranskat)abstract
- In this investigation, the applicability of the two-color pyrometer technique for temperature measurements in dry hard turning of AISI 52100 steel was studied, where both machined surfaces as well as cutting tools were considered. The impacts of differing hard turned surface topography on the two-color pyrometer readings was studied by conducting temperature measurements on reference samples created using cutting tools with different degrees of tool flank wear. In order to conduct measurements in a controlled environment, a specially designed furnace was developed in which the samples were heated step-wise up to 1,000 °C in a protective atmosphere. At each testing temperature, the temperatures measured by the two-color pyrometer were compared with temperatures recorded by thermocouples. For all materials and surfaces as studied here, the two-color pyrometer generally recorded significantly lower temperatures than the thermocouples; for the hard turned surfaces, depending on the surface topography, the temperatures were as much as 20 % lower and for the CBN cutting tools, 13 % lower. To be able to use the two-color pyrometer technique for temperature measurements in hard turning of AISI 52100 steel, a linear approximation function was determined resulting in three unique equations, one for each of the studied materials and surfaces. By using the developed approximation function, the measured cutting temperatures can be adjusted to compensate for differing materials or surface topographies for comparable machining conditions. Even though the proposed equations are unique for the hard turning conditions as studied here, the proposed methodology can be applied to determine the temperature compensation required for other surface topographies, as well as other materials. © 2013 Society for Experimental Mechanics.
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| 30. |
- Nilsson, Håkan, 1971, et al.
(författare)
-
Implementation of a 3D solver for electric arc welding, coupling fluid mechanics with electromagentics
- 2011
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Ingår i: 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics. HEFAT2011. ; , s. 614-620
-
Konferensbidrag (refereegranskat)abstract
- This paper describes the implementation of a 3D numerical solver for electric arc welding, where the fluid mechanics of the shielding gas is strongly influenced by the electromagnetic fields. The implementation is done in the OpenFOAM-1.6.x OpenSource Computational Fluid Dynamics (CFD) tool (www.openfoam.com). OpenFOAM is basically a general library of C++ classes for numerical simulation of continuum mechanic problems, but it is mainly used in CFD. The basics of high-level programming in OpenFOAM is described briefly, while the main components of the implementation done in the present work are described in high detail. The implementation is validated against an analytical solution of the electromagnetic field of an infinite electrically conducting rod, and against an experimental study of GTAW (Gas Tungsten Arc Welding). The numerical results agree very well with both the analytical and experimental results. A grid-dependency study has been made for the GTAW case, showing that the main features of the presented solutions are independent of the mesh size.
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| 31. |
- Nylén, Per, 1960-, et al.
(författare)
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Relationships between Process Parameters, Microstructure and Adhesion Strength of HVOF Sprayed IN718 Coating
- 2010
-
Ingår i: Proceedings of the 2010 International Thermal Spray Conference. - : Springer Science and Business Media LLC. - 9783871555909 ; , s. 1-7
-
Konferensbidrag (refereegranskat)abstract
- Fundamental understanding of relationships between process parameters, particle in-flight characteristics, and adhesion strength of HVOF sprayed coatings is important to achieve the high coating adhesion that is needed in aeronautic repair applications. In this study, statistical Design of Experiments (DoE) was used to identify the most important process parameters that influence adhesion strength of IN718 coatings sprayed on IN718 substrates. Special attention was given to the parameters combustion ratio, total gas mass flow, stand-off distance and external cooling, since these parameters were assumed to have a significant influence on particle temperature and velocity. Relationships between these parameters and coating microstructure were evaluated to fundamentally understand the relationships between process parameters and adhesion strength.
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| 32. |
- Åstrand, Erik, 1981-
(författare)
-
Weld Procedures and Demands for Improved Fatigue Strength of Single Load Carrying Fillet Welds
- 2013
-
Ingår i: Trends in Welding Research. - Chicago : ASM International. - 9781627089982 ; , s. 798-804
-
Konferensbidrag (refereegranskat)abstract
- Traditional weld demands on throat size and leg length does not support a welding process for improved penetration. This paper includes theoretical analysis of welded samples showing the potential with welds that have a prescribed asymmetry. Weld with a larger leg length against the web plate offer in this study improved fatigue properties and could also offer potential for reduced welding time, a smaller amount of filler material and potentially make the quality inspection more relevant. Copyright © 2013 ASM International® All rights reserved.
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| 33. |
- Öberg, Anna, 1979, et al.
(författare)
-
The right evaluation method - an enabler for process improvement
- 2013
-
Ingår i: International Conference on Joining Materials, 5-8 May 2013, Helsingor. - : JOM-Institute.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper aims at describing the procedure where an alternative evaluation process was developed to support the improvement of both welding and weld quality evaluation. Welded structures are important when striving for reduced fuel consumption due to vehicle weight. Hence good control of the fabrication process is critical to keep welding performance on target, avoiding waste in terms of added weight and overproduction. The resulting distribution of weld weight has shown to be an important control parameter in the sense of keeping cost down.To identify the causes for deviations between actual and theoretical weld weight, information about the weld was needed. The currently used evaluation method showed not to be capable of giving the information needed. It was necessary to know the throat size as well as weld geometry. The current evaluation method introduced more variation due to the measurement than the actual fabrication process itself, leading to drift of process target and overproduction.To fulfil the need of information, that different functions within the company had, a PULL-approach was used. The information need, information presentation and sequence were outlined for each information receiver individually. An alternative measurement method was developed and named WIA – Weld Impression Analysis. The method consists of two parts; creating the replica and analysing the shape in an image analysis program.The method was tested to see if it was capable of delivering accurate and precise measurements, satisfying repeatability and reproducibility requirements for this particular situation. A thorough measurement system analysis was carried out. The measurement system assigned 98.98% of the total variation to part-to-part variation corresponding to long-term process variation. The variation that stems from taking the impressions and preparing them was as well investigated, also showing satisfying results. Finally it was investigated if the impressions reflect the true shape of the welds accurately. The results showed a tendency of slightly higher cross sectional areas in the range of 0-3 %. This however indicated that the accuracy of the measurement system was sufficient for its purpose.The PULL-approach generated a sufficient method which enabled the possibility to perform process improvement and gain large production cost savings.
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| 34. |
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| 35. |
- Andersson, Joel, 1981-, et al.
(författare)
-
Effect of solution heat treatments on superalloys : Part 1 – alloy 718
- 2012
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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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| 36. |
- 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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| 37. |
- Andersson, Joel, 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. - : Taylor & Francis Group. - 1362-1718 .- 1743-2936. ; 17:1, s. 49-59
-
Tidskriftsartikel (refereegranskat)abstract
- The ability to weld repair three precipitation hardening superalloys, i.e. Alloy 718, Allvac 718Plus and Waspaloy, with gas tungsten 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 954uC–1 h, 982uC–1 h, 954uC–15 h and 1020uC–1 h and Waspaloy for 4 h at 996uC, 1010uC, 1040uC and at 1080uC. By metallography, the total number of cracks was evaluated in both the heat affected zone and the fusion zone, 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 heat affected zone cracking behaviour.
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| 38. |
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| 39. |
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| 40. |
- De Oro Calderón, Raquel, 1982, et al.
(författare)
-
Surface phenomena during the early stages of sintering in steels modified with Fe–Mn–Si–C master alloys
- 2013
-
Ingår i: Materials Characterization. - : Elsevier BV. - 1044-5803. ; 86, s. 80-91
-
Tidskriftsartikel (refereegranskat)abstract
- The characteristics of the metallic powder surface play a critical role in the development of strong bonds between particles during sintering, especially when introducing elements with a high affinity for oxygen. In this study, Mn and Si have been combined in a Fe–Mn–Si–C master alloy powder in order to reduce their chemical activity and prevent oxidation during the heating stage of the sintering process. However, when this master alloy powder is mixed with an iron base powder, differences in chemical activity between both components can lead to an oxygen transfer from the iron base powder to the surface of the master alloy particles. The present research is focused on studying the evolution of the master alloy particle surface during the early stages of sintering. Surface characterization by X-ray Photoelectron Spectroscopy (XPS) shows that the master alloy powder surface is mostly covered by a thin easily reducible iron oxide layer (~ 1 nm). Mn–Si particulate oxides are found as inclusions in specific areas of the surface. Evolution of oxides during sintering was studied on green compacts containing iron powder, graphite and Fe–Mn–Si–C master alloy powder that were heat treated in vacuum (10− 6 mbar) at different temperatures (from 400, 600, 800 to 1000 °C) and analyzed by means of XPS. Vacuum sintering provides the necessary conditions to remove manganese and silicon oxides from the powder surface in the range of temperatures between 600 °C and 1000 °C. When sintering in vacuum, since the gaseous products from reduction processes are continuously eliminated, oxidation of master alloy particles due to oxygen transfer through the atmosphere is minimized.
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| 41. |
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| 42. |
- Karamchedu, Seshendra, 1987
(författare)
-
Delubrication of Chromium Prealloyed Powder Metallurgy Steels
- 2013
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Consolidation of steel components produced by means of powder metallurgy (PM) is achieved typically through compaction and sintering. During consolidation, final dimensions of the part are already achieved after compaction, while sintering imparts strength to the components. Prior to the compaction stage, lubricants are added to the metal powder to reduce the inter-particle and die-wall friction during pressing and hence improve powder compressibility and ejection of the component from the compaction tool. These lubricants have to be safely removed after compaction since they are source of oxygen and carbon that can negatively affect further sintering process as well as final performance of the sintered components. Lubricants commonly used for PM steels are based on ethylene bis-stearamide (EBS) and their removal is achieved through thermolysis in the initial zone of the sintering furnace. With increasing demands on the achievable densities and performance of PM components, lubricants and possible risks of improper delubrication have received interest. Among the problems encountered during sintering, those concerning delubrication are frequent but difficult to detect. Hence previous studies have aimed at improving the efficiency of lubricant removal and predicting the same. Delubrication being a complex process still poses problems in practice and its proper control requires a system which monitors the delubrication sequence and can be incorporated into a closed loop control.In the present work, a reliable approach for in-situ monitoring of delubrication of PM steel compacts is presented. The method is based on continuous monitoring of the processing atmosphere using sensors commonly used in the industry (CO2 and O2). It was demonstrated that the initial stages of lubricant removal can be monitored using the oxygen sensor based on zirconia ceramics and the later stages can be detected utilizing CO2 sensor based on infrared cell technology. Based on the established methodology, a systematic study on the effect of various process parameters on lubricant removal in the processing of chromium prealloyed PM steels has been conducted. Effect of temperature, holding time, heating rate, process gas composition (inert, reducing and oxygen containing atmospheres) and purity (wet and dry gases), flow rate and graphite addition was evaluated. Additionally, change in surface chemistry of the base powder occurring during delubrication and its effect on sintering have been studied using X-ray photoelectron spectroscopy and scanning electron microscopy combined with the energy dispersive X-ray analysis. Based on the experimental results it is recommended to perform delubrication at ~ 450 °C applying low heating rates in dry-nitrogen atmosphere with flow sufficient enough to provide dynamic gas conditions around the component surface. This is especially important in the case of powder prealloyed with oxygen sensitive elements like chromium.
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| 43. |
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| 44. |
- Ramjaun, T., et al.
(författare)
-
Effect of interpass temperature on residual stresses in multipass welds produced using low transformation temperature filler alloy
- 2014
-
Ingår i: Science and technology of welding and joining. - 1362-1718 .- 1743-2936. ; 19:1, s. 44-51
-
Tidskriftsartikel (refereegranskat)abstract
- Weld filler alloys that exploit transformation plasticity through low austenite to martensite transformation temperatures offer an effective method of reducing residual stresses in strong steel welds. However, in multipass welds, the heat input from later weld passes may be insufficient to retransform prior welding passes, leading to the accumulation of thermally induced strains and elevated residual stresses. In this work, the residual stress distributions produced around arc welds fabricated with a martensitic weld filler alloy that transforms at a low temperature have been studied as a function of the number of passes deposited and the interpass temperature. It is found that when the interpass temperature is above the transformation temperature of the weld metal, the entire multipass weld transforms as a single entity, thus permitting the optimum exploitation of the transformation plasticity. In contrast, the deposition of new metal with a relatively low interpass temperature leads to increased residual stresses in the underlying layers, reducing or eliminating the beneficial stress states previously created.
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| 45. |
- Ramjaun, T., et al.
(författare)
-
Effects of dilution and baseplate strength on stress distributions in multipass welds deposited using low transformation temperature filler alloys
- 2014
-
Ingår i: Science and technology of welding and joining. - 1362-1718 .- 1743-2936. ; 19:6, s. 461-467
-
Tidskriftsartikel (refereegranskat)abstract
- Transformation plasticity can be utilised to control residual stresses in steel welds. This requires special filler alloys that transform at a sufficiently low temperature to compensate for accumulated thermal contraction strains. However, the welding parameters needed to optimise the effect in multipass joints have yet to be established. This topic has been investigated by characterising the residual stress distribution in multipass welds fabricated with different welding alloys and baseplates using neutron diffraction to assess the effects of dilution and baseplate strength. While the use of richly alloyed weld metal does enhance fatigue performance in single pass joints, the extent of stress relief that can be derived from transformation plasticity is reduced due to incomplete martensitic transformation when further layers are deposited. For all cases studied, compressive stresses were measured in the weld metal with balancing tensile stress in the heat affected zone of the plate. The magnitude of the tension was observed to be a function of the strength of the baseplate. Recommendations are also presented for the combination of welding and material parameters that lead to the optimum exploitation of transformation plasticity as a method for boosting the fatigue performance of multipass welded joints.
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| 46. |
- Ramjaun, T., et al.
(författare)
-
Surface residual stresses in multipass welds produced using low transformation temperature filler alloys
- 2014
-
Ingår i: Science and technology of welding and joining. - 1362-1718 .- 1743-2936. ; 19:7, s. 623-630
-
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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| 47. |
- Steffenburg-Nordenström, Joachim, 1962-, et al.
(författare)
-
Simulation of the influence of forming on residual stresses and deformations after welding and heat treatment in Alloy 718
- 2014
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Manufacturing of components in aero engines requires attention to residual stress and final shape of the product in order to meet high quality product standards. This sets very high demands on involved manufacturing steps. The manufacturing of a V-shaped leading edge of a vane is simulated. It is made of Alloy718, which is a nickel based heat resistant material commonly used in aerospace components. The manufacturing process chain consists of forming, welding and heat treatment. The results show that the remaining residual stresses after a manufacturing process chain are affected when the residual history from the formingprocess is considered. The residual stress decrease after heat treatment is about 55-65%. Moreover, the von Mises stress profile through thickness at the centre of the radius at the weld joint is about 25% higher when full forming history is considered.
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| 48. |
- Stenbacka, Nils, 1947-
(författare)
-
Kan man svetsa i äldre stålkonstruktioner
- 2011
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Ingår i: Stålbyggnad. - Stockholm : Stålbyggnadsinstitutet. - 1404-9414. ; :3, s. 52-54
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 49. |
- Tano, Ingrid, 1968-, et al.
(författare)
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Relationships between Coating Microstructure and Thermal Conductivity in Thermal Barrier Coatings – A modelling Approach
- 2010
-
Ingår i: International Thermal Spray Conference and Exposition, ITCS Singapore 2010. - Düsseldorft : DVS Media. - 9783871555909 ; , s. 66-72
-
Konferensbidrag (refereegranskat)abstract
- Fundamental understanding of relationships between coating microstructure and thermal conductivity is important to be able to understand the influence of coating defects, such as delaminations and pores, on heat insulation in thermal barrier coatings. Object-Oriented Finite element analysis (OOF) has recently been shown as an effective tool for evaluating thermo-mechanical material behaviour, because of this method's capability to incorporate the inherent material microstructure as an input to the model. In this work, this method was combined with multi-variate statistical modelling. The statistical model was used for screening and tentative relationship building and the finite element model was thereafter used for verification of the statistical modelling results. Characterisation of the coatings included microstructure, porosity and crack content and thermal conductivity measurements. A range of coating architectures was investigated including High purity Yttria stabilised Zirconia, Dysprosia stabilised Zirconia and Dysprosia stabilised Zirconia with porosity former. Evaluation of the thermal conductivity was conducted using the Laser Flash Technique. The microstructures were examined both on as-sprayed samples as well as on heat treated samples. The feasibility of the combined two modelling approaches, including their capability to establish relationships between coating microstructure and thermal conductivity, is discussed.
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| 50. |
- Curry, Nicholas, 1984-, et al.
(författare)
-
Next generation thermal barrier coatings for the gas turbine industry
- 2011
-
Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 20:1-2, s. 108-115
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to develop the next generation of production ready air plasma sprayed thermal barrier coating with a low conductivity and long lifetime. A number of coating architectures were produced using commercially available plasma spray guns. Modifications were made to powder chemistry, including high purity powders, dysprosia stabilized zirconia powders, and powders containing porosity formers. Agglomerated & sintered and homogenized oven spheroidized powder morphologies were used to attain beneficial microstructures. Dual layer coatings were produced using the two powders. Laser flash technique was used to evaluate the thermal conductivity of the coating systems from room temperature to 1200 °C. Tests were performed on as-sprayed samples and samples were heat treated for 100 h at 1150 °C. Thermal conductivity results were correlated to the coating microstructure using image analysis of porosity and cracks. The results show the influence of beneficial porosity on reducing the thermal conductivity of the produced coatings. © 2010 ASM International.
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