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  • 151.
    Gåård, Anders
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Wear in sheet metal forming2008Licentiatavhandling, monografi (Annet vitenskapelig)
  • 152.
    Gåård, Anders
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Wear in sheet metal forming2008Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The general trend in the car body manufacturing industry is towards low-series production and reduction of press lubricants and car weight. The limited use of press lubricants, in combination with the introduction of high and ultra-high strength sheet materials, continuously increases the demands of the forming tools. To provide the means of forming new generations of sheet material, development of new tool materials with improved galling resistance is required, which may include tailored microstructures, introducing of specific(MC, M(C,N))carbides and nitrides, coatings and improved surface finish. In the present work, the wear mechanisms in real forming operations have been studied and emulated on a laboratory scale by developing a test equipment. The wear mechanisms identified in the real forming process, were distinguished into a sequence of events consisting of initial local adhesive wear of the sheets resulting in transfer of sheet material to the tool surfaces. Successive forming operations led to growth of the transfer layer and initiation of scratching of the sheets. Finally, scratching changed into severe adhesive wear, associated with gross macroscopic damage. The wear process was repeated in the laboratory test-equipment in sliding between several tool materials, ranging from cast iron to conventional ingot cast tool steels to advanced powder metallurgy tool steel, against dual-phase carbon steel sheets. By use of the test-equipment, selected tool materials were ranked regarding wear resistance in sliding against ferritic-martensitic steel sheets at different contact pressures.

    Wear in sheet metal forming is mainly determined by adhesion; initially between the tool and sheet surface interaction and subsequently, after initiation of material transfer, between a sheet to sheet contact. Atomic force microscopy force curves showed that adhesion is sensitive to both chemical composition and temperature. By alloying of iron with 18wt.% Cr and 8wt.% Ni, alloying in itself, or changes in crystal structure, led to an increase of 3 times in adhesion at room temperature. Hence, alloying may be assumed a promising way for control of adhesive properties. Additionally, frictional heating should be controlled to avoid high adhesion as, generally, adhesion was found to increase with increasing temperature for all investigated materials.

  • 153.
    Gåård, Anders
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Wear mechanisms in sheet metal forming: Effects of tool microstructure, adhesion and temperature2008Doktoravhandling, monografi (Annet vitenskapelig)
  • 154.
    Gåård, Anders
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Wear mechanisms in sheet metal forming: Effects of tool microstructure, adhesion and temperature2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The general trend in the car body manufacturing industry is towards low-series production and reduction of press lubricants and car weight. The limited use of lubricants, in combination with the introduction of high and ultrahigh-strength sheet materials, continuously increases the demands on the forming tools. The major cause for tool failure during the forming process is transfer and accumulation of sheet material on the tool surfaces, generally referred to as galling. The adhered material creates unstable frictional conditions and scratching of the tool/sheet interface. To provide the means of forming new generations of sheet materials, development of new tool materialswith improved galling resistance is required, which may include tailored microstructures introducing specific carbides and nitrides, coatings and improved surface finish. In the present work, the galling wear mechanisms in real forming operations have been studied and emulated at a laboratory scale by developing a test equipment. The wear mechanisms, identified in the real forming process, were distinguished into a sequence of events. At the initial stage, local adhesive wear of the sheets led to transfer of sheet material to the tool surfaces. Successive forming operations resulted in growth of the transfer layer with initiation of scratching of the sheets. Finally, scratching changed into severe adhesive wear, associated withgross macroscopic damage. The wear process was successfully repeated in the laboratory test equipment in sliding between several tool materials, ranging from cast iron and conventional ingot cast tool steels, to advanced powder metallurgy tool steel, sliding against medium and high-strength steel sheets. By use of the test equipment, selected tool materials were ranked regarding galling resistance. The controlling mechanism for galling in sheet metal forming is adhesion. The initial sheet material transfer was found to occur, preferably, to the metallic matrix of the tool steels. Hence, the carbides in the particular steels appeared less prone to adhesion as compared to the metallic matrix. Therefore, an improved galling resistance was observed for a tool steel comprising a high amount of small homogeneously distributed carbides offering a low-strength interface to the transferred sheet material.Further, atomic force microscopy showed that nanoscale adhesion was influenced by temperature, with increasing adhesion as temperature increases. A similar dependence was observed at the macroscale where increasing surface temperature led to initiation of severe adhesive wear. The results were in good agreement to the nano scale observations and temperature-induced high adhesion was suggested as a possible mechanism.

  • 155.
    Gåård, Anders
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Hallbäck, Nils
    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.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Temperature effects on adhesive wear in dry sliding contacts2010Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 268, nr 7-8, s. 968-975Artikkel i tidsskrift (Fagfellevurdert)
  • 156.
    Gåård, Anders
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Hirvonen Grytzelius, Joakim
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Zhang, Hanmin
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Experimental study of the relationship between temperature and adhesive forces for low-alloyed steel, stainless steel and titanium using atomic force microscopy in ultra-high vacuum2008Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, ISSN 0021-8979, Vol. 103, nr 12, artikkel-id 124301Artikkel i tidsskrift (Fagfellevurdert)
  • 157.
    Gåård, Anders
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. 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. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Influence of tool steel microstructure on origin of galling initiation and wear mechanisms under dry sliding against carbon steel sheets2009Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 267, nr 1-4, s. 387-393Artikkel i tidsskrift (Fagfellevurdert)
  • 158.
    Gåård, Anders
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. 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. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Microstructural characterization and wear behavior of (Fe,Ni)-TiC MMC prepared by DMLS2006Inngår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 421, nr 1-2, s. 166-171Artikkel i tidsskrift (Fagfellevurdert)
  • 159.
    Gåård, Anders
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. 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. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Wear mechanisms in deep drawing of carbon steel: correlation to laboratory testing2008Inngår i: Tribotest, ISSN 1354-4063, Vol. 14, nr 1, s. 1-9Artikkel i tidsskrift (Fagfellevurdert)
  • 160.
    Gåård, Anders
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. 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. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Wear mechanisms in galling: cold work tool materials sliding against high-strength carbon steel sheets2009Inngår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 33, nr 1, s. 45-53Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Transfer and accumulation of adhered sheet material, generally referred to as galling, is the major cause for tool failure in sheet metal forming. In this study, the galling resistances of several tool steels were evaluated against dual-phase high-strength carbon steel using a SOFS tribometer, in which disc-shaped tools were slid against a real sheet surface in dry sliding test conditions. Three different frictional regimes were identified and characterized during sliding, and any transition in friction corresponded to a transition in wear mechanisms of the sheets. The performance of the tools depended on load, material and the particular frictional regime. Best overall performance was obtained by nitrogen-alloyed powder metallurgy tool steel.

  • 161.
    Gåård, Anders
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. 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. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Hallbäck, Nils
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Galling resistance and wear mechanisms - cold work tool materials sliding against carbon steel sheets2007Inngår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 26, nr 1, s. 67-72Artikkel i tidsskrift (Fagfellevurdert)
  • 162.
    Gåård, Anders
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Sarih, Rahim M.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Influence of Tool Material and Surface Roughness on Galling Resistance in Sliding Against Austenitic Stainless Steel2012Inngår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 46, nr 2, s. 179-185Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Transfer and accumulation of adhered sheet material, generally referred to as galling, is a major cause for tool failure in sheet metal forming. In the present work, the galling resistance of three different tool materials was evaluated in lubricated sliding against austenitic stainless steel using a SOFS tribometer. All tool materials were prepared to four different surface roughnesses, ranging from a polished surface with R (a) = 0.05 mu m to a ground surface with R (a) = 0.3 mu m. The overall best performance was obtained for polished nitrogen alloyed powder metallurgy (PM) tool steel, where galling was detected only at the highest load evaluated, 700 N. However, for both the D2 type tool steel and nodular iron, best performance was observed for the surface possessing a surface roughness of 0.1 mu m. The improved galling resistance for the rougher surfaces was related to filling of grinding scratches with sheet material during the initial stage of sliding, prolonging the development of protruding sheet material on the tools surface. Similar trend was not observed for the PM steel, which was related to width of the scratches originating from the surface preparation, in relation to tool microstructure.

  • 163. Hallberg Hofstrand, Erik
    et al.
    Lestelius, Magnus
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik. Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Paper Surface Centre. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Rättö, Peter
    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.
    Odeberg Glasenapp, A.
    Evaluation of Pressure Variations Generated During Flexographic Post-Print of Corrugated Board and Effects of Mechanical Properties of Printing Forms on Printed Banding2004Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 164. Hallberg Hofstrand, Erik
    et al.
    Lestelius, Magnus
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik. Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Paper Surface Centre. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Rättö, Peter
    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.
    Odeberg Glasenapp, A
    Flexo Print of Corrugated Board: Mechanical Aspects of the Plate and Plate Mounting Materials2005Inngår i: TAGA Journal, vol.2,pp.16-28Artikkel i tidsskrift (Fagfellevurdert)
  • 165.
    Hallbäck, Nils
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Girlanda, Orlando
    Tryding, J
    Finite element Analysis of Ink-Tack Delamination of Paperboard2006Inngår i: International Journal of Solids and Structures, 43(5), 899–912 (2006)Artikkel i tidsskrift (Fagfellevurdert)
  • 166.
    Hallbäck, Nils
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Korin, Christer
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Barbier, Christophe
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper.
    Nygårds, Mikael
    KTH.
    Finite Element Analysis of Hot Melt Adhesive Joints in Carton Board2014Inngår i: Packaging technology & science, ISSN 0894-3214, E-ISSN 1099-1522, Vol. 27, nr 9, s. 701-712Artikkel i tidsskrift (Fagfellevurdert)
  • 167.
    Hanson, Magnus
    et al.
    Department of Materials Science, Uppsala University.
    Gåård, Anders
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Hogmark, Sture
    Department of Materials Science, Uppsala University.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. 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. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Comparison of two test methods for evaluation of forming tool materials2008Inngår i: Tribotest, ISSN 1354-4063, Vol. 14, nr 2, s. 147-158Artikkel i tidsskrift (Fagfellevurdert)
  • 168.
    Henriksson, Lisa
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Frodeson, Stefan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Berghel, Jonas
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Andersson, Simon
    Emerging Cooking Solutions Sweden AB.
    Ohlson, Mattias
    Emerging Cooking Solutions Sweden AB.
    Bioresources for Sustainable Pellet Production in Zambia: Twelve Biomasses Pelletized at Different Moisture Content2019Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, nr 2, s. 2550-2575Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The use of charcoal and firewood for cooking is common in Zambia,and its utilization is suchthat the deforestation rate is high, energy utilization is low, and unfavorable cooking methods lead to high death rates due to indoor air pollution mainly from particulate matter and carbon monoxide.Byusing an alternative cooking method, such as pellet stoves, it is possible to offer a sustainable solution, provided that sustainable pelletproduction can be achieved. In this study, 12different available biomaterials were pelletizedina single pellet unitto investigate their availability as raw materials for pellet production in Zambia. The study showedthat sicklebush and pigeon pea generatedthe same pelleting properties correlated withcompression and frictionand that both materials showedlow moisture uptake. The study also identifiedtwo groups of materials that broadenedthe raw material base and helpedto achieve sustainable pellet production.Group 1consisted of materials with equal pelletingabilities (miombo, peanut shell, pigeon pea,and sicklebush) andGroup 2 consistedof materialsthat showed low impact of varying moisture content(eucalyptus, miombo, peanut shell, pigeon pea, and sicklebush). The hardest pellet was made from Tephrosia, which wasfollowed by Gliricidia.

  • 169.
    Hidén Rudander, Petter
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Case hardened steel plates for ballistic armour: A study of ballistic and mechanical properties of case hardened ARMOX® steel2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Protective materials are a necessity to ensure the safety of personnel or property subjected to impacts by bullets, fragments and/or explosions. To shatter an inbound projectile, the surface of the target needs to exhibit a very high hardness but also the ability to prevent crack growth and plastically deform to avoid brittle fracture. The need for a combination of hardness and toughness led to the invention of dual hard steel which can be achieved within a homogeneous plate by modification of the surface through single-sided case hardening. In this work ARMOX® 440T and ARMOX® 500T was case hardened with a case depth of 2 and 2.3 mm and shoot upon with armour piercing rounds P80 to determine the ballistic limit of the material and to compare with the reference ARMOX®. Metallographic investigation was performed together with grain size measurement and mechanical properties were tested including hardness, impact toughness, dimensional deviation and tensile strength.

    A considerable increase of the ballistic performance with 40-70 % was reached by single-sided case hardening even though an irregular failure of the diffusion barrier had led to double-sided cases in various areas. Mass efficiency also increased considerably. Especially ARMOX® 440T was suitable for the treatment since it increased by the largest relative amount despite the fact that it had a thinner case then ARMOX® 500T plates.

    The complete penetrations were caused by formation of adiabatic shear bands and lead to punching of the plates except for hits at areas with double-sided case where back spall also occurred. The backside-case also resulted in a sharp reduction in impact toughness. Crack formation in close proximity to the impact site was found in all case hardened plates perpendicular to the front surface originating from inter-granular oxides near the surface.

    All the conventionally case hardened plates deviated from the reference plate flatness. Most likely because of placement in the furnace.

    Collectively the material is not recommended to be implemented in structural components until further investigations have been made concerning multi-hit threat, heat treat optimisation to minimize dimensional changes and bending because of the formation of perpendicular cracks under tensile load.

  • 170. Hjertsén, D
    et al.
    Sjöström, Johnny
    Bergström, Jens
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Näsström, M
    Finite element simulation of tool steel stress response as used in hot forging2004Konferansepaper (Fagfellevurdert)
  • 171.
    Hubbe, Martin A.
    et al.
    North Carolina State Univ, Dept Forest Biomat,.
    Alen, Raimo
    University Jyvaskyla, Finland.
    Paleologou, Michael
    FPInnovations, Canada.
    Kannangara, Miyuru
    Natl Res Council Canada.
    Kihlman, Jonas
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Lignin Recovery from Spent Alkaline Pulping Liquors Using Acidification, Membrane Separation, and Related Processing Steps: A Review2019Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, nr 1, s. 2300-2351Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The separation of lignin from the black liquor generated during alkaline pulping is reviewed in this article with an emphasis on chemistry. Based on published accounts, the precipitation of lignin from spent pulping liquor by addition of acids can be understood based on dissociation equilibria of weak acid groups, which affects the solubility behavior of lignin-related chemical species. Solubility issues also govern lignin separation technologies based on ultrafiltration membranes; reduction in membrane permeability is often affected by conditions leading to decreased solubility of lignin decomposition products and the presence of colloidal matter. Advances in understanding of such phenomena have potential to enable higher-value uses of black liquor components, including biorefinery options, alternative ways to recover the chemicals used to cook pulp, and debottlenecking of kraft recovery processes.

  • 172.
    Hämäläinen, Pyry
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    Hallbäck, Nils
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Gåård, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Lestelius, Magnus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper (from 2013).
    On the determination of transverse shear properties of paper using the short span compression test2017Inngår i: Mechanics of materials (Print), ISSN 0167-6636, E-ISSN 1872-7743, Vol. 107, s. 22-30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present paper explores the short span compression tester (SCT) as a means to experimentally determine the transverse shear moduli of paper. These moduli, which are known to be difficult to determine by any other means, are of importance for the behavior of paper during tissue manufacturing and in the converting and embossing of paperboard. Testing was conducted on paper of two different grammages both in MD and in CD. By applying the Timoshenko-Engesser theory for buckling of shear compliant materials, estimates of the transverse shear moduli were obtained through the measured SCT values and standard measurements of the Young's modulus and the thickness. These estimates were evaluated by detailed FE-analyses of the SCT setup incorporating initial geometrical imperfections representative for real test conditions. It was found that the Timoshenko-Engesser theory gives estimates of the transverse shear moduli that are within an accuracy well applicable for most engineering purposes. The results suggest that the method is at least as accurate as any other, more involved, method that could be used for the purpose.

  • 173.
    Hörling, Daniel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Parameter identification of GISSMO damage model for DOCOL 1200M: A study on crash simulation for high strength steel sheet components2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In the automotive industry there is a conflict between the need for weight reduction in order to reduce the CO2 emissions and the need for high safety. It has led to the use of high strength steel instead of the traditional lightweight materials. The increased use of high strength steels in combination with that the shortened development time in the automotive industry has led to the need of improved predictions of the actual crash behavior well since a full scale crash test is both expensive and time consuming.The damage model GISSMO is used in such crashworthiness simulations. In the present thesis the high strength steel grade DOCOL 1200M, GISSMO damage model has a number of parameters and curves that defines when necking and failure occurs, those have to be found. GISSMO is a phenomenological damage mechanics model which is based on experiments and does not consider voids and cracks thus it is only reliable to similar load cases as analyzed in the experiments. The different load cases are represented by the triaxiality which is the ratio between the mean stress and the von Mises stress.To find the parameters a number of test specimens were manufactured and tested in uniaxial tension then a FEM model was designed and the force displacement curve achieved from the simulation was mapped to match the experimentally achieved curve. The parameters were changed by the software LS-OPT® in order to increase the match. A metamodel-based optimization was run to find the curves and parameters with feedforward neural-networks and space filling point selection.The result shows that GISSMO has the potential to predict the failure behavior well, when the different specimens are optimized individually the match is good for all cases and when the simulation is examined the necking and localization of deformation is clearly seen. When the specimens are optimized together the match is not as good as the individual match.In order to improve the results more precise force displacement curves from the experiments would be of interest, for example load cells and optical measurments/strain gages could have been used to get the local displacement and the local stress and stress state. To make the model more reliable pure shear tests and compression tests could be used in future work. Running the optimizations for more iterations may also improve the result.

  • 174.
    Irshad, Muhammad Aatif
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    The effect of prior austenite grain size on the machinability of a pre-hardened mold steel.: Measurement of average grain size using experimental methods and empirical models.2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The use of pre-hardened mold steels has increased appreciably over the years; more than 80% of the plastic mold steels are used in pre-hardened condition. These steels are delivered to the customer in finished state i.e. there is no need of any post treatment. With hardness around ~40HRC, they have properties such as good polishability, good weldability, corrosion resistance and thermal conductivity. Machinability is a very important parameter in pre-hardened mold steels as it has a direct impact on the cost of the mold. In normal machining operations involving intricate or near net shapes, machining constitutes around 60% of the total mold cost.

    Efforts are underway to explore every possible way to reduce costs associated with machining and to make production more economical. All the possible parameters which are considered to affect the machinability are being investigated by the researchers. This thesis work focuses on the effect of prior austenite grain size on the machinability of pre-hardened mold steel (Uddeholm Nimax).

     Austenitizing temperatures and holding times were varied to obtain varying grain sized microstructures in different samples of the same material. As it was difficult to delineate prior-austenite grain boundaries, experimental and empirical methods were employed to obtain reference values. These different grain sized samples were thereafter subjected to machining tests, using two sets of cutting parameters. Maximum flank wear depth=0.2mm was defined for one series of test which were more akin to rough machining, and machining length of 43200mm or maximum wear depth=0.2mm were defined for second series of tests which were similar to finishing machining.

    The results were obtained after careful quantative and qualitative analysis of cutting tools. The results obtained for Uddeholm Nimax seemed to indicate that larger grain sized material was easier to machine. However, factors such as retained austenite content and work hardening on machined surface, which lead to degradation of machining operations were also taken into consideration. Uddeholm Nimax showed better machinability in large grained samples as retained austenite(less than 2%) content was minimal in the large grained sample. Small grained sample in Uddeholm Nimax had a higher retained austenite (7+2%) which resulted in degradation of machining operation and a lesser cutting tool life.

  • 175.
    Jackman, Henrik
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Svensson, Krister
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Bending modulus of freestanding carbon nanotubes2010Konferansepaper (Annet vitenskapelig)
  • 176.
    Jackman, Henrik
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Svensson, Krister
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Measurements of the critical strain for rippling in carbon nanotubes2011Inngår i: Applied Physics Letters, ISSN 0003-6951, Vol. 98, nr 18, s. 3 pages-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report measurements of the bending stiffness in free standing carbon nanotubes, using atomic force microscopy inside a scanning electron microscope. Two regimes with different bending stiffness were observed, indicative of a rippling deformation at high curvatures. The observed critical strains for rippling were in the order of a few percent and comparable to previous modeling predictions. We have also found indications that the presence of defects can give a higher critical strain value and a concomitant reduction in Youngs modulus.

  • 177.
    Jacobsson, Lasse
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Wickberg, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    De Vin, Leo
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Creating Industrially Relevant Environments for Teaching Lean Manufacturing at Karlstad University2016Inngår i: Advances in Manufacturing Technology XXX / [ed] Y.M. Goh and K. Case, IOS Press, 2016, Vol. 3, s. 514-519Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Simulation for training lean manufacturing ranges from simple paperbasedor LEGO®-based games to larger scale simulation environments, forinstance push car assembly. Whilst such simulations may be suitable for educatingstudents, they are often less suitable for training industry workers. The latter groupis more diverse and is more used to intuitive learning than to formal instruction.Thus, it is important that the training environment for this group more realisticallyrepresents the work environment; otherwise training transfer will be limited. Forthis reason, a lean training environment that includes materials processing stationsas well as assembly areas was created. The stations exhibit some realisticbehaviour such as stochastic breakdowns.

  • 178. Jansson, A
    et al.
    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.
    Influence of thickness on the mechanical properties for starch films2004Inngår i: Carbohydrate Polymers, 56, 499-503, (2004)Artikkel i tidsskrift (Fagfellevurdert)
  • 179.
    Jansson, Adam
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Master thesis within light warhead for support weapon: Investigation of defects, methods and requirement specifications in order to get a shell body shatter free2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    At launching the shell body, especially the backplane of the shell body, will be exposed to very high stresses due to acceleration, pressure and increased temperature from the propellant combustion. Defects in the shell body could in worst case for example result in high temperature gas leakage into the warhead and thereby ignite the explosives before exiting the launcher. This kind of explosion results in serious damages and can seriously injure both the gunner and other people in the surroundings.

    According to earlier study, carbon fibre reinforced epoxy with filament winding manufacturing method was the primary focus. The purpose of this master thesis was to investigate requirements and testing methods on a shell body manufactured in composite that will guarantee the safety of the gunner and surroundings in the launch phase.

    The pre-study conducted in this project showed that matrix cracks and fibre breakages are most common defects in the shell body that occur during launching affected by burst pressure. Matrix crack is the less dangerous defect among the impact damage types. Discussion with composite manufacturing companies showed that fibre breakage is a very serious type of defect since more breakage of fibres leads to the shell body have reduced stresses and cannot built-up the fully potential burst pressure during launching.

     

    Two requirement specifications were carried out, one for the shell body and another for the detection methods. These were created by own research and ideas according to found information, telephone- and e-mail contact with experts in areas and with personnel at Saab Dynamics AB.

    Some requirements for the shell body were that it should be fully usable after drop tests from different heights, vibration and transportation tests yield no cyclic damage after a long transport. Furthermore, the shell body should always use a fully isolated driving band to not have hot explosive gases penetrated into critical sections which results in detonation already in the launcher barrel. The most important requirements for the detection methods were to have depth analysis, high reliability and in-field inspection.

     

    Elimination- and decision matrices were made to find which detection methods should be the final selections in order to find the defects in a shell body. The detection methods which did not fulfil the criteria from each separate matrix were eliminated and did not proceed further as a concept. Eliminations were performed in concept generation phase (elimination matrix) and concept selection phase (decision matrix). In final selection phase a couple of methods were chosen that together found as many defects as possible.

     

    By using both acoustic emission and shearography all the critical defects and a wide range of other defects can be detected with very high reliability and resolution at an acceptable cost. These two methods “interact” perfectly with each other. Acoustic emission is the best method to find fibre breakage and matrix cracks, which are the most commonly occurring defects during launching. But shearography does not have a good detectability of fibre breakage and matrix cracks. On the other hand, shearography has good detectability of both planar- and volumetric defects.

    It is concluded that only two inspection methods, i.e. acoustic emission and shearography are needed to detect all of the possible defects in the grenade shell body. This is more economical solution requiring smaller space and fewer operators compared to one separate NDT method for detecting each type of defect.

  • 180. Jansson, Agneta
    et al.
    Järnström, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Paper Surface Centre. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Rättö, Peter
    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.
    Physical and Swelling Properties of Spray-Dried Powders made from Starch and Poly(vinyl alcohol)2006Inngår i: Starch/Stärke, 58 (12), 632-641,(2006)Artikkel i tidsskrift (Fagfellevurdert)
  • 181. Jansson, Agneta
    et al.
    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.
    Influence of thickness on the mechanical properties for starch films2004Inngår i: Carbohydrate Polymers, 56, 2004, pp 499-503Artikkel i tidsskrift (Fagfellevurdert)
  • 182. Jansson, Agneta
    et al.
    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.
    Mechanical properties of starch - a biodegradable polymer2002Konferansepaper (Fagfellevurdert)
  • 183. Jansson, Andreas
    Influence of alloying content and preconditioning on gaseous ferritic nitrocarburizing of steels2011Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Atlas Copco rock drills AB is manufacturing and developing rock drills. These rock drills have steel components that have high requirements. To increase mechanical properties (besides material selection) the components undergoes the in-house technology surface treatment nitrocarburizing. However some material can experience a variation in result after this surface treatment. This study is performed to increase the knowledge on which parameters in the manufacturing process that are influencing on the result of this surface treatment. Several steels were studied including steel grades comparable with the low alloy steels, 50CrMo4C, 42CrMo4, 25CrMo4 and C45E but also three high alloy Cr-Mo-V tool steels with various carbon content. These steels were exposed to different external elements such as air (surface oxidation), cutting fluid and alkaline cleaning fluids to gain knowledge about how chemical composition respond to external elements regarding nitrocarburizing results. The specimens were evaluated with light optical microscopy (LOM), scanning electron microscopy (SEM) and hardness testing. The results of this study demonstrate that steels have similar behaviour as reported in literature in aspect of chemical composition; increased amount of alloying content give a harder but also thinner hardened case. External elements like cutting fluid and delay time in air (surface oxidation) decrease thickness and homogeneity of hardened case in almost all material. An alkaline cleaning process after exposure of these external elements (air, cutting fluid) would, inconsistent, decrease thickness and homogeneity even further. Adding a second step of cleaning the surface with i.e. ethanol after alkaline cleaning process could reduce the negative effect from alkaline wash. Therefore, it is recommended that the wash process at Atlas Copco will be altered to improve the result of this surface treatment by a decrement of passivation media in cleaning process.

  • 184. Jernkvist, L O
    et al.
    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.
    Determination of cylindrical elastic orthotropy in wood by use of digital speckle photography2000Konferansepaper (Fagfellevurdert)
  • 185. Jernkvist, L O
    et al.
    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.
    Experimental determination of stiffness variation across growth rings in Picea Abies2001Inngår i: Holzforschung 55 2001 pp 309-317Artikkel i tidsskrift (Fagfellevurdert)
  • 186.
    Jireskog, Elin
    Karlstads universitet.
    Påverkan av spädvätskans pH och renhet på sulfatmassans blekbarhet: Laborativa försök och fabriksförsök för att minska kemikalieförbrukningen2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 187.
    Johansson, Caisa
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Going through the barrier2012Inngår i: Food Science & Technology, ISSN 1475-3324, Vol. 26, nr 3, s. 32-34Artikkel, forskningsoversikt (Annet vitenskapelig)
  • 188.
    Johansson, Caisa
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Bras, Julien
    France.
    Mondragon, Inaki
    Spain.
    Nechita, Petronela
    Romania.
    Plackett, David
    Danmark.
    Simon, Peter
    Slovakia.
    Gregor Svetec, Diana
    Slovenia.
    Virtanen, Sanna
    Finland.
    Giacinti Baschetti, Marco
    Italy.
    Breen, Chris
    UK.
    Clegg, Fransic
    UK.
    Aucejo, Susana
    Spain.
    Renewable fibers and bio-based materials for packaging applications-a reveiw of recent developments2012Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, nr 2, s. 2506-2552Artikkel, forskningsoversikt (Fagfellevurdert)
  • 189.
    Johansson, Daniel
    et al.
    MSE Weibull AB.
    De Vin, Leo
    Högskolan i Skövde.
    A Low Cost Video See-Through Head Mounted Display for Increased Situation Awareness in an Augmented Environment2008Inngår i: Proceedings of 5th INTUITION International Conference: Virtual Reality in Industry and Society: From Research to Application, 2008, Turin, Italy: INTUITION , 2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A head mounted display is developed for use in an immersive augmented reality simulator for virtual training. The simulator requires a video see-through parallax-free display to accurately mix the real and virtual worlds. High field of view is also required to allow use of peripheral vision in order to create a higher sense of awareness for the user. Due to high cost associated with commercial off-the-shelf display systems, a custom solution is designed and developed by combining hardware and software. It is shown that it is possible to build a low cost display system that provides the necessary attributes and acceptable compromises for the current type of application.

  • 190.
    Johansson, Hans
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. 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.
    Strip steel shapes as a result of non uniform plastic strain distributions. Part 22002Rapport (Annet vitenskapelig)
  • 191.
    Johansson, Hans
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap. 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.
    Tillstånd i bandstål av betydelse för bandets form2002Rapport (Annet vitenskapelig)
  • 192. Johansson, K
    et al.
    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.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Single fibre fragmentation, SFF, as evaluation of fibre strength in brown stock washing and oxygen delignification2000Konferansepaper (Fagfellevurdert)
  • 193. Johansson, K
    et al.
    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.
    Germgård, Ulf
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Single fibre fragmentation, SFF, as evaluation of fibre strength in brown stock washing and oxygen delignification2001Inngår i: Appita Journal, Vol. vol 54 no 3Artikkel i tidsskrift (Fagfellevurdert)
  • 194.
    Jonhed, Anna
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap.
    Properties of modified starches and their use in the surface treatment of paper2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The papermaking industry uses a large amount of starch each year, both as a wet-end additive and as a rheological modifier in surface sizing and coating colors. It is important to be able to reduce the amount of chemicals used in the papermaking and surface treatment process, to reduce costs and to make the process even more efficient. Interest in new high-performance starches is great. By using these new types of starches, improved recycling of barrier products may be obtained as well as a reduction in the use of synthetic sizing agents. The objectives of this work were to understand the behavior of temperature-responsive hydrophobically modified starches, where the solubility in water simply can be adjusted by temperature or by polymer charge, to improve the barrier properties, like the water vapor permeability, mechanical properties and water resistance (Cobb and contact angle) of papers surface sized by starch-containing solutions, and to investigate the potential for industrial use of these temperature-responsive starches. It was demonstrated that the temperature-responsive starches phase separate upon cooling and, depending on the charge density of the starch, a particulate precipitation or a gel-like structure was obtained. The starch with zero net charge showed a larger increase in turbidity than the starch with a cationic net charge, indicating that particulate precipitation is favored by a zero net charge and that the formation of a gel network is favored by charged starch molecules. Further, the starches formed inclusion complexes with surfactants, giving stabilization to the starches in the presence of surfactants. The net charge density of the starch and the charge of the surfactant determined whether or not an inclusion complex would form between them. Important mechanisms for the stability of the starch seemed to be formation of mixed micellar-like structures between the hydrophobic chain of the starch and the surfactant along the starch backbone in addition to formation of inclusion complexes between the starch and the surfactant. The hydrophobically modified starches showed higher hydrophobic surface character when applied to the paper surface above the critical phase separation temperature than with application at room temperature. Free films of the temperature-responsive starches showed good barrier against oxygen, but no barrier against water vapor. The mechanical properties decreased with addition of glycerol to the films.

  • 195.
    Jonsson, Jonathan
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    Different coatings effect on tool-life when milling hardened tool steels2015Independent thesis Basic level (degree of Bachelor), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    Abstract

    This thesis work is about finding out which coating should be used for which hardened tool steel and this was done by testing different coated cutting tools in different kinds of tool steels. The thesis work is performed at Uddeholms AB together with Uddeholms AB in the department of R&D at machinability cooperating with eifeler-Vacotec GmbH. The thesis work is going on from the end of January to the start of June and is a part of the education as mechanical engineer at Karlstad University and includes a total of 22,5 hp. The objective after finished thesis work is to be able to leave a recommendation to Uddeholms AB which coating is most suitable for each tool steel. To be able to leave that recommendation cutting tests are performed in four different hardened steel grades from Uddeholms AB combined with seven different coatings from eifeler-Vacotec GmbH. Steel grades tested are NIMAX®, DIEVAR®, VANADIS® 10 and ORVAR® SUPREME and coatings tested are CROSAL®, EXXTRAL® and SISTRAL® in different compounds. ORVAR® SUPREME gave such a long cutting tool-life that it was left for further investigation due to time limits that the thesis work had. In the other three tool steels it was possible to get a recommendation out of the four coatings tested in each tool steel. The coating that is recommended for each tool steel is only based on the cutting tool lasting the longest in each tool steel. That is not how a recommendation usually is formed, however for this thesis work there is no time for checking all the aspects that is vital for a proper recommendation. In order to get a proper recommendation, further more aspects that are checked are for example:

    • Different cutting parameters (cutting speed, feed, etc.)
    • Different geometries on the cutting tool
    • Smoothness of the cutting tool and the coating

    In table 1 there is a compilation of which coating that was recommended for which tool steel.

    Table 1. This is a compilation of which coating that was recommended for which tool steel.

    NIMAX®               CROSAL® V1

    DIEVAR®             SISTRAL® Ultrafine

    VANADIS® 10    SISTRAL® S

  • 196.
    Jonsson, Niklas
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013).
    Analys och utredning av värmebeständiga keramer för användning i hybriddrivlinor för fasta bränslen2015Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    Abstract [sv]

    Uppdragsgivaren Precer Group erbjuder tekniska lösningar för produktion av el genom ren förbränning av olika typer av fasta bränslen. Tekniken är anpassningsbar för att användas som återladdningskälla i olika typer av hybridfordon samt för produktion av el till bostäder och fritidshus.

    Arbetet har som syfte att presentera keramiska material till två olika zoner i Precers generation 2 drivlina där metallbränslen förbränns i en temperatur på 1800 °C. I Zon1 ska keramen klara en maximal temperatur på 2300°C och ha isolationsegenskaper. Till Zon2 önskas förmågan att motstå vidhäftning av heta partiklar och materialet ska kunna appliceras som ytbeläggning på befintligt rostfritt stål. Maximal temperatur i denna zon är 1100°C.

    Av de material som presenteras i arbetet är fullt stabiliserad Zirkoniumoxid (ZrO2) det enda materialet som klarar temperaturskravet i Zon1. ZrO2 har en låg värmeledningsförmåga på 2W/m*°C vilket resulterar i en god isolationsförmåga.

    Stora delar av arbetet är riktat till Zon2 där tester påvisar att keramiska material har en bättre förmåga att motstå vidhäftning av heta metallpartiklar än det befintliga rostfria stålet. De tre ytbeläggningar som testades var aluminiumoxid, zirkoniumoxid, och aluminia. Väljs istället att använda solida keramiska material ökar utbudet och material så som kiselkarbid( SiC), aluminiumtitanat(Al2TiO2), och kiselnitrid (Si3N4) är också tänkbara. Ett slutgiltigt materialval ansågs vara svårbedömt då konstruktionsunderlag saknades.

  • 197.
    Järnström, Lars
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Paper Surface Centre. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Johansson, Caisa
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörs- och kemivetenskaper, Paper Surface Centre.
    Johnson, Johanna
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Ultraviolet-induced aging of flexographic printing plates studied by thermal and structural analysis methods2009Inngår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 112, nr 3, s. 1636-1646Artikkel i tidsskrift (Fagfellevurdert)
  • 198.
    Karlsson, Hanna
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för kemiteknik.
    Strength Properties of Paper produced from Softwood Kraft Pulp: Pulp Mixture, Reinforcement and Sheet Stratification2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    For paper producers, an understanding of the development of strength properties in the paper is of uttermost importance. Strong papers are important operators both in the traditional paper industry as well as in new fields of application, such as fibre-based packaging, furniture and light-weight building material. In the work reported in this thesis, three approaches to increasing paper strength were addressed: mixing different pulps, multilayering and reinforcement with man-made fibres. In specific:

    The effects of mixing Swedish softwood kraft pulp with southern pine or with abaca (Musa Textilis) were investigated. Handsheets of a softwood kraft pulp with the addition of abaca fibres were made in a conventional sheet former. It was seen that the addition of abaca fibres increased the tearing resistance, fracture toughness, folding endurance and air permeance. Tensile strength, tensile stiffness and tensile energy absorption, however, decreased somewhat. Still it was possible to add up to about 60% abaca without any great loss in tensile strength. As an example, with the addition of 30% abaca, the tear index was increased by 36%, while the tensile index was decreased by 8%.

    To study the effect of stratification, a handsheet former for the production of stratified sheets, the LB Multilayer Handsheet Former was evaluated. The advantage of this sheet former is that it forms a stratified sheet at low consistency giving a good ply bond. It was shown to produce sheets with good formation and the uniformity, evaluated as the variation of paper properties, is retained at a fairly constant level when the number of layers in the stratified sheets is increased. The uniformity of the sheets produced in the LB Multilayer Handsheet Former is generally at the same level as of those produced in conventional sheet formers.

    The effects of placing southern pine and abaca in separate layers, rather than mixing them homogeneously with softwood pulp were studied. Homogeneous and stratified sheets composed of softwood and southern pine or softwood and abaca were produced in the LB Multilayer Handsheet Former. It was found that by stratifying a sheet, so that a pulp with a high tear index and a pulp with a high tensile index are placed in separate layers, it was possible to increase the tear index by approximately 25%, while the tensile index was decreased by 10-20%. Further, by mixing a pulp with less conformable fibres and no fines with a pulp with more flexible fibres and fines, a synergy in tensile strength (greater strength than that predicted by linear mass fraction additivity) was obtained.

    The effects of stratifying sheets composed of softwood and abaca were compared to the effects of refining the softwood pulp. Homogeneous and stratified sheets composed of softwood with three different dewatering resistances and abaca were also produced in the LB Multilayer Handsheet Former. It was found that by stratifying the sheets the tear index was retained while the tensile index was increased by the refining.

    The effects of reinforcing softwood pulp of different dewatering resistances with man-made fibres with low bonding ability were also investigated. Man-made fibres (i.e. regenerated cellulose, polyester and glass fibres) were added in the amounts 1, 3, or 5 wt% to softwood pulp of three different dewatering resistances. It was found that with refining of a softwood pulp and subsequent addition of long fibres with low bonding ability the tensile-tear relationship can be shifted towards higher strength values. The bonding ability of the man-made fibres was evaluated by pull-out tests and the results indicated that, in relation to the fibre strength, regenerated cellulose (lyocell) was most firmly attached to the softwood network while the glass fibres were most loosely attached.

  • 199.
    Karlsson, Johan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013).
    Composite material in car hood: Investigation of possible sandwich materials2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 200.
    Karlsson, Patrik
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för maskin- och materialteknik.
    The early stage of galling2012Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In sheet metal forming (SMF) of materials such as stainless steels there is a major problem with transfer and accumulation of sheet material to the metal forming tool surface. The problem is known as galling; a kind of severe adhesive wear, which results in severe scratching of produced parts. In this thesis, galling observed in contacts between tool steels and stainless steel sheets under lubricated sliding conditions was studied, focusing on the early stage of galling. It was found that changes in friction cannot be used as galling indicator in the early stage of galling because transfer and accumulation of sheet material happens even though friction is low and stable. The progression of galling is influenced by tool steel damage occurring around the tool steel hard phases caused by sheet material flow, which results in formation of wear-induced galling initiation sites. A correlation between the critical contact pressure to galling and sheet material proof stress was found. Galling happened at lower pressures for sheet material with lower proof stress possibly due to easier sheet material flow, resulting in quicker tool damage. Material transfer and tool steel damage were delayed for tool steels comprising homogenously distributed, small and high hard phases. Additionally, the galling resistance was higher for tool steels with higher hardness due to decreased tool steel damage. In a comparison between observations of the worn tool surfaces after wear tests and calculations in FEM it was found that material transfer did not take place at regions with highest contact pressures but at regions with highest plastic strains. The results obtained in this thesis indicate that tool steel damage and sheet material flow occurring in the contact during sliding are important factors influencing galling.

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