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  • 1. Bressi, Sara
    et al.
    Dumont, A. G.
    Partl, Manfred
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. Carleton Univ, Ottawa, Canada.
    An advanced methodology for the mix design optimization of hot mix asphalt2016In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 98, p. 174-185Article in journal (Refereed)
    Abstract [en]

    The bitumen quantity to add to asphalt mixtures depends on the surfaces of aggregates and filler to be coated. The formulas currently available in the literature have limitations such as considering all the fillers with the same specific surface or the aggregates with spherical or cubical shapes. This paper aims to define an analytical approach for the determination of the optimal dosage of bitumen in HMA proposing new methodologies to go a step further in the resolution of the above mentioned approximations. Indeed, new surface area factors were calculated to determine the aggregates surface considering their real shapes and volumes. Afterwards, the authors proposed a detailed characterization of two types of fillers and the critical filler concentration, introduced by Faheem and Bahia, was used to calculate the minimum amount of bitumen for maintaining the mastic in a diluted state and filling the voids in the mixtures. Finally, a verification of the formula developed was carried out with specific laboratory tests. These results allow the challenge of revising the method of calculating the specific surface of the aggregates and filler to be addressed with the final goal to include them in a new mix design optimization for HMA. 

  • 2.
    Carosio, Federico
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Cuttica, Fabio
    Medina, Lilian
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Clay nanopaper as multifunctional brick and mortar fire protection coating: Wood case study2016In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 93, p. 357-363Article in journal (Refereed)
    Abstract [en]

    Abstract Wood is one of the most sustainable, esthetically pleasing and environmentally benign engineering materials, and is often used in structures found in buildings. Unfortunately, the fire hazards related to wood are limiting its application. The use of transparent cellulose nanofiber (CNF)/clay nanocomposites, with unique brick-and-mortar structure, is proposed as a sustainable and efficient fire protection coating for wood. Fire performance was assessed by cone calorimetry. When exposed to the typical 35 kW/m2 heat flux of developing fires, the time to ignition of coated wood samples increased up to about 4 1/2 min, while the maximum average rate of heat emission (MARHE) was decreased by 46% thus significantly reducing the potential fire threat from wood structures.

  • 3.
    Celma Cervera, Carlos
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Partl, Manfred N.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. bEMPA Swiss Federal Laboratories for Materials Testing and Research, Switzerland.
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Contact-induced deformation and damage of rocks used in pavement materials2017In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 133, p. 255-265Article in journal (Refereed)
    Abstract [en]

    Performance of stone-based construction materials, such as asphalt and unbound aggregate mixtures is defined to a great extent by the mechanics of the stone-to-stone interactions. Accordingly, the Discrete Element Method (DEM) is gaining popularity as a modelling tool to investigate the mechanical behavior of these materials. Contact and failure laws defining particles force-displacement relationships and the propensity of particles to break are crucial inputs for the DEM simulations. The present study aims at providing an experimental contact mechanics basis for the development of physically based stone-to-stone interaction laws. The attention is focused on investigating stone's force-displacement relationship and damage characteristics at pure normal loading for two stone materials used by the road industry. Experiments are performed at spherical contact profiles for cyclic and monotonically increasing loads. The emphasis lies on the evolution of contact compliance and accumulation of contact induced damage. The effect of surface roughness on the materials response is examined through comparative experiments performed on the specimens with different roughness values. Optical and environmental scanning electron microscopy (ESEM) observations of the contact induced damage at the material surface are presented and discussed in the context of contact mechanics. The implications of the reported experimental findings on the development of mechanics based contact and failure laws for the DEM modelling of stone-based construction materials are discussed.

  • 4.
    Dai, J. H.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Harbin Inst Technol Weihai, Sch Mat Sci & Engn, 2 West Wenhua Rd, Weihai 264209, Peoples R China..
    Li, Wei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Song, Y.
    Harbin Inst Technol Weihai, Sch Mat Sci & Engn, 2 West Wenhua Rd, Weihai 264209, Peoples R China..
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala Univ, Dept Phys & Astron, Div Mat Theory, Box 516, SE-75120 Uppsala, Sweden.;Wigner Res Ctr Phys, Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary..
    Theoretical investigation of the phase stability and elastic properties of TiZrHfNb-based high entropy alloys2019In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 182, article id UNSP 108033Article in journal (Refereed)
    Abstract [en]

    First principles calculations are performed to study the effects of alloying elements (X = Al, Si, Sc, V, Cr, Mn, Cu, Zn, Y. Mo, Ta, W and Re) on the phase stability and elastic properties of TiZrHfNb refractory high entropy alloys. Both equimolar and non-equimolar alloys are considered. It is shown that the calculated lattice parameters, phase stability and elastic moduli of equimolar TiZrHfNbX are consistent with the available experimental and theoretical results. The substitutions of alloying elements at Ti, Zr, and Hf sites with various contents show similar effects on the phase stability and elastic properties of the TiZrHINb-based alloys. The substitutions on Nb site are found to generally decrease the stability of body centered cubic phase. Close connections between the charge densities at the Wigner-Seitz cell boundary and the bulk moduli of TiZrHfNb-based alloys are found. The present results provide a quantitative model for exploring the phase stability and elastic properties of TiZrHINb-based alloys from the electronic structure viewpoint. Elsevier Ltd.

  • 5. Davydova, A.
    et al.
    Eriksson, J.
    Chen, R.
    Rudisch, K.
    Persson, Clas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. University of Oslo, Norway.
    Scragg, J. J. S.
    Thio-olivine Mn2SiS4 thin films by reactive magnetron sputtering: Structural and optical properties with insights from first principles calculations2018In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 152, p. 110-118Article in journal (Refereed)
    Abstract [en]

    Thio-olivines such as (Fe,Mn)2(Si,Ge)S4 have been proposed as candidate earth-abundant materials for single and multi-junction solar cells. In this work we present the first investigation of Mn2SiS4thin films prepared by reactive magnetron sputtering deposition, using a composition grading approach. Precursor instability in ambient conditions is observed, revealing the oxidation/hydrolysis of Si–S bonds from the as-deposited film as a blocking mechanism for the ternary compound formation. Structural, morphological and optical properties of the annealed Mn2SiS4 films are reported for the first time. Resulting Mn2SiS4 films have orthorhombic Pnma structure and are polycrystalline. Raman active modes at 325 nm excitation are observed at 262, 320, 400 and 464 cm−1. From room temperature photoluminescence at 532 nm excitation the band gap is estimated to be about 1.9 eV, but a high optical absorption coefficient of >104 cm−1 was only obtained at E > 2.8 eV. First principles calculations are used for better understanding of opto-electronic properties. From the calculations, Mn2SiS4 is suggested to have a band gap of about 1.73–1.86 eV depending on the magnetic configuration of Mn and slight indirect nature. The slow absorption onset is interpreted by strong anisotropy due to one of the components of the dielectric function.

  • 6.
    Espinoza-Cuadra, J.
    et al.
    CONACyT-México, Av. Insurgentes Sur 1582, Col. Crédito Constructor Del. Benito Juárez, C.P. 03940, Mexico, D.F., Mexico.
    Gallegos-Acevedo, P.
    Universidad Tecnológica de la Mixteca, Carretera a Acatlima Km. 2.5 Huajuapán de León, C.P. 69000, Oaxaca, Mexico.
    Mancha-Molinar, H.
    Research and Development Department, CIFUNSA, Blvd. Isidro López Z. #4003, Zona Industrial Saltillo, C.P. 25230, Coahuila, Mexico.
    Picado, Apolinar
    Natl Univ Engn UNI, Fac Chem Engn.
    Effect of Sr and solidification conditions on characteristics of intermetallic in Al–Si 319 industrial alloys2010In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 31, no 1, p. 343-356Article in journal (Refereed)
    Abstract [en]

    An experimental study was carried out to determine the effect of strontium (Sr) on the characteristic of intermetallic phases, particularly the Al5FeSi phase which present morphology of platelets or needle-like. The results showed that within the range of variables studied, the modification process caused the disappearance of the needles and only occur the precipitation of phase α (chinese script-like). Refinement of the intermetallic phases occurs in conjunction with the refinement in grain size. Both parameters depend strongly on local cooling rate (T), temperature gradient (G) and apparent rate of solidification front (V). In the case of equiaxed structures the refinement of grain size and intermetallic occurs with increasing local cooling rate and temperature gradient and decrease the apparent rate of solidification front. In the case of columnar structures, refinement of grains and intermetallic requires the increase in values of the three variables indicated. Moreover, the addition of Sr resulted in the modification of silicon eutectic, as noted in others research works.

  • 7.
    Huang, Shuo
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Li, Wei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Li, Xiaoqing
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Schönecker, Stephan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Bergqvist, Lars
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Holmström, E.
    Varga, L. K.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Wigner Research Centre for Physics, Hungary; Uppsala University, Sweden.
    Mechanism of magnetic transition in FeCrCoNi-based high entropy alloys2016In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 103, p. 71-74Article in journal (Refereed)
    Abstract [en]

    First-principles alloy theory and Monte-Carlo simulations are performed to investigate the magnetic properties of FeCrCoNiAlx high entropy alloys. Results show that face-centered-cubic (fcc) and body-centered-cubic (bcc) structures possess significantly different magnetic behaviors uncovering that the alloy's Curie temperature is controlled by the stability of the Al-induced single phase or fcc-bcc dual-phase. We show that the appearance of the bcc phase with increasing Al content brings about the observed transition from the paramagnetic state for FeCrCoNi to the ferromagnetic state for FeCrCoNiAl at room-temperature. Similar mechanism is predicted to give rise to room-temperature ferromagnetism in FeCrCoNiGa high entropy alloy.

  • 8.
    Larsson, Per-Lennart
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Blanchard, Pierre
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    On the invariance of hardness at sharp indention of materials with general biaxial residual stress fields2013In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 52, p. 602-608Article in journal (Refereed)
    Abstract [en]

    In recent years, the influence from residual surface stresses on the global indentation properties, i.e. hardness and size of the contact area, have been studied quite frequently. The investigations presented have been based on experimental, theoretical and numerical methods and for one thing, the invariance of hardness in the case of residual equi-biaxial surface stresses, has been well-established. In the more general case, when the principal surface stresses are not necessarily equi-biaxial, corresponding results are more scattered and it is therefore the aim of the present study to remedy this shortcoming. In doing so, the problem is presently attacked using numerical methods and in particular the finite element method (FEM) is relied upon. Classical Mises elastoplastic material behavior is assumed throughout the investigation which is restricted, for clarity but not for necessity, to sharp cone indentation. The results confirm the invariance of hardness also for general stress fields when the deformation in the contact region is dominated by plastic deformation.

  • 9.
    Li, Xiaojie
    et al.
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Electron & Ion Beams, Dalian 116024, Peoples R China.;KTH Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Li, Xiaoqing
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Schönecker, Stephan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Li, Ruihuan
    Changzhou Vocat Inst Mechatron Technol, Inst Mold Technol, Changzhou 213164, Peoples R China..
    Zhao, Jijun
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Electron & Ion Beams, Dalian 116024, Peoples R China..
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala Univ, Div Mat Theory, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden.;Res Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary..
    Understanding the mechanical properties of reduced activation steels2018In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 146, p. 260-272Article in journal (Refereed)
    Abstract [en]

    Reduced activation ferritic/martensitic (RAFM) steels are structural materials with potential application in Generation-IV fission and fusion reactors. We use density-functional theory to scrutinize the micro-mechanical properties of the main alloy phases of three RAFM steels based on the body-centered cubic FeCrWVMn solid solution. We assess the lattice parameters and elastic properties of ferromagnetic alpha-Fe and Fe91Cr9, which are the main building blocks of the RAFM steels, and present a detailed analysis of the calculated alloying effects of V, Cr, Mn, and W on the mechanical properties of Fe91Cr9. The composition dependence of the elastic parameters is decomposed into electronic and volumetric contributions and studied for alloying levels that cover the typical intervals in RAFM steels. A linear superposition of the individual solute effects on the properties of Fe91Cr9 is shown to provide an excellent approximation for the ab initio values obtained for the RAFM steels. The intrinsic ductility is evaluated through Rice's phenomenological theory using the surface and unstable stacking fault energies, and the predictions are contrasted with those obtained by empirical criteria. Alloying with V or W is found to enhance the ductility, whereas additional Cr or Mn turns the RAFM base alloys more brittle.

  • 10.
    Linvill, Eric
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.). KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Larsson, Per A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Östlund, Sören
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.). KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Advanced three-dimensional paper structures: Mechanical characterization and forming of sheets made from modified cellulose fibers2017In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 128, p. 231-240Article in journal (Refereed)
    Abstract [en]

    Cellulose partially converted to dialcohol cellulose has been identified as a potential breakthrough material for the production of bio-based, complex, double-curved surfaces due to its extensive strain-at-break characteristics (reaching as great as 80% in tensile loading). Tensile testing of handsheets made from modified cellulose fibers was conducted from 50 to 90% relative humidity (RH) and from 23 to 150 °C. Strain-at-break of the handsheets ranged from 35 to 80% over this humidity and temperature range, which is significantly greater than typical cellulose-based materials. The combined effect of moisture and temperature was further investigated by dynamic mechanical thermal analysis, which was utilized to determine the glass-transition temperature of the handsheets as a function of relative humidity. Based on the tensile test results and verified by the three-dimensional (3-D) forming and simulation, a forming limit diagram (strain-based failure surface which describes and illustrates the formability of the material) for the handsheets was generated. This forming limit illustrates significant extent to which this bio-based material can be 3-D formed into advanced structures. Furthermore, temperature was identified as the best, quickest, and most controllable method of improving extensibility of this material during 3-D forming.

  • 11.
    Lv, Yezhe
    et al.
    School of Materials Science and Engineering, Zhengzhou University, PR China.
    Sun, Yufu
    School of Materials Science and Engineering, Zhengzhou University, PR China.
    Zhao, Jingyu
    Yu, Guangwen
    School of Materials Science and Engineering, Zhengzhou University, PR China.
    Shen, Jingjie
    School of Materials Science and Engineering, Zhengzhou University, PR China.
    Hu, Sumeng
    School of Materials Science and Engineering, Zhengzhou University, PR China.
    Effect of tungsten on microstructure and properties of high chromium cast iron2012In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 39, p. 303-308Article in journal (Refereed)
    Abstract [en]

    In this study, effect of tungsten on microstructure and properties of high chromium cast iron was investigated.The experimental results indicated that tungsten distributed uniformly in the matrix and carbides.W carbides are composed of WC1x, W6C2.54 and CW3 and W2C. With the increase of tungstencontent, bulk hardness and matrix microhardness both increased gradually and reached the peak at62.62HRC and 913HV, respectively. All of the tungsten-containing alloys performed better than tungsten-freealloys in impact tests and alloys containing 1.03 wt% W showed the highest impact toughness at8.23 J cm2. Tungsten considerably improved the performance of high chromium cast iron on wearresistance and alloys containing 1.03 wt%Wincreased 205% compared to tungsten-free alloys. Therefore,tungsten can be used as an alloying element to increase the hardness and wear resistance without scarifyingimpact toughness in high chromium cast iron. Alloys containing 1.03 wt% tungsten showed theoptimum properties.

  • 12.
    Poulikidou, Sofia
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Jerpdal, Lars
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Björklund, Anna
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Akermo, Malin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Environmental performance of self-reinforced composites in automotive applications - Case study on a heavy truck component2016In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 103, p. 321-329Article in journal (Refereed)
    Abstract [en]

    A screening environmental life cycle analysis (LCA) of the novel self-reinforced poly(ethylene therephthalate) (SrPET) is presented in this paper. A truck exterior panel is used as case study where a concept design made by SrPET is assessed and compared to a glass fibre reinforced composite and a thermoplastic blend that are currently used for the selected component. The results showed that the SrPET panel has 25% lower environmental impact compared to the current design, with no significant life cycle trade-offs. SrPET offers possibilities for weight reduction while maintaining good mechanical properties. As the impact during use phase is expected to decrease in the future the relative importance of manufacturing and end-of-life (EOL) will increase. Thus SrPET can be considered a competitive material for replacing existing energy intense non-recyclable composites.

  • 13.
    Poulikidou, Sofia
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Schneider, Christof
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Björklund, Anna
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Kazemahvazi, Sohrab
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. Univ Cambridge, England.
    Wennhage, Per
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Zenkert, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    A material selection approach to evaluate material substitution for minimizing the life cycle environmental impact of vehicles2015In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 83, p. 704-712Article in journal (Refereed)
    Abstract [en]

    Weight reduction is commonly adopted in vehicle design as a means for energy and emissions savings. However, selection of lightweight materials is often focused on performance characteristics, which may lead to sub optimizations of life cycle environmental impact. Therefore systematic material selection processes are needed that integrate weight optimization and environmental life cycle assessment. This paper presents such an approach and its application to design of an automotive component. Materials from the metal, hybrid and polymer families were assessed, along with a novel self-reinforced composite material that is a potential lightweight alternative to non-recyclable composites. It was shown that materials offering the highest weight saving potential offer limited life cycle environmental benefit due to energy demanding manufacturing. Selection of the preferable alternative is not a straightforward process since results may be sensitive to critical but uncertain aspects of the life cycle. Such aspects need to be evaluated to determine the actual benefits of lightweight design and to base material selection on more informed choices.

  • 14.
    Rehman, Hafeez Ur
    et al.
    Shanghai Jiao Tong Univ, Sch Mat Sci & Engn, State Key Lab Met Matrix Composites, Shanghai 200240, Peoples R China..
    Chen, Yujie
    Shanghai Jiao Tong Univ, Sch Mat Sci & Engn, State Key Lab Met Matrix Composites, Shanghai 200240, Peoples R China..
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Pathan, Radan
    Shanghai Jiao Tong Univ, Dept Automat, Shanghai 200240, Peoples R China..
    Liu, Hezhou
    Shanghai Jiao Tong Univ, Collaborat Innovat Ctr Adv Ship & Dee Sea Explora, Shanghai 200240, Peoples R China..
    Wang, Hesheng
    Shanghai Jiao Tong Univ, Dept Automat, Shanghai 200240, Peoples R China..
    Chen, Tao
    Shanghai Jiao Tong Univ, Sch Mat Sci & Engn, State Key Lab Met Matrix Composites, Shanghai 200240, Peoples R China..
    Zhang, Xiaomiao
    Shanghai Gen Hosp, Songjiang Rd 650, Shanghai 201620, Peoples R China..
    Li, Hua
    Shanghai Jiao Tong Univ, Collaborat Innovat Ctr Adv Ship & Dee Sea Explora, Shanghai 200240, Peoples R China..
    High-cycle-life and high-loading copolymer network with potential application as a soft actuator2019In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 182, article id UNSP 108010Article in journal (Refereed)
    Abstract [en]

    Thermo-responsive polymer materials ate appealing in emerging fields including soft robotics, artificial muscles, and actuators. However, realising a single smart polymer material that can achieve immense strain, fast actuation, and high loading remains a challenge. We attempted to address these limitations by fabricating a thermo-responsive copolymer network structure of poly(urethane-caprolactone-siloxane). The relative concentrations of these precursors were adjusted to realise a high mechanical strength of >= 17 MPa, 100% shape fixation, and a quick shape recovery time of <= 15 s. Experimental results revealed that the soft segments largely determines the extensibility and crystallinity of the copolymer material. The thermal gradient of the soft part enables the copolymer to self-heal during shape recovery. The copolymer network was applied to a load lifting device as an artificial muscle and was able to lift 200 times its weight with a short response time of <5 s and maximum power density that was half that of mammalian skeletal muscles. With its fast actuation, high loading, and self-healing abilities, the developed therrno-activated smart copolymer material is potentially applicable to a wide range of fields such as soft robotics, biomimetic devices, and prosthetics.

  • 15. Sun, Yufu
    et al.
    Hu, Sumeng
    Xiao, Zhiyun
    You, Sansan
    Zhao, Jingyu
    Yezhe, Lyu
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Tribologi.
    Effects of nickel on low-temperature impact toughness and corrosion resistanceof high-ductility ductile iron2012In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, ISSN 0264-1275, Vol. 41, p. 37-42Article in journal (Refereed)
    Abstract [en]

    High-ductility ductile iron was alloyed with 0–1.8 wt% Ni in this paper. The low-temperature impact toughness test and corrosion test of simulated seawater static whole-soaking were conducted to research the effect of nickel on the low-temperature impact toughness and corrosion resistance of high-ductility ductile iron. The results show that with nickel increasing, the impact toughness under low temperature ascents a great deal, and reaches the highest point with 0.71 wt% nickel addition, then descents; while the corrosion resistance has always been growing with the increasing of nickel content. Ductile iron containing 0.71 wt% nickel shows the best low-temperature impact toughness (the impact toughness values Akv of the samples reached 16.6 J at 20 C, 12.8 J at 40 C respectively) and exhibits the optimum combination properties. The presence of rust layer, which was made up of Fe3O4, played certain barrier for electrochemical reaction.

  • 16. Velea, M. N.
    et al.
    Schneider, Christof
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. Swerea.
    Lache, S.
    Second order hierarchical sandwich structure made of self-reinforced polymers by means of a continuous folding process2016In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 102, p. 313-320Article in journal (Refereed)
    Abstract [en]

    One typical way to obtain higher stiffness and strength to weight ratios within structural applications is to use sandwich structures containing lightweight cellular cores. In this study a novel second order hierarchical sandwich structure and its manufacturing principle are described. The whole hierarchical structure is made of a fully recyclable material - different forms of poly-ethylene terephthalate (PET): PET matrix, reinforced with PET fibres (Self reinforced - SrPET) and PET foam resulting in a recyclable structure. The manufacturing path is developed such that it can be implemented within a continuous production line. Out-of-plane compression test are carried out in order to determine the stiffness and strength properties of the proposed structure. An analytical model is developed for evaluating the out-of-plane stiffness and strength properties and used for investigating the influence of the geometric parameters on the structural performance of the proposed hierarchical sandwich structure. (C) 2016 Elsevier Ltd. All rights reserved.

  • 17.
    Walbrühl, Martin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Linder, David
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. KTH, Royal Inst Technol, Dept Mat Sci & Engn, Unit Struct, SE-10044 Stockholm, Sweden..
    Bonvalet, Manon
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. KTH, Royal Inst Technol, Dept Mat Sci & Engn, Unit Struct, SE-10044 Stockholm, Sweden..
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Borgenstam, Annika
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    ICME guided property design: Room temperature hardness in cemented carbides2019In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 161, p. 35-43Article in journal (Refereed)
    Abstract [en]

    The potential change in EU regulations may affect the traditional W-C-Co based cemented carbides industry and a methodology is required to accelerate the materials development with alternative binders. This work presents the ICME (Integrated Computational Materials Engineering) framework and the improved models that will enable tailor-made materials design of cemented carbides. The cemented carbide hardness is one of the key properties of the composites and here its close relation to the binder composition is in focus. Modeling the influence of alternative binder materials on the hardness of cemented carbides offers a way to optimize the composite properties of prospective binder candidates virtually, thereby reducing the development time and costs drastically compared to a classical trial-and-error method. The outline of a genetic algorithm is presented and the integration of the required models and tools, that are, or will become, available within this ICME framework, are presented.

  • 18.
    Zander, Johan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Modelling technological properties of commercial wrought aluminium alloys2009In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 30, no 9, p. 3752-3759Article in journal (Refereed)
    Abstract [en]

    The purpose of this paper is to model three important technological properties for aluminium alloys, based on their performance indices. The models are based on the chemical compositions and microstructure characteristics which are calculated using thermodynamical calculations. The properties that were modelled are the general corrosion, the weldability (MIG and TIC) and the machinability. The results from these models are to be used in materials selection and optimisation. The models clearly show that the general corrosion resistance is reduced for all alloy additions, except for small amounts of titanium. The largest influence on the corrosion is from copper and zinc. The weldability is negatively influenced by the copper and zinc-content, and for small additions of zirconium and titanium it is increased. The machinability is positively influenced by the hardness of the alloy or by adding lead or bismuth. For the non-heat-treatable alloys there was no influence from the composition to the corrosion resistance or the weldability. Copper and zinc which are added to increase the strength to the alloy strongly reduce both the weldability and the corrosion resistance but due to the increase in hardness increase the workability.

  • 19.
    Zander, Johan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    One parameter model for strength properties of hardenable aluminium alloys2008In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 29, no 8, p. 1540-1548Article in journal (Refereed)
    Abstract [en]

    Models for strength properties are proposed for commercially aluminium alloys. The alloy group investigated are the hardenable alloys from the 2000 (Al-Cu and Al-Cu-Mg), 6000 (Al-Mg-Si) and 7000 (Al-Zn-Mg) series. The same model for solid solution hardening that has successfully been applied to non-hardenable alloys has been used. For precipitation hardening, particle cutting and the Orowan mechanism have been considered. The same basic model is used for all strength properties. It is demonstrated that with one fitting parameter for each property, a representation with reasonable accuracy can be obtained that is applicable to a wide range of alloys. Such models are useful in materials optimisation and selection.

  • 20. Zhang, Shang-Zhou
    et al.
    Cui, Hao
    Li, Ming-Man
    Yu, Hui
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Yang, Rui
    Hu, Qing-Miao
    First-principles study of phase stability and elastic properties of binary Ti-xTM (TM = V,Cr,Nb,Mo) and ternary Ti-15TH-yAl alloys2016In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 110, p. 80-89Article in journal (Refereed)
    Abstract [en]

    The phase stability and elastic property of binary Ti-chi TM (TM=V, Cr, Nb, Mo) and ternary Ti-15TH-yAl alloys are investigated systematically by using a first-principles method. The coherent potential approximation is employed to describe the random distribution of the alloying atoms in the alloys. We show that the transition metal (TM) elements V, Cr, Nb, Mo increase the elastic stability of the beta phase but decreases that of the a phase. The polycrystalline bulk modulus of the a phase increases with the concentration of the TM alloying elements whereas the Young's modulus and shear modulus are weakened. For the beta phase, all the polycrystalline elastic moduli hardens with the addition of the TM alloying elements. The influence of the simple metal (SM) element Al on the elastic properties is much weaker than the TM ones. The TM alloying elements increase the stability of the beta relative to the alpha and omega phases. Al stabilizes significantly the beta phase over the omega phase. Our calculations suggest that the d electron density dominates the elastic modulus but not the relative phase stability. The interaction between the TM and SM alloying elements in titanium alloys matters to the relative stability.

  • 21.
    Zhao, Wenyue
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Li, Wei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Sun, Z.
    Gong, S.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Tuning the plasticity of Ni-Mo solid solution in Ni-based superalloys by ab initio calculations2017In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 124, p. 100-107Article in journal (Refereed)
    Abstract [en]

    The generalized stacking fault energies of face centered cubic Ni-Mo solid solutions are calculated using the exact muffin-tin orbital method in combination with coherent potential approximation. The alloying of Mo in Ni is found to decrease the intrinsic stacking fault energy of the solid solution from 150 mJ/m2 (pure Ni) to 50 mJ/m2 (17.5 at.% Mo) almost linearly. At the same time, the unstable stacking fault energy (the unstable twin fault energy) of the Ni-based solid solution increases (decreases) in a small extent with increasing Mo concentration. Three different twinnability measures are adopted and all indicate a substantially enhanced twinning mechanism in Ni-Mo solid solutions with increasing concentration of Mo. The weaker Ni-Ni bonding at high Mo concentrations is considered to be the main mechanism behind the disclosed phenomena. Segregation of Mo to the fault plane is proved to have strong effect on the generalized stacking fault energy of Ni-based solid solution.

  • 22.
    Zhou, Tao
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. University of Science and Technology Beijing, China.
    Babu, R. Prasath
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Odqvist, Joakim
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Yu, Hao
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Quantitative electron microscopy and physically based modelling of Cu precipitation in precipitation-hardening martensitic stainless steel 15-5 PH2018In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 143, p. 141-149Article in journal (Refereed)
    Abstract [en]

    Precipitation-hardening martensitic stainless steels rely on very fine precipitates for optimal mechanical performance. These multicomponent alloys are prone to clustering and precipitation reactions during tempering, where Cu is one of the alloying elements added to stimulate precipitation. It is efficient to use an integrated computational materials engineering (ICME) approach to tailor alloying and heat treatment for design of these alloys. The most promising physically based modelling of precipitation for this purpose at present is Langer-Schwartz-Kampmann-Wagner (LSKW) modelling within the CALPHAD framework. This approach has been successful for model alloys, but reliable results for mulhcomponent stainless steels are less common. Hence, we combine quantitative transmission electron microscopy and LSKW modelling to investigate the tempering of a martensitic stainless steel 15-5 PH at 500 degrees C. The microstructural characterization shows that the Cu precipitation and growth occur in three stages: i) Cu BCC, n) Cu 9R, and iii) Cu FCC, during tempering up to 1000 h. The modelling predictions of size, volume fraction and number density of precipitates are in good agreement with the experimental results. Thus, the approach with a combination of quantitative electron microscopy and LSKW modelling using CALPHAD-type databases holds promise for further optimization of precipitation-hardening martensitic stainless steels.

  • 23.
    Zhu, Jiqing
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Balieu, Romain
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Lu, Xiaohu
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Microstructure evaluation of polymer-modified bitumen by image analysis using two-dimensional fast Fourier transform2018In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 137, p. 164-175Article in journal (Refereed)
    Abstract [en]

    Aiming to quantitatively evaluate the microstructure of polymer-modified bitumen (PMB) for roads, this paper employs the two-dimensional fast Fourier transform(2D-FFT) to process the microscopic and numerical images of four PMBs. The related derivative parameters, including the characteristic frequency and wavelength, are computed from the 2D-FFT power spectrum. The results show that the absence/presence of a characteristic frequency (range) on the power spectrum can indicate the lack/existence of the corresponding periodical structural pattern(s) in the original PMB image. A lower characteristic frequency usually represents a coarser PMB microstructure while a higher one implies a finer PMB microstructure. The 2D-FFT method is thus valid for differentiating various PMB microstructures. The proposed method is also capable of quantitatively evaluating the effects of temperature and the temporal evolution of PMB microstructure during phase separation. As the separation continues, the decrease of characteristic frequency indicates the coarsening process of a PMB microstructure. Additionally, the numerical reproduction of the observed phase separation is evaluated with the same method. The quantitative comparison with the experimental results reveals that the simulations fairly reproduced the microscopy observation results despite some deviation. The proposed method provides a foundation for the microstructure-based modelling of PMB performance in the future.

  • 24.
    Zhu, Jiqing
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Lu, Xiaohu
    Nynas AB.
    Balieu, Romain
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Kringos, Niki
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Modelling and numerical simulation of phase separation in polymer modified bitumen by phase-field method2016In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 107, p. 322-332Article in journal (Refereed)
    Abstract [en]

    In this paper, a phase-field model with viscoelastic effects is developed for polymer modified bitumen (PMB) with the aim to describe and predict the PMB storage stability and phase separation behaviour. The viscoelastic effects due to dynamic asymmetry between bitumen and polymer are represented in the model by introducing a composition-dependent mobility coefficient. A double-well potential for PMB system is proposed on the basis of the Flory-Huggins free energy of mixing, with some simplifying assumptions made to take into account the complex chemical composition of bitumen. The model has been implemented in a finite element software package for pseudo-binary PMBs and calibrated with experimental observations of three different PMBs. Parametric studies have been conducted. Simulation results indicate that all the investigated model parameters, including the mobility and gradient energy coefficients, interaction and dilution parameters, have specific effects on the phase separation process of an unstable PMB. In addition to the unstable cases, the model can also describe and predict stable PMBs. Moreover, the phase inversion phenomenon with increasing polymer content in PMBs is also well reproduced by the model. This model can be the foundation of an applicable numerical tool for prediction of PMB storage stability and phase separation behaviour.

1 - 24 of 24
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