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51.	Kovářík, Ondrej, et al. (författare) Resonance bending fatigue testing with simultaneous damping measurement and its application on layered coatings 2016 Ingår i: International Journal of Fatigue. - : Elsevier BV. - 0142-1123 .- 1879-3452. ; 82, Part 2, s. 300-309 Tidskriftsartikel (refereegranskat)abstract 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 Îµyy was drafted. The model is based on the combination of defect models developed by GÃ¶ken and Riehemann (2004) and classical dislocation model of Granato and LÃŒcke (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.
52.	Kuhn, Joel, et al. (författare) The Effect of Fuel Electrode Roughness on the Properties of Plasma Sprayed Solid Oxide Cells 2018 Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 165:9, s. F693-F701 Tidskriftsartikel (refereegranskat)abstract Solid oxide cell electrolytes fabricated by atmospheric plasma spraying are frequently found to have considerable gas leak rates.Electrode surface roughness is known to have an influence on electrolyte leak rates. A jet of high velocity air, produced with an airknife, was aimed at the plasma plume during fuel electrode deposition to reduce the surface roughness prior to electrolyte deposition.The resulting fuel electrode masses, electrode compositions, and electrode surface roughnesses were measured for varying air knifeinlet pressures. Surface asperity populations and maximum heights were significantly reduced using air knife pressures of >6 barat the expense of deposition efficiency. The nickel volume fraction in the fuel electrode increased slightly with increasing air knifepressure. Open circuit voltages were larger on the smoother fuel electrodes that were produced at higher air knife pressures, but nosignificant effect of air knife pressure on cell power density could be discerned.© 2018 The Electrochemical Society
53.	Kuhn, Joel, et al. (författare) The effect of fuel electrode roughness on the properties of plasma sprayed solid oxide cells 2017 Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 78:1, s. 1477-1487 Tidskriftsartikel (refereegranskat)abstract Solid oxide cell electrolytes fabricated by atmospheric plasma spraying are frequently found to have nonzero gas leak rates. Electrode surface roughness is known to have an influence on electrolyte leak rates. A jet of high velocity air, produced with an air knife, was aimed at the plasma plume during fuel electrode deposition to reduce the surface roughness prior to electrolyte deposition. The resulting fuel electrode masses, electrode compositions, and electrode surface roughnesses were measured for varying air knife inlet pressures. Surface asperity populations and maximum heights were significantly reduced using air knife pressures of > 6 bar at the expense of deposition efficiency. The distribution of surface gradients was also improved with the use of the air knife, but some regions with steep gradients still remained in surfaces prepared with an air knife pressure of 8 bar. Â© The Electrochemical Society.
54.	Kumar, Koppolu Raja Rajesh, et al. (författare) The MED7 subunit paralogs of Mediator function redundantly in development of etiolated seedlings in Arabidopsis 2018 Ingår i: The Plant Journal. - : John Wiley & Sons. - 0960-7412 .- 1365-313X. ; 96:3, s. 578-594 Tidskriftsartikel (refereegranskat)abstract MED7 is a subunit of the Mediator middle module and is encoded by two paralogs in Arabidopsis. We generated MED7 silenced lines using RNAi to study its impact on Arabidopsis growth and development. Compared with wild type, etiolated seedlings of the MED7 silenced lines exhibited reduced hypocotyl length caused by reduced cell elongation when grown in the dark. The hypocotyl length phenotype was rescued by exogenously supplied brassinosteroid. In addition, MED7 silenced seedlings exhibited defective hook opening in the dark as well as defective cotyledon expansion in the presence of the brassinosteroid inhibitor brassinazole. Whole transcriptome analysis on etiolated seedlings using RNA sequencing revealed several genes known to be regulated by auxin and brassinosteroids, and a broad range of cell wall-related genes that were differentially expressed in the MED7 silenced lines. This was especially evident for genes involved in cell wall extension and remodeling, such as EXPANSINs and XTHs. Conditional complementation with each MED7 paralog individually restored the hypocotyl phenotype as well as the gene expression defects. Additionally, conditional expression of MED7 had no effects that were independent of the Mediator complex on the observed phenotypes. We concluded that the MED7 paralogs function redundantly in regulating genes required for the normal development of etiolated Arabidopsis seedlings.
55.	Larsson, Miriam, et al. (författare) Functional studies of the yeast Med5, Med15 and Med16 mediator tail subunits 2013 Ingår i: PLOS ONE. - : Public Library of Science (PLOS). - 1932-6203. ; 8:8 Tidskriftsartikel (refereegranskat)abstract The yeast Mediator complex can be divided into three modules, designated Head, Middle and Tail. Tail comprises the Med2, Med3, Med5, Med15 and Med16 protein subunits, which are all encoded by genes that are individually non-essential for viability. In cells lacking Med16, Tail is displaced from Head and Middle. However, inactivation of MED5/MED15 and MED15/MED16 are synthetically lethal, indicating that Tail performs essential functions as a separate complex even when it is not bound to Middle and Head. We have used the N-Degron method to create temperature-sensitive (ts) mutants in the Mediator tail subunits Med5, Med15 and Med16 to study the immediate effects on global gene expression when each subunit is individually inactivated, and when Med5/15 or Med15/16 are inactivated together. We identify 25 genes in each double mutant that show a significant change in expression when compared to the corresponding single mutants and to the wild type strain. Importantly, 13 of the 25 identified genes are common for both double mutants. We also find that all strains in which MED15 is inactivated show down-regulation of genes that have been identified as targets for the Ace2 transcriptional activator protein, which is important for progression through the G1 phase of the cell cycle. Supporting this observation, we demonstrate that loss of Med15 leads to a G1 arrest phenotype. Collectively, these findings provide insight into the function of the Mediator Tail module.
56.	Lundberg, Oskar, et al. (författare) A nonlinear state-dependent model for vibrations excited by roughness in rolling contacts 2015 Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 0022-460X .- 1095-8568. ; 345:9, s. 197-213 Tidskriftsartikel (refereegranskat)abstract A state-dependent method to model contact nonlinearities in rolling contacts is proposed. By pre-calculation of contact stiffness and contact filters as functions of vertical relative displacement, a computationally efficient modelling approach based on a moving point force description is developed. Simulations using the state-dependent model have been analysed by comparison with measurements. Results from the investigated case consisting of a steel ball rolling over a steel beam having two different degrees of roughness - show good agreement between nonlinear simulations and measured beam vibrations. The promising results obtained with the proposed method are potentially applicable to wheel rail interaction and rolling element bearings.
57.	Lundberg, Oskar, 1980-, et al. (författare) Non-linear contact forces for beam/ball-interaction and its influence on the dynamic response of the beam 2013 Ingår i: 42nd International Congress and Exposition on Noise Control Engineering 2013, INTER-NOISE 2013. - : OAL-Osterreichischer Arbeitsring fur Larmbekampfung. - 9781632662675 ; , s. 238-247 Konferensbidrag (refereegranskat)abstract A well-defined rolling contact problem is studied with the intention to cover interesting aspects of tyre-road contact modeling and rolling contact in general. More specifically, the dynamic response in a steel beam caused by a steel ball rolling over it is studied by theoretical modeling of the beam- And ball dynamics as well as the contact forces. Validation of the dynamic response simulations is achieved by comparison with measurements. The contact model is shown to be greatly dependent on an accurate estimate of the real contact stiffness. A method to estimate the contact stiffness which leads to good accuracy in dynamic response simulations is presented. Although the contact stiffness is significantly lower for rubber- Asphalt interaction than for steel-steel contact, the results give useful insight for tyre-road contact modeling.
58.	Lundberg, Oskar, 1980-, et al. (författare) Non-linear contact stiffness and dynamic contact filter for rolling contacts 2014 Ingår i: FISITA 2014 World Automotive Congress - Proceedings. - : FISITA. Konferensbidrag (refereegranskat)abstract Rolling contacts present in passenger cars such as in bearings and transmission elements are sources of noise and vibration, principally for interior comfort concerns. Moreover, tyre/road noise is the main source of road traffic noise which in turn leads to sleep disturbance and annoyance. In order to simulate friction losses as well as generated noise and vibrations in any rolling contact, it is crucial to have a correct description of the dynamic excitation caused by the roughness of the surfaces in contact. In this paper, a state-dependent modelling approach previously proposed by the authors is applied to a well-defined steel-steel rolling contact. A parametric study investigating the influence of rolling speed on contact conditions is performed, indicating the limits for the use of linear point force expressions for the rolling contact investigated. The state-dependent method is based on pre-calculation of contact stiffness and contact filtering as functions of vertical relative displacement. This leads to a computationally efficient way to include the influence of surface roughness and shape of the contacting bodies in a point force expression. Only vertical contact forces are studied within the scope of this work. Tangential friction forces are likely to affect the resulting vibrations and should therefore be further studied.
59.	Lyphout, Christophe, 1981-, et al. (författare) Internal Diameter HVAF Spraying for Wear and Corrosion Applications 2014 Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 24:1-2, s. 235-243 Tidskriftsartikel (refereegranskat)abstract Electrolytic hard chrome (EHC) methods are still widely utilized in the printing, automotive and off-shore industries. Alternative methods to EHC have been widely developed in the past decade by conventional HVOF processes and more recently HVAF systems, which are processing at higher kinetic energy and more particularly at lower temperature, significantly increasing wear and corrosion resistance properties. A dedicated internal diameter HVAF system is here presented, and coatings characteristics are compared to the one obtained by standard HVAF coatings. Specially R&D designed fixtures with inside bore of 200 mm have been manufactured for this purpose, with a possibility to spray samples at increasing depth up to 400 mm while simulating closed bottom bore spraying. WC-based and Cr3C2-based powder feedstock materials have been deposited onto high-strength steel substrates. Respective coating microstructures, thermally induced stresses and corrosion resistance are discussed for further optimization of coating performances. The fact that the ID-HVAF system is utilized both for spraying and gritblasting procedures is also given a particular interest.
60.	Lyphout, Christophe, 1981-, et al. (författare) Screening Design of Supersonic Air Fuel Processing for Hard Metal Coatings 2014 Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 23:8, s. 1323-1332 Tidskriftsartikel (refereegranskat)abstract Replacement of electrolytic hard chromium method by thermal spray technology has shown a growing interest in the past decades, mainly pioneered by depositing WC-based material by conventional HVOF processes. Lower thermal energy and higher kinetic energy of sprayed particles achieved by newly developed Supersonic Air Fuel system, so-called HVAF-M3, significantly reduces decarburization, and increases wear and corrosion resistance properties, making HVAF-sprayed coatings attractive both economically and environmentally. In the present work, full factorial designs of experiments have been extensively utilized to establish relationships between hardware configurations, process and engineering variables, and coatings properties. The relevance of those process factors is emphasized and their significance is discussed in the optimization of coatings for improved abrasion wear and corrosion performances. © 2014 ASM International.
61.	Lyu, Yezhe, et al. (författare) Development of a noise related track maintenance tool 2015 Ingår i: 22nd International Congress on Sound and Vibration, ICSV 2015. - : International Institute of Acoustics and Vibrations. - 9788888942483 Konferensbidrag (refereegranskat)abstract The purpose of this work-package within the Quiet-track, FP7, is to develop a noise related track maintenance tool, in the form of an on-board measurement system. As a first step, lab scale tests using a pin-on-disc tribometer were used in order to distinguish how noise changes when the wear mechanism in a sliding contact shifts from normal wear to severe and catastrophic wear. Once the potential for using sound as an indication of severe wear transitions was established, full scale tests were carried out with a rapid transit (metro) train, type C20. The train was equipped with microphones that continuously measured the sound pressure near the wheel rail contact. In order to provoke severe/catastrophic wear, the test train was run in a curve with small radius, and the rails and wheels were carefully cleaned before the tests. The same kind of transfer from mild to severe/catastrophic wear was identified on the full scale test as in the laboratory scale test, confirmed by studying the surface topography and the morphology of the wear particles. Moreover, the full scale test results showed that the sound pressure changed significantly when transferring from mild to severe wear in agreement with the pin-on-disc test results. By comparing noise from the inner wheel/rail contact to noise form the outer wheel/rail contact a wear indication value for the outer wheel/rail contact is suggested in this study. This value can be seen as an advanced parameter from which the probability of severe wear, in the wheel flange/rail gauge face contact of the outer contact, can be estimated. At present, a real time condition monitoring system is set up in Stockholm (Metro line 1) in order to validate the results.
62.	Mahade, Satyapal, 1987-, et al. (författare) Durability of Gadolinium Zirconate/YSZ Double-Layered Thermal Barrier Coatings under Different Thermal Cyclic Test Conditions 2019 Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 12:14 Tidskriftsartikel (refereegranskat)abstract Higher durability in thermal barrier coatings (TBCs) is constantly sought to enhance the service life of gas turbine engine components such as blades and vanes. In this study, three double layered gadolinium zirconate (GZ)-on-yttria stabilized zirconia (YSZ) TBC variants with varying individual layer thickness but identical total thickness produced by suspension plasma spray (SPS) process were evaluated. The objective was to investigate the role of YSZ layer thickness on the durability of GZ/YSZ double-layered TBCs under different thermal cyclic test conditions i.e., thermal cyclic fatigue (TCF) at 1100 °C and a burner rig test (BRT) at a surface temperature of 1400 °C, respectively. Microstructural characterization was performed using SEM (Scanning Electron Microscopy) and porosity content was measured using image analysis technique. Results reveal that the durability of double-layered TBCs decreased with YSZ thickness under both TCF and BRT test conditions. The TBCs were analyzed by SEM to investigate microstructural evolution as well as failure modes during TCF and BRT test conditions. It was observed that the failure modes varied with test conditions, with all the three double-layered TBC variants showing failure in the TGO (thermally grown oxide) during the TCF test and in the ceramic GZ top coat close to the GZ/YSZ interface during BRT. Furthermore, porosity analysis of the as-sprayed and TCF failed TBCs revealed differences in sintering behavior for GZ and YSZ. The findings from this work provide new insights into the mechanisms responsible for failure of SPS processed double-layered TBCs under different thermal cyclic test conditions.
63.	Mahade, Satyapal, 1987-, et al. (författare) Engineered architectures of gadolinium zirconate based thermal barrier coatings subjected to hot corrosion test 2017 Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 328, s. 361-370 Tidskriftsartikel (refereegranskat)abstract Abstract Gadolinium zirconate (GZ) is considered as a promising top coat candidate for high temperature TBC applications. Suspension plasma spray has shown the capability to generate a wide range of microstructures including the desirable columnar microstructure. In this study, two different TBC architectures were deposited using the axial suspension plasma spray. The first variation was a triple layered TBC comprising of thin YSZ base layer beneath a relatively porous GZ intermediate layer and a dense GZ top layer. The second variation was a composite TBC architecture of GZ and YSZ comprising of thin YSZ base layer and GZ + YSZ top layer. Cross sectional SEM analysis of the layered and composite TBCs revealed a columnar microstructure. The porosity content of the deposited TBCs was measured using two methods (Image Analysis and Water Intrusion). The as-sprayed TBCs were exposed at 900 Â°C for 8 h to a corrosive salt environment consisting of a mixture of vanadium pentoxide and sodium sulfate. XRD analysis on the as-corroded TBCs top surface showed the presence of gadolinium vanadate in both the layered and the composite TBCs. SEM/EDS analysis of the top surface and the cross-section of the layered and composite TBCs after hot corrosion test revealed the infiltration of the molten salts through the columnar gaps. The composite TBC showed a lower hot corrosion induced damage compared to the layered TBC where a considerable spallation was observed.
64.	Mahade, Satyapal, 1987-, et al. (författare) Engineered thermal barrier coatings deposited by suspension plasma spray 2017 Ingår i: Materials letters (General ed.). - : Elsevier BV. - 0167-577X .- 1873-4979. ; 209, s. 517-521 Tidskriftsartikel (refereegranskat)abstract Yttria stabilized zirconia (YSZ) is susceptible to CMAS (Calcium Magnesium Alumino Silicates) attack at high temperatures (>1200 Â°C) which limits its durability. New ceramic materials which can overcome these high temperature challenges are highly desirable. This work investigates the feasibility of depositing two variations of three ceramic layered thermal barrier coatings. The first variation comprised of yttria as the top ceramic layer with gadolinium zirconate (GZ) as the intermediate layer and YSZ as the base layer. The second variation comprised of Yttrium Aluminum Garnet (YAG) as the top layer with gadolinium zirconate as the intermediate layer and YSZ as the base layer. Microstructural analysis of the as sprayed three layered TBCs were performed by SEM/EDS. Columnar microstructures with a relatively dense top layer were obtained in both the variations. The porosity content of the TBCs was measured by water intrusion and image analysis methods. Phase composition of each layer of the as sprayed TBCs was analyzed using XRD. YAG showed an amorphous phase whereas GZ showed a cubic defect fluorite phase and tetragonal phase was observed in YSZ. In the case of yttria, monoclinic and cubic phases were observed. Â© 2017 Elsevier B.V.
65.	Mahade, Satyapal, 1987-, et al. (författare) Erosion Behavior of Gadolinium Zirconate/YSZ Multi-Layered Thermal Barrier Coatings Deposited by Suspension Plasma Spray 2016 Ingår i: Proceedings of the International Thermal Spray Conference. ; , s. 343-347 Konferensbidrag (refereegranskat)abstract 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.
66.	Mahade, Satyapal, et al. (författare) Erosion Performance of Gadolinium Zirconate-Based Thermal Barrier Coatings Processed by Suspension Plasma Spray 2017 Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 26:1-2, s. 108-115 Tidskriftsartikel (refereegranskat)abstract 7-8 wt.% Yttria-stabilized zirconia (YSZ) is the standard thermal barrier coating (TBC) material used by the gas turbines industry due to its excellent thermal and thermo-mechanical properties up to 1200 °C. The need for improvement in gas turbine efficiency has led to an increase in the turbine inlet gas temperature. However, above 1200 °C, YSZ has issues such as poor sintering resistance, poor phase stability and susceptibility to calcium magnesium alumino silicates (CMAS) degradation. Gadolinium zirconate (GZ) is considered as one of the promising top coat candidates for TBC applications at high temperatures (>1200 °C) due to its low thermal conductivity, good sintering resistance and CMAS attack resistance. Single-layer 8YSZ, double-layer GZ/YSZ and triple-layer GZdense/GZ/YSZ TBCs were deposited by suspension plasma spray (SPS) process. Microstructural analysis was carried out by scanning electron microscopy (SEM). A columnar microstructure was observed in the single-, double- and triple-layer TBCs. Phase analysis of the as-sprayed TBCs was carried out using XRD (x-ray diffraction) where a tetragonal prime phase of zirconia in the single-layer YSZ TBC and a cubic defect fluorite phase of GZ in the double and triple-layer TBCs was observed. Porosity measurements of the as-sprayed TBCs were made by water intrusion method and image analysis method. The as-sprayed GZ-based multi-layered TBCs were subjected to erosion test at room temperature, and their erosion resistance was compared with single-layer 8YSZ. It was shown that the erosion resistance of 8YSZ single-layer TBC was higher than GZ-based multi-layered TBCs. Among the multi-layered TBCs, triple-layer TBC was slightly better than double layer in terms of erosion resistance. The eroded TBCs were cold-mounted and analyzed by SEM.
67.	Mahade, Satyapal, 1987-, et al. (författare) Exploiting Suspension Plasma Spraying to Deposit Wear-Resistant Carbide Coatings. 2019 Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 12:15 Tidskriftsartikel (refereegranskat)abstract Titanium- and chromium-based carbides are attractive coating materials to impart wear resistance. Suspension plasma spraying (SPS) is a relatively new thermal spray process which has shown a facile ability to use sub-micron and nano-sized feedstock to deposit high-performance coatings. The specific novelty of this work lies in the processing of fine-sized titanium and chromium carbides (TiC and Cr3C2) in the form of aqueous suspensions to fabricate wear-resistant coatings by SPS. The resulting coatings were characterized by surface morphology, microstructure, phase constitution, and micro-hardness. The abrasive, erosive, and sliding wear performance of the SPS-processed TiC and Cr3C2 coatings was also evaluated. The results amply demonstrate that SPS is a promising route to manufacture superior wear-resistant carbide-based coatings with minimal in situ oxidation during their processing.
68.	Mahade, Satyapal, 1987-, et al. (författare) Failure analysis of Gd2Zr2O7/YSZ multi-layered thermal barrier coatings subjected to thermal cyclic fatigue 2016 Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 689, s. 1011-1019 Tidskriftsartikel (refereegranskat)abstract 8 wt.% yttria stabilized zirconia (8YSZ) is the standard ceramic top coat material used in thermal barrier coatings (TBCs) due to its excellent thermo-physical and thermo-mechanical properties. However, above 1200 °C, YSZ has issues such as susceptibility to CMAS (Calcium Magnesium Alumino Silicates) attack and enhanced sintering which could lead to catastrophic failure of the TBC. Pyrochlores of rare earth zirconate composition such as gadolinium zirconate have shown to be resistant to CMAS attack and at the same time possess several other attractive properties. However, poor thermal cycling life of single layer gadolinium zirconate (GZ) TBC compared to single layer YSZ has been reported. Therefore, a double layered GZ/YSZ TBC with YSZ as the intermediate coating and GZ as the top coat and a single layer 8YSZ were deposited by the axial suspension plasma spray process. Additionally, a triple layer TBC (GZdense/GZ/YSZ) comprising of denser GZ coating on top of GZ/YSZ TBC was deposited. SEM analysis revealed a columnar microstructure in the single, double and triple layer TBCs. XRD analysis confirmed the presence of tetragonal prime and defect fluorite phases in the top surface of YSZ and GZ based as sprayed TBCs respectively. The single layer YSZ and GZ/YSZ multi-layered TBCs were subjected to thermal cyclic fatigue (TCF) testing at 1100 °C and 1200 °C. The triple layer TBC showed a higher thermal cyclic life at both the temperatures compared to the single and double layer TBCs. The failed TBCs at 1100 °C were analyzed by SEM/EDS and image analysis. It was found that the failure modes in single layer YSZ and GZ based TBCs were different.
69.	Mahade, Satyapal, 1987-, et al. (författare) Functional performance of Gd2Zr2O7/YSZ multi-layered thermal barrier coatings deposited by suspension plasma spray 2017 Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 318, s. 208-216 Tidskriftsartikel (refereegranskat)abstract 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.
70.	Mahade, Satyapal, et al. (författare) Isothermal Oxidation Behavior of Gd2Zr2O7/YSZ Multilayered Thermal Barrier Coatings 2016 Ingår i: International Journal of Applied Ceramic Technology. - : Wiley-Blackwell. - 1546-542X .- 1744-7402. ; 13:3, s. 443-450 Tidskriftsartikel (refereegranskat)abstract Efficiency of a gas turbine can be increased by increasing the operating temperature. Yttria-stabilized zirconia (YSZ) is the standard thermal barrier coating (TBC) material used in gas turbine applications. However, above 1200°C, YSZ undergoes significant sintering and CMAS (calcium magnesium alumino silicate) infiltration. New ceramic materials of rare earth zirconate composition such as gadolinium zirconate (GZ) are promising candidates for thermal barrier coating applications (TBC) above 1200°C. Suspension plasma spray of single-layer YSZ, double-layer GZ/YSZ, and a triple-layer TBC comprising denser GZ on top of GZ/YSZ TBC was attempted. The overall coating thickness in all three TBCs was kept the same. Isothermal oxidation performance of the three TBCs along with bare substrate and bond-coated substrate was investigated for time intervals of 10 h, 50 h, and 100 h at 1150°C in air environment. Weight gain/loss analysis was carried out by sensitive weighing balance. Microstructural analysis was carried out using scanning electron microscopy (SEM). As-sprayed single-layer YSZ and double-layer GZ/YSZ showed columnar microstructure, whereas the denser layer in the triple-layer TBC was not columnar. Phase analysis of the top surface of as-sprayed TBCs was carried out using XRD. Porosity measurements were made by water intrusion method. In the weight gain analysis and SEM analysis, multilayered TBCs showed lower weight gain and lower TGO thickness compared to single-layer YSZ.
71.	Mahade, Satyapal, 1987-, et al. (författare) Thermal conductivity and thermal cyclic fatigue of multilayered Gd2Zr2O7/YSZ thermal barrier coatings processed by suspension plasma spray 2015 Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 283, s. 329-336 Tidskriftsartikel (refereegranskat)abstract 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.
72.	Mahade, Satyapal, 1987-, et al. (författare) Understanding the effect of material composition and microstructural design on the erosion behavior of plasma sprayed thermal barrier coatings 2019 Ingår i: Applied Surface Science. - : Elsevier B.V.. - 0169-4332 .- 1873-5584. ; 488, s. 170-184 Tidskriftsartikel (refereegranskat)abstract In this work, three different TBC compositions comprising of yttria partially stabilized zirconia (8YSZ), yttria fully stabilized zirconia (48YSZ) and gadolinium zirconate (GZ) respectively, were processed by suspension plasma spray (SPS) to obtain columnar microstructured TBCs. Additionally, for comparison, lamellar microstructured, 7YSZ TBC was deposited by air plasma spray (APS) process. SEM analysis was carried out to investigate the microstructure and white light interferometry was used to evaluate the surface morphology of the as-sprayed TBCs. Porosity measurements were made using water intrusion and image analysis methods and it was observed that the SPS-YSZ and APS-YSZ TBCs showed higher porosity content than SPS-GZ and SPS-48YSZ. The as-sprayed TBC variations (APS-YSZ, SPS-YSZ, SPS-GZ, and SPS-48YSZ) were subjected to erosion test. Results indicate that the erosion resistance of APS-YSZ TBC was inferior to the SPS-YSZ, SPS-GZ and SPS-48YSZ TBCs respectively. Among the SPS processed TBCs, SPS-YSZ showed the highest erosion resistance whereas the SPS-48YSZ showed the lowest erosion resistance. SEM analysis of the eroded TBCs (cross section and surface morphology) was performed to gain further insights on their erosion behavior. Based on the erosion results and post erosion SEM analysis, erosion mechanisms for splat like microstructured APS TBC and columnar microstructured SPS TBCs were proposed. The findings from this work provide new insights on the erosion mechanisms of columnar microstructured TBCs and lamellar microstructured TBCs deposited by plasma spray.
73.	Markocsan, Nicolaie, et al. (författare) MAX-phase coatings produced by thermal spraying 2016 Ingår i: The 7th International Swedish Production Symposium, SPS16, Conference Proceedings. - Lund : Swedish Production Academy. ; , s. 1-8 Konferensbidrag (refereegranskat)abstract This paper presents a comparative study on Ti2AlC coatings produced by different thermal spray methods, as Ti2AlC is one of the most studied materials from the MAX phase family. Microstructural analysis on coatings produced by High Velocity Air Fuel (HVAF), Cold Spray and High Velocity Oxygen Fuel (HVOF) has been carried out by means of scanning electron microscopy equipped with energy dispersive spectrometer (EDS). The volume fraction of porosity was determined using the ASTM standard E562. The phase characterization of the as-received powder and the as-sprayed coatings was conducted using X-ray diffraction with Cr Kα radiation. Impact of spray parameters on the porosity and the mechanical properties of the coatings are also discussed. The results show that the spraying temperature and velocity plays a crucial role on coatings characteristics.
74.	Markocsan, Nicolaie, 1967-, et al. (författare) MAX-phase coatings produced by thermal spraying 2017 Ingår i: Journal of Superhard Materials. - : Allerton Press. - 1063-4576 .- 1934-9408. ; 39:5, s. 355-364 Tidskriftsartikel (refereegranskat)abstract This paper presents a comparative study on the Ti2AlC coatings produced by different thermal spray methods, as Ti2AlC is one of the most studied materials from the MAX-phase family. Microstructural analysis of coatings produced by High Velocity Air Fuel (HVAF), Cold Spray and High Velocity Oxygen Fuel (HVOF) has been carried out by means of the scanning electron microscopy equipped with an energy dispersive spectrometer (EDS). The volume fraction of porosity was determined using the ASTM standard E562. The phase characterization of the as-received powder and as-sprayed coatings was conducted using the X-ray diffraction with CrKÎ± radiation. Impact of the spray parameters on the porosity and the mechanical properties of the coatings are discussed. The results show that the spraying temperature and velocity play a crucial role in coatings characteristics. Â© 2017, Allerton Press, Inc.
75.	Musalek, Radek, et al. (författare) Fatigue Performance of TBC on Structural Steel Exposed to Cyclic Bending 2014 Ingår i: Proceedings of the International Thermal Spray Conference. - : ASM International. ; , s. 880-885 Konferensbidrag (refereegranskat)abstract 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.
76.	Musalek, Radek, et al. (författare) Fatigue performance of TBCs on hastelioy X substrate during cyclic bending 2015 Ingår i: Thermal Spray 2015. - : ASM International. - 9781510811546 ; , s. 406-412 Konferensbidrag (refereegranskat)abstract 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 Â°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. Â© Copyright (2015) by ASM International All rights reserved.
77.	Musalek, Radek, et al. (författare) Fatigue Performance of TBCs on Hastelloy X Substrate During Cyclic Bending 2016 Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 25:1-2, s. 231-243 Tidskriftsartikel (refereegranskat)abstract 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 the presented study, testing was carried out for TBC samples deposited on industrially more relevant Hastelloy X substrates. Samples were tested after each step of the 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) was used for deposition of bond coat and top coat. In addition, for one half of the samples, dual-layer bond coat was prepared by combination of high-velocity air-fuel (HVAF) and APS processes. Samples were tested in the as-sprayed condition and after 100 hours annealing at 980 Â°C, which simulated application-relevant in-service conditions. Obtained results showed that each stage of the TBC manufacturing process as well as the simulated in-service heat exposure may significantly influence the fatigue properties of the TBC coated part. HVAF grit-blasting substantially increased the fatigue performance of the uncoated substrates. This beneficial effect was suppressed by deposition of APS bond coat but not by deposition of dual-layer HVAF + APS bond coat. All heat-treated samples showed again enhanced fatigue performance. Â© 2015 ASM International
78.	Musalek, Radek, et al. (författare) Fatigue Testing of TBC on Structural Steel by Cyclic Bending 2014 Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 24:1-2, s. 168-174 Tidskriftsartikel (refereegranskat)abstract 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.
79.	Sadeghimeresht, Esmaeil, et al. (författare) Bi-layer thermal spray coatings : A critical approach to extend the service-life of metallic components 2016 Konferensbidrag (övrigt vetenskapligt/konstnärligt)
80.	Sadeghimeresht, Esmaeil, 1985-, et al. (författare) Corrosion performance of bi-layer Ni/Cr2C3–NiCr HVAF thermal spray coating 2016 Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 369, s. 470-481 Forskningsöversikt (refereegranskat)abstract The corrosion behavior of three HVAF thermal spray coating systems (A: single-layer Ni, B: single-layer Cr2C3–NiCr coatings, and C: bi-layer Ni/Cr2C3–NiCr coating) was comparatively studied using immersion,salt spray, and electrochemical tests. Polarization and EIS results showed that the corrosion behavior of Cr2C3–NiCr coatings in 3.5 wt.% NaCl solution was significantly improved by adding the intermediate layer of Ni. It was illustrated that the polarization resistance of the bi-layer Ni/Cr2C3–NiCr and singlelayerCr2C3–NiCr coatings were around 194 and 38 k cm2, respectively. Microstructure analysis revealed that the bond coating successfully prevented the corrosion propagation toward the coating.
81.	Shaikhali, Jehad, et al. (författare) Biochemical and redox characterization of the mediator complex and its associated transcription factor GeBPL, a GLABROUS1 enhancer binding protein 2015 Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 468:3, s. 385-400 Tidskriftsartikel (refereegranskat)abstract The eukaryotic mediator integrates regulatory signals from promoter-bound transcription factors (TFs) and transmits them to RNA polymerase II (Pol II) machinery. Although redox signalling is important in adjusting plant metabolism and development, nothing is known about a possible redox regulation of mediator. In the present study, using pull-down and yeast two-hybrid assays, we demonstrate the association of mediator (MED) subunits MED10a, MED28 and MED32 with the GLABROUS1 (GL1) enhancer-binding protein-like (GeBPL), a plant-specific TF that binds a promoter containing cryptochrome 1 response element 2 (CryR2) element. All the corresponding recombinant proteins form various types of covalent oligomers linked by intermolecular disulfide bonds that are reduced in vitro by the thioredoxin (TRX) and/or glutathione/glutaredoxin (GRX) systems. The presence of recombinant MED10a, MED28 and MED32 subunits or changes of its redox state affect the DNA-binding capacity of GeBPL suggesting that redox-driven conformational changes might modulate its activity. Overall, these results advance our understanding of how redox signalling affects transcription and identify mediator as a novel actor in redox signalling pathways, relaying or integrating redox changes in combinationwith specific TFs as GeBPL.
82.	Shaikhali, Jehad, et al. (författare) Redox regulation of the MED28 and MED32 mediator subunits is important for development and senescence 2016 Ingår i: Protoplasma. - : Springer Science and Business Media LLC. - 0033-183X .- 1615-6102. ; 253:3, s. 957-963 Tidskriftsartikel (refereegranskat)abstract Mediator is a conserved multi-protein complex that acts as a bridge between promoter-bound transcriptional regulators and RNA polymerase II. While redox signaling is important in adjusting plant metabolism and development, the involvement of Mediator in redox homeostasis and regulation only recently started to emerge. Our previous results show that the MED10a, MED28, and MED32 Mediator subunits form various types of covalent oligomers linked by intermolecular disulfide bonds in vitro. To link that with biological significance we have characterized Arabidopsis med32 and med28 mutants and found that they are affected in root development and senescence, phenotypes possibly associated to redox changes.
83.	Silveira, L. L., et al. (författare) Comparative Study of the Corrosion and Cavitation Resistance of HVOF and HVAF FeCrMnSiNi and FeCrMnSiB Coatings 2017 Ingår i: Proceedings of the International Thermal Spray Conference & Exposition (ITSC 2017). - New York : Curran Associates, Inc. - 9781510858220 ; , s. 675-680 Konferensbidrag (refereegranskat)abstract Cavitation and corrosion on hydrodynamic components and systems reduces the operational efficiency. The use of wear resistant coatings have been studied as a solution to the problem of corrosion and cavitation in the industrial environment. Thermal spray processes are recognized as excellent technique to deposit coatings. The high velocity oxy-fuel process (HVOF) can produce high density and bond strength coatings. High velocity air-fuel process (HVAF) is an alternative process, shown to be superior regarding corrosion protection and production costs. HVAF can deposit coating with shorter dwell time and lower temperature, producing coating with lower oxide content This paper presents the use of HVOF and HVAF process to deposit FeCrMnSiNi and FeCrMnSiB coatings, studying the resistance against corrosion and cavitation in comparison to 316L HVOF coating. Microstructure was analyzed by XRD, microscopic means and mechanical testing. Cavitation and corrosion behavior of the coatings were also studied comparatively. HVAF coatings presented lower porosity and oxide levels, as well as higher hardness values, compared with the coatings deposited by HVOF process. The HVAF process presented better cavitation resistance than HVOF coatings. The FeCrMnSiNi HVAF coating had the best corrosion protection performance between the developed alloys.
84.	Silveira, L. L., et al. (författare) Study of the corrosion and cavitation resistance of HVOF and HVAF FeCrMnSiNi and FeCrMnSiB coatings 2019 Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 374, s. 910-922 Tidskriftsartikel (refereegranskat)abstract Cavitation and corrosion on hydrodynamic components and systems reduces the operational efficiency. The use of wear resistant coatings has been studied as a solution to the problem of corrosion and cavitation in industrial environments. The high velocity oxy-fuel process (HVOF) can produce coatings with high density and bond strength. High velocity air-fuel (HVAF) is an alternative process, which can deposit coatings with higher velocity and lower temperatures, compared to the HVOF process, resulting in lower oxide content. This paper analyzes the HVOF and HVAF processes to deposit FeCrMnSiNi and FeCrMnSiB coatings, comparing their cavitation and corrosion resistance. HVAF coatings presented lower porosity and oxide levels, as well as higher hardness values. The HVAF process presented better cavitation and corrosion resistance, due to lower porosity and oxide contents of the coatings. The amount of oxides and pores in the coatings was crucial in their corrosive behavior, by facilitating the penetration of the chloride ions through the pores, leading to a higher corrosion rate and pitting formation. © 2019 Elsevier B.V.
85.	Sjöberg, Sören, 1971- (författare) Influence of running-in on gear efficiency 2014 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract The general trend in gear industry is an increased focus on gear transmission efficiency. This thesis focuses on the understanding of how different gear manufacturing methods – particularly the contribution of the running-in process – affect the surface characteristics and friction response, with the purpose of increasing gearbox efficiency. The thesis consists of a summary and five appended papers.The research hypothesis in paper A and paper B was that the dry elastic contact area ratio is a descriptive parameter for the contact condition. Paper A deals with the influence of manufacturing method on the initial contact conditions. The emphasis in paper B is the changes that occur during running-in and correlating these changes to design requirements. Paper C examines the influence of manganese phosphate coating and lubricants, with respect to friction and the risk of scuffing at the initial contact. Paper D examines the effect of running-in load on the friction response for different surfaces. In paper E, the question of whether the load during running-in influences the gear mesh efficiency is further expounded.The main conclusions of this thesis are that the running-in influences the gear mesh efficiency; a high running-in load enhances the gear mesh efficiency. The difference in mesh efficiency is in the range of one tenth of a per cent. Thus, the influence of running-in cannot be neglected because it is in the same order of magnitude as reported for other gear efficiency enhancements. Furthermore, the dry elastic contact area ratio presents a descriptive measure of how surface topography influences the contact, at both a global (form deviation) and local (roughness) level. The surface topography caused by the manufacturing method has a significant influence on the contact area ratio. Shaving was found to have the highest contact area ratio, and would therefore be the best choice if deviations from case hardening could be minimised. It was also confirmed that surfaces coated with manganese phosphate raise the limiting load for scuffing failure up to 13 times compared to the uncoated ground equivalent.
86.	Sjöberg, Sören, et al. (författare) The influence of manufacturing method on the running-in of gears 2011 Ingår i: Proceedings of the Institution of mechanical engineers. Part J, journal of engineering tribology. - : SAGE Publications. - 1350-6501 .- 2041-305X. ; 225:10, s. 999-1012 Tidskriftsartikel (refereegranskat)abstract Striving for higher gear transmission efficiency by using a low-viscosity transmission lubricant affects the lubricant film thickness. To keep the K-ratio (the ratio between the film thickness and the surface roughness) intact, more effort must be put on the surface topography. This paper presents a study of how running-in affects the dry elastic contact area ratio in spur gears using real surface topographies from three common manufacturing methods (green-shaving, honing, and grinding). The test gears were manufactured in case-hardened steel, similar to 20MnCrS5. Surface topography measurements were used as input to a contact analysis boundary element software program. An important hypothesis used in this work is that the dry elastic contact area ratio, i.e. the ratio between real and nominal contact area, can be used as a measure of the contact conditions in gears. It is concluded that running-in differs significantly for the studied manufacturing methods and that the dry elastic contact area ratio gives a consistent description of these changes. The shaved gears have the highest dry elastic contact area ratio after running in, where the ground gears have the lowest dry elastic contact area ratio. The increase in dry elastic contact area ratio is about 30 per cent for the shaved gears, 12 per cent for the honed gears and less than 5 per cent for the ground gears. Extreme value parameters, such as R(p) and R(z), showed relatively good correlation to dry elastic contact area ratio. However no genuine correlation could be found between dry elastic contact area ratio and two-dimensional (2D) surface roughness parameters. Furthermore, traditional gear metrology form parameters do not serve as a good measure on the changes occurring during the running-in.
87.	Sokolowski, Pawel, et al. (författare) Thermophysical properties of YSZ and YCeSZ suspension plasma sprayed coatings having different microstructures 2017 Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 318, s. 28-38 Tidskriftsartikel (refereegranskat)abstract The paper describes the ceramic top coats of Thermal Barrier Coatings (TBC) obtained by Suspension Plasma Spraying (SPS). The spray process realized with different plasma torches allowed obtaining coatings having different morphology, namely, columnar-like and two-zones microstructure. The microstructures influenced the thermal transport properties of TBC’s. The study analyses the thermophysical properties of yttria and yttria- with ceria- stabilized zirconia coatings, i.e. YSZ and YCeSZ, respectively. The spray processes were realized with the use of three different plasma spray torches: (i) SG-100; (ii) Axial III and (iii) hybrid WSP one. The deposition parameters were designed for each plasma torch separately. The microstructure of coatings was then analyzed using Optical and Scanning Electron Microscopy i.e. OM and SEM, respectively. The thermophysical properties of the coatings such as density, specific heat and thermal dilatation were measured using gas pycnometry, calorimetry and dilatometry methods respectively. The collected data were used, together with thermal diffusivity found with the use of laser flash method, to calculate the thermal conductivity of the deposits. The thermal conductivities of coatings were in a range from 0.63 to 0.99 [W/m.K] for YSZ samples and between 0.82 and 1.37 [W/m.K] in the case of YCeSZ coatings. Thermal transport properties were found to be influenced by the coatings’ porosity and their microstructure. Finally, the thermal conductivity values were successfully validated using response function method, which can be an alternative to complex FEM methods. (C) 2017 Elsevier B.V. All rights reserved.
88.	Sosa, Mario, 1986-, et al. (författare) Gear Web Design with focus on Powder Metal - Sound characteristics and web design : Sound characteristics and web design 2013 Ingår i: International Conference on Gears. - : VDI Verlag. - 9783180921990 ; , s. 1199-1208 Konferensbidrag (refereegranskat)abstract The presented work focuses on gear web design using powder metal (PM) by utilizing the finite element method (FEM) to reduce weight and inertia taking into account root bending strength and tooth deflection.A topological optimization is used to determine feasible candidates for different web designs which have as objective to reduce volume. Similar geometric topologies were shown during different loading conditions; and hence, this topology was chosen as a suitable candidate. This candidate was further developed into a parametric model which incorporated the same overall shape shown in the topological optimization. A shape optimization procedure was used utilizing the parametric model having as state variables root bending strength and tooth deflection; and as objective the decrease in inertia, and in consequence weight, of the gear. To analyze a gear which is thoroughly studied, a similar gear to the FZG C type gear is used.Another aspect studied in this paper is the damping properties of three different gears, wrought, conventional PM and double density. Their damping properties are measured using their reverberation time and their frequency response function.Sound characteristics results show that a significant increase in dampening can be observed in PM gears when compared to conventional wrought gears. Finally results from the shape optimizations show how gears can be designed with PM to reduce weight and inertia, with marginal effects on strength and stiffness.
89.	Sosa, Mario, et al. (författare) In situ running-in analysis of ground gears 2016 Ingår i: Wear. - : Elsevier. - 0043-1648 .- 1873-2577. ; 352-353, s. 122-129 Tidskriftsartikel (refereegranskat)abstract The initial contact state between two interacting gears proves of interest due to empirical evidence indicating difference in life and efficiency in the long term due to the initial operation. Presented here is an analysis of the initial contact state of spur gears, made of case carburized 16MnCr5 steel, by the use of in situ surface measurements and friction measurements in a back-to-back test rig during the running-in cycles. Furthermore a method to estimate wear during running-in is proposed. Results show that the most significant changes in roughness and friction occurred during the first initial cycles at high load.
90.	Sosa, Mario, et al. (författare) In situ surface characterization of running-in of involute gears 2015 Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 340-341, s. 41-46 Tidskriftsartikel (refereegranskat)abstract Gear life and operation are largely determined by the properties of the contacting surfaces, which inevitably change over the gear life. The initial topography transformation, a characteristic effect of running-in, is very important. This paper focuses on how the running-in of the surface topography can be characterized and what methodology can be used for this purpose. To characterize running-in, gears were run in an FZG back-to-back test rig and the changes in surface topography were measured in situ using a Form Talysurf Intra. This enables the same gear tooth surface to be measured with enough precision to follow its development through the different stages of running-in. Gear tooth surfaces as manufactured were measured on three occasions: in initial manufactured condition, after a standard running-in procedure, and after an efficiency test. Running-in was characterized both qualitatively by plotting roughness profiles and quantitatively by analyzing a selected set of roughness parameters. This paper demonstrates that: the asperity peaks were worn off in the initial running-in stage; roughness, waviness, and form can be separated using a carefully chosen polynomial fit and the Gaussian filter; surface topography can be examined initially, after running-in, and after operation in situ; and complete wear of the initial surface can be observed in specific circumstances.
91.	Sosa, Mario, 1986- (författare) Running-in of gears - surface and efficiency transformation 2017 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract With ever shorter development times and market demands on overall system performance such as efficiency, reliability and low maintenance, accurate predictive tools are necessary and gear drives prove to be no exception. All these characteristics have an impact on a process which has remained a riddle: running-in. Even though no consensus on a definition of this phenomena is readily available, this thesis examines efficiency, surface roughness and simulation through the optics of running-in.Geared transmissions are known for their formidable efficiency and their extreme reliability. However, with an ever increasing power density, the ability to accurately predict mesh losses becomes of utmost importance. The accurate quantification of bearing losses as well as efficiency of ground and superfinished gears under dip lubrication are examined with respect to running-in. Results show a considerable influence on the calculation of gear mesh losses originating from which bearing loss model is chosen. Furthermore, when a larger running-in load is used on ground gears, an increase in efficiency can be observed during working operation, while for superfinished no significant changes are found. These efficiency/frictional changes are also shown to occur in the initial cycles of the running-in phase.From a surface transformation point of view running-in is shown to be a reduction of asperity tips in case hardened ground gears, while in superfinished gears no changes were seen. These gear surface changes were measured with a novel method with a surface profilometer in-situ before, after running-in and after efficiency testing. Results also show that such changes in ground gear roughness profile occur during the very initial cycles.In order to predict running-in, a simulation method was developed. Such method utilizes a 2D surface integral method to simulate contact between rough surfaces, but requires the use of surface hardness and an accurate lower cutoff wavelength. This cutoff wavelength proved to play a pivotal role in determining an accurate contact pressure at the proper level of granularity, hence a well defined real contact area. The predicted and measured run-in surfaces are compared and are found to be in accordance with each other.
92.	Struglics, André, et al. (författare) Human aggrecanase generated synovial fluid fragment levels are elevated directly after knee injuries due to proteolysis both in the inter globular and chondroitin sulfate domains. 2011 Ingår i: Osteoarthritis and Cartilage. - : Elsevier BV. - 1063-4584. ; 19, s. 1047-1057 Tidskriftsartikel (refereegranskat)abstract OBJECTIVE: To examine different aggrecanase generated fragments in synovial fluid (SF) from patients with acute and chronic knee injuries and from knee healthy subjects. METHODS: We prepared SF-D1 samples from acute (n=35) and chronic (n=35) knee injury patients and knee healthy subjects (n=10). Aggrecan fragments were analyzed in the SF-D1 samples by quantitative (G1, ARGS, KEEE and G3 antibodies) and non-quantitative (GRGT and AGEG antibodies) Western blot. RESULTS: ARGS-SELE, ARGS-chondroitin sulfate (CS)1, GRGT-, GLGS- and AGEG-G3 fragments were the main ARGS and G3 fragments in injured and reference samples. In the acute injury samples the concentrations of these fragments were increased compared to the reference, and the level of the ARGS-SELE remained elevated for at least 2 years after the joint injury. Both SF ARGS fragments and aggrecanase generated G3 fragments had high sensitivity and specificity as biomarkers in distinguishing injured from healthy knee joints, although the ARGS fragments had higher area under the receiver operating characteristic curve (AUC) values for injuries (74-86%) than the G3 fragments (AUC values 63-68%). CONCLUSION: Our results suggest that during the acute phase after knee injury there is an increased aggrecanase activity against both the interglobular domain (IGD) and the CS2 cleavage sites of joint cartilage aggrecan. This increase in SF aggrecanolytic fragments is present for several years after the injury. SF ARGS fragments are better biomarkers than the aggrecanase generated G3-fragments in distinguishing injured from healthy knee joints.
93.	Wallin, Stefan, et al. (författare) RFC8632: A YANG Data Model for Alarm Management 2019 Annan publikation (populärvet., debatt m.m.)abstract This document defines a YANG module for alarm management. It includes functions for alarm-list management, alarm shelving, and notifications to inform management systems. There are also operations to manage the operator state of an alarm and administrative alarm procedures. The module carefully maps to relevant alarm standards.
94.	Zas, Rafael, et al. (författare) Genetic variation in resistance of Norway spruce seedlings to damage by the pine weevil Hylobius abietis 2017 Ingår i: Tree Genetics & Genomes. - : Springer Berlin/Heidelberg. - 1614-2942 .- 1614-2950. ; 13:5 Tidskriftsartikel (refereegranskat)abstract Regeneration of northern conifer forests is commonly performed by reforestation with genetically improved materials obtained from long-term breeding programs focused on productivity and timber quality. Sanitary threats can, however, compromise the realization of the expected genetic gain. Including pest resistance traits in the breeding programs may contribute to a sustainable protection. Here we quantified the variation in different components of resistance of Norway spruce to its main pest, the pine weevil Hylobius abietis. We followed insect damage in two large progeny trials (52 open-pollinated families with 100-200 individuals per family and trial) naturally infested by the pine weevil. Pine weevils damaged between 17 and 48% of the planted seedlings depending on the trial and year, and mortality due to weevil damage was up to 11.4%. The results indicate significant genetic variation in resistance to the pine weevil, and importantly, the variation was highly consistent across trials irrespective of contrasting incidence levels. Individual heritability estimates for the different components of seedling resistance were consistently low, but family heritabilities were moderate (0.53 to 0.81). While forward selections and breeding for higher resistance seem not feasible, backwards selections of the best parent trees emerge as a putative alternative to reduce weevil damage. A positive genetic correlation between early growth potential and probability of being attacked by the weevil was also observed, but the relationship was weak and appeared only in one of the trials. Overall, results presented here open the door to a new attractive way for reducing damage caused by this harmful pest.

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