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  • 1.
    Alwaeli, Laith
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Sjukvårdens behov av kurser inom verksamhetsutveckling2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 2.
    Asala, G.
    et al.
    University of Manitoba, Winnipeg, R3T 5V6, Canada .
    Andersson, Joel
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Ojo, Olanrewaj A.
    University of Manitoba, Winnipeg, R3T 5V6, Canada .
    Precipitation behavior of gamma′ precipitates in the fusion zone of TIG welded ATI 718Plus®2016In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 87, no 9-12, p. 2721-2729Article in journal (Refereed)
    Abstract [en]

    The precipitation behavior of the main strengthening phase, γ′ precipitates, in ATI 718Plus® superalloy after Tungsten Inert Gas (TIG) welding and postweld heat treatments has been studied. In contrast to electron beam welding, where no γ′ precipitates are reported to form in the as-welded condition, analytical transmission electron microscopy study in this work revealed the formation of γ′ precipitates after the TIG welding, albeit in a non-uniform distribution manner. This is attributable to a more extensive elemental microsegregation that occurred into the interdendritic liquid and slower cooling rate during the TIG welding, which also induced the formation of interdendritic Nb-rich Laves phase particles and MC-type carbides. Theoretical calculations were performed to study the influence of Nb microsegregation, on both the kinetics and extent of γ′ precipitation, and the results agree with experimental observations. It is found that the precipitation kinetics, and not the extent of γ′ precipitate formation in the fusion zone, during postweld heat treatments is affected by the micro-segregation of Nb that produced Laves phase particles during the weld solidification.

  • 3.
    Asala, G.
    et al.
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, Canada.
    Khan, A. K.
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, Canada.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Mechanical Engineering. University West, Department of Engineering Science, Division of Welding Technology.
    Ojo, O. A.
    University of Manitoba, Department of Mechanical Engineering, Winnipeg, Canada.
    Microstructural Analyses of ATI 718Plus® Produced by Wire-ARC Additive Manufacturing Process2017In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 48A, no 9, p. 4211-4228Article in journal (Refereed)
    Abstract [en]

    A detailed microstructural study of ATI 718Plus superalloy produced by the wire-arc additive manufacturing (WAAM) process was performed through the use of scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron probe micro-analysis (EPMA), and electron backscatter diffraction (EBSD). Extensive formation of eutectic solidification microconstituents including Laves and MC-type carbide phases, induced by micro-segregation, are observed in the build of the alloy in the as-deposited condition. Notwithstanding the significant segregation of niobium (Nb), which has been reported to promote the formation of the delta-phase in ATI 718Plus, only eta-phase particles are observed in the deposit. Excessive precipitation of eta-phase particles is found to be linked to Laves phase particles that are partially dissolved in the deposit after post-deposition heat treatment (PDHT). The EBSD analysis shows a high textured build in the aOE (c) 100 > directions with only a few misoriented grains at the substrate-deposit boundary and the top of the deposit. Investigation on the hardness of the build of the alloy, in the as-deposited condition, showed a softened zone about 2 mm wide at the deposited metal heat affected zone (DMHAZ), which has not been previously reported and potentially damaging to the mechanical properties. An extensive analysis with the use of both microstructural characterization tools and theoretical calculations shows that the DMHAZ has the lowest volume fraction of strengthening precipitates (gamma’ and gamma aEuro(3)) in terms of their number density, which therefore induces the observed softness. Delayed re-precipitation kinetics and the extent of the precipitation of gamma’ and gamma aEuro(3) in the DMHAZ which is related to the diffusion of segregated solute elements from the interdendritic regions are attributed to this phenomenon. The microstructural analyses discussed in this work are vital to adequate understanding of properties of ATI 718Plus produced by the additive manufacturing process technique.

  • 4.
    Broberg, Patrik
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Surface crack detection in welds using thermography2013In: NDT & E international, ISSN 0963-8695, E-ISSN 1879-1174, Vol. 57, p. 69-73Article in journal (Refereed)
    Abstract [en]

    Thermography is today used within non-destructive testing for detecting several different types of defects. The possibility for using thermography for detecting surface cracks in welded metal plates has here been investigated. During testing the weld is illuminated using a high power infrared light source. Due to surface cracks acting like black bodies, they will absorb more energy than the surrounding metal and can be identified as a warmer area when imaged using an infrared camera. Notches as well as real longitudinal cold cracks in a weld are investigated using the presented method. The results show that thermography is promising as a method for detection cracks open to the surface.

  • 5.
    Broberg, Patrik
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Runnemalm, Anna
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Sjödahl, Mikael
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Improved Corner Detection by Ultrasonic Testing using Phase Analysis2013In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 53, no 2, p. 630-634Article in journal (Refereed)
    Abstract [en]

    In ultrasonic testing, corners are used for sensitivity calibration in the form of notches, for measuring the sound velocity in the material, and as known reference points during testing. A 90° corner will always reflect incoming waves in the opposite direction due to a double reflection and therefore give a strong echo. This article presents a method for separating the echo from a corner from other echoes and more accurately find the position of the corner. The method is based on analysing the phase of the reflected signal. The proposed method was tested on a steel calibration block and the width of the indication was reduced by up to 50% compared to the amplitude signal. This results in a more accurate positioning of the corner. Using the phase instead of the amplitude will also improve the reliability, since reflections other than from corners will disappear.

  • 6.
    Chen, Y.
    et al.
    University of Manchester, School of Materials, Manchester, United Kingdom.
    Zhao, X.
    Shanghai Jiao Tong University, Shanghai Key Laboratory of Advanced High-Temperature Materials and Precision Forming, Shanghai, China .
    Dang, Y.
    University of Manchester, School of Materials, Manchester, United Kingdom.
    Xiao, Ping
    University of Manchester, School of Materials, Manchester, United Kingdom.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Characterization and understanding of residual stresses in a NiCoCrAlY bond coat for thermal barrier coating application2015In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 94, p. 1-14Article in journal (Refereed)
    Abstract [en]

    The residual stresses in a NiCoCrAlY bond coat deposited on a Ni-base superalloy substrate after oxidation at 1150 °C were studied by X-ray diffraction using the sin2Ψ technique. The stresses were found to be tensile; they first increased and then decreased with oxidation time. High temperature stress measurement indicated that the stress developed and built up upon cooling, predominantly within the temperature range from 1150 °C to 600 °C. Microstructural examination suggested that, due to the limited penetration depth into the bond coat, the X-ray only probed the stress in a thin surface layer consisting of the single γ-phase formed through Al depletion during oxidation. Quantitative high temperature X-ray diffraction analysis revealed that, above 600 °C, the volume fraction of the β-phase in the bond coat increased with decreasing temperature. The mechanisms of stress generation in the bond coat were examined and are discussed based on the experiments designed to isolate the contribution of possible stress generation factors. It was found that the measured bond coat stresses were mainly induced by the volume change of the bond coat associated with the precipitation of the β-phase upon cooling.

  • 7.
    Choquet, Isabelle
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Javidi-Shirvan, Alireza
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Nilsson, Håkan
    Chalmers University of Technology, Department of Applied Mechanics, .
    Magnetic field models for high intensity arcs, applied to welding: A comparison between three different formulations2013In: ASM Proceedings of the International Conference: Trends in Welding Research 2013, Chicago, IL: ASM International, 2013, p. 876-885Conference paper (Refereed)
    Abstract [en]

    Most simulation studies done to deeper understand high-intensity welding arcs address axi-symmetric configurations and use the electric potential formulation. This formulation involves the assumption of a one-dimensional magnetic field. The assumption is justified in its original frame: rather long arcs (about 10 mm), and when the electrode tip is excluded from the computational domain. However, arcs applied to welding are shorter, and the electrode geometry is important to take into account. The present work questions the assumption of a one-dimensional magnetic field for simulating short welding arcs. We have compared three different approaches for modeling the magnetic field: three-dimensional, two-dimensional axi-symmetric, and the electric potential formulation. These models have been applied to water cooled anode Gas Tungsten Arc Welding (GTAW) test cases with truncated conical electrode tip (tip radius of 0.5 and 0.2 mm) and various arc lengths (2, 3 and 5 mm). For the axi-symmetric cases studied in the present work, the three- and two-dimensional models give exactly the same results. The one-dimensional simplification of the magnetic field turns out to have a significant unfavorable effect on the simulation results. For axi-symmetric welding applications, it is argued that the two-dimensional axi-symmetric formulation should be used. Copyright © 2013 ASM International® All rights reserved.

  • 8.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering. University West, Department of Engineering Science, Research Enviroment Production Technology West. Treibacher AG, Austria.
    Feedstock for SPS and SPPS: Properties and Processing2016Conference paper (Other academic)
  • 9.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Janikowski, Wysomir
    University of Manchester.
    Pala, Zdenek
    Academy of Sciences of the Czech Republic, Institute of Plasma Physics.
    Vilémová, Monica
    Academy of Sciences of the Czech Republic, Institute of Plasma Physics.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Impact of Impurity Content on the Sintering Resistance and Phase Stability of Dysprosia- and Yttria-Stabilized Zirconia Thermal Barrier Coatings2014In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 23, no 1-2, p. 160-169Article in journal (Refereed)
    Abstract [en]

    Dysprosia-stabilized zirconia (DySZ) is a promising candidate to replace yttria-stabilized zirconia (YSZ) as a thermal barrier coating due to its lower inherent thermal conductivity. It is also suggested in studies that DySZ may show greater stability to high temperature phase changes compared to YSZ, possibly allowing for coatings with extended lifetimes. Separately, the impurity content of YSZ powders has been proven to influence high-temperature sintering behavior. By lowering the impurity oxides within the spray powder, a coating more resistant to sintering can be produced. This study presents both high purity and standard purity dysprosia and YSZ coatings and their performance after a long heat treatment. Coatings were produced using powder with the same morphology and grain size; only the dopant and impurity content were varied. Samples have been heat treated for exposure times up to 400 h at a temperature of 1150 °C. Samples were measured for thermal conductivity to plot the evolution of coating thermal properties with respect to exposure time. Thermal conductivity has been compared to microstructure analysis and porosity measurement to track structural changes. Phase analysis utilizing x-ray diffraction was used to determine differences in phase degradation of the coatings after heat treatment. © 2013 ASM International.

  • 10.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Janikowski, Wyszomir
    University of Mancheste.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Impact of impurity content on the sintering resistance of dysprosia and yttria stabilised zirconia thermal barrier coatings2013In: Proceedings of the International Thermal Spray Conference / [ed] Editor: Rogerio S. Lima, Arvind Agarwal, Margaret M. Hyland, Yuk-Chiu Lau, Georg Mauer, André McDonald, and Filofteia-Laura, ASM International, 2013, p. 557-563Conference paper (Refereed)
    Abstract [en]

    Dysprosia stabilised zirconia (DySZ) is a promising candidate to replace yttria stabilised zirconia (YSZ) as a thermal barrier coating due to its lower inherent thermal conductivity. It is also suggested in studies that DySZ may show greater stability to high temperature phase changes compared to YSZ, possibly allowing for coatings with extended lifetimes. Separately, the impurity content of YSZ powders has been proven to influence high temperature sintering behaviour. By lowering the impurity oxides within the spray powder, a coating more resistant to sintering can be produced. This study presents both high purity and standard purity dysprosia and yttria stabilised zirconia coatings and their performance after a long heat treatment. Coatings were produced using powder with the same morphology and grain size; only the dopant and impurity content were varied. Samples have been heat treated for exposure times up to 400 hours at a temperature of 1150°C. Samples were subsequently measured for thermal conductivity to plot the evolution of coating thermal properties with respect to exposure time. Thermal conductivity has been compared to microstructure analysis and porosity measurement to track structural changes due to sintering.

  • 11.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Tang, Zhaolin
    Northwest Mettech Corp., Vancouver, Canada.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Influence of Bond Coat Surface Roughness on the Structure of Axial Suspension Plasma Spray Thermal Barrier Coatings - Thermal and Lifetime Performance2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 268, no April, p. 15-23Article in journal (Refereed)
  • 12.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    VanEvery, Kent
    Progressive Surface, Grand Rapids, MI 49512, USA .
    Snyder, Todd
    Progressive Surface, Grand Rapids, MI 49512, USA.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Thermal Conductivity Analysis and Lifetime Testing of Suspension Plasma-Sprayed Thermal Barrier Coatings2014In: Coatings, ISSN 2079-6412, Vol. 4, no 3, p. 630-650Article in journal (Refereed)
    Abstract [en]

    Suspension plasma spraying (SPS) has become an interesting method for the production of thermal barrier coatings for gas turbine components. The development of the SPS process has led to structures with segmented vertical cracks or column-like structures that can imitate strain-tolerant air plasma spraying (APS) or electron beam physical vapor deposition (EB-PVD) coatings. Additionally, SPS coatings can have lower thermal conductivity than EB-PVD coatings, while also being easier to produce. The combination of similar or improved properties with a potential for lower production costs makes SPS of great interest to the gas turbine industry. This study compares a number of SPS thermal barrier coatings (TBCs) with vertical cracks or column-like structures with the reference of segmented APS coatings. The primary focus has been on lifetime testing of these new coating systems. Samples were tested in thermo-cyclic fatigue at temperatures of 1100 °C for 1 h cycles. Additional testing was performed to assess thermal shock performance and erosion resistance. Thermal conductivity was also assessed for samples in their as-sprayed state, and the microstructures were investigated using SEM

  • 13.
    Eggertsen, P. -A
    et al.
    University of Technology, Div. of Material and Computational Mechanics, Dept. of Applied Mechanics Chalmers.
    Mattiasson, Kjell
    University of Technology, Div. of Material and Computational Mechanics, Dept. of Applied Mechanics Chalmers.
    Larsson, Mats
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    A comprehenisve analysis of benchmark 4: Pre-strain effect on springback of 2D draw bending2011In: AIP Conference Proceedings, Seoul, 2011, Vol. 1383, p. 1064-1071Conference paper (Refereed)
    Abstract [en]

    In order to be able to form high strength steels with low ductility, multi-step forming processes are becoming more common. Benchmark 4 of the NUMISHEET 2011 conference is an attempt to imitate such a process. A DP780 steel sheet with 1.4 mm thickness is considered. In order to understand the pre-strain effect on subsequent forming and springback, a 2D draw-bending is considered. Two cases are studied: one without prestrain and one with 8% pre-stretching. The draw-bending model is identical to the "U-bend" problem of the NUMISHEET'93 conference. The purpose of the benchmark problem is to evaluate the capability of modern FE-methods to simulate the forming and springback of these kinds of problems. The authors of this article have previously made exhaustive studies on material modeling in applications to sheet metal forming and springback problems, [1],[2],[3]. Models for kinematic hardening, anisotropic yield conditions, and elastic stiffness reduction have been investigated. Also procedures for material characterization have been studied. The material model that mainly has been used in the current study is based on the Banabic BBC2005 yield criterion, and a modified version of the Yoshida-Uemori model for cyclic hardening. This model, like a number of other models, has been implemented as User Subroutines in LS-DYNA. The effects of various aspects of material modeling will be demonstrated in connection to the current benchmark problems. The provided material data for the current benchmark problem are not complete in all respects. In order to be able to perform the current simulations, the authors have been forced to introduce a few additional assumptions. The effects of these assumptions will also be discussed. © 2011 American Institute of Physics.

  • 14.
    Ekström, Johanna
    et al.
    University West, Department of Engineering Science.
    Emanuelsson, Stefan
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Förstudie till implementering av papperslös verkstad2012Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Under sommaren 2012 genomfördes ett examensarbete på Siemens Industrial Turbo­mach­inery AB i Trollhättan gällande möjligheterna att införa pappers­lös verkstad. Syftet med examensarbetet var att kartlägga möjligheterna att minska administrativ hant­ering av produktions­orderkort och öka realtidsuppdatering. För att av­gränsa studien avsåg examens­arbetet endast flödet av produk­tions­­­order­kort ifrån plan­er­ings­avdelningen genom två pro­duk­tions­grupper och vidare in på gods­­­­avdel­ningen.

    För att kartlägga flödet för den manuella hanteringen av produktionsorderkort upprättades värdeflödesanalyser. Dessutom genomfördes ett studiebesök på Volvo Aero Corporation för att se hur ett annat företag har gjort för att eliminera elektronisk produk­tionsorder. Utifrån värdeflödesanalyserna och studiebesöket identifierades tre frågeställ­ningar vilka an­sågs vara betydelsefulla för att kunna införa elektronisk produk­tions­order. Dessa var huru­vida affärssystemet klarar av att hantera införande av elektronisk produk­tions­order, hur spårbarheten av material skall bibehållas samt hur godsavdelningen skall få information om var detaljer skall förflyttas. För att besvara dessa frågor genomfördes 15 inter­vjuer med per­sonal från Siemens Industrial Turbo­machinery i Trollhättan, med per­sonal från huvud­kontoret i Finspång samt med personal från systemutvecklingsföretaget Else AB.

    Informationen från alla intervjuer samt studiebesöket på Volvo Aero Corporation belyser möjligheterna och problemen med att eliminera produktionsorderkorten och samman­ställ­des i en utvärdering. Denna utvärdering ligger till grund för kartläggningen av det fram­tida tillståndet, vilken visar ett tänkbart arbetssätt när produktions­order­korten tagits bort och ersatts med elek­tronisk produktions­order. Det som huvud­sakligen belyses i det framtida tillståndet är att affärssystemet är förberett för elek­tronisk produk­tions­order, dock rekom­men­deras införande av Warehouse Management System samt ett transportssystem. För att under­­lätta implementering av elektronisk produktionsorder skulle införande av ett web­baserat användargränssnitt vara lämpligt.

  • 15.
    Ericson Öberg, Anna
    et al.
    Chalmers Tekniska Högskola.
    Hammersberg, Peter
    Chalmers Tekniska Högskola.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    The right evaluation method - an enabler for process improvement2013Conference paper (Other academic)
    Abstract [en]

    This paper aims at describing the procedure where an alternative evaluation process was developed to support the improvement of both welding and weld quality evaluation. Welded structures are important when striving for reduced fuel consumption due to vehicle weight. Hence good control of the fabrication process is critical to keep welding performance on target, avoiding waste in terms of added weight and overproduction. The resulting distribution of weld weight has shown to be an important control parameter in the sense of keeping cost down.

    To identify the causes for deviations between actual and theoretical weld weight, information about the weld was needed. The currently used evaluation method showed not to be capable of giving the information needed. It was necessary to know the throat size as well as weld geometry. The current evaluation method introduced more variation due to the measurement than the actual fabrication process itself, leading to drift of process target and overproduction.

    To fulfil the need of information, that different functions within the company had, a PULL-approach was used. The information need, information presentation and sequence were outlined for each information receiver individually. An alternative measurement method was developed and named WIA – Weld Impression Analysis. The method consists of two parts; creating the replica and analysing the shape in an image analysis program.

    The method was tested to see if it was capable of delivering accurate and precise measurements, satisfying repeatability and reproducibility requirements for this particular situation. A thorough measurement system analysis was carried out. The measurement system assigned 98.98% of the total variation to part-to-part variation corresponding to long-term process variation. The variation that stems from taking the impressions and preparing them was as well investigated, also showing satisfying results. Finally it was investigated if the impressions reflect the true shape of the welds accurately. The results showed a tendency of slightly higher cross sectional areas in the range of 0-3 %. This however indicated that the accuracy of the measurement system was sufficient for its purpose.

    The PULL-approach generated a sufficient method which enabled the possibility to perform process improvement and gain large production cost savings.

  • 16.
    Ganvir, Ashish
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Characterization of Microstructure and Thermal Properties of YSZ Coatings Obtained by Axial Suspension Plasma Spraying (ASPS)2015In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 7, p. 1195-1204Article in journal (Refereed)
    Abstract [en]

    The paper aims at demonstrating various microstructures which can be obtained using the suspension spraying technique and their respective significance in enhancing the thermal insulation property of a thermal barrier coating. Three different types of coating microstructures are discussed which were produced by the Axial Suspension Plasma Spraying. Detailed characterization of coatings was then performed. Optical and scanning electron microscopy were utilized for microstructure evaluations; x-ray diffraction for phase analysis; water impregnation, image analysis, and mercury intrusion porosimetry for porosity analysis, and laser flash analysis for thermal diffusivity measurements were used. The results showed that Axial Suspension Plasma Spraying can generate vertically cracked, porous, and feathery columnar-type microstructures. Pore size distribution was found in micron, submicron, and nanometer range. Higher overall porosity, the lower density of vertical cracks or inter-column spacing, and higher inter-pass porosity favored thermal insulation property of the coating. Significant increase in thermal diffusivity and conductivity was found at higher temperature, which is believed to be due to the pore rearrangement (sintering and pore coarsening). Thermal conductivity values for these coatings were also compared with electron beam physical vapor deposition (EBPVD) thermal barrier coatings from the literature and found to be much lower. © 2015 ASM International

  • 17.
    Ganvir, Ashish
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Joshi, Shrikant
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Vilemova, Monika
    IPP.
    Pala, Zdenek
    IPP.
    Influence of Microstructure on Thermal Properties of Axial Suspension Plasma-Sprayed YSZ Thermal Barrier Coatings2016In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 25, no 1-2, p. 202-212Article in journal (Refereed)
    Abstract [en]

    Suspension plasma spraying is a relatively new thermal spaying technique to produce advanced thermal barrier coatings (TBCs) and enables production of coatings with a variety of structures—highly dense, highly porous, segmented, or columnar. This work investigates suspension plasma-sprayed TBCs produced using axial injection with different process parameters. The influence of coating microstructure on thermal properties was of specific interest. Tests carried out included microstructural analysis, phase analysis, determination of porosity, and pore size distribution, as well as thermal diffusivity/conductivity measurements. Results showed that axial suspension plasma spraying process makes it possible to produce various columnar-type coatings under different processing conditions. Significant influence of microstructural features on thermal properties of the coatings was noted. In particular, the process parameter-dependent microstructural attributes, such as porosity, column density, and crystallite size, were shown to govern the thermal diffusivity and thermal conductivity of the coating.

  • 18.
    Ganvir, Ashish
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Vilemova, Monika
    IPP Prague, Czech Republic.
    Pala, Zdenek
    IPP Prague, Czech Republic.
    Influence of Microstructure on Thermal Properties of Columnar Axial Suspension Plasma Sprayed Thermal Barrier Coatings2015In: Proceedings of the International Thermal Spray Conference: International Thermal Spray Conference and Exposition, ITSC 2015; Long Beach; United States; 11 May 2015 through 14 May 2015 / [ed] A. McDonald, A. Agarwal, G. Bolelli, A. Concustell, Y.-C. Lau, F.-L. Toma, E. Turunen, C. Widener, ASM International, 2015, p. 498-505Conference paper (Refereed)
    Abstract [en]

    Suspension Plasma Spraying is a relatively new thermal spraying technique to produce advanced thermal barrier coatings. This technique enables the production of a variety of structures from highly dense, highly porous, segmented or columnar coatings. In this work a comparative study is performed on six different suspension plasma sprayed thermal barrier coatings which were produced using axial injection and different process parameters. The influence of coating morphology and porosity on thermal properties was of specific interest. Tests carried out include microstructural analysis with SEM, phase analysis using XRD, porosity calculation using Archimedes experimental setup, pore distribution analysis using mercury infiltration technique and thermal diffusivity/conductivity measurements using laser flash analysis. The results showed that columnar and cauliflower type coatings were produced by axial suspension plasma spraying process. Better performance coatings were produced with relatively higher overall energy input given during spraying. Coatings with higher energy input, lower thickness and wider range of submicron and nanometer sized pores distribution showed lower thermal diffusivity and hence lower thermal conductivity. Also, in-situ heat treatment did not show dramatic increase in thermal properties.

  • 19.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Design of Microstructures in Thermal Barrier Coatings: A Modelling Approach2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Plasma sprayed Thermal Barrier Coating systems (TBCs) are commonly used for thermal protection of components in modern gas turbine application such as power generation, marine and aero engines. The material that is most commonly used in these applications is Yttria Stabilized Zirconia (YSZ) because of this ceramic’s favourable properties, such as low thermal conductivity, phase stability to high temperature, and good erosion resistance. The coating microstructures in YSZ coatings are highly heterogeneous, consisting of defects such as pores and cracks of different sizes which determine the coating’s final thermal and mechanical properties, and the service lives of the coatings. Determination of quantitative microstructure–property correlations is of great interest as experimental procedures are time consuming and expensive.

    This objective of this thesis work was to investigate the relationships between coating microstructure and thermal-mechanical properties of TBCs, and to utilise these relationships to design an optimised microstructure to be used for next generation TBCs. Simulation technique was used to achieve this goal. Important microstructural parameters influencing the performance of TBCs were identified and coatings with the identified microstructural parameters were designed, modelled and experimentally verified. TBCs comprising of large globular pores with connected cracks inherited within the coating microstructure were shown to have significantly enhanced performance. Low thermal conductivity, low Young‘s modulus and high lifetime were exhibited by these coatings. The modelling approach described in this work can be used as a powerful tool to design new coatings as well as to achieve optimised microstructures.

  • 20.
    Gupta, Mohit Kumar
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Design of Thermal Barrier Coatings: A modelling approach2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Atmospheric plasma sprayed (APS) thermal barrier coatings (TBCs) are commonly used for thermal protection of components in modern gas turbine application such as power generation, marine and aero engines. TBC is a duplex material system consisting of an insulating ceramic topcoat layer and an intermetallic bondcoat layer. TBC microstructures are highly heterogeneous, consisting of defects such as pores and cracks of different sizes which determine the coating's final thermal and mechanical properties, and the service lives of the coatings. Failure in APS TBCs is mainly associated with the thermo-mechanical stresses developing due to the thermally grown oxide (TGO) layer growth at the topcoat-bondcoat interface and thermal expansion mismatch during thermal cycling. The interface roughness has been shown to play a major role in the development of these induced stresses and lifetime of TBCs.The objective of this thesis work was two-fold for one purpose: to design an optimised TBC to be used for next generation gas turbines. The first objective was to investigate the relationships between coating microstructure and thermal-mechanical properties of topcoats, and to utilise these relationships to design an optimised morphology of the topcoat microstructure. The second objective was to investigate the relationships between topcoat-bondcoat interface roughness, TGO growth and lifetime of TBCs, and to utilise these relationships to design an optimal interface. Simulation technique was used to achieve these objectives. Important microstructural parameters influencing the performance of topcoats were identified and coatings with the feasible identified microstructural parameters were designed, modelled and experimentally verified. It was shown that large globular pores with connected cracks inherited within the topcoat microstructure significantly enhanced TBC performance. Real topcoat-bondcoat interface topographies were used to calculate the induced stresses and a diffusion based TGO growth model was developed to assess the lifetime. The modelling results were compared with existing theories published in previous works and experiments. It was shown that the modelling approach developed in this work could be used as a powerful tool to design new coatings and interfaces as well as to achieve high performance optimised morphologies.

  • 21.
    Haraldsson, Jenny
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Karlsson, Christian
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Ersättning av skruvförband till VE152012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Fordonsindustrin strävar efter ständiga förbättringar på transmissionssystem inom exempelvis hållfasthet och viktminskning. För att reducera vikten på växellådshuset (VE15) har alternativ till det befintliga skruvförbandet granskats. Målet med examensarbetet var att välja två olika fogningsmetoder, en inom svetsning och en inom limning. De valda fogningsmetoderna jämfördes med det befintliga skruvförbandet utifrån bland annat viktminskningspotential och hållfasthet.

    Information inom svetsning, limning, skruvförband och aluminium införskaffades med hjälp av kvalificerade databaser, vetenskapliga artiklar samt rådfrågning av sakkunniga inom respektive område. Utifrån de valda fogningsmetoderna, friktionsomrörningssvetsning (FSW) och epoxi, idégenererades utformning av flänsen.

    Vid användning av FSW som fogningsmetod reducerades vikten på VE15 med 13,7 % och med epoxi var viktminskningen 25,5 %, i jämförelse med skruvförbandet. Då mekaniken i växellådan genererar krafter på flänsen är hållfasthetsegenskaper hos fogningsmetoderna viktiga. Epoxi, FSW och skruvförbandet klarar belastningarna med god marginal. Med avseende på bland annat hållfasthet, vikt och miljö/hälsopåverkan valdes FSW som potentiell ersättare av skruvförbandet på VE15. Valet utfördes med en konceptvägningsmatris.

  • 22.
    Javidi Shirvan, Alireza
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Modelling of Electric Arc Welding: arc-electrode coupling2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Arc welding still requires deeper process understanding and more accurateprediction of the heat transferred to the base metal. This can be provided by CFD modelling.Most works done to model arc discharge using CFD consider the arc corealone. Arc core simulation requires applying extrapolated experimental data asboundary conditions on the electrodes. This limits the applicability. To become independent of experimental input the electrodes need to be included in the arcmodel. The most critical part is then the interface layer between the electrodesand the arc core. This interface is complex and non-uniform, with specific physicalphenomena.The present work reviews the concepts of plasma and arc discharges that areuseful for this problem. The main sub-regions of the model are described, andtheir dominant physical roles are discussed.The coupled arc-electrode model is developed in different steps. First couplingsolid and fluid regions for a simpler problem without complex couplinginterface. This is applied to a laser welding problem using the CFD softwareOpenFOAM. The second step is the modelling of the interface layer betweencathode and arc, or cathode layer. Different modelling approaches available inthe literature are studied to determine their advantages and drawbacks. One ofthem developed by Cayla is used and further improved so as to satisfy the basicprinciples of charge and energy conservation in the different regions of thecathode layer. A numerical procedure is presented. The model, implementedin MATLAB, is tested for different arc core and cathode conditions. The maincharacteristics calculated with the interface layer model are in good agreementwith the reference literature. The future step will be the implementation of theinterface layer model in OpenFOAM.

  • 23.
    Javidi Shirvan, Alireza
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Choquet, Isabelle
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Nilsson, Håkan
    Chalmers University of technology, Applied Mechanics.
    Numerical modelling of shielding gas flow and heat transfer in laser welding process2012In: Proceedings of the 5th International Swedish Production Symposium, SPS12 / [ed] The Swedish Production Academy on October 2012, Linköping, 2012, , p. 7p. 1-7Conference paper (Refereed)
    Abstract [en]

    In the present work a three-dimensional model has been developed to study shieldinggas flow and heat transfer in a laser welding process using computational fluid dynamics.This investigation was motivated by problems met while using an optical system totrack the weld path. The aim of this study was to investigate if the shielding gas flowcould disturb the observation area of the optical system. The model combines heatconduction in the solid work piece and thermal flow in the fluid region occupied by theshielding gas. These two regions are coupled through their energy equations so asto allow heat transfer between solid and fluid region. Laser heating was modelled byimposing a volumetric heat source, moving along the welding path. The model wasimplemented in the open source software OpenFOAM and applied to argon shieldinggas and titanium alloy Ti6Al4V base metal. Test cases were done to investigate theshielding gas flow produced by two components: a pipe allowing shielding the melt,and a plate allowing shielding the weld while it cools down. The simulation results confirmedthat these two components do provide an efficient shielding. They also showedthat a significant amount of shielding gas flows towards the observation area of the opticalsystem intended to track the weld path. This is not desired since it could transportsmoke that would disturb the optical signal. The design of the shielding system thusneeds to be modified.

  • 24.
    Josic, Petar
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Järvitalo, Marko
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Framtagning av analysverktyg för materialförbrukning inom motorunderhåll2012Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The thesis report describes the way of creating an analysis tool for material consumption at the department of engine service at Volvo Aero Corporation. The analysis tool generates average lists and purchase lists for PW100 engine. The documentation of the analysis tool is described in seven parts.

    By using the tool the structural material planner can in an easy manner generate lists that are based on earlier historical data. Instead of creating lists manually the material planner can gain more accurate lists much faster. Previously there were no fact based results in comparison with today.

    Pre studies were made to gain a better insight of the current organization and processes at the engine service department. Interviews with staff as well literature studies in the field of storage and spare parts manage has given possibilities to create an analysis tool. Plan of requirements were created to specify the features of the analysis tool.

    The program Microsoft Access was chosen due to the amout of data to construct the analysis tool. All information was brought from the database SAP. The analysis tool was built in three integrated parts:

    1. Average list: shows the average consumption of material for selected engine and maintenance type.

    2. Stock status: checks the stock for material for selected engine and maintenance type. New and used material is selectable.

    3. Incoming material: shows incoming material that is undelivered for selected engine and maintenance type.

    By these three integrated parts the analysis tool generates a purchase list. The list contains engine type, material number, material description, quantity, price and ABC-classification. By implementing the analysis tool in the daily work purchases will be more accurate. Capital binding will decrease as well.

  • 25.
    Jothi, Sathiskumar
    et al.
    Swansea University Bay Campus, College of Engineering, Engineering East Building, Fabian Way, Swansea, United Kingdom.
    Merzlikin, S.V.
    Max-Planck-InstitutfürEisenforschung GmbH, Max-Planck-Strae 1, Düsseldorf, Germany.
    Croft, T.N.
    Swansea University Bay Campus, College of Engineering, Engineering East Building, Fabian Way, Swansea, United Kingdom.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Brown, S.G.R.
    Swansea University Bay Campus, College of Engineering, Engineering East Building, Fabian Way, Swansea, United Kingdom.
    An investigation of micro-mechanisms in hydrogen induced cracking in nickel-based superalloy 7182016In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 664, p. 664-681Article in journal (Refereed)
    Abstract [en]

    Hydrogen embrittlement of the nickel-iron based superalloy 718 has been investigated using slow strain rate tests for pre-charged material and also in-situ hydrogen charging during testing. Fractography analyses have been carried using scanning electron microscopy, electron back-scattering diffraction and orientation image microscopy concentrating on the influence of microstructural features and associated micro-mechanisms leading to hydrogen induced cracking and embrittlement. It was observed that hydrogen induced transgranular cracking initiates at micro-voids in the crystal lattice. Similar behaviour has been observed in multi-scale finite element chemo-mechanical numerical simulations. In contrast, hydrogen induced localized slip intergranular cracking was associated with the formation of micro-voids in intergranular regions. The effects of grain boundary and triple junction character on intergranular hydrogen embrittlement were also investigated. It was observed that low end high angle misorientations (LHAM), 15°<Ξ ≀ 35°, and critical high angle misorientations (CHAM), 35° < 50°, are preferential sites for hydrogen induced cracking. In contrast, few or no hydrogen induced cracks were observed at low angle misorientations (LAM), 0°≀ Ξ le; 15°, high end high angle misorientations (HHAM), 50°<Ξ ≀ 55°, or special GB misorientations (SGB), Ξ > 55°. Finally, the use of grain boundary engineering techniques to increase the resistance of super alloy 718 to hydrogen induced cracking and embrittlement is discussed. © 2016 Elsevier B.V. All rights reserved.

  • 26.
    Keyvani, Ali
    et al.
    University West, Department of Engineering Science, Division of Natural Sciences and Electrical and Surveying Engineering. University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Johansson, Henrik
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Ericsson, Mikael
    University West, Department of Engineering Science, Division of Natural Sciences and Electrical and Surveying Engineering.
    Motion synthesizer platform for moving manikins2012In: 2012 AHFE International Conference 21-25 July 2012 Hilton San Francisco, Union Square, California: Conference proceedings, AHFE , 2012, p. 545-554Conference paper (Refereed)
  • 27.
    Keyvani, Ali
    et al.
    University West, Department of Engineering Science, Division of Natural Sciences and Electrical and Surveying Engineering. University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Johansson, Henrik
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Ericsson, Mikael
    University West, Department of Engineering Science, Division of Natural Sciences and Electrical and Surveying Engineering.
    Lämkull, Dan
    Volvo Car Corporation.
    Örtengren, Roland
    Chalmers.
    Schema for Motion Capture Data Management2011In: Lecture Notes in Computer Science. 3rd International Conference on Digital Human Modeling, ICDHM 2011: Orlando, 9-14 July 2011, 2011, p. 99-108Conference paper (Refereed)
    Abstract [en]

    A unified database platform capable of storing both motion captured data and information about these motions (metadata) is described. The platform stores large motion captured data in order to be used by different applications for searching, comparing, analyzing and updating existing motions. The platform is intended to be used to choose a realistic motion in simulation of production lines. It is capable of supporting and handling different motion formats, various skeleton types and distinctive body regions in a uniform data model. Extended annotating system is also introduced to mark the captured data not only in the time domain (temporal) but also on different body regions (spatial). To utilize the platform, sample tests are performed to prove the functionality. Several motion captured data is uploaded to the database while MATLAB is used to access the data, ergonomically analyze the motions based on OWAS standard, and add the results to the database by automatic tagging of the postures.

  • 28.
    Kovářík, Ondrej
    et al.
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Haušild, Petr
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Medricky, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Tomek, Libor
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Siegl, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Mušálek, Radek
    Institute of Plasma Physics CAS..
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Fatigue crack growth in bodies with thermally sprayed coating2015In: Proceedings from the International Thermal Spray Conference (May 11–14, 2015, Long Beach, California, USA), ASM International, 2015, Vol. 1, p. 398-405Conference paper (Refereed)
    Abstract [en]

    Many applications of thermally sprayed coatings call for increased fatigue resistance of coated parts. Despite the intensive research in this area, the influence of coating on fatigue is still not completely understood. In this paper, the spatiotemporal localization of crack initiation and the dynamics of crack propagation are studied. The resonance bending fatigue test is employed to test flat specimens with both sides coated. Hastelloy-X substrates coated with classical TBC YSZ/NiCoCrAlY composites were tested. The strain distribution on the coating surface is evaluated by the digital image correlation method (DIC) through the whole duration of the fatigue test. Localization of crack initiation sites and the mode of crack propagation in the coated specimen are related to the observed resonance frequency. The individual phases of specimen degradation, i.e. the changes of material properties, crack initiation, and crack propagation are identified. The tested coatings strongly influenced the first two phases, the influence on the crack propagation was less significant. © Copyright (2015) by ASM International All rights reserved.

  • 29.
    Kovářík, Ondrej
    et al.
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Haušild, Petr
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Čapek, Jiří
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Medřický, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Siegl, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Mušálek, Radek
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Pala, Zdeněk
    Institute of Plasma Physics AS CR, v.v.i., Prague, Czech Republic.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Resonance bending fatigue testing with simultaneous damping measurement and its application on layered coatings2016In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 82, Part 2, p. 300-309Article in journal (Refereed)
    Abstract [en]

    Abstract The use of specimen loss factor as fatigue damage indicator of Hastelloy-X substrates with different surface treatments was investigated together with other fatigue damage indicators, namely resonance frequency and crack mouth length. The tested surface treatments included grit-blasting and plasma spraying of NiCoCrAlY bond coat and yttria stabilized zirconia (YSZ) top coat. The loss factors of fatigue test specimens were measured repeatedly during the resonance bending fatigue test using the conventional free decay method. The analysis of the damping spectra, i.e. the model describing the relation of loss factor to maximum macroscopic specimen strain εyy was drafted. The model is based on the combination of defect models developed by Göken and Riehemann (2004) and classical dislocation model of Granato and LÌcke (1956). It appears, that the damping spectra can be well approximated as a combination of two defect peaks (C1 and C2) and one dislocation peak (D1). The low strain defect peak (peak C1) is sensitive to the presence of fatigue cracks. The second defect peak (peak C2) can be attributed to the remaining substrate and coating defects such as embedded grit particles, coating porosity, surface roughness and sliding in the sample clamping area. The fatigue damage detection using the C1 peak magnitude was performed and its results were related to the crack length obtained by digital image correlation (DIC) method. In the crack initiation stage I., the C1 peak height shows different behavior than the resonance frequency and therefore provides new information. The underlying processes causing C1 peak changes need to be found yet, however. In the crack growth stage II., both resonance frequency and peak height C1 correlate with the measured fatigue crack size.

  • 30.
    Kovářík, Ondřej
    et al.
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Haušild, Petr
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Čapek, Jiří
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Medřický, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Siegl, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Mušálek, Radek
    Institute of Plasma Physics AS CR, v.v.i., Prague, Czech Republic.
    Pala, Zdeněk
    Institute of Plasma Physics AS CR, v.v.i., Prague, Czech Republic.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Damping measurement during resonance fatigue test and its application for crack detection in TBC samples2016In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 82, no Part 2, p. 300-309Article in journal (Refereed)
    Abstract [en]

    Abstract The use of specimen loss factor as fatigue damage indicator of Hastelloy-X substrates with different surface treatments was investigated together with other fatigue damage indicators, namely resonance frequency and crack mouth length. The tested surface treatments included grit-blasting and plasma spraying of NiCoCrAlY bond coat and yttria stabilized zirconia (YSZ) top coat. The loss factors of fatigue test specimens were measured repeatedly during the resonance bending fatigue test using the conventional free decay method. The analysis of the damping spectra, i.e. the model describing the relation of loss factor to maximum macroscopic specimen strain εyy was drafted. The model is based on the combination of defect models developed by Göken and Riehemann [1] and classical dislocation model of Granato and LÌcke [2]. It appears, that the damping spectra can be well approximated as a combination of two defect peaks (C1 and C2) and one dislocation peak (D1). The low strain defect peak (peak C1) is sensitive to the presence of fatigue cracks. The second defect peak (peak C2) can be attributed to the remaining substrate and coating defects such as embedded grit particles, coating porosity, surface roughness and sliding in the sample clamping area. The fatigue damage detection using the C1 peak magnitude was performed and its results were related to the crack length obtained by digital image correlation (DIC) method. In the crack initiation stage I., the C1 peak height shows different behavior than the resonance frequency and therefore provides new information. The underlying processes causing C1 peak changes need to be found yet, however. In the crack growth stage II., both resonance frequency and peak height C1 correlate with the measured fatigue crack size.

  • 31.
    Kristiansson, Lilia
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Competence development through Project-based learning in higher education i Sweden and England2012In: 40th annual congress of the Nordic Educational Research association, NPFP/NERA: 8-10 mars, 2012, Copenhagen, Aarhus: Department of Eduation, Aarhus University , 2012, p. 286-Conference paper (Refereed)
    Abstract [en]

    The focus of higher education curricula has been changing from factual knowledge acquisition to developing students competences in response to a changing professional environment in the context of a knowledge economy and labour market globalisation.

    Despite these social changes, existing teaching and learning strategies in Engineering are still mainly lecture-based.

    We investigate competence development using a Project- Based Learning (PrBL) environment on a range of Engineering programmes at Lancaster University, UK and Högskolan Väst, Sweden. We evaluate the PrBL potential to enhance student employability prospects.

    PrBL is an example of collaborative student-focussed learning underpinned by constructivist theory which encourages deeper learning via construction of meaning, connection of ideas and creation of meaningful artefacts. PrBL stimulates collaborative knowledge building among participants and develops a range of skills through creating an informal learning environment. First and second-year students on undergraduate programmes in Engineering departments in both universities with projects as part of their course participated in this study. In the UK the students had to design, build and test two types of robots. The Swedish students were given a project to make calculations for a pump with preset parameters. The projects were designed to help the students acquire competences relevant to their future career. All students worked in small groups. After finishing their projects, the students completed an open-ended questionnaire about their experiences.

    The students evaluated PrBL positively, stating that they developed problem solving and analytical skills and the ability to apply mathematical tools. They highly rated collaboration with peers and emphasised the necessity of developing time management, communication and organisational skills.

    Higher education systems in Europe including Scandinavia are facing new challenges in developing students' employability. We conclude with recommendations for promoting PrBL in university courses as it contributes to competence development and is an efficient tool when administrative resources are limited and when academic staff are faced with large student numbers.

  • 32.
    Kristiansson, Lilia
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Luchinskaya, Daria
    Is co-op education a source of increased motivation for learning?2012In: The European Conference on Educational Research, ECER 2012: 18-21 sept, 2012, Cádiz, 2012Conference paper (Refereed)
    Abstract [en]

    Many universities across the world offer a model for course delivery which combines academic study with a placement in industry. This educational model originated in the U.S., where the automobile industry wanted to ensure a supply of skilled engineers. This educational process has been described in different ways, for example in America it is known as 'cooperative education', or co-op, while in the UK it adopted the name of 'sandwich courses'.

    There is a vast amount of literature which assesses the role of work practice in the development of competences and skills of future professionals, the effect it has on the transition of graduates into the work environment, how it shapes their career aspirations etc. At the same time there are studies which look into the effect of placements on students' motivation in their academic performance.  The research results demonstrate that students who have chosen a co-op model are more motivated in their studies than those students who have chosen not to go on placements [e.g. 1, 2]. The main reasons for the increased motivation of students who chose the co-op route were that their work experience provided them with evidence that the theoretical knowledge they learn at the university is relevant to their work.

    Despite of the benefits that co-op model can bring into students' learning experience, the success of this model across different countries varies. For example, in Sweden the co-op model is very popular among students. However, in the UK the number of students entering this route is decreasing [3].

    In this paper we address the success of the co-op model, especially in relation to students' motivation for their academic study using the co-op programme offered by the Engineering department, University West, Sweden as an example. The aim of this study is to investigate which aspects of academic knowledge students find useful for their practical placements and how their experience of applying this knowledge can be put into practice to increase to motivation for learning of the other students who choose the traditional educational route.

    The main two objectives of educators are: first, to contribute to students' subject knowledge; second, to motivate students to learn. We assume that students coming into higher education have a so-called intrinsic motivation when they begin their studies although it is not always the case in practice. Our task as educators is to stimulate individuals, offer them external motivation to improve their skills and to ensure that they do not lose interest in their selected topics [4].

    To achieve this goal a university teacher can build on positive students' attitudes by creating an open and imaginative atmosphere at lectures and tutorials, for example through the use of alternative teaching methods, such as problem-based learning or project-based learning.

    The study was carried out at the University West in 2010/11. The students who participated in the study opted for the co-op model and the participating tutor taught a module on Solid Mechanics on both co-op and traditional routes.

    MethodFor this study, a mixed-methods approach was used comprising open-ended questionnaires and observations. The students who went on placements were asked to complete a questionnaire at the end of each placement period. The questionnaire was designed to capture the students' experience during their practice focusing on the effect of the placements on their motivation in their further academic study. As part of the existing curriculum the students who went on placements had also to give a presentation to their peers at the end of each placement period where they summarised their work, the responsibilities they had, the engineering problems they were solving, and reflected on their experience. These presentations were observed by the tutor. The data from the questionnaires and presentations were later analysed for students' opinions about the opportunities that they received during their placements for deepening their academic knowledge. Based on the results of this analysis, new engineering problems adapted from the students' practice were introduced into the Solid Mechanics course delivery together with new teaching methods, such as problem-based learning and project-based learning, to achieve higher motivation in students who have not opted for a co-op model [5, 6].

    Expected OutcomesThe collected data showed that the students gave very positive feedback about their practice and the analysis demonstrated that this practical experience supports and inspires further study. In their reports students suggested using new practical-based problems in relevant courses. Using real-life problems can make learning richer and more rewarding for all students.The co-op students can share their work experience with their non-co-op peers by giving presentations regarding the relevance of the academic course content to their job, the problems they were solving while on the placements, the opportunities for challenging future jobs as well as increased confidence and self-esteem. The tutor observed that problem-based learning and project-based learning based on working in groups as well as the use of the real-life problems increased motivation in non-co-op students. They became more responsible, active, and knowledge-seeking and improved their communication with peers. The tutor also observed that having a mix of students who had placements and those who did not in the groups formed a stimulating learning environment. In conclusion, suggestions were made in relation to what can be incorporated into a range of engineering programmes to increase students' motivation and enhance their engagement with the learning process.

    References1. Gomez S., Lush D., and Clements M. (2004), Work Placements Enhance the Academic Performance of Bioscience Undergraduates, J. Voc. Ed. Training, V 56, 3, 363-386. 2. Duignan, J. (2003) Placement and Adding Value to the Academic Performance of Undergraduates:  J. Voc. Ed. Training, Volume 55, 3, 335-350. 3. Sandwich Courses in Higher Education (UK), A report on current provision and analysis of barriers to increasing participation, July 2011, Education for Engineering. 4. Eklann, A, Kjellen, B & Svensson, L.(2010). " Learning using case studies" (in Swedish). Studentlitteratur: Lund. 5. Sergiovanni, T. J. (1991). "The principals a reflective practice perspective" (2nd Ed.). Boston: Allyn and Bacon. 6. Norman G.R., Schmidt H.G. (1992)."The Psychologial Basic of Problem-Based Learning: A Review of the Evidence." Academic Medicine 67: 557-565.

  • 33.
    Lagrosen, Yvonne
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Grundén, Kerstin
    University West, Department of Economics and IT.
    Tosteby, Jonas
    University West, Department of Engineering Science.
    Exploring the OCN method as a means of organizational learning2012In: Exploring the OCN method as a means of organizational learning, 2012Conference paper (Refereed)
    Abstract [en]

    Purpose -. The aim of the paper is to examine whether the use of the OCN-method also leads to organizational learning. The studied organisations are one municipality (Lerum) in west Sweden and one nonprofit professional Swedish organization, the Swedish Association of Body workers.

     

    Methodology/approach - The empirical data are derived from two focus group interviews of selected employees having different functions in the studied organisations and one in-depth interviews. The interviews are analyzed in accordance with grounded theory.  We also examine which strengths and possibilities for improvements the OCN-method has regarding organisational learning.

     

    Findings -  The interview questions are semi-structured and examine the degree and type of learning that is created by using the OCN-method. Using open-ended questions is assumed to be well suited for research in new areas.  The findings from the interviews are related to the five disciplines of the learning organisation.

     

    Research limitation/implication- The empirical data is limited to two different kinds of organisations. It would be of general interest to examine whether the usage of the OCN-method also contributes to learning in organisations.   

     

    Orginality/value - The connection between the OCN -method (Open College Network) and the learning organisation is not very well examined.

     

  • 34.
    Lagrosen, Yvonne
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Lagrosen, Stefan
    University West, Department of Economics and IT, Division of Business Administration.
    The Quality Café as a method for organisational learning and quality development2013In: Abstracts of Papers Presented at the International Conference on Management, Leadership and Governance / [ed] Vincent Ribiere,Lugkana Worasinchai, Bangkok: The Institute for Knowledge and Innovation , 2013, p. 203-208Conference paper (Refereed)
    Abstract [en]

    This paper reports a study into the usefulness of a method called the Quality Café. The method is based on the World Café method which has been supplemented with the quality management tool,

    affinity diagrams. The purpose of this paper is to investigate The Quality Cafe as a method for organisational learning and quality development. The paper is based on theory from quality management and organisational learning. A framework depicting quality man-agement as a system of components of different profundity is presented. In the study the possibility of integrating more profound aspects in one of the superficial tools, the affinity diagram, is assessed. A case study has been carried out in which a Quality Café was performed in a Swedish SPA-hotel. The results have been as-sessed for their usefulness for the company as well as for research. It is found that the method was useful in both regards in this specific case which indicates its us-ability. Nevertheless further research is needed to assess the general usefulness of the method.

  • 35.
    Li, Peigang
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Cold lap formation in Gas Metal Arc Welding of steel: An experimental study of micro-lack of fusion defects2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Cold laps are defined as micro-lack of fusion defects at the weld toe more or less parallel to the surface of the parent plate. These defects are known to negatively influence the fatigue properties of weldments. Previous studies suggest that cold lap formation can not be avoided completely in Gas Metal Arc Welding (GMAW). Therefore, a better understanding of formation mechanisms is imperative to be able to minimize the number and size of these defects. The main objective of this work has been to provide a more comprehensive understanding of cold laps, including categorising, characterisation and defining the most significant factors for formation. GMAW was used to produce welds that were investigated by metallographic methods using light optical microscopy, scanning electron microscopy and energy dispersive spectrometry. A novel classification of cold laps was introduced and three types of cold laps were identified: spatter cold laps, overlap cold laps and spatter-overlap cold laps. It was shown that cold laps are partially or fully filled by oxides. The most common oxides are manganese silicon oxides which were concluded to be formed primarily by oxidation of droplets. The presence of oxides was found to significantly increase the tendency to form spatter cold laps as well as overlap cold laps. Particularly for overlap cold laps, it was found that the depth (in transverse direction of weld) is reduced when welding in a non-oxidising environment. Welding on blasted surfaces increased the cold lap formation by entrapment of gas. The droplet and base metal temperatures were also found to be significant factors in cold lap formation. For overlap cold laps the occurrence frequency decreased with increased preheating temperature of the base metal. Mechanisms of overflowing resulting in overlap cold laps were discussed based on an extensive literature review. Several phenomena are believed to contribute to overflow including Rayleigh instability, the balance of forces, transfer of lateral momentum by droplets and an outward Marangoni fluid flow of the weld pool.

    The present studies suggest that cold lap formation can be suppressed by ensuring that the welding process (arc) is as stable as possible and by welding on a preheated work piece in a non-oxidising environment.

  • 36.
    Li, Peigang
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Influence of oxides on cold lap formation in tandem GMAW2012In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, ISSN 1362-1718, Vol. 17, no 8, p. 643-648Article in journal (Refereed)
    Abstract [en]

    The connection between the formation of cold laps and the presence of Mn‐Si oxides was studied. The underlying purpose is to understand the fundamental mechanisms of cold lap formation and to avoid it. Tandem gas metal arc welding (GMAW) was used to produce welded specimens in two different shielding gases (pure Ar and pure CO2) with base metal S355 MC (EN-10149-2) and wire G3Si1 (EN ISO 14341-A). Cross-sections of welds in the cold lap location were evaluated by light optical microscopy and scanning electron microscopy combined with energy dispersive spectroscopy. The results showed that the Mn‐Si oxides significantly enhanced cold laps formation, especially the overlap type cold lap formation. The Mn‐Si oxides originated from oxidation of the droplets. These oxides transfers to the surface of the weld pool at the weld toe, where they contributed to the formation of the cold laps.

  • 37.
    Li, Peigang
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Study on temperature influence on lack of fusion formation in spatter/base metal interface2014In: Advanced Materials Research, ISSN 1662-8985, Vol. 875 - 877, p. 1421-1428Article in journal (Refereed)
    Abstract [en]

    In the development of modern welded structures with longer life-time and/or higher load-carrying ability, fatigue properties are becoming more and more important. A lot of researches have been done to investigate which factors can elongate the fatigue life of weldments. Cold lap defects, were found to be important initiation sites of the fatigue failure in 1990s. In the ISO standard, cold lap is referred to as a type of micro-lack of fusion. Previous study found that most of the cold laps in GMAW process are formed in spatters. In this paper the interface of spatter/base metal was cut, polished and investigated by conventional metallographic methods. The aim is to reveal the influence of temperature on cold lap formation. In the experiments, different pre-heating temperatures of the parent plate were used in tandem GMAW. Results showed linear empirical relationship between the temperature of the parent plate and the amount of lack of fusion in the spatter/base metal interface.

  • 38.
    Li, Peigang
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Markocsan, Nicolaie
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Karlsson, Leif
    University West, Department of Engineering Science.
    Cold laps - micro-lack of fusion defects in steel arc welds: a reviewManuscript (preprint) (Other academic)
  • 39.
    Li, Peigang
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Klement, Uta
    Chalmers University of Technology, Materials and Manufacturing Technology.
    Characterization of cold lap defects in tandem arc MAG welding2013In: Rivista Italiana della Saldatura, ISSN 0035-6794, Vol. 65, no 5, p. 761-769Article in journal (Refereed)
    Abstract [en]

    The objective of this investigation was to classify and characterize the small lack of fusion defects, called cold lap, located at the weld toe. Since the defects are very small (0.01-1.5 mm) and difficult to detect by NDT methods, a better understanding of the formation mechanism is required to be able to avoid their formation. The investigation consisted of two parts. Firstly, a study was made on the type and frequency of cold laps. Three types were identified, namely "spatter cold lap", and "overlap cold lap" and "spatter-overlap cold lap". No relation between type or frequency of cold laps and the welding parameters could be established. Secondly, the interface between spatter and the base material was investigated using optical and scanning electron microscopy, to better understand the cold lap formation mechanism. Manganese-silicate particles were found in the interface located in such a way that they may assist cold lap formation.

  • 40.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Vassen, Robert
    Forschungszentrum Jülich.
    Erosion Behavior of Gadolinium Zirconate/YSZ Multi-Layered Thermal Barrier Coatings Deposited by Suspension Plasma Spray2016In: Proceedings of the International Thermal Spray Conference, 2016, p. 343-347Conference paper (Refereed)
    Abstract [en]

    Yttria stabilized zirconia (8YSZ) is the standard ceramic material for thermal barrier coating (TBC)applications. However, above 1200º C, it has limitations such as poor sintering resistance & susceptibility to CMAS(Calcium Magnesium Alumino Silicates) degradation. Gadolinium zirconate (GZ) is considered as one of the promising top coat candidates for TBC applications at high temperature (>1200 ºC) due to its lower thermal conductivity, good sintering resistance and CMAS infiltration resistance. Single layer 8YSZ, double layer GZ/YSZand triple layer GZdense/GZ/YSZ TBCs were deposited by suspension plasma spray (SPS). Microstructuralanalysis was carried out by SEM (scanning electron microscopy). Phase analysis of as sprayed TBCs was carriedout using XRD (X ray diffraction). The as sprayed multi-layered TBCs were subjected to erosion test at room temperature and their erosion resistance was compared with single layer 8YSZ. It was observed that the erosion resistance of 8YSZ TBC was higher than GZ/YSZ multi-layered TBCs at room temperature. Among the multilayered TBCs, triple layer TBC was slightly better than double layer in terms of erosion resistance.

  • 41.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Research Environment Production Technology West.
    Thermal conductivity and thermal cyclic fatigue of multilayered Gd2Zr2O7/YSZ thermal barrier coatings processed by suspension plasma spray2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 283, p. 329-336Article in journal (Refereed)
    Abstract [en]

    Rare earth zirconates have lower thermal conductivity, better phase stability, improved sintering resistance and CMAS (calcium magnesium alumino silicates) infiltration resistance than yttria stabilized zirconia (YSZ) at temperatures above 1200 °C. However, their lower fracture toughness and lower coefficient of thermal expansion (CTE) compared to YSZ lead to premature coating failure. In order to overcome these drawbacks at higher temperatures, a multilayered coating approach is attempted in this study and compared with the single layer YSZ. Suspension plasma spray of single layer YSZ, single layer gadolinium zirconate (GZ) and double layer GZ/YSZ was carried out. Additionally, a triple layer coating system, with denser gadolinium zirconate on top of the GZ/YSZ system was sprayed to impart an added functionality of sealing the TBC from CMAS infiltration. Microstructural analysis was done using scanning electron microscopy and optical microscopy. Columnar microstructure with vertical cracks was observed. XRD analysis was used to identify phases formed in the as sprayed TBC samples. Porosity measurements were done using water impregnation method. Thermal diffusivity of single and multi-layered coatings was obtained by laser flash analysis and thermal conductivity of the coating systems was determined. It was found that the thermal conductivity of single layer gadolinium zirconate was lower than YSZ and that the thermal conductivity of multilayered systems were between their respective single layers. The single (YSZ), double (GZ/YSZ) and triple (GZ dense/GZ/YSZ) layer TBCs were subjected to thermal cyclic fatigue (TCF) test at 1100 °C and 1200 °C. It was observed that the single layer YSZ had lowest TCF life whereas the triple layer TBC had highest TCF life irrespective of test temperature.

  • 42.
    Mahade, Satyapal
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Vassen, Robert
    Forschungszentrum Julich, Inst Energy & Climate Res IEK 1, Julich, German.
    Functional performance of Gd2Zr2O7/YSZ multi-layered thermal barrier coatings deposited by suspension plasma spray2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 318, p. 208-216Article in journal (Refereed)
    Abstract [en]

    7-8 wt% yttria stabilized zirconia (YSZ) is the standard ceramic top coat material used in gasturbines to insulate the underlying metallic substrate. However, at higher temperatures(>1200 °C), phase stability and sintering becomes an issue for YSZ. At these temperatures,YSZ is also susceptible to CMAS (calcium magnesium alumino silicates) infiltration. New ceramic materials such as pyrochlores have thus been proposed due to their excellent properties such as lower thermal conductivity and better CMAS attack resistance compared to YSZ. However, pyrochlores have inferior thermo mechanical properties compared to YSZ.Therefore, double-layered TBCs with YSZ as the intermediate layer and pyrochlore as the top ceramic layer have been proposed. In this study, double layer TBC comprising gadoliniumzirconate (GZ)/YSZ and triple layer TBC (GZdense/GZ/YSZ) comprising relatively denser GZtop layer on GZ/YSZ were deposited by suspension plasma spray. Also, single layer 8YSZ TBC was suspension plasma sprayed to compare its functional performance with the multilayered TBCs. Cross sections and top surface morphology of as sprayed TBCs were analyzed by scanning electron microscopy (SEM). XRD analysis was done to identify phases formed in the top surface of as sprayed TBCs. Porosity measurements were made using water intrusionand image analysis methods. Thermal diffusivity of the as sprayed TBCs was measured using laser flash analysis and thermal conductivity of the TBCs was calculated. The multi-layered GZ/YSZ TBCs were shown to have lower thermal conductivity than the single layer YSZ. Theas sprayed TBCs were also subjected to thermal cyclic testing at 1300 ºC. The double and triple layer TBCs had a longer thermal cyclic life compared to YSZ. The failed samples were cold mounted and analyzed by SEM.

  • 43.
    Matsfelt, Johanna
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Study on the influence of the electrode tilt angle in GTAW doing CFD simulation of the heat source2013Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 44.
    Matysiak, Hubert
    et al.
    Warsaw University of Technology, Functional Materials Research Center.
    Zagorska, Malgorzata
    Warsaw University of Technology, Faculty of Materials Science and Engineering.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Balkowiec, Alicja
    Warsaw University of Technology, Faculty of Materials Science and Engineering.
    Cygan, Rafal
    Wytwornia Sprzetu Komunikacyjnego, "Polskie Zaklady Lotnicze Rzeszow".
    Rasinski, Marcin
    Warsaw University of Technology, Faculty of Materials Science and Engineering.
    Pisarek, Marcin
    Polish Academy of Sciences, Institute of Physical Chemistry.
    Andrzejczuk, Mariusz
    Warsaw University of Technology, Faculty of Materials Science and Engineering.
    Kubiak, Krzysztof
    Rzeszow University of Technology, Faculty of Mechanical Engineering and Aeronautics.
    Kurzydlowski, Krzysztof J.
    Warsaw University of Technology, Faculty of Materials Science and Engineering.
    Microstructure of Haynes® 282® Superalloy after Vacuum Induction Melting and Investment Casting of Thin-Walled Components2013In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, ISSN 1996-1944, Vol. 6, no 11, p. 5016-5037Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to characterize the microstructure of the as-cast Haynes® 282® alloy. Observations and analyses were carried out using techniques such as X-ray diffraction (XRD), light microscopy (LM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray spectroscopy (EDS), wave length dispersive X-ray spectroscopy (WDS), auger electron spectroscopy (AES) and electron energy-loss spectrometry (EELS). The phases identified in the as-cast alloy include: γ (gamma matrix), γʹ (matrix strengthening phase), (TiMoCr)C (primary carbide), TiN (primary nitride), σ (sigma-TCP phase), (TiMo)2SC (carbosulphide) and a lamellar constituent consisting of molybdenum and chromium rich secondary carbide phase together with γ phase. Within the dendrites the γʹ appears mostly in the form of spherical, nanometric precipitates (74 nm), while coarser (113 nm) cubic γʹ precipitates are present in the interdendritic areas. Volume fraction content of the γʹ precipitates in the dendrites and interdendritic areas are 9.6% and 8.5%, respectively. Primary nitrides metallic nitrides (MN), are homogeneously dispersed in the as-cast microstructure, while primary carbides metallic carbides (MC), preferentially precipitate in interdendritic areas. Such preference is also observed in the case of globular σ phase. Lamellar constituents characterized as secondary carbides/γ phases were together with (TiMo)2SC phase always observed adjacent to σ phase precipitates. Crystallographic relations were established in-between the MC, σ, secondary carbides and γ/γʹ matrix.

  • 45.
    Medricky, Jan
    et al.
    Czech Technical University in Prague, Prague, Czech Republic.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Pala, Zdenek
    Institute of Plasma Physics AS CR, Prague, Czech Republic.
    Vilemova, Monika
    Institute of Plasma Physics AS CR, Prague, Czech Republic.
    Chraska, Tomas
    Institute of Plasma Physics AS CR, Prague, Czech Republic.
    Johansson, Jimmy
    GKN Aerospace Engine Systems, Trollhättan, Darrasa, Sweden.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Optimization of High Porosity Thermal Barrier Coatings Generated with a Porosity Former2015In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 4, p. 622-628Article in journal (Refereed)
    Abstract [en]

    Yttria-stabilized zirconia thermal barrier coatings are extensively used in turbine industry; however, increasing performance requirements have begun to make conventional air plasma sprayed coatings insufficient for future needs. Since the thermal conductivity of bulk material cannot be lowered easily; the design of highly porous coatings may be the most efficient way to achieve coatings with low thermal conductivity. Thus the approach of fabrication of coatings with a high porosity level based on plasma spraying of ceramic particles of dysprosia-stabilized zirconia mixed with polymer particles, has been tested. Both polymer and ceramic particles melt in plasma and after impact onto a substrate they form a coating. When the coating is subjected to heat treatment, polymer burns out and a complex structure of pores and cracks is formed. In order to obtain desired porosity level and microstructural features in coatings; a design of experiments, based on changes in spray distance, powder feeding rate, and plasma-forming atmosphere, was performed. Acquired coatings were evaluated for thermal conductivity and thermo-cyclic fatigue, and their morphology was assessed using scanning electron microscopy. It was shown that porosity level can be controlled by appropriate changes in spraying parameters.

  • 46.
    Musalek, Radek
    et al.
    Department of Materials Engineering, Institute of Plasma Physics AS CR, v.v.i, Za Slovankou 3, 182 00, Praha 8, Czech Republic.
    Kovarik, Ondrej
    Czech Technical University in Prague, Department of Materials, Faculty of Nuclear Sciences and Physical Engineering, Trojanova 13, 120 00, Praha 2, Czech Republic.
    Medricky, Jan
    Czech Technical University in Prague, Department of Materials, Faculty of Nuclear Sciences and Physical Engineering, Trojanova 13, 120 00, Praha 2, Czech Republic.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Fatigue Performance of TBC on Structural Steel Exposed to Cyclic Bending2014In: Proceedings of the International Thermal Spray Conference, ASM International, 2014, p. 880-885Conference paper (Refereed)
    Abstract [en]

    For applications with variable loading, fatigue performance of coated parts is of utmost importance. In this study, fatigue performance of conventional structural steel coated with thermal barrier coating (TBC) was evaluated in cyclic bending mode by "SF-Test" device. Testing was carried out for as-received and grit-blasted substrates, as well as for samples with Ni-based bond-coat and bond-coat with YSZ-based top-coat. Comparison of results obtained for different loading amplitudes supplemented by fractographic analysis enabled identification of dominating failure mechanisms and evaluation of fatigue resistance alteration due to the deposited coatings.

  • 47.
    Musalek, Radek
    et al.
    Institute of Plasma Physics AS CR, Department of Materials Engineering , v.v.i, Za Slovankou 3, 182 00, Praha 8, Czech Republic.
    Kovarik, Ondrej
    Czech Technical University in Prague, Department of Materials, Faculty of Nuclear Sciences and Physical Engineering, Trojanova 13, 120 00, Praha 2, Czech Republic.
    Medricky, Jan
    Czech Technical University in Prague, Department of Materials, Faculty of Nuclear Sciences and Physical Engineering, Trojanova 13, 120 00, Praha 2, Czech Republic.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Fatigue Testing of TBC on Structural Steel by Cyclic Bending2015In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 1-2, p. 168-174Article in journal (Refereed)
    Abstract [en]

    For applications with variable loading, fatigue performance of coated parts is of utmost importance. In this study, fatigue performance of conventional structural steel coated with thermal barrier coating (TBC) was evaluated in cyclic bending mode by “SF-Test” device. Testing was carried out at each stage of the TBC preparation process, i. e., for as-received and grit-blasted substrates, as well as for samples with Ni-based bond-coat and complete TBC: bond-coat with YSZ-based top-coat. Comparison of results obtained for different loading amplitudes supplemented by fractographic analysis enabled identification of dominating failure mechanisms and demonstrated applicability of the high-frequency resonant bending test for evaluation of fatigue resistance alteration at each stage of the TBC deposition process.

  • 48.
    Musalek, Radek
    et al.
    Institute of Plasma Physics as CR, V.v.i., Prague, Czech Republic.
    Medricky, Jan
    Institute of Plasma Physics as CR, V.v.i., Prague, Czech Republic.
    Pala, Zdenek
    Institute of Plasma Physics as CR, V.v.i., Prague, Czech Republic.
    Kovarik, Ondrej
    Czech Technical University in Prague, Prague, Czech Republic.
    Tomek, Libor
    Czech Technical University in Prague, Prague, Czech Republic.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Fatigue performance of TBCs on hastelioy X substrate during cyclic bending2015In: Thermal Spray 2015: Proceedings from the International Thermal Spray Conference (May 11–14, 2015, Long Beach, California, USA) / [ed] Agarwal A.,Lau Y.-C.,McDonald A.,Bolelli G.,Toma F.-L.,Concustell A.,Widener C.A.,Turunen, ASM International, 2015, Vol. 1, p. 406-412Conference paper (Refereed)
    Abstract [en]

    Our previous experiments with low-cost steel substrates confirmed that individual steps of conventional thermal barrier coating (TBC) deposition may influence fatigue properties of the coated samples differently. In this study, testing was carried out for TBC samples deposited on industrially more relevant Hastelioy X substrates. Samples were tested after each step of TBC deposition process: As-received (non- coated), grit-blasted, bond-coated (NiCoCrAlY) and bond- coated + top-coated (yttria-stabilized zirconia - YSZ). Conventional atmospheric plasma spraying (APS) with gas stabilized plasma torch was used for deposition of both bond coat and top coat. In addition, for one half of the samples, bond coat was prepared by consecutive combination of HVAF (High Velocity Air Fuel) and APS processes. Samples were tested both in as-sprayed condition and after 100 hours annealing at 980 °C, which simulated in-service conditions. Obtained results showed that different fatigue performance may be expected for various stages of the TBC deposition as well as due to the variation of the deposition process and sample temperature history. © Copyright (2015) by ASM International All rights reserved.

  • 49.
    Musalek, Radek
    et al.
    Institute of Plasma Physics AS CR, V.v.i., Za Slovankou 3, 182 00 Praha, Czech Republic .
    Taltavull, Catalina
    Universidad Rey Juan Carlos, ESCET, 28933 Mostoles, Madrid, Spain .
    Lopez Galisteo, Antonio
    Universidad Rey Juan Carlos, ESCET, 28933 Mostoles, Madrid, Spain .
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Evaluation of failure micromechanisms of advanced thermal spray coatings by in-situ experiment2014In: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 606, p. 187-190Article in journal (Refereed)
    Abstract [en]

    Identification of failure mechanisms of thermal spray coatings by means of traditional fractography of failed parts is often troublesome. The reason for this is a highly inhomogeneous character of the coating microstructure and harsh in-service conditions which may obscure evidentiary fractographic marks. In this study, failure evolution of advanced thermal barrier coating (TBC) prepared by plasma spraying was studied in-situ at high magnification in a scanning electron microscope under well-defined laboratory conditions of three-point bending (3PB). © (2014) Trans Tech Publications, Switzerland.

  • 50.
    Mušálek, Radek
    et al.
    Institute of Plasma Physics AS CR, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Prague, Czech Republic.
    Bertolissi, Gabriele
    Institute of Plasma Physics AS CR, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Prague, Czech Republic.
    Medřický, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Materials, .
    Kotlan, Jiří
    Institute of Plasma Physics AS CR, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Prague, Czech Republic.
    Pala, Zdenek
    Institute of Plasma Physics AS CR, v.v.i., Department of Materials Engineering, Za Slovankou 3, 182 00 Prague, Czech Republic.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Feasibility of suspension spraying of yttria-stabilized zirconia with water-stabilized plasma torch2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 268, no April, p. 58-62Article in journal (Refereed)
    Abstract [en]

    Thermal spraying of suspensions allows preparation of coatings from submicron-sized powders but demands a source of heat with a high enthalpy in order to provide an appropriate thermal treatment of the liquid feedstock during the in-flight stage so that the solvent may be evaporated, dispersed particles melted and accelerated towards the substrate to form a coating. Water-stabilized plasma (WSP) torch developed at the Institute of Plasma Physics AS CR, v.v.i. provides such a heat source with high enthalpy, high velocity of the plasma and, when compared to high-enthalpy gas-stabilized plasma (GSP) torches, relatively cheap operation. In this study, results of our experiments with suspension spraying of yttria-stabilized zirconia (YSZ) with WSP torch are presented and demonstrate that coating deposition with a high feed rate is possible with WSP technology. Formation of both columnar “cauliflower” microstructure and segmentation cracks was achieved. Variation of the deposition conditions was observed to modify coating microstructure in terms of splat morphology, porosity and thickness per pass, which is promising for further coating development.

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