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  • 1.
    Abbasi, Saeed
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    Characterisation of airborne particles from rail traffic2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Since the investigation of wear particles in rail transport started in late-1910s, the high mass concentration of these particles has raised worries among researchers concerned with air quality. However, effective action has yet to be taken because of lack of relevant knowledge. This thesis provides applicable information for the airborne wear particles in rail transport. Some aspects of their characteristics such as diameter size, mass concentration, number concentration, and morphology of particles were investigated in field tests and laboratory tests.The effects on particle characterisations from different operational conditions in the field tests, and applying different braking materials, conducting tests in different applied loads or sliding velocities in the laboratory tests were studied. The main advantage of conducting laboratory tests was to focus on studying particles from one source. The possibility of repetition, using high sensitive instruments and conducting tests at low costs are the other advantages of laboratory studies. Paper A describes how a pin-on-disc machine was used to reproduce similar real operational conditions during mechanical braking in a train. The results were validated by comparing the field tests results with the laboratory studies. The particles morphology and size distribution were also studied.Paper B presents a summary of field tests results. The effects of curve negotiating and applying braking in different real conditions were investigated with an on-board measurement.The element composition of the particles and their potential sources were also investigated outside of the particles morphologies.Paper C presents comprehensive results from laboratory studies on airborne particles from different braking materials. The differences in the particle characteristics in similar test conditions were attributable to different material compositions and dominant wear mechanisms. A new index was introduced in this paper and is suggested to be used as a qualitative factor with regard to the airborne wear particle emission rate.Paper D is a review of the recent studies of exhaust emission and non-exhaust emission from rail vehicles. A summary of results, measurements, adverse health effects, and proposed or applied solutions are reviewed in this paper.

  • 2.
    Abdollahifakhr, Hamon
    et al.
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Computer Supported Engineering Design.
    Sengul, Ceyhun
    Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Computer Supported Engineering Design.
    AUTOMATIC DESIGN OF WIRING PATTERN FOR CAR SEAT HEATERS2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This projects aims to develop design automation in product development. Design automation causes increase in producibility and decrease in product cost and manufacturing lead time.

    The study at hand is proposed to provide a new method and to introduce procedure to the design of wiring pattern for a car seat heater for Kongsberg Automotive, KA. KA is a Norwegian company and a global provider of engineering, design, and manufacture for seat comfort, driver and motion control systems, fluid assemblies, and industrial driver interface products. The method that currently is used in the company to create a wiring pattern is neither sufficient enough nor automated.

    In order to design the wiring pattern, at first procedure is handled by the designer. Secondly, car seat heater 2D layout is imported and then, the dimensions of the elements are defined as constraints. Then VBA codes are opened and the program is run. The result will be a wiring pattern in different 2D layouts. To make the design process easier, we have modeled five different layouts; wiring pattern of one element, two elements, three elements, five elements (with two back sides) and one element trapezoidal 2D layout.

    The algorithm written in VBA (Visual basic for application) creates the pattern according to the dimensions of the elements which are used as inputs to define constrained parameters. The created macros are simple to use and easy to modify, independent from the programming knowledge. The user is only responsible with parameter input and running the program. The solution gives wiring pattern for a car seat heater.

  • 3.
    Abiri, Olufunminiyi
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Simplifications of non-local damage models2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Ductile fracture presents challenges with respect to material modelling and numerical simulations of localization. The strain and damage localization may be unwanted as it indicates a failure in the process or, as in the case of machining and cutting, a wanted phenomenon to be controlled. The latter requires a higher accuracy regarding the modelling of the underlying coupled plastic and fracturing/damage behaviour of the material, metal in the current context as well as the robustness of the simulation procedure. The focus of this thesis is on efficient and reliable finite element solution of the localization problem through the non-local damage model. The non-local damage model extends the standard continuum mechanics theory by using non-local continuum theory in order to achieve mesh independent results when simulating fracture or shear localization. In this work, the non-local damage model and its various simplifications are evaluated in an in-house finite element code developed using Matlab™. The accuracy, robustness, efficiency and costs of the models are investigated and also compared to a general multi-length scale finite element formulation. A numerical study versus published data is used to demonstrate the validity of the model. The explicit non-local damage variant will be implemented in a commercial finite element code for use in machining simulation

  • 4.
    Abiri, Olufunminiyi
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Non-local models in manufacturing simulations2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Ductile fracture presents challenges with respect to material modelling andnumerical simulations of localization. The strain and damage localization maybe unwanted as it indicates a failure in the process or, as in the case ofmachining and cutting, a wanted phenomenon to be controlled. The latterrequires a higher accuracy regarding the modelling of the underlying coupledplastic and fracturing/damage behaviour of the material, metal in the currentcontext as well as the stability and robustness of the simulation procedure.This aim of this work is to develop, evaluate and implement formulations thatcan efficiently and reliably handle localization problems in machiningsimulations. The focus is on non-local models. The non-local models extendthe standard continuum mechanics theory by using non-local continuumtheory in order to achieve mesh independent results when simulating fractureor shear localization.The non-local damage model is implemented and various formulations areevaluated in a Matlab™ based finite element code. The chosen algorithm wasthen implemented in commercial software. The implementations remedy themesh sensitivity problem and gives convergent solution for metal cuttingsimulations with reasonable cost. The length scale associated with the nonlocalmodels are in the current context considered as a numericalregularization parameter. The model has been applied in machiningsimulations and compared with measurements from industry.Keywords: Finite element simulation; Non-local damage; Plasticity; Machining

  • 5.
    Abiri, Olufunminiyi
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Non-local damage models in manufacturing simulations2013Conference paper (Refereed)
    Abstract [en]

    Localisation of deformation is a problem in several manufacturing processes. Machining is an exception where it is a wanted feature. However, it is always a problem in finite element modelling of these processes due to mesh sensitivity of the computed results. The remedy is to incorporate a length scale into the numerical formulations in order to achieve convergent solutions. Different simplifications in the implementation of a non-local damage model are evaluated with respect to temporal and spatial discretisation to show the effect of different approximations on accuracy and convergence.

  • 6.
    Abiri, Olufunminiyi
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Non-local damage models in manufacturing simulations2015In: European journal of mechanics. A, Solids, ISSN 0997-7538, E-ISSN 1873-7285, Vol. 49, 548-560 p.Article in journal (Refereed)
    Abstract [en]

    Localisation of deformation is a problem in several manufacturing processes. Machining is an exception where it is a wanted feature. However, it is always a problem in finite element modelling of these processes due to mesh sensitivity of the computed results. The remedy is to incorporate a length scale into the numerical formulations in order to achieve convergent solutions. Different simplifications in the implementation of a non-local damage model are evaluated with respect to temporal and spatial discretisation to show the effect of different approximations on accuracy and convergence.

  • 7.
    Abiri, Olufunminiyi
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Qin, Hao
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Comparison of Multiresolution Continuum Theory and Nonlocal Dame model for use in Simulation of Manufacutring Processes2016In: International Journal for Multiscale Computational Engineering, ISSN 1543-1649, Vol. 14, no 1, 81-94 p.Article in journal (Refereed)
    Abstract [en]

    Modelling and simulation of manufacturing processes may require the capability to account for localization behavior, often associated with damage/fracture. It may be unwanted localization indicating a failure in the process or, as in the case of machining and cutting, a wanted phenomenon to be controlled. The latter requires a higher accuracy regarding the modelling of the underlying physics, as well as the robustness of the simulation procedure. Two different approaches for achieving mesh-independent solutions are compared in this paper. They are the multiresolution continuum theory (MRCT) and nonlocal damage model. The MRCT theory is a general multilength-scale finite element formulation, while the nonlocal damage model is a specialized method using a weighted averaging of softening internal variables over a spatial neighborhood of the material point. Both approaches result in a converged finite element solution of the localization problem upon mesh refinement. This study compares the accuracy and robustness of their numerical schemes in implicit finite element codes for the plane strain shear deformation test case. Final remarks concerning ease of implementation of the methods in commercial finite element packages are also given.

  • 8.
    Abiri, Olufunminiyi
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials. University of Johannesburg, South Africa.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Wedberg, Dan
    Controlling Thermal Softening Using Non-Local Temperature Field in Modelling2016In: Journal of Machining and Forming Technologies, ISSN 1947-4369, Vol. 8, no 1-2, 13-28 p.Article in journal (Refereed)
    Abstract [en]

    One of the aims of this work is to show that thermal softening due to the reduced flow strength of a material with increasing temperature may cause chip serrations to form during machining. The other purpose, the main focus of the paper, is to demonstrate that a non-local temperature field can be used to control these serrations. The non-local temperature is a weighted average of the temperature field in the region surrounding an integration point. Its size is determined by a length scale. This length scale may be based on the physics of the process but is taken here as a regularization parameter.

  • 9.
    Adamopoulos, Stergios
    TEI Thessaly, Greece.
    Recovery and utilization of wood and rubber at the end of their lifespan to produce innovative products2014In: Development and Business Prospects in Thessaly by Symbiotic Utilization of Agricultural and Industrial Solid Waste to Produce Materials and Energy, November 24, Larissa, Greece, 2014Conference paper (Other academic)
  • 10.
    Adekunle, Kayode
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Synthesis of reactive soybean oils for use as thermoset resins in composites.2007Conference paper (Refereed)
  • 11.
    Adolfi, Sofia
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Slag inclusion formation during solidification of steel alloys and in cast iron2007Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis explores the formation of segregation and inclusions during solidification of steel and cast iron. A better understanding of the formation mechanism should result in decreasing fraction of defects during solidification of ingot and strand material.

    Density driven macrosegregation was studied both experimentally and theoretically to see the effect of channel segregation on the total segregation. Formation of these pencil-like segregations is due to natural convection in the solidifying metal caused by liquid enrichment of elements with lower density compared to the bulk. It is suggested to change the composition to compensate for this density difference.

    Inclusion precipitation can be finite by limitations in segregation. Saturated liquid is found in the last solidified areas, often between dendrites. Here the enrichment of the liquid is possible due to microsegregation. Meanwhile crystals form and solidify the elements with low solubility in the solid is pushed out in the remaining liquid. Soon the liquid is saturated to the level where spontaneous formation of inclusions occurs. Microstructure studies by aid of SEM and micro-probe measurements are analysed to find at what point during solidification process the inclusions start to form. In steel making this formation has a detrimental effect on the mechanical properties in contrary to the production of nodular cast iron where the inclusions have a beneficial effect on the graphite formation.

    Inoculation of cast iron aims at reaching higher number density of graphite nodules, nodule morphology modification and control of nodule distribution during solidification. Late precipitation of nucleation sites has shown to have a positive impact on preventing chill. To find the most potent inoculation agent different additives were tested. Special effort has been made to analyse the effect of oxides and sulphides as nucleation sites.

  • 12.
    Adolfsson, Robin
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Jönsson, Caroline
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Är SundaHus materialklassning kompatibel med Miljöbyggnads, BREEAMs och LEEDs materialkrav?: En studie om SundaHus miljöklassningar.2015Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    We live in a society where there is a shortage of housing and the demand for new and sustainable buildings is growing. The houses that are being built today are focused on being energy efficient to save resources. Something that is forgotten is the choice of materials to house constructions. Materials can affect nature and people from the cradle to the grave by for example material hazardous components. The certification systems Miljöbyggnad, BREEAM and LEED have been checked and their material criteria have been defined. Through a selection of construction materials taken from SundaHus a review has been made of these materials towards the certification systems´ criteria on materials to see if they are compatible. The minority of the criteria were reviewed to separate materials and could be verified in SundaHus. Almost all materials passed the criteria that could be used of Miljöbyggnad and BREEAM regardless of classification in SundaHus. None of the LEED criteria were compatible with SundaHus for separate materials. The fact that the worse classifications in SundaHus could pass the criteria that were reviewed indicates that the requirements in environmental certification systems are too low. Higher and more demands should be made on individual materials and the hazardous substances in them.

  • 13.
    Agde Tjernlund, Jessica
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Length-scale effects in yielding and damage development in polymer materials2005Licentiate thesis, comprehensive summary (Other scientific)
  • 14.
    Agde Tjernlund, Jessica
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Gamstedt, Kristofer
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Gudmundson, Peter
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Length-scale effects on damage development in tensile loading of glass-sphere filled epoxy2006In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 43, no 24, 7337-7357 p.Article in journal (Refereed)
    Abstract [en]

    Particle-reinforced polymers are widely used in load-carrying applications. The effect of particle size on damage development in the polymer is still relatively unexplored. In this study, the effect of glass-sphere size on the damage development in tensile loaded epoxy has been investigated. The diameter of the glass spheres ranged from approximately 0.5-50 mu m. The first type of damage observed was debonding at the sphere poles, which subsequently grew along the interface between the glass spheres and epoxy matrix. These cracks were observed to kink out into the matrix in the radial direction perpendicular to the applied load. The debonding stresses increased with decreasing sphere diameter, whereas the length to diameter ratio of the resulting matrix cracks increased with increasing sphere diameter. These effects could not be explained by elastic stress analysis and linear-elastic fracture mechanics. Possible explanations are that a thin interphase shell may form in the epoxy close to the glass spheres, and that there is a length-scale effect in the yield process which depends on the strain gradients. Cohesive fracture processes can contribute to the influence of sphere size on matrix-crack length. Better knowledge on these underlying size-dependent mechanisms that control damage development in polymers and polymer composites is useful in development of stronger materials. From a methodology point of view, the glass-sphere composite test can be used as an alternative technique (although still in a qualitative way) to hardness vs. indentation depth to quantify length-scale effects in inelastic deformation of polymers.

  • 15.
    Agde Tjernlund, Jessica
    et al.
    KTH, Superseded Departments, Solid Mechanics.
    Gamstedt, Kristofer
    KTH, Superseded Departments, Solid Mechanics.
    Xu, Zhi-Hui
    KTH, Superseded Departments, Materials Science and Engineering.
    Influence of molecular weight on strain-gradient yielding in polystyrene2004In: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 44, no 10, 1987-1997 p.Article in journal (Refereed)
    Abstract [en]

    Experimental observations have indicated that the presence of strain gradients has an influence on the inelastic behavior of polymers as well as in other materials such as ceramics and metals. The present study has experimentally quantified length-scale effects in inelastic deformations of the polymer material polystyrene (PS) with respect to the molecular length. The experimental technique that has been used is nano-indentation to various depths with a Berkovich indenter. The hardness has been calculated with the method by Oliver and Pharr, and also by direct measurements of the area from atomic force microscopy. The experiments showed that the length-scale effects in inelastic deformations exist in polystyrene at ambient conditions. The direct method gave a smaller hardness than the Oliver-Pharr method. It was also shown that the length-scale parameter according to Nix and Gao increases with increasing molecular weight. For high molecular weights above a critical value of entanglement, there was no pertinent increase in the length-scale parameter. The length-scale parameter for strain-gradient plasticity has a size of around 0.1 μm for polystyrene.

  • 16.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology.
    Hansson, Lars
    Luleå University of Technology.
    Morén, Tom
    Luleå University of Technology.
    Distribution of preservatives in thermally modified Scots pine and Norway spruce sapwood2013In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 47, no 3, 499-513 p.Article in journal (Refereed)
    Abstract [en]

    Studying the impregnation and distribution of oil-based preservative in dried wood is complicated as wood is a nonhomogeneous, hygroscopic and porous material, and especially of anisotropic nature. However, this study is important since it has influence on the durability of wood. To enhance the durability of thermally modified wood, a new method for preservative impregnation is introduced, avoiding the need for external pressure or vacuum. This article presents a study on preservative distribution in thermally treated Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) sapwood using computed tomography scanning, light microscopy, and scanning electron microscopy. Secondary treatment of thermally modified wood was performed on a laboratory scale by impregnation with two types of preservatives, viz. Elit Träskydd (Beckers) and pine tar (tar), to evaluate their distribution in the wood cells. Preservative solutions were impregnated in the wood using a simple and effective method. Samples were preheated to 170 °C in a drying oven and immediately submerged in preservative solutions for simultaneous impregnation and cooling. Tar penetration was found higher than Beckers, and their distribution decreased with increasing sample length. Owing to some anatomical properties, uptake of preservatives was low in spruce. Besides, dry-induced interstitial spaces, which are proven important flow paths for seasoned wood, were not observed in this species.

  • 17.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology, Sweden.
    Morén, Tom
    Luleå University of Technology, Sweden.
    Moisture properties of heat-treated Scots pine and Norway spruce sapwood impregnated with wood preservatives2012In: Wood and Fiber Science, ISSN 0735-6161, Vol. 44, no 1, 85-93 p.Article in journal (Refereed)
    Abstract [en]

    An experiment was conducted on commercially heat-treated (HT) Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] Karst.) sapwood collected from Ht Wood AB, Arvidsjaur, Sweden. Secondary treatment on HT wood was performed in laboratory scale by impregnating with water-repellent preservatives (a commercial one and pine tar) to evaluate their retention and different moisture-related properties. Preservative solutions were impregnated using a simple and effective method. Wood samples were heated at 170°C in a dry oven and were immediately immersed in preservative solutions. Considerable retention was observed in HT wood, particularly in pine. Moisture adsorption properties were measured after conditioning in a high-humidity environmental chamber (4°C and 84% RH). Experimental results showed that secondary treatment enhanced moisture excluding efficiencies by decreasing equilibrium moisture content, suggesting better hydrophobicity. Soaking test in water showed that antiswelling and water repellence efficiencies improved, especially in tar-treated wood. In addition, this type of treatment significantly decreased water absorption. It was also possible to decrease volumetric swellings. Thus, secondary treatment of HT wood with preservative, in particular with tar, improved dimensional stability and water repellency.

  • 18.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology.
    Sehlstedt-Persson, Margot
    Luleå University of Technology.
    Hansson, Lars
    Luleå University of Technology.
    Morén, Tom
    Luleå University of Technology.
    Evaluation of preservative distribution in thermally modified European aspen and birch boards using computed tomography and scanning electron microscopy2013In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 59, no 1, 57-66 p.Article in journal (Refereed)
    Abstract [en]

    The aim of this experiment was to impregnate thermally modified wood using an easy and cost-effective method. Industrially processed thermally modified European aspen (Populus tremula L.) and birch (Betula pubescens Ehrh.) were collected and secondarily treated at the laboratory scale with the preservatives tung oil, pine tar and Elit Träskydd (Beckers) using a simple and effective method. Preservative uptake and distribution in sample boards were evaluated using computed tomography (CT) and scanning electron microscopy (SEM) techniques. Preservative uptake and treatability in terms of void volume filled were found the highest in Beckers and the lowest in tung oil-treated samples. Thermally modified samples had lower treatability than their counterpart control samples. More structural changes after thermal modification, especially in birch, significantly reduced the preservative uptake and distribution. The differences of preservatives uptake near the end grain were high and then decreased near the mid position of the samples length as compared with similar type of wood sample. Non-destructive evaluation by CT scanning provided a very useful method to locate the preservative gradients throughout the sample length. SEM analysis enabled the visualization of the preservative deposits in wood cells at the microstructural level.

  • 19.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology.
    Sehlstedt-Persson, Margot
    Luleå University of Technology.
    Karlsson, Olov
    Luleå University of Technology.
    Morén, Tom
    Luleå University of Technology.
    Uneven distribution of preservative in kiln-dried sapwood lumber of Scots pine: Impact of wood structure and resin allocation2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, no 2, 251-258 p.Article in journal (Refereed)
    Abstract [en]

    Scots pine (Pinus sylvestris L.) sapwood lumber was collected after kiln drying and preservative treatment with Celcure AC 800 (a copper-amine wood preservative). Distribution of the preservative throughout the lumber was visually examined. Not all, but some samples showed specific localized areas without any preservative distribution throughout their entire length. Those samples were assessed further for anatomical properties, specifically in impregnated and unimpregnated areas. Additional study was conducted on the morphological nature and redistribution of lipophilic extractives using three different histochemical staining methods. Intrinsic wood properties – especially the frequency of axial resin canals and the percentage of canals blocked – were found to be responsible for the irregular distribution of the preservative. Furthermore, the inability to create continuous and frequent interstitial spaces due to the collapse of thin-walled ray cells throughout the lumber resulted in un-even distribution of preservatives. Staining techniques were useful to localize places with more or less abundance of extractives (e.g., fats) in impregnated and unimpregnated wood, which varied considerably. Histochemical observations revealed information pertaining to the kiln dry specific distribution and redistribution of extractives between the areas. Moreover, resin reallocation and modification in ray parenchyma and resin canals induced by kiln drying would be another reason for the impregnation anomalies.

  • 20.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology.
    Yang, Qian
    Luleå University of Technology.
    Sehlstedt-Persson, Margot
    Luleå University of Technology.
    Morén, Tom
    Luleå University of Technology.
    Accelerated Mold Test on Dried Pine Sapwood Boards: Impact of Contact Heat Treatment2013In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 33, no 3, 174-187 p.Article in journal (Refereed)
    Abstract [en]

    We test the hypothesis that the combination of kiln drying of double-stacked boards and contact heat treatment will reduce the susceptibility of treated boards to colonization by mold fungi. Winter-felled Scots pine (Pinus sylvestris L.) sapwood boards were double-stacked in an industrial kiln in ''sapwood out'' and ''sapwood in'' positions. Dried samples were then contact heat-treated using a hot press at three different temperatures (140°C, 170°C, and 200°C) for three different periods (1, 3, and 10 min). An accelerated mold test was performed in a climate chamber where naturally mold-infected samples were used as a source of mold inocula. Contact heat treatment degraded the saccharides that accumulated at dried surfaces, and reduced the mold growth. The threshold temperature and time for inhibiting mold growth were 170°C for 10 min. However, for industrial application, the most feasible combination of temperature and time would be 200°C for 3 min. We concluded that double stacking/contact heat treatment used is an environmentally friendly alternative to chemicals for reducing mold on Scots pine sapwood boards.

  • 21.
    Aid, Graham
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Management and Engineering, Environmental Technology and Management. Ragn-sells, Sweden.
    Kihl, Anders
    Ragn Sells AB.
    Driving forces and inhibitors of secondary stock extraction2014Conference paper (Other academic)
    Abstract [en]

    Even though it’s well known to mankind that our common resources are limited and that recycling is a key for a sustainable future; in reality we see few examples of true recycling where virgin raw material is substituted by waste. There are endless number of examples where waste is utilized to some extent without solving the core issue: reducing the need of extracting virgin raw materials. This article analyses some of the driving forces and inhibitors that explains why it’s so difficult establish secondary stock extraction although technology is available. The authors discuss and suggest possible ways for reducing the some of the main barriers.

  • 22. Ajay, A.
    et al.
    Raja, V. S.
    Sivakumar, G.
    Joshi, Shrikant V.
    Hot corrosion behavior of solution precursor and atmospheric plasma sprayed thermal barrier coatings2015In: Corrosion Science, Vol. 98, 271-279 p.Article in journal (Refereed)
    Abstract [en]

    Hot corrosion behavior of solution precursor plasma spray (SPPS) thermal barrier coating (TBC) in molten salt mixtures of 90wt.% Na<inf>2</inf>SO<inf>4</inf>+5wt.% V<inf>2</inf>O<inf>5</inf>+5wt.% NaCl and 50wt.% Na<inf>2</inf>SO<inf>4</inf>+50wt.% V<inf>2</inf>O<inf>5</inf> at 900°C is compared vis-à-vis atmospheric plasma spray (APS) coating. APS TBCs show better hot corrosion resistance than SPPS TBCs in both the salt mixtures. The vertical cracks in SPPS coatings, meant for strain tolerance and high thermal cycling life, serve as channels for transporting salts across the coating to bond coat/top coat interface and accelerate failure. © 2015 Elsevier Ltd.

  • 23.
    Akbarnejad, Shahin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Investigation on static strength of welded joints2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Although high strength steels represent yield strength up to 1300 MPa, welded structures reveal lowerstrength values. The strongest commercially available electrode provides the yield strength of about900 MPa. Therefore, in welded steels with strength above this type of filler metal, achieving anacceptable global strength is a crucial issue.

    In this master thesis, affects of different welding procedures on static strength of welded jointsof Weldox 960 and Weldox 1100 steels, were studied. These steels are produced by SSAB inOxelösund. Meanwhile, finite element method analyses were applied in order to investigatethe static strength behavior of such weldments under uniaxial tension.

    The welding parameters which were selected as variables are:

    •  Heat input
    • Weld joint geometry
    • Filler metal

    When weld metal is undermatching in strength levels than the base material, by applyingtension the soft weld metal begins to deform before parent metal. At that point thedeformation of resulted soft zone, including the weld metal and the heat affected zone, ishindered by high strength parent metal. Thus, uniaxial stress caused by uniaxial load isconverted to multiaxial stress. This conversion in tension results in increase in the staticstrength of weldment. The increase in strength is emphasized by increase in the width of thewelded joint while the thickness of the plate is kept as constant.

    After experiments and performing FEM studies, it was revealed that the static strength ofWeldox 960 welded joints approaches towards the tensile strength of parent metal by increasein the width of the weldment. In Weldox 1100 joints; a slight increase in tensile properties ofthe weldments, when the width of the sample increases, was observed.

  • 24.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ceramic reinforced high modulus steel composites: processing, microstructure and properties2014In: Canadian metallurgical quarterly, ISSN 0008-4433, E-ISSN 1879-1395, Vol. 53, no 3, 253-263 p.Article in journal (Refereed)
    Abstract [en]

    Ceramic reinforced steel matrix composites are materials for automotive, aerospace, wear and cutting applications. Such metal matrix composites (MMCs) combine attractive physical, mechanical and wear properties with ease of fabrication and low cost. The review focuses on the current state of the art of producing these metal matrix composites, ceramics reinforcements, composition of steel matrix, microstructure evolution and parameters influencing the mechanical and wear properties. Processing methods to fabricate ceramic reinforced steel matrix composites are discussed to produce these composites with low number of defects, homogeneous microstructure and high mechanical and wear performance. The influence of chemical nature of ceramic reinforcements and composition of steel matrix on the microstructure, mechanical and wear properties is presented. The strengthening mechanisms and parameters controlling wear performance of steel MMCs are described as a function of the content of ceramic reinforcements, microstructural design and structure of the steel matrix. Keeping in view the stability of ceramics in steels, suitable ceramic reinforcements and steel matrix materials are discussed. Moreover, the importance of microstructure and interface between ceramic reinforcement and steel matrix in controlling the mechanical properties of steel MMCs is highlighted. The review identifies area of research for development to fully appreciate and tailor the properties of these industrially important composites.

  • 25.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Structuring gas adsorbents by processing of porous powders2014Conference paper (Refereed)
  • 26.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Structuring of Aluminophosphates Monoliths for Carbon Capture2015Conference paper (Refereed)
  • 27.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Structuring of Nanoporous Powders into Hierarchically Porous Nanostructured Adsorbents for Clean Energy2016Conference paper (Refereed)
  • 28.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Structuring of nanoporous powders into hierarchically porous nanostructured adsorbents for decarbunization2015Conference paper (Refereed)
  • 29.
    Akhtar, Farid
    Stockholm University.
    Stainless Steel Polymer Composites2012In: Wiley Encyclopedia of Composites, John Wiley & Sons, 2012Chapter in book (Refereed)
    Abstract [en]

    In electronic, automotive, medical, and aerospace industries, electrostatic discharge (ESD) control and electromagnetic interference (EMI) shielding are important design considerations. Conductive polymer composites are well researched and commercially available materials for ESD control and EMI shielding. Several kinds of conductive fillers are incorporated in the form of particulates and fibers in polymer matrix. A comparison between various conductive fillers in polymer matrix is presented. Stainless steel fibers as conductive filler for polymer matrix offer several advantages. Polymer composites show resistivities in the range of 103−106 Ω/sq at a volume fraction as low as 0.75 vol% of stainless steel fibers. The effect of filler size, shape of the filler, critical volume fraction, and effect of polymer matrix on the ESD control/EMI shielding properties of the stainless steel-reinforced conductive polymer composite is discussed. Important parameters are described to obtain effective ESD control and EMI shielding using stainless fiber polymer matrix composites. Several reported stainless steel-reinforced polymer composites are summarized and their effectiveness for ESD control and EMI shielding is compared

  • 30.
    Akhtar, Farid
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Structuring of porous powders for gas separation applications2013Conference paper (Other academic)
  • 31.
    Akhtar, Farid
    Department of Materials and Environmental Chemistry, Stockholm University.
    Structured adsorbents with High CO2 over N2 selectivity and CO2 uptake capacity2012In: 2012 AIChE annual meeting: David L. Lawrence Convention Center, Pittsburgh, PA, October 28-November 2, 2012 : conference proceedings., New York: American Institute of Chemical Engineers, 2012Conference paper (Refereed)
    Abstract [en]

    Structured adsorbents with high CO2 adsorption capacity, CO2 over N2 selectivity and rapid adsorption and desorption kinetics are ideal for CO2 capture from power-plant flue gas at a low cost. We report here binder-free zeolite monoliths with high CO2 over N2 selectivity (> 500) and uptake capacity (4mmolg-1) at 298 K and 101 kPa. Binder-free zeolite monoliths were consolidated by a rapid and facile processing approach called pulse current processing (PCP) from partially K exchanged NaA powders. The pore widow size of NaA was optimized by partially exchanging Na with K cations to achieve a high CO2 over N2 selectivity while maintaining a high CO2 uptake capacity. The CO2 uptake from binary mixtures of 0.10CO2-0.90N2 was obtained from the single component CO2 and N2 adsorption isotherms by applying Ideal adsorption solution (IAS) and Fast IAS theories. The binder-free adsorbents with an optimum degree of ion exchange display extraordinarily high CO2 over N2 selectivity and high CO2 uptake, together with a rapid CO2 adsorption and desorption kinetics and high mechanical stability. The performance of the new adsorbent has been compared with other potential candidates for efficient swing adsorption processes by a figure of merit. Key words: CO2 Capture; Zeolite monoliths; Pulse current processing; Selectivity; Adsorption; Ideal adsorbed solution (IAS) theory

  • 32.
    Akhtar, Farid
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Zeolite adsorbents for gas separation applications2013Conference paper (Refereed)
  • 33.
    Akhtar, Farid
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Structuring of porous powders into hierarchically porous adsorbents2013Conference paper (Refereed)
  • 34.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hierarchical zeolites for carbon capture2014Patent (Other (popular science, discussion, etc.))
  • 35.
    Akhtar, Farid
    et al.
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Andersson, Linnéa
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Keshavarzi, Neda
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Colloidal processing and CO 2 capture performance of sacrificially templated zeolite monoliths2012In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 97, 289-296 p.Article in journal (Refereed)
    Abstract [en]

    Sacrificial templating of suspension cast and subsequently thermally treated zeolite monoliths with glassy carbon spheres and fibers yielded zeolite 13X and silicalite-1 monoliths with macroporosities up to 50 vol%. Homogeneous distribution of the macroporosity in hierarchically porous monoliths was obtained by tailoring the surface chemistry of the carbon particles by polyelectrolyte-assisted adsorption of zeolite particles. The effect of amount of kaolin binder and temperature for the thermal treatment on the monoliths strength, surface area and CO2 uptake was studied by diametral compression tests, electron microscopy, X-ray diffraction and gas adsorption. Cyclic adsorption and regeneration measurements showed that zeolite 13X monoliths display a high CO2 uptake while the silicalite-1 monoliths could be regenerated with a relatively low energy penalty.

  • 36.
    Akhtar, Farid
    et al.
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Andersson, Linnéa
    School of Chemical, Biological and Environmental Engineering, Oregon State University.
    Ogunwumi, Steven
    Crystalline Materials Research, Corning Incorporated.
    Hedin, Niklas
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Structuring adsorbents and catalysts by processing of porous powders2014In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 34, no 7, 1643-1666 p.Article in journal (Refereed)
    Abstract [en]

    Microporous materials such as zeolites, metal organic frameworks, activated carbons and aluminum phosphates are suitable for catalysis and separation applications. These high surface area materials are invariably produced in particulate forms and need to be transformed into hierarchically porous structures for high performance adsorbents or catalysts. Structuring of porous powders enables an optimized structure with high mass transfer, low pressure drop, good heat management, and high mechanical and chemical stability. The requirements and important properties of hierarchically porous structures are reviewed with a focus on applications in gas separation and catalysis. Versatile powder processing routes to process porous powders into hierarchically porous structures like extrusion, coatings of scaffolds and honeycombs, colloidal processing and direct casting, and sacrificial approaches are presented and discussed. The use and limitations of the use of inorganic binders for increasing the mechanical strength is reviewed, and the most important binder systems, e.g. clays and silica, are described in detail. Recent advances to produce binder-free and complex shaped hierarchically porous monoliths are described and their performance is compared with traditional binder-containing structured adsorbents. Needs related to better thermal management and improved kinetics and volume efficiency are discussed and an outlook on future research is also given.

  • 37.
    Akhtar, Farid
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University.
    Ogunwumi, Steven
    Laminates for rapid CO2 capture from gas mixtures2013Patent (Other (popular science, discussion, etc.))
  • 38.
    Akhtar, Farid
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Hedin, Niklas
    Department of Materials and Environmental Chemistry, Stockholm University.
    Bergström, Lennart M.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Zeolite adsorbents with high CO2-over-N2 selectivity and high capacity2012Conference paper (Refereed)
  • 39.
    Akhtar, Farid
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Keshavarzi, Neda
    Department of Materials and Environmental Chemistry, Stockholm University.
    Shakarova, Dilshod
    Department of Materials and Environmental Chemistry, Stockholm University.
    Cheung, Ocean
    Department of Materials and Environmental Chemistry, Stockholm University.
    Hedin, Niklas
    Department of Materials and Environmental Chemistry, Stockholm University.
    Bergström, L.M.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Aluminophosphate monoliths with high CO2-over-N2 selectivity and CO2 capture capacity2014In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 99, 55877-55883 p.Article in journal (Refereed)
    Abstract [en]

    Monoliths of microporous aluminophosphates (AlPO4-17 and AlPO4-53) were structured by binder-free pulsed current processing. Such monoliths could be important for carbon capture from flue gas. The AlPO4-17 and AlPO4-53 monoliths exhibited a tensile strength of 1.0 MPa and a CO2 adsorption capacity of 2.5 mmol g-1 and 1.6 mmol g-1, respectively at 101 kPa and 0°C. Analyses of single component CO2 and N2 adsorption data indicated that the AlPO4-53 monoliths had an extraordinarily high CO2-over-N2 selectivity from a binary gas mixture of 15 mol% CO2 and 85 mol% N2. The estimated CO2 capture capacity of AlPO4-17 and AlPO4-53 monoliths in a typical pressure swing adsorption (PSA) process at 20°C was higher than that of the commonly used zeolite 13X granules. Under cyclic sorption conditions, AlPO4-17 and AlPO4-53 monoliths were regenerated by lowering the pressure of CO2. Regeneration was done without application of heat, which would regenerate them to their full capacity for CO2 adsorption.

  • 40.
    Akhtar, Farid
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Kocjan, Andraz
    The hydrolysis of AlN powder: powerful tool in advanced materials engineering2014Conference paper (Refereed)
  • 41.
    Akhtar, Farid
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Liu, Qingling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Bergstroem, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Erratum: Strong and binder free structured zeolite sorbents with very high CO2-over-N-2 selectivities and high capacities to adsorb CO2 rapidly (vol 5, pg 7664, 2012)2012In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 5, no 12, 9947- p.Article in journal (Refereed)
  • 42.
    Akhtar, Farid
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Liu, Qingling
    Department of Materials and Environmental Chemistry, Stockholm University.
    Hedin, Niklas
    Department of Materials and Environmental Chemistry, Stockholm University.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University.
    Strong and binder free structured zeolite sorbents with very high CO 2-over-N 2 selectivities and high capacities to adsorb CO 2 rapidly2012In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 5, no 6, 7664-7673 p.Article in journal (Refereed)
    Abstract [en]

    Mechanically strong monoliths of zeolite NaKA with a hierarchy of pores displayed very high CO2-over-N2 selectivity. The zeolite monoliths were produced by pulsed current processing (PCP) without the use of added binders and with a preserved microporous crystal structure. Adsorption isotherms of CO2 and N2 were determined and used to predict the co-adsorption of CO2 and N2 using ideal adsorbed solution theory (IAST). The IAST predictions showed that monolithic adsorbents of NaKA could reach an extraordinarily high CO2-over-N2 selectivity in a binary mixture with a composition similar to flue gas (15 mol% CO2 and 85 mol% N2 at 25 °C and 101 kPa). Structured NaKA monoliths with a K+ content of 9.9 at% combined a CO2-over-N2 selectivity of >1100 with a high CO2 adsorption capacity (4 mmol g−1) and a fast adsorption kinetics (on the order of one minute). Estimates of a figure of merit (F) based on IAST CO2-over-N2 selectivity, and time-dependent CO2 uptake capacity, suggest that PCP-produced structured NaKA with a K+ content of 9.9 at% offers a performance far superior to 13X adsorbents, in particular at short cycle times.

  • 43.
    Akhtar, Farid
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Liu, Qingling
    Hedin, Niklas
    Department of Materials and Environmental Chemistry, Stockholm University.
    Bergström, Lennart M.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Structured zeolite adsorbents with very high CO2-over-N2 selectivity and high capacity.2012Conference paper (Refereed)
  • 44.
    Akhtar, Farid
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Shakarova, Dilshod
    Department of Materials and Environmental Chemistry, Stockholm University.
    Ojuva, Arto
    Department of Materials and Environmental Chemistry, Stockholm University.
    Bergström, Lennart M.
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, Department of Materials and Environmental Chemistry, Stockholm University.
    Structuring of AlPOs and zeolite powders into hierarchically porous CO2 adsorbents2014Conference paper (Refereed)
    Abstract [en]

    The use of porous materials in industrially important gas separation and purification applications, e.g. CO2 separation from flue gas and purification of biogas require that the porous material is assembled into mechanically strong and hierarchically porous macroscopic structures. Hierarchically porous structured monoliths[1-2] and laminates[3] have been reported with high performance for CO2 separation from N2. Such structured monoliths and laminates with tailored porosity at various length scales combined high volumetric efficiency, good mass and heat transfer, rapid adsorption/desorption kinetics and structural integrity[1-3]. Here, we demonstrate a binder-less approach[4,5] to consolidate 8-ring window zeolite and aluminophosphate (AlPO4’s) powders into mechanically strong monoliths with a high CO2 uptake capacity and CO2-over-N2 selectivity, and a rapid adsorption and release kinetics. Adsorption isotherms of CO2 and N2 were used to predict the co-adsorption of CO2 and N2 using ideal adsorbed solution theory (IAST). The IAST predictions showed that monolithic zeolite adsorbents of partially K exchanged NaA could reach an extraordinarily high CO2-over-N2 selectivity in a binary mixture with a composition similar to flue gas[1]. Furthermore, zeolite monoliths showed high tensile strength of 2.2 MPa. AlPO-17 and AlPO-53 monoliths were consolidated by the binder-less process with a tensile strength over 1 MPa. AlPO-17 monoliths showed high CO2 adsorption capacity while AlPO-53 exhibited high CO2-over-N2 selectivity. Cyclic CO2 adsorption tests showed that AlPO4 monoliths required less energy for regeneration compared to zeolite and could be regenerated to their full capacity at low pressures

  • 45.
    Akhtar, Farid
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Sjöberg, Erik
    Korelskiy, Danil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rayson, Mark
    Department of Chemistry, The University of Surrey, Guildford.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University.
    Preparation of graded silicalite-1 substrates for all-zeolite membranes with excellent CO2/H2 separation performance2015In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 493, 206-211 p.Article in journal (Refereed)
    Abstract [en]

    raded silicalite-1 substrates with a high gas permeability and low surface roughness have been produced by pulsed current processing of a thin coating of a submicron silicalite-1 powder onto a powder body of coarser silicalite-1 crystals. Thin zeolite films have been hydrothermally grown onto the graded silicalite-1 support and the all-zeolite membranes display an excellent CO2/H2 separation factor of 12 at 0 °C and a CO2 permeance of 21.3×10-7 mol m-2 s-1 Pa-1 for an equimolar CO2/H2 feed at 505 kPa and 101 kPa helium sweep gas. Thermal cracking estimates based on calculated surface energies and measured thermal expansion coefficients suggest that all-zeolite membranes with a minimal thermal expansion mismatch between the graded substrate and the zeolite film should remain crack-free during thermal cycling and the critical calcination step.

  • 46.
    Akhtar, Suleman
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Material Factors Influencing Crack Initiation and Propagation During Seamless Tube Rolling of Low Carbon Steel Grades2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Lower hot ductility can lead to cracks in steels. Hot ductility is affected by grain boundary sliding at temperatures higher than A3 and by the presence of thin films of ferrite at grain boundaries at temperatures lower than A3. Grain boundary sliding might occur because of the segregation of harmful elements like sulphur, etc. While thin films of ferrite at grain boundaries lead to easy interlinking of MnS precipitates at grain boundaries and ultimately may cause cracks in the material. Also, stress concentration is higher at thin ferrite films at grain boundaries which for being softer as compared to austenite matrix lead to cracks in the material. Elongated  (Fe, Mn)S sulphides are more detrimental for the hot ductility as compared to round ones. Higher aspect ratio of the precipitates is also dependent on sulphur content. The higher the sulphur content, the higher would be the hot ductility. Silicon, being a ferrite stabilizer, causes the volume fraction of ferrite to increase which improves the hot ductility of the steels. Hot ductility can be improved by adding Boron that segregates to grain boundaries instead of sulphur improving the strength of grain boundaries. Increasing silicon content can lead to higher volume fraction of ferrite thus improving ductility because stress would uniformly be distributed across the grain and not merely on the grain boundaries. Apart from that, decreasing the solution treatment temperature and increasing holding time on solution treatment temperature can lead to lower dissolved content of sulphur and coarser MnS precipitates hence improving hot ductility. 

  • 47.
    Akhtar, Sultan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Strömberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strømme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    TEM investigations of attachment of functionalized magnetic nanoparticles to DNA-coils acting as a biosensor2010In: Scandem 2010, Stockholm, Sweden, June 8-11, 2010Conference paper (Refereed)
  • 48.
    Albertini, Gianni
    et al.
    Dipartimento di Scienze dei Materiali e della Terra, Universita, Ancona, Italy.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials . Linköping University, The Institute of Technology.
    Manescu, Adrian
    Instituto di Scienze Fisiche, Universita, Ancona, Italy.
    Ponzetti, Araldo
    NUOVA M.A.I.P SpA, Viale Cavalotti n 30, Jesi, Italy.
    Neutron Diffraction Measurement of Residual Stress in a centrifugal Bowl of Duplex Steel2001In: Journal of Neutron Research, ISSN 1023-8166, Vol. 9, 305-312 p.Article in journal (Refereed)
  • 49. Alemani, Mattia
    et al.
    Gialanella, S.
    Straffelini, G.
    Ciudin, R.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Perricone, G.
    Metinoz, I.
    Dry sliding of a low steel friction material against cast iron at different loads: Characterization of the friction layer and wear debris2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 376-377, 1450-1459 p.Article in journal (Refereed)
    Abstract [en]

    Pin-on-disc testing was used to investigate the sliding behavior and the wear products of a low-steel friction material against a cast iron disc at different applied loads, to investigate the effect of the temperature rise induced by frictional heating. The testing rig was operated in a clean chamber with a purified incoming air flux. The outgoing flux carries the wear particles to an impactor that counted and sorted them by average diameter and weight. At increasing applied loads, corresponding to a proportional increase of the pin-disc contact temperature, the coverage of both the pin and disc surface by a friction layer was found to increase too. The relevant X-Ray diffraction patterns revealed the presence of a large amount of graphite and different compounds originating from the friction material and from the counterface disc, mainly iron oxides, as concerns this latter. After the test at the lowest investigated load, i.e., 1 kg, the disc worn surface exhibited abrasive grooves and a discontinuous friction layer mainly made of compacted iron oxide particles. After the test at higher loads, i.e., 5 and 7 kg, the disc surface was covered by a compact friction layer. As concerns the friction layer on the pins, most of the ingredients from the friction material were detected, in association with the iron oxides from the disc. These results can be interpreted in terms of the temperature stability range of the phenolic resin used as a binder of the friction material. The characterization of the collected airborne wear debris showed that the particles produced by the low temperature (i.e., low load) test were mostly equiaxed; whereas those produced by the high temperature (i.e., high loads) tests, predominantly displayed a plate-like morphology. The mechanisms of their formation in relation to the characteristics of the friction layers are illustrated and discussed.

  • 50.
    Alfredsson, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Nyberg, Harald
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Hogmark, Sture
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jacobson, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Tribological conditions of curling - the ultimate friction sport?2011In: 18th International Conference on Wear of Materials, Philadelphia, USA, April 3-7, 2011, 2011Conference paper (Refereed)
    Abstract [en]

    Curling is an Olympic winter sport in which 8 players forming two teams slide stones across a sheet of ice towards a target area. The two teams have eight stones each and take turns to slide the stones over to the target area, some 28 m away from the release line. After being released, the stone is only affected by the sliding friction. However, this friction may be somewhat modified by sweeping the ice just in front of the sliding stone, using special curling brooms. Further, the trajectory of the stone becomes slightly curled. By slowly turning the stone clockwise when it is released, it will turn to the right, and vice versa. The best team in each round of 16 stones score one point for each stone resting closer to the target than the best stone from the opponent team.

    The game makes up a very interesting tribological system, presenting a number of challenging problems. These problems include understanding exactly:

    • what determines the level of friction, and how it is affected by the sweeping,
    • how the roughness of the stone influences the friction, and how the sliding surface should best be prepared to give a stable and repeatable friction,
    • how the intentionally bumpy "pebbled" ice structure influences the friction,
    • the size and distribution of the contact spots between the rough stone and the pebbled ice,
    • the mechanism causing the curl of the stone - "Why does the stone curl?".

    This poster is based on an experimental project, and presents this very intriguing tribological system. It offers some ready explanations and challenges the visiting tribologists to contribute their insights.

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