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  • 201.
    Ghassemali, Ehsan
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Sonkusare, Reshma
    Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur, India.
    Biswas, Krishanu
    Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur, India.
    Gurao, Nilesh P.
    Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur, India.
    Dynamic precipitation at elevated temperatures in a dual-phase AlCoCrFeNi high-entropy alloy: an in situ study2018Inngår i: Philosophical Magazine Letters, ISSN 0950-0839, E-ISSN 1362-3036, Vol. 98, nr 9, s. 400-409Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of a possible phase transformation or precipitation of the face-centred cubic (FCC) phase on intermediate-temperature deformation of a dual-phase AlCoCrFeNi high-entropy alloy has been studied using in situ tensile testing at 550°C. Electron backscatter diffraction (EBSD) results showed localised precipitation of the FCC phase during the intermediate-temperature deformation. The overall fracture behaviour and crack propagation of the material was not altered much compared to the room-temperature behaviour, namely brittle trans-granular fracture. Deformation at higher temperatures (above 750°C) is suggested as a way to enhance the dynamic FCC phase precipitation, in order to improve the ductility or deformability of the alloy. 

  • 202.
    Ghassemali, Ehsan
    et al.
    School of Mechanical & Aerospace Engineering, Nanyang Technological University and Singapore Institute of Manufacturing Technology (SIMTech).
    Tan, Ming-Jen
    School of Mechanical & Aerospace Engineering, Nanyang Technological University.
    Chua, Beng Wah
    Singapore Institute of Manufacturing Technology (SIMTech).
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning. Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Lim, S.C.V.
    Materials Engineering, Monash University.
    Grain size and workpiece dimension effects on material flow in an open-die micro-forging/extrusion process2013Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 582, nr 10, s. 379-388Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The interactive effect of grain size and specimen dimensions on the material flow and microstructural evolution was studied in a progressive open-die microforming process. Particular interest was paid on the effect of the number of grains over the initial specimen thickness, on the evolution of the dead metal zone (DMZ) in the final micro-component's microstructure. Such a DMZ is deemed unfavorable for mechanical properties of the pin. Interestingly, experimental results revealed that the DMZ can be removed at the pin surface by increasing the initial grain size. This behavior was attributed to the role of the strain gradient on the deformation. In the aspects of the forming load and dimensional measurements of the final parts, there were no significant size-effects observed in this process. This is because the neutral plane, which demarcates the two directions of material flow in the open-die forging/extrusion process, determines the amount of material flow towards the die orifice, regardless of the initial grain size.

  • 203.
    Ghassemali, Ehsan
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning. Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. School of Mechanical & Aerospace Engineering, Nanyang Technological University and Singapore Institute of Manufacturing Technology (SIMTech).
    Tan, Ming-Jen
    School of Mechanical & Aerospace Engineering, Nanyang Technological University.
    Chua, Beng Wah
    Singapore Institute of Manufacturing Technology (SIMTech).
    Lim, Samuel C.V.
    Materials Engineering, Monash University.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning. Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Friction effects during open-die micro-forging/extrusion processes: An upper bound approach2014Inngår i: Procedia Engineering / [ed] Ishikawa, T, Mori, KI, Elsevier, 2014, Vol. 81, s. 1915-1920Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In microforming processes it is preferred to not to use lubricants, due to their complex behavior in micro-scale. Nevertheless, using lubricants could increase the life time and decrease the required forming load. Thus, it is necessary to study and develop an analytical solution for different lubrication conditions in microforming processes. A previously studied upper bound model was modified in this study for various lubrication conditions in an open-die micro-forging/extrusion process. Two approaches were chosen for identifying the friction factor in the model: (i) global friction factor, (ii) localized friction factor. Comparison of the modeling results with the experimental showed the reliability of the second approach, providing a better fit.

  • 204.
    Ghassemali, Ehsan
    et al.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University and Singapore Institute of Manufacturing Technology (SIMTech).
    Tan, Ming-Jen
    School of Mechanical and Aerospace Engineering, Nanyang Technological University.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Lim, S.C.V.
    Singapore Institute of Manufacturing Technology (SIMTech).
    Progressive microforming process: Towards the mass production of micro-parts using sheet metal2013Inngår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 66, nr 5-8, s. 611-621Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although there is considerable published literature on micro-metal forming processes, there is still a lack of research towards implementing these processes commercially. Some of the challenges are handling of micro-parts and process intermittency. This work demonstrates the feasibility of producing symmetric micro-parts using a progressive forming set-up. Such a progressive forming process alleviates the challenges in handling and removal of micro-parts. Micro-pins with diameters of 0.3, 0.5, and 0.8 mm were successfully manufactured without defects. Experimental observations together with process simulation results showed that this process has three main stages: (1) indentation at the very beginning, (2) upsetting, and (3) extrusion predominantly occurring at the very end stage of the stroke. The bulk of the pin forming occurs at the end stroke of the process (extrusion stage). The effects of punch/pin diameter ratio on the pin aspect ratio and the maximum forming load were also investigated. In addition, the finite element results also revealed that a hybrid friction model was required to be implemented for better fit with experimental results as compared to the shear and Coulomb friction models.

  • 205.
    Ghassemali, Ehsan
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning. Nanyang Technological University, Singapore; Singapore Institute of Manufacturing Technology, Singapore.
    Tan, Ming-Jen
    Nanyang Technological University, Singapore.
    Lim, Samuel Chao Voon
    Monash University, Clayton, Australia.
    Wah, Chua Beng
    Singapore Institute of Manufacturing Technology, Singapore.
    Jarfors, Anders
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Experimental and Simulation of Friction Effects in an Open-Die Microforging/Extrusion Process2014Inngår i: Journal of Micro and Nano-Manufacturing, ISSN 2166-0468, Vol. 2, nr 1, s. 011005-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Friction effects during a progressive microforming process for production of micropins of various diameters were experimentally investigated and were analytically modeled, using a hybrid friction model. The response surface method and ANOVA analysis were used to generalize the findings for various pin diameters. Besides, it was shown that to get an accurate result in simulation, the friction model must be considered locally instead of a global friction model for the whole process. The effect of friction factor on the final micropart dimensions (the effect on the instantaneous location of the neutral plane) and the forming pressure were investigated. The results showed a reduction in the friction factor as die diameter increased. Following that, the optimum frictional condition to obtain the highest micropart aspect ratio was defined as the maximum friction on the interface between the die upper surface and the punch surface, together with a minimum friction inside the die orifice.

  • 206.
    Ghassemali, Ehsan
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Tan, Ming-Jen Tan
    School of Mechanical & Aerospace Engineering, Nanyang Technological University, Singapore.
    Wahb, Chua Beng
    Singapore Institute of Manufacturing Technology (SIMTech), Singapore.
    Lim, S.C.V.
    Materials Engineering, Monash University, Australia.
    Jarfors, Anders E.W.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Effect of cold-work on the Hall–Petch breakdown in copper based micro-components2015Inngår i: Mechanics of materials (Print), ISSN 0167-6636, E-ISSN 1872-7743, Vol. 80, part A, s. 124-135Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Effects of substructural dimensions on the mechanical properties of micro-pins produced by an open-die micro-extrusion/forging process were studied. Micro-pins of diameter 0.3 mm were manufactured from copper strips, having different initial grain sizes. Micro-compression tests on the micro-pins revealed no significant size effect, even if the number of grains over the diameter of the micro-pins falls below its critical value. However, relaxation of the as-formed substructure using recovery annealing led to a surprising drop in the flow stress of the micro-pins. This was explained and attributed to the number of subgrains over the diameter of the micro-pins, showing the important role of subgrains rather than grains in determining the mechanical properties.

  • 207.
    Ghassemali, Ehsan
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning. Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Sonkusare, Reshma
    Indian Institute of Technology, India.
    Biswas, Krishanu
    Indian Institute of Technology, India.
    Gurao, Nilesh P.
    Indian Institute of Technology, India.
    In-situ study of crack initiation and propagation in a dual phase AlCoCrFeNi high entropy alloy2017Inngår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 710, s. 539-546Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study reports the effect of phase distribution on crack propagation in a dual phase AlCoCrFeNi high entropy alloy (HEA) under tensile loading. The alloy is characterized by the presence of a brittle disordered BCC phase that can be toughened by precipitation of a ductile FCC phase during homogenization heat treatment. The stress and strain partitioning between the two phases is of paramount importance to determine the mechanical response of this alloy. The as-cast alloy was subjected to homogenization at 1273 K for 6 h to prevent the formation of detrimental sigma phases and to precipitate the ductile FCC phase. In-situ tensile test in a scanning electron microscope with an electron backscatter diffraction facility was carried out to understand the micro-mechanisms of deformation of the alloy. Precipitation of the FCC phase at the BCC grain boundaries reflected the effect of the FCC phase on crack deflection and branching during propagation. The strain partitioning between the two phases and the evolution of misorientation distribution was investigated. It is observed that the presence of ductile FCC high entropy phase can impart good room temperature ductility to the brittle BCC phase. As there are very few investigations performed on the dual phase HEAs, a proper microstructural design can be be achieved and can be utilized to toughen the brittle HEAs.

  • 208.
    Ghatei Kalashami, A.
    et al.
    Isfahan University of Technology, Iran.
    Kermanpur, A.
    Isfahan University of Technology, Iran.
    Ghassemali, Ehsan
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Najafizadeh, A.
    Isfahan University of Technology, Iran.
    Mazaheri, Y.
    Isfahan University of Technology and Bu-Ali Sina University, Iran.
    Correlation of microstructure and strain hardening behavior in the ultrafine-grained Nb-bearing dual phase steels2016Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 678, s. 215-226Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ultrafine-grained dual phase (DP) steels with different Nb contents (0.00, 0.06 and 0.12 wt%) were produced by cold-rolling followed by intercritical annealing of ferrite/martensite starting microstructure at 770 °C for different holding times. Scanning electron microscopy, equipped with electron backscattered diffraction (EBSD) detector, nanoindentation and tensile testing were used to characterize microstructural evolutions and their correlations to the strain hardening and fracture behavior. EBSD results confirmed the retardation effect of Nb on recrystallization. It was found that the strains stored in the grains and density of geometrically necessary dislocations (GNDs) were increased with the addition of Nb. Strain hardening analysis showed that plastic deformation of the DP steels occurred in three distinct stages, which based on the EBSD results, nanoindentation and fracture analysis, were controlled by microstructural features such martensite volume fraction and size, density of GNDs and individual ferrite and martensite tensile properties.

  • 209.
    Ghatei Kalashami, A.
    et al.
    Isfahan University of Technology, Iran.
    Kermanpur, A.
    Isfahan University of Technology, Iran.
    Ghassemali, Ehsan
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Najafizadeh, A.
    Isfahan University of Technology, Iran.
    Mazaheri, Y.
    Isfahan University of Technology and Bu-Ali Sina University, Iran.
    The effect of Nb on texture evolutions of the ultrafine-grained dual-phase steels fabricated by cold rolling and intercritical annealing2017Inngår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 694, s. 1026-1035Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dual phase (DP) steels with different amounts of Nb were produced by utilizing cold rolling and intercritical annealing of a ferrite-martensite duplex starting structure. The effects of Nb contents (0.00, 0.06, 0.12 and 0.18 wt%) on microstructure and texture evolutions were studied. Addition of Nb promoted formation of ultra-fine grained structures with the ferrite grain size of about ~1 mm and uniformlydispersed martensite particles. The results showed increasing the fraction of the high angle grain boundaries and formation of {111} fiber components in the microstructures with increasing Nb content. In addition, the texture power was decreased with the addition of Nb, resulting in random texture components

  • 210.
    Goh, C. S.
    et al.
    Singapore Institute of Manufacturing Technology.
    Gupta, M.
    Department of Mechanical Engineering, National University of Singapore.
    Jarfors, A. E. W.
    Singapore Institute of Manufacturing Technology.
    Tan, M. J.
    School of Mechanical and Aerospace Engineering.
    Wei, J.
    Singapore Institute of Manufacturing Technology.
    Magnesium and Aluminium carbon nanotube composites2010Inngår i: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 425, s. 245-261Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Carbon nanotubes are one of the most exciting discoveries of nanosized materials in the 20th century. Challenges to create materials applicable for industrial applications involve both the incorporation of the carbon nanotubes into the material and to ensure that they do not agglomerate. Aluminium and magnesium based materials are among the metals that can benefit from the incorporation of carbon nanotubes. The fabrication of Aluminium carbon nanotube composites has challenges from reactivity and degradation of the carbon nanotube additions; hence the powder metallurgy route is preferred. Magnesium based materials on the other hand do not have this limitation and both the powder metallurgical route and the casting route are viable. Among the benefits of adding carbon nanotubes are increased yield strength and stiffness. Here is important that the effect is significant already at very low addition levels. This makes it possible to increase strength without having a significant detrimental effect on ductility. In fact, for magnesium alloys ductility can be improved due to the activation of additional slip planes improving the normally low ductility of HCP structure materials. © (2010) Trans Tech Publications.

  • 211.
    Goi, K. L. S.
    et al.
    Ametek, Singapore.
    Butler, D. L.
    Nanyang Technological University, Singapore.
    Jarfors, A. E. W.
    KIMAB, Stockholm, Sweden.
    Yong, J. M. S.
    Singapore Institute of Manufacturing Technology.
    Lim, D. C. S.
    Nanyang Technological University, Singapore.
    Elastic modulus of sintered porous Ti-Si-Zr, using activation by Ti-Si mechanically alloyed powder and TiH2 powder2008Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 475, nr 1-2, s. 45-51Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel biomaterial based on Ti-Si-Zr was developed using the sintering process with a composition targeting at a bulk modulus in the same range as that of human bone, i.e. 10-30 GPa. Control of porosity should also be possible to allow for the promotion osseointegration. The sintering procedure involves the use of mechanically alloyed Ti-Si-powder, and TiH2, to promote bonding, but not consolidation. The effect of porosity on the bulk modulus using compression testing is investigated. The influence of sintering temperature, heating rate, and amount and size of the TiH2-activator on porosity are also investigated. The achievable bulk modulus was in the range of 20-55 GPa at porosity levels ranging from 16% to 54%. Porosity had a profound influence on the bulk modulus, and the choice of appropriate processing conditions enables the creation of an engineered porosity and bulk modulus primarily by varying the sintering temperature and the size of the TiH2-powder particles. © 2007.

  • 212.
    Gonapati, Santosh Reddy
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Industriell produktutveckling, produktion och design.
    Talur Chandrashekar, Gnanesh
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Industriell produktutveckling, produktion och design.
    On the possibility to increase the maximum operating temperature(MOT) of Al-20%SiC composites for wear friction and thermophysical properties.2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Aluminium is one of the prominent metals used in the automobile industries apart from cast-iron. Aluminium is used for lightweight material properties and, it meets some of the prominent mechanical properties. When aluminium is combined with silicon carbide, it improves some of the mechanical properties and provides similar strength as that of the cast-iron. The purpose of aluminium silicon carbide is to recover some of the mechanical properties and the thermal properties for the disc brakes. Aluminium is enhanced with 20% silicon carbide is cast using stir casting. In this paper, two different compositions are compared. The hardness of the samples was analyzed with the help of the Nano-indentation test. Alloy-1 shows better hardness values compared to Alloy-2. The scratch resistivity of the sample surfaces was analyzed under the microscope with the help of the Nano-scratch test. The presence of SiC particles in the aluminium matrix withstands the indenter to penetrate deep into the surface.

  • 213.
    Gondhalekar, Akash Avinash
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Design and Development of Light Weight High Entropy Alloys2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The main aim of this thesis was to design and develop new Aluminium based compositionally complex alloys (CCAs) using the high entropy alloy (HEA) concept, and to understand their evolution of microstructures during casting and also after the secondary process which is heat-treatment, and finally to evaluate their subsequent mechanical properties. Prior to the development of alloys, a computational technique ThermoCalc was used which helped in understanding the phase formation in various results. Use of thermodynamic physical parameters for predicting the stability of single-phase fields was done to assess their validity in predicting the compositional regions of the alloys developed.

    The first alloy developed is Al73.6Mg18Ni1.5Ti1.9Zr1Zn4 in at% (NiTiZrZn) CCA. The microstructure consists of the FCC as a primary phase with ~49% volume fraction along with β-AlMg and intermetallic (IM) phases including Al3Ni, Al3Ti, and Al3Zr. After casting, the microstructure showed some presence of eutectic structures. The Al3Ti, and Al3Zr IM phases seemed to precipitate early which led to less homogenization of Ti and Zr, causing deviation in the amount of these elements in the matrix. Further, the CCA was heat-treated at 375 oC for 24hrs and 48hrs and the evolution of microstructure along with its hardness and phase transformation characterisation was investigated.

    The second developed alloy was quaternary Al65.65Mg21.39Ag10.02Ni2.94 in at% (AgNi) CCA. In the as-cast state, the main phase (matrix) was FCC with ~64 % volume fraction along with BCC, β-AlMg and Al3Ni IM phases. There was a good level homogenization of all elements in the alloy. They were further heat- treated at 400 oC for 24 hrs and 48 hrs and were studied for any change in microstructure along with its hardness and thermal stability. This CCA had the highest hardness value from all developed CCAs.

    Lastly, in order to check how Ni affects the microstructure and properties of (AgNi) CCA, a ternary Al67.2Mg22.09Ag10.7 in at% (Ag) CCA was developed. The composition was kept such that it is exactly 97% by excluding the Ni. During the development of this alloy, the cast was cooled in two ways first being the normal cooled just like other CCAs and second being a fast cooling method. Both of these alloys consists of the FCC phase as a primary phase with 72% volume fraction along with BCC and β-AlMg. Both of them were also heat treated at 400 oC for 24 hrs and 48 hrs to evaluate any changes in microstructure and also to assess its hardness and thermal stability.

  • 214.
    Gracco, Antonio
    et al.
    DDS, Faculty of Dentistry, University of Padua, Padua, Italy.
    Dandrea, Martina
    DDS, Faculty of Dentistry, University of Rome, Rome, Italy.
    Deflorian, Flavio
    Department of Industrial Engineering, University of Trento, Trento, Italy.
    Zanella, Caterina
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Department of Industrial Engineering, University of Trento, Trento, Italy.
    De Stefani, Alberto
    DDS, Faculty of Dentistry, University of Padua, Padua, Italy.
    Bruno, Giovanni
    DDS, Faculty of Dentistry, University of Padua, Padua, Italy.
    Stellini, Edoardo
    DDS, Faculty of Dentistry, University of Padua, Padua, Italy.
    Application of a molybdenum and tungsten disulfide coating to improve tribological properties of orthodontic archwires2019Inngår i: Nanomaterials, ISSN 2079-4991, Vol. 9, nr 5, artikkel-id 753Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Coatings incorporating nanoparticles of molybdenum and tungsten disulfide (MoS2 and WS2)—known for their lubricating properties—are applied to orthodontic stainless steel wires to verify if there is an improvement in terms of tribological properties during the sliding of the wire along the bracket. To simulate in vitro sliding of the wire along the bracket and evaluate friction 0.019 × 0.025 inches orthodontic stainless steel (SS) wires were subjected to the application, by electrodeposition, of Ni, Ni + MoS2, and Ni + WS2 . The samples produced were analyzed with scanning electron microscopy and assessment of resistance to bending. Thirty-two test conditions have been analyzed, arising from the combination of four types of coatings (SS bare wires and strings with three types of coating), two types of self-ligating bracket (Damon Q, Ormco and In-Ovation R, GAC International), two bracket-wire angles (0◦ and 5◦), two environments (dry and wet). Analyses carried out on the samples show acceptable coatings incorporating MoS2 and WS2 and a resistance of coatings after a minimum bending. In “dry conditions” a statistically significant decrease in friction occurs for wires coated with MoS2 and WS2 if associated with the In-Ovation bracket. In “wet conditions” this decrease is observed only in isolated test conditions. Analysis of the wires after sliding tests show little wear of the applied coatings. Nanoparticles are acceptable and similar in their behavior. Improvements in terms of friction are obtained pairing coatings incorporating MoS2 and WS2 with the In-Ovation bracket in dry conditions. 

  • 215.
    Gu, Y. W.
    et al.
    Singapore Institute of Manufacturing Technology.
    Goh, C. W.
    Singapore Institute of Manufacturing Technology.
    Goi, L. S.
    Singapore Institute of Manufacturing Technology.
    Lim, C. S.
    School of Mechanical and Aerospace Engineering, Nanyang Technological University, Nanyang Avenue, Singapore.
    Jarfors, A. E. W.
    Swedish Institute for Metals Research, Stockholm, Sweden.
    Tay, B. Y.
    Singapore Institute of Manufacturing Technology.
    Yong, M. S.
    Singapore Institute of Manufacturing Technology.
    Erratum: "Solid state synthesis of nanocrystalline and/or amorphous 50Ni-50Ti alloy" (Materials Science Engineering A (2005) vol. 392 (222-228) 10.1016/j.msea.2004.09.025))2005Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 402, nr 1-2, s. 349-350Artikkel i tidsskrift (Fagfellevurdert)
  • 216.
    Gu, Y. W.
    et al.
    Singapore Institute of Mfg. Technol..
    Goh, C. W.
    Singapore Institute of Mfg. Technol..
    Goi, L. S.
    Singapore Institute of Mfg. Technol..
    Lim, C. S.
    School of Mechanical/Production Eng., Nanyang Technological University, Nanyang Avenue, Singapore.
    Jarfors, A. E. W.
    Swedish Inst. for Metals Research, Stockholm, Sweden.
    Tay, B. Y.
    Singapore Institute of Mfg. Technol..
    Yong, M. S.
    Singapore Institute of Mfg. Technol..
    Solid state synthesis of nanocrystalline and/or amorphous 50Ni-50Ti alloy2005Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 392, nr 1-2, s. 222-228Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A nanocrystalline/amorphous 50Ni-50Ti alloy was produced by solid state synthesis via mechanical alloying from elemental Ti and Ni powders. Using X-ray diffraction analysis and transmission electron microscopy techniques, a mechanically induced solid state reaction of 50Ni-50Ti was investigated. Results showed that nanocrystalline and amorphous Ni-Ti phases were obtained after mechanical alloying. The mechanical alloying of 50Ni-50Ti for 270 ks led to the formation of f.c.c. Ni(Ti) solid solution, characterized by a lattice parameter of 0.3558 nm, crystallite size of 14 nm and lattice strain of 0.98%. The particle size decreased with increasing milling time. The crystallite size of mechanically alloyed 50Ni-50Ti powders was substantially refined as the milling proceeded and the lattice strain increased with the milling time. The steady-state crystallite size was approximately 10-15 nm. The internal lattice strain in Ni-Ti alloy led to the disordering and the subsequent formation of amorphous alloy during mechanical alloying. After heat treatment at 1100 °C, the as-milled powders transformed into B2-NiTi phase and a small amount of Ti2Ni phase. © 2004 Elsevier B.V. All rights reserved.

  • 217.
    Gu, Y. W.
    et al.
    Singapore Inst. of Mfg. Technology, 71 Nanyang Drive, 638075, Singapore.
    Goi, L. S.
    Singapore Inst. of Mfg. Technology, 71 Nanyang Drive, 638075, Singapore.
    Jarfors, A. E. W.
    Singapore Inst. of Mfg. Technology, 71 Nanyang Drive, 638075, Singapore.
    Butler, D. L.
    Sch. of Mech./Production Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore.
    Lim, C. S.
    Sch. of Mech./Production Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore.
    Structural evolution in Ti-Si alloy synthesized by mechanical alloying2004Inngår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 352, nr 1-4, s. 299-304Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mechanical alloying of Ti-Si powder mixture was performed by high-energy ball milling at ambient temperature (25 °C). The structural and compositional evolutions during the mechanical alloying process were investigated by X-ray diffraction, energy dispersive spectroscopy, scanning electron microscopy and transmission electron microscopy. Results showed, that the crystallite size of Ti and Si decreased with increasing milling time and the steady-state crystallite size was between 5 and 15nm. The mechanically alloyed Ti-Si powder was predominantly nanocrystalline with traces of the remnant amorphous phase. It was found that a significant increase in solid solubility of Si in Ti was achieved by mechanical alloying. Interdiffusion between the two elements occurred during milling and the dissolution of Si in Ti was obtained after 60 h milling, forming Ti(Si) solid solution. The lattice parameter ratio c/a and the unit cell volume of h.c.p. Ti(Si) were found to decrease with increasing milling time, indicating that the shrinkage of Ti lattice was caused by diffusion of Si atoms into Ti. © 2004 Elsevier B.V. All rights reserved.

  • 218.
    Gunnarsson, Niklas
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsområde Robusta inbyggda system.
    Leisner, Peter
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsområde Robusta inbyggda system.
    Hald, J
    Hultman, L
    Influence of Ultrasound on filling of Grooves during Ni Electrodeposition2009Konferansepaper (Annet vitenskapelig)
  • 219. Gunnarsson, Niklas
    et al.
    Leisner, Peter
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsområde Robusta inbyggda system.
    Wang, X.
    Svensson, M.
    Vieider, C.
    Hultman, L.
    Electrochemically based low-cost high precision processing in MOEMS packaging2009Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 54, nr 9, s. 2458-2465Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Precision processing in MOEMS (micro-opto-electromechanical systems) packaging has been studied based on electrochemical processes with the purpose of establishing technology for low-cost multifunctional encapsulation of microsystems and assembly of opto-electric access links in polymer.

    The electrochemically based processes studied in this paper include:

    1.Electroforming of a polymer moulding tool (stamper) in a nickel sulphamate electrolyte on a high-precision 3D etched silicon template.

    2.Patterning of 3D surfaces by an electrophoretic photoresist.

    3.Precision plating of Au and Sn for self-alignment of chips by eutectic Au–Sn solder.

    The results show that nickel stampers with adequately low internal stress can be electroformed on 3D silicon wafers. Furthermore, 3D polymer samples manufactured by the nickel stampers can be patterned with metal lines down to 20 μm width using electrophoretic photoresist. Finally, eutectic Au–Sn solder bumps are realized by electroplating of Au and Sn followed by reflowing, satisfying the demands on dimension and alloy composition control over a 4 in. Si wafer.

  • 220.
    Gunnarsson, Niklas
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsområde Robusta inbyggda system.
    Leisner, Peter
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsområde Robusta inbyggda system.
    Wang, X.
    Svensson, M.
    Vieider, C.
    Hultman, L.
    Low-cost high precision processing in MEMs packaging based on electrochemical processes2007Konferansepaper (Annet vitenskapelig)
  • 221.
    Gustafsson, Tim
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Jansson, Johan
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Development and Implementation of an Anisotropic Material Model based on the Fibre Orientation in GFRPs2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Based on the fibre orientation distribution of a glass fibre reinforced polymer (GFRP) an anisotropic material model is developed and implemented in the commercial Finite Element code LS-Dyna. The material model is coupled with the fibre orientation extracted from flow filling simulations performed in Moldex3D. Central mathematical models used are the Eshelby-Mori-Tanaka model for calculating a composites effective stiffness, Advani and Tucker’s orientation averaging method for considering the fibre orientation tensors, a Lagrange polynomial controlled radial return algorithm for the application of nonlinear hardening and finally Hashin’s damage initiation criterion to establish the initiation and evolution of damage. The material model is calibrated by adjusting Lagrange polynomial data points, until the simulation response corresponds to that of experimental tensile tests. Two different glass fibre reinforced composites are evaluated, and it is concluded that the model can capture the behaviour of the experimental curves with high accuracy. By validation against experimental results, it is shown that the material model performs well. The model is also compared to other advanced commercial material modelling software’s.

  • 222.
    Hajiannia, I.
    et al.
    Department of Materials Engineering, Isfahan University of Technology, Isfahan, Iran.
    Shamanian, M.
    Department of Materials Engineering, Isfahan University of Technology, Isfahan, Iran.
    Atapour, M.
    Department of Materials Engineering, Isfahan University of Technology, Isfahan, Iran.
    Ghassemali, Ehsan
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Saeidi, N.
    Department of Materials Engineering, Isfahan University of Technology, Isfahan, Iran.
    Development of Ultrahigh Strength TRIP Steel Containing High Volume Fraction of Martensite and Study of the Microstructure and Tensile Behavior2018Inngår i: Transactions of the Indian Institute of Metals, ISSN 0972-2815, E-ISSN 0975-1645, Vol. 71, nr 6, s. 1360-1367Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new transformation induced plasticity (TRIP) steel containing high volume fraction of martensite was produced by austempering heat treatment cycle. Microstructure and tensile properties of this TRIP steel were investigated and compared to those of a dual phase (DP) steel with high martensite volume fraction. Microstructural analysis showed a mixture of ferrite, bainite, retained austenite and about 25–30 vol% of martensite in the TRIP steel. As a result of the strain induced transformation of retained austenite to martensite, the TRIP steel showed a strength elongation balance of 86% higher than that for the DP steel. In comparison to the commercial TRIP780 steel, the current TRIP steel showed a 15% higher ultimate tensile strength value while maintaining the same level of ductility. TRIP steel also had a larger work hardening exponent than DP steel at all strains. 

  • 223.
    Hajiannia, Iman
    et al.
    Department of Materials Engineering, Isfahan University of Technology, Isfahan, Iran.
    Shamanian, Morteza
    Department of Materials Engineering, Isfahan University of Technology, Isfahan, Iran.
    Atapour, Masoud
    Department of Materials Engineering, Isfahan University of Technology, Isfahan, Iran.
    Ashiri, Rouholah
    Department of Materials Science and Engineering, Dezful Branch, Islamic Azad University, Iran.
    Ghassemali, Ehsan
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    The assessment of second pulse effects on the microstructure and fracture behavior of the resistance spot welding in advanced ultrahigh-strength steel TRIP11002019Inngår i: Iranian Journal of Materials Science and Engineering, ISSN 1735-0808, Vol. 16, nr 2, s. 79-88Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, the effects of the second pulse resistance spot welding on the microstructure and mechanical properties of transformation induced plasticity 1100 steel were evaluated. The thermal process after welding was designed to improve metallurgical properties with pulse currents of 6 kA, 9 kA, and 12 kA after initial welding with 10 kA current. The effect of the second pulse on mechanical and microstructural properties was investigated. The fracture of the welds was for pulsed samples of 6 kA and 9 kA pull out with mechanical test. Due to the existence of the microstructure including the equiaxial dendritic and finer in fusin zone in the pulsed current of 9 kA, the maximum fracture energy, and maximum force were observed. A significant decrease in the FZ hardness in 6 kA current was observed in the nano-hardness results, which was attributed to the existence of martensitic and ferrite temper. The highest ratio of CTS/TSS was obtained for 6 kA and 9 kA, respectively, and force-displacement evaluation was maximum in 9 kA. The fracture surfaces included dendrites and dimples. The results of partial fracture revealed separation in the coherent boundaries of the coarse grain of the annealed region.

  • 224.
    Hajiannia, Iman
    et al.
    Isfahan Univ Technol, Dept Mat Engn, Esfahan, Iran.
    Shamanian, Morteza
    Isfahan Univ Technol, Dept Mat Engn, Esfahan, Iran.
    Atapour, Masoud
    Isfahan Univ Technol, Dept Mat Engn, Esfahan, Iran.
    Ghassemali, Ehsan
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Ashiri, Rouholah
    Islamic Azad Univ, Dezful Branch, Dept Mat Sci & Engn, Dezful, Iran.
    A microstructure evaluation of different areas of resistance spot welding on ultra-high strength TRIP1100 steel2018Inngår i: Cogent Engineering, Vol. 5, nr 1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, the microstructure of resistance spot welds of advanced ultra-high strength TRIP1100 steel was investigated. For this purpose, welding was performed after determining the best welding parameters. Four sections of the heat-affected zone (HAZ) regions were selected in the regions where the heat exchange was used to control the microstructure. Then, they were used with EBSD by scanning electron microscopy (SEM). The results showed that the TRIP1100 steel microstructure consisted of polygonal ferrites, bainites, residual austenite (RA) and martensite/austenitic islands (M/A). They also showed that the melting zone (FZ) has a lath martensite structure, and the grains are larger in packets. The structure of the martensite and different orientation grains are located in the Upper-critical area (UCHAZ). In the inter-critical region (ICHAZ), the high carbon martensitic content is higher due to the presence and the structure of ferrite and martensite. In the sub-critical region (SCHAZ), due to the tempering of martensite at a temperature below A(C1), the structure is similar to the base metal (BM), with the difference that the RA degradation reduces its structure by 50%. It was found that the RA in the BM had completely transformed. The results showed that with the movement of the BM to the weld metal, the boundaries with a low angle were increased.

  • 225.
    Hansal, W.E.G.
    et al.
    Happy Plating, Austria.
    Sandalache, G.
    Happy Plating, Austria.
    Leisner, Peter
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik.
    Pulse-electrodeposited NiP-SiC composite coatings2013Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 114, s. 851-858Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper describes the effect of modulated bipolar current (pulse reverse plating) on the incorporation of micron and submicron sized SiC particles within an electrodeposited Ni–P alloy matrix (dispersion coating). Based on electrochemical measurements, a pulse plating process has been defined and the effects of pulse parameters (type of current, frequency of current pulses and current density), the electrolyte composition and the size of the silicon carbide on the particles incorporation rate, phosphorus co-deposition rate, surface morphology, structure, micro hardness and wear resistance of the deposits has been investigated.

    The experimental results show that the phosphorus co-deposition and the particles incorporation rate decrease applying higher current density. The reduction of particle size decreases the co-deposition content of the particles within the coating. Application of pulsed current leads to a more compact composite coating, significantly improving the hardness and the tribological behaviour of the Ni/SiC deposits, mainly at higher frequency of the applied current pulses. DC and bipolar pulses generate unfavourable higher co-deposition rate of phosphorus, hence a loss in hardness has been observed. Tailored shift of the properties and alloy composition during the deposition process can be achieved by change of matrix properties via alternation of the pulse sequences.

  • 226.
    HASSAN, INAMUL
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH, Industriell produktutveckling, produktion och design.
    Effects of Austempering Process on Mechanical Behavior Properties of Compacted Graphite Iron2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The thesis paper here focuses on the effects of the austempering temperature (TA) and the austempering time (tA) on the unalloyed fully ferrite Compacted Graphite Iron (CGI), to obtain improve in mechanical properties and the study of the microstructure. The unalloyed CGI samples were austenitised at 850oC for 60 and 90 min and were then heat treated at 275, 325 and 375oC with different holding times at 30,60,90, and 120 mins. Mechanical properties like the tensile strength, yield strength, young’s modulus, Brinell and Vickers harness were conducted to perform the analysis on the samples. LOM was used for the study of the microstructure and SEM was used for the study of fractography of the fractured tensile bar.

  • 227. Helbo, C.
    et al.
    Møller, Patrick
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning - Ytteknik. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsområde Robusta inbyggda system.
    Leisner, Peter
    Acreo.
    The use of mathematical modelling in optimisation of the pulse plating of copper on printed circuit boards2000Konferansepaper (Annet vitenskapelig)
  • 228.
    Hellström, Kristina
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Density variations during solidification of lamellar graphite iron2017Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 229.
    Hellström, Kristina
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Diaconu, Lucian
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Diószegi, Attila
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Density and thermal expansion coefficients of liquid grey cast iron and austeniteInngår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940Artikkel i tidsskrift (Annet vitenskapelig)
  • 230.
    Hellström, Kristina
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Diószegi, Attila
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Diaconu, Lucian
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    A broad literature review of density measurements of liquid cast iron2017Inngår i: Metals, ISSN 2075-4701, Vol. 7, nr 5, artikkel-id 165Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    The literature on density measurements, with a particular interest in methods suitable for liquid cast iron, is reviewed. Different measurement methods based on a number of physical properties are highlighted and compared. Methods for the calculation of density are also reviewed, and the influence of alloying elements on density is, to some extent, discussed. The topic is of essence for the understanding of the material behaviour at solidification, which is pivotal in software applications for casting simulation. Since a deeper understanding of the relationship between the density of liquid cast iron and volume expansion is necessary, the conclusion that further research within the field is needed lies close at hand.

  • 231.
    Hellström, Kristina
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Svidró, Péter
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Diaconu, Lucian
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Density variations during solidification of grey cast iron2017Konferansepaper (Fagfellevurdert)
  • 232.
    Hellström, Kristina
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Svidró, Péter
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Diaconu, Lucian Vasile
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Diószegi, Attila
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Density variations during solidification of grey cast Iron2018Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, s. 155-162Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As part of moving towards a sustainable production of diesel engines for heavy vehicle applications, the ability to predict casting defects has become ever so important. In order to model the solidification process for cast components correctly, it is of essence to know how the material will actually behave. To produce sound castings, often of complex geometry, the industry relies on various simulation software for the prediction and avoidance of defects. Thermophysical properties, such as density, play an important part in these simulations. Previous measurements of how the volume of liquid grey iron changes with temperature has been made with a conventional dilatometer. Measurements have also been made in the austenitic range, then on iron-carbon-silicon alloys with a carbon content lower than 1.5 wt%. Based on these measurements the density variations during solidification were calculated. The scope for this paper is to model the volume changes during solidification with the control volume finite difference method, using data from the density measurements. 

  • 233.
    Hermansson, Erik
    et al.
    Högskolan i Jönköping, Hälsohögskolan, HHJ. Ortopedteknisk plattform.
    Marcus, Ekberg
    Högskolan i Jönköping, Hälsohögskolan, HHJ. Ortopedteknisk plattform.
    A material study of insoles: Manufactured using different methods2019Independent thesis Basic level (degree of Bachelor), 180 hpOppgave
    Abstract [en]

    Aim: The aim of this study is to evaluate if additive manufacturing (AM) is an appropriate manufacturing method for insoles in comparison to vacuum forming (VF) and subtractive manufacturing (SM) in regards of material properties such as abrasion resistance. Background: Traditionally insoles are manufactured with either VF or SM. AM has been around for some decades but implementation into orthotic and prosthetic (O&P) business has not been accomplished yet. Therefore, the quality of the products produced with AM must be tested in comparison with traditional methods. Method: A comparison of samples for the mentioned manufacturing methods was done with the help of an abrasion testing machine with the standard ASTM G133. Two samples were produced from each manufacturing method and respectively tested for one and two hours. All the samples were weighed before and after the tests with the help of a four decimal scale. The difference in weight before and after the test and coefficient of friction was evaluated. The weight difference was analyzed to see how much material had been removed from the sample. The percentage of wear loss was calculated for each specific sample, both for one hour and two hours of testing. No statistical analysis could be made due to the limited amount of samples and testing time. Result: No statistically significant could be found for either wear loss or the coefficient of friction as mentioned above. Conclusion: A conclusion whether which material having the best abrasion resistance for respectively manufacturing method could not be drawn due to limited results. This study can be seen as a pilot study where the methodology can be used in further studies. Further research on AM needs to be conducted.

  • 234.
    Hernando, Juan Carlos
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Artistic Entries from the 2017 International Metallographic Contest2018Inngår i: Metallography, Microstructure, and Analysis, ISSN 2192-9262, Vol. 7, nr 1, s. 91-92Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 235.
    Hernando, Juan Carlos
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Can you identify the microstructure?2017Inngår i: Metallography, Microstructure, and Analysis, ISSN 2192-9262, Vol. 6, nr 4, s. 362-363Artikkel i tidsskrift (Annet vitenskapelig)
  • 236.
    Hernando, Juan Carlos
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Morphological characterization of primary austenite in cast iron2017Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Automotive industry products portfolio includes a wide variety of complex‐shaped cast iron products, such as truck engine components, that need to withstand a constant trend of higher demands, especially urged by stricter environmental regulations on emissions. Combined with this continued demand on properties improvement, cast iron industry faces a process problem related to the lack of understanding of solidification and mechanisms behind defect formation.

    Casting products are highly affected by the product design and the manufacturing method itself, which governs the final microstructure and hence the final mechanical properties. Wall thickness of the moulding material strongly influences the solidification time, varying the microstructural coarseness, resulting in a component with different properties depending on the local shape of the casting.

    The main objective of this work is the characterization of the primary austenite microstructure and its coarsening process, which has been poorly documented in cast iron literature, to allow the prediction and control of these microstructural features present in the casting.

    The microstructural evolution of the primary austenite in hypoeutectic lamellar graphite iron (LGI) is studied under isothermal coarsening conditions. The dendritic microstructure suffered major morphological changes that included dendrite fragmentation, globularization, and coalescence. Empirical relations based on morphological parameters are introduced to predict the microstructural evolution of primary austenite. A novel technique for colour‐etching and semi‐automatic image analysis for the characterization of quenched dendritic microstructures in cast iron is presented. A new experimental technique for production of graphitic iron with varying nodularity is presented as a solution to control the production of compacted (CGI) and spheroidal graphite iron (SGI) under laboratory conditions. The nodularity evolution is controlled as a function of the holding time and the residual Mg, allowing the study of the primary solidification and primary microstructures of hypoeutectic CGI and SGI in future investigations.

  • 237.
    Hernando, Juan Carlos
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    The role of primary austenite morphology in cast iron2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Automotive industry products portfolio includes a wide variety of complex-shaped cast iron products, such as truck engine components. Urged by strict environmental regulations on emissions, these components constantly need to combine higher demands on performance with lighter designs. As a result, cast iron industry continuously faces new challenges related to solidification of new alloys, component designs and casting processes.

    Complex shapes, variations in the thickness of the casting and the molding material strongly influence the solidification time for a component, thus varying its microstructural coarseness and hence showing different properties depending on the local shape of the casting.

    This work increases our understanding of the morphological evolution of primary austenite occurring during isothermal coarsening at the semi-solid state. New experimental techniques have been developed to show that primary austenite coarsens according to the Ostwald ripening model in lamellar (LGI), compacted (CGI)and spheroidal (SGI) graphite iron. Significant morphological changes occur after long coarsening times, including dendrite fragmentation and coalescence. The quantitative characterization of the morphological changes during coarsening is accurately described by morphological parameters, i.e., Mγ, DIDHyd and DγNN.

    Subsequently, the impact of primary austenite morphology on the eutectic microstructures in CGI and SGI has been investigated. It was observed that the eutectic microstructures are not significantly affected by the surface area of primary austenite and the size of the interdendritic regions. Fraction, nodularity, shape distribution of graphite particles and the number of nodules and eutectic cells are similar as a function of coarsening time. These results suggest that the nucleation frequency and growth of eutectic microstructures are not significantly influenced by the morphology of primary austenite.

    Furthermore, miniaturized tensile tests demonstrated that the UTS in CGI is directly related to the primary austenite morphology. The UTS decreases with the increasing coarseness of primary austenite, showing an inverse linear relation to Mγ, DIDHyd and DγNN. These results demonstrate the strong impact of primary austenite morphology on UTS when the eutectic and eutectoid microstructures are similar, emphasizing the importance of incorporating the morphology of primary austenite in our models.

  • 238.
    Hernando, Juan Carlos
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Diószegi, Attila
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    An overview of isothermal coarsening in hypoeutectic lamellar cast iron2016Inngår i: Advances in the science and engineering of casting solidification: An MPMD symposium honoring Doru Michael Stefanescu / [ed] Laurentiu Nastac, Baicheng Liu, Hasse Fredriksson, Jacques Lacaze, Chun-Pyo Hong, Adrian Catalina, Andreas Buhrig-Polaczek, Daan M. Maijer, Charles Andrew Monroe, Adrian Sabau, Roxana Ruxanda, Alan A. Luo, Subhayu Sen, Attila Diószegi, Cham: Springer, 2016, s. 295-302Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A complete qualitative characterization of the isothermal coarsening process in hypoeutectic lamellar cast iron is presented for the first time in this work. Interrupted solidification experiments were used to study the evolution of the dendritic austenite network under long term isothermal conditions. Cylindrical samples were re-melted and isothermally coarsened for times from 2 minutes to 6 days at 1175°C after dendritic coherence was reached. Micrographs from horizontal and vertical sections of the coarsened samples are presented. Complete fragmentation of the dendrite network and further rearrangement of the solid phase are reported as new behaviors in the coarsening process in lamellar cast iron. A linear increase in secondary dendrite arm spacing in agreement with the literature is observed in the first several samples confirming qualitative observations. A new model is proposed which describes the entire coarsening process observed in this investigation.

  • 239.
    Hernando, Juan Carlos
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Diószegi, Attila
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    An overview of isothermal coarsening in hypoeutectic lamellar cast iron2015Inngår i: Advances in the science and engineering of casting solidification: An MPMD symposium honoring Doru Michael Stefanescu / [ed] Laurentiu Nastac, Baicheng Liu, Hasse Fredriksson, Jacques Lacaze, Chun-Pyo Hong, Adrian Catalina, Andreas Buhrig-Polaczek, Daan M. Maijer, Charles Andrew Monroe, Adrian Sabau, Roxana Ruxanda, Alan A. Luo, Subhayu Sen, Attila Diószegi, Hoboken, New Jersey: John Wiley & Sons, 2015, s. 295-302Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A complete qualitative characterization of the isothermal coarsening process in hypoeutectic lamellar cast iron is presented for the first time in this work. Interrupted solidification experiments were used to study the evolution of the dendritic austenite network under long term isothermal conditions. Cylindrical samples were re-melted and isothermally coarsened for times from 2 minutes to 6 days at 1175°C after dendritic coherence was reached. Micrographs from horizontal and vertical sections of the coarsened samples are presented. Complete fragmentation of the dendrite network and further rearrangement of the solid phase are reported as new behaviors in the coarsening process in lamellar cast iron. A linear increase in secondary dendrite arm spacing in agreement with the literature is observed in the first several samples confirming qualitative observations. A new model is proposed which describes the entire coarsening process observed in this investigation.

  • 240.
    Hernando, Juan Carlos
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Diószegi, Attila
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    On the primary solidification of compacted graphite iron: Microstructure evolution during isothermal coarsening2018Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 925, s. 90-97Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is widely accepted that in most commercial hypoeutectic alloys, both static mechanicalproperties and feeding characteristics during solidification, are extremely linked to the coarseness ofthe primary phase. It is therefore of critical importance to provide tools to control and predict thecoarsening process of the dendritic phase present in hypoeutectic melts. The characterization of theprimary phase, a product of the primary solidification, has traditionally been neglected whencompared to the eutectic solidification characterization in cast iron investigations. This workpresents the morphological evolution of the primary austenite present in a hypoeutectic compactedgraphite cast iron (CGI) under isothermal conditions. To that purpose, a base spheroidal graphitecast iron (SGI) material with high Mg content is re-melted in a controlled atmosphere and reversedinto a CGI melt by controlling the Mg fading. An experimental isothermal profile is applied to thesolidification process of the experimental alloy to promote an isothermal coarsening process of theprimary austenite dendrite network during solid and liquid coexistence. Through interruptedsolidification experiments, the primary austenite is preserved and observed at room temperature. Byapplication of stereological relations, the primary phase and its isothermal coarsening process arecharacterized as a function of the coarsening time applied. The microstructural evolution observedin the primary austenite in CGI and the measured morphological parameters show a similar trend tothat observed for lamellar graphite cast iron (LGI) in previous investigations. The modulus of theprimary austenite, Mγ, and the nearest distance between the centre of gravity of neighbouringaustenite particles, Dγ, followed a linear relation with the cube root of coarsening time.

  • 241.
    Hernando, Juan Carlos
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Domeij, Björn
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Diószegi, Attila
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Influence of Ti and Mo additions on the isothermal coarsening process of primary austenite in Lamellar Graphite Iron2017Konferansepaper (Fagfellevurdert)
  • 242.
    Hernando, Juan Carlos
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    Domeij, Björn
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    González, Daniel
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Amieva, José Manuel
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Diószegi, Attila
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Material och tillverkning – Gjutning.
    New experimental technique for nodularity and Mg fading control in compacted graphite iron production on laboratory scale2017Inngår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 48, nr 11, s. 5432-5441Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The narrow production window for compacted graphite iron material (CGI) drastically reduces the possibilities to produce it in small batches outside an industrial environment. This fact hinders laboratory-scale investigations on CGI solidification. This work presents a solution to that issue by introducing an experimental technique to produce graphitic cast iron of the main three families. Samples of a base hypereutectic spheroidal graphite iron (SGI) were re-melted in a resistance furnace under Ar atmosphere. Varying the holding time at 1723 K (1450 °C), graphitic irons ranging from spheroidal to lamellar were produced. Characterization of the graphite morphology evolution, in terms of nodularity as a function of holding time, is presented. The nodularity decay for the SGI region suggests a linear correlation with the holding time. In the CGI region, nodularity deterioration shows a slower rate, concluding with the sudden appearance of lamellar graphite. The fading process of magnesium, showing agreement with previous researchers, is described by means of empirical relations as a function of holding time and nodularity. The results on nodularity fade and number of nodules per unit area fade suggest that both phenomena occur simultaneously during the fading process of magnesium.

  • 243.
    Hernando, Juan Carlos
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Elfsberg, Jessica
    Scania CV AB, Södertälje, Sweden.
    Dahle, Arne
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Diószegi, Attila
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Evolution of primary austenite and its influence on eutectic microstructures during coarsening of Fe-C-Si alloys2019Inngår i: Materialia, ISSN 2589-1529, Vol. 7, artikkel-id 100391Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The evolution of primary austenite morphology during isothermal coarsening has been studied in the three main Fe–C–Si alloys used in industry, LGI, CGI, and SGI. The dendritic microstructure increases length scale during coarsening accompanied by fragmentation and coalescence of austenite crystals. The morphological parameters, SDAS, Mγ, DhydID, and Dγ show a linear relation with the cube root of coarsening time, t1/3, with similar rates for the three different Fe–C–Si alloys. The eutectic microstructures after coarsening of primary austenite in CGI and SGI alloys are not significantly affected by the surface area of primary austenite and the size of the interdendritic regions. Fraction, nodularity, shape distribution of graphite particles and the number of nodules and eutectic cells are similar when studied as a function of coarsening time. These results suggest that the nucleation frequency in CGI and SGI, and the growth of eutectic microstructures in CGI, are not significantly influenced by the morphology of primary austenite.

    Fulltekst tilgjengelig fra 2021-06-29 00:00
  • 244.
    Hernando, Juan Carlos
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Elfsberg, Jessica
    Scania CV AB, Södertälje, Sweden.
    Ghassemali, Ehsan
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Dahle, Arne
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Diószegi, Attila
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    The effect of coarsening of primary austenite on the ultimate tensile strength of hypoeutectic compacted graphite Fe-C-Si alloys2019Inngår i: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 168, s. 33-37Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of primary austenite morphology on the ultimate tensile strength (UTS) of hypoeutectic compacted graphite Fe-C-Si alloys (CGI) is studied by isothermal coarsening experiments. Secondary dendrite arm spacing (SDAS) and the morphological characteristics related to the surface area of primary austenite, M γ and D ID Hyd , increase with the cube root of coarsening time. UTS decreases linearly with increasing coarseness of primary austenite. The eutectic and eutectoid microstructures are unaffected by the primary austenite morphology. These observations demonstrate the strong influence of primary austenite morphology on the mechanical properties of hypoeutectic CGI alloys.

    Fulltekst tilgjengelig fra 2021-04-22 00:00
  • 245.
    Hernando, Juan Carlos
    et al.
    Jönköping University, Tekniska Högskolan, JTH, Material och tillverkning.
    Elfsberg, Jessica
    Scania CV AB, Södertälje, Sweden.
    Ghassemali, Ehsan
    Jönköping University, Tekniska Högskolan, JTH, Material och tillverkning.
    Dahle, Arne
    Jönköping University, Tekniska Högskolan, JTH, Material och tillverkning.
    Diószegi, Attila
    Jönköping University, Tekniska Högskolan, JTH, Material och tillverkning.
    The role of primary austenite morphology in hypoeutectic compacted graphite iron alloys2020Inngår i: International Journal of metalcasting, ISSN 1939-5981, E-ISSN 2163-3193Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work investigates the role of primary austenite morphology on the eutectic and eutectoid microstructures and the ultimate tensile strength (UTS) in a hypoeutectic compacted graphite iron (CGI) alloy. The morphology of primary austenite is modified by isothermal coarsening experiments in which holding times up to 60 min are applied to the solid–liquid region after coherency. The cooling conditions for the subsequent eutectic and eutectoid reactions are similar. Miniaturized tensile tests are performed to evaluate the UTS. The morphological characteristics related to the surface area of primary austenite, the modulus of primary austenite, Mγ, and the hydraulic diameter of the interdendritic region, DHydID, increase with the cube root of coarsening time. The eutectic and eutectoid microstructures are not significantly affected by the morphology of primary austenite, thus indicating that the morphology of the interdendritic regions does not control the nucleation frequency and growth of eutectic cells or graphite. UTS decreases linearly with the increasing coarseness of primary austenite for similar eutectic and eutectoid microstructures, demonstrating the strong influence of primary austenite morphology on the UTS in hypoeutectic CGI alloys.

  • 246.
    Hernando, Juan Carlos
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Ghassemali, Ehsan
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Diószegi, Attila
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    The morphological evolution of primary austenite during isothermal coarsening2017Inngår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 131, s. 492-499Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The morphological evolution of primary austenite in an industrial hypoeutectic lamellar cast iron was studied under isothermal conditions for coarsening times varying from 0 min to 96 h. The dendritic austenite structure formed during the primary solidification suffered major morphological changes during the isothermal coarsening process. After a sufficient coarsening time, dendrite fragmentation, globularization, and coalescence of austenite were studied using electron backscatter diffraction (EBSD) technique. This study confirmed that the secondary dendrite arm spacing (SDAS) is an inappropriate length scale to describe the primary austenite coarsening process for longer times. The application of shape independent quantitative parameters confirmed the reduction of the total interfacial area during microstructural coarsening. The modulus of the primary austenite, Mγ, which represents the volume-surface ratio for the austenite phase, and the spatial distribution of the austenite particles, measured as the nearest distance between the center of gravity of neighboring particles, Dγ, followed a linear relation with the cube root of coarsening time during the whole coarsening process. The mean curvature of the austenite interface, characterized through stereological relations, showed a linear relation to Mγ and Dγ, allowing the quantitative characterization and modeling of the complete coarsening process of primary austenite.

  • 247.
    Jammula, Chaitanya Krishna
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Industriell produktutveckling, produktion och design. Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Correlating the microstructure with wear properties of aluminium silicon carbides2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Aluminium is one of the metals playing a prominent role in automobile industry after cast iron. Because of its light weight property and good mechanical properties. When aluminium reinforced with silicon carbide showing good tribological properties and improved strength. Aluminium silicon carbide needs some good wear and frictional properties to use it as break disc. Aluminium reinforced with 15% and 20% silicon carbide and casted in two different ways, liquid casting and stir casting. Four different composites are compared in this paper. Hardness test was carried out on the samples. Increase in the Vickers hardness with increase in silicon carbide reinforcement for both the castings is observed. Rockwell C hardness is showing decreasing trend with increase in SiC reinforcement. The scratch resistance of the surface under micro level was analysed with the help of nano scratch test. The SiC particles in the aluminium matrix are resisting the indenter from deep deformation of the surface. Frictional forces are dropped whenever the indenter met the SiC particles. In other cases, SiC particles are deforming the aluminium matrix in the form of broken particles. The plastic deformation of aluminium is observed, and material is piled up on sideways of groove at high load.Sliding wear behaviour of the composites are investigated by means of reciprocating pin on plate wear rig. The test was carried out at load of 20N for five different sliding duration. Aluminium with 20% silicon carbide of liquid casting is used as a base metal. The worn-out surface of the samples is analysed in SEM. The metallography of the worn-out samples is showing some deep grooves and abrasion of the material. Wear debris from both the surfaces are forming into a cluster of layers. These layers are protecting the surface from wear in some areas were observed. Composition of tribo layer formed during the test was investigated with the help of EDS analysis. The tribo layer are rich in aluminium and silicon elements because both the samples are made of aluminium silicon carbide.

  • 248.
    Jansson, Johan
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Gustafsson, T.
    Högskolan i Jönköping, Tekniska Högskolan.
    Salomonsson, Kent
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Olofsson, Jakob
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Johansson, Joel
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Industriell produktutveckling, produktion och design.
    Appelsved, P.
    Kongsberg Automotive AB, Mullsjö, Sweden.
    Palm, M.
    Husqvarna AB, Huskvarna, Sweden.
    An anisotropic non-linear material model for glass fibre reinforced plastics2018Inngår i: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 195, s. 93-98Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper aims to present a methodology to predict the anisotropic and non-linear behaviour of glass fibre reinforced plastics using finite element methods. A material model is implemented in order to remedy the need of multiple material definitions, and to control the local plastic behaviour as a function of the fibre orientation. Injection moulding simulations traditionally provide second order orientation tensors, which are considered together with a homogenization scheme to compute local material properties. However, in the present study, fourth order tensors are used in combination with traditional methods to provide more accurate material properties. The elastic and plastic response of the material model is optimized to fit experimental test data, until simulations and experiments overlap. The proposed material model can support design engineers in making more informed decisions, allowing them to create smarter products without the need of excessive safety factors, leading to reduced component weight and environmental impact. 

  • 249.
    Jansson, Johan
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Olofsson, Jakob
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    Salomonsson, Kent
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Material och tillverkning.
    On the use of heterogeneous thermomechanical and thermophysical material properties in finite element analyses of cast components2019Inngår i: IOP Conference Series: Materials Science and Engineering, Institute of Physics (IOP), 2019, Vol. 529, nr 1, artikkel-id 012076Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Cast components generally show a heterogeneous distribution of material properties, caused by variations in the microstructure that forms during solidification. Variations caused by the casting process are not commonly considered in structural analyses, which might result in manufacturing of sub-optimised components with unexpected in-use behaviour. In this paper, we present a methodology which can be used to consider both thermomechanical and thermophysical variations using finite element analyses in cast components. The methodology is based on process simulations including microstructure modelling and correlations between microstructural features and material properties. Local material data are generated from the process simulation results, which are integrated into subsequent structural analyses. In order to demonstrate the methodology, it is applied to a cast iron cylinder head. The heterogeneous distribution of material properties in this component is investigated using experimental methods, demonstrating local variations in both mechanical and physical behaviour. In addition, the strength-differential effect on tensile and compressive behaviour of cast iron is considered in the modelling. The integrated simulation methodology presented in this work is relevant to both design engineers, production engineers as well as material scientists, in order to study and better understand how local variations in microstructure might influence the performance and behaviour of cast components under in-use conditions. 

  • 250.
    Jarfors, A. E. W.
    Singapore Inst. of Mfg. Technology, Process Technology Division, Precision Metal Forming Group, Singapore.
    A Discussion of the Dynamic Specific Heat during Solidification2003Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 437-438, s. 391-394Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    State-of-the-art solidification theory shows that the apparent latent heat of fusion decreases with increasing cooling rates, due to the creation of lattice defects. A portion of the defects condenses during and after solidification, releasing heat, causing the apparent specific heat to be dynamic. Experimental data on copper shows an increase and a maximum in the apparent specific heat at moderate cooling rates. An extension of the existing theory for dynamic specific heats is made. Previous models do not reproduce the maximum, nor do they reproduce the equilibrium value at low cooling rates. The presently derived model reproduces all essential features of the experimentally data. It also clearly shows that the effect at moderate cooling rates is significant and the tabulated values are not applicable for modelling casting.

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