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  • 151.
    Gupta, Mohit Kumar
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Li, X. -H
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Östergren, Lars
    GKN Aerospace, Trollhättan, Sweden.
    Influence of Bondcoat Spray Process on Lifetime of Suspension Plasma-Sprayed Thermal Barrier Coatings2018Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 27, nr 1-2, s. 84-97Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Development of thermal barrier coatings (TBCs) manufactured by suspension plasma spraying (SPS) is of high commercial interest as SPS has been shown capable of producing highly porous columnar microstructures similar to the conventionally used electron beam–physical vapor deposition. However, lifetime of SPS coatings needs to be improved further to be used in commercial applications. The bondcoat microstructure as well as topcoat–bondcoat interface topography affects the TBC lifetime significantly. The objective of this work was to investigate the influence of different bondcoat deposition processes for SPS topcoats. In this work, a NiCoCrAlY bondcoat deposited by high velocity air fuel (HVAF) was compared to commercial vacuum plasma-sprayed NiCoCrAlY and PtAl diffusion bondcoats. All bondcoat variations were prepared with and without grit blasting the bondcoat surface. SPS was used to deposit the topcoats on all samples using the same spray parameters. Lifetime of these samples was examined by thermal cyclic fatigue testing. Isothermal heat treatment was performed to study bondcoat oxidation over time. The effect of bondcoat deposition process and interface topography on lifetime in each case has been discussed. The results show that HVAF could be a suitable process for bondcoat deposition in SPS TBCs.

  • 152.
    Karimi Neghlani, Paria
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Sadeghimeresht, Esmaeil
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Deng, D.
    Linköping University, Division of Engineering Materials, Department of Management and Engineering, Linköping, 581 83, Sweden.
    Gruber, H.
    University of Chalmers, Division of Materials and Manufacture, Industrial and Materials Science, Gothenburg, 412 96, Sweden.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Nylen, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Influence of build layout and orientation on microstructural characteristics of electron beam melted Alloy 7182018Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 99, nr S1, s. 2903-2913Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Effects of build layout and orientation consisting of (a) height from the build plate (Z-axis), (b) distance between samples, and (c) location in the build plate (X-Y plane) on porosity, NbC fraction, and hardness in electron beam melted (EBM) Alloy 718 were studied. The as-built samples predominantly showed columnar structure with strong ˂001˃ crystallographic orientation parallel to the build direction, as well as NbC and ÎŽ-phase in inter-dendrites and grain boundaries. These microstructural characteristics were correlated with the thermal history, specifically cooling rate, resulted from the build layout and orientation parameters. The hardness and NbC fraction of the samples increased around 6% and 116%, respectively, as the height increased from 2 to 45 mm. Moreover, by increasing the height, formation of ÎŽ-phase was also enhanced associated with lower cooling rate in the samples built with a greater distance from the build plate. However, the porosity fraction was unaffected. Increasing the sample gap from 2 to 10 mm did not change the NbC fraction and hardness; however, the porosity fraction increased by 94%. The sample location in the build chamber influenced the porosity fraction, particularly in interior and exterior areas of the build plate. The hardness and NbC fraction were not dependent on the sample location in the build chamber. © 2018, The Author(s).

  • 153.
    Fargas, G.
    et al.
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Barcelona, 08019, Spain. Centre for Research in Multiscale Engineering of Barcelona, Universitat Politècnica de Catalunya, Campus Diagonal Besòs-EEBE, Barcelona, 08019, Spain.
    Roa, J. J.
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Barcelona, 08019, Spain. Centre for Research in Multiscale Engineering of Barcelona, Universitat Politècnica de Catalunya, Campus Diagonal Besòs-EEBE, Barcelona, 08019, Spain.
    Sefer, B.
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Barcelona, 08019, Spain. Centre for Research in Multiscale Engineering of Barcelona, Universitat Politècnica de Catalunya, Campus Diagonal Besòs-EEBE, Barcelona, 08019, Spain. University of Erlangen-Nuremberg, Institute for Surface Science and Corrosion, Department of Materials Science and Engineering, Erlangen, D-91058, Germany.
    Pederson, Robert
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Antti, M. -L
    Division of Materials Science, Luleå University of Technology, Luleå, S-97187, Sweden.
    Mateo, A.
    Universitat Politècnica de Catalunya, CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Barcelona, 08019, Spain. Centre for Research in Multiscale Engineering of Barcelona, Universitat Politècnica de Catalunya, Campus Diagonal Besòs-EEBE, Barcelona, 08019, Spain.
    Influence of cyclic thermal treatments on the oxidation behavior of Ti-6Al-2Sn-4Zr-2Mo alloy2018Ingår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 145, s. 218-224Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ti-6Al-2Sn-4Zr-2Mo is one of the most common titanium alloys for aerospace industry. This alloy experiences oxidation phenomenon at elevated temperatures. In the present study, cyclic thermal treatments were performed in air at 500, 593 and 700 °C, up to 500 cycles, in order to determine the oxidation kinetics and to analyze the oxide scale and alpha-case formation. Moreover, results were compared to those achieved under isothermal conditions to elucidate differences between both thermal conditions. In this sense, metallographic techniques and X-ray diffraction, together with a detailed advanced characterization of the microstructure by Field Emission Scanning Electron Microscopy and Focus Ions Beam, were used to analyze surface oxidation evolution. Results pointed out that cyclic treatments induced a strong increase of the weight gain compared to isothermal treatments. The analysis of the oxide scale revealed the formation of not only rutile, as isothermal treatments, but also anatase. Thickness of the oxide scale was higher for cyclic conditions, while alpha case did not exceed values reached by isothermal treatments and even became lower at 500 °C.

  • 154.
    Balachandramurthi, Arun Ramanathan
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Moverare, Johan
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Linköping University, Department of Management and Engineering, Linköping, Sweden.
    Dixit, Nikhil
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Pederson, Robert
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Influence of defects and as-built surface roughness on fatigue properties of additively manufactured Alloy 7182018Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 735, s. 463-474Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electron beam melting (EBM) and Selective Laser Melting (SLM) are powder bed based additive manufacturing (AM) processes. These, relatively new, processes offer advantages such as near net shaping, manufacturing complex geometries with a design space that was previously not accessible with conventional manufacturing processes, part consolidation to reduce number of assemblies, shorter time to market etc. The aerospace and gas turbine industries have shown interest in the EBM and the SLM processes to enable topology-optimized designs, parts with lattice structures and part consolidation. However, to realize such advantages, factors affecting the mechanical properties must be well understood – especially the fatigue properties. In the context of fatigue performance, apart from the effect of different phases in the material, the effect of defects in terms of both the amount and distribution and the effect of “rough” as-built surface must be studied in detail. Fatigue properties of Alloy 718, a Ni-Fe based superalloy widely used in the aerospace engines is investigated in this study. Four point bending fatigue tests have been performed at 20 Hz in room temperature at different stress ranges to compare the performance of the EBM and the SLM material to the wrought material. The experiment aims to assess the differences in fatigue properties between the two powder bed AM processes as well as assess the effect of two post-treatment methods namely – machining and hot isostatic pressing (HIP). Fractography and metallography have been performed to explain the observed properties. Both HIPing and machining improve the fatigue performance; however, a large scatter is observed for machined specimens. Fatigue properties of SLM material approach that of wrought material while in EBM material defects severely affect the fatigue life. © 2018 Elsevier B.V.

  • 155.
    Sadeghimeresht, Esmaeil
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Reddy, Liam
    The University of Nottingham, Faculty of Engineering, Nottingham, United Kingdom.
    Hussain, Tanvir
    The University of Nottingham, Faculty of Engineering, Nottingham, United Kingdom.
    Huhtakangas, Matti
    M. H. Engineering AB, Karlskoga, Sweden.
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Joshi, Shrikant V.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Influence of KCl and HCl on high temperature corrosion of HVAF-sprayed NiCrAlY and NiCrMo coatings2018Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 148, s. 17-29Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The oxidation performance of NiCrAlY and NiCrMo coatings thermally sprayed by high velocity air-fuel (HVAF) technique has been investigated in a chloridizing-oxidizing environment, with and without a KCl deposit, at 600 °C for up to 168 h. Both coatings protected the substrate in the absence of KCl due to formation of a dense Cr-rich oxide scale. In the presence of KCl, Cl−/Cl2 diffused through a non-protective and porous NiCr2O4 scale formed on NiCrAlY, leading to formation of volatile CrCl3. On the other hand, Mo in NiCrMo stimulated the formation of a more protective Cr-rich oxide scale which increased the corrosion resistance by reducing Cl−/Cl2 diffusion.

  • 156.
    Karimi Neghlani, Paria
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Raza, Tahira
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Svensson, Lars-Erik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Influence of laser exposure time and point distance on 75-μm-thick layer of selective laser melted Alloy 7182018Ingår i: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 94, nr 5-8, s. 2199-2207Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A systematic matrix with 25 samples, using five different point distances and five laser exposure times, depositing 75-μm-thick layers of Alloy 718 has been studied. The work has concentrated on defects formed, hardness of the deposits, and the microstructure. Relatively large amount of defects, both lack of fusion and porosity, was found in several of the specimens in the deposits. The defects were never possible to fully eliminate, but a significant decrease, mainly in the lack of fusion, was seen with increasing laser exposure time. The gas porosity on the other hand was not affected to any larger degree, except for the lowest laser energy input, where a slight increase in porosity was seen. A small increase in hardness was noted with increasing laser energy input. The width of the deposited beads increased with increasing laser energy, while the depth of deposits was more or less constant. However, for the lowest combination of point distance and laser exposure time, quite deep and narrow beads were formed. A comparison was made with deposition of 50-μm-thick layers, with quite similar laser energy input, but with some variation in detailed deposition parameters. It was found that the 75-μm-thick layers contained less lack of fusion, particularly for small point distances. The amount of porosity was also less, but that did not vary with deposition parameters.© 2017 The Author(s)

  • 157.
    Karimi Neghlani, Paria
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Sadeghimeresht, Esmaeil
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Åkerfeldt, Pia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Luleå, 971 87, Sweden.
    Ålgårdh, Joakim
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Powder Materials & Additive Manufacturing, Swerea KIMAB AB, Kista, 164 40, Sweden.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Influence of successive thermal cycling on microstructure evolution of EBM-manufactured alloy 718 in track-by-track and layer-by-layer design2018Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 160, s. 427-441Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Successive thermal cycling (STC) during multi-track and multi-layer manufacturing of Alloy 718 using electron beam melting (EBM) process leads to a microstructure with a high degree of complexity. In the present study, a detailed microstructural study of EBM-manufactured Alloy 718 was conducted by producing samples in shapes from one single track and single wall to 3D samples with maximum 10 longitudinal tracks and 50 vertical layers. The relationship between STC, solidification microstructure, interdendritic segregation, phase precipitation (MC, δ-phase), and hardness was investigated. Cooling rates (liquid-to-solid and solid-to-solid state) was estimated by measuring primary dendrite arm spacing (PDAS) and showed an increased cooling rate at the bottom compared to the top of the multi-layer samples. Thus, microstructure gradient was identified along the build direction. Moreover, extensive formation of solidification micro-constituents including MC-type carbides, induced by micro-segregation, was observed in all the samples. The electron backscatter diffraction (EBSD) technique showed a high textured structure in 〈001〉 direction with a few grains misoriented at the surface of all samples. Finer microstructure and possibility of more γ″ phase precipitation at the bottom of the samples resulted in slightly higher (~11%) hardness values compared to top of the samples. © 2018 Elsevier Ltd

  • 158.
    Tamil Alagan, Nageswaran
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Beno, Tomas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Hoier, Philipp
    Chalmers University of Technology, Department of Industrial and Materials Science, SE-412 96 Gothenburg, Sweden.
    Klement, Uta
    Chalmers University of Technology, Department of Industrial and Materials Science, SE-412 96 Gothenburg, Sweden.
    Wretland, Anders
    GKN Aerospace Engine Systems AB, SE-461 81 Trollhättan, Sweden.
    Influence of Surface Features for Increased Heat Dissipation on Tool Wear2018Ingår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 11, nr 5, artikel-id E664Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The critical problems faced during the machining process of heat resistant superalloys, (HRSA), is the concentration of heat in the cutting zone and the difficulty in dissipating it. The concentrated heat in the cutting zone has a negative influence on the tool life and surface quality of the machined surface, which in turn, contributes to higher manufacturing costs. This paper investigates improved heat dissipation from the cutting zone on the tool wear through surface features on the cutting tools. Firstly, the objective was to increase the available surface area in high temperature regions of the cutting tool. Secondly, multiple surface features were fabricated for the purpose of acting as channels in the rake face to create better access for the coolant to the proximity of the cutting edge. The purpose was thereby to improve the cooling of the cutting edge itself, which exhibits the highest temperature during machining. These modified inserts were experimentally investigated in face turning of Alloy 718 with high-pressure coolant. Overall results exhibited that surface featured inserts decreased flank wear, abrasion of the flank face, cutting edge deterioration and crater wear probably due to better heat dissipation from the cutting zone.

  • 159.
    Nilsen, Morgan
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Sikström, Fredrik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Ancona, Antonio
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    In-process Monitoring and Control of Robotized Laser Beam Welding of Closed Square Butt Joints2018Ingår i: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 25, s. 511-516Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    In robotized laser welding of technical zero gap closed square butt joints it is critical to position the laser beam correct with regardsto the joint. Welding with an offset from the joint may cause lack of sidewall fusion, a serious defect that is hard to detect and gives a weak weld . When using machined parts with gap and misalignment between the parts that is close to zero, existing joint tracking systems will probably fail to track the joint. A camera based system using LED illumination and matching optical filters is proposed in this paper to address this issue. A high dynamic range CMOS camera and the LED illumination is integrated into the laser tool. The camera captures images of the area in front of the melt pool where the joint is visible and an algorithm based on the Hough transform and a Kalman filter estimates the offset between the laser spot and the joint position. Welding experiments, using a 6 kW fiber laser, have been conducted to evaluate the performance of the system. Promising results are obtained that can be used in the further development of a closed loop controlled joint tracking system.

  • 160.
    Tofeldt, Oskar
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Pierce, S.G.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Smillie, G.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Kerr, W.
    Advanced Forming Research Centre, Inchinnan, Renfrewshire, UK.
    Flockhart, G.M.H.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Macleod, C.N.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Blue, R.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Gachagan, A.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Stratoudaki, T.
    University of Strathclyde, Electronic & Electrical Engineering, Glasgow, UK.
    Olsson, Jonas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    McMahon, D.
    Advanced Forming Research Centre, Inchinnan, Renfrewshire, UK.
    Investigation of fundamental ultrasonic propagation characteristics in NDT of Electron Beam Melted additive manufactured samples: Inconel 7182018Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    New approaches for efficient NDT inspection of modern additively manufactured metallic components are required urgently to qualify and validate the next generation of metallic parts across a range of industries. Ultrasonic testing is a fundamental component of NDT for such additive manufacturing processes. This work studies the ultrasonic propagation characteristics of EBM manufactured sample coupons in Inconel 718material. Fundamental longitudinal and shear wave velocity measurements are experimentally measured in 3 orthogonal build directions of the sample coupons. Results show a dependency of the ultrasonic velocities and the build direction. The measured velocities are further verified in a phased array measurement showing successful results that highlights the potential of continued studies with synthetic apertures techniques.

  • 161.
    Singh, Sukhdeep
    et al.
    Department of Industrial and Materials Science, Chalmers University of Technology, Gothenburg, Sweden.
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Investigation on effect of welding parameters on solidification cracking of austenitic stainless steel 3142018Ingår i: Procedia Manufacturing, E-ISSN 2351-9789, s. 351-357Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    This study investigates the solidification cracking susceptibility of the austenitic stainless steel 314. Longitudinal Varestraint testing was used with three different set of welding test parameters. Weld speed, current and voltage values were selected so that the same heat input resulted in all the test conditions. From the crack measurements it was seen that the test condition with the lowest current and welding speed value also produced the least amount of cracking with very good repeatability.

  • 162.
    Sadeghimeresht, Esmaeil
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Karimi Neghlani, Paria
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Zhang, Pimin
    Linköping University,Department of Management and Engineering, Linköping, Sweden.
    Peng, Ru
    Linköping University,Department of Management and Engineering, Linköping, Sweden.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Pejryd, Lars
    Örebro University, School of Science and Technology, Örebro, Sweden.
    Joshi, Shrikant V.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Isothermal Oxidation Behavior of EBM-Additive Manufactured Alloy 7182018Ingår i: Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications / [ed] Ott, E., Liu, X., Andersson, J., Bi, Z., Bockenstedt, K., Dempster, I., Groh, J., Heck, K., Jablonski, P., Kaplan, M., Nagahama, D. and Sudbrack, C., Springer, 2018, s. 219-240Konferensbidrag (Refereegranskat)
    Abstract [en]

    Oxidation of Alloy 718 manufactured by electron beam melting (EBM) process has been undertaken in ambient air at 650, 700, and 800 °C for up to 168 h. At 800 °C, a continuous external chromia oxide enriched in (Cr, Ti, Mn, Ni) and an internal oxide that was branched structure of alumina formed, whereas at 650 and 700 °C, a continuous, thin and protective chromia layer was detected. The oxidation kinetics of the exposed EBM Alloy 718 followed the parabolic rate law with an effective activation energy of ~248 ± 22 kJ/mol in good agreement with values in the literature for conventionally processed chromia-forming Ni-based superalloys. The oxide scale formed on the surface perpendicular to the build direction was slightly thicker, and more adherent compared to the scale formed on the surface along the build direction, attributed to the varied grain texture in the two directions of the EBM-manufactured specimens. The increased oxygen diffusion and high Cr depletion found on the surface along the build direction were attributed to the fine grains and formation of vacancies/voids along this grain orientation.

  • 163.
    Jafari, Reza
    et al.
    Tarbiat Modares University, Department of Material Science and Engineering, Tehran, Iran.
    Sadeghimeresht, Esmaeil
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Shahrabi Farahani, Taghi
    Tarbiat Modares University, Department of Material Science and Engineering, Tehran, Iran.
    Huhtakangas, Matti
    M. H. Engineering AB, Karlskoga, Sweden .
    Markocsan, Nicolaie
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Joshi, Shrikant V.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    KCl-Induced High Temperature Corrosion Behavior of HVAF-Sprayed Ni-Based Coatings in Ambient Air2018Ingår i: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 27, nr 3, s. 500-511Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    KCl-induced high temperature corrosion behavior of four HVAF-sprayed Ni-based coatings (Ni21Cr, Ni5Al, Ni21Cr7Al1Y, and Ni21Cr9Mo) under KCl deposit has been investigated in ambient air at 600°C up to 168h. The coatings were deposited onto 16Mo3 steel - a widely used boiler tube material.Uncoated substrate, 304L and Sanicro25 were used as reference materials in the test environment.SEM/EDS and XRD techniques were utilized to characterize the as-sprayed and exposed samples.The results showed that the small addition of KCl significantly accelerated degradation to the coatings. All coatings provided better corrosion resistance compared to the reference materials. The alumina-forming Ni5Al coating under KCl deposit was capable of forming a more protective oxide scale compared to the chromia-forming coatings as penetration of Cl through diffusion paths was hindered. Both active corrosion and chromate formation mechanisms were found to be responsible for Page 1 of 23ASM the corrosion damages. The corrosion resistance of the coatings based on the microstructure analysis and kinetics had the following ranking (from the best to worst): Ni5Al >Ni21Cr> Ni21Cr7Al1Y>Ni21Cr9Mo.

  • 164.
    Hanning, Fabian
    et al.
    Chalmers University of Technology,Department of Industrial and Materials Science, S-Gothenburg, 41296, Sweden.
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Measurement of the thermal cycle in the base metal heat affected zone of cast ATI ® 718Plus TM during manual multi-pass TIG welding2018Ingår i: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 25, s. 443-449Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a method to acquire thermal data in the base metal heat affected zone (HAZ) during manual multi-pass TIG welding of ATI ® 718Plus TM , representing conditions close to an actual repair welding operation. Thermocouples were mounted in different locations along side walls of linear grooves to record temperature data. The thermal cycling was found to be largely independent of location within the HAZ. The recorded temperatures were below the incipient laves melting temperature, indicating that the current test setup requires optimisation to study HAZ liquation. Based on the results of this study, a modified thermocouple mounting technique is proposed. © 2018 Elsevier B.V. All rights reserved.

  • 165.
    Kanhed, Satish
    et al.
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Awasthi, Shikha
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Midha, Swati
    Department of Textile Technology Indian Institute of Technology Delhi New Delhi, 110016, India.
    Nair, Jitin
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Nisar, Ambreen
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Patel, Anup Kumar
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Pandey, Aditi
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Sharma, Rajeev
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Goel, Sneha
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Upadhyaya, Anish
    Powder Metallurgy Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Ghosh, Sourabh
    Department of Textile Technology Indian Institute of Technology Delhi New Delhi, 110016, India.
    Balani, Kantesh
    Biomaterials Processing and Characterization Laboratory Department of Materials Science and Engineering Indian Institute of Technology Kanpur Kanpur-208016, Uttar Pradesh, India.
    Microporous Hydroxyapatite Ceramic Composites as Tissue Engineering Scaffolds: An Experimental and Computational Study2018Ingår i: Advanced Engineering Materials, ISSN 1438-1656, E-ISSN 1527-2648, Vol. 20, nr 7, artikel-id 1701062Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Bone‐tissue engineering mandates the development of multi‐functional bioactive porous hydroxyapatite (HAp) scaffolds. Herein, microwave sintered HAp/ZnO and HAp/Ag composite scaffolds with ≈5–19% porosity are developed using 0–30 vol% graphite as a porogen. The mechanical properties of the porous scaffold are analyzed in detail, revealing that even being more porous, the reinforcement of ZnO (9% porosity, hardness of 2.8 GPa, and toughness of 3.5 MPa.m1/2) has shown to have better hardness and fracture toughness when compared to Ag (5% porosity, hardness of 1.6 GPa, and toughness of 2.6 MPa.m1/2). The flexural strength obtained experimentally are complemented with a finite‐element technique that adopts microstructural features in visualizing the effect of porosity on stress distribution. The antibacterial efficacy and cytocompatibility of these composites are validated by increased metabolic activity and conspicuous cell‐matrix interactions. The anticipation of the results reveal that HAp/ZnO (9% porosity) and HAp/Ag (5% porosity) composites can be used as a potential multi‐functional bone implant scaffolds.

  • 166.
    Neikter, Magnus
    et al.
    Luleå University of Technology, Division of Materials Science, Luleå 971 81, Sweden.
    Åkerfeldt, P.
    Luleå University of Technology, Division of Materials Science, Luleå 971 81, Sweden.
    Pederson, Robert
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Antti, M. -L
    Luleå University of Technology, Division of Materials Science, Luleå 971 81, Sweden.
    Microstructural characterization and comparison of Ti-6Al-4V manufactured with different additive manufacturing processes2018Ingår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 143, s. 68-75Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, the microstructures of Ti-6Al-4V manufactured by different additive manufacturing (AM) processes have been characterized and compared. The microstructural features that were characterized are the α lath thickness, grain boundary α (GB-α) thickness, prior β grain size and α colony size. In addition, the microhardnesses were also measured and compared. The microstructure of shaped metal deposited (SMD) Ti-6Al-4V material showed the smallest variations in α lath size, whereas the material manufactured with laser metal wire deposition-0 (LMwD-0) showed the largest variation. The prior β grain size was found to be smaller in material manufactured with powder bed fusion (PBF) as compared with corresponding material manufactured with the directed energy deposition (DED) processes. Parallel bands were only observed in materials manufactured with DED processes while being non-present in material manufactured with PBF processes.

  • 167.
    Segerstark, Andreas
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Svensson, Lars-Erik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ojo, Olanrewaju
    University of Manitoba,Department of Mechanical Engineering, Winnipeg, R3T 5V6, Canada.
    Microstructural Characterization of Laser Metal Powder Deposited Alloy 7182018Ingår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 142, s. 550-559Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A microstructural study of Laser Metal Powder Deposition (LMPD) of Alloy 718, using a low (40 J/mm) and high (100 J/mm) heat inputs (HIs) was performed. The microstructure was characterized in as-deposited condition as well as after a standard heat-treatment, using optical microscope (OM), scanning electron microscope (SEM) and Transmission Electron Microscope (TEM). Laves, MC-carbides, γ' and γ'' are observed in the interdendritic areas of both conditions. However, the dendritic core only consists of γ-matrix. The high HI condition shows a slightly larger Primary Dendrite Arm Spacing (PDAS) as compared to the low HI condition. Additionally, the particle size of the Nb-rich constituents in the interdendriticregions (Laves-phase and Niobium carbide) are larger in the high HI sample. After heat-treatment, the Laves phase dissolves and is replaced by δ-phase in the interdendritic regions, while γ', γ'' and MC-carbideremain in the interdendritic regions. However, the γ'' precipitates seems to be less developed in the dendritic core as compared to the interdendritic regions, especially in the high HI sample. This can be attributed to a heterogeneous distribution of Nb in the microstructure, with a lower Nb content in the dendritic core as compared to close to the interdendritic regions.

  • 168.
    Hosseini, Vahid
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Innovatum AB., Trollhättan, Trollhättan, Sweden.
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Örnek, Cem
    KTH Royal Institute of Technology, Department of Chemical Science and Engineering, Division of Surface and Corrosion Science, Stockholm, Sweden, Department of Corrosion in Energy and Processing Industry, Swerea KIMAB AB, P.O. Box 7047, Kista, Sweden.
    Reccagni, Pierfranco
    The University of Manchester, School of Materials, Manchester, United Kingdom.
    Wessman, Sten
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Engelberg, Dirk
    The University of Manchester, School of Materials, Manchester, United Kingdom.
    Microstructure and functionality of a uniquely graded super duplex stainless steel designed by a novel arc heat treatment method2018Ingår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 139, s. 390-400Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel arc heat treatment technique was applied to design a uniquely graded super duplex stainless steel (SDSS), by subjecting a single sample to a steady state temperature gradient for 10 h. A new experimental approach was used to map precipitation in microstructure, covering aging temperatures of up to 1430 °C. The microstructure was characterized and functionality was evaluated via hardness mapping. Nitrogen depletion adjacent to the fusion boundary depressed the upper temperature limit for austenite formation and influenced the phase balance above 980 °C. Austenite/ferrite boundaries deviating from Kurdjumov–Sachs orientation relationship (OR) were preferred locations for precipitation of σ at 630–1000 °C, χ at 560–1000 °C, Cr2N at 600–900 °C and R between 550 °C and 700 °C. Precipitate morphology changed with decreasing temperature; from blocky to coral-shaped for σ, from discrete blocky to elongated particles for χ, and from polygonal to disc-shaped for R. Thermodynamic calculations of phase equilibria largely agreed with observations above 750 °C when considering nitrogen loss. Formation of intermetallic phases and 475 °C-embrittlement resulted in increased hardness. A schematic diagram, correlating information about phase contents, morphologies and hardness, as a function of exposure temperature, is introduced for evaluation of functionality of microstructures. © 2018 The Authors

  • 169.
    Tolvanen, Sakari
    et al.
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Pederson, Robert
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Klement, Uta
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg, Sweden.
    Microstructure and Porosity of Laser Welds in Cast Ti-6Al-4V with Addition of Boron2018Ingår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 49A, nr 5, s. 1683-1691Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Addition of small amounts of boron to cast Ti-6Al-4V alloy has shown to render a finer microstructure and improved mechanical properties. For such an improved alloy to be widely applicable for large aerospace structural components, successful welding of such castings is essential. In the present work, the microstructure and porosity of laser welds in a standard grade cast Ti-6Al-4V alloy as well as two modified alloy versions with different boron concentrations have been investigated. Prior-β grain reconstruction revealed the prior-β grain structure in the weld zones. In fusion zones of the welds, boron was found to refine the grain size significantly and rendered narrow elongated grains. TiB particles in the prior-β grain boundaries in the cast base material restricted grain growth in the heat-affected zone. The TiB particles that existed in the as cast alloys decreased in size in the fusion zones of welds. The hardness in the weld zones was higher than in the base material and boron did not have a significant effect on hardness of the weld zones. The fusion zones were smaller in the boron-modified alloys as compared with Ti-6Al-4V without boron. Computed tomography X-ray investigations of the laser welds showed that pores in the FZ of the boron modified alloys were confined to the lower part of the welds, suggesting that boron addition influences melt pool flow. © 2018 The Author(s)

  • 170.
    Murray, James W.
    et al.
    University of Nottingham, Faculty of Engineering, UK.
    Leva, Alessandro
    University of Nottingham, Faculty of Engineering, UK.
    Joshi, Shrikant V.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Hussain, Tanvir
    University of Nottingham, Faculty of Engineering, UK.
    Microstructure and wear behaviour of powder and suspension hybrid Al2O3–YSZ coatings2018Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 44, nr 7, s. 8498-8504Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract Suspension based plasma sprayed coatings can yield superior microstructural and tribological properties compared to conventional powder based plasma sprayed coatings. This study investigates a new hybrid method, using simultaneous spraying from powder and suspension, to produce composite coatings using alumina and yttria stabilised zirconia (YSZ), with potentially excellent wear and thermal properties. Dry sliding wear showed the alumina suspension-YSZ suspension coating yielded half the specific wear rate of the alumina powder-YSZ suspension, explained by preferential gamma alumina formation and increased porosity in the latter. Both YSZ-containing samples showed superior toughness and wear rate than simple alumina powder and suspension coatings.

  • 171.
    Asala, G.
    et al.
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, Canada.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ojo, Olanrewaju
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, Canada.
    Microstructure Dependence of Dynamic Impact Behaviour of ATI 718plus® Superalloy2018Ingår i: Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications / [ed] Ott, E., Liu, X., Andersson, J., Bi, Z., Bockenstedt, K., Dempster, I., Groh, J., Heck, K., Jablonski, P., Kaplan, M., Nagahama, D. and Sudbrack, C., Springer, 2018, s. 369-378Konferensbidrag (Refereegranskat)
    Abstract [en]

    ATI 718Plus® is a γ′-strengthened nickel-based superalloy developed to substitute the widely used Alloy 718 in aero-engine applications. This newer superalloy is a candidate material for aero-engine turbine structures, with the requirement to withstand impact loading occurring at high strain rates during turbine blade out events. Furthermore, the understanding of the high strain rate response of ATI 718Plus® is important in optimising its machinability during cutting operations. To predict and model the behaviour of ATI 718Plus® during these events and in other dynamic impact applications, proper understanding of the high strain rate behaviour of the alloy is important, but not presently available. Therefore, in this work, the influence of microstructural condition and strain rates on dynamic impact behaviour of ATI 718Plus®, using a modified version of direct impact Hopkinson bar, is investigated. It is observed that the age-hardened alloy exhibits a significantly reduced strain hardening and strain rate hardening capabilities compared to the solution heat treated microstructure. Furthermore, microstructural examination of the deformed samples shows that the formation of adiabatic shear bands, which usually serve as damage nucleation site, is substantially suppressed in the solution heat treated microstructure, while the aged microstructure exhibits high propensity to form localised shear bands.

  • 172.
    Karimi Neghlani, Paria
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Deng, Dunyong
    Linköping University, Division of Engineering Materials, Linköping, Sweden.
    Sadeghimeresht, Esmaeil
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Olsson, Jonas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Ålgårdh, Joakim
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Swerea KIMAB AB, Kista, Sweden.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Microstructure Development in Track-by-Track Melting of EBM-Manufactured Alloy 7182018Ingår i: Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications / [ed] Ott, E., Liu, X., Andersson, J., Bi, Z., Bockenstedt, K., Dempster, I., Groh, J., Heck, K., Jablonski, P., Kaplan, M., Nagahama, D. and Sudbrack, C., Springer, 2018, s. 643-654Konferensbidrag (Refereegranskat)
    Abstract [en]

    Electron beam melting (EBM) is a powder-bed fusion process within the group of additive manufacturing (AM) technology that is used to fabricate high performance metallic parts. Nickel-Iron base superalloys, such as Alloy 718, are subjected to successive heating and cooling at temperatures in excess of 800 °C during the EBM process. Characterization of the dendritic structure, carbides, Laves and δ-phase were of particular interest in this study. These successive thermal cycles influence the microstructure of the material resulting in a heterogeneous structure, especially in the building direction. Hence, the aim of this study was to gain increased fundamental understanding of the relationship between the processing history and the microstructure formed within a single layer. Different numbers of tracks with equal heights were for this purpose produced, varying from one to ten tracks. All tracks used the same process parameters regardless of number and/or position. Microstructure characteristics (sub-grain structure, grain structure and phases) were analyzed by optical microscopy, scanning electron microscopy equipped with energy disperse spectroscopy and electron backscatter diffraction. The direction of dendrites changed in the overlap zones within the tracks due to re-melting of material in the overlap zone. The primary dendrite arm spacings slightly increased along multi-tracks owing to a slight decrease in cooling rate by addition of the next tracks. Epitaxial growth of grains were observed in all samples due to partial re-melting of grains in previous layers and surface nucleation was also found to occur in all tracks.

  • 173.
    Kumara, Chamara
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Microstructure Modelling of Additive Manufacturing of Alloy 7182018Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In recent years, additive manufacturing (AM) of Alloy 718 has received increasing interest in the field of manufacturing engineering owing to its attractive features compared to those of conventional manufacturing methods. The ability to produce complicated geometries, low cost of retooling, and control of the microstructure are some of the advantages of the AM process over traditional manufacturing methods. Nevertheless, during the building process, the build material undergoes complex thermal conditions owing to the inherent nature of the process. This results in phase transformation from liquid to solid and solid state. Thus, it creates microstructural gradients in the built objects, and as a result,heterogeneous material properties. The manufacturing process, including the following heat treatment that is used to minimise the heterogeneity, will cause the additively manufactured material to behave differently when compared to components produced by conventional manufacturing methods. Therefore, understanding the microstructure formation during the building and subsequent post-heat treatment is important, which is the objective of this work. Alloy 718 is a nickel-iron based super alloy that is widely used in the aerospace industry and in the gas turbine power plants for making components subjected tohigh temperatures. Good weldability, good mechanical properties at high temperatures, and high corrosion resistance make this alloy particularly suitablefor these applications. Nevertheless, the manufacturing of Alloy 718 components through traditional manufacturing methods is time-consuming and expensive. For example, machining of Alloy 718 to obtain the desired shape is difficult and resource-consuming, owing to significant material waste. Therefore, the application of novel non-conventional processing methods, such as AM, seems to be a promising technique for manufacturing near-net-shape complex components.In this work, microstructure modelling was carried out by using multiphase-field modelling to model the microstructure evolution in electron beam melting (EBM) and laser metal powder directed energy deposition (LMPDED) of Alloy 718 and x subsequent heat treatments. The thermal conditions that are generated during the building process were used as input to the models to predict the as-built microstructure. This as-built microstructure was then used as an input for the heat treatment simulations to predict the microstructural evolution during heat treatments. The results showed smaller dendrite arm spacing (one order of magnitude smaller than the casting material) in these additive manufactured microstructures, which creates a shorter diffusion length for the elements compared to the cast material. In EBM Alloy 718, this caused the material to have a faster homogenisation during in-situ heat treatment that resulting from the elevated powder bed temperature (> 1000 °C). In addition, the compositional segregation that occurs during solidification was shown to alter the local thermodynamic and kinetic properties of the alloy. This was observed in the predicted TTT and CCT diagrams using the JMat Pro software based on the predicted local segregated compositions from the multiphase-field models. In the LMPDED Alloy 718 samples, this resulted in the formation of δ phase in the interdendritic region during the solution heat treatment. Moreover, this resulted in different-size precipitation of γ'/γ'' in the inter-dendritic region and in the dendrite core. Themicro structure modelling predictions agreed well with the experimental observations. The proposed methodology used in this thesis work can be an appropriate tool to understand how the thermal conditions in AM affect themicro structure formation during the building process and how these as-built microstructures behave under different heat treatments.

  • 174.
    Raza, Tahira
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Svensson, Lars-Erik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Microstructure of Selective Laser Melted Alloy 718 in As-Manufactured and Post Heat Treated Condition2018Ingår i: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 25, s. 450-458Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Manufacturing of Alloy 718 with selective laser melting (SLM) process faces several challenges. One of the challenges is the process-induced porosities in as-manufactured SLM parts. Another challenge is the microstructure of Alloy 718 that contains a high amount of segregating elements, such as MC-type carbides and γ/Laves phase eutectics in interdendritic regions. The microstructural heterogeneity in the as-manufactured SLM part unavoidably leads to mechanical heterogeneity and hence, post-processing heat treatments become necessary to achieve a homogeneous microstructure. Therefore, by investigating various post heat treatment options the knowledge on how to decrease/eliminate these segregations will be developed. © 2018 Elsevier B.V. All rights reserved.

  • 175.
    Svenman, Edvard
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW). GKN Aerospace Engine Systems, Trollhättan, Sweden.
    Modeling of inductive coil geometry for gap position measurement2018Ingår i: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 25, s. 103-110Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Finite element modelling of high frequency inductive coils and metal plates was used to investigate the impedance response to a narrow gap between the plates. The model was used to predict distance sensitivity for both coil-to-gap and coil-to-plate. Different coil axis orientations, along and across the gap and normal to the plate, were modeled, as well as different coil lengths. The model can be used to predict the working range and select orientation and geometry of inductive seam tracking probes with zero gap capability for precision laser beam welding. Different materials, thicknesses and frequencies can be used.

  • 176.
    Kumara, Chamara
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Deng, Dunyong
    Linköping University, Division of Engineering Materials, Department of Management and Engineering, Linköping, Sweden.
    Moverare, Johan
    Linköping University, Division of Engineering Materials, Department of Management and Engineering, Linköping, Sweden.
    Nylén, Per
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Modelling of anisotropic elastic properties in alloy 718 built by electron beam melting2018Ingår i: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 34, nr 5, s. 529-537Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Owing to the inherent nature of the process, typically material produced via electron beam melting (EBM) has a columnar microstructure. As a result of that, the material will have anisotropic mechanical properties. In this work, anisotropic elastic properties of EBM built Alloy 718 samples at room temperature were investigated by using experiments and modelling work. Electron backscatter diffraction data from the sample microstructure was used to predict the Young’s modulus. The results showed that the model developed in the finite element software OOF2 was able to capture the anisotropy in the Young’s modulus. The samples showed transversely isotropic elastic properties having lowest Young’s modulus along build direction. In addition to that, complete transversely isotropic stiffness tensor of the sample was also calculated. © 2018 Institute of Materials, Minerals and Mining.

  • 177.
    Panwisawas, Chinnapat
    et al.
    University of Birmingham,School of Metallurgy and Materials, , Edgbaston, Birmingham B15 2TT, UK.
    Sovani, Yogesh
    University of Birmingham, School of Metallurgy and Materials, Edgbaston, Birmingham B15 2TT, UK.
    Turner, Richard P.
    University of Birmingham, School of Metallurgy and Materials, Edgbaston, Birmingham B15 2TT, UK.
    Brooks, Jeffery W.
    University of Birmingham, School of Metallurgy and Materials, Edgbaston, Birmingham B15 2TT, UK.
    Basoalto, Hector C.
    University of Birmingham, School of Metallurgy and Materials, Edgbaston, Birmingham B15 2TT, UK.
    Choquet, Isabelle
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Modelling of thermal fluid dynamics for fusion welding2018Ingår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 252, nr February, s. 176-182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A fluid dynamics approach to modelling of fusion welding in titanium alloys is proposed. The model considers the temporal and spatial evolution of liquid metal/gas interface to capture the transient physical effects during the heat source–material interaction of a fusion welding process. Melting and vaporisation have been considered through simulation of all interfacial phenomena such as surface tension, Marangoni force and recoil pressure. The evolution of the metallic (solid and liquid) and gaseous phases which are induced by the process enables the formation of the keyhole, keyhole dynamics, and the fully developed weld pool geometry. This enables the likelihood of fluid flow-induced porosity to be predicted. These features are all a function of process parameters and formulated as time-dependent phenomena. The proposed modelling framework can be utilised as a simulation tool to further develop understanding of defect formation such as weld-induced porosity for a particular fusion welding application. The modelling results are qualitatively compared with available experimental information.

  • 178.
    Susi, Bryan T
    et al.
    Applied Research Associates Inc., Raleigh, USA.
    Tu, Juei-feng
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Molecular Dynamics Simulations of the Wetting Behavior of Carbon Nanotubes in Liquid Copper2018Ingår i: Computers & Fluids, ISSN 0045-7930, E-ISSN 1879-0747, Vol. 172, s. 19-28Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Although it is generally agreed that carbon is not wetted by liquid copper, the degree of rejection for a Single Wall Carbon Nanotube (SWCNT) has not been quantified. This paper presents Molecular Dynamics (MD) simulations to quantify the magnitude of resistance liquid copper imposes on a (5,5) SWCNT under static and dynamic intrusion scenarios. Two new sets of coefficients for the Morse potential model are proposed that better predict interfacial behavior between liquid copper and carbon. The proposed models, after being validated using empirically observed contact angle data for liquid copper and carbon, are used to investigate the wettability of a (5,5) single-walled carbon nanotube in liquid copper. It was found that the force required to submerge an initially un-wetted SWCNT into liquid copper under static conditions is higher than the expected force calculated from macro-scale fluid dynamic theory. The results indicate that a perturbation in the liquid copper surface reduces the force required for the SWCNTs to become incorporated in the liquid copper.

  • 179.
    Eynian, Mahdi
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Magnevall, Martin
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Sandvik Coromant AB, Sandviken, 81181, Sweden.
    Cedergren, Stefan
    GKN Aerospace Sweden AB, Trollhättan, 46138, Sweden.
    Wretland, Anders
    GKN Aerospace Sweden AB, Trollhättan, 46138, Sweden.
    Lundblad, Mikael
    Sandvik Coromant AB, Sandviken, 81181, Sweden.
    New methods for in-process identification of modal parameters in milling2018Ingår i: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 77, s. 469-472Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Chatter vibrations encountered in machining can degrade surface finish and damage the machining hardware. Since chatter originates from unstable interaction of the machining process and the machining structure, information about vibration parameters of the machining structure should be used to predict combinations of cutting parameters that allow stable machining. While modal test methods, for example those with impact hammers, are widely used to identify structural parameters; the need for sophisticated test equipment is prohibitive in their use. Furthermore, dynamic properties of critical components of a machine tool may change as they get affected by cutting loads, material removal and spindle rotation. Recently few algorithms have been proposed that identify the in-process dynamic parameters by frequency measurements, thus avoiding these problems. In this paper, some of these algorithms are reviewed and their capabilities and limitations in processing am experimental data set are compared and discussed. © 2018 The Authors. Published by Elsevier Ltd.

  • 180.
    Sadeghimeresht, Esmaeil
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Ni-based coatings for high temperature corrosion protection2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Biomass/waste-fired boilers severely suffer from high temperature corrosion of critical load-bearing components, e.g. water-wall and superheater tubes, due to presence of Cl-containing corrosive species. Deposition of a dense and adherent Ni-based coating by high velocity air-fuel (HVAF) thermal spray technique is a promising approach to extend the component's lifetime and, hence, increase the thermal/electrical efficiency of the boilers. In this research, high temperature corrosion of candidate Ni-based coatings –Ni21Cr, Ni21Cr7AlY, Ni5Al, Ni21Cr9Mo, Ni21Cr9Mo-SiO2 – sprayed by HVAF has been investigated through detailed laboratory studies in ambient air, moisture and HCl-laden environments. The exposures were conducted at 600 °C for up to 168 h with and without presence of KCl salt. All coatings were highly protective in all environments in the absence of KCl due to formation of corresponding protective scales of alumina or chromia on the coating surface. When KCl was introduced, chromia-forming coatings degraded through a two-stage mechanism; 1) formation of K2CrO4 and Cl- followed by diffusion of Cl- through oxide grain boundaries, leading to formation of Cl2, metal chlorides as well as a nonprotective oxide, and 2) inward diffusion of the formed Cl2 through defects in the non-protective oxide, leading to metal chloride evaporation and breakaway oxidation. The corrosion behavior of the chromia-forming Ni21Cr coating was improved by addition of alloying elements such as Al and Mo. It was also shown that adding dispersed SiO2 further increased the corrosion resistance of the coatings. The oxide scale formed in the presence of SiO2 effectively suppressed Cl- ingress and lowered the corrosion rate, since the formed oxide was continuous, adherent andrich in Cr. The performance of the coatings in the complex Cl-containing environment was ranked as (from highest to lowest corrosion resistance); Ni21Cr9Mo-SiO2 > Ni21Cr7AlY > Ni5Al > Ni21Cr9Mo > Ni21Cr, confirming the enhanced corrosion protection of chromia-forming coatings in the presence of alloying elements and dispersed SiO2.

  • 181.
    de Blanche, Andreas
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för Matematik, Data- och Lantmäteriteknik.
    Lundqvist, Thomas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för Matematik, Data- och Lantmäteriteknik.
    Node Sharing for Increased Throughput and Shorter Runtimes: an Industrial Co-Scheduling Case Study2018Ingår i: Proceedings of the 3rd Workshop on Co-Scheduling of HPC Applications (COSH 2018): Held together with HiPEAC 2018 / [ed] Trinitis, Carsten; Weidendorfer, Josef, 2018, s. 15-20Konferensbidrag (Refereegranskat)
    Abstract [en]

    The allocation of jobs to nodes and cores in industrial clusters is often based on queue-system standard settings, guesses or perceived fairness between different users and projects. Unfortunately, hard empirical data is often lacking and jobs are scheduled and co-scheduled for no apparent reason. In this case-study, we evaluate the performance impact of co-scheduling jobs using three types of applications and an existing 450+ node cluster at a company doing large-scale parallel industrial simulations. We measure the speedup when co-scheduling two applications together, sharing two nodes, compared to running the applications on separate nodes. Our results and analyses show that by enabling co-scheduling we improve performance in the order of 20% both in throughput and in execution times, and improve the execution times even more if the cluster is running with low utilization. We also find that a simple reconfiguration of the number of threads used in one of the applications can lead to a performance increase of 35-48% showing that there is a potentially large performance increase to gain by changing current practice in industry.

  • 182.
    Nystedt, Patrik
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för Matematik, Data- och Lantmäteriteknik.
    Öinert, Johan
    Blekinge Institute of Technology, Department of Mathematics and Natural Sciences, Karlskrona, Sweden.
    Richter, Johan
    Mälardalen University, Academy of Education, Culture and Communication,Västerås, Sweden.
    Non-associative Ore extensions2018Ingår i: Israel Journal of Mathematics, ISSN 0021-2172, E-ISSN 1565-8511, Vol. 224, nr 1, s. 263-292Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We introduce non-associative Ore extensions, S = R[X; sigma, delta], for any non-ssociative unital ring R and any additive maps sigma, delta : R -> R satisfying sigma(1) = 1 and delta(1) = 0. In the special case when delta is either left or right R-delta-linear, where R-delta = ker(delta), and R is delta-simple, i.e. 0 and R are the only delta-invariant ideals of R, we determine the ideal structure of the non-associative differential polynomial ring D = R[X; id(R),delta]. Namely, in that case, we show that all non-zero ideals of D are generated by monic polynomials in the center Z(D) of D. We also show that Z(D) = R-delta[p] for a monic p is an element of R-delta [X], unique up to addition of elements from Z(R)(delta) . Thereby, we generalize classical results by Amitsur on differential polynomial rings defined by derivations on associative and simple rings. Furthermore, we use the ideal structure of D to show that D is simple if and only if R is delta-simple and Z(D) equals the field R-delta boolean AND Z(R). This provides us with a non-associative generalization of a result by Oinert, Richter and Silve-strov. This result is in turn used to show a non-associative version of a classical result by Jordan concerning simplicity of D in the cases when the characteristic of the field R-delta boolean AND Z(R) is either zero or a prime. We use our findings to show simplicity results for both non-associative versions of Weyl algebras and non-associative differential polynomial rings defined by monoid/group actions on compact Hausdorff spaces.

  • 183.
    Bonilla Hernández, Ana Esther
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    On cutting tool resource management2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The search for increased productivity and cost reduction in machining can be interpreted as desire to increase the Material Removal Rate, , and maximize the cutting tool utilization. The CNC process is complex and involves numerous constraints and parameters; ranging from tolerances to machinability. A well-managed preparation process creates the foundation for achieving a reduction in manufacturing errors and machining time. Along the preparation process of the NC-program, two different studies have been performed and are presented in this thesis. One study examined the CAM programming process from the Lean perspective. The other study includes an evaluation of how the cutting tools are used in terms of and tool utilization. Two distinct combinations of cutting data might provide the same . However, the tool life and machining cost can be different. Therefore, selection of appropriate cutting parameters that best meet all these objectives is challenging. An algorithm for analysis and efficient selection of cutting data for maximal , maximal tool utilization and minimal machining cost has been developed and is presented in this work. The presented algorithm shortens the time dedicated to the optimized cutting data selection and the needed iterations along the program development. Furthermore, the objectives that need to be considered during the estimation of the manufacturing processes sustainability have been identified. In addition, this thesis also includes a theoretical study to estimate energy use, CO2-footprint and water consumption during the manufacture of a workpiece, which can be invaluable for companies in their search for sustainability of their manufacturing processes.

  • 184.
    Alizadeh-Khameneh, Mohammad Amin
    et al.
    KTH Royal Institute of Technology, Division of Geodesy and Satellite Positioning, Stockholm, Sweden.
    Eshagh, Mehdi
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för Matematik, Data- och Lantmäteriteknik.
    Jensen, Anna O.
    KTH Royal Institute of Technology, Division of Geodesy and Satellite Positioning, Stockholm, Sweden.
    Optimization of deformation monitoring networks using finite element strain analysis2018Ingår i: Journal of Applied Geodesy, ISSN 1862-9016, E-ISSN 1862-9024, Vol. 2, nr 2, s. 187-197Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An optimal design of a geodetic network can fulfill the requested precision and reliability of the network, and decrease the expenses of its execution by removing unnecessary observations. The role of an optimal design is highlighted in deformation monitoring network due to the repeatability of these networks. The core design problem is how to define precision and reliability criteria. This paper proposes a solution, where the precision criterion is defined based on the precision of deformation parameters, i. e. precision of strain and differential rotations. A strain analysis can be performed to obtain some information about the possible deformation of a deformable object. In this study, we split an area into a number of three-dimensional finite elements with the help of the Delaunay triangulation and performed the strain analysis on each element. According to the obtained precision of deformation parameters in each element, the precision criterion of displacement detection at each network point is then determined. The developed criterion is implemented to optimize the observations from the Global Positioning System (GPS) in Skåne monitoring network in Sweden. The network was established in 1989 and straddled the Tornquist zone, which is one of the most active faults in southern Sweden. The numerical results show that 17 out of all 21 possible GPS baseline observations are sufficient to detect minimum 3 mm displacement at each network point. © 2018 Walter de Gruyter GmbH, Berlin/Boston.

  • 185.
    Nystedt, Patrik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för Matematik, Data- och Lantmäteriteknik.
    Partial category actions on sets and topological spaces2018Ingår i: Communications in Algebra, ISSN 0092-7872, E-ISSN 1532-4125, Vol. 46, nr 2, s. 671-683Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We introduce (continuous) partial category actions on sets (topological spaces) and show that each such action admits a universal globalization. Thereby, we obtain a simultaneous generalization of corresponding results for groups, by Abadie, and Kellendonk and Lawson, and for monoids, by Megrelishvili and Schroder. We apply this result to the special case of partial groupoid actions where we obtain a sharpening of a result by Gilbert, concerning ordered groupoids, in the sense that mediating functions between universal globalizations always are injective.

  • 186.
    Wiklund, Daniel
    et al.
    Swerea IVF, Box 104, Mölndal, SE-431 22, Sweden.
    Larsson, Mats
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Phenomenological friction model in deep drawing of aluminum sheet metals2018Ingår i: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 418, nr 1, s. 1-8, artikel-id 012097Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Friction is an important parameter in sheet metal forming since it influences the flow of material in the process. Consequently, it is also an important parameter in the design process of new stamping dies when numerical simulations are utilized. Today, the most commonly used friction model in forming simulations is Coulomb’s friction which is a strong simplification of the tribological system conditions and a contributory cause of discrepancy between simulation and physical experiments. There are micromechanical models available but with an inherent complexity that results in limited transparency for users. The objective in this study was to design a phenomenological friction model with a natural level of complexity when Coulomb’s friction is inadequate. The local friction model considers implicit properties of tool and sheet surface topography, lubricant viscosity, sheet metal hardness and strain, and process parameters such as sliding speed and contact pressure. The model was calibrated in a Bending-Under-Tension test (BUT) and the performance was evaluated in a cross shaped geometry (X-die). The results show a significant improvement of the simulation precision and provide the user a transparent tribological system. © Published under licence by IOP Publishing Ltd.

  • 187.
    Seif, M. R.
    et al.
    Arak University of Technology, Department of Surveying Engineering, Arak, Iran.
    Sharifi, M. A.
    University of Tehran, School of Surveying and Geospatial Engineering, College of Engineering, Tehran, Iran.
    Eshagh, Mehdi
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för Matematik, Data- och Lantmäteriteknik.
    Polynomial approximation for fast generation of associated Legendre functions2018Ingår i: Acta Geodaetica et Geophysica, ISSN 2213-5812, Vol. 53, nr 2, s. 275-293Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Today high-speed computers have simplified many computational problems, but fast techniques and algorithms are still relevant. In this study, the Hermitian polynomial approximation is used for fast evaluation of the associated Legendre functions (ALFs). It has lots of applications in geodesy and geophysics. This method approximates the ALFs instead of computing them by recursive formulae and generate them several times faster. The approximated ALFs by the Newtonian polynomials are compared with Hermitian ones and their differences are discussed. Here, this approach is applied for computing a global geoid model point-wise from EGM08 to degree and order 2160 and in propagating the orbit of a low Earth orbiting satellite. Our numerical results show that the CPU-time decreases at least two times for orbit propagation, and five times for geoid computation comparing to the case where recursive formulae for generation of ALFs are used. The approximation error in the orbit computation is at a sub-millimeter level over two weeks and that the computed geoid 0.01 mm, with a maximum of 1 mm

  • 188.
    Ott, Eric
    et al.
    General Electric, Cincinnati, USA.
    Liu, XingboWest Virginia University, Morgantown, USA.Andersson, JoelHögskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).BI, ZhongnanChina Iron and Steel Research Institute, Beijing, China.Bockenstedt, KevinATI Specialty Materials, Monroe, USA.Dempster, IanWyman Gordon Forgings Inc., Houston, USA.Groh, JonGeneral Electric, Cincinnati, USA.Heck, KarlCarpenter Technology, Philadelphia, USA.Jablonski, PaulUnited States Department of Energy, Albany, USA.Kaplan, MaxPratt & Whitney, East Hartford, USA.Nagahama, DaisukeHonda Motor Co. Ltd.SaitamaJapan.Sudbrack, ChantalQuesTek Innovations, Evanston, USA.
    Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications2018Proceedings (redaktörskap) (Övrigt vetenskapligt)
    Abstract [en]

    This technical meeting will focus on Alloy 718 and Superalloys in this class relative to alloy and process development, production, product applications, trends and the development of advanced modeling tools. The symposium provides an opportunity for authors to present technical advancements relative to a broad spectrum of areas while assessing their impact on related fields associated with this critical alloy group. There are continuing innovations relative to these alloys as well as novel processing techniques which continue to extend applications in very challenging environments ranging from corrosion resistance in the deep sea to high-stressed space applications.

  • 189.
    Badgujar, Amol C.
    et al.
    Centre for Solar Energy Materials, ARCI, Hyderabad, India.
    Joshi, Shrikant V.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Dhage, Sanjay R.
    Mechanical and Aerospace Engineering Department, University of California, Los Angeles, USA .
    Process Parameter Impact on Selective Laser Ablation of Bilayer Molybdenum Thin Films for CIGS Solar Cell Applications2018Ingår i: Materials focus, ISSN 2169-429X, nr 4, s. 556-562Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cu(In,Ga)Se2 or CIGS absorber layers are a promising candidate for thin film solar cells, with efficiency exceeding 22% having already been demonstrated at the cell level and their commercialization been ramped up. Scribing by selective ablation to achieve monolithic integration is an essential step in CIGS module making to divide a large area cell into a series of inter-connected smaller cells. P1 scribing or electrical isolation of back contact is an essential part of the monolithic integration. Laser-induced scribing of Molybdenum (Mo) back contact of a CIGS solar cell is highly sensitive to process parameters like laser power, pulse duration, and pulse repetition frequency. The above parameters control the scribe width, heat affected zone and process residue directly or indirectly, thereby affecting electrical isolation and module performance. Influence of laser process parameters on scribing of a bilayer Mo thin film back contact has been investigated and is being reported. The scribes obtained employing various laser conditions were characterized for electrical isolation and analyzed by optical microscopy followed by profilometry. High-quality scribing, with a scribe width of 53 μm over a length of 300 mm, was achieved on a bilayer Mo thin film sputtered on a Soda lime glass substrate.

  • 190.
    Glorieux, Emile
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Riazi, Sarmad
    Department of Signals and Systems, Chalmers University of Technology, S-412 96 Gothenburg, Sweden.
    Lennartson, Bengt
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS). Department of Signals and Systems, Chalmers University of Technology, S-412 96 Gothenburg, Sweden.
    Productivity/energy optimisation of trajectories and coordination for cyclic multi-robot systems2018Ingår i: Robotics and Computer-Integrated Manufacturing, ISSN 0736-5845, E-ISSN 1879-2537, Vol. 49, s. 152-161Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The coordination of cyclic multi-robot systems is a critical issue to avoid collisions but also to obtain the shortest cycle-time. This paper presents a novel methodology for trajectory and coordination optimisation of cyclic multi-robot systems. Both velocity tuning and time delays are used to coordinate the robots that operate in close proximity and avoid collisions. The novel element is the non-linear programming optimisation model that directly co-adjusts the multi-robot coordination during the trajectory optimisation, which allows optimising these as one problem. The methodology is demonstrated for productivity/smoothness optimisation, and for energy efficiency optimisation. An experimental validation is done for a real-world case study that considers the multi-robot material handling system of a multi-stage tandem press line. The results show that the productivity optimisation with the methodology is competitive compared to previous research and that substantial improvements can be achieved, e.g. up to 50% smoother trajectories and 14% reduction in energy consumption for the same productivity. This paper addresses the current lack of systematic methodologies for generating optimal coordinated trajectories for cyclic multi-robot systems to improve the productivity, smoothness, and energy efficiency.

  • 191.
    Parsian, Amir
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Regenerative Chatter Vibration in Indexable Drills: Modeling and Simulation2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    An indexable insert drill is a drill which uses cutting inserts to make holes. Undesirable sound generated by this type of drill has always been considered as a problem in workshops. The focus of this thesis is to investigate the mechanism behind these vibrations, to model it and to provide guidelines for reducing the sound in future drill designs. Primary investigations show that the main sound generating mechanism is a self-induced vibration due to a coupled torsional-axial deformation in the drill which leads to the torsional-axial chatter vibration. The first step of simulating regenerative chatter vibrations in a drill is to model the static cutting forces. In this thesis, a model is proposed to estimate static cutting forces in indexable drills by dividing the cutting edges into small elements. Since, using this model, forces can be calculated separately on each insert, it is possibleto consider insert differences in estimation of the cutting loads. Torsional-axial coupling has been discussed and subsequently a time-domain model is proposed to simulate chatter vibrations. The resulting model is a system of delay differential equations with variable delays. The delay varies with time and is dependent on the state of the system. Variations in the time-delay, tool jump-out and backward motions of inserts have been included in the proposed time-domain simulation. A set of experiments was conducted to verify the model. Finally, a number of different strategies to alleviate the problem of chatter vibration are explored and their feasibilities for use in future products are discussed.

  • 192.
    Eshagh, Mehdi
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för Matematik, Data- och Lantmäteriteknik.
    Ashargie, Andenet
    Bedada, Tulu B.
    Regional recovery of gravity anomaly from the inversion of diagonal components of GOCE gravitational tensor: A Case Study in Ethiopia, Artificial Satellites2018Ingår i: Artificial Satellites : he Journal of Space Research Centre of Polish Academy of Sciences, E-ISSN 2083-6104, Vol. 53, nr 2, s. 55-74Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The tensor of gravitation is traceless as the gravitational field of the Earth is harmonic outside the Earth's surface. Therefore, summation of the 2nd-order horizontal derivatives on its diagonal components should be equal to the radial one but with the opposite sign. The gravity field can be recovered locally from either of them, or even their combination. Here, we use the in-orbit diagonal components of the gravitational tensor measured by the gravity field and steady stateocean circulation explorer (GOCE) mission for recovering gravity anomaly with a resolution of 1°×1° at sea level in Ethiopia. In order to solve the system of equations, derived after discretisation of integral equations, the Tikhonov regularisation is applied and the bias of thi sregularisation is estimated and removed from the estimated gravity anomalies. The errors of the anomalies are estimated and their significance of recovery from these diagonal components is investigated. Statistically, the difference between the recovered anomalies from each scenario isnot significant comparing to their errors. However, their joint inversion of the diagonal components improved the solution by about 1 mGal. Furthermore, the inversion processes arebetter stabilised when using errors of the input data compared with its exclusion, but at the penalty of degradation in accuracy of the estimates.

  • 193.
    Hattinger, Monika
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Researchers design conceptions of e-learning courses targeting industry practitioners’ competence needs2018Ingår i: International Journal of Continuing Engineering Education and Life-Long Learning, ISSN 1560-4624, E-ISSN 1741-5055, Vol. 28, nr 3-4, s. 235-253Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper addresses two overall challenges that concern university research teachers' professional identities when they make design plans for blended e-learning courses targeting practitioners' competence needs. Research teachers' are challenged by finding applicable learning material that matches practitioners' experiences and workplace knowledge demands. They are also challenged when they need to digitise engineering learning content such as virtual labs, and machine-related cases such as turning and milling aligning to workplace needs. Design plans used for campus education is argued to be insufficient meeting these challenges. Consequently, researchers' professional identities become vulnerable when they cross boundaries between university and industry practices. Results show that even if researchers are not trained for educational e-learning design they identify concepts for digitising cases and labs. By applying a work-integrated learning strategy, the courses integrate practical and theoretical tasks and cases collected from the manufacturing industry workplaces and thereby support competence development. © 2018 Inderscience Enterprises Ltd.

  • 194.
    Mishchenko, Andrii
    et al.
    Universidade Federal de Uberlândia – UFU, Grupo Centro para Pesquisa e Desenvolvimento de Processo de Soldagem – Laprosolda, Uberlândia, MG, Brasil.
    Scotti, Americo
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Universidade Federal de Uberlândia – UFU, Grupo Centro para Pesquisa e Desenvolvimento de Processo de Soldagem – Laprosolda, Uberlândia, MG, Brasil.
    Residual Stresses in Arc Welding: A Holistic Vision2018Ingår i: Soldagem & Inspeção, ISSN 0104-9224, E-ISSN 1980-6973, Vol. 23, nr 1, s. 93-112Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There are several examples in current literature where assumptions regarding residual stresses are made, yet rarely confirmed in practice. To validate this statement, this work presents a critical view on the subject through a bibliographic review. A series of conflicting results were found when researchers attempted, both experimentally and by simulation, to define, quantify, or even qualify, the individual effect of each factor on residual stress generation. It was concluded that the reason for this would be the lack of a holistic view to study the subject. Therefore, a diagram is proposed, which lists and classifies as primary and secondary the governing factors related to the generation of residual stresses, to facilitate the understanding of the effect of each factor. It was also observed a lack of harmonization in publications, both in symbology and in terminology, of the residual stress axes and components. Therefore, a symbology and terminology proposal, with the intention of facilitating the comprehension and transportability of results, is presented. Eventually, from this work is therefore expected a better understanding of the reasons for the literature assumptions to be not always confirmed in practice.

  • 195.
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Review of Weldability of Precipitation Hardening Ni- and Fe-Ni-Based Superalloys2018Ingår i: Proceedings of the 9th International Symposium on Superalloy 718 & Derivatives: Energy, Aerospace, and Industrial Applications / [ed] Ott, E., Liu, X., Andersson, J., Bi, Z., Bockenstedt, K., Dempster, I., Groh, J., Heck, K., Jablonski, P., Kaplan, M., Nagahama, D. and Sudbrack, C., Springer, 2018, s. 899-916Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fabrication and welding of structural components for the hot section of aero-engines continues to be of high importance to the manufacturing industry of aero-engines. This paper discusses and reviews the literature on hot cracking and strain age cracking, cracking phenomena that can occur during welding or subsequent heat treatment of precipitation hardened Ni- and Fe-Ni-based superalloys. The influence of chemical composition in terms of i.e. hardening elements and impurities, microstructure of base material and weld zone, together with welding processes and corresponding parameters and heat input are discussed and related to the cracking susceptibility of different nickel based superalloys.

  • 196.
    Bolmsjö, Gunnar
    et al.
    Linnaeus University, Växjö, Sweden.
    Ferreira Magalhães, Ana Catarina
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS). Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Cederqvist, L.
    SKB AB, Oskarshamn, Sweden.
    De Backer, Jeroen
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Robotic Friction Stir Welding of complex geometry and mixed materials2018Ingår i: 50th International Symposium on Robotics, ISR 2018, VDE Verlag GmbH , 2018, s. 35-41Konferensbidrag (Refereegranskat)
    Abstract [en]

    Friction stir welding (FSW) is a solid state process for joining materials which has demonstrated advantages compares with other methods which include joining of mixed materials, hard to weld alloys and consistent and high quality. This paper presents a study of robotic FSW initiated by Volvo Skövde plant to join an insert workpiece of extruded aluminium with a cylinder block of aluminium casting. A three-stage procedure was decided to determine the feasibility to apply robotic FSW. The stages included study of welding the mixed materials, weld along the complex joint line with holes and channels close to the joint, and finally welding the cylinder block. The results based on preliminary analysis indicate that the final tests were successful and the process is feasible for the challenging case study. However, further studies are recommended in order to identify the operating parameters window, tool design, and control of the process in order to optimize productivity and quality. © VDE VERLAG GMBH

  • 197.
    Pitonak, Martin
    et al.
    University of West Bohemia, NTIS—New Technologies for the Information Society, Faculty of Applied Sciences, Technicka´ 8, 306 14 Plzen, Czech Republic.
    Eshagh, Mehdi
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för Matematik, Data- och Lantmäteriteknik.
    Sprlak, Michal
    University of Newcastle, School of Engineering, Faculty of Engineering and Built Environment, Callaghan, NSW 2308, Australia.
    Tenzer, Robert
    The Hong Kong Polytechnic University, Department of Land Surveying and Geo-informatics, 181 Chatham Road South, Hung Hom, 999077 Kowloon, Hong Kong.
    Novak, Pavel
    University of West Bohemia, NTIS—New Technologies for the Information Society, Faculty of Applied Sciences, Technicka´ 8, 306 14 Plzen, Czech Republic.
    Spectral combination of spherical gravitational curvature boundary-value problems2018Ingår i: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 214, nr 2, s. 773-791Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Four solutions of the spherical gravitational curvature boundary-value problems can be exploited for the determination of the Earth’s gravitational potential. In this paper we discuss the combination of simulated satellite gravitational curvatures, that is, components of the third-order gravitational tensor, by merging these solutions using the spectral combination method. For this purpose, integral estimators of biased-and unbiased-types are derived. In numerical studies, we investigate the performance of the developed mathematical models for the gravitational field modelling in the area of Central Europe based on simulated satellite measurements. First, we verify the correctness of the integral estimators for the spectral downward continuation by a closed-loop test. Estimated errors of the combined solution are about eight orders smaller than those from the individual solutions. Second, we perform a numerical experiment by considering the Gaussian noise with the standard deviation of 6.5 x 10(-17) m(-1) s(-2) in the input data at the satellite altitude of 250 km above the mean Earth sphere. This value of standard deviation is equivalent to a signal-to-noise ratio of 10. Superior results with respect to the global geopotential model TIM-r5 (Brockmann et al. 2014) are obtained by the spectral downward continuation of the vertical-vertical-vertical component with the standard deviation of 2.104 m(2) s(-2), but the root mean square error is the largest and reaches 9.734 m(2) s(-2). Using the spectral combination of all gravitational curvatures the root mean square error is more than 400 times smaller but the standard deviation reaches 17.234 m(2) s(-2). The combination of more components decreases the root mean square error of the corresponding solutions while the standard deviations of the combined solutions do not improve as compared to the solution from the vertical-vertical-vertical component. The presented method represents a weight mean in the spectral domain that minimizes the root mean square error of the combined solutions and improves standard deviation of the solution based only on the least accurate components.

  • 198.
    Kisielewicz, Agnieszka
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Sikström, Fredrik
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Christiansson, Anna-Karin
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Ancona, Antonio
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS).
    Spectroscopic monitoring of laser blown powder directed energy deposition of Alloy 7182018Ingår i: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 25, s. 418-425Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Experimental explorations of a spectrometer system used for in-process monitoring of the laser blown powder directed energy deposition of Alloy 718 is presented. Additive manufacturing of metals using this laser process experiences repeated heating and cooling cycles which will influence the final microstructure and chemical composition at every given point in the built. The spectrometer system disclosed, under certain process conditions, spectral lines that indicate vaporisation of chromium. Post process scanning electron microscope energy dispersive spectroscopy analysis of the deposited beads confirmed a reduction of chromium. Since the chromium concentration in Alloy 718 is correlated to corrosion resistance, this result encourages to further investigations including corrosion tests.

  • 199.
    Hosseini, Vahid
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Innovatum AB Trollhättan,Trollhättan,Sweden.
    Thuvander, Mattias
    Chalmers University of Technology, Department of Physics, Gothenburg,Sweden.
    Wessman, Sten
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Karlsson, Leif
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Spinodal Decomposition in Functionally Graded Super Duplex Stainless Steel and Weld Metal2018Ingår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 49A, nr 7, s. 2803-2816Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Low-temperature phase separations (T < 500 °C), resulting in changes in mechanical and corrosion properties, of super duplex stainless steel (SDSS) base and weld metals were investigated for short heat treatment times (0.5 to 600 minutes). A novel heat treatment technique, where a stationary arc produces a steady state temperature gradient for selected times, was employed to fabricate functionally graded materials. Three different initial material conditions including 2507 SDSS, remelted 2507 SDSS, and 2509 SDSS weld metal were investigated. Selective etching of ferrite significantly decreased in regions heat treated at 435 °C to 480 °C already after 3 minutes due to rapid phase separations. Atom probe tomography results revealed spinodal decomposition of ferrite and precipitation of Cu particles. Microhardness mapping showed that as-welded microstructure and/or higher Ni content accelerated decomposition. The arc heat treatment technique combined with microhardness mapping and electrolytical etching was found to be a successful approach to evaluate kinetics of low-temperature phase separations in SDSS, particularly at its earlier stages. A time-temperature transformation diagram was proposed showing the kinetics of 475 °C-embrittlement in 2507 SDSS.

  • 200.
    Sandström, Kristina
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för Industriell ekonomi, Elektro- och Maskinteknik.
    Sjögren, Karin
    Johansson, Kristina
    Högskolan Väst, Institutionen för individ och samhälle, Avdelningen för psykologi, pedagogik och sociologi.
    Students Sense of belonging and social media2018Ingår i: VILÄR Abstraktbok / [ed] Kristina Johansson, Trollhättan: Högskolan Väst , 2018, s. 8-8Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Students who participate in a work-integrated learning (WIL) program - such as Cooperative Education during their university studies are often better prepared for the labour market compared to students who do not receive discipline specific practical experience. But does this better preparedness come with a price? Students who participate in WIL programs compared to non-WIL students often have less access to social support networks and the university community due to their alternating academic and work terms.There is reason to believe that the construct of belonging may have especially important implications among university students. There has been growing attention in recent years to mental illness amongst post-secondary students, particularly during their first few years of university study (Conley, Kirsch, Dickson, & Bryant,2014; Storrie, Ahern, & Tuckett, 2010). Research suggests that a sense of school belonging among university students may help buffer the stress associated with the transition to university (Brunwasser, 2012). Pittman and Richmond (2008), for example, found that students who experienced a positive change in their sense of university belonging throughout their first year tended to experience a drop in levels of anxiety and depression related internalizing behavioural problems. A study by Friedlander, Reid, Shupak, and Cribbie (2007), found that when compared to parental social support, higher levels of perceived social support from friends better predicted a healthy social, emotional, and overall adjustment to university among first-year university students. While evidence points to a relation between peer support and sense of belonging and university students' academic and psychological outcomes, such measures do not account for the impact of Social Media (SM) use. This study aims to understand and describe students perception on the role social media play in sense of belonging and peer support and what the relationship(s) arebetween sense of belonging, peer support, social media and well-being. Is really work integrated learning models a way of supporting the transition between H.E and W.L or are we creating other barriers that's needs to be overcome? This study comprise of a questionnaire and focus groups interviews. 164 individuals completed a 30-45 minutes long questionnaire in English, in the end of the questionnaire the students could choose to say yes to participate in a focus group, and it resulted in five focus groups including 15 students representing all four faculties. Preliminary results indicate that the students emphasize the importance of peer-support during both their academic studies and work periods. The Students seem to find solutions trying to achieve this through SM, it becomes a natural tool and creates a platform for students to connect and support each other virtually. In the presentation we will illustrate more results.

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