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  • 401.
    Vilardell, Anna M.
    et al.
    Univ Barcelona, CPT, Dept Ciencia Mat & Engn Met, Marti & Franques 1, E-08028 Barcelona, Spain..
    Cinca, N.
    Univ Barcelona, CPT, Dept Ciencia Mat & Engn Met, Marti & Franques 1, E-08028 Barcelona, Spain..
    Cano, I. G.
    Univ Barcelona, CPT, Dept Ciencia Mat & Engn Met, Marti & Franques 1, E-08028 Barcelona, Spain..
    Concustell, A.
    Univ Barcelona, CPT, Dept Ciencia Mat & Engn Met, Marti & Franques 1, E-08028 Barcelona, Spain..
    Dosta, S.
    Univ Barcelona, CPT, Dept Ciencia Mat & Engn Met, Marti & Franques 1, E-08028 Barcelona, Spain..
    Guilemany, J. M.
    Univ Barcelona, CPT, Dept Ciencia Mat & Engn Met, Marti & Franques 1, E-08028 Barcelona, Spain..
    Estrade, S.
    Univ Barcelona, Dept Elect, LENS MIND IN2UB, C Marti & Franques 1, E-08028 Barcelona, Spain..
    Ruiz-Caridad, A.
    Univ Barcelona, Dept Elect, LENS MIND IN2UB, C Marti & Franques 1, E-08028 Barcelona, Spain..
    Peiro, F.
    Univ Barcelona, Dept Elect, LENS MIND IN2UB, C Marti & Franques 1, E-08028 Barcelona, Spain..
    Dense nanostructured calcium phosphate coating on titanium by cold spray2017Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 37, nr 4, s. 1747-1755Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article deals with the understanding of building-up mechanisms of bioactive nanocrystalline hydroxyapatite coatings by Cold Spray, revealing very promising results in contrast to more conventional techniques such as Plasma Spray. A full characterization of feedstock and coatings is provided. The agglomerated structure of the powder proved to be suitable to obtain successfully thick hydroxyapatite coatings. A crystallite size below similar to 20 nm in the powder and the as-sprayed coatings is calculated by the Rietveld X-ray refinement method and agreed by Transmission Electron Microscopy. Some wipe tests were carried out on Ti6Al4V substrates in order to study the deposition of single particles and the nanoscale features were evaluated. The resulting structure indicates that there is no delimitation of particle boundaries and the overall coating has been formed by effective compaction of the original nanocrystallites, leading to consistent and consolidated layers. (C) 2016 Elsevier Ltd. All rights reserved.

  • 402.
    Vilardell, Anna M.
    et al.
    Univ Barcelona, Thermal Spray Ctr, Barcelona, Spain.
    Cinca, N.
    Univ Barcelona, Thermal Spray Ctr, Barcelona, Spain..
    Concustell, A.
    Univ Barcelona, Thermal Spray Ctr, Barcelona, Spain..
    Dosta, S.
    Univ Barcelona, Thermal Spray Ctr, Barcelona, Spain.
    Cano, I. G.
    Univ Barcelona, Thermal Spray Ctr, Barcelona, Spain.
    Guilemany, J. M.
    Univ Barcelona, Thermal Spray Ctr, Barcelona, Spain.
    Cold spray as an emerging technology for biocompatible and antibacterial coatings: State of art2015Inngår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 50, nr 13, s. 4441-4462Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    The use of coatings in biomaterials has been fundamental on the applicability of many medical devices and has helped improve mechanical properties such as wear and fatigue and biological properties such as biocompatibility and bioactivity of implant prosthesis, thus, in essence, ameliorating human quality life. The aim of the present paper is to give a review on cold spray (CS) coating systems that are emerging in orthopedics industry (internal fixation systems and prosthesis) as well as those for antibacterial purposes (in body and touch external surfaces). These studies are very new, the oldest dating from the half of last decade and most deal with the improvement of biocompatibility and bioactivity of hard tissue replacement; therefore, research on biocoatings is in constant development with the aim to produce implant surfaces that provide a balance between cell adhesion and low cytotoxicity, mechanical properties, and functionalization. CS offers many advantages over conventional high-temperature processes and seems to be able to become competitive in front of the low-temperature techniques. It is mainly cost effective, appropriate for oxygen-sensitive materials, and environmentally green. It basically involves the use of feedstock material in powder form, which is supersonically sprayed onto the appropriate substrate but without any melting as it occurs in conventional thermal spray processes. Biocompatible metallic materials and polymers have been successfully deposited by this method because it is based on the plasticity of the coating material; pure ceramic deposits, for example of hydroxyapatite, are still a challenge.

  • 403.
    Vilardell, Anna M.
    et al.
    Universitat de Barcelona, Spain.
    Cinca, N.
    Universitat de Barcelona, Spain.
    Jokinen, A.
    BioNavis Ltd., Finland.
    Garcia-Giralt, N.
    URFOA, IMIM, Spain.
    Dosta, S.
    Universitat de Barcelona, Spain.
    Cano, I. G.
    Universitat de Barcelona, Spain.
    Guilemany, J. M.
    Universitat de Barcelona, Spain.
    Real-Time Protein and Cell Binding Measurements on Hydroxyapatite Coatings2016Inngår i: Journal of Functional Biomaterials, ISSN 2079-4983, E-ISSN 2079-4983, Vol. 7, nr 3, artikkel-id 23Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although a lot of in vitro and in vivo assays have been performed during the last few decades years for hydroxyapatite bioactive coatings, there is a lack of exploitation of real-time in vitro interaction measurements. In the present work, real-time interactions for a plasma sprayed hydroxyapatite coating were measured by a Multi-Parametric Surface Plasmon Resonance (MP-SPR), and the results were compared with standard traditional cell viability in vitro assays. MP-SPR is proven to be suitable not only for measurement of molecule–molecule interactions but also molecule–material interaction measurements and cell interaction. Although SPR is extensively utilized in interaction studies, recent research of protein or cell adsorption on hydroxyapatite coatings for prostheses applications was not found. The as-sprayed hydroxyapatite coating resulted in 62.4% of crystalline phase and an average thickness of 24 ± 6 ÎŒm. The MP-SPR was used to measure lysozyme protein and human mesenchymal stem cells interaction to the hydroxyapatite coating. A comparison between the standard gold sensor and Hydroxyapatite (HA)-plasma coated sensor denoted a clearly favourable cell attachment on HA coated sensor as a significantly higher signal of cell binding was detected. Moreover, traditional cell viability and proliferation tests showed increased activity with culture time indicating that cells were proliferating on HA coating. Cells show homogeneous distribution and proliferation along the HA surface between one and seven days with no significant mortality. Cells were flattened and spread on rough surfaces from the first day, with increasing cytoplasmatic extensions during the culture time.

  • 404.
    Viskari, Leif
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Cr(VI)-free surface treatment of fluid connectors2007Independent thesis Advanced level (degree of Master (One Year)), 15 poäng / 22,5 hpOppgave
  • 405.
    W. Lindvall, Fredrik
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Adhesive wear testing and modelling of tool steels sliding against sheet metals2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Sheet metal forming is a manufacturing method used because of its versatility. Sheets are plastically deformed by a tool to create a product. A tool is expected to last for several 100,000 forming operations and efforts are made to optimize the tools. A common type of wear referred to as galling is the adhesion of sheet material to the tools. This problem has become more prevalent as new high strength sheet materials have been developed at the same time as lubricants have become heavily regulated. This has forced the development of new tool steels with improved resistance to galling. There are many parameters influencing the response to galling. In this work the influence of surface preparation, contact geometry, material selection and lubrication has been investigated. The surface of the forming tools has a large influence on the tools effective life. To refurbish a forming tool is expensive and often requires special shops and hand polishing. The influence on galling of different surface preparations suited for sheet metal forming was investigated using a strip-reduction equipment. The contact conditions of a tool sliding against metal sheets were investigated using FE models. The contact conditions were calculated for a U-bending test and for a sliding-on-flat-surface wear tester. The results were compared to those found in literature. One model incorporated the surface roughness of a sheet as measured by optical profilometry. The strength of the interface between the tool and the sheet material determine if material can be transferred onto the tool. The interface between the tool and adhered sheet material was closely studied using transmission electron microscopy of thin lamellas produced by focused ion beam milling. This showed sheet material adhering to the tool without the formation of an interlayer. Finally, several different combinations of tool steels and sheet materials were tested with regards to their ability to withstand galling.

  • 406.
    W. Lindvall, Fredrik
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    On tool steel, surface preparation, contact geometry and wear in sheet metal forming2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In sheet metal forming operations the life length of the production equipment islargely dependent on the wear of the tools that are in direct contact with the sheet.One form of adhesive wear where some sheet material gets transferred to the tool, alsoknown as galling, is the most common cause of tool failure. The transferred materialsticks firmly to the tool and will scratch subsequent sheets and increase friction, renderingthem anywhere from aesthetically unsightly to completely ripped apart. Withcareful combination of several parameters the tools production life can be significantlyextended. The surface preparation of the tools has a large influence on the tool life, thesurface has to be smooth and yet not without texture. It was shown in strip reductiontesting that the orientation as well as the depth of the surface texture left by polishinginfluenced the tool life and that a texture perpendicular to the sliding direction was toprefer. The geometry of the forming tool is also a parameter to take into account as itinfluences the tool life not only by changing the contact pressure but also in itself. Ina sliding against flat sheet test rig a lower contact pressure increased the sliding distanceto galling. When two different geometries were compared at the same contactpressure it was found that there was a difference in tool life. As to the tool itself thematerial it’s made of influences the wear rate and tool life. Different tool steels wasinvestigated in sliding wear against metal sheets; Vancron 40 performed better thanVanadis 6 and S290PM performed better than a AISI M2 grade steel.

  • 407.
    W. Lindvall, Fredrik
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Assessment of galling performance of tools steel andsheets metals used in formingManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    A number of tool steel and sheet metal combinations were tested with respect to gallingbehaviour. Tests were performed both in dry and lubricated sliding. The tested sheet gradeswere three carbon steels, Docol 1200 M, Docol 1000 DP and DC01 two stainless steels,EN 1.4301 and EN 1.4509 one aluminium grade, AA 1193 and one titanium grade ti6al4vor EN 3.7164. The tool steels were two high speed steels and three powder metallurgicaltool steel grades.It was found that the tool steels performed equally well on dry sheets and the gradescould not be adequately separated. Under lubricated sliding on the Docol 1200 M sheetsthe difference between two PM materials was however notable.The addition of lubrication increased the tool life significantly for all materials excepttitanium. Titanium showed signs of galling immediately even if the sheets were lubricated.

  • 408.
    W. Lindvall, Fredrik
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Hogmark, Sture
    Uppsala Universitet.
    Study of the interface between adhered sheet metaland tool steel subjected to adhesive wearManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Many products used every day have at least some parts manufactured by sheet metal forming.Sheet metal forming is well suited for mass production and many machines perform aforming step in a matter of seconds. A common and severe form of wear is called gallingand occurs as small amounts of the sheet material is transferred on to the tool.In the present study the interface between three different sheet materials and a powdermetallurgical tool steel was investigated based on morphology and chemical composition.The sheets used were a high strength carbon steel sheet CS, a stainless steel grade, SS andtitanium, Ti. The tool steel, Vancron 40, was selected based on previously shown resistanceto galling. The microstructure of the tool steel contains three major constituents, the steelmatrix, M6C carbides and MCN carbonitrides, each constituent with potentially differentadhesive properties.To investigate the interfaces between the tool and the adhered material cross sectionlamellas was cut using a focused ion beam and studied in a transmission electron microscope.The chemical compositions of the interfaces were also investigated using electronenergy-loss spectroscopyThe presence of an interlayer between the tool and the adhered material would be ofhigh interest as the adhesion in the interface governs galling. The study did not reveal anyinterlayer between tool constituents and adhered material, for Vancron 40 worn against CSand SS but for one combination. SS sheet showed a ≃ 10 nm morphological interlayeragainst a MCN carbonitride. The lubricant was removed from the contact area and no traceof it was left in the interface between tool and adhered sheet. This shows that adhesive wearoccurs during direct tool to sheet contact comparative to dry sliding in SOFS tests.

  • 409.
    W. Lindvall, Fredrik
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Ekengren, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    FE calculations of contact conditions of a doublecurved disc pressed and slid against a metal sheetManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Many products are manufactured using sheet metal forming, as it has a high productionrate and a low cost when producing large series. However wear of sheet metal formingtools in the form of galling can severely limit the production. The sliding-on-flat-surfacewear tester, SOFS, has been used to reproduce the wear process leading up to galling in alaboratory environment.The contact conditions of the SOFS wear tester were investigated by several differentFE models. The contact conditions during static loading were accurately and preciselypredicted for the contact geometry found in the Sliding on flat surface wear tester. Thepressures were validated against the analytical Hertzian solution. During sliding the contactgeometry was shown to change predictably into a semi elliptical shape. At high friction, = 0.6, the contact pressure distribution changed to be heavier in the front and to the sides,leaving a slightly lower pressure in the center of the contact.An attempt was also made to model a sheet with surface roughness as measures byan optical profilometer. The attempt was successful in that a working FE model could becreated but there still remains work before the model con be used to accurately predict thecontact conditions. The model showed the formation of potential lubrication pockets on a

  • 410. Wahlstrom, T
    et al.
    Rakic, V
    Karlsson, H
    Thuvander, Fredrik
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Paper Surface Centre. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Predicting tensile properties of multilayer paperboards from properties of the layers2008Annet (Annet (populærvitenskap, debatt, mm))
  • 411.
    Wallin, Harald
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    An investigation of friction graphs ranking ability regarding the galling phenomenon in dry SOFS contact: (Adhesive material transfere and friction)2008Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The main purpose of this project is to investigate different tool steels in terms of their ability to withstand material transfer buildup, so-called galling, occurring in SMF (sheet metal forming) operations. The ability to withstand galling is vital to optimize cost-effectiveness and increase the work tool’s effective operational time. This investigation studies four different tool steels, including a TiN-coating, with the intention of evaluating the microstructures, chemical composition and hardness effect on galling resistance in dry conditions using a slider-on-flatsurface (SOFS) tribo-tester which measures the coefficient of friction during sliding.

    An OP (optical profilometer) was used to measure the size and geometry of lump growth on the tool and damage on the work sheet. A scanning electron microscope (SEM) was used to identify the interacting tribological mechanisms exhibited at different stages during the slide. The SEM figures confirmed three different types of characteristic patterns exhibited in the tracks after tribo- testing which were categorized as mild adhesive, abrasive and severe adhesive damage.

    A SEM figure that illustrates a ragged contact surface and an obvious change in the sheet materials plastic behavior is in this report regarded as a sign of severe adhesive contact, the characteristics could possibly be explained by local high temperature and high pressure followed by a sudden pressure drop and creation of hardened welds or solders between the two surfaces which increase the frictional input needed for further advancement. Friction coefficients observed in the initial 100% mild adhesive stage were, μ=0,22-0,26 succeeded by abrasive SEM characteristics often in association with mild adhesive contact and friction values between μ=0,25-0,4 which where sometimes followed by severe adhesive SEM characteristics in 100% of the contact zone with friction values between μ=0,34- 0,9 respectively. The tool material that performed best according to the friction detection criteria was Sv21 closely followed by Sleipner (TiN coated) and Va40 (HRC 63.3). Unfortunately was the friction criteria, a significant raise in friction for defining a sliding length to galling, not adequate for dry conditions due to immediate material transfer succeeded by cyclic changes between partial or 100% abrasive+mild adhesive and severe adhesive contact. The mechanism that change abrasive wear in association with mild adhesive contact, (moderate friction input), to sever adhesive wear, (higher friction input), is dependent on lump shape (lump geometry) and can appear at comparably low speeds 0,04-0,08 [m/s] and low friction energy input (μ=0,34), the magnitude of the change in friction is therefore not always significant and hardly detectable on the friction graph. This was quite unexpected but could be explained by concentration of friction energy rater than the absolute amount. The problem with using friction graphs for galling evaluation was increased even further when a very small lump size and low corresponding rate of material transfer to the tool surface caused a sustainable high raise in friction (μ≈0,3→0,6) on a TiN-coated tool steel called Sleipner.

    A hardly detectable or similar friction raise for Sv21 and Va40 showed much larger corresponding lump size and rate of material transfer. This means that friction graphs demonstrate a clear problem with quantifying lump size [m3] and rate of  material transfer [m3/s]. Another phenomenon called stick slip behavior, material transfer and lump growth followed by a sudden decrease in lump size and transfer of material back to the work sheet, is also not possible to detect on a friction graph. Because a drop in friction can easily be a change in contact temperature and lump attack angle due to a growing lump and not a decreasing lump.

     

    The conclusion, a friction graph is not suited for galling evaluation and ranking in dry SOFS conditions. A ranking should primarily be based on dimensional OP measurements of the cross section of formed tracks and scratches or preferably by repeated OP measurements of the tool surface during a single test, the last revel the exact lump growth history and true lump growth even in the sliding direction.

     

  • 412.
    Wang, Yu
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Mechanical properties and microstructure of laser sintered and starch consolidated iron-based powders2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In powder metallurgy research field, Direct Metal Laser Sintering (DMLS) and Metal Powder Starch Consolidation (MPSC) are relatively new rapid forming techniques to fabricate complex and near net-shaped components. The working principles of DMLS are to melt and fuse metal powder layer by layer in computer controlled systems to pile up components like three dimensional printing. It has been for instance extensively used for mould inserts, die parts, and functional metal prototypes. Another, less explored method, starch consolidation is a pressureless direct casting method which consists principally of mixing powder slurry, casting into moulds, consolidation, drying, and sintering. With a strong focus on both methods, the study here combines several strong material technology sectors; powder, rapid forming, mechanical property testing and surface technology. It covers the processing chain from green body preparation, optimization of

    sintering, nitriding, post sinter heat treatment, to modeling and assessment of material behaviour for end-user applications. An iron based powder and a high vanadium high speed steel powder with low and high carbon contents were used in the DMLS and MPSC processes, respectively. The overall aim of the study is to synthesize near net-shaped powder-based components, to characterize pores and microstructure, and to establish a fundamental understanding of failure mechanisms of powder based materials in bending fatigue, thermal fatigue and wear.

    The study showed the DMLS and MPSC technologies could produce shaped components with a multi-phased structure, controllable nitriding depth and high relative densities in a range of 97 - 99.7 %. Materials' heterogeneity and porosity have detrimental influence on mechanical properties, especially on crack initiation and subsequent propagation.

  • 413. Wang, Yu
    et al.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Characterization and fatigue behaviour of a starch consolidated and sintered high speed steel2006Konferansepaper (Fagfellevurdert)
  • 414. Wang, Yu
    et al.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Fatigue and microstructure of iron based sintered alloys2007Inngår i: Journal of Iron and Steel research, 2007, 14Artikkel i tidsskrift (Fagfellevurdert)
  • 415. Wang, Yu
    et al.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Room temperature and thermal fatigue behaviour f an iron-based laser sintered metal2006Konferansepaper (Fagfellevurdert)
  • 416.
    Wang, Yu
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Borgström, Henrik
    Department of Materials Science and Engineering, Chalmers University of Technology.
    Characterization and bending fatigue behaviour of a starch consolidated high speed steel: as-sintered, sintered and tempered, and sintered and nitridedManuskript (Annet vitenskapelig)
  • 417.
    Wang, Yu
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Burman, Christer
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Thermal fatigue behavior of an iron-based laser sintered material2009Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 513-514, nr 15 july, s. 64-71Artikkel i tidsskrift (Fagfellevurdert)
  • 418.
    Wang, Yu
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Burman, Christer
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Thermal fatigue behaviour of an iron-based laser sintered material2009Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 513-514, s. 67-71Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Direct metal laser sintering is a rapid manufacturing technique to make intricate and near net-shaped parts. An iron-based laser sintered metal was studied to evaluate its thermal fatigue properties. The test was performed using cylindrical specimens in a high power induction heating system equipped with a laser strain gauge for a contactless surface strain measurement. Initiation of thermal fatigue cracks occurred preferentially at pores and layer interfaces, while propagation of cracks followed along phase boundaries and thin inter-dendritic phases and showed an inter-granular fracture. By using the fundamental Fourier equation for heat conduction, the temperature cycle was modeled and calculated. A thermo elastic ideal plastic model was used to deduce the thermal stress based on surface strain experimentally measured. Finally, the temperature distribution, thermal stresses and mechanical strains were discussed with respect to thermal fatigue damage.

  • 419.
    Wang, Yu
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Gerth, Julia
    Uppsala University.
    Hogmark, Sture
    Uppsala University.
    Borgström, Henrik
    Chalmers University of Technology.
    Harlin, Peter
    Dalarna University.
    Microstructure, strentgth and wear of high speed steel in HIPed, HIPed + nitrided, and SC+nitrided conditionsManuskript (Annet vitenskapelig)
  • 420.
    Wickholm, Kristina
    et al.
    RISE - Research Institutes of Sweden, Bioekonomi.
    Williams, Helén
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Lindström, Annika
    Innventia.
    Lorentzon, Ann
    Innventia.
    Wikström, Fredrik
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Innovative packaging for reduction of food waste from producer to consumer2016Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Increasing population and environmental changes poses a significant pressure on the global food supply chain. With the large quantities of food waste that’s been reported over the past couple of years packaging can play a more significant role in reducing the food wastage. Together with actors along the entire value chain we are developing new innovative packaging solutions to reduce food waste throughout the value chain, from food producers to consumers. The purpose of the study is to design and optimize new packaging system solutions so that no part of the chain is optimized at the expense of any other part. In the fall of 2015 the food wastage was examined in three supply chains, salsa in glass jar (A), rice pudding in plastic packaging (B) and lettuce in plastic packaging (C), by using waste audits in the businesses, collecting, comparing and analyzing data. For consumer insights ethnographic studies was used in ten Swedish households. Interviews have also been conducted with consumers in retail stores. The supply chain study indicates little wastage for A and B and higher for C. Consumer report some handling difficulties with the food packaging and reasons why food is wasted. The main reasons being that the food gets bad, difficulties to empty the packaging and that the amount of food is higher than their needs. A majority of the consumer state that they often view packaging as something unnecessary. Consumers do not give packaging functions many thoughts in general and many have difficulties in judging the packaging functions.

  • 421.
    Wik, Greger
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Headbox Slice Opening Arrangement: An Alternative Solution for Tissue Machines2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The head box in a tissue machine distributes the fiber suspension to a flat jet along the width of the machine. By adjusting the so-called lip opening, the flow is regulated and the jet is accelerated to match the machine speed. In this work, ideas for alternative solutions for lip opening mechanism is generated and evaluated with a focus on making a cost saving. One of the concepts has been selected for a deeper analysis with respect to the design, strength and cost. The selected concept is based on reducing the number of jacks required by using one jack operating a shaft parallel to the apron beam. Levers convey the movement to the apron beam. The analysis show that the shaft is exposed to high torque which results in large elastic twisting of the shaft, which means that the force that supports the apron beam will not be equal over the entire width. If the difference in force is too big, the apron beam will twist which results in an uneven lip opening. The shaft stiffness is therefore crucial. For the head box with a width of 2946 mm, the number of jacks is reduced from three to one. Wider head boxes may need more than one jack since the shaft cannot be made to long without getting too much twisted. A lip opening mechanism of the current design with six 20 ton jacks can be compared to the new concept in which only two jacks is needed and the cost is reduced by 18%. There is further potential for savings if the jack, separate gear and electric motor are replaced with an actuator that has the motor mounted directly.

  • 422.
    Wikstrand, Björn
    Karlstads universitet, Institutionen för ingenjörsvetenskap, fysik och matematik.
    Investigation of nickel phospor coat: -As corrosion protection inside water heaters2009Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis explores the possibility of alternatives to copper lining inside the water heater

    tank in water heaters. The need for an alternative is based on the increasing copper prices the

    recent years. The aim of this thesis is to compare three different materials, stainless steel,

    copper and a nickel coated plain carbon steel. This comparison is based on a basic corrosion

    test and a literature survey to render a merit value for each environment/metal interface. The

    testing solution consists of 100ppm Cl

    - concentration the specimens are tested in three

    different pH levels and at three different temperatures. The specimens have their weight

    measured before and after the test.

    The 15μm thick nickel coating was performed by Ferroprodukter AB, composing of 9% P

    and 91% Ni. The copper and stainless steel specimens are both from Thermia’s actual water

    heater tank. The copper lining is made of pure copper and the stainless steel hull is made of

    ferritic stainless steel.

    The results from the corrosion test are measured in weight change by modulus, |Δw|/w, for

    the comparison of the three materials. It was found that stainless steel was the worst

    material, performing better at higher temperatures and higher pH , but overall performance is

    far from copper and nickel’s corrosion properties. The nickel coating and copper specimen

    showed comparable results and perform more or less equally well. Regarding identification

    of corrosion mechanics, it may consist of either pitting and general corrosion damage or a

    mixture of both. To avoid the fact that weight change may be both negative and positive, the

    solution to this was to incorporate a merit value based on the absolute value of the weight

    change, divided by the initial weight of the specimen.

    In conclusion, stainless steel total weight change by modulus accumulates to 16.072g, nickel

    coated specimen accumulates a weight change by modulus equal to 8.544g, important note:

    two of the nickel coated specimen account for ~72.4% of the total weight change by modulus

    which then accumulates to 2.36g. Copper’s total weight change by modulus was 2.937g thus

    the lowest. However, disregarding from the 90캜 regime; stainless steel scores 13.496g,

    copper 2.151g, and nickel 1.095g.

  • 423.
    Wikström, Fredrik
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Williams, Helén
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Packaging and Food Waste Behavior2017Inngår i: Reference Module in Food Sciences, Elsevier, 2017, s. 1-4Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Packaging saves food by protecting the content from physical and chemical degradation during the distribution and storage processes. However, packaging can do much more than that. This article explores how the design of a package may help, or indeed hinder, the consumer to avoid wasting food. A number of packaging attributes influence consumer behavior. The influence is different depending on the product‘s characteristics and the needs of the consumer. For many products, it might be better to add packaging material, for example, by creating smaller sizes of the product to reduce food waste and the overall environmental impact.

  • 424.
    Wikström, Fredrik
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Williams, Helén
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Trischler, Jakob
    Karlstads universitet, Fakulteten för humaniora och samhällsvetenskap (from 2013), Centrum för tjänsteforskning (from 2013).
    Rowe, Zane
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    The importance of packaging functions for food waste of different products in households2019Inngår i: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 11, nr 9, s. 1-16, artikkel-id 2641Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The United Nations sustainability goal SDG 12.3 is to reduce the amount of food that is wasted by half, due to environmental and social reasons. This paper aims to analyse the most important packaging functions that affect food waste in households for different products, as the reason for wastage can be expected to differ between different products. The reasons for food wastage of different categories and products have been compiled through literature studies, and possible improvements of packaging functions to reduce food waste have been identified. In addition, an expert workshop judged the most important packaging functions to reduce food waste for a number of products. They also discussed the obstacles and possibilities to realise the packaging improvements. This study confirms that how packaging functions influence food waste on the product level is a highly unexplored question. Most likely, there is high potential to reduce food waste through better adaptions of packaging functions to user needs and habits. Both the literature study and the expert workshop show that less food per pack and better information regarding food safety and storage have high potential to reduce food waste, but also that product specific considerations are necessary.

  • 425.
    Wilke, Caroline
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Fördröja åldrandet av elektrotekniskt papper genom kemikalietillsats: En studie av dicyandiamids påverkan2011Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Nordic Paper Åmotfors tillverkar elektrotekniskt papper som används till att isolera lindningarna i transformatorer. Det är viktigt att bibehålla papprets egenskaper under en mycket lång tid då en transformators livlängd är lång. Syftet med detta examensarbete var att undersöka huruvida tillsats av en kemikalie bestående av dicyandiamid kan fördröja åldrandet av de papper som Nordic Paper tillverkar. Förhoppningen var att deras papper därefter skulle klara de krav-parametrar som finns för papper som åldrats i olja. Kemikalien som användes var Cartafix® WE liquid.

    Försök utfördes där olika kemikaliedoseringar tillsattes i mälden. Pappersark tillverkades och kvävehalten mättes därefter för att verifiera att kemikalien fastnat i de färdiga papprena. Pappers-arken åldrades sedan endera i olja eller i luft, och den kvarvarande polymerisationsgraden (DP) mättes. Sprängstyrke- och konduktivitetstester utfördes också. Papper som Nordic Paper tillverkat beströks med olika kemikaliedoseringar och samma tester utfördes även på dessa.

    Resultaten visade att retentionen av kemikalien var låg. Kvävehalten blev inte högre än 1 % och detta skedde vid 10-20 % kemikalietillsats.

    Efter åldring i olja minskade DP relativt mycket, vilket medförde att papprena inte uppnådde de uppsatta kraven (maximalt 50 % minskning). Tillsats av kemikalien förbättrade dock papprets åldringsegenskaper med nästan 45 % om icke-modifierat papper jämförs med det modifierade pappret som hade högst DP (10 % kemikalietillsats, vilket motsvarade 1 % kvävehalt).

    Papper som modifierats med kemikalietillsats i mälden gav lägre DP då åldringen skett i luft jämfört med icke-modifierat papper. DP minskade avsevärt efter åldring för papper som bestrukits med kemikalien.

    Kemikalietillsats försämrade både sprängstyrkan och konduktivteten.

  • 426. Yadoitsev, Igor
    et al.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Yadroitsava, Ina
    Hierarchical design principles of selective laser melting for high quality metallic objects2015Inngår i: Additive manufacturing, ISSN 2214-8604, Vol. 7, s. 45-56Artikkel i tidsskrift (Fagfellevurdert)
  • 427. Yadroitsev, I
    et al.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Yadroitsava, I
    Selective laser melting of Ti6Al4V alloy for biomedical applications: Temperature monitoring and microstructural evolution2014Inngår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 583, s. 404-409Artikkel i tidsskrift (Fagfellevurdert)
  • 428.
    Yadroitsev, I.
    et al.
    Cent Univ Technol, Dept Mech & Mechatron Engn, ZA-9300 Bloemfontein, Free State, South Africa.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Yadroitsava, I.
    Cent Univ Technol, Dept Mech & Mechatron Engn, ZA-9300 Bloemfontein, Free State, South Africa.
    Du Plessis, A.
    Univ Stellenbosch, CT Scanner Facil, ZA-7602 Stellenbosch, South Africa.
    Qualification of Ti6Al4V ELI Alloy Produced by Laser Powder Bed Fusion for Biomedical Applications2018Inngår i: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 70, nr 3, s. 372-377Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rectangular Ti6Al4V extralow interstitials (ELI) samples were manufactured by laser powder bed fusion (LPBF) in vertical and horizontal orientations relative to the build platform and subjected to various heat treatments. Detailed analyses of porosity, microstructure, residual stress, tensile properties, fatigue, and fracture surfaces were performed based on x-ray micro-computed tomography, scanning electron microscopy, and x-ray diffraction methods. The types of fracture and the tensile fracture mechanisms of the LPBF Ti6Al4V ELI alloy were also studied. Detailed analysis of the microstructure and the corresponding mechanical properties were compared against standard specifications for conventional Ti6Al4V alloy for use in surgical implant applications. Conclusions regarding the mechanical properties and heat treatment of LPBF Ti6Al4V ELI for biomedical applications are made.

  • 429.
    Yadroitsev, I
    et al.
    Université de Lyon, France.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Yadroitsava, I
    Université de , France.
    Johansson, S
    Linköpings universitet.
    Smurov, I
    Université de Lyon.
    Energy input effect on morphology and microstructure of selective laser melting single track from metallic powder2013Inngår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 213, nr 4, s. 606-613Artikkel i tidsskrift (Fagfellevurdert)
  • 430.
    Yadroitsev, Igor
    et al.
    South Africa.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Yadroitsava, I.
    South Africa.
    A systematic approach to manufacturing parts with desired properties by selective laser melting2015Inngår i: Materials Science and Technology Conference and Exhibition 2015, MS and T 2015, Association for Iron and Steel Technology, AISTECH , 2015, Vol. 1, s. 121-128Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Selective laser melting (SLM) is becoming a powerful additive manufacturing technology for different industries: automotive, medical, chemical, aerospace, etc. The extension of applications requires a wide spectrum of powder materials with specific properties. To produce parts with tailored properties by SLM, optimal process-parameters and scanning strategies have to be used for different powders. Numerical simulation allows the estimation of temperature distribution during laser melting and prediction the final microstructures and properties of SLM object. A hierarchical approach, including systematic analysis of SLM parameters necessary to control the final product quality on every level - track, layer, 3D object is suggested and discussed. A series of single tracks, layers and 3D objects were manufactured from metal powders to validate a proposed algorithm. The efficiency of the approach was illustrated by the manufacturing of fully dense samples from AISI 420 stainless steel.

  • 431. Yadroitsev, Igov
    et al.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Yadroitsava, Inna
    Titanium Alloys Manufactured by In Situ Alloying During Laser Powder Bed Fusion2017Inngår i: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 69, nr 12, s. 2725-2730Artikkel i tidsskrift (Fagfellevurdert)
  • 432.
    Yadroitsev, Igov
    et al.
    Department of Mechanical and Mechatronic Engineering, Bloemfontein, Central University of Technology, Free State, South Africa.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Yadroitsava, Inna
    Department of Mechanical and Mechatronic Engineering, Bloemfontein, Central University of Technology, Free State, South Africa.
    Du Plessis, Anton
    University of Stellenbosch.
    Qualification of DMLS Ti6Al4V (ELI) alloy for biomedical applications2017Inngår i: Proceedings of the 28th Annual International Solid Freedom Fabrication symposium – an Additive Manufacturing conference 2017 / [ed] David L. Bourell, Richard H. Crawford, Carolyn C. Seepersad, Joseph J. Beaman & Scott Fish, Austin: University of Texas , 2017Konferansepaper (Fagfellevurdert)
  • 433.
    Yang, Zhenkun
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Alternatives to hard chromium plating on piston rods2011Independent thesis Advanced level (degree of Master (Two Years)), 30 poäng / 45 hpOppgave
  • 434.
    Yong-an, Min
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). Shanghai University, China.
    Bergström, Jens
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Xiao-chun, Wu
    Shanghai University, China.
    Luo-ping, Xu
    Shanghai University, China.
    Oxidation and Thermal Fatigue Behaviors of Two Type Hot Work Steels During Thermal Cycling2013Inngår i: Journal of Iron and Steel Research International, ISSN 1006-706X, E-ISSN 2210-3988, Vol. 20, nr 11, s. 90-97Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thermal fatigue test has been carried out on widely used hot work steel 4Cr5MoSiV1 and a low alloyed steel 3Cr3MoV in temperature range of 200 to 700 degrees C. Tempering resistance, as well as high temperature hardness/strength of steel specimens, works as a dominating material parameter on thermal fatigue resistance. During the heating period, high hardness can depress the inelastic deformation. This deformation is the origination of tensile stress, which acts as the driving force of heat checking during the cooling period. The cyclic strain-oxidation interaction can speed up the damage on surface defects, which plays an obvious role in initiation of thermal cracks. On 4Cr5MoSiV1 steel specimens, borders between the matrix and inclusions such as titanium compounds, or lager carbides such as primary carbides, are focused by strain and attacked by oxidation, and are main initiating places of cracks. While on 3Cr3MoV steel specimens, larger strain causes plastic deformation concentrating around grain boundaries. Then the following oxidation accelerates this grain boundary damage and creates cracks.

  • 435.
    Zemui, Simon
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013).
    Quenching and tempering hardness response of front axle steel beams: Different material properties during quenching and tempering2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The aim of this thesis was to investigate what the relation is between as-quench hardness and final surface hardness for steel beams is, depending on what tempering temperature is used. Also explain how chemistry, dimension and microstructure effects the final mechanical properties of the front axle beam. For this a review of literature concerning the effects was completed.Hardness measurement on the surface was performed on the ends of the beam (bottom and top). This hardness measurement was performed on 6 different front axle articles of the same material (41CrS4) and 2 different front axle articles of another material (40CrMo4). The relation diagram gives an estimation of what type of tempering temperature is needed to achieve the final hardness that is desired. Because the relation was done with some inconsistences it can’t be said to give a perfect answer. The relation diagrams only work for material 41CrS4 and 40CrMo4. For the core hardness test, 2 articles of 41CrS4 and one article of 40CrMo4 was measured on 5 different position on the cross-section, the beams for the respective articles were taken from quenched state and quenched+tempered. The beam dimensions have a significant effect when it comes to cooling down the part and achieve as close to uniform hardness as possible. Even though the Middle point of the I-section sample is one of the closest cores to the surface, it has a softer core compared with the other cores. While there exists hardness difference after quenching between different points in the core they even out after tempering. When comparing the core hardness with the surface hardness it can be said that the surface hardness is not as hard as the core because of decarburization. The microstructure analysis was done on 2 articles of 41CrS4 and one article of 40CrMo4. Samples from the 3 articles is taken from both the as-quenched state and quenched+tempered state. From the optical microscope it could be seen, that the surface of the beams decarbonizes leading to a higher amount of ferrite at the structure and softer surface. Because of this 15 mm into the material is harder than at-surface. Decarburization of the 41CrS4 steels made it so that what should have been a martensite and bainite dominated surface became a ferrite and bainite dominated.To decide the actual amount of retained austenite in the sample an XRD-analysis was performed. The XRD-analysis is done only for one article type of 41CrS4. From the front axle beam three samples of three different locations (bottom, middle, top) was taken for the analysis. For the theoretical calculation of the retained austenite vs the actual amount it can be said that is a very good representation of the total amount of retained austenite in the product. But the theoretical calculation deviates a bit from the actual amount at the top part of the beam.

  • 436.
    Åkefeldt, Jon
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Optimization of laser welding process: Hermetical weld between a medium carbon steel and a low carbon steel shim2017Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
  • 437.
    Åsberg, Mikael
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Fredriksson, Gunnel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Hatami, Sepehr
    Sverea IVF, Gotenburg.
    Fredriksson, Wendy
    Bodycote Hot Isostatic Pressing AB.
    Influence of HIP on microstructure, pore elimination and tensile properties of SLM manufactured H13 tool steel2017Konferansepaper (Annet vitenskapelig)
  • 438.
    Åsberg, Mikael
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Fredriksson, Gunnel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Hatami, Sepehr
    Swerea IVF AB.
    Fredriksson, Wendy
    Bodycote Hot Isostatic Pressing.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Influence of post treatment on microstructure, porosity and mechanical properties of additive manufactured H13 tool steel2019Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 742, s. 584-589Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Additive manufacturing (AM) is an attractive manufacturing technology in tooling applications. It provides unique opportunities to manufacture tools with complex shapes, containing inner channels for conformal cooling. In this investigation, H13, a widely used tool steel, was manufactured using a laser powder bed fusion method. Microstructure, tensile mechanical properties, hardness, and porosity of the AM H13 after stress relieve (SR), standard hardening and tempering (SR + HT), and hot isostatic pressing (SR + HIP + HT) were investigated. It was found that the microstructure of directly solidified colonies of prior austenite, which is typical for AM, disappeared after austenitizing at the hardening heat treatment. In specimens SR + HT and SR + HIP + HT, a microstructure similar to the conventional but finer was observed. Electron microscopy showed that SR and SR + HT specimens contained lack of fusion, and spherical gas porosity, which resulted in remarkable scatter in the observed elongation to break values. Application of HIP resulted in the highest strength values, higher than those observed for conventional H13 heat treated in the same way. The conclusion is that HIP promotes reduction of porosity and lack of fusion defects and can be efficiently used to improve the mechanical properties of AM H13 tool steel.

  • 439.
    Öhrn Sten, Niklas
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Design and development of a new invented doctor blade: Design och utveckling av nyuppfunnet kräppningsblad2014Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This report contains the development and construction of a new patented doctor blade. A doctor blade is used when creping soft paper from a large rotating Yankee cylinder. At the current state the doctor blade are in use for four to six hours before it needs to be switch due to wearing, stopping the production of soft paper. The new idea is to have a very long and small blade that will slide into a fixed blade and be continuously pulled when creping paper. The company CS Production had a concept of the fixed blade but wanted to further develop it since the blade was too wide.

     

    Measurements where done with the old blade and with the old testing device to measure the pull force required to pull the blade. New concepts where made by the method of brainstorming and evaluated with an elimination matrix. Rivet joints where selected as the joining technique for the new design. The new concept contains one dominant blade that smaller parts were assembled to form the final blade. The material selected for the dominant blade and the section blade was a cold rolled stainless spring steel strip and for the middle disc the material was aluminum bronze string casted. Test on the pull force required where done with the new doctor blade in the new test rig.  FEM simulation where done on a small part of the blade to see where stresses are occurring in the blade. The FEM result showed that no stresses where on the middle discs, rivets or section blades. This is not reliable results because the small doctor blade is pushing down onto the middle discs and stresses should be occurring on the discs.  Further testing is needed to see if the blade can withstand the forces applied to it.

  • 440.
    Östberg, Linda
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Some aspects on the activation of dissolving pulps and the influence on the reactivity in a following viscose stage2013Inngår i: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 47, nr 3-4, s. 165-169Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It was found that, for a dissolving pulp, an enzymatic pre-treatment with an endoglucanase prior to viscose preparation did not change the correlation between the gamma number of the viscose dope and the carbon disulphide charge. Thus, the pulp stoichiometry, or reactivity, was not changed by an endoglucanase pre-treatment. It has nevertheless previously been found that the pulp reactivity, measured either by Fock's test or as the filter clogging value (Kw), increased for the same type of enzyme pre-treatment. Thus, the pulp reactivity seems to be influenced by the analysis method employed.

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