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  • 151.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hajlane, Abdelghani
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Materials Science and Nano-engineering, Mohammed VI Polytechnic University, Benguerir, Morocco.
    Renbi, Abdelghani
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Ouarga, Ayoub
    Materials Science and Nano-engineering, Mohammed VI Polytechnic University, Benguerir, Morocco.
    Chouhan, Shailesh Singh
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Conductive Regenerated Cellulose Fibers by Electroless Plating2019Inngår i: Fibers, ISSN 2079-6439, Vol. 7, nr 5, artikkel-id 38Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Continuous metallized regenerated cellulose fibers for advanced applications (e.g. multi-functional composites) are produced by electroless copper plating. Copper is successfully deposited on the surface of cellulose fibers using commercial cyanide-free electroless copper plating package commonly available for manufacturing of printed wiring boards. The deposited copper is found to enhance the thermal stability, electrical conductivity and resistance to moisture uptake of the fibers. On the other hand, involved chemistry results in altering the molecular structure of the fibers as is indicated by the degradation of their mechanical performance (tensile strength and modulus).

    Fulltekst (pdf)
    fulltext
  • 152.
    Al-Mashikhi, S.O.
    et al.
    University of Notttingham.
    Powell, John
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Voisey, K.T.
    University of Notttingham.
    An explanation of ‘striation free' cutting of mild steel by fibre laser2009Inngår i: Lasers in manufacturing 2009: proceedings of the Fifth International WLT-Conference Lasers in Manufacturing, LIM 2009 : Munich, Germany, June 15th - 18th, 2009 / [ed] Andreas Ostendorf, Stuttgart: AT-Fachverlag , 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents the results of an experimental and theoretical investigation into the phenomenon of ‘striation free cutting', which is a feature of fibre laser cutting of thin section mild steel. The paper concludes that the creation of very low roughness edges is related to an optimisation of the cut front geometry when the cut front is inclined at angles close to the Brewster angle for the laser - material combination. For purely geometric reasons this particular type of cut front optimisation is not possible for CO2 laser cutting of mild steel.

    Fulltekst (pdf)
    FULLTEXT01
  • 153.
    Al-Mashikhi, S.O
    et al.
    Salalah College of Technology, Engineering Department, Salalah, Oman and Faculty of Engineering, University of Nottingham.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Voisey, K.T.
    Faculty of Engineering, University of Nottingham.
    Heat affected zones and oxidation marks in fiber laser–oxygen cutting of mild steel2011Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 23, nr 4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of cutting speed and sheet thickness on surface oxidation and heat affected zones (HAZs) has been investigated for laser–oxygen cutting of mild steel sheet with a fiber laser. Optical and scanning electron micrographs were used to determine the extent of surface oxidation and HAZ from plan and cross-sectional views, respectively. The HAZ is consistently wider at the bottom of the cut compared to the HAZ at the top of the cut. With increasing speed, the width of the HAZ at the top of the cut decreases whereas the HAZ width at the bottom of the cut generally increases. No simple, direct relationship between HAZ width and surface oxidation was seen. However, it is possible to state that in each case considered here, the HAZ would be completely removed if they are machined back by a depth equal to the extent of the surface oxidation.

  • 154.
    Almer, J.
    et al.
    Advanced Photon Source (APS), Argonne National Laboratory, Argonne.
    Lienert, U.
    Advanced Photon Source (APS), Argonne National Laboratory, Argonne.
    Peng, R.L.
    Linköping universitet.
    Schlauer, C.
    Linköping universitet.
    Odén, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Strain and texture analysis of coatings using high-energy x-rays2003Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 94, nr 1, s. 697-702Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate the internal strain and crystallographic orientation (texture) in physical-vapor deposited metal nitride coatings of TiN and CrN. A high-energy diffraction technique is presented that uses synchrotron x rays and an area detector, and which allows the strain and intensity distributions of multiple crystallographic planes to be measured by a single x-ray exposure. Unique texture states and nonlinear sin2 strain distributions are observed for all coatings investigated. Quantitative analysis indicates that existing micromechanical models can reasonably predict strain and corresponding stress for mixed-hkl reflections but are inadequate for fully describing measured data. Alternative mechanisms involving deposition-induced defects are proposed

  • 155.
    Almer, J
    et al.
    Advanced Photon Source (APS), Argonne National Laboratory, Argonne.
    Odén, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Håkansson, G
    Bodycote Värmebehandling AB.
    Microstructure and thermal stability of arc-evaporated Cr-C-N coatings2004Inngår i: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 84, nr 7, s. 611-630Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The role of C incorporation in the microstructure and thermal stability of arc-evaporated Cr-C-N coatings is explored via reactive growth in a mixed C2H4-N2 environment. C is found to react more readily than N at both the Cr cathode and the coating surfaces, so that a C2H4-to-N2 flow ratio of only 1% yields a C-to-N ratio of approximately 10% within the coatings. The as-deposited microstructures consist primarily of the δ-Cr(C, N) phase and possess high compressive residual stresses, which decrease with increasing C content. Post-deposition annealing up to 700°C results in depletion of lattice defects, and concomitant reductions in stress and coating hardness, together with phase transformations which suggest metastable phase formation during growth. Apparent activation energies for this lattice defect are found to be in the range expected for bulk diffusion of N and C (2.4-2.8 eV). The results suggest that inclusion of small amounts of C in this system offers the ability to reduce internal stresses while maintaining defect-related hardness increases, permitting growth of thicker and thus more wear-resistant coatings.

  • 156.
    Almgren, Karin M
    et al.
    STFI-Packforsk AB, Box 5604, SE-114 86 Stockholm.
    Gamstedt, Kristofer
    Department of Fiber and Polymer Technology, Royal Institute of Technology - KTH.
    Varna, Janis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Contribution of wood fiber hygroexpansion to moisture induced thickness swelling of composite plates2010Inngår i: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 31, nr 5, s. 762-771Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One of the main drawbacks of wood fiber-based composite materials is their propensity to swell due to moisture uptake. Because the wood fibers are usually the main contributor to hygroexpansion, it is of interest to quantify the hygroexpansion coefficient of wood fibers, to compare and rank different types of fibers. This investigation outlines an inverse method to estimate the transverse hygroexpansion coefficient of wood fibers based on measurements of moisture induced thickness swelling of composite plates. The model is based on composite micromechanics and laminate theory. Thickness swelling has been measured on polylactide matrix composites with either bleached reference fibers or crosslinked fibers. The crosslinking modification reduced the transverse hygroexpansion of the composites and the transverse coefficient of hygroexpansion of the fibers was reduced from 0.28 strain per relative humidity for reference fibers to 0.12 for cross-linked fibers.

  • 157.
    Al-Ramahi, Nawres
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Failure Impact Energy in Curved Composite Plates2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An investigation of low velocity impact characteristics of curved composite plates have been presented. The plates represent parts of car's bumpers with radii of curvature of 120mm,200mm, 300mm, 450mm and infinity.

    Two types of composite materials are used, unidirectional 0° and woven 0°/90° types with five layers of 3mm thickness and ten layers of 6mm thickness of each type.

    The results showed that larger plates curvatures can absorb more impact energy and the ten layer woven 0°/90° composite are superior to similar unidirectional 0° composite. On the other hand the five layer unidirectional 0° plates are superior in absorbing energy compared to similar woven 0°/90° plates.

    An investigation of the failure patterns and development for both types of composite has been presented and discussed.

    The effects of multi-strike on the energy absorbtion of both type of composite have showed different pattern of energy absorbtion behavior.

    Fulltekst (pdf)
    fulltext
  • 158.
    Al-Ramahi, Nawres
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Numerical stress analysis in hybrid adhesive joint with non-linear materials2018Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis presents systematic numerical study of stresses in the adhesive of a single-lap joint subjected to various loading scenarios (mechanical and thermal loading). The main objective of this work is to improve understanding of the main material and geometrical parameters determining performance of adhesive joint for the future analysis of failure initiation and development in these structures.

    The first part of the thesis deals with development of a 3D model as well as 2D model, optimized with respect to the computational efficiency by use of novel displacement coupling conditions able to correctly represent monoclinic materials (off-axis layers of composite laminates). The model takes into account the nonlinearity of materials (adherend and adhesive) with geometrical nonlinearity also accounted for. The parameters of geometry of the joint are normalized with respect to the dimensions of adhesive (e.g. thickness) thus making analysis of results more general and applicable to wide range of different joints. Optimal geometry of the single-lap joint is selected based on results of the parametric analysis by using peel and shear stress distributions in the adhesive layer as a criteria and it allows separation of edge and end effects. Three different types of single lap joint with similar and dissimilar (hybrid) materials are considered: a) metal-metal; b) composite-composite; c) composite-metal. In case of composite laminates, four lay-ups are evaluated: uni-directional ([08]T and [908]T) and quasi-isotropic laminates ([0/45/90/-45]S and [90/45/0/-45]S). The influence of the abovementioned parameters is carefully examined by analyzing peel and shear stress distributions in the adhesive layer. Discussion and conclusions with respect to the magnitude of the stress concentration at the ends of the joint overlap as well as overall level of stresses within overlap are presented. Recommendations concerning use of nonlinear material model are given.

    The rest of the work is related to the various methods of manufacturing of joint (curing) and application of thermo-mechanical loading suitable to these scenarios. The appropriate sequences of application of thermal and mechanical loads for the analysis of the residual thermal stresses developed due to manufacturing of joints at elevated temperature required to cure polymer (adhesive/composite) are proposed. It is shown that the most common approach used in many studies of simple superposition of thermal and mechanical stresses works well only for linear materials and produces wrong results if material is non-linear. The model and simulation technique presented in the current thesis rectifies this issue and accurate stress distributions are obtained. Based on the analysis of these stress distributions the following conclusions can be made: joint processing at elevated temperature causes high stresses inside the adhesive layer; the residual thermal stresses will reduce the peel stress concentration at the ends of overlap joint and the shear stress within the overlap, moreover, this effect is more pronounced for the case of the one-step joint manufacturing in comparison with two-step processing technique.

    This study has generated a lot of results for better understand of behavior of adhesive joints and it will help in design of stronger, more durable adhesive single-lap joints in the future.

    Fulltekst (pdf)
    fulltext
  • 159.
    Al-Ramahi, Nawres
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Institute of Technology, Middle Technical University, Baghdad.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Swerea SICOMP AB.
    Varna, Janis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    FEM analysis of stresses in adhesive single-lap joints with non-linear materials under thermo-mechanical loading2018Inngår i: ECCM18, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This study presents comprehensive numerical stress analysis in the adhesive layer of a single-lap joint subjected to various loading scenarios (mechanical and thermal loading). For this purpose numerical model (finite element method) with novel displacement coupling conditions able to correctly represent monoclinic materials (off-axis layers of composite laminates) has been developed. This model includes nonlinear material model and geometrical nonlinearity is also accounted for. The effect of thermal residual stresses (in adhesive) is analysed for various methods of manufacturing of single lap joint. The sequences of application of thermal and mechanical loads for the analysis of the thermal residual stresses in joints are proposed. It is shown that the most common approach used in many studies of linear superposition of thermal and mechanical stresses works well only for linear materials and produces wrong results if material is non-linear. The present study demonstrates suitable method to apply combined thermal and mechanical loads to get accurate stress distributions. Based on the analysis of these stress distributions the conclusions concerning the effect of the thermal residual stresses on peel and shear stress concentrations are made. The comparison between effect of thermal stresses in case of the one-step and two-step joint manufacturing techniques is made.

    Fulltekst (pdf)
    fulltext
  • 160.
    Al-Ramahi, Nawres
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Institute of Technology / Baghdad, Middle Technical University, Baghdad, Iraq.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Swerea SICOMP AB, Piteå, Sweden.
    Varna, Janis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Investigation of end and edge effects on results of numerical simulation of single lap adhesive joint with non-linear materials2018Inngår i: International Journal of Adhesion and Adhesives, ISSN 0143-7496, E-ISSN 1879-0127, Vol. 87, s. 191-204Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents systematic numerical study of stresses in the adhesive of a single-lap joint with the objective to improve understanding of the main material and geometrical parameters determining performance of adhesive joints. For this purpose a 3D model as well as 2D model, optimized with respect to the computational efficiency by use of novel displacement coupling conditions able to correctly represent monoclinic materials (off-axis layers of composite laminates), are employed. The model accounts for non-linearity of materials (adherend and adhesive) as well as geometrical non-linearity. The parameters of geometry of the joint are normalized with respect to the dimensions of adhesive (e.g. thickness) thus making analysis of results more general and applicable to wide range of different joints. Optimal geometry of the single-lap joint allowing to separate edge effect from end effects is selected based on results of the parametric analysis by using peel and shear stress distributions in the adhesive layer as a criterion. Three different types of single lap joint with similar and dissimilar (hybrid) materials are considered in this study: a) metal-metal; b) composite-composite; c) composite-metal. In case of composite laminates, four lay-ups are evaluated: uni-directional ([08]T and [908]T) and quasi-isotropic laminates ([0/45/90/-45]S and [90/45/0/-45]S). The influence of the abovementioned parameters on peel and shear stress distributions in the adhesive layer is examined carefully and mechanical parameters governing the stress concentrations in the joint have been identified, this dependence can be described by simple but accurate fitting function. The effect of the used material model (linear vs non-linear) on results is also demonstrated.

  • 161.
    Al-Ramahi, Nawres
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Varna, Janis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Model for numerical simulation and parametric analysis of composite adhesive joints under thermo-mechanical loading2017Inngår i: ICCS20: Proceedings : 20th International Conference on Composite Structures / [ed] Antonio J.M. Ferreira, W. Larbi, J.F. Deu, F. Tornabene, N. Fantuzzi, Paris: Società Editrice Esculapio, 2017 , 2017, , s. 662s. 234-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Abstract: The current investigation focuses on development and verification of a modelfor numerical simulation of performance of adhesive joints under tensile loading. Differentcombination of materials in joints is considered: metal-metal, composite-composite andcomposite-metal. The objective of this paper is to present simulation results of joints usingan accurate finite element model including non-linear behaviour and large deformation.Moreover, several loading scenarios are analysed, including simultaneous application oftemperature and mechanical load. Not only the effect of temperature on mechanicalperformance of materials (adhesive as well as adherents) is analysed but also built up ofresidual thermal stresses during the manufacturing of joints are taken into account. Thisapproach is demonstrated by simulation of tensile tests of joints at several temperatures.Two scenarios of application of temperature and mechanical load using large deformationtheory are considered: 1) the thermal and mechanical loads are applied simultaneously (theproperties of the materials are adjusted accordingly to their performance at differenttemperatures); 2) temperature is applied on specimen which is not macroscopicallyconstrained and the obtained stress distribution is used as initial state for the nextsimulation of mechanical loaded joint. The influence of edge effects (due to limited widthof the joint) on the stress distribution within the joint are studied. In order to eliminatethese effects the periodic boundary conditions (BC) are used in the numerical model.These BC are adjusted to optimize numerical model and obtain efficient calculation routinefor analysis of stresses within interior part of the structure. The validity of these BCs isevaluated and verified by analysing number of case studies. The comparison between full3D FEM model and simplified 2D model is carried out. The resulting stress distributions inthe overlap region of joints are presented for different joints (the parameters are: materialcombinations, material models, geometry of adhesive layer, constraints and BCs) withcomprehensive analysis and recommendations for optimal numerical model that can beused in joint design.

  • 162.
    Al-Ramahi, Nawres
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Varna, Janis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Numerical stress analysis in adhesive joints under thermo-mechanical load using model with special boundary conditions2019Inngår i: 2nd International Conference on Sustainable Engineering Techniques (ICSET 2019)6–7 March 2019, Baghdad, Iraq, Institute of Physics (IOP), 2019, Vol. 3, artikkel-id 032061Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A numerical study of the adhesive joint made of similar and dissimilar adherends subjected to thermo-mechanical loading is presented. A comprehensive numerical model was used for this purpose with the novel displacement coupling conditions which are able to correctly represent monoclinic materials (off-axis layers of composite laminates). The geometrical nonlinearity as well as nonlinear material model are also taken into account. Three different types of single-lap and double-lap adhesive joints are considered in this study: a) metal-metal; b) composite-composite; c) composite-metal. In case of composite laminates, four lay-ups are evaluated: uni-directional ([08]T and [908]T) and quasi-isotropic laminates ([0/45/90/-45]S and [90/45/0/-45]S). This paper focuses on the parameters which have the major effect on the peel and shear stress distribution within adhesive layer at the overlap ends. The comparison of behaviour of single- and double- lap joints in relation to these parameters is made. The master curves for maximum stress (peel and shear) at the ends of the overlap with respect to the bending stiffness and axial modulus of the adherends are constructed by analysing stress distributions in the middle of the adhesive. The main conclusions of this paper are: the maximum peel stress value for SLJ is reduced with increase of the adherend bending stiffness and for DLJ, similar behaviour was observed at the end next to the inner plate corner, while, at the end next to the outer plate corner peel stress is reduced with increase of adherend axial modulus.

    Fulltekst (pdf)
    fulltext
  • 163.
    Alvi, Sajid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Lulea University of Technology.
    Synthesis and Characterization of High Entropy Alloy and Coating2019Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    High entropy alloys (HEAs) are a new class of alloys that contains five or more principal elements in equiatomic or near-equiatomic proportional ratio. The configuration entropy in the HEAs tends to stabilize the solid solution formation, such as body-centered-cubic (BCC), face-centered-cubic (FCC) and/or hexagonal-closed-pack (HCP) solid solution. The high number of principal elements present in HEAs results in severe lattice distortion, which in return gives superior mechanical properties compared to the conventional alloys. HEAs are considered as a paradigm shift for the next generation high temperature alloys in extreme environments, such as aerospace, cutting tools, and bearings applications.

    The project is based on the development of refractory high entropy alloy and film. The first part of the project involves designing high entropy alloy of CuMoTaWV using spark plasma sintering (SPS) at 1400 oC. The sintered alloy showed the formation of a composite of BCC solid solution (HEA) and V rich zones with a microhardness of 600 HV and 900 HV, respectively. High temperature ball-on-disc tribological studies were carried out from room temperature (RT) to 600 oC against Si3N4 counter ball. Sliding wear characterization of the high entropy alloy composite showed increasing coefficient of friction (COF) of 0.45-0.67 from RT to 400 oC and then it decreased to 0.54 at 600 oC. The wear rates were found to be low at RT (4 × 10⁠−3 mm⁠3/Nm) and 400 oC (5 × 10⁠−3 mm⁠3/Nm) and slightly high at 200 oC (2.3 × 10⁠−2 mm⁠3/Nm) and 600 oC (4.5 × 10⁠−2 mm⁠3/Nm). The tribology tests showed adaptive behavior with lower wear rate and COF at 400 oC and 600 oC, respectively. The adaptive wear behavior at 400 oC was due to the formation of CuO that protected against wear, and at 600 oC, the V-rich zones converted to elongated magneli phases of V2O5 and helped in reducing the friction coefficient.

    The second part of the project consists of sintering of novel CuMoTaWV target material using SPS and depositing CuMoTaWV refractory high entropy films (RHEF) using DC-magnetron sputtering on silicon and 304 stainless steel substrate. The deposited films showed the formation of nanocrystalline BCC solid solution. The X-ray diffraction (XRD) studies showed a strong (110) preferred orientation with a lattice constant and grain size of 3.18 Å and 18 nm, respectively. The lattice parameter were found to be in good agreement with the one from the DFT optimized SQS (3.16 Å). The nanoindentation hardness measurement at 3 mN load revealed an average hardness of 19 ± 2.3 GPa and an average Young’s modulus of 259.3 ± 19.2 GPa. The Rutherford backscattered (RBS) measurement showed a gradient composition in the cross-section of the film with W, Ta and Mo rich at the surface, while V and Cu were found to be rich at the substrate-film interface. AFM measurements showed an average surface roughness (Sa) of 3 nm. Nano-pillars of 440 nm diameter from CuMoTaWV RHEFs were prepared by ion-milling in a focused-ion-beam (FIB) instrument, followed by its compression. The compressional yield strength and Young’s modulus was calculated to be 10.7 ± 0.8 GPa and 196 ± 10 GPa, respectively. Room temperature ball-on-disc tribological test on the CuMoTaWV RHEF, after annealing at 300 oC, against E52100 alloy steel (Grade 25, 700-880 HV) showed a steady state COF of 0.25 and a low average wear rate of 6.4 x 10-6 mm3/Nm.

    Fulltekst (pdf)
    fulltext
  • 164.
    Alvi, Sajid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    High temperature tribology of CuMoTaWV high entropy alloy2019Inngår i: Wear of Materials, 2019, Vol. 426-427, s. 412-419Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An equiatomic high entropy alloy (HEA) CuMoTaWV was designed for room temperature to high temperature wear applications using spark plasma sintering of elemental powder mixture at 1400 °C. The sintered solid solution showed uniform distribution of elements in a BCC high entropy alloy phase along with V rich solid solution phase with an average hardness of 600 Hv and 900 Hv, respectively. Room temperature (RT) dry sliding wear tests, against alloy steel (700–880 Hv) for 200 m sliding distance at 5 N normal load, showed negligible wear of 5 × 10−7 mm/N m and a coefficient of friction (COF) of 0.5. Sliding wear characterization of sintered CuMoTaWV alloy against Si3N4 (1550 Hv) counter body from RT to 600 °C showed an increasing average COF of 0.45–0.67 from RT to 400 °C and then reducing to 0.54 at 600 °C. The wear rate was found to be lower at RT (4 × 10−3 mm3/N m) and 400 °C (5 × 10−3 mm3/N m), and slightly higher at 200 °C (2.3 × 10−2 mm3/N m) and 600 °C (4.5 × 10−2 mm3/N m). The CuMoTaWV alloy showed wear mechanisms specific to the test temperatures. The wear of CuMoTaWV alloy was governed by adhesive wear at RT and 200 °C and oxidative wear at 400 °C and 600 °C. The analyses of wear surfaces showed that the low wear rate at RT was due to the high hardness of the HEA, presence of V rich zones and formation of W and Ta tribofilm. At 400 °C, the formation of CuO tribolayer reduced the wear and hindered oxidation of wear track. At 600 °C, the wear rate increased due to oxidation of Cu, Ta and W. Moreover, the formation of lubricating elongated magneli phase V2O5 in V rich regions of CuMoTaWV alloy reduced the COF to 0.54.

  • 165.
    Alvi, Sajid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    High temperature tribology of polymer derived ceramic composite coatings2018Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, artikkel-id 15105Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polymer derived ceramic (PDC) composite coatings were deposited on AISI 304 substrates using siloxane based preceramic polymer polymethlysilsquioxane (PMS) and ZrSi2 as active filler or Ag as passive filler. The tribological performance of the composite coatings was evaluated at room temperature and moderately high temperatures (150 °C, 200 °C, 300 °C and 400 °C). The composite coatings showed low coefficient of friction (COF), µ, from 0.08 to 0.2 for SiOC-ZrSi2 composite coatings, and from 0.02 to 0.3 for SiOC-Ag composite coatings, at room temperature with increasing normal load from 1 to 5 N. High temperature tribology tests showed high COF values from 0.4 to 1 but low wear for SiOC-ZrSi2 coating, and low COF from 0.2 to 0.3 for SiOC-Ag coatings at lower temperature ranges. Low load friction tests at room temperature showed negligible wear in SiOC-ZrSi2 coatings, suggesting good wear resistant and lubricating properties due to formation of t-ZrO2 and carbon. Low COF and high amount of wear was observed in SiOC-Ag composite coatings at room temperature due to high ductility of Ag and smearing of wear debris in the wear track. The coatings and wear tracks were characterized to evaluate the lubrication and wear behavior.

  • 166.
    Alvi, Sajid Ali
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Ghamgosar, Pedram
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Rigoni, Federica
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Vomiero, Alberto
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Adaptive nanolaminate coating by atomic layer deposition2019Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 692, artikkel-id 137631Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Atomic layer deposition (ALD) was used to deposit ZnO/Al2O3/V2O5 nanolaminate coatings to demonstrate a coating system with temperature adaptive frictional behaviour. The nanolaminate coating exhibited excellent conformity and crack-free coating of thickness 110 nm over Inconel 718 substrate. The ALD trilayer coating showed a hardness and elastic modulus of 12 GPa and 193 GPa, respectively. High-temperature tribology of the nanolaminate trilayer was tested against steel ball in dry sliding condition at 25 °C (room temperature, RT), 200 °C, 300 °C, and 400 °C. It was found that the nanolaminate coating showed a low coefficient of friction (COF) and wear rate at RT and 300 °C. The trilayer coating was found intact and stable at all temperatures during the friction tests. The adaptability of nanolaminate coating with the temperature was verified by performing the cyclic friction test at 300 °C and RT. The low COF and wear rate had been attributed to the (100) and (002) basal plane sliding of ZnO top layer, and the interlayer sliding of weakly bonded planes parallel to (001) plane in V2O5 bottom layer. Furthermore, even after the removal of ZnO coating during the tribotest, the bottom V2O5 layer coating stabilized the COF and wear rate at RT and 300 °C.

  • 167.
    Alvi, Sajid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Jarzabek, Dariusz M.
    Department of Mechanics of Materials (ZMM), Institute of Fundamental Technological Research, Polish Academy of Sciences, 02-106 Warsaw, Poland.
    Gilzad Kohan, Mojtaba
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hedman, Daniel
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Jenczyk, Piotr
    Department of Mechanics of Materials (ZMM), Institute of Fundamental Technological Research, Polish Academy of Sciences, 02-106 Warsaw, Poland.
    Natile, Marta Maria
    CNR—Institute of Condensed Matter Chemistry and Technologies for Energy (ICMATE), I-16149 Genoa, Italy. Department of Chemical Sciences, University of Padova, 35131 Padova, Italy.
    Vomiero, Alberto
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Synthesis and Mechanical Characterization of a CuMoTaWV High-Entropy Film by Magnetron Sputtering2020Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 12, nr 18, s. 21070-21079Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Development of high-entropy alloy (HEA) films is a promising and cost-effective way to incorporate these materials of superior properties in harsh environments. In this work, a refractory high-entropy alloy (RHEA) film of equimolar CuMoTaWV was deposited on silicon and 304 stainless-steel substrates using DC-magnetron sputtering. A sputtering target was developed by partial sintering of an equimolar powder mixture of Cu, Mo, Ta, W, and V using spark plasma sintering. The target was used to sputter a nanocrystalline RHEA film with a thickness of ∼900 nm and an average grain size of 18 nm. X-ray diffraction of the film revealed a body-centered cubic solid solution with preferred orientation in the (110) directional plane. The nanocrystalline nature of the RHEA film resulted in a hardness of 19 ± 2.3 GPa and an elastic modulus of 259 ± 19.2 GPa. A high compressive strength of 10 ± 0.8 GPa was obtained in nanopillar compression due to solid solution hardening and grain boundary strengthening. The adhesion between the RHEA film and 304 stainless-steel substrates was increased on annealing. For the wear test against the E52100 alloy steel (Grade 25, 700–880 HV) at 1 N load, the RHEA film showed an average coefficient of friction (COF) and wear rate of 0.25 (RT) and 1.5 (300 °C), and 6.4 × 10–6 mm3/N m (RT) and 2.5 × 10–5 mm3/N m (300 °C), respectively. The COF was found to be 2 times lower at RT and wear rate 102 times lower at RT and 300 °C than those of 304 stainless steel. This study may lead to the processing of high-entropy alloy films for large-scale industrial applications.

  • 168.
    Alvi, Sajid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Saeidi, Kamran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    High temperature tribology and wear of selective laser melted (SLM) 316L stainless steel2020Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 448-449, artikkel-id 203228Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High temperature wear behaviour of selective laser melted (SLM) 316L stainless steel (SS) was studied to elucidate the influence of characteristic microstructure of SLM 316L SS on the wear properties. The wear tests were conducted from room temperature (RT) to 600 °C using ball-on-disc setup with alumina counter ball. The effect of temperature on the wear rate and the underlying mechanisms were evaluated and compared with conventional 316 SS. The RT coefficient of friction (COF) and wear rate of SLM 316L SS and conventional 316 SS were 0.5 and 4.6 ± 0.4 x 10−4 mm3/Nm and 0.7 and 4.5 ± 0.1 x 10−4 mm3/Nm, respectively. The wear rate of conventional 316 SS slightly decreased with increasing temperature from 4.5 ± 0.1 x 10−4 mm3/Nm at RT to 3.2 ± 0.1 x 10−4 mm3/Nm at 300 °C, followed by increasing to 4.9 ± 0.4 x 10−4 mm3/Nm at 400 °C, while the wear rate of SLM 316L SS was twofold lower with 2.3 ± 0.6 x 10−4 mm3/Nm at 300 °C and 2.7 ± 0.3 x 10−4 mm3/Nm at 400 °C. The wear rate at 600 °C was found to be comparable between SLM 316L SS and conventional 316 SS with a wear rate of 6.4 ± 0.7 x 10−4 mm3/Nm and 6.6 ± 0.6 x 10−4 mm3/Nm, respectively. The lower wear rate in SLM 316L SS at higher temperatures of 300 °C and 400 °C was due to its stable hierarchical microstructure, cellular subgrains, formation of stable oxide glaze and higher hardness. Moreover, the cross-sectional microscopy of wear track after 600 °C wear tests showed that the deformation zone below the wear track in SLM 316L SS was 10–15 μm compared to 30–40 μm for conventional 316 SS. The two folds low wear rate of the SLM 316L SS at 300 °C and 400 °C compared to conventional 316 SS could potentially render it for usage in applications where high temperature wear resistant SS are needed.

  • 169.
    Alvi, Sajid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Zhang, Hanzhu
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    High-Entropy Ceramics2019Inngår i: High Entropy Alloys, INTECH, 2019Kapittel i bok, del av antologi (Fagfellevurdert)
  • 170.
    Amer, Eynas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Sjödahl, Mikael
    Impact of an extended source in laser ablation using pulsed digital holographic interferometry and modelling2009Inngår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 255, nr 21, s. 8917-8925Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pulsed digital holographic interferometry has been used to study the effect of the laser spot diameter on the shock wave generated in the ablation process of an Nd:YAG laser pulse on a Zn target under atmospheric pressure. For different laser spot diameters and time delays, the propagation of the expanding vapour and of the shock wave were recorded by intensity maps calculated using the recorded digital holograms. From the latter phase maps, the refractive index and the density field can be derived. A model was developed that approaches the density distribution, in particular the ellipsoidal expansion characteristics. The induced shock wave has an ellipsoid shape that approaches a sphere for decreasing spot diameter. The ellipsoidal shock waves have almost the same centre offset towards the laser beam and the same aspect ratio for different time steps. The model facilitates the derivation of the particle velocity field. The method provides valuable quantitative results that are discussed, in particular in comparison with the simpler point source explosion theory.

  • 171.
    Amer, Eynas
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Shaer, M. El
    Department of Engineering Physics and Mathematics, Faculty of Engineering, Zagazig University.
    Comparison of the laser ablation process on Zn and Ti using pulsed digital holographic interferometry2010Inngår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 256, nr 14, s. 4633-4641Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pulsed digital holographic interferometry has been used to compare the laser ablation process of a Q-switched Nd-YAG laser pulse (wavelength 1064 nm, pulse duration 12 ns) on two different metals (Zn and Ti) under atmospheric air pressure. Digital holograms were recorded for different time delays using collimated laser light (532 nm) passed through the volume along the target. Numerical data of the integrated refractive index field were calculated and presented as phase maps. Intensity maps were calculated from the recorded digital holograms and are used to calculate the attenuation of the probing laser beam by the ablated plume. The different structures of the plume, namely streaks normal to the surface for Zn in contrast to absorbing regions for Ti, indicates that different mechanisms of laser ablation could happen for different metals for the same laser settings and surrounding gas. At a laser fluence of 5 J/cm2, phase explosion appears to be the ablation mechanism in case of Zn, while for Ti normal vaporisation seems to be the dominant mechanism.

  • 172.
    Andersons, J.
    et al.
    University of Latvia.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Estimation of the tensile strength of an oriented flax fiber-reinforced polymer composite2011Inngår i: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 42, nr 9, s. 1229-1235Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Unidirectional orientation of natural fibers in a polymer composite ensures the highest efficiency of reinforcement. Flax fiber reinforcement is discontinuous due to limited fiber length and heterogeneous due to the presence of elementary fibers and their bundles. In order to assess the upper limit of tensile strength of such slightly misoriented, nominally UD natural fiber composite, a statistical strength model of continuous UD fiber reinforced composites is applied. It is found that the experimental strength of UD flax composites, produced from rovings or manually aligned fibers, approaches the theoretical limit only at relatively low fiber volume fraction ca. 0.2, being markedly below it at higher fiber content.

  • 173.
    Andersons, J.
    et al.
    University of Latvia.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hojo, M.
    Ochiai, S.
    Kyoto University.
    Fibre fragment distribution in a single-fibre composite tension test2001Inngår i: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 32, nr 4, s. 323-332Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Single fibre fragmentation tests are performed for brittle fibres with Weibull strength distribution and different surface treatments. The fragmentation process is modelled and closed-form expressions for break spacing distribution are obtained. The model accounts for the effect of finite fibre length on the initial fragmentation as well as for break interaction on the advanced fragmentation stage. It is assumed that the exclusion zone due to fibre-matrix interface failure and stress recovery in the fibre is linearly dependent on the applied load. This assumption is validated experimentally. The derived theoretical average fragment length dependence on applied load is used to determine the fibre strength distribution parameters and the effective interfacial shear stress for carbon/epoxy single fibre composites with different fibre surface treatment and for glass/vinylester single fibre composite. Fragment length distribution is predicted for several load levels. Predictions are in good agreement with experimental data

  • 174.
    Andersons, J.
    et al.
    University of Latvia.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hojo, M.
    Mesoscopic Materials Research Center, Kyoto University.
    Ochiai, S.
    Mesoscopic Materials Research Center, Kyoto University.
    Glass fibre strength distribution determined by common experimental methods2002Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 62, nr 1, s. 131-145Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The tensile strength of brittle fibres is routinely described by the Weibull distribution. The parameters of the distribution can be obtained from tests on single fibres and fibre bundles or from model composite tests. However, there is growing evidence that the distribution parameters obtained by different experimental techniques differ systematically. In order to investigate the possible causes of such discrepancies, single-fibre tension, fibre bundle, and single-fibre fragmentation tests are employed in this study to obtain strength distribution of commercial E-glass fibres. The results reveal parameter dependence on the approach used to extract the distribution parameters from experimental data. Particularly, in the case of single-fibre tension tests, the shape parameter obtained from average fibre strength vs. length data is larger than that obtained at a fixed gauge length. It is assumed that the apparent fibre strength scatter is caused by both the inherent flaw structure along a fibre and by the fibre-to-fibre strength variability within a batch, due to slightly differing processing and handling history of the fibres. Fibre fragmentation test results are used to derive the Weibull distribution parameters applicable to the fibre batch. The strength distribution obtained is compared with strength data for the single fibres, and reasonably good agreement is observed.

  • 175.
    Andersons, J.
    et al.
    Institute of Polymer Mechanics, University of Latvia.
    Joffe, Roberts
    Sandmark, R.
    Materials division, SINTEF SI.
    Constrained fragmentation of composites under uniaxial loading1995Inngår i: Mechanics of composite materials, ISSN 0191-5665, E-ISSN 1573-8922, Vol. 31, nr 1, s. 26-33Artikkel i tidsskrift (Fagfellevurdert)
  • 176.
    Andersons, J.
    et al.
    Institute of Polymer Mechanics, University of Latvia.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sparnins, Edgars
    Institute of Polymer Mechanics, University of Latvia.
    Weichert, D.
    Institute of General Mechanics, RWTH-Aachen University.
    Modeling the effect of reinforcement discontinuity on the tensile strength of UD flax fiber composites2011Inngår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 46, nr 15, s. 5104-5110Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To exploit the potential of natural fibers as reinforcement of polymer matrix composites, aligned bast fiber composite materials are being produced and studied. Bast fiber reinforcement is discontinuous due to the limited length of natural fibers, which needs to be reflected in predictive models of mechanical properties of composites. The strength in tension in the fiber direction of an aligned flax fiber-reinforced composite is modeled assuming that a cluster of adjacent fiber discontinuities is the origin of fracture. A probabilistic model of tensile strength, developed for UD composites containing a microdefect, is applied. It follows from the theoretical analysis that the experimental tensile strength as a function the fiber volume fraction can be described with acceptable accuracy assuming the presence of a cluster of ca. 4 × 4 elementary fiber discontinuities

  • 177.
    Andersons, J.
    et al.
    Institute of Polymer Mechanics, University of Latvia.
    Leterrier, Y.
    École Polytechnique Fédérale de Lausanne.
    Joffe, Roberts
    Statistical model of coating fragmentation under equibiaxial load1998Inngår i: Materials and Manufacturing Processes, ISSN 1042-6914, E-ISSN 1532-2475, Vol. 13, nr 4, s. 597-602Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A statistical model of coating cracking under equibiaxial tension is proposed based on a Weibull strength distribution for the coating. Crack length and spacing distributions are derived assuming that cracks initiate in random locations and propagate straight till stopping upon encountering a geometiical obstacle (another crack). The theoretical distributions are verified by comparing with simulated cracking patterns obtained by the Monte-Carlo method. An analysis of crack patterns of SiO2 coatings on a PET film under biaxial tension is performed. Qualitative agreement with the theoretical crack spacing distribution is observed.

  • 178.
    Andersons, J.
    et al.
    University of Latvia.
    Sparnins, Edgars
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Prediction of crack onset strain in composite laminates at mixed mode cracking2009Inngår i: 5th International EEIGM/AMASE/FORGEMAT Conference on Advanced Materials Research, Bristol: IOP Publishing Ltd , 2009, Vol. 5Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Failure process of continuous fiber reinforced composite laminates in tension usually starts with appearance of intralaminar cracks. In composite laminates with complex lay-ups and/or under combined loading, intralaminar cracks may develop in plies with different reinforcement directions. A necessary part of mixed mode cracking models is the criterion of failure. For propagation-controlled fracture it is usually formulated in terms of energy release rates and their critical values of the particular composite material. Intralaminar fracture toughness of unidirectionally reinforced glass/epoxy composite was experimentally determined at several mode I and mode II ratios. It is found that the crack propagation criterion, linear in terms of the energy release rates, reasonably well approximates the test results. The determined mixed mode cracking criterion was applied to predict intralaminar crack onset in cross-ply glass/epoxy composite under tensile loading. The predicted crack onset strain values agree with test results at small off-axes angles of the cracking ply (on-axis and 15° off-axis loading), but underestimate crack onset at larger reinforcement angles with respect to the loading direction. The discrepancy is likely to be caused by the deviation of linearity in laminate response before cracking onset in these laminates, related to non-linear shear characteristics of unidirectional plies. The applicability of strength-based fracture criterion for initiation-controlled cracking is discussed.

    Fulltekst (pdf)
    FULLTEXT01
  • 179.
    Andersons, J.
    et al.
    University of Latvia, Riga.
    Sparnins, Edgars
    Institute of Polymer Mechanics, University of Latvia.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Stiffness and strength of flax fiber/polymer matrix composites2006Inngår i: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 27, nr 2, s. 221-229Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Flax fiber composites with thermoset and thermoplastic polymer matrices have been manufactured and tested for stiffness and strength under uniaxial tension. Flax/polypropylene and flax/maleic anhydride grafted polypropylene composites are produced from compound obtained by coextrusion of granulated polypropylene and flax fibers, while flax fiber mat/vinylester and modified acrylic resin composites are manufactured by resin transfer molding. The applicability of rule-of-mixtures and orientational averaging based models, developed for short fiber composites, to flax reinforced polymers is considered.

  • 180.
    Andersons, Janis
    et al.
    Institute of Polymer Mechanics, University of Latvia.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Initiation and propagation controlled intralaminar cracking in cross-ply laminates: Chapter 102009Inngår i: Encyclopedia of Polymer Composites: Properties, Performance and Applications, New York: Nova Science Publishers, Inc., 2009Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 181.
    Andersons, Janis
    et al.
    Institute of Polymer Mechanics, University of Latvia.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mechanical damage characteristics of elementary hemp fibers and scale effect of fiber strength2012Inngår i: High Performance Structure and Materials VI: papers presented at the 6th International Conference on High Performance Structures and Materials held at the Wessex Institute of Technology in the New Forest, UK] / [ed] W.P. De Wilde; C.A. Brebbia; S. Hernandez, Southampton: WIT Press, 2012, s. 157-167Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Ecological and economical considerations foster replacement of man-made fibers by natural renewable fibers in various industrial applications. Bast fibers of such plants as, e.g., flax, hemp, jute etc., are particularly attractive as a reinforcement of polymer-matrix composites due to their high specific stiffness and strength in the axial direction. The elementary bast fibers exhibit pronounced scatter of strength. It necessitates probabilistic description of their strength via a distribution function that reflects damage morphology and severity in fibers. Fiber fracture is shown to originate from mechanical defects of the bast cell wall, the most prominent of them being kink bands. While the number of kink bands in a fiber is easily determined by optical microscopy, direct experimental measurement of their strength is complicated. Therefore, alternative approaches are sought, enabling extraction of strength characteristics of the kink bands from fiber tests via appropriate probabilistic models. Analytical distribution function of bast fiber strength has been derived, allowing for the effect of mechanical damage in the form of kink bands. The fiber characteristics measured have been used to evaluate the kink band density and strength distributions. The theoretical distribution is verified against experimental tensile strength data of elementary hemp fibers at several gauge lengths and found to provide acceptable accuracy in predicting the scale effect of strength.

  • 182. Andersons, Janis
    et al.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sparnins, Edgars
    Institute of Polymer Mechanics, University of Latvia.
    Evaluation of interfacial shear strength by tensile tests of impregnated flax fiber yarns2012Inngår i: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 46, nr 3, s. 351-357Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Adhesion of flax fibers and polymer matrix as well as mutual bonding of elementary fibers in a technical fiber are among the principal factors governing the mechanical response of flax fiber reinforced polymer-matrix composites. A method for evaluation of adhesion is proposed based on tension tests of impregnated fiber yarns, with subsequent characterization by optical microscopy of length distribution of fibers pulled out of the yarn fracture surfaces. An elementary probabilistic model is derived relating aspect ratio distribution of the pulled out fibers to the fiber tensile strength distribution and the effective interfacial shear strength. The method was applied to flax fiber/vinylester resin yarns and an estimate of interfacial shear strength at 17 MPa was obtained.

  • 183.
    Andersons, Janis
    et al.
    Institute of Polymer Mechanics, University of Latvia.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sparnins, Edgars
    Statistical model of the transverse ply cracking in cross-ply laminates by strength and fracture toughness based failure criteria2008Inngår i: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 75, nr 9, s. 2651-2665Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cross-ply laminate subjected to tensile loading provides a relatively well understood and widely used model system for studying progressive cracking of the transverse ply. This test allows to identify material strength and/or toughness characteristics as well as to establish relation between damage level and the composite stiffness reduction. The transverse ply cracking is an inherently stochastic process due to the random variability of local material properties of the plies. The variability affects both crack initiation (governed by the local strength) and propagation (governed by the local fracture toughness). The primary aim of the present study is elucidation of the relative importance of these phenomena in the fragmentation process at different transverse and longitudinal ply thickness ratios. The effect of the random crack distribution on the mechanical properties reduction of the laminate is also considered. Transverse ply cracking in glass fiber/epoxy cross-ply laminates of the lay-ups [02/902]s, [0/902]s, and [0/904]s is studied. Several specimens of each lay-up were subjected to uniaxial quasistatic tension to obtain crack density as a function of applied strain. Crack spacing distributions at the edge of the specimen also were determined at a predefined applied strain. Statistical model of the cracking process is derived, calibrated using crack density vs. strain data, and verified against the measured crack spacing distributions.

  • 184.
    Andersons, Janis
    et al.
    Institute of Polymer Mechanics, University of Latvia.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sparnins, Edgars
    Rubenis, Oskars
    Institute of Polymer Mechanics, University of Latvia.
    Progressive cracking mastercurves of the transverse ply in a laminate2009Inngår i: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 30, nr 8, s. 1175-1182Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, progressive cracking of a transverse layer in a cross-ply composite laminate subjected to tensile loading is considered. Using the results of a probabilistic cracking model, approximate relations for crack density as a function of stress are derived for initiation-controlled and propagation-controlled cracking. It is shown that the crack density evolution in the transverse ply can be represented by a mastercurve in suitably normalized coordinates. The mastercurve approach is applied to progressive cracking in glass/epoxy laminates

  • 185.
    Andersons, Janis
    et al.
    Institute of Polymer Mechanics, University of Latvia.
    Modniks, Janis
    Institute of Polymer Mechanics, University of Latvia.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    An Improved Method For Identification Of The Interfacial Shear Strength By Tensile Tests Of Short-Fiber Composites2015Inngår i: Proceedings of 7th International Conference on Composites Testing and Model Identification / [ed] C. González; C. López; J. LLorca, Madrid, Spain: IMDEA, Madrid (SPAIN) , 2015Konferansepaper (Fagfellevurdert)
    Fulltekst (pdf)
    FULLTEXT01
  • 186.
    Andersons, Janis
    et al.
    Institute of Polymer Mechanics, University of Latvia.
    Modniks, Janis
    Institute of Polymer Mechanics, University of Latvia.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Madsen, Bo
    Technical University of Denmark, Risø Campus, Materials Research Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark.
    Nättinen, Kalle
    Bemis Flexible Packaging Europe, Bemis Valkeakoski Oy.
    Apparent interfacial shear strength of short-flax-fiber/starch acetate composites2016Inngår i: International Journal of Adhesion and Adhesives, ISSN 0143-7496, E-ISSN 1879-0127, Vol. 64, s. 78-85Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The paper deals with an indirect industry-friendly method for identification of the interfacial shear strength (IFSS) in a fully bio-based composite. The IFSS of flax fiber/starch acetate is evaluated by a modified Bowyer and Bader method based on an analysis of the stress-strain curve of a short-fiber-reinforced composite in tension. A shear lag model is developed for the tensile stress-strain response of short-fiber-reinforced composites allowing for an elasticperfectly plastic stress transfer. Composites with different fiber volume fractions and a variable content of plasticizer have been analyzed. The apparent IFSS of flax /starch acetate is within the range of 5.5 to 20.5 MPa, depending on composition of the material. The IFSS is found to be greater for composites with a higher fiber loading and to decrease with increasing content of plasticizer. The IFSS is equal or greater than the yield strength of the neat polymer, suggesting good adhesion, as expected for the chemically compatible constituents.

  • 187.
    Andersons, Janis
    et al.
    Institute of Polymer Mechanics, University of Latvia.
    Sparnins, Edgars
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    The onset of mixed mode intralaminar cracking in a cross-ply composite laminate2008Inngår i: Mechanics of composite materials, ISSN 0191-5665, E-ISSN 1573-8922, Vol. 44, nr 6, s. 549-556Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The intralaminar fracture toughness of a unidirectionally reinforced glass/epoxy composite is determined experimentally at several mode I and mode II loading ratios. The crack propagation criterion, expressed as a quadratic form in terms of single-mode stress intensity factors (alternatively, linear in terms of energy release rates), approximates the test results reasonably well. The mixed-mode cracking criterion obtained is used to predict the intralaminar crack on set in a cross-ply glass/epoxy composite under off-axis tensile loading.

  • 188.
    Andersons, Janis
    et al.
    Institute of Polymer Mechanics, University of Latvia.
    Sparnins, Edgars
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Uniformity of filament strength within a flax fiber batch2009Inngår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 44, nr 2, s. 685-687Artikkel i tidsskrift (Fagfellevurdert)
  • 189.
    Andersons, Janis
    et al.
    Institute of Polymer Mechanics, University of Latvia.
    Sparnins, Edgars
    Institute of Polymer Mechanics, University of Latvia.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Wallström, Lennart
    Strength distribution of elementary flax fibres2005Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 65, nr 3-4, s. 693-702Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Flax fibres, along with a number of other natural fibres, are being considered as an environmentally friendly alternative of synthetic fibres in fibre-reinforced polymer composites. A common feature of natural fibres is a much higher variability of mechanical properties. This necessitates study of the flax fibre strength distribution and efficient experimental methods for its determination. Elementary flax fibres of different gauge lengths are tested by single fibre tension in order to obtain the stress-strain response and strength and failure strain distributions. The applicability of single fibre fragmentation test for flax fibre failure strain and strength characterization is considered. It is shown that fibre fragmentation test can be used to determine the fibre length effect on mean fibre strength and limit strain.

  • 190.
    Andersons, Janis
    et al.
    Institute of Polymer Mechanics, University of Latvia.
    Sparnins, Edgars
    Nyström, Birgitha
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Scale effect of the tensile strength of flax-fabric-reinforced polymer composites2011Inngår i: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 30, nr 23, s. 1969-1974Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The development of UD natural fiber composites, considered for application as structural materials, necessitates evaluation of the scale effect of their strength. Alignment of the fibers in flax bast fiber composites can be achieved by employing textile reinforcement, such as yarns and fabrics. Cutting specimens for mechanical tests out of such textile-reinforced composite plates results in a complex non-uniform reinforcement structure at their edges, which may affect the strength of specimens. Scale effect of the tensile strength in the fiber direction of flax fabric reinforced composites is studied in the current work. A model accounting for both volume and edge effect of the specimens on their tensile strength is proposed.

  • 191.
    Andersons, Janis
    et al.
    Institute of Polymer Mechanics, University of Latvia.
    Sparnins, Edgars
    Porike, Evija
    Institute of Polymer Mechanics, University of Latvia.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Strength distribution of elementary flax fibres due to mechanical defects2008Inngår i: 11th International Inorganic-Bonded Fiber Composites Conference (IIBCC): Madrid, Nov. 4 - 7, 2008. Proceedings / [ed] Blanco Suárez; Maria Ángeles, Madrid: Universidad Complutense de Madrid , 2008Konferansepaper (Fagfellevurdert)
  • 192.
    Andersons, Janis
    et al.
    Institute of Polymer Mechanics, University of Latvia.
    Sparnins, Edgars
    Rubenis, Ojars
    Institute of Polymer Mechanics, University of Latvia.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Estimation of laminate stiffness reduction due to cracking of a transverse ply by employing crack initiation- and propagation-based master curves2008Inngår i: Mechanics of composite materials, ISSN 0191-5665, E-ISSN 1573-8922, Vol. 44, nr 5, s. 441-450Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The applicability range of toughness-and strength-based criteria for progressive cracking of a transverse layer in a cross-ply composite laminate subjected to tensile loading is considered. Using a deterministic cracking model, approximate relations for the crack density as a function of stress are derived for initiation-and propagation-controlled types of cracking. The master-curve approach is applied to progressive cracking in glass/epoxy laminates. The accuracy of estimation of laminate stiffness reduction by using crack density master curves is evaluated.

  • 193.
    Andersson, Anders
    et al.
    Luleå tekniska universitet.
    Engström, Hans
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Wiklund, Greger
    Påsvetsning, upplegering och ytomsmältning (glasering) med högeffektlaser1983Rapport (Annet vitenskapelig)
  • 194.
    Andersson, Anton
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Recycling of Blast Furnace Sludge within the Integrated Steel Plant: Potential for Complete Recycling and Influence on Operation2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Ore-based steelmaking generates various residues including dust, sludges, scales and slags. Internal and external recycling has allowed for 68-90 % of the dust, sludges and scales to be recycled. However, several residues are landfilled despite containing elements valuable as raw material in the production of steel. One such residue is the blast furnace (BF) sludge which has a chemical composition dominated by iron and carbon. In 2008, the annual worldwide landfilling of BF sludge was estimated to 8 million metric tons in dry weight. Furthermore, as the iron production via the BF route has increased significantly since 2008, the landfilling of BF sludge could be even higher as of today. Thus, the potential to reclaim valuable iron and carbon while improving the raw material efficiency is substantial.

    Traditionally, in-plant recycling of residues generated in the integrated steel plant is conducted via the sinter or, in the case of pellet-based BFs, via cold-bonded briquettes and injection in the BF tuyeres. The challenges in recycling BF sludge via these routes are the fine particle size distribution, the high water content and the zinc content. Of these challenges, the latter is the main concern as too high zinc loads in the BF lead to increased reductant rates, reduced lining life of carbon-based bricks and scaffold formation, which may disturb the process. The challenge regarding zinc has previously been addressed by pretreating the sludge, generating a low-zinc and high-zinc fraction where the former has been recycled to the BF via the sinter or cold-bonded pellets. Although pretreatment and recycling of the low-zinc fraction have been achieved in industrial scale, the reported sludges are generally coarse in size and high in zinc. Furthermore, recycling of pretreated BF sludge to the BF utilizing cold-bonded briquettes has not been reported and the internal recycling of the high-zinc fraction has not been considered.

    In the present thesis, newly produced BF sludge with a fine particle size distribution and low zinc content was characterized finding that a majority of the zinc was present in weak acid soluble phases and that the finest fraction of the sludge carried most of the zinc. Based on these findings, the BF sludge was pretreated using sulfuric acid leaching, hydrocycloning and tornado treatment, respectively. Sulfuric acid leaching was the most effective method in selectively separating zinc from the iron, carbon and solids. However, both hydrocycloning and tornado treatment were successful in generating a fraction low in zinc.

    The low-zinc fraction of the tornado-treated BF sludge was incorporated in cold-bonded briquettes and tested for strength, swelling and intrinsic reducibility. Furthermore, the briquettes were charged as basket samples in the LKAB Experimental Blast Furnace (EBF) in order to study the behavior in actual BF conditions. The results suggested that the low-zinc fraction of the BF sludge could be added to the briquettes without negatively affecting the performance of the briquettes in the BF. The results were confirmed in industrial-scale trials where non-treated BF sludge was added to cold-bonded briquettes in an amount that would facilitate complete recycling of the low-zinc fraction. Charging these briquettes to the BF did not induce any negative effects on the process or the hot metal (HM) quality.

    The high-zinc fraction of the tornado-treated BF sludge was added in self-reducing cold-bonded agglomerates and studied in technical-scale smelting reduction experiments aiming at recycling to the HM desulfurization plant. The experiments suggested that melt-in problems could be expected when using either briquettes or pellets. Nonetheless, industrial-scale trials were performed aiming to study the feasibility of recycling cold-bonded briquettes to both the HM desulfurization plant and basic oxygen furnace (BOF). These trials suggested that a substantial amount could be recycled without affecting the final quality of the steel. However, additional experiments were identified to be required in order to enable 100 % recycling of the high-zinc fraction of the tornado-treated BF sludge.

    Based on the results from the experimental work, a holistic concept to completely recycle the BF sludge within the integrated steel plant was suggested.

    Fulltekst (pdf)
    fulltext
  • 195.
    Andersson, Anton
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Rosenkranz, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Samuelsson, Caisa
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Characterization and Upgrading of a Low Zinc-Containing and Fine Blast Furnace Sludge: A Multi-Objective Analysis2017Inngår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 57, nr 2, s. 262-271Artikkel i tidsskrift (Fagfellevurdert)
  • 196.
    Andersson, Anton
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Samuelsson, Caisa
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Characterization and Upgrading of Ore Based Steelmaking Sludges2015Inngår i: COM 2015: Conference of Metallurgists, 2015Konferansepaper (Annet vitenskapelig)
  • 197.
    Andersson, Anton
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Samuelsson, Caisa
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Characterization of Blast Furnace Sludge and Upgrading Using Physical Separation and Leaching2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The on-site sinter plants of the Swedish ore based steel industry are all closed. Instead of using sinter, the blast furnaces (BF) operate on iron ore pellets and the major part of the recycling of in-plant residues is realized via cold bonded briquettes charged to the BF. Cost of raw materials and energy continuously drives the work towards an increased recycling of in plant residues. The major part of the zinc entering the BF leaves through the top gas ending up in the BF dust and sludge. The recycling of all the BF dust back to the BF leaves the BF sludge as the main bleed of zinc out of the system. In order to utilize the iron and carbon content of the sludge, means to remove zinc is required prior to recycling via the briquette. In the present work, blast furnace sludge has been characterized. Using the characterization as standpoint, different operations for zinc removal was suggested and studied in laboratory scale. Zinc was successfully removed using a hydrometallurgical and physical separation route, respectively. A successful dezincing operation would enable the recycling of the sludge. This would improve the material- and energy efficiency and substantially decrease the amount of sludge being landfilled.

  • 198.
    Andersson, Anton
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Samuelsson, Caisa
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Björkman, Bo
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Feasible routes of blast furnace sludge upgrading in the light of its properties2016Inngår i: SCANMET V: 5th International Conference on Process Development in Iron and Steelmaking, Luleå, 12-15 June 2016, 2016Konferansepaper (Annet vitenskapelig)
  • 199.
    Andersson, Anton
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Andersson, Mats
    SSAB Europe.
    Kullerstedt, Adeline
    Swerim AB.
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Sundqvist Ökvist, Lena
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Recycling of the High-Zinc Fraction of Upgraded BF Sludge within the Integrated Steel Plant2018Konferansepaper (Fagfellevurdert)
  • 200.
    Andersson, Anton
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Andersson, Mats
    SSAB Europe.
    Kullerstedt, Adeline
    Swerim AB.
    Ahmed, Hesham
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    Sundqvist-Ökvist, Lena
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Mineralteknik och metallurgi.
    RECYCLING OF THE HIGH-ZINC FRACTION OF UPGRADED BF SLUDGE WITHIN THE INTEGRATED STEEL PLANT2018Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Ore-based steelmaking generates a variety of residues and recycling of these within the existing process or via other applications is essential for sustainable production from mainly  environmental aspects. In blast furnace (BF) ironmaking, the gas-cleaning equipment recovers the particles in the off-gas as BF dust and sludge. Traditionally, the dry dust is recycled back to the BF. In order to recycle the BF sludge together with the dust, the sludge has to be upgraded, removing zinc. The literature reports cases of recycling BF dust and the low-zinc fraction of upgraded BF sludge to the BF. However, research towards recycling of the high-zinc fraction of BF sludge within the ore-based steel plant is limited. In the present paper, the high-zinc fraction of tornado-treated BF sludge was incorporated in self-reducing cold-bonded agglomerates. The agglomerates were subjected to smelting reduction experiments aiming to study the feasibility of recycling the in-plant residues to the desulphurization plant. Difficulties in the melt-in of the agglomerates suggested that cold-bonded pellets were more suitable for recycling than the briquettes. However, full-scale trials suggested that cold-bonded briquettes can be used to recycle in-plant residues to the desulphurization plant without affecting the desulphurization process and final steel quality.

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